Digitalcamera in electronics

(3) Optical resonator or cavity. As mentioned in 2(c) above, Ne atoms in the 3S2 metastable state decay spontaneously to the 2P4 level after a relatively long period of time under normal circumstances; however, a novel circumstance arises if, as shown in Fig. 2, a HeNe discharge is placed between two highly reflecting mirrors that form an optical cavity or resonator along the axis of the discharge. When a resonator structure is in place, photons from the Ne* 3S2-->2P4 transition that are emitted along the axis of the cavity can be reflected hundreds of times between the two highly reflecting end mirrors of the cavity. These reflecting photons can interact with other excited Ne*(3S2) atoms and cause them to emit 6328 Å light in a process known as stimulated emission. The new photon produced in stimulated emission has the same wavelength and polarization, and is emitted in the same direction, as the stimulating photon. It is sometimes useful for purposes of analogy to think of the stimulated emission process as a "cloning" process for photons, as depicted in Fig. 4. The stimulated emission process should be contrasted with spontaneous emission processes that, because they are not caused by any preceding event, produce photons that are emitted isotropically, with random polarization, and over a broader range of wavelengths. As stimulated emission processes occur along the axis of the resonator a situation develops in which essentially all 3S2-->2P4 Ne* decays contribute deexcitation photons to the photon stream reflecting between the two mirrors. This photon multiplication (light amplification) process produces a very large number of photons of the same wavelength and polarization that travel back and forth between the two cavity mirrors. To extract a light beam from the resonator, it is only necessary to have one of the two resonator mirrors, usually called the output coupler, have a reflectivity of only 99% so that 1% of the photons incident on it travel out of the resonator to produce an external laser beam. The other mirror, called the high reflector, should be as reflective as possible. The small diameter, narrow bandwidth, and strong polarization of the HeNe laser beam are determined by the properties of the resonator mirrors and other optical components that lie along the axis of the optical resonator. Back

Area of interest is a digital camera setting, either through software or on board, that allows for a subset of the camera sensor array to be read out for each field. This is useful for reducing the field of view (FOV) or resolution to the lowest required rate in order to decrease the amount of data transferred, thereby increasing the possible frame rate. The full resolution, in terms of Nyquist frequency or spatial sampling frequency, can be retained for this subset of the overall field. For example, a square field of 494 x 494 may contain all of the useful information for a given frame and can be used so as to not waste bandwidth. For additional information on Nyquist frequency, view Imaging Electronics 101: Camera Types and Interfaces for Machine Vision Applications.

Is acameraan electronic device TSA

Gain before the ADC can be useful for taking full advantage of the bit-depth of the camera in low light conditions, although it is almost always the case that careful lighting is more desirable. Gain can also be used to ensure that the taps of multi-tap sensors are well matched. For a detailed discussion of sensor taps, view Imaging Electronics 101: Camera Resolution for Improved Imaging System Performance. In general, gain should be used only after optimizing the exposure setting, and then only after exposure time is set to its maximum for a given frame rate. To visually see the improvement gain can make in an image, compare Figures 1a, 1b, 2a, and 2b.

With binning or subsampling, the entire FOV is desired, but the full camera resolution may not be required. In this case, the gray value of adjacent pixels can be averaged together to form larger effective pixels, or only every other pixel read out. Binning or subsampling increases speed by decreasing the amount of data transferred.

(2) Optical gain medium. To achieve laser action it is necessary to have a large number of atoms in excited states and to establish what is termed a population inversion. To understand the significance of a population inversion to HeNe laser action, it is useful to consider the processes leading to excitation of He and Ne atoms in the discharge, using the simplified diagram of atomic He and Ne energy levels given in Fig. 3. A description of the rather complex HeNe excitation process can be given in terms of the following four steps. (a) An energetic electron collisionally excites a He atom to the state labeled 21S0 in Fig. 3. A He atom in this excited state is often written He*(21S0), where the asterisk means that the He atom is in an excited state. (b) The excited He*(21S0) atom collides with an unexcited Ne atom and the atoms exchange internal energy, with an unexcited He atom and excited Ne atom, written Ne*(3S2), resulting. This energy exchange process occurs with high probability only because of the accidental near equality of the two excitation energies of the two levels in these atoms. (c) The 3S2 level of Ne is an example of a metastable atomic state, meaning that it is only after a relatively long period of time - on atomic time scales - that the Ne*(3S2) atom deexcites to the 2P4 level by emitting a photon of wavelength 6328 Å. It is this emission of 6328 Å light by Ne atoms that, in the presence of a suitable optical configuration, leads to lasing action. (d) The excited Ne*(2P4) atom rapidly deexcites to its ground state by emitting additional photons or by collisions with the plasma tube walls. Because of the extreme quickness of the deexcitation process, at any moment in the HeNe plasma, there are more Ne atoms in the 3S2 state than there are in the 2P4 state, and a population inversion is said to be established between these two levels. When a population inversion is established between the 3S2 and 2P4 levels of the Ne atoms in the discharge, the discharge can act as an optical gain or amplification medium for light of wavelength 6328 Å. This is because a photon incident on the gas discharge will have a greater probability of being replicated in a 3S2-->2P4 stimulated emission process (discussed below) than of being destroyed in the complementary 2P4-->3S2 absorption process. (3) Optical resonator or cavity. As mentioned in 2(c) above, Ne atoms in the 3S2 metastable state decay spontaneously to the 2P4 level after a relatively long period of time under normal circumstances; however, a novel circumstance arises if, as shown in Fig. 2, a HeNe discharge is placed between two highly reflecting mirrors that form an optical cavity or resonator along the axis of the discharge. When a resonator structure is in place, photons from the Ne* 3S2-->2P4 transition that are emitted along the axis of the cavity can be reflected hundreds of times between the two highly reflecting end mirrors of the cavity. These reflecting photons can interact with other excited Ne*(3S2) atoms and cause them to emit 6328 Å light in a process known as stimulated emission. The new photon produced in stimulated emission has the same wavelength and polarization, and is emitted in the same direction, as the stimulating photon. It is sometimes useful for purposes of analogy to think of the stimulated emission process as a "cloning" process for photons, as depicted in Fig. 4. The stimulated emission process should be contrasted with spontaneous emission processes that, because they are not caused by any preceding event, produce photons that are emitted isotropically, with random polarization, and over a broader range of wavelengths. As stimulated emission processes occur along the axis of the resonator a situation develops in which essentially all 3S2-->2P4 Ne* decays contribute deexcitation photons to the photon stream reflecting between the two mirrors. This photon multiplication (light amplification) process produces a very large number of photons of the same wavelength and polarization that travel back and forth between the two cavity mirrors. To extract a light beam from the resonator, it is only necessary to have one of the two resonator mirrors, usually called the output coupler, have a reflectivity of only 99% so that 1% of the photons incident on it travel out of the resonator to produce an external laser beam. The other mirror, called the high reflector, should be as reflective as possible. The small diameter, narrow bandwidth, and strong polarization of the HeNe laser beam are determined by the properties of the resonator mirrors and other optical components that lie along the axis of the optical resonator. Back

(b) The excited He*(21S0) atom collides with an unexcited Ne atom and the atoms exchange internal energy, with an unexcited He atom and excited Ne atom, written Ne*(3S2), resulting. This energy exchange process occurs with high probability only because of the accidental near equality of the two excitation energies of the two levels in these atoms. (c) The 3S2 level of Ne is an example of a metastable atomic state, meaning that it is only after a relatively long period of time - on atomic time scales - that the Ne*(3S2) atom deexcites to the 2P4 level by emitting a photon of wavelength 6328 Å. It is this emission of 6328 Å light by Ne atoms that, in the presence of a suitable optical configuration, leads to lasing action. (d) The excited Ne*(2P4) atom rapidly deexcites to its ground state by emitting additional photons or by collisions with the plasma tube walls. Because of the extreme quickness of the deexcitation process, at any moment in the HeNe plasma, there are more Ne atoms in the 3S2 state than there are in the 2P4 state, and a population inversion is said to be established between these two levels. When a population inversion is established between the 3S2 and 2P4 levels of the Ne atoms in the discharge, the discharge can act as an optical gain or amplification medium for light of wavelength 6328 Å. This is because a photon incident on the gas discharge will have a greater probability of being replicated in a 3S2-->2P4 stimulated emission process (discussed below) than of being destroyed in the complementary 2P4-->3S2 absorption process. (3) Optical resonator or cavity. As mentioned in 2(c) above, Ne atoms in the 3S2 metastable state decay spontaneously to the 2P4 level after a relatively long period of time under normal circumstances; however, a novel circumstance arises if, as shown in Fig. 2, a HeNe discharge is placed between two highly reflecting mirrors that form an optical cavity or resonator along the axis of the discharge. When a resonator structure is in place, photons from the Ne* 3S2-->2P4 transition that are emitted along the axis of the cavity can be reflected hundreds of times between the two highly reflecting end mirrors of the cavity. These reflecting photons can interact with other excited Ne*(3S2) atoms and cause them to emit 6328 Å light in a process known as stimulated emission. The new photon produced in stimulated emission has the same wavelength and polarization, and is emitted in the same direction, as the stimulating photon. It is sometimes useful for purposes of analogy to think of the stimulated emission process as a "cloning" process for photons, as depicted in Fig. 4. The stimulated emission process should be contrasted with spontaneous emission processes that, because they are not caused by any preceding event, produce photons that are emitted isotropically, with random polarization, and over a broader range of wavelengths. As stimulated emission processes occur along the axis of the resonator a situation develops in which essentially all 3S2-->2P4 Ne* decays contribute deexcitation photons to the photon stream reflecting between the two mirrors. This photon multiplication (light amplification) process produces a very large number of photons of the same wavelength and polarization that travel back and forth between the two cavity mirrors. To extract a light beam from the resonator, it is only necessary to have one of the two resonator mirrors, usually called the output coupler, have a reflectivity of only 99% so that 1% of the photons incident on it travel out of the resonator to produce an external laser beam. The other mirror, called the high reflector, should be as reflective as possible. The small diameter, narrow bandwidth, and strong polarization of the HeNe laser beam are determined by the properties of the resonator mirrors and other optical components that lie along the axis of the optical resonator. Back

Camerasensors

In a CCD camera sensor, the pixel clock describes the speed of the complementary signals which are used to move the charge packets through the shift registers towards the read out amplifiers. This determines how long it takes to read out the entire sensor, but it is also limited by noise and spillover issues which occur when the packets are transferred too quickly. For example, two cameras with identical sensors may use different pixel clock rates, leading to different performances in saturation capacity (linear range) and frame rate. This setting is not readily user adjustable, as it is generally set to an optimal value specific to the sensor and FPGA capabilities. Overclocking a sensor by increasing the pixel clock can also lead to thermal issues.

Gamma is a digital camera setting that controls the grayscale reproduced on the image. An image gamma of unity (Figures 3a - 3b) indicates that the camera sensor is precisely reproducing the object grayscale (linear response). A gamma setting much greater than unity results in a silhouetted image in black and white (Figures 4a – 4b). In Figure 4b, notice the decreased contrast compared to Figure 3b. Gamma can be thought of as the ability to stretch one side (either black or white) of the dynamic range of the pixel. This control is often used in signal processing to raise the signal-to-noise ratio (SNR).

Knowledge Center/ Application Notes/ Imaging Application Notes/ Imaging Electronics 101: Basics of Digital Camera Settings for Improved Imaging Results

The process of producing He and Ne in specific excited states is known as pumping and in the HeNe laser this pumping process occurs through electron-atom collisions in a discharge. In other types of lasers, pumping is achieved by light from a bright flashlamp or by chemical reactions. Common to all lasers is the need for some process to prepare an ensemble of atoms, ions or molecules in appropriate excited states so that a desired type of light emission can occur. (2) Optical gain medium. To achieve laser action it is necessary to have a large number of atoms in excited states and to establish what is termed a population inversion. To understand the significance of a population inversion to HeNe laser action, it is useful to consider the processes leading to excitation of He and Ne atoms in the discharge, using the simplified diagram of atomic He and Ne energy levels given in Fig. 3. A description of the rather complex HeNe excitation process can be given in terms of the following four steps. (a) An energetic electron collisionally excites a He atom to the state labeled 21S0 in Fig. 3. A He atom in this excited state is often written He*(21S0), where the asterisk means that the He atom is in an excited state. (b) The excited He*(21S0) atom collides with an unexcited Ne atom and the atoms exchange internal energy, with an unexcited He atom and excited Ne atom, written Ne*(3S2), resulting. This energy exchange process occurs with high probability only because of the accidental near equality of the two excitation energies of the two levels in these atoms. (c) The 3S2 level of Ne is an example of a metastable atomic state, meaning that it is only after a relatively long period of time - on atomic time scales - that the Ne*(3S2) atom deexcites to the 2P4 level by emitting a photon of wavelength 6328 Å. It is this emission of 6328 Å light by Ne atoms that, in the presence of a suitable optical configuration, leads to lasing action. (d) The excited Ne*(2P4) atom rapidly deexcites to its ground state by emitting additional photons or by collisions with the plasma tube walls. Because of the extreme quickness of the deexcitation process, at any moment in the HeNe plasma, there are more Ne atoms in the 3S2 state than there are in the 2P4 state, and a population inversion is said to be established between these two levels. When a population inversion is established between the 3S2 and 2P4 levels of the Ne atoms in the discharge, the discharge can act as an optical gain or amplification medium for light of wavelength 6328 Å. This is because a photon incident on the gas discharge will have a greater probability of being replicated in a 3S2-->2P4 stimulated emission process (discussed below) than of being destroyed in the complementary 2P4-->3S2 absorption process. (3) Optical resonator or cavity. As mentioned in 2(c) above, Ne atoms in the 3S2 metastable state decay spontaneously to the 2P4 level after a relatively long period of time under normal circumstances; however, a novel circumstance arises if, as shown in Fig. 2, a HeNe discharge is placed between two highly reflecting mirrors that form an optical cavity or resonator along the axis of the discharge. When a resonator structure is in place, photons from the Ne* 3S2-->2P4 transition that are emitted along the axis of the cavity can be reflected hundreds of times between the two highly reflecting end mirrors of the cavity. These reflecting photons can interact with other excited Ne*(3S2) atoms and cause them to emit 6328 Å light in a process known as stimulated emission. The new photon produced in stimulated emission has the same wavelength and polarization, and is emitted in the same direction, as the stimulating photon. It is sometimes useful for purposes of analogy to think of the stimulated emission process as a "cloning" process for photons, as depicted in Fig. 4. The stimulated emission process should be contrasted with spontaneous emission processes that, because they are not caused by any preceding event, produce photons that are emitted isotropically, with random polarization, and over a broader range of wavelengths. As stimulated emission processes occur along the axis of the resonator a situation develops in which essentially all 3S2-->2P4 Ne* decays contribute deexcitation photons to the photon stream reflecting between the two mirrors. This photon multiplication (light amplification) process produces a very large number of photons of the same wavelength and polarization that travel back and forth between the two cavity mirrors. To extract a light beam from the resonator, it is only necessary to have one of the two resonator mirrors, usually called the output coupler, have a reflectivity of only 99% so that 1% of the photons incident on it travel out of the resonator to produce an external laser beam. The other mirror, called the high reflector, should be as reflective as possible. The small diameter, narrow bandwidth, and strong polarization of the HeNe laser beam are determined by the properties of the resonator mirrors and other optical components that lie along the axis of the optical resonator. Back

Camerasensor detector

Depending upon the application, it can be useful to expose or activate pixels only when an event of interest occurs. In this case, the user can use the digital camera setting of trigger to make the camera acquire images only when a command is given. This can be used to synchronize image capture with a strobed light source, or take an image when an object passes a certain point or activates a proximity switch, the latter being useful in situations where images are being stored for review at a later time. Trigger can also be used in occasions when a user needs to take a sequence of images in a non-periodic fashion, such as with a constant frame rate.

A 1400 V high voltage, DC power supply maintains a glow discharge or plasma in a glass tube containing an optimal mixture (typically 5:1 to 7:1) of helium and neon gas, as shown in Fig. 1 and indicated in the diagram of Fig. 2. The discharge current is limited to about 5 mA by a 91 kW ballast resistor. Energetic electrons accelerating from the cathode to the anode collide with He and Ne atoms in the laser tube, producing a large number of neutral He and Ne atoms in excited states. He and Ne atoms in excited states can deexcite and return to their ground states by spontaneously emitting light. This light makes up the bright pink-red glow of the plasma that is seen even in the absence of laser action.

(c) The 3S2 level of Ne is an example of a metastable atomic state, meaning that it is only after a relatively long period of time - on atomic time scales - that the Ne*(3S2) atom deexcites to the 2P4 level by emitting a photon of wavelength 6328 Å. It is this emission of 6328 Å light by Ne atoms that, in the presence of a suitable optical configuration, leads to lasing action. (d) The excited Ne*(2P4) atom rapidly deexcites to its ground state by emitting additional photons or by collisions with the plasma tube walls. Because of the extreme quickness of the deexcitation process, at any moment in the HeNe plasma, there are more Ne atoms in the 3S2 state than there are in the 2P4 state, and a population inversion is said to be established between these two levels. When a population inversion is established between the 3S2 and 2P4 levels of the Ne atoms in the discharge, the discharge can act as an optical gain or amplification medium for light of wavelength 6328 Å. This is because a photon incident on the gas discharge will have a greater probability of being replicated in a 3S2-->2P4 stimulated emission process (discussed below) than of being destroyed in the complementary 2P4-->3S2 absorption process. (3) Optical resonator or cavity. As mentioned in 2(c) above, Ne atoms in the 3S2 metastable state decay spontaneously to the 2P4 level after a relatively long period of time under normal circumstances; however, a novel circumstance arises if, as shown in Fig. 2, a HeNe discharge is placed between two highly reflecting mirrors that form an optical cavity or resonator along the axis of the discharge. When a resonator structure is in place, photons from the Ne* 3S2-->2P4 transition that are emitted along the axis of the cavity can be reflected hundreds of times between the two highly reflecting end mirrors of the cavity. These reflecting photons can interact with other excited Ne*(3S2) atoms and cause them to emit 6328 Å light in a process known as stimulated emission. The new photon produced in stimulated emission has the same wavelength and polarization, and is emitted in the same direction, as the stimulating photon. It is sometimes useful for purposes of analogy to think of the stimulated emission process as a "cloning" process for photons, as depicted in Fig. 4. The stimulated emission process should be contrasted with spontaneous emission processes that, because they are not caused by any preceding event, produce photons that are emitted isotropically, with random polarization, and over a broader range of wavelengths. As stimulated emission processes occur along the axis of the resonator a situation develops in which essentially all 3S2-->2P4 Ne* decays contribute deexcitation photons to the photon stream reflecting between the two mirrors. This photon multiplication (light amplification) process produces a very large number of photons of the same wavelength and polarization that travel back and forth between the two cavity mirrors. To extract a light beam from the resonator, it is only necessary to have one of the two resonator mirrors, usually called the output coupler, have a reflectivity of only 99% so that 1% of the photons incident on it travel out of the resonator to produce an external laser beam. The other mirror, called the high reflector, should be as reflective as possible. The small diameter, narrow bandwidth, and strong polarization of the HeNe laser beam are determined by the properties of the resonator mirrors and other optical components that lie along the axis of the optical resonator. Back

Offset refers to the DC component of a video or image signal, and effectively sets the black level of the image. The black level is the pixel level (in electrons, or volts) which corresponds to a pixel value of zero. This is often used with a histogram to ensure the full use of the camera bit-depth, effectively raising signal-to-noise. Pushing non-black pixels to zero lightens the image, although it gives no improvement in the data. By increasing the black level, offset is used as a simple machine vision image processing technique for brightening and effectively creating a threshold (setting all pixels below a certain value to zero to highlight features) for blob detection.

Gain can be before or after the analog-to-digital converter (ADC). However, it is important to note that gain after the ADC is not true gain, but rather digital gain. Digital gain uses a look up table to map the digital values to other values, losing some information in the process.

(a) An energetic electron collisionally excites a He atom to the state labeled 21S0 in Fig. 3. A He atom in this excited state is often written He*(21S0), where the asterisk means that the He atom is in an excited state. (b) The excited He*(21S0) atom collides with an unexcited Ne atom and the atoms exchange internal energy, with an unexcited He atom and excited Ne atom, written Ne*(3S2), resulting. This energy exchange process occurs with high probability only because of the accidental near equality of the two excitation energies of the two levels in these atoms. (c) The 3S2 level of Ne is an example of a metastable atomic state, meaning that it is only after a relatively long period of time - on atomic time scales - that the Ne*(3S2) atom deexcites to the 2P4 level by emitting a photon of wavelength 6328 Å. It is this emission of 6328 Å light by Ne atoms that, in the presence of a suitable optical configuration, leads to lasing action. (d) The excited Ne*(2P4) atom rapidly deexcites to its ground state by emitting additional photons or by collisions with the plasma tube walls. Because of the extreme quickness of the deexcitation process, at any moment in the HeNe plasma, there are more Ne atoms in the 3S2 state than there are in the 2P4 state, and a population inversion is said to be established between these two levels. When a population inversion is established between the 3S2 and 2P4 levels of the Ne atoms in the discharge, the discharge can act as an optical gain or amplification medium for light of wavelength 6328 Å. This is because a photon incident on the gas discharge will have a greater probability of being replicated in a 3S2-->2P4 stimulated emission process (discussed below) than of being destroyed in the complementary 2P4-->3S2 absorption process. (3) Optical resonator or cavity. As mentioned in 2(c) above, Ne atoms in the 3S2 metastable state decay spontaneously to the 2P4 level after a relatively long period of time under normal circumstances; however, a novel circumstance arises if, as shown in Fig. 2, a HeNe discharge is placed between two highly reflecting mirrors that form an optical cavity or resonator along the axis of the discharge. When a resonator structure is in place, photons from the Ne* 3S2-->2P4 transition that are emitted along the axis of the cavity can be reflected hundreds of times between the two highly reflecting end mirrors of the cavity. These reflecting photons can interact with other excited Ne*(3S2) atoms and cause them to emit 6328 Å light in a process known as stimulated emission. The new photon produced in stimulated emission has the same wavelength and polarization, and is emitted in the same direction, as the stimulating photon. It is sometimes useful for purposes of analogy to think of the stimulated emission process as a "cloning" process for photons, as depicted in Fig. 4. The stimulated emission process should be contrasted with spontaneous emission processes that, because they are not caused by any preceding event, produce photons that are emitted isotropically, with random polarization, and over a broader range of wavelengths. As stimulated emission processes occur along the axis of the resonator a situation develops in which essentially all 3S2-->2P4 Ne* decays contribute deexcitation photons to the photon stream reflecting between the two mirrors. This photon multiplication (light amplification) process produces a very large number of photons of the same wavelength and polarization that travel back and forth between the two cavity mirrors. To extract a light beam from the resonator, it is only necessary to have one of the two resonator mirrors, usually called the output coupler, have a reflectivity of only 99% so that 1% of the photons incident on it travel out of the resonator to produce an external laser beam. The other mirror, called the high reflector, should be as reflective as possible. The small diameter, narrow bandwidth, and strong polarization of the HeNe laser beam are determined by the properties of the resonator mirrors and other optical components that lie along the axis of the optical resonator. Back

Binning is specific to CCD sensors, where the charge from adjacent pixels are physically added together, increasing the effective exposure and sensitivity. Subsampling generally refers to CMOS sensors, where binning is not strictly possible; subsampling offers no increase in exposure or sensitivity. Subsampling can also be used with CCD sensors in lieu of binning when low resolution and high transfer rates are desired without the desire for the original exposure. For in-depth information on sensors, view Imaging Electronics 101: Understanding Camera Sensors for Machine Vision Applications.

Types ofcamera

Camera in electronicsprice

(1) Energy pump. A 1400 V high voltage, DC power supply maintains a glow discharge or plasma in a glass tube containing an optimal mixture (typically 5:1 to 7:1) of helium and neon gas, as shown in Fig. 1 and indicated in the diagram of Fig. 2. The discharge current is limited to about 5 mA by a 91 kW ballast resistor. Energetic electrons accelerating from the cathode to the anode collide with He and Ne atoms in the laser tube, producing a large number of neutral He and Ne atoms in excited states. He and Ne atoms in excited states can deexcite and return to their ground states by spontaneously emitting light. This light makes up the bright pink-red glow of the plasma that is seen even in the absence of laser action. The process of producing He and Ne in specific excited states is known as pumping and in the HeNe laser this pumping process occurs through electron-atom collisions in a discharge. In other types of lasers, pumping is achieved by light from a bright flashlamp or by chemical reactions. Common to all lasers is the need for some process to prepare an ensemble of atoms, ions or molecules in appropriate excited states so that a desired type of light emission can occur. (2) Optical gain medium. To achieve laser action it is necessary to have a large number of atoms in excited states and to establish what is termed a population inversion. To understand the significance of a population inversion to HeNe laser action, it is useful to consider the processes leading to excitation of He and Ne atoms in the discharge, using the simplified diagram of atomic He and Ne energy levels given in Fig. 3. A description of the rather complex HeNe excitation process can be given in terms of the following four steps. (a) An energetic electron collisionally excites a He atom to the state labeled 21S0 in Fig. 3. A He atom in this excited state is often written He*(21S0), where the asterisk means that the He atom is in an excited state. (b) The excited He*(21S0) atom collides with an unexcited Ne atom and the atoms exchange internal energy, with an unexcited He atom and excited Ne atom, written Ne*(3S2), resulting. This energy exchange process occurs with high probability only because of the accidental near equality of the two excitation energies of the two levels in these atoms. (c) The 3S2 level of Ne is an example of a metastable atomic state, meaning that it is only after a relatively long period of time - on atomic time scales - that the Ne*(3S2) atom deexcites to the 2P4 level by emitting a photon of wavelength 6328 Å. It is this emission of 6328 Å light by Ne atoms that, in the presence of a suitable optical configuration, leads to lasing action. (d) The excited Ne*(2P4) atom rapidly deexcites to its ground state by emitting additional photons or by collisions with the plasma tube walls. Because of the extreme quickness of the deexcitation process, at any moment in the HeNe plasma, there are more Ne atoms in the 3S2 state than there are in the 2P4 state, and a population inversion is said to be established between these two levels. When a population inversion is established between the 3S2 and 2P4 levels of the Ne atoms in the discharge, the discharge can act as an optical gain or amplification medium for light of wavelength 6328 Å. This is because a photon incident on the gas discharge will have a greater probability of being replicated in a 3S2-->2P4 stimulated emission process (discussed below) than of being destroyed in the complementary 2P4-->3S2 absorption process. (3) Optical resonator or cavity. As mentioned in 2(c) above, Ne atoms in the 3S2 metastable state decay spontaneously to the 2P4 level after a relatively long period of time under normal circumstances; however, a novel circumstance arises if, as shown in Fig. 2, a HeNe discharge is placed between two highly reflecting mirrors that form an optical cavity or resonator along the axis of the discharge. When a resonator structure is in place, photons from the Ne* 3S2-->2P4 transition that are emitted along the axis of the cavity can be reflected hundreds of times between the two highly reflecting end mirrors of the cavity. These reflecting photons can interact with other excited Ne*(3S2) atoms and cause them to emit 6328 Å light in a process known as stimulated emission. The new photon produced in stimulated emission has the same wavelength and polarization, and is emitted in the same direction, as the stimulating photon. It is sometimes useful for purposes of analogy to think of the stimulated emission process as a "cloning" process for photons, as depicted in Fig. 4. The stimulated emission process should be contrasted with spontaneous emission processes that, because they are not caused by any preceding event, produce photons that are emitted isotropically, with random polarization, and over a broader range of wavelengths. As stimulated emission processes occur along the axis of the resonator a situation develops in which essentially all 3S2-->2P4 Ne* decays contribute deexcitation photons to the photon stream reflecting between the two mirrors. This photon multiplication (light amplification) process produces a very large number of photons of the same wavelength and polarization that travel back and forth between the two cavity mirrors. To extract a light beam from the resonator, it is only necessary to have one of the two resonator mirrors, usually called the output coupler, have a reflectivity of only 99% so that 1% of the photons incident on it travel out of the resonator to produce an external laser beam. The other mirror, called the high reflector, should be as reflective as possible. The small diameter, narrow bandwidth, and strong polarization of the HeNe laser beam are determined by the properties of the resonator mirrors and other optical components that lie along the axis of the optical resonator. Back

There are three principal elements of a laser, which are (1) an energy pump, (2) an optical gain medium, and (3) an optical resonator. These three elements are described in detail below for the case of the HeNe laser .

There are three principal elements of a laser, which are (1) an energy pump, (2) an optical gain medium, and (3) an optical resonator. These three elements are described in detail below for the case of the HeNe laser . (1) Energy pump. A 1400 V high voltage, DC power supply maintains a glow discharge or plasma in a glass tube containing an optimal mixture (typically 5:1 to 7:1) of helium and neon gas, as shown in Fig. 1 and indicated in the diagram of Fig. 2. The discharge current is limited to about 5 mA by a 91 kW ballast resistor. Energetic electrons accelerating from the cathode to the anode collide with He and Ne atoms in the laser tube, producing a large number of neutral He and Ne atoms in excited states. He and Ne atoms in excited states can deexcite and return to their ground states by spontaneously emitting light. This light makes up the bright pink-red glow of the plasma that is seen even in the absence of laser action. The process of producing He and Ne in specific excited states is known as pumping and in the HeNe laser this pumping process occurs through electron-atom collisions in a discharge. In other types of lasers, pumping is achieved by light from a bright flashlamp or by chemical reactions. Common to all lasers is the need for some process to prepare an ensemble of atoms, ions or molecules in appropriate excited states so that a desired type of light emission can occur. (2) Optical gain medium. To achieve laser action it is necessary to have a large number of atoms in excited states and to establish what is termed a population inversion. To understand the significance of a population inversion to HeNe laser action, it is useful to consider the processes leading to excitation of He and Ne atoms in the discharge, using the simplified diagram of atomic He and Ne energy levels given in Fig. 3. A description of the rather complex HeNe excitation process can be given in terms of the following four steps. (a) An energetic electron collisionally excites a He atom to the state labeled 21S0 in Fig. 3. A He atom in this excited state is often written He*(21S0), where the asterisk means that the He atom is in an excited state. (b) The excited He*(21S0) atom collides with an unexcited Ne atom and the atoms exchange internal energy, with an unexcited He atom and excited Ne atom, written Ne*(3S2), resulting. This energy exchange process occurs with high probability only because of the accidental near equality of the two excitation energies of the two levels in these atoms. (c) The 3S2 level of Ne is an example of a metastable atomic state, meaning that it is only after a relatively long period of time - on atomic time scales - that the Ne*(3S2) atom deexcites to the 2P4 level by emitting a photon of wavelength 6328 Å. It is this emission of 6328 Å light by Ne atoms that, in the presence of a suitable optical configuration, leads to lasing action. (d) The excited Ne*(2P4) atom rapidly deexcites to its ground state by emitting additional photons or by collisions with the plasma tube walls. Because of the extreme quickness of the deexcitation process, at any moment in the HeNe plasma, there are more Ne atoms in the 3S2 state than there are in the 2P4 state, and a population inversion is said to be established between these two levels. When a population inversion is established between the 3S2 and 2P4 levels of the Ne atoms in the discharge, the discharge can act as an optical gain or amplification medium for light of wavelength 6328 Å. This is because a photon incident on the gas discharge will have a greater probability of being replicated in a 3S2-->2P4 stimulated emission process (discussed below) than of being destroyed in the complementary 2P4-->3S2 absorption process. (3) Optical resonator or cavity. As mentioned in 2(c) above, Ne atoms in the 3S2 metastable state decay spontaneously to the 2P4 level after a relatively long period of time under normal circumstances; however, a novel circumstance arises if, as shown in Fig. 2, a HeNe discharge is placed between two highly reflecting mirrors that form an optical cavity or resonator along the axis of the discharge. When a resonator structure is in place, photons from the Ne* 3S2-->2P4 transition that are emitted along the axis of the cavity can be reflected hundreds of times between the two highly reflecting end mirrors of the cavity. These reflecting photons can interact with other excited Ne*(3S2) atoms and cause them to emit 6328 Å light in a process known as stimulated emission. The new photon produced in stimulated emission has the same wavelength and polarization, and is emitted in the same direction, as the stimulating photon. It is sometimes useful for purposes of analogy to think of the stimulated emission process as a "cloning" process for photons, as depicted in Fig. 4. The stimulated emission process should be contrasted with spontaneous emission processes that, because they are not caused by any preceding event, produce photons that are emitted isotropically, with random polarization, and over a broader range of wavelengths. As stimulated emission processes occur along the axis of the resonator a situation develops in which essentially all 3S2-->2P4 Ne* decays contribute deexcitation photons to the photon stream reflecting between the two mirrors. This photon multiplication (light amplification) process produces a very large number of photons of the same wavelength and polarization that travel back and forth between the two cavity mirrors. To extract a light beam from the resonator, it is only necessary to have one of the two resonator mirrors, usually called the output coupler, have a reflectivity of only 99% so that 1% of the photons incident on it travel out of the resonator to produce an external laser beam. The other mirror, called the high reflector, should be as reflective as possible. The small diameter, narrow bandwidth, and strong polarization of the HeNe laser beam are determined by the properties of the resonator mirrors and other optical components that lie along the axis of the optical resonator. Back

When a population inversion is established between the 3S2 and 2P4 levels of the Ne atoms in the discharge, the discharge can act as an optical gain or amplification medium for light of wavelength 6328 Å. This is because a photon incident on the gas discharge will have a greater probability of being replicated in a 3S2-->2P4 stimulated emission process (discussed below) than of being destroyed in the complementary 2P4-->3S2 absorption process. (3) Optical resonator or cavity. As mentioned in 2(c) above, Ne atoms in the 3S2 metastable state decay spontaneously to the 2P4 level after a relatively long period of time under normal circumstances; however, a novel circumstance arises if, as shown in Fig. 2, a HeNe discharge is placed between two highly reflecting mirrors that form an optical cavity or resonator along the axis of the discharge. When a resonator structure is in place, photons from the Ne* 3S2-->2P4 transition that are emitted along the axis of the cavity can be reflected hundreds of times between the two highly reflecting end mirrors of the cavity. These reflecting photons can interact with other excited Ne*(3S2) atoms and cause them to emit 6328 Å light in a process known as stimulated emission. The new photon produced in stimulated emission has the same wavelength and polarization, and is emitted in the same direction, as the stimulating photon. It is sometimes useful for purposes of analogy to think of the stimulated emission process as a "cloning" process for photons, as depicted in Fig. 4. The stimulated emission process should be contrasted with spontaneous emission processes that, because they are not caused by any preceding event, produce photons that are emitted isotropically, with random polarization, and over a broader range of wavelengths. As stimulated emission processes occur along the axis of the resonator a situation develops in which essentially all 3S2-->2P4 Ne* decays contribute deexcitation photons to the photon stream reflecting between the two mirrors. This photon multiplication (light amplification) process produces a very large number of photons of the same wavelength and polarization that travel back and forth between the two cavity mirrors. To extract a light beam from the resonator, it is only necessary to have one of the two resonator mirrors, usually called the output coupler, have a reflectivity of only 99% so that 1% of the photons incident on it travel out of the resonator to produce an external laser beam. The other mirror, called the high reflector, should be as reflective as possible. The small diameter, narrow bandwidth, and strong polarization of the HeNe laser beam are determined by the properties of the resonator mirrors and other optical components that lie along the axis of the optical resonator. Back

Digital cameras, compared to their analog counterparts, offer greater flexibility in allowing the user to adjust camera settings through acquisition software. In some cases, the settings in analog cameras can be adjusted through hardware such as dual in-line package (DIP) switches or RS-232 connections. Nevertheless, the flexibility of modifying settings through the software greatly adds to increased image quality, speed, and contrast - factors that could mean the difference between observing a defect and missing it altogether. Many digital cameras have on board field-programmable gate arrays (FPGAs) for digital signal processing and camera functions. FPGAs perform the calculations behind many digital camera functions, as well as additional ones such as color interpolation for mosaic filters and simple image processing (in the case of smart cameras). Camera firmware encompasses the FPGA and on board memory; firmware updates are occasionally available for cameras, adding and improving features. The on board memory in digital cameras allows for storage of settings, look up tables, buffering for high transfer rates, and multi-camera networking with ethernet switches. Some of the most common digital camera settings are gain, gamma, area of interest, binning/subsampling, pixel clock, offset, and triggering. Understanding these basic settings will help to achieve the best results for a range of applications.

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Triggering can be done through hardware or software. Hardware triggers are ideal for high precision applications, where the latency intrinsic to a software trigger is unacceptable (which can be many milliseconds). Software triggers are often easier to implement because they take the form of a computer command sent through the normal communication path. An example of a software trigger is the snap function in image viewing software.

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As stimulated emission processes occur along the axis of the resonator a situation develops in which essentially all 3S2-->2P4 Ne* decays contribute deexcitation photons to the photon stream reflecting between the two mirrors. This photon multiplication (light amplification) process produces a very large number of photons of the same wavelength and polarization that travel back and forth between the two cavity mirrors. To extract a light beam from the resonator, it is only necessary to have one of the two resonator mirrors, usually called the output coupler, have a reflectivity of only 99% so that 1% of the photons incident on it travel out of the resonator to produce an external laser beam. The other mirror, called the high reflector, should be as reflective as possible. The small diameter, narrow bandwidth, and strong polarization of the HeNe laser beam are determined by the properties of the resonator mirrors and other optical components that lie along the axis of the optical resonator. Back

Though a host of additional digital camera settings exist, it is important to understand the basics of gain, gamma, area of interest, binning/subsampling, pixel clock, offset, and trigger. These functions lay the groundwork for advanced image processing techniques that require knowledge of the aforementioned basic settings. To learn more about imaging electronics, view our additional imaging electronics 101 series pertaining to camera sensors, camera resolution, and camera types.

As mentioned in 2(c) above, Ne atoms in the 3S2 metastable state decay spontaneously to the 2P4 level after a relatively long period of time under normal circumstances; however, a novel circumstance arises if, as shown in Fig. 2, a HeNe discharge is placed between two highly reflecting mirrors that form an optical cavity or resonator along the axis of the discharge. When a resonator structure is in place, photons from the Ne* 3S2-->2P4 transition that are emitted along the axis of the cavity can be reflected hundreds of times between the two highly reflecting end mirrors of the cavity. These reflecting photons can interact with other excited Ne*(3S2) atoms and cause them to emit 6328 Å light in a process known as stimulated emission. The new photon produced in stimulated emission has the same wavelength and polarization, and is emitted in the same direction, as the stimulating photon. It is sometimes useful for purposes of analogy to think of the stimulated emission process as a "cloning" process for photons, as depicted in Fig. 4. The stimulated emission process should be contrasted with spontaneous emission processes that, because they are not caused by any preceding event, produce photons that are emitted isotropically, with random polarization, and over a broader range of wavelengths. As stimulated emission processes occur along the axis of the resonator a situation develops in which essentially all 3S2-->2P4 Ne* decays contribute deexcitation photons to the photon stream reflecting between the two mirrors. This photon multiplication (light amplification) process produces a very large number of photons of the same wavelength and polarization that travel back and forth between the two cavity mirrors. To extract a light beam from the resonator, it is only necessary to have one of the two resonator mirrors, usually called the output coupler, have a reflectivity of only 99% so that 1% of the photons incident on it travel out of the resonator to produce an external laser beam. The other mirror, called the high reflector, should be as reflective as possible. The small diameter, narrow bandwidth, and strong polarization of the HeNe laser beam are determined by the properties of the resonator mirrors and other optical components that lie along the axis of the optical resonator. Back

Gain is a digital camera setting that controls the amplification of the signal from the camera sensor. It should be noted that this amplifies the whole signal, including any associated background noise. Most cameras have automatic gain, or autogain, which is abbreviated as AGC. Some allow the user to turn it off or set it manually.

(d) The excited Ne*(2P4) atom rapidly deexcites to its ground state by emitting additional photons or by collisions with the plasma tube walls. Because of the extreme quickness of the deexcitation process, at any moment in the HeNe plasma, there are more Ne atoms in the 3S2 state than there are in the 2P4 state, and a population inversion is said to be established between these two levels. When a population inversion is established between the 3S2 and 2P4 levels of the Ne atoms in the discharge, the discharge can act as an optical gain or amplification medium for light of wavelength 6328 Å. This is because a photon incident on the gas discharge will have a greater probability of being replicated in a 3S2-->2P4 stimulated emission process (discussed below) than of being destroyed in the complementary 2P4-->3S2 absorption process. (3) Optical resonator or cavity. As mentioned in 2(c) above, Ne atoms in the 3S2 metastable state decay spontaneously to the 2P4 level after a relatively long period of time under normal circumstances; however, a novel circumstance arises if, as shown in Fig. 2, a HeNe discharge is placed between two highly reflecting mirrors that form an optical cavity or resonator along the axis of the discharge. When a resonator structure is in place, photons from the Ne* 3S2-->2P4 transition that are emitted along the axis of the cavity can be reflected hundreds of times between the two highly reflecting end mirrors of the cavity. These reflecting photons can interact with other excited Ne*(3S2) atoms and cause them to emit 6328 Å light in a process known as stimulated emission. The new photon produced in stimulated emission has the same wavelength and polarization, and is emitted in the same direction, as the stimulating photon. It is sometimes useful for purposes of analogy to think of the stimulated emission process as a "cloning" process for photons, as depicted in Fig. 4. The stimulated emission process should be contrasted with spontaneous emission processes that, because they are not caused by any preceding event, produce photons that are emitted isotropically, with random polarization, and over a broader range of wavelengths. As stimulated emission processes occur along the axis of the resonator a situation develops in which essentially all 3S2-->2P4 Ne* decays contribute deexcitation photons to the photon stream reflecting between the two mirrors. This photon multiplication (light amplification) process produces a very large number of photons of the same wavelength and polarization that travel back and forth between the two cavity mirrors. To extract a light beam from the resonator, it is only necessary to have one of the two resonator mirrors, usually called the output coupler, have a reflectivity of only 99% so that 1% of the photons incident on it travel out of the resonator to produce an external laser beam. The other mirror, called the high reflector, should be as reflective as possible. The small diameter, narrow bandwidth, and strong polarization of the HeNe laser beam are determined by the properties of the resonator mirrors and other optical components that lie along the axis of the optical resonator. Back

To achieve laser action it is necessary to have a large number of atoms in excited states and to establish what is termed a population inversion. To understand the significance of a population inversion to HeNe laser action, it is useful to consider the processes leading to excitation of He and Ne atoms in the discharge, using the simplified diagram of atomic He and Ne energy levels given in Fig. 3. A description of the rather complex HeNe excitation process can be given in terms of the following four steps. (a) An energetic electron collisionally excites a He atom to the state labeled 21S0 in Fig. 3. A He atom in this excited state is often written He*(21S0), where the asterisk means that the He atom is in an excited state. (b) The excited He*(21S0) atom collides with an unexcited Ne atom and the atoms exchange internal energy, with an unexcited He atom and excited Ne atom, written Ne*(3S2), resulting. This energy exchange process occurs with high probability only because of the accidental near equality of the two excitation energies of the two levels in these atoms. (c) The 3S2 level of Ne is an example of a metastable atomic state, meaning that it is only after a relatively long period of time - on atomic time scales - that the Ne*(3S2) atom deexcites to the 2P4 level by emitting a photon of wavelength 6328 Å. It is this emission of 6328 Å light by Ne atoms that, in the presence of a suitable optical configuration, leads to lasing action. (d) The excited Ne*(2P4) atom rapidly deexcites to its ground state by emitting additional photons or by collisions with the plasma tube walls. Because of the extreme quickness of the deexcitation process, at any moment in the HeNe plasma, there are more Ne atoms in the 3S2 state than there are in the 2P4 state, and a population inversion is said to be established between these two levels. When a population inversion is established between the 3S2 and 2P4 levels of the Ne atoms in the discharge, the discharge can act as an optical gain or amplification medium for light of wavelength 6328 Å. This is because a photon incident on the gas discharge will have a greater probability of being replicated in a 3S2-->2P4 stimulated emission process (discussed below) than of being destroyed in the complementary 2P4-->3S2 absorption process. (3) Optical resonator or cavity. As mentioned in 2(c) above, Ne atoms in the 3S2 metastable state decay spontaneously to the 2P4 level after a relatively long period of time under normal circumstances; however, a novel circumstance arises if, as shown in Fig. 2, a HeNe discharge is placed between two highly reflecting mirrors that form an optical cavity or resonator along the axis of the discharge. When a resonator structure is in place, photons from the Ne* 3S2-->2P4 transition that are emitted along the axis of the cavity can be reflected hundreds of times between the two highly reflecting end mirrors of the cavity. These reflecting photons can interact with other excited Ne*(3S2) atoms and cause them to emit 6328 Å light in a process known as stimulated emission. The new photon produced in stimulated emission has the same wavelength and polarization, and is emitted in the same direction, as the stimulating photon. It is sometimes useful for purposes of analogy to think of the stimulated emission process as a "cloning" process for photons, as depicted in Fig. 4. The stimulated emission process should be contrasted with spontaneous emission processes that, because they are not caused by any preceding event, produce photons that are emitted isotropically, with random polarization, and over a broader range of wavelengths. As stimulated emission processes occur along the axis of the resonator a situation develops in which essentially all 3S2-->2P4 Ne* decays contribute deexcitation photons to the photon stream reflecting between the two mirrors. This photon multiplication (light amplification) process produces a very large number of photons of the same wavelength and polarization that travel back and forth between the two cavity mirrors. To extract a light beam from the resonator, it is only necessary to have one of the two resonator mirrors, usually called the output coupler, have a reflectivity of only 99% so that 1% of the photons incident on it travel out of the resonator to produce an external laser beam. The other mirror, called the high reflector, should be as reflective as possible. The small diameter, narrow bandwidth, and strong polarization of the HeNe laser beam are determined by the properties of the resonator mirrors and other optical components that lie along the axis of the optical resonator. Back