For calculation, we use the same triangle as we did in the first case, with a peak at the lens and the base at the field of view.

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

Field of viewmicroscope Calculator

Triangle calculation involves applying trigonometry to calculate the angle of view. There are two different possibilities to calculate the angle.

After we calculate the length of all three sides of a right triangle then we can use trigonometry to calculate the angle γ.

With the right-triangle method, we use the same triangle as we did in the first chapter with a peak at the lens and the base at the field of view. We divide the triangle into two right triangles.

(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

How to calculatefield of viewdiameter

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

n order to convert the field of view expressed in degrees to meters we can use the same two methods as we did in the first chapter. The only difference is that instead of an angle γ we need to calculate the chord/arc length value.

Calculating field of viewcalculator

Field of view is the measured area of the scene a person sees when looking through the binoculars. It depends on the build of the eyepiece, thickness of the lenses and it is also affected by magnification. Field of view can be expressed in multiple measurements. Measurements in yards, feet, and meters are called the linear field of view. Besides the linear field of view, there is also an angular field of view where the field of view is provided in angular degrees.

The segment of a circle is a totally different method to calculate the angle. For calculations, we don’t use a linear chord but a circular arc.

The first possibility uses a triangle with a peak at the lens and the base at the field of view. Before we start to make any calculations, we must divide the triangle into two right triangles.

Although we used two different triangle methods to calculate the angle, the results are the same. This means that it is not important which triangle method we use. If you want to calculate the angle of view for your binoculars with the triangle calculation you can use the method that you prefer best.

Field of viewmicroscope 10X

Calculating field of view ofa microscope

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

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

As the FOV increases the segment method is more accurate. I also think that the segment method is easier to calculate than both triangle methods. The segment method is easier to use because there is no trigonometry in its calculations.

Calculating field of viewformula

When we look at the results we can see that there are some differences between calculation methods. When we used the triangle method the linear FOV in both cases is 122.09707m. This means that it doesn’t matter which triangle method we use to calculate the linear FOV. When we calculate FOV with a segment method we got a bit different result, 122.17304m. I think that the segment method is easier to calculate than the triangle method.

If the angle is high this means that the field of view is wide – the higher the angle, the wider the field of view. I wrote this article because I wanted to show you how to convert linear FOV to angular FOV and the other way around.

Calculating field of viewmicroscope Worksheet

With the segment method, the angle is different, 7.1619°. Both methods provide pretty similar answers, but if we change the FOV from 125m/1000m to 140m/1000m we can see that the difference in angle increases. If the FOV is 125m/1000m the difference in angle between triangle and a segment of a circle method is 4.7*10-3. If FOV is 140m/1000m the difference in angle increases to 6.5*10-3.

I started to write this article because I wanted to find out if there is any difference in angle value when using different calculation methods.

(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

(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

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.

If you wish to calculate the FOV for your binocular with any of these methods there is an Excel file attached. In the file, there are formulas for all three methods.

This article will help you if FOV is expressed in meters or yards and you want it to be in degrees. Most manufacturers already state how much is the angle of view on their optical devices. If you are still not certain what is the size of the angle on your binocular, here are some methods how to calculate it.

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

If we use the second method, there is no need to divide the triangle. The law of cosines is used for calculating the angles of a triangle if we know all three sides (as it is in our case).

The value of hypotenuse (h) also depends on a field of view value. With riflescopes, the hypotenuse is set at 100m because the field of view is being measured at 100m. With binoculars, spotting scopes, and other optical devices the field of view is measured at 1000m, so the hypotenuse is also 1000m.

We can see that there are some differences between both calculation methods. With the triangle method, the angle γ in both cases is 7.1666°. This means that it doesn’t matter which triangle method we use to calculate the angle.

Field of viewmicroscope 40x

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 two methods to calculate the angle of view. You can use a triangle calculation or a segment of a circle. There is a difference in the distance line between both methods. The triangle method uses the length of a chord while a segment of a circle uses curved boundary length (circular arc) for calculation.

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 .

(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

(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

(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

Thank you for your this article on FOV. As an aside, adding the .xlsx makes up for not mentioning apparent FOV, AFOV. I like your academic approach. Yet I would prefer defining the Object Distance along the optical axis rather than the hypotenuse. What do you think? The object´s position is on the chord, not on the virtual arc.