A Comprehensive Guide on DIY Outdoor Projects That ... - lensesback.com

 2024-10-25 05:23:58

Example 1: Camera MagnificationWhen imaging a sample with a camera, the image is magnified by the objective and the camera tube. If using a 20X Nikon objective and a 0.75X Nikon camera tube, then the image at the camera has 20X × 0.75X = 15X magnification.

The shoulder is located at the base of the objective threading and marks the beginning of the exposed objective body when it is fully threaded into a nosepiece or other objective mount.

[1] R. M. Wood, Optics and Laser Tech. 29, 517 (1998).[2] Roger M. Wood, Laser-Induced Damage of Optical Materials (Institute of Physics Publishing, Philadelphia, PA, 2003).[3] C. W. Carr et al., Phys. Rev. Lett. 91, 127402 (2003).[4] N. Bloembergen, Appl. Opt. 12, 661 (1973).

Pulsed lasers with high pulse repetition frequencies (PRF) may behave similarly to CW beams. Unfortunately, this is highly dependent on factors such as absorption and thermal diffusivity, so there is no reliable method for determining when a high PRF laser will damage an optic due to thermal effects. For beams with a high PRF both the average and peak powers must be compared to the equivalent CW power. Additionally, for highly transparent materials, there is little to no drop in the LIDT with increasing PRF.

The labeling area for an objective usually falls in the middle of the objective body. The labeling found here is dictated by ISO 8578: Microscopes -- Marking of Objectives and Eyepieces, but not all manufacturers adhere strictly to this standard. Generally, one can expect to find the following information in this area:

Threading allows an objective to be mounted to a nosepiece or turret. Objectives can have a number of different thread pitches; Thorlabs offers a selection of microscope thread adapters to facilitate mounting objectives in different systems.

Now compare the maximum power density to that which is specified as the LIDT for the optic. If the optic was tested at a wavelength other than your operating wavelength, the damage threshold must be scaled appropriately. A good rule of thumb is that the damage threshold has a linear relationship with wavelength such that as you move to shorter wavelengths, the damage threshold decreases (i.e., a LIDT of 10 W/cm at 1310 nm scales to 5 W/cm at 655 nm):

Thorlabs' LIDT testing is done in compliance with ISO/DIS 11254 and ISO 21254 specifications.First, a low-power/energy beam is directed to the optic under test. The optic is exposed in 10 locations to this laser beam for 30 seconds (CW) or for a number of pulses (pulse repetition frequency specified). After exposure, the optic is examined by a microscope (~100X magnification) for any visible damage. The number of locations that are damaged at a particular power/energy level is recorded. Next, the power/energy is either increased or decreased and the optic is exposed at 10 new locations. This process is repeated until damage is observed. The damage threshold is then assigned to be the highest power/energy that the optic can withstand without causing damage. A histogram such as that below represents the testing of one BB1-E02 mirror.

Created to provide unmatched product knowledge and expertise in night vision and thermal devices in Canada and beyond, Cold Harbour Supply is dedicated to providing cutting-edge electro-optics, raising standards of end-user education, and offering unparalleled customer service and support.

The energy density of the beam can be compared to the LIDT values of 1 J/cm2 and 3.5 J/cm2 for a BB1-E01 broadband dielectric mirror and an NB1-K08 Nd:YAG laser line mirror, respectively. Both of these LIDT values, while measured at 355 nm, were determined with a 10 ns pulsed laser at 10 Hz. Therefore, an adjustment must be applied for the shorter pulse duration of the system under consideration. As described on the previous tab, LIDT values in the nanosecond pulse regime scale with the square root of the laser pulse duration:

The specifications to the right are measured data for the antireflective (AR) coatings deposited onto the optical surface of our high power focusing objectives. Damage threshold specifications are constant for a given coating type, regardless of the focal length or magnification.

The adjusted LIDT value of 350 W/cm x (1319 nm / 1550 nm) = 298 W/cm is significantly higher than the calculated maximum linear power density of the laser system, so it would be safe to use this doublet lens for this application.

However, the maximum power density of a Gaussian beam is about twice the maximum power density of a uniform beam, as shown in the graph to the right. Therefore, a more accurate determination of the maximum linear power density of the system is 1 W/cm.

Focusing lensfor sale

To adapt the examples shown here to your own microscope, please use our Magnification and FOV Calculator, which is available for download by clicking on the red button above. Note the calculator is an Excel spreadsheet that uses macros. In order to use the calculator, macros must be enabled. To enable macros, click the "Enable Content" button in the yellow message bar upon opening the file.

As the EFL is designed to extend the long-range performance of the GL4 Pro for rifles and PCCs, EFL-equipped GL4 Pros may not be compatible with pistol holsters previously compatible with the GL4 and XVL2. Holster modifications may be required. Check out 4MR Ranch's Review of the EFL Here!Comapatible with the RovyVon GL4 Pro, GL4 Pro XL, and GL4 Pro FP. NOT compatible with the XVL2 or Standard/IR GL4

The Villain Weapon Systems GL4 External Focusing Lens addresses the wide flood pattern of the GL4's IR illuminator and focuses the 300mW beam into a tight spot capable of clearly illuminating your target past 100m. The focusing lens also eliminates the "washout" associated with the close-distance foreground flood illumination of the standard IR illuminator.

Field curvature (or Petzval curvature) describes the case where an objective's plane of focus is a curved spherical surface. This aberration makes widefield imaging or laser scanning difficult, as the corners of an image will fall out of focus when focusing on the center. If an objective's class begins with "Plan", it will be corrected to have a flat plane of focus.

The magnification of a system is the multiplicative product of the magnification of each optical element in the system. Optical elements that produce magnification include objectives, camera tubes, and trinocular eyepieces, as shown in the drawing to the right. It is important to note that the magnification quoted in these products' specifications is usually only valid when all optical elements are made by the same manufacturer. If this is not the case, then the magnification of the system can still be calculated, but an effective objective magnification should be calculated first, as described below.

Pulsed Microsecond Laser ExampleConsider a laser system that produces 1 µs pulses, each containing 150 µJ of energy at a repetition rate of 50 kHz, resulting in a relatively high duty cycle of 5%. This system falls somewhere between the regimes of CW and pulsed laser induced damage, and could potentially damage an optic by mechanisms associated with either regime. As a result, both CW and pulsed LIDT values must be compared to the properties of the laser system to ensure safe operation.

Pulsed Nanosecond Laser Example: Scaling for Different WavelengthsSuppose that a pulsed laser system emits 10 ns pulses at 2.5 Hz, each with 100 mJ of energy at 1064 nm in a 16 mm diameter beam (1/e2) that must be attenuated with a neutral density filter. For a Gaussian output, these specifications result in a maximum energy density of 0.1 J/cm2. The damage threshold of an NDUV10A Ø25 mm, OD 1.0, reflective neutral density filter is 0.05 J/cm2 for 10 ns pulses at 355 nm, while the damage threshold of the similar NE10A absorptive filter is 10 J/cm2 for 10 ns pulses at 532 nm. As described on the previous tab, the LIDT value of an optic scales with the square root of the wavelength in the nanosecond pulse regime:

Safe practices and proper usage of safety equipment should be taken into consideration when operating lasers. The eye is susceptible to injury, even from very low levels of laser light. Thorlabs offers a range of laser safety accessories that can be used to reduce the risk of accidents or injuries. Laser emission in the visible and near infrared spectral ranges has the greatest potential for retinal injury, as the cornea and lens are transparent to those wavelengths, and the lens can focus the laser energy onto the retina.

Focusing lenslaser

As the magnification increases, the resolution improves, but the field of view also decreases. The dependence of the field of view on magnification is shown in the schematic to the right.

Focusing LensThorlabs

Dipping objectives are designed to correct for the aberrations introduced by the specimen being submerged in an immersion fluid. The tip of the objective is either dipped or entirely submerged into the fluid.

Focusing objectives can be used in a variety of applications where intense optical power is necessary, such as laser cutting or engraving. At lower powers, focused laser light can be used for wafer inspection or to activate special types of photoresist in photolithography. Because all the objectives on this page have a limited field of view, laser scanning should be performed by moving either the sample or the objective. When incorporating these objectives into a system, note that the labeled magnifications of these objectives are calculated assuming the objective is being use with a 200 mm focal length tube lens.

Also referred to as the parfocal distance, this is the length from the shoulder to the top of the specimen (in the case of objectives that are intended to be used without a cover glass) or the top of the cover glass. When working with multiple objectives in a turret, it is helpful if all of the parfocal distances are identical, so little refocusing will be required when switching between objectives. Thorlabs offers parfocal length extenders for instances in which the parfocal length needs to be increased.

In both the large (T → ∞) and small (T → 0) limits, K approaches well-known theoretical results. For small T, which corresponds to an entrance pupil much larger than the Gaussian spot, K obeys the relation 1.27/T. This can be obtained from Gaussian beam propagation theory [2] which predicts that the minimum spot size a Gaussian beam can be focused to is s ≈ 1.27λf/S. By inserting factors of D to write this in terms of N and T, this expression can be cast into the same form as the spot size equation above, s = (1.27/T)λN, giving the result K = 1.27/T. As seen in Figure 2 above, this accurately predicts the focused spot size up to T ≈ 0.5, when the entrance pupil diameter D is twice as large as the spot size S. Above T = 0.5, it underestimates the value of K, as indicated by the deviation of the dashed blue line from the numerical results.

Beam diameter is also important to know when comparing damage thresholds. While the LIDT, when expressed in units of J/cm², scales independently of spot size; large beam sizes are more likely to illuminate a larger number of defects which can lead to greater variances in the LIDT [4]. For data presented here, a <1 mm beam size was used to measure the LIDT. For beams sizes greater than 5 mm, the LIDT (J/cm2) will not scale independently of beam diameter due to the larger size beam exposing more defects.

FocusLensprice

When imaging a sample with a camera, the dimensions of the sample area are determined by the dimensions of the camera sensor and the system magnification, as shown by Equation 2.

The DLP mirror is actuated via a computer controlled oscillator circuit. A laser beam directed to the mirror is either passed to a target detector, or diverted, ...

This adjustment factor results in LIDT values of 0.45 J/cm2 for the BB1-E01 broadband mirror and 1.6 J/cm2 for the Nd:YAG laser line mirror, which are to be compared with the 0.7 J/cm2 maximum energy density of the beam. While the broadband mirror would likely be damaged by the laser, the more specialized laser line mirror is appropriate for use with this system.

For each focusing objective that Thorlabs provides, we provide an estimate of the focused spot size when the incident Gaussian spot size (1/e2) is the same as the diameter of the entrance pupil. With this choice, the focused spot size is given by:s ≈ 1.83λN, or equivalently, s ≈ 1.83λ/(2*NA), where NA is the numerical aperture of the objective; and the transmitted power is 86% of that of the incident beam.

The GL4 Pro EFL gives two illuminator patterns selectable via an included spacer that can be added or removed during the Lens installation:

Lasers are categorized into different classes according to their ability to cause eye and other damage. The International Electrotechnical Commission (IEC) is a global organization that prepares and publishes international standards for all electrical, electronic, and related technologies. The IEC document 60825-1 outlines the safety of laser products. A description of each class of laser is given below:

Immersion objectives are similar to water-dipping objectives; however, in this case the sample is under a cover glass. A drop of fluid is then added to the top of the cover glass, and the tip of the objective is brought into contact with the fluid. Often, immersion objectives feature a correction collar to adjust for cover glasses with different thicknesses. Immersion fluids include water, oil (such as MOIL-30), and glycerol.

NaCl is made up of two elements sodium and chlorine in the simple ratio of 1:1. The sodium atom donates one electron to the chlorine atom forming an ...

For intermediate values of T, which is the range in which most applications will fall, there is no exact theoretical result for K. Instead, the red line above represents a two-term polynomial fit to the numerical results, the coefficients of which are specified in the table below (the polynomial fit was performed using 1/T as the independent variable). This expression may be used to estimate K for T ≥ 0.5.

Focusing lensoptics

Use this field of view (FOV) calculator to setup screens correctly for sim racing, giving you a better feel and making you faster and more consistent.

Each 50X objective is equipped with a cover glass correction collar with engraved graduations, in mm, for fused silica coverslip thicknesses from 0 to 1 mm. In addition, the 1064 nm variant is engraved with a scale for up to 1.2 mm thick silicon carbide coverslips. The scales span the majority of the objectives' circumferences, allowing for smooth, precise adjustment. Once the correct position is found, the collar can be locked in place by tightening the setscrew below it with the included 0.050" hex key. Custom graduations for specific cover glass materials including sapphire (Al2O3), silicon (Si), silicon carbide (SiC), gallium arsenide (GaAs), and gallium nitride (GaN) can be made on request; please contact Tech Support for more details.

The focused spot size is expressed in terms of the wavelength, truncation ratio, and f-number as where K(T) is called the spot size coefficient and is a function of the truncation ratio [1]. In Figure 2 below, numerically computed values for K, obtained by calculating the focused intensity profile and extracting the focused spot size for discrete values of T, are plotted as black squares. As discussed in detail below, the solid-and-dashed blue line represents the coefficient predicted by Gaussian beam theory, the gray line represents the value of K for an Airy disk intensity profile, and the red line is a polynomial fit to the numerical values for T ≥ 0.5.

Focusing lenscost

CW Laser ExampleSuppose that a CW laser system at 1319 nm produces a 0.5 W Gaussian beam that has a 1/e2 diameter of 10 mm. A naive calculation of the average linear power density of this beam would yield a value of 0.5 W/cm, given by the total power divided by the beam diameter:

The energy density of your beam should be calculated in terms of J/cm2. The graph to the right shows why expressing the LIDT as an energy density provides the best metric for short pulse sources. In this regime, the LIDT given as an energy density can be applied to any beam diameter; one does not need to compute an adjusted LIDT to adjust for changes in spot size. This calculation assumes a uniform beam intensity profile. You must now adjust this energy density to account for hotspots or other nonuniform intensity profiles and roughly calculate a maximum energy density. For reference a Gaussian beam typically has a maximum energy density that is twice that of the 1/e2 beam.

When a laser beam is focused by an objective, the resulting spot size (s) will depend upon the wavelength of the light (λ), the beam diameter as it enters the objective (S), the focal length of the objective (f), and the entrance pupil diameter of the objective (D). Dimensionless parameters are formed by taking the ratio of the focal length to the entrance pupil diameter and the ratio of the beam diameter to the entrance pupil diameter, which are known respectively as the f-number (N = f/D) and the truncation ratio (T = S/D). The f-number is fixed for a given objective, while the truncation ratio may be tuned by increasing or decreasing the incident beam diameter.

Please note that we have a buffer built in between the specified damage thresholds online and the tests which we have done, which accommodates variation between batches. Upon request, we can provide individual test information and a testing certificate. The damage analysis will be carried out on a similar optic (customer's optic will not be damaged). Testing may result in additional costs or lead times. Contact Tech Support for more information.

If this relatively long-pulse laser emits a Gaussian 12.7 mm diameter beam (1/e2) at 980 nm, then the resulting output has a linear power density of 5.9 W/cm and an energy density of 1.2 x 10-4 J/cm2 per pulse. This can be compared to the LIDT values for a WPQ10E-980 polymer zero-order quarter-wave plate, which are 5 W/cm for CW radiation at 810 nm and 5 J/cm2 for a 10 ns pulse at 810 nm. As before, the CW LIDT of the optic scales linearly with the laser wavelength, resulting in an adjusted CW value of 6 W/cm at 980 nm. On the other hand, the pulsed LIDT scales with the square root of the laser wavelength and the square root of the pulse duration, resulting in an adjusted value of 55 J/cm2 for a 1 µs pulse at 980 nm. The pulsed LIDT of the optic is significantly greater than the energy density of the laser pulse, so individual pulses will not damage the wave plate. However, the large average linear power density of the laser system may cause thermal damage to the optic, much like a high-power CW beam.

This scaling gives adjusted LIDT values of 0.08 J/cm2 for the reflective filter and 14 J/cm2 for the absorptive filter. In this case, the absorptive filter is the best choice in order to avoid optical damage.

Example 4: Sample AreaThe dimensions of the camera sensor in Thorlabs' previous-generation 1501M-USB Scientific Camera are 8.98 mm × 6.71 mm. If this camera is used with the Nikon objective and trinoculars from Example 1, which have a system magnification of 15X, then the image area is:

The images of a mouse kidney below were all acquired using the same objective and the same camera. However, the camera tubes used were different. Read from left to right, they demonstrate that decreasing the camera tube magnification enlarges the field of view at the expense of the size of the details in the image.

Following Equation 1 and the table to the right, we calculate the effective magnification of an Olympus objective in a Nikon microscope:

by W Zhao · 2015 · Cited by 17 — 1. Introduction · The UFL has a small numerical aperture (N.A.) to make the focal range long due to the diffraction effect, so it is difficult to precisely ...

The optimal balance between spot size and power transmission will depend upon the given application. For each focusing objective that Thorlabs offers, we provide an estimate of the spot size using T = 1, when the Gaussian spot size is the same as the diameter of the entrance pupil. With this choice, the spot size is given by: s ≈ 1.83λN, or equivalently, s ≈ 1.83λ/(2*NA), where NA is the numerical aperture of the objective.

While this rule of thumb provides a general trend, it is not a quantitative analysis of LIDT vs wavelength. In CW applications, for instance, damage scales more strongly with absorption in the coating and substrate, which does not necessarily scale well with wavelength. While the above procedure provides a good rule of thumb for LIDT values, please contact Tech Support if your wavelength is different from the specified LIDT wavelength. If your power density is less than the adjusted LIDT of the optic, then the optic should work for your application.

Pulses shorter than 10-9 s cannot be compared to our specified LIDT values with much reliability. In this ultra-short-pulse regime various mechanics, such as multiphoton-avalanche ionization, take over as the predominate damage mechanism [2]. In contrast, pulses between 10-7 s and 10-4 s may cause damage to an optic either because of dielectric breakdown or thermal effects. This means that both CW and pulsed damage thresholds must be compared to the laser beam to determine whether the optic is suitable for your application.

Objectives that feature a built-in iris diaphragm are ideal for darkfield microscopy. The iris diaphragm is designed to be partially closed during darkfield microscopy in order to preserve the darkness of the background. This is absolutely necessary for high numerical aperture (above NA = 1.2) oil immersion objectives when using an oil immersion darkfield condenser. For ordinary brightfield observations, the iris diaphragm should be left fully open.

Note that Leica, Mitutoyo, Nikon, and Thorlabs use the same tube lens focal length; if combining elements from any of these manufacturers, no conversion is needed. Once the effective objective magnification is calculated, the magnification of the system can be calculated as before.

Using an immersion fluid with a high refractive index allows objectives to achieve numerical apertures greater than 1.0. However, if an immersion objective is used without the fluid present, the image quality will be very low. Objectives following ISO 8578: Microscopes -- Marking of Objectives and Eyepieces will be labeled with an identifier ring to tell the user what immersion fluid the objective is designed to be used with; a list of ring colors can be found in the table above.

Objectives with very small working distances may have a retraction stopper incorporated into the tip. This is a spring-loaded section which compresses to limit the force of impact in the event of an unintended collision with the sample.

When pulse lengths are between 1 ns and 1 µs, laser-induced damage can occur either because of absorption or a dielectric breakdown (therefore, a user must check both CW and pulsed LIDT). Absorption is either due to an intrinsic property of the optic or due to surface irregularities; thus LIDT values are only valid for optics meeting or exceeding the surface quality specifications given by a manufacturer. While many optics can handle high power CW lasers, cemented (e.g., achromatic doublets) or highly absorptive (e.g., ND filters) optics tend to have lower CW damage thresholds. These lower thresholds are due to absorption or scattering in the cement or metal coating.

When an optic is damaged by a continuous wave (CW) laser, it is usually due to the melting of the surface as a result of absorbing the laser's energy or damage to the optical coating (antireflection) [1]. Pulsed lasers with pulse lengths longer than 1 µs can be treated as CW lasers for LIDT discussions.

Thorlabs expresses LIDT for CW lasers as a linear power density measured in W/cm. In this regime, the LIDT given as a linear power density can be applied to any beam diameter; one does not need to compute an adjusted LIDT to adjust for changes in spot size, as demonstrated by the graph to the right. Average linear power density can be calculated using the equation below.

As previously stated, pulsed lasers typically induce a different type of damage to the optic than CW lasers. Pulsed lasers often do not heat the optic enough to damage it; instead, pulsed lasers produce strong electric fields capable of inducing dielectric breakdown in the material. Unfortunately, it can be very difficult to compare the LIDT specification of an optic to your laser. There are multiple regimes in which a pulsed laser can damage an optic and this is based on the laser's pulse length. The highlighted columns in the table below outline the relevant pulse lengths for our specified LIDT values.

Our MicroSpot objectives are externally RMS-threaded (0.800"-36), which allows them to be mounted directly to our fiber launch systems, DIY Cerna® Microscope Systems, and microscope objective turrets; to convert RMS threads to M32 x 0.75 threads, we offer the M32RMSS brass thread adapter. Our 5X, 10X, and 20X objectives can be mounted to any of our flexure stages using an HCS013 RMS mount. An objective case (OC2RMS lid and OC22 canister) is included with our 50X objectives and an aluminum cap (RMSCP1) is available for purchase separately.

Hi HAVE USED ON FIRM CONDITION OF:: OPTOMETRIST AND OPTICAL STORE MARCO SLITLAMP WITH OUT TABLE UNIT CHECK BY OPTOMETRIST ASKING $600.00 ...

An objective lens determines the basic performance of an optical microscope or imaging systems and is designed for various performance needs and applications.

Objectives following ISO 8578: Microscopes -- Marking of Objectives and Eyepieces will be labeled with an identifier ring to tell the user what immersion fluid the objective is designed to be used with; a list of ring colors can be found in the table to the right.

These objectives are capable of producing a near-diffraction-limited spot size when used with a monochromatic source within the 450 - 2100 nm range that fills the entrance aperture, also known as the entrance pupil. However, if used at a wavelength other than the design wavelength, the effective focal length listed on the Specs tab will shift and the AR coating will no longer be optimized; see the Graphs tab for AR coating plots. Custom AR Coatings are available by contacting Tech Support to optimize the performance of these objectives at other wavelengths. When working with wavelengths outside of the visible, consider using some of Thorlabs' laser viewing cards to help locate and align your beam.

Images can also exhibit chromatic aberrations, where colors originating from one point are not focused to a single point. To strike a balance between an objective's performance and the complexity of its design, some objectives are corrected for these aberrations at a finite number of target wavelengths.

Laser beams typically have a tranverse intensity profile that may be approximated by a Gaussian function,,where w is the beam half-width or beam waist radius, conventionally defined as the radius (r) at which the intensity has decreased from its maximum axial value of I0 to I0/e2 ≈ 0.14I0. The spot size of a laser beam may be defined as twice the beam waist radius, and the corresponding circle with diameter equal to the spot size thus contains 86% of the beam's total intensity.

Through focus MTF describes how the MTF of an optical system varies as the image plane moves through the focal region for a chosen spatial frequency.

Here, the Design Magnification is the magnification printed on the objective, fTube Lens in Microscope is the focal length of the tube lens in the microscope you are using, and fDesign Tube Lens of Objective is the tube lens focal length that the objective manufacturer used to calculate the Design Magnification. These focal lengths are given by the table to the right.

Five objective classes are shown in the table to the right; only three common objective classes are defined under the International Organization for Standards ISO 19012-2: Microscopes -- Designation of Microscope Objectives -- Chromatic Correction. Due to the need for better performance, we have added two additional classes that are not defined in the ISO classes.

LIDT in linear power density vs. pulse length and spot size. For long pulses to CW, linear power density becomes a constant with spot size. This graph was obtained from [1].

A cover glass, or coverslip, is a small, thin sheet of glass that can be placed on a wet sample to create a flat surface to image across.

A Cold Harbour Supply Exclusive Product. 100% Designed and Made in the USA by Villain Weapon SystemsGL4-Pro not included, to buy this as a package check out this page: HERE

As T is increased, the illumination of the aperture becomes more and more uniform. The resulting intensity profile of the focused spot will therefore transition from a Gaussian profile to an Airy disk profile. In the large T limit, this is reflected in the value of K, which approaches a constant value of 1.6449 as T → ∞. This value corresponds to the 1/e2 spot size of an Airy disk instead of the better-known 2.44λN value which is where the first intensity minimum occurs, as shown in Figure 4 [3].

References[1] Hakan Urey, "Spot size, depth-of-focus, and diffraction ring intensity formulas for truncated Gaussian beams," Appl. Opt. 43, 620-625 (2004)[2] Sidney A. Self, "Focusing of spherical Gaussian beams," Appl. Opt. 22, 658-661 (1983)[3] Eugene Hecht, "Optics," 4th Ed., Addison-Wesley (2002)

As described above, the maximum energy density of a Gaussian beam is about twice the average energy density. So, the maximum energy density of this beam is ~0.7 J/cm2.

This microscope objective serves only as an example. The features noted above with an asterisk may not be present on all objectives; they may be added, relocated, or removed from objectives based on the part's needs and intended application space.

For wavelengths between 192 nm - 500 nm, Thorlabs offers UV MicroSpot Laser Focusing Objectives in a number of magnifications; this range covers many excimer lasers which cure photoresist, such as KrF lasers (248 nm) and ArF lasers (193 nm).

The camera sensor dimensions can be obtained from the manufacturer, while the system magnification is the multiplicative product of the objective magnification and the camera tube magnification (see Example 1). If needed, the objective magnification can be adjusted as shown in Example 3.

The pulse length must now be compensated for. The longer the pulse duration, the more energy the optic can handle. For pulse widths between 1 - 100 ns, an approximation is as follows:

The working distance, often abbreviated WD, is the distance between the front element of the objective and the top of the specimen (in the case of objectives that are intended to be used without a cover glass) or top of the cover glass. The cover glass thickness specification engraved on the objective designates whether a cover glass should be used.

Focusing LensDestiny 2

Thorlabs' High-Power MicroSpot® Focusing Objectives are designed to focus on-axis laser beams to a diffraction-limited spot. We offer center wavelengths of 532 nm, 850 nm, and 1064 nm, with AR coatings of 490 - 570 nm, 790 - 910 nm, and 980 - 1130 nm, respectively. These objectives can be used at common fiber laser wavelengths including 515 nm, 808 nm, 1030 nm, or 1070 nm. Objectives with a 532 nm or 1064 nm center wavelength are also ideal for use with Nd:YAG lasers; for additional optics for use with these lasers, see the Nd:YAG Optics tab. All of the focusing objectives below offer a damage threshold of ≥15 J/cm2 (see the Damage Thresholds tab for more details). The RMS threading on each of our MicroSpot objectives allows for easy integration into existing systems, and their robust housing and fused silica lens design is built to hold up to consistent industrial or laboratory use.

March U.K. Limited (2003–2008); Shop Direct Limited (2008–2020) · Private Limited Company · Retail · Home shopping · Financial services · Littlewoods Shop Direct ...

The calculation above assumes a uniform beam intensity profile. You must now consider hotspots in the beam or other non-uniform intensity profiles and roughly calculate a maximum power density. For reference, a Gaussian beam typically has a maximum power density that is twice that of the uniform beam (see lower right).

The following is a general overview of how laser induced damage thresholds are measured and how the values may be utilized in determining the appropriateness of an optic for a given application. When choosing optics, it is important to understand the Laser Induced Damage Threshold (LIDT) of the optics being used. The LIDT for an optic greatly depends on the type of laser you are using. Continuous wave (CW) lasers typically cause damage from thermal effects (absorption either in the coating or in the substrate). Pulsed lasers, on the other hand, often strip electrons from the lattice structure of an optic before causing thermal damage. Note that the guideline presented here assumes room temperature operation and optics in new condition (i.e., within scratch-dig spec, surface free of contamination, etc.). Because dust or other particles on the surface of an optic can cause damage at lower thresholds, we recommend keeping surfaces clean and free of debris. For more information on cleaning optics, please see our Optics Cleaning tutorial.

Now compare the maximum energy density to that which is specified as the LIDT for the optic. If the optic was tested at a wavelength other than your operating wavelength, the damage threshold must be scaled appropriately [3]. A good rule of thumb is that the damage threshold has an inverse square root relationship with wavelength such that as you move to shorter wavelengths, the damage threshold decreases (i.e., a LIDT of 1 J/cm2 at 1064 nm scales to 0.7 J/cm2 at 532 nm):

Example 3: Trinocular Magnification (Different Manufacturers)When imaging a sample through trinoculars, the image is magnified by the objective and the eyepieces in the trinoculars. This example will use a 20X Olympus objective and Nikon trinoculars with 10X eyepieces.

The widest aperture available on the lens gives the shallowest depth of field. For example, on a lens with a maximum aperture of f/2.8, if the ...

Objectives are commonly divided by their class. An objective's class creates a shorthand for users to know how the objective is corrected for imaging aberrations. There are two types of aberration corrections that are specified by objective class: field curvature and chromatic aberration.

Pulsed Nanosecond Laser Example: Scaling for Different Pulse DurationsSuppose that a pulsed Nd:YAG laser system is frequency tripled to produce a 10 Hz output, consisting of 2 ns output pulses at 355 nm, each with 1 J of energy, in a Gaussian beam with a 1.9 cm beam diameter (1/e2). The average energy density of each pulse is found by dividing the pulse energy by the beam area:

Objectives can be divided by what medium they are designed to image through. Dry objectives are used in air; whereas dipping and immersion objectives are designed to operate with a fluid between the objective and the front element of the sample.

Jul 15, 2015 — Typically, aberrations are more prevalent on lenses with low f/numbers. In most cases, the aberration can be reduced by stopping the lens to a ...

In order to illustrate the process of determining whether a given laser system will damage an optic, a number of example calculations of laser induced damage threshold are given below. For assistance with performing similar calculations, we provide a spreadsheet calculator that can be downloaded by clicking the button to the right. To use the calculator, enter the specified LIDT value of the optic under consideration and the relevant parameters of your laser system in the green boxes. The spreadsheet will then calculate a linear power density for CW and pulsed systems, as well as an energy density value for pulsed systems. These values are used to calculate adjusted, scaled LIDT values for the optics based on accepted scaling laws. This calculator assumes a Gaussian beam profile, so a correction factor must be introduced for other beam shapes (uniform, etc.). The LIDT scaling laws are determined from empirical relationships; their accuracy is not guaranteed. Remember that absorption by optics or coatings can significantly reduce LIDT in some spectral regions. These LIDT values are not valid for ultrashort pulses less than one nanosecond in duration.

Example 2: Trinocular MagnificationWhen imaging a sample through trinoculars, the image is magnified by the objective and the eyepieces in the trinoculars. If using a 20X Nikon objective and Nikon trinoculars with 10X eyepieces, then the image at the eyepieces has 20X × 10X = 200X magnification. Note that the image at the eyepieces does not pass through the camera tube, as shown by the drawing to the right.

LIDT in energy density vs. pulse length and spot size. For short pulses, energy density becomes a constant with spot size. This graph was obtained from [1].

The effective magnification of the Olympus objective is 22.2X and the trinoculars have 10X eyepieces, so the image at the eyepieces has 22.2X × 10X = 222X magnification.

Focusing Lenswow

Magnification is not a fundamental value: it is a derived value, calculated by assuming a specific tube lens focal length. Each microscope manufacturer has adopted a different focal length for their tube lens, as shown by the table to the right. Hence, when combining optical elements from different manufacturers, it is necessary to calculate an effective magnification for the objective, which is then used to calculate the magnification of the system.

Use this formula to calculate the Adjusted LIDT for an optic based on your pulse length. If your maximum energy density is less than this adjusted LIDT maximum energy density, then the optic should be suitable for your application. Keep in mind that this calculation is only used for pulses between 10-9 s and 10-7 s. For pulses between 10-7 s and 10-4 s, the CW LIDT must also be checked before deeming the optic appropriate for your application.

The results presented above suggest that, in the intermediate T regime, a smaller spot size may be achieved by increasing T. This, however, comes at the cost of reducing the overall power transmitted through the entrance aperture, and reductions in spot size may not be worth the loss in power. The power transmitted through an entrance pupil of diameter D as a function of T is plotted above in Figure 3. Already at T = 1, when the Gaussian spot size has the same diameter as the entrance pupil, the transmitted power is 86% of the incident power. By increasing T from 1 to 2, the spot size is reduced by only ≈ 9%, while the transmitted power decreases from 86% to 40%.

In order to facilitate fast identification, nearly all microscope objectives have a colored ring that circumscribes the body. A breakdown of what magnification each color signifies is given in the table below.

According to the test, the damage threshold of the mirror was 2.00 J/cm2 (532 nm, 10 ns pulse, 10 Hz, Ø0.803 mm). Please keep in mind that these tests are performed on clean optics, as dirt and contamination can significantly lower the damage threshold of a component. While the test results are only representative of one coating run, Thorlabs specifies damage threshold values that account for coating variances.

Additionally, the objective label area may include the objective's specified wavelength range, specialty features or design properties, and more. The exact location and size of each and any of these elements can vary.

The spot size achieved by focusing a laser beam with a lens or objective is an important parameter in many applications. This tutorial describes how the ratio of the initial beam diameter to the entrance pupil diameter, known as the truncation ratio, affects the focused spot size and provides expressions for calculating the spot size as a function of this ratio. Because the power transmitted by the focusing optic also depends upon the truncation ratio, the optimal balance between spot size and power transmission will depend upon the given application.

An AC127-030-C achromatic doublet lens has a specified CW LIDT of 350 W/cm, as tested at 1550 nm. CW damage threshold values typically scale directly with the wavelength of the laser source, so this yields an adjusted LIDT value:

If an objective is used for water dipping, water immersion, or oil immersion, a second colored ring may be placed beneath the magnification identifier. If the objective is designed to be used with water, this ring will be white. If the objective is designed to be used with oil, this ring will be black. Dry objectives lack this identifier ring entirely. See the table to the right for a complete list of immersion identifiers.

The most common, a standard #1.5 cover glass, is designed to be 0.17 mm thick. Due to variance in the manufacturing process the actual thickness may be different. The correction collar present on select objectives is used to compensate for cover glasses of different thickness by adjusting the relative position of internal optical elements. Note that many objectives do not have a variable cover glass correction, in which case the objectives have no correction collar. For example, an objective could be designed for use with only a #1.5 cover glass. This collar may also be located near the bottom of the objective, instead of the top as shown in the diagram.