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Frequently Asked Questions

I have a lens/filter/mirror/optic that I purchased from CVI Laser Optics and I want to clean it. What cleaning methods are recommended for my item?

The recommended cleaning methods are dependent on the type of optic and its coatings.

You can download the recommended CVI Laser Optics cleaning procedures document Cleaning Methods (PDF).

The first part of the document describes five separate cleaning procedures with step-by-step instructions. The second part of the document lists which procedures should be used for which component.

You can also download this article Cleaning Optics (PDF) which explains the importance of the cleaning process to improve both the lifetime and performance of optics. Proper materials, techniques and handling procedures should be used to minimize the risk of damage.

Helpful Light Beam Definitions

Continuous Wave
Laser power is fixed or variable, but not delivered in a discrete pulse envelope.

Laser energy is delivered in a single discrete pulse at a specified repetition rate.

The average power of a continuous wave (cw) laser beam expressed in watts (W).

Energy per Pulse
The energy of an individual pulse expressed in joules (J).

Pulse Repetition Rate
The rate at which pulses are repeated in a uniformly pulsed train of pulses expressed at the frequency of repetition of the pulses in the unit of hertz (pulses per second, Hz).

Gaussian Criteria
The definition as used in the ANSI Z136.1 Standard for both beam diameter and beam divergence, require that these quantities be measured at the 1/e power point (63.2%) on the ideal Gaussian beam intensity profile. Note that most laser equipment manufacturers specify these beam properties at the 1/e2 power point (86.5%), which is a factor of 1.414 larger than the 1/e power point.

Beam Dimension
Beam size (typically diameter) in millimeters, measured on the longest dimension.

Beam Divergence
Change in beam size with respect to distance measured in milliradians.

What is the index/transmission of a certain optical material at a certain wavelength?

Typical index and transmission values for our optical materials can be found in our catalog. This link will open the appropriate section Material Properties (PDF).

I want to purchase one of your optical products, but the coating I want is not listed on the website as available for that product. Can I still get the coating I want?

Most of the time, yes. The optic & coating combinations shown on the Buy-Online section are our most popular ones, and are the most likely to be readily available. Our full selection of antireflection and high-reflection coatings can be applied to our line of optics for an additional fee. For coating recommendations, availability, and pricing please contact one of our Applications Engineers.

What is the damage threshold for your anti-reflective and mirror coatings?

CVI Laser Optics has tested the majority of our coatings for their damage threshold specifications. We understand that it is important to our customers to know what this limit is in order to preserve the integrity of their optical systems.

This link will open the appropriate Coatings (PDF) section of our catalog. Below each coating, there is a typical damage threshold listed. When coatings are very similar in composition, there may be a reference to another coating for its damage threshold. Please note that all the values given are for reference only and do not imply a guarantee.

There are many different applications for the coatings, so we tried to test them with a common laser for the specified range of the coating. They were typically tested using a pulsed 1064 nm laser and its harmonics. Unfortunately, we could not possibly test them for all different configurations, including continuous (CW) lasers. There are simply too many parameters that affect the damage threshold of a coating. Therefore, we do not have any other data than what is specified in the catalog and there is not a simple formula to determine how a different wavelength might respond.

Can CVI Laser Optics modify standard optics to custom sizes?

Yes, we can! Our ability to modify includes edging diameters down and cutting to square or rectangular shapes. This includes lenses (both spherical and cylindrical), mirrors, and filters (excluding the interference filters).

There are a few rules of thumb to follow when modifying standard pieces:

The standard tolerance for modifications is ±0.25 mm (±0.01"). If a customer needs a tighter tolerance, it must be specified.

A standard lens can be edged down to a diameter that is no less than twice the center thickness of the lens. For example, the smallest we could edge a beginning diameter of 30 mm and center thickness 8.4 mm is down to 17 mm.

A mirror can be modified, but the flatness cannot be maintained to the original specification because stress is induced when a piece is modified. We can also use CNC processing to create 1-off pieces in a myriad of size and radii options. And, finally, we make custom lenses in larger batches for many customers and applications.

I was looking through your concave reflectors and your spherical mirrors but couldn't find the correct radius of curvature that I need. Do you make custom reflectors?

Yes, we can! We can also put a reflective coating on one of our plano-concave (or plano-convex) lenses.

Do you coat Customer Furnished Materials?

We have recently announced a new service to coat Customer Furnished Materials. Please see the link below for our press release. Any further questions should be directed to the contact information at the bottom of the press release.

The calibration date on my filter's spectral curve sheet expired. Do I need to recalibrate the filter?

No, the calibration date listed on the filter spectral curve sheets are the next calibration due date for the spectrometer on which the curve was measured. It has no effect on the filter's performance.

What is the difference between S- and P-polarization?

S-polarization (the s stems from the German word senkrecht meaning perpendicular) and P-polarization (the p means parallel) are the two main ways to describe two types of linearly polarized light. A primary misconception when using the terms is assuming that P is always vertical and S is always horizontal. This is not true. P and S are relative to a surface (usually the surface that the light is acting upon and/or reflecting from).

To properly define S- and P- polarizations, we first need to define the term plane of incidence. The plane of incidence is the plane that the incident and exiting beams lie in and is perpendicular to the surface that the light is incident upon.

P-polarization refers to light that is polarized parallel to the plane of incidence.

S-polarization refers to light that is polarized perpendicularly to the plane of incidence.

So saying that P-polarization is always up-down and S is always side-to-side is incorrect. One example where this is incorrect is with a common beamsplitter setup. In a beamsplitter being used where the entrance and exit beams are all parallel to the table top, P will be parallel to the table (side-to-side) and S will be perpendicular to the table (up-down).

The best thing is to keep in mind that S and P are relative to the plane of incidence.

What is the optical difference between N-BK7 and fused silica?

N-BK7 glass is one of the most common and widely used borosilicate crown glasses available. It performs well against most chemical tests, it is relatively hard, and does not scratch easily. N-BK7 glass can be handled without the need for special precautions. The bubble and inclusion content is also very low. N-BK7 has excellent transmission from 350nm to 1.5 µm. It can be a low-cost alternative to fused silica.

Fused silica is another common material used for optics. It has greater transmission than N-BK7 in the UV and IR spectrum. Transmission ranges from 180nm to 2 µm. Fused silica has a low coefficient of thermal expansion, providing stability and resistance to thermal shock over large temperature deviations. Fused silica has increased hardness and resistance to scratching. It can be an excellent alternative to N-BK7 glass, depending on the application.

What is the correct orientation for an Interference Filter?

A good rule of thumb, especially important if there is risk of overheating or solarization, is that the interference filters should always be oriented with the shiniest (metallic) and most nearly colorless side toward the source in the radiant flux. This orientation will minimize thermal load on the absorbing-glass blocking components. Reversing filter orientation will have no effect on filter transmittance near or within the pass band.
Optical Coatings – Interference Filters (PDF).

Will your microscope objectives work with my microscope body?

There are two main properties to keep in mind when choosing microscope components: objective mounting thread and mechanical tube length. CVI Laser Optics standard microscope objectives all have an RMS threaded (0.8 in., 36 TPI) interface. This standard thread is used on many other commercial microscopes. Check the documentation that came with your microscope body.

Our standard visible microscope objectives are designed for a mechanical tube length of 160 mm. The mechanical tube length is the distance between the end of the tube you insert the eyepiece into and the shoulder of the objective. Both the eyepiece and objective should be designed for this spacing to perform at the specified magnification.

What is the difference between standard objectives and infinite-conjugate objectives?

Standard, or finite-conjugate objectives form an intermediate image within the microscope body. Infinite-conjugate objectives do not, therefore they require a tube lens between the objective and the eyepiece to create a viewable image.

What do the numbers on a microscope objective mean?

Most standard microscope objectives will have two sets of numbers in this format:

160 is the mechanical tube length (in mm) for which the objective is designed. For an explanation of mechanical tube length, please see the previous FAQs.

0.17 is the thickness (in mm) of a glass cover slip that the objective is corrected for when being used for examining a biological specimen.

4 is the magnification (in this example, 4×)

0.12 is the numerical aperture (NA) of the objective.

I'm providing my own power to the OEM drive board. What are specs for the necessary power supply and cord?

The recommended power supply is 12VDC, regulated, 3 Amp (providing some "reserve" over the 2.5A max load).

The power connector/cord we use is a Mouser Electronics (Kobicon) #172-4201 ( / tel. 800-346-6873). Ref. Cable Assembly - Mouser 172-4201.pdf (

The connector must be wired with center terminal connected to positive, and the outside shell connected to negative.

I'm using the OEM board with TTL control. What are the proper DIP switch settings?

For direct TTL control of shutter "ON" time, DIP switches DS-1 & DS-2 should be ON. DS-3 should be OFF. On-board timer pot R3 should be set to the minimum value (full CCW). Maintain the TTL pulse as long as required to get desired shutter timing.

For on-board control of shutter "ON" time, all DIP switches should be ON. Initiate the shutter drive with a short TTL pulse (typ. 10-20mS). Set on-board timer pots as needed to get desired shutter timing.

Notes - The shutter will not actuate if DS-2 and DS-3 are both OFF. See Operating Instructions sheet #25164B for more complete information.

When the shutter is closed, is the transmission zero?

For standard (black-coated metal) shutter blades, the transmission is essentially zero.

What is the light power that can safely be incident on the closed shutter without affecting its performance?

Maximum allowable light level will depend on many factors (wavelength, duration, blade material, blade coating, and environmental conditions), generally limited by coating damage and/or warping of shutter blades. Although we do not rate shutters for specific light levels, we can provide sample blades for application-specific testing by customers. Contact Melles Griot Applications Engineers for sample blade arrangements. (Email link

How does the X synchronization work?

When the shutter blades are fully open (or fully closed for a normally open shutter), a dry contact switch is closed, which provides electrical continuity across the X-sync output terminals.

May I use a lower drive voltage (lessDC signal than the recommended 4X rated solenoid voltage to actuate the shutter?

We recommend only using the recommended 4X voltage pulse for 20-30mS. Using any lesser voltage will result in less reliable shutter actuation.

What are the operational specifications for Standard and Ultrathin Electronic Shutters?

Shutters operated within these conditions should function reliably.

Operational Specifications:

Maximum Repetition Rate: 2 Hz Minimum Recharge Time: 200 msec (from start of de-energized condition to start of next actuation) Duty Cycle Factor: max 100% (See Shutter App Not 004 for further information) Service life: >100,000 actuations

Environmental Specifications:

Operating Temperature: -10C to + 40C Humidity: Non-condensing Shock/Vibration Resistance: To be verified by user, within system

What is the laser damage threshold for the shutters blades?

We do not have a documented laser damage threshold for our Spring-Steel Blades with a Teflon-impregnated black matte finish. If this is a concern for your application, CVI Laser Optics and Melles Griot will send you a sample shutter blade for testing.

What types of lenses are best suited to collimate and focus a diode laser?

CVI Laser Optics offers collimating and focusing lenses designed specifically for diode laser wavelengths. The GLC series lenses are designed and optimized for 405 nm and 830 nm, with custom versions available for 375 nm. They can also be used at other diode laser wavelengths and still provide excellent performance. Many of these lenses are diffraction limited: spherical aberration, coma, astigmatism, and sphero-chromatism have been corrected by the design. These lenses are antireflection coated to provide increased performance.
GLC - Collimating and Focusing Lenses for Diode Lasers

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