Optical Testing


The newest addition to our list of unique capabilities is DTB’s optical testing laboratory. This laboratory is able to measure Photometry and Radiometry of light and with light of a given object or source.


Every object affects or interprets light differently, so appropriate and accurate measurements are needed to determine how much light is being produced by a source or cast upon an object. This can be measured with respect to power requirements and also how the human eye interprets that light.


Some of the optical photometric properties and optometric proportion we measure are:


Optical Photometric Properties Optometric Properties

  • Haze

  • Transmittance

  • Optical Distortion

  • Optical Deviation

  • Optical Density

  • Prismatic Deviation

  • Spherical and Cylindrical Power

DTB’s new light analyzer is an integrated system designed to measure not only weighted and un-weighted photometric parameters such as total transmittance, but also haze with respect to both A and C illuminants. Our system is not limited to photometric measurements, but also can measure the radiometric power aspects of the item of interest as well.


Optical Testing: Light Analyzer for Luminous Transmittance and Haze

Light Analyzer for Luminous Transmittance and Haze


To measure the illuminance/luminance and radiance/irradiance of an object our new optometer can be employed to take information from multiple photometric or radiometric detectors across the surface of an object.


DTB can test in accordance with many specifications such as, ASTMD1003 for transmittance and haze, ASTMF 2156 for optical distortion or any other requirements you may have such as ATPD 2352. Our optical testing lab has worked with a vast amount of products such as transparent armor, night vision goggles and laser visors.


Relevant Optical Specs:



  • Luminous Transmittance per: ASTM-D-1003, ATPD 2352 4.4.1, PMA202-07001, MIL-DTL-62420, ASTM F659, ANSI/SAE Z26.1, ASTM F1915

    • Photopic , Scotopic and Night Vision Goggle response functions

    • Standardized light sources A and C

  • Haze per: ASTM-D-1003, ATPD 2352 4.4.1 and PMA202-07001, ASTM F659, ANSI-SAE Z26.1

    • Taber Surface Abrasion testing for interior and exterior (threat surface) wear, per ATPD 2352 4.3.6, ANSI-SAE Z26.1 and ASTM D 1044

  • Optical Density per: PMA202-07001,MIL-DTL-62420, MIL STD 11352H

  • Optical Deviation per: ATPD 4.4.3, ASTM F801, MIL-DTL-62420

  • Optical Distortion per: ATPD 2352 4.4.4, ASTM D2156

  • Prismatic deviation per: PMA202-07001, ASTM F659

  • Spherical & Cylindrical Power per: PMA202-07001, ASTM F659, MIL-DTL-62420


A2LA Coverage:



  • Optical Testing

    • PASTM F801-96; ASTM F2156-06; ASTM D1003-00; ASTM D1044-08; ATPD 2352R Sections 4.4.1, 4.4.1.1, 4.4.2, 4.4.3, 4.4.4

  • Abrasion

    • ANSI/SAE Z26.1.1-1996, Sections 5.17 and 5.18; ATPD 2352R, Sections 3.3.6 and 4.3.6

      Optical Testing: Abraiser for Abrasion testing

      Abraiser



      Optical Testing: Abrasion Sample

      Abrasion Sample



The following are some of the optical testing applications we perform:




  • Display monitors

  • Periscopes

  • Night Vision goggles

  • Laser Visor


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Characterization of Light Sources


Often there is a research need to characterize the photometric profile of light sources and to that end some useful photometric measurements that Dayton T. Brown, Inc., can provide to measure these light sources are explained in this outline.


Light sources can be characterized according to their wavelength spectrum as either narrow or broad-banded. For example, atomic resonance lamps such as sodium or mercury emit light only at certain wavelengths.


The spectral bandwidth of the light at each atomic line is generally very narrow. Lasers, of course, are effectively monochromatic (i.e. single wavelength). Conversely, arc lamps such as xenon, carbon arc and incandescent lamps emit over a very broad wavelength range with a few spectral features.


One useful measurement of light sources is Luminous Intensity or Candela (cd = lm/sr).


The candela is the foundation unit for the measurement of visible light. The candela is the luminous intensity, in a given direction of a source that emits light that has a wavelength of approximately 555 nm (yellowish-green) and that has a radiant intensity in that direction of 1/683 watt per steradian.


The candela value is independent of distance. One can think of it as the emission from the lamp without the interest in what happens to the photons it has ejected. The candela is frequently used when dealing with focused light for LEDs, flashlights or spots.


Typical Candela values:
110 cd Light Bulb
Up to 106cd Xenon Head light
1 – 300 mcd LED (10mA)
5.6 cd White LED (20mA)

Another example, Illuminance (Lux, lm/m2), is the total luminous flux which falls on a surface and it shows the intensity of the incident light. The value is affected by the wavelength of the emitted light and the distance between the light source and the illuminated area.


The human eye is most sensitive to light that has a wavelength of around 550nm (yellowish-green) and thus an amber light source will have more Lux than a blue one, as an example. This is called the luminosity function.


The larger the distance between the light source and the illuminated area the lower the illuminance will be. Below we show some examples of illuminance for certain activities:


Typical illuminance values:
1 lx Full Moon
10 lx Street Lighting
100-1,000 lx Workspace Lighting
10,000 lx Surgery Lighting
100,000 lx Plain Sunshine

Luminance (L) is another useful measurement of light sources. It is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle. The SI unit for luminance is candela/meter2 (cd/m2).


A non-SI term for the same unit is the "nit". (Nit is believed to come from the Latin nitere, to shine). Luminance is occasionally referred to as ‘photometric brightness’ of a light source.


Luminance is frequently used when dealing with LEDs, flashlights or spots, video displays and aircraft cockpit lighting.


Typical luminance values:
1.6 * 109 cd/m² Solar Disk At Noon (Don't Look!)
600,000 cd/m² Solar Disk At Horizon
120,000 cd/m² Frosted Bulb 60 W
11,000 cd/m² T8 Cool White Fluorescent
8,000 cd/m² Average Clear Sky
2,500 cd/m² Moon Surface
2,000 cd/m² Average Cloudy Sky
30 cd/m² Green Electroluminescent Source
0.0004 cd/m² Darkest Sky

Dayton T. Brown, Inc. can provide these measurements and stands ready to assist you in your photometric testing and evaluation needs.



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Laser Eye Protection Testing


Dayton T. Brown, Inc. has wide ranging experience in the propagation and measurement of electromagnetic radiation in the visible, infrared and ultraviolet regions.


We maintain a particular interest and capacity with respect to laser eye protection.


Our capabilities include the measurement and evaluation of laser eye protection for helmet mounted displays, night vision goggles and Integrated Modular Helmets in accordance with the latest military specifications in the visible, near infrared and infrared regions.


Optical Testing: Lens Analyzer

Lens Analyzer for Optometric Properties


In additional to this proficiency we also maintain facilities and equipment necessary to evaluate photometric attributes of light.


We retain the expertise to evaluate displays and light sources for Chromaticity, Luminous Intensity, Luminance, Illuminance, Spectral Response and Contrast Ratios.


You may also be interested in our Safety and Survival Testing.



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