Light Measurement Input Optics

detector opticsLight measurement units are defined around very specific spatial responses. A carefully designed input optics system is essential if measurement accuracy is to be achieved.
 


Two laws of geometrical optics apply directly to radiometry and photometry: the inverse square law and the cosine law.


The inverse square law defines the relationship between irradiance from a point source and the distance to the measurement surface. It states that the intensity per unit area varies in inverse proportion to the square of the distance between the source and surface.


In other words, if you measure 16 W/cm² at 1 meter, you will measure 4 W/cm² at 2 meters, and can calculate the irradiance at any other distance. A well defined measurement plane and approximate point source are required for valid interpolations.


In radiance measurements (W/cm²/sr), where a detector with a narrow viewing angle looks at a much larger, uniform area source, the area of the source that the detector sees increases as the detector moves farther away, counteracting the effects of the inverse square law and making the reading independent of distance.
 

Integrating sphere

Radiance measurements are useful for characterizing large area sources such as CRT's and backlit displays, or for diffuse, uniformly illuminated surfaces.


The cosine law refers to the relationship between the irradiance on a surface and the incident angle. The intensity falls off in proportion to the cosine of the reflected angle, since the effective surface area is reduced as the angle increases.


Irradiance and Illuminance detectors, especially those with filters that restrict off-angle light, require cosine correction to properly quantify light coming from all angles. Inaccurate cosine response is one of the biggest sources of error in full immersion applications.


There are many applications in light measurement that require specialized input optics. For example, intense laser beams must be diffused so that the narrow beam does not locally saturate the receiver. Many high intensity ultraviolet sources require temperature resistant remote optics that offer cosine spatial responses and side viewing.

Use the table below to browse our standard input optic offerings.  If you have questions about any of our optics, need assistance selecting the right optic for your application, inquiring about pricing, or are looking for a customized solution, please contact using the button below.
 

 

                                                                  
 

Image Part Number Specifications
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Diffusers

Diffusers are used to improve the spacial response of detectors with the goal of creating a cosine corrected response.

W Quartz (1.024" dia) Wide eye diffuser with internal dome, 200 - 2100 nm, 42 mm diameter OD
WU ^W diffuser with sealant and orings to allow submersion in liquids. 42 mm diameter OD
TD Teflon (21.5 mm dia) Dome diffuser 200 - 700 nm, 42 mm diameter OD
  QT Teflon (.43” dia.)diffuser with protective quartz window 200-700 nm, 42 mm diameter OD
QT-#mm ^QT diffuser with aperture to measure smaller light spots. Available with 1, 3, 5 or 7 mm apertures, 200-700 nm
A313 Quartz (.43" dia) flat multi-layer diffuser, 200 - 2100 nm, 42 mm diameter OD
A313-#mm ^A313 diffuser with aperture to measure smaller light spots. Available with  1,3,5 or 7 mm apertures, 200-2100 nm
T Teflon (.5" dia) diffuser in threaded filter ring.  Has mating threads on both sides to allow additional optical components to attach.  42 mm diameter OD
RAA4* Right-Angle Adapter/Diffuser (.27" dia) with mini integrating sphere .61" dia x .44" tall
  RAA4X* Right Angle Adapter /Diffuser (.27” dia )with x10 attenuation, mini integrating sphere .61” dia by .44” tall
RAA5* Mini Right Angle Adapter/Diffuser (.25" dia) with internal integrating sphere (.46 x .47 x .84")
A2* Silica chips in a filter ring to be combined with W or WU for use on Fiber optics  (requires MPS2354P2XD  to connect to fiber)
W5E* Miniature cosine correcting diffuser with 6.35 mm OD and ~10.92 mm length. Threads directly on to SMA905 fiber
  *designed for connection to SMA905 fiber optics/patch cords

Laser Power Adapters

Used for testing small spots of light and or collimated beams

HNK15 Narrow beam adapter, eliminates alignment errors.  15 mm opening
K15 15 mm aperture and targeting aid
K9 9 mm aperture and targeting aid

Fiber Optics / Patch Cords

Light guides used to connect input optics to sensors/spectrometers with SMA905-SMA905 adapters (unless otherwise noted.) . The tip of the fiber can also be used as an input optic receiving light based on the numerical aperture.

FFO600SC 1m 600µm solid core, low solar, Fiber, Patchcord, Kevlar Jacket
FFO600FCPC 1m 600µm solid core, low solar, Fiber, Patchcord, Kevlar Jacket.   FCPC to SMA905.
  FFO600SCW-3 Fiber, Kevlar jacket, 3m 600um Solid, submersible, detachable
  FFOSMA2UV1000 SMA2/UV1000/1100N/SQLK6.0mm/2  Fiber Optic, UV 1000/1100 nm
  FFO400UVIR Fiber, 400um, SMA905, BX, 1m  250-2500 nm
  FFO2501 Bndl-0.5m-56x200/220/245 LSHOH sealed at both ends for water immersion; 200 deg C max operating temperature
FFO12-S Solid Tubing, rated 300 deg C Fiber Optic, Rigid, 12" L
FFO18-S Solid Tubing, Rated 300 deg C Fiber Optic, Rigid,18" L
P11-2 Fiber, 600 micron LSHOH, 1.97"
P11-4 Fiber, 600 micron LSHOH, 3.97"
PIN4 Contact Luminance Probe Solid 1000 um, .22NA fiber optic light guide in protective metal tube for remote end-on viewing (SMA905 - Ferrule tip).  Requires P6/SMA adapter to mount to ILT detectors and luminance calibration for contact luminance measurements in cd/m2 or fL.  (Custom lengths available)

Filter Rings

Used to mount customers filters to ILT light sensors and spectrometers

A310 Mounts filters 25 mm dia., up to 7 mm thick, has 1 ¼"-24 threads
A311 Mounts filters 25 mm dia., up to 4 mm thick, has 1 ¼"-24 threads
  MPS235600XD Mounts filters 12.7 mm dia., up to 4 mm thick, has 1 ¼"-24 threads
  MPS235500XD Mounts filters 12.7 mm dia., up to 7 mm thick, has 1 ¼"-24 threads

Right Angle Probe

Used to access light in hard to reach/hostile environments. Withstands exposure to high temperatures and intense UV.

  RAMP12 Right Angle Mocro Probe FFO12/RAA5.  High temperature right angle probe for insertion into harsh environments or remote locations.  Withstands temperatures up to 300 deg C.  Connects to ILT spectrometers and SED(SEL) version detectors with SMA905 adapters.  (P6/SMA sold separately)
  RAMP18 Right Angle Mocro Probe  FFO18/RAA5  High temperature right angle probe for insertion in harsh environments or remote locations. Withstands Temperatures up to 300 Deg C. Connects to ILT spectrometers and SED(SEL) version detectors with SMA905 adapters. (P6/SMA sold separately) 

Hoods

Ambient light blocking adapters /occlusion hoods

H Hood, internally baffled to reduce stray light and field of view.  Accepts standard input optics and filters.  Best for distance 25' or less
  LED LED intensity barrel with baffles and removable aperture.  Used to set distance, block ambient light, and minimize internal reflections for beam CD measurement on small light sources

Lenses

Lenses are often used to create a narrow field of view for luminance/radiance measurements

L30-1 High Gains Lens increases detector sensitivity while limiting acceptance angle for visible and near IR applications.  For effective intensity of flash sources at a distance greater than 25 feet.  (L30-1 must be used with 1 or 2 filters or empty filter rings to assure the lens is at the correct distance from the sensor)
R Radiance/luminance lens produce an average field of view of +/- 0.75 degree (1.5 degree total) for radiance/luminance measurement of extended sources
  R1.7 Radiance/luminace lens use to create 1.7 MRAD 
  R11 Radiance/luminace lens use to create 11 MRAD
R2* Radiance/luminace lens produce an average field of view of 2 degrees, for radiance/luminance measurement of extended sources
R3* Small Spot, fixed (500 mm) distance radiance/luminance lens 
  * indicates for use with a fiber optic/patch cord with SMA905 adapter

Adapters

Can be used for alignment, as apertures  or for connection of fiber optic light guides

P2 Adapter, 4.3 mm I.D.
P6 Adapter, 12.5 mm
  P6/SMA* Adapter, SMA905 connection
  * indicates for use with a fiber optic/patch cord with SMA905 adapter

Apertures

Used to reduce a sensor surface area to allow irradiance measurement of small spot of light. Can also be used in place of, or along with neutral density filters to allow measurement of more intense light sources.  Apertures can be sold alone, Mounted in a filter ring or combined with filters and optics

  1 mm-7 mm  SHM30727P## apertures with openings 1, 2, 3, 3.2, 4.3, 5 and 7 mm

Integrating spheres

Integrating spheres are used to capture the light coming from a source in all directions to allow measurements of total flux (Watts/Lumens)

INS50* Integrating Sphere, 2" , .276 “ input port plus  1 SMA905 port to attach fiber optic
INS125 Integrating sphere, 5" three port - two 20 mm, one 40 mm dia. 
INS250N Integrating sphere, 10", three port - two 20 mm, one 40 mm dia.  Includes built-in calibrated lamp.
  * indicates for use with a fiber optic/patch cord with SMA905 adapter