Input Optics

Light 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.

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.


Part Number Description Specifications
A1490LP Quartz Rod Light Pipe 4" long with a .217" OD .196" ID, for remote access to hard to reach sources. Requires MPS1692#6XD and 6-32 set screw to mount onto SED(SEL) detectors (Sold separately).
Note: Also useful for lamp testing of encased endoscopy light sources with optional A0101 (wolf dynamics), A0102 (ACMI) and A0103 (Olympus) light source adapters also sold separately.
A1490-K Endoscope Adapter Kit Accessory kit for endoscopy light source testing includes: A1490LP Light pipe, mounting ring MPS1692#6XD with 6-32 set screw, and light source adapters A0101 Wolf/Dyonics, A0102 ACMI, and A0103 Olympus. ILT detector and calibration sold separately.
A310 Filter Mounting Ring Mounts filters 25 mm dia., up to 7 mm thick, has 1 ¼"-24 threads
A311 Filter Mounting Ring Mounts filters 25 mm dia., up to 4 mm thick, has 1 ¼"-24 threads
A312 Opal Diffuser Opal Diffuser, Mounted in A310 Ring
A313 Flat Quartz Diffuser Flat Quartz Diffuser, Mounted in A311 Ring
AT Attenuator cap, X10 Provides X10 attenuation. No threads, slides onto end of detector
FFO12 Rigid Fiber, 12" Long 3/8” Stainless steel tubing over a 600 micron. 300 dec C rated, fiber optic with SMA905 adapters, .22 NA.
FFO12/RAA5 Right Angle Mocro Probe 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)


Light Guide, UV Quartz

2 mm diameter bundled fiber optic to transmit UV radiation , 1.5 meter-long-56x200/220/245 LSHOH is water proof and withstands high temperature (up to 200 deg C)


Light Guide, UV Quartz

2 mm diameter bundled fiber optic to transmit UV radiation, 1.5 Foot-long-Bundle-0.5m-56x200/220/245 LSHOH is water proof and withstands high temperature (up to 200 deg C) Replaced FFO2500


Fiber Optic Light Guide

22 fiber bundle LSOH, 0.5 meter-long water proof fiber optic with PVC monocoil jacket and SMA connectors


Light Guide, UV Quartz

Light Guide, UV Quartz Solid Core  2.0 meter-long -1000 um (1mm)

FSD2 Diffuser, Fused Silica Combines any UV-VIS filter with Fused Silica Diffuser in one ring for extra sensitivity and excellent spatial response.
H Hood 62.5 mm long x 42 mm dia. barrel, internally baffled to reduce stray light and field of view. Accepts standard input optics and filters.
HNK15 Laser Adapter H Hood, N Adapter and K15 Cone assembly for laser power measurements. 15 mm diameter input aperture with uniform response.
INS125 Integrating Sphere, 5" Designed as a powerful accessory to the ILT950, ILT1400 and ILT1700 light measurement tools. Allows total flux measurements of LED's, small lamps, low power lasers, fiberoptic guides and collimated beams of light.  The removable port adapter also allows calibration and readout in absolute irradiance with excellent cosine correction.  Unit is configured with 2, 20 mm diameter ports and one 40 mm diameter port for maximum versatility. System includes, wrench, 5 inch sphere, 1 detector port adapter and 3 removable port covers. Port covers are painted with the same reflectance material as the sphere to assure maximum performance and also can be used as a reflectance standard. (Calibration sold separately)
NOTE: 12" (opens), 10", 2" diameter spheres also available.
INS250N Integrating Sphere, 10" 250 mm diameter sphere in cubical housing, includes two port plugs, power supply, and YIN Calibrated miniature lamp.
NOTE: 12" (opens), 5", 2" diameter spheres also available.
Click for INS250N Manual (PDF)
K15 Cone 15 mm aperture and targeting aid.
K9 Cone 9 mm aperture and targeting aid.
L30-1 High Gain 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)
LED LED Intensity Barrel For measuring beam intensity of LEDs when used with ILT SED sensors. The LED barrel has a removable 9.27 mm dia aperture to allow measurement of both mounted and through hole LED's.  Click on link to see drawing. (component change 6/2017, increased aperture from 4 mm to 9 mm)
P2 Adapter, 4.3 mm I.D. sleeve 4.3 mm I.D., Adapts fiber optic cables to female 1 ¼"-24 threads on SED(SEL)(SHD)(SL) Detectors
P6 Adapter, 12.5 mm 12.5 mm I.D.CR149 adaptor with female 1 ¼" -24 threads.
P6/SMA Adapter, SMA905 P6 Adapter with SMA905 coupling.
P8 Adapter, 8.30 mm I.D. 8.30 mm I.D., Adapts RAMP to female 1 ¼"-24 threads on SED(SEL)(SHD)(SL) Detectors.
P9 Adapter, 9.2 mm I.D. 9.2 mm I.D.,Adapts PIN to female 1 ¼"-24 threads on SED(SEL)(SHD)(SL) Detectors.
P12 A1490 Light Pipe Adapter For mounting A1490 onto ILT detectors.
PIN4 Luminance Probe Solid 1000 µm, .22NA fiberoptic light guide in protective metal tube for remote end-on viewing. Requires P6/SMA adapter to mount to ILT detectors and luminance calibration for contact luminance measurements in cd/m2 or fL. (custom lengths available)
R Barrel For use with SED(SEL) detectors to produce an average field of view of +/-0.75 degree (1.5 degree total) for radiance/luminance measurement of extended sources.
RAA4 Right Angle Adapter Right-Angle Cosine Adapter permits measurement of light sources 90º to the fiber normal. Sold with weighted screw-on handle for more stable detector placement when needed. Calibration required (sold separately)
RAA5 Mini Right Angle Diffuser Miniature diffuser with teflon window and SMA905 connector measures .85 L x .46 W x.47 H inches.
RAMP12 Microprobe / 12 Inches Obsolete. Replaced by FFO12/RAA5 Right Angle Micro Probe.
T Diffuser Used in addition to the W for improved cosine response, especially with thin film filters. For spectral ranges 250- 700 nm.
T1MM Diffuser / Aperture 1 mm Teflon diffuser mounted in filter ring with 1 mm diameter aperture for contact irradiance
T2X Diffuser Combines any UV-Vis filter with T Teflon Diffuser in one ring for extra sensitivity and excellent spatial response.
TD Diffuser Domed teflon diffuser for use with ILT detectors for spectral ranges 250- 700 nm.
W Diffuser Internal hemisphere of solid quartz for use with ILT detectors for cosine response from 200-2100 nm.
W2 Quartz Cosine Receptor RPS900 series quartz cosine receptor for superior cosine response
W4 Mini Cosine Correcting Diffuser Miniature cosine correcting diffuser with 6.35 mm OD and ~10.92 mm length. Screws onto ILT fiber optic with standard SMA connecter for applications requiring improved spatial response.