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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.

Input Optics
Part Number Description Specifications
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

FFOSMA2UV1000

Light Guide, UV Quartz

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

FFO1857-1.5

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)

FFO2501

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

FFO2755P1XA

Fiber Optic Light Guide

22 fiber bundle LSOH, 0.5 meter-long water proof fiber optic with PVC monocoil jacket and SMA connectors
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.
K9 Cone 9 mm aperture and targeting aid.
K15 Cone 15 mm aperture and targeting aid.
INS250 Integrating Sphere, 10" 250 mm diameter sphere in cubical housing, includes two port plugs, and YIN Calibrated miniature lamp.

Click for INS250 Manual (PDF)
L30 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.
LED Barrel LED Adapter with baffles, painted flat internally and assembled for luminous/radia.nt intensity measurement of LED's, 4.3 mm dia. aperture. Dimensions: 134 mm x 42 mm diameter
N Adapter Quartz diffuser with reflective coating
P1 1 mm dia. aperture 1 mm I.D. aperture with 1 ¼"-24, used for limiting input area.
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.
PIN Probe Single quartz fiber housed in 1.5 mm diameter x 152 mm long stainless steel tube for remote end-on viewing. Custom lengths available. Requires P9 adapter.
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.
RAA Right Angle Adapter Input adapter for fiber optic probes includes a W Wide Eye diffuser for cosine response. Dimensions: 32 mm dia. x 25 mm high.
RAMP12 Microprobe / 12 Inches 5 x 5 mm square chrome plated tube encasing a UV transmitting quartz fiber light guide with right angle acceptor. Requires P8 Adapter.
RAMP18 Microprobe / 18 Inches 5 x 5 mm square chrome plated tube encasing a UV transmitting quartz fiber light guide with right angle acceptor. Requires P8 Adapter.
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 IL detectors for spectral ranges 250- 700 nm.
W Diffuser Internal hemisphere of solid quartz for use with IL detectors for cosine response from 200-2100 nm.
W2 Quartz Cosine Receptor RPS900 series quartz cosine receptor for superior cosine response
YK113 CIE 127 Input Optic photopic filter and input optic designed for CIE 127 condition A and condition B LED measurements.