1OL 750 Diffuse Spectral Reflectance Measurement System Optronic Laboratories, Inc.
2About Optronic Laboratories, Inc. In 1998, Optronic Laboratories, Inc. moved into its new 25,000 square foot purpose-built facility, consolidating and expanding production, R & D and calibration facilities.
3The OL Series 750 Monochromators The heart of any spectroradiometric system is the monochromator, but…It must give the right bandpasses –Too large and spectra are distortedToo small and signals are lowIt must give high spectral purity (low stray light) so only the wavelength of interest is detected.
4The OL Series 750 Monochromators Available in single and double (shown) versionsF/4 optics for high throughputVery low stray lightNumerous special features for most accurate results
5The OL Series 750 Monochromators Large range of gratings availableOptimised for high efficiencyOptimised for wide wavelength rangeOptimised for high resolutionTri-grating mounts change gratings automatically
6The OL Series 750 Monochromators Range of Plug-in input accessoriesChoppers (shown) for IR detectorsAutomatic control of chopper speed and “open” position stopFilter-wheel for input attenuation or filteringVersatile plug-in chopper or filter wheel input accessories
7The OL Series 750 Monochromators Fully automated 11 position blocking-filter wheelIncludes SHUT position for dark current readingsOptimised filters for widest wavelength rangeBlocking-filter wheel changes filters automatically
8The OL Series 750 Monochromators Blocking filters:how they workGratings diffract light at different angles depending on wavelength400nm will also diffract at the same angle as 800nm (since 2 x 400 = 800)A blocking filter removes the 400nm so just 800nm is leftBlocking filter400nm + 800nm400nm800nmgrating
9The OL Series 750 Monochromators Light passes into the monochromator through the entrance slit, then onto the first collimating mirror.
10The OL Series 750 Monochromators Collimated (parallel) light is directed onto the grating.
11The OL Series 750 Monochromators The grating diffracts the light, sending each wavelength off at a different angle.The desired wavelength is collected by the first focussing mirror….
12The OL Series 750 Monochromators …which focuses it at the middle slit.A second collimating mirror collects this beam…
13The OL Series 750 Monochromators …and collimates it onto a second grating.Since the second grating is linked to the first, they are at the same angle and hence the same wavelength.
14The OL Series 750 Monochromators This second grating acts like the first, but the spectral purity is increased by many decades.
15The OL Series 750 Monochromators The pure monochromatic light, at the wavelength desired, is then focussed onto the exit slit and emerges from the monochromator.
16The OL Series 740-20 Light Sources For transmission, reflection and detector response measurements, a light source at the entrance of the OL 750 creates monochromatic light at the exit.The OL Series is an ideal light source for most applications.
17The OL Series 740-20 Light Sources Single and double lamp versionsUV lamp200nm to 400nmTungsten lamp250nm to 2500nmGlowbar1000nm to 30000nm
18The OL Series 740-20 Light Sources Optics match the OL Series 750 MonochromatorsEasy switching from one source …
19The OL Series 740-20 Light Sources Optics match the OL series 750 monochromatorsEasy switching from one source ……to the otherFully automated switching available
20The OL 750 + OL 740-20 200 to 30,000 nm coverage monochromatic light prevents sample heatingSuits a very wide range of standard OL accessoriesSuits many existing and future applications
21Reflectance Measurements Reflectance can be specular (like a mirror) or diffuse (like paper).Optronic Laboratories, Inc. manufactures a wide range of accessories for regular and diffuse transmittance.
22Diffuse ReflectanceOptronic Laboratories, Inc. manufactures a range of fixed-angle and Edward spheres for diffuse reflectance measurements.To illustrate a diffuse reflectance measurement system, we will use the OL Diffuse Reflectance Attachment.
23Diffuse ReflectanceDiffuse reflectance is measured against a standard.A scan is run with the standard, then another with the sample.SampleStandard
24Diffuse ReflectanceCAUTION:Change in throughputDO NOT USEFrom a simple viewpoint, the ratio of these scans would indicate the sample reflectance.However, the throughput of the sphere changes due to the sample.Sample
25Diffuse Reflectance Instead, the double beam method should be used. This involves 4 scans, three to calibrate and one to measure.Scan 2Scan 4Scan 3Scan 1SampleStandard
26Diffuse ReflectanceThe scans with the beam directed at the wall of the sphere correct for the throughput changes.The true reflectance can then be calculated.Scan 4Scan 2StandardSample
27The OL SeriesUses the double beam method for accurate values of reflectanceSoftware guides the user through the calibration and measurementBeam switch mirrorStandard or sample
28The OL Series 740-70 2 versions of the OL 740-70 are available PTFE sphere coating for 250nm to 2,500nmGold sphere coating for 1,000nm to 30,000nmStandard or sample
29The OL 750 + OL 740-20 + OL 740-70 If we put these together… And add a detectorPositive location&Easy assembly
30The OL OL OL...we have a complete system for diffuse reflectance.The light-trap supplied also allows measurements which exclude specular reflections.
31More InformationThe systems illustrated represent just a few of the accessories from Optronic Laboratories, Inc.For more information:Contact your local Optronic Laboratories’ representativeVisit our website at