OEM spectro Catalogue - Horiba

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10 To illustrate the possibilities of concave aberration corrected grating designs, the figure below shows the performance of a concave aberration corrected grating design compared with that of Czerny-Turner design without astigmatism correction. Here, spot diagrams for an f/2 CP140 aberration corrected spectrograph are compared to those from an equivalent focal length Czerny-Turner spectrograph (“CZT140”, f=140 mm) at f/4. The input slit size in both instruments was set to 0.20 mm (W)x0.5 mm (H). The CP140 optimally images at all wavelengths, whereas the CZT140 produces a very tall image. As the wavelength increases, the degree of astigmatism in the Czerny- Turner design also increases, resulting in a decrease of flux density due to the increasing image height. The fast f/2 CP140 has a much higher light gathering capacity compared to the CZT140 at f/4. Thus the effective flux density of signal from the aberration corrected CP140 is almost 40 times higher than that from the equivalent Czerny-Turner instrument. H1034 scanning spectrometer spot diagrams SPOT DIAGRAM INSTRUMENTAL PROFILE SPOT DIAGRAM INSTRUMENTAL PROFILE l = 250 nm bandpass (FWHM) = 2 nm *TH = 93.1 P.C. dispersion = 6.2 nm/mm *TH : rate of the useful ligth limited by the height of the exit slit (or pixel). CZT140 l = 750 nm bandpass (FWHM) = 2 nm TH = 95.5 P.C. dispersion = 7.2 nm/mm This figure shows spot diagrams of the H1034, 100 millimeter focal length, scanning spectrometer. This instrument uses a 1200 grooves per millimeter concave aberration corrected f/3 grating. The 250 nanometer to 750 nanometer wavelength range is very well corrected for coma, SA, AST and field curvature.
Field curvature (FC) is the shape of the image plane (usually called the Petzval Field). The shape of the field determines the shape of images at the exit. Field curvature can cause calibration errors for off-axis sources and pixel to pixel crosstalk on arrays. Calibration errors and increased blur of off-axis inputs are considered stray light. Aberration corrected gratings can change the shape of the exit focal plane field. Aberration corrected gratings are often called “flat field” gratings. This feature prevents image degradation for off axis images. Designs without this correction often suffer from spatial and spectral resolution losses for off axis inputs. Aberration conclusion review Coma, SA, and FC contribute to near end stray light (light from adjacent wavelengths). Light that does not properly strike the detector decreases the system performance. The signal to noise ratio suffers because of low throughput per pixel and increased pixel to pixel crosstalk. Putting the advantages of efficiency, system light collection capability, system stray light advantages and aberration correction together provides a clear view of the advantages of the holographic concave aberration corrected grating designs. The performance advantages of aberration corrected concave gratings, together with the simple, compact and robust design optimize system performance Technology pushing instrument design In the past three decades detector technology has progressed from film to phototubes to photodiode arrays to charge coupled devices (CCDs). The use of small diameter optical fibers (with high numerical apertures) coupled with new detector technology has made improving imaging performance of existing instruments much more important. Good off axis performance has become necessary as applications using fiber arrays and tall CCD arrays are used together in applications. It is in this area that aberration corrected holographic grating designs have made the biggest impact. Aberrations such as coma, spherical aberration, astigmatism and field curvature make point to point imaging a difficult challenge. Commercially available instruments are designed as all-purpose instruments. They must adapt to applications that work well in the UV through the far infrared in scanning and image modes. For dedicated industrial applications, a more specific design can lead to an instrument that outperforms the all-purpose, one size fits all, instrument design. For those users with dedicated, repetitive applications (as with most OEM grating customers), spectrometers with concave gratings are the obvious choice. Another advantage of aberration correction gratings well worth mentioning is the ability to correct for aberrations in other parts of the optical system. Other system aberrations (e.g., aberrations from lenses, mirrors or sample-related problems) can be corrected with an appropriate grating design. The concave aberration corrected grating design can incorporate the required corrections for system coma, spherical aberration, astigmatism and field curvature. This system design approach can improve resolution and spatial imaging. Design success will often depend on achieving the optimal coupling of all system components. Aberration corrected holographic grating designs are used in many industrial systems to optimize throughput while reducing noise. 11
Page 1 and 2: Gratings and OEM Division general s
Page 3 and 4: Introduction As a pioneer and world
Page 5 and 6: Spectrometers for OEM applications
Page 7 and 8: System light collection capability
Page 9: Spherical aberration (SA) Spherical
Page 13 and 14: Existing proof of concept systems T
Page 15 and 16: VS70-M The VS70-M is a plug and pla
Page 17 and 18: VS140-M The VS140-M is a plug and p
Page 19 and 20: Modular spectroscopy components a s
Page 21 and 22: Slits and optional CMOS or NMOS det
Page 23 and 24: Input: The VS spectrographs can acc
Page 25 and 26: Drive Electronics: These detectors
Page 27 and 28: Imaging compact spectrographs This
Page 29 and 30: Spectrometer comparaison chart comp
Page 31 and 32: H10-34B OEM imaging monochromator B
Page 33 and 34: 70 60 50 40 30 20 10 0 190 240 290
Page 35 and 36: Technical information Before introd
Page 37 and 38: Note that the lower the dispersion
Page 39 and 40: Projection of the grating width on
Page 41 and 42: G= � � d²G area of the source
Page 43 and 44: Information request form If you hav
Page 45 and 46: Fax form For more information or cu
Page 47 and 48: and product lines HORIBA Jobin Yvon

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