Ebert Spectrometers Free of Astigmatism and Coma
TL;DR: In this paper, a ray-tracing computer program has been developed to analyse and design Ebert spectrometers, which are usable over only a narrow spectral range, but special cases were found that are suitable for use as scanning monochromators.
Abstract: A ray-tracing computer programme has been developed to analyse and design Ebert spectrometers. Using this programme the author has found families of spectrometers that have no astigmatism or coma. In general these spectrometers are usable over only a narrow spectral range, but special cases were found that are suitable for use as scanning monochromators. The monochromators are corrected for these aberrations at all wavelengths, but they require auxiliary folding mirrors. The good performance of the monochromators is due to zero incidence angles of the chief ray at both reflections from the spherical mirror.
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TL;DR: Czerny-Turner Spectrographs using Divergent Grating Illumination Optica Acta: International Journal of Optics: Vol 22, No 5, pp 473-475.
Abstract: (1975) Design of Czerny-Turner Spectrographs Using Divergent Grating Illumination Optica Acta: International Journal of Optics: Vol 22, No 5, pp 473-475
20 citations
TL;DR: In this paper, the damped-least-squares method of optimization is applied to the design of holographic concave gratings for the Seya-Namioka monochromator.
Abstract: The damped-least-squares method of optimization is applied to the design of holographic concave gratings for the Seya-Namioka monochromator. The performance of monochromators using such gratings is evaluated in terms of optical transfer function and spot diagram data. The results are compared with those of Noda.
12 citations
TL;DR: Coma compensation in a parabolized Ebert monochromator is studied using the plate diagram and it is shown that two different criteria may be used: narrowest images or symmetrical ones; however, both may not be satisfied simultaneously.
Abstract: Coma compensation in a parabolized Ebert monochromator is studied using the plate diagram. It is shown that two different criteria may be used: narrowest images or symmetrical ones; however, both may not be satisfied simultaneously. Symmetrical or narrowest images may be obtained for an extended range of wavelengths with displacement of at least one of the slits. With fixed slits only incomplete compensation may be obtained.
9 citations
Patent•
20 Dec 2000TL;DR: In this article, thermally compensated optical systems for use in an optical network are disclosed, which include a diffraction grating coupled to a grating mount having a temperature coefficient.
Abstract: Thermally compensated wavelength division demultiplexers and multiplexers are disclosed. In one aspect, thermally compensated optical systems for use in an optical network are disclosed. The systems include a diffraction grating coupled to a grating mount having a temperature coefficient. The systems further include an optical fiber coupled to a fiber mount having a temperature coefficient and a lens assembly coupled to a lens mount. The lens mount is operable to position the lens assembly between the fiber mount and the grating mount and includes a substantially similar temperature coefficient to the fiber mount.
8 citations
14 Apr 2003
TL;DR: In this paper, a miniaturized optical spectrometer module has been developed and realized in polymer by injection molding, which is designed for the visible (VIS, 380 nm-750 nm) and near infrared spectral (NIR, 680 nm-1100 nm) range.
Abstract: A miniaturized optical spectrometer module has been developed and realized in polymer by injection moulding. The spectrometer is designed for the visible (VIS, 380 nm-750 nm) and near infrared spectral (NIR, 680 nm-1100 nm) range. The assembled module has a size of a match box with a spectral resolution (Rayleigh criterion) of <7 nm /10 nm for the visible and <7 nm/8 nm for the near infrared spectrum depending on the pixel width of the used detectors. The stray light has been reduced well below 0.5 % for the VIS-module (VIS: filter OG550, measured at 500 nm) and NIR-module (NIR: filter RG850, measured at 790 nm). To avoid a wavelength shift caused by a thermal expansion of the system, a passive temperature compensation unit is designed. As a result of this the temperature shift between -40 °C and +70 °C can be reduced to <0.03 nm/K. To guarantee a flexible application of the spectrometer the measurement signal is coupled into the spectrometer by a fibre to free-space coupling unit with a 90° beam deflection. In order to use injection moulded components for optical sensors, mould inserts with a high optical quality are required. A toroidal optical mirror with an average surface roughness of Ra<20 nm and a radial shape accuracy as high as 0.2 % (0.1 mm) and optical gratings for the visible and near infrared spectral range with a planarity of 4 μm/cm and an absolute diffraction efficiency as high as 80 % can be fabricated. LIGA-technology, ultra-precision machining and electro-forming processes are applied. All optical elements have been replicated in polycarbonate (PC) with comparable characteristics. The spectrometer set up is based on a modular concept. This enables a high position accuracy of the elements to each other (few tens of μm) and a variation of specification (wavelength and resolution).
2 citations
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TL;DR: In this paper, a spherical mirror, autocollimating plane grating monochromator is described which is compact, stable, and exhibits spectral resolution which is better than 50 percent of the theoretical value.
Abstract: A spherical mirror, autocollimating plane grating monochromator is described which is compact, stable, and exhibits spectral resolution which is better than 50 percent of the theoretical value. The spectrometer is 30 inches long and uses a 3-in. wide grating with 30,000 lines/inch. The optical system, although not in use in any modern spectrometer, was described by Ebert in 1889. The aberration corrective arrangement of the spherical mirror leaves only astigmatism as a serious aberration. The use of curved slits to remove this effect of astigmatism is described.The mechanical-optical system is described in detail, and use of the instrument with a photomultiplier tube to record visible and ultraviolet emission spectra is described. Spectra are presented which demonstrate a second-order spectral resolution of 0.05A in the visible and ultraviolet region.
231 citations
TL;DR: In der Strahlenvereinigung bei den beiden Fallen wird an photographisehen Aufnahmen gezeigt as discussed by the authors, die erste Hohlspiegel in den Strahlngang bringt, dureh den zweiten Hohlstiegel gesteigert oder teilweise rtickgi~ngig gemaeht werden.
Abstract: Bei Spiegelspektrometern kSnnen je naeh der Anordnung des Strahlenganges die Fehler, die der erste Hohlspiegel in den Strahl~ngang bringt, dureh den zweiten Hohlspiegel gesteigert oder teilweise rtickgi~ngig gemaeht werden. Der Untersehied in der Strahlenvereinigung bei den beiden Fallen wird an photographisehen Aufnahmen gezeigt. Viele in der Praxis benutzte Anordnungen entsprechen dem ungiinstigen Falle.
221 citations
TL;DR: In this article, the symmetrical spherical mirror was compared to the unsymmetrical spherical-mirror Czerny-Turner spectrometer using a high blaze grating.
Abstract: Geometrical optic techniques are used to analyze and compare the symmetrical spherical mirror to the unsymmetrical spherical-mirror Czerny–Turner spectrometer. The aberration problems due to diffraction from the grating are analyzed and methods of partial correction of the aberrations are derived. The flux and resolution advantage of gratings with high blaze angles used in the unsymmetrical spherical-mirror Czerny–Turner is shown. A design and ray tracing routine employing a digital computer is utilized to illustrate the geometric effects of the diffraction grating and the partial corrective measures. Slit curvature is analyzed numerically and some general results are abstracted from the numerical data. It may be inferred from the results of theory and numerical calculations that the unsymmetrical Czerny–Turner spectrometer using two spherical mirrors can be made superior to a similar symmetrical Czerny–Turner spectrometer. A comparison of luminosity is made between the Czerny–Turner spectrometer, utilizing a high blaze grating, and various interf erometric and modulating spectrometers and it is shown that the luminosity of the Czerny–Turner spectrometer is comparable or superior.
167 citations
TL;DR: In this article, the results of preliminary tests and calculations showed that the Ebert system is capable of near theoretical resolution at f/6 even when very long slits are used.
Abstract: The previous paper ( Wm. G. Fastie J. Opt. Soc. Am.42, 641 ( 1952)) described a plane grating monochromator optical system which apparently has not been used since Ebert described it in 1889. The high resolution obtained has inspired the design of an f/6 spectrometer of that type for the infrared region. This paper describes the results of preliminary tests and calculations which show that the Ebert system is capable of near theoretical resolution at f/6 even when very long slits are used. Both slits must be curved in order to remove the effect of astigmatism and to avoid wavelength errors at the exit slit which arise from curvature of spectrum when a plane grating is employed. That the same curvature of slits simultaneously corrects these two image errors is a fortunate coincidence which makes the Ebert system appear to be superior to currently employed spectrometer optical systems. Comparison with other systems and discussion of the limitations of the Ebert system are presented.
120 citations
TL;DR: In this article, the analytic theory of aberrations has been used to derive an expression for the magnitude of the coma width of the image in the meridional plane in a Czerny-Turner spectrograph with unequal mirror radii.
Abstract: The analytic theory of aberrations has been used to derive an expression for the magnitude of the coma width of the image in the meridional plane in a Czerny–Turner spectrograph with unequal mirror radii. The calculated properties of a 4-m spectrograph with equal radii and a recently constructed 3.34-m spectrograph with unequal radii are compared with the results obtained by tracing individual rays. The agreement is excellent, in contrast to the results of Chandler [ J. Opt. Soc. Am.58, 895 ( 1968)]. The lateral position of the grating for complete elimination of coma found experimentally with the 3.34-m instrument is in fair agreement with the theory. A correction to the 3 longitudinal grating position is given for a Czerny–Turner spectrograph which results in a flatter focal surface.
77 citations