Method and apparatus for measuring the spectral absorption in opaque material and method and apparatus for measuring a distribution of microscopic absorption

摘要

For measuring spectral absorption characteristics of an opaque specimen, apparatus of Fig. 4 comprises a variable wavelength laser which can continuously emit monochromatic light over a wide spectral range, a beam converter 11 positioned to convert light from the laser into parallel rays, a beam splitter BS positioned to produce from the beam (i) rectilinear light which strikes a specimen 20 which transmits light, e.g. a dilute suspension or translucent biological specimen, which scatters the light, the forward component of which is combined with the incident light by a half-mirror HM, and (ii) reflected light which passes through a shifter AO where its frequency is slightly changed before being recombined with the forward scattered light in a detector 2 which can be a highly directional detecting system or a heterodyne system, which are further described (Figs. 1 to 3).;For measurement of absorption of a specimen within a scattering medium, the final light path is modified by altering the position of the half-mirror (HM) and of the specimen 21, which is placed behind a sample of the medium NZ, so that the light passing through the medium is reflected by the specimen and again through the medium and then combines with the forward scattered light at the half-mirror and passed to the detector.;Several other arrangements of the components of the apparatus are shown, for measuring various types of specimen which absorb or scatter light, including some which use a Michelson light-receiving system for a reflecting specimen, or a highly directional optical system.;For measuring spectral absorption characteristics of a reflecting specimen when the intensity of the reflection component of incident light is high, the regular reflection component is removed in apparatus (Figs. 10 and 11) by means of a beam trap BT which receives light from the specimen 21 via an angled mirror M5.;Other apparatus can measure either transmission or reflection spectral absorption characteristics in a microsized region (Figs. 12 and 13) and including Cassegrain reflection optical systems disposed confocally and having a pin-hole P at the confocal point, from which the scattered light extracted passes to a detector 2.;Modifications of the apparatus allow a microscopic absorption distribution in an opaque specimen to be measured, by changing the relation between the specimen and the beam of directional parallel light, so as to apply incident light to a very small point region corresponding to a 0-order difraction component (Figs. 15A to 17).;The spectral absorption characteristics of a specimen are thus measured with high accuracy and simply and without picking up extraneous scattered light, and the invention is especially useful for examination of specimens of animal tissue.