A multi-slit type spectrometer includes a light diffracter which diffracts an incident light according to wavelengths; an optical shutter array member including a plurality of optical shutter elements arranged in correspondence with wavelength bands diffracted by the light diffracter, operable to transmit an incident ray according to an applied voltage, and made of PLZT. A zone of a given number of adjacent optical shutter elements is applied with a voltage corresponding to the wavelength bands of the rays incident upon the zone of adjacent optical shutter elements at a specified timing so that the rays respectively pass through or are reflected at the optical shutter elements. A signal processor receives the ray which has passed through or has been reflected at each optical shutter element and outputs an electrical signal according to the intensity of the received ray. A calculator calculates the intensity of the incident ray for each wavelength band in accordance with the electrical signal output from the signal processor and the specified applying timing.
Fourier transform spectrometer using a multielement liquid crystal display. A ferroelectric liquid crystal mask is used as an optical encoder for a solid-state Fourier transform spectrometer. A 1.times.64 element array was striped and used as a 1.times.4 element device. The device intersected dispersed radiation and encoded each spectral component thereof with a carrier signal by applying half-wave potentials to each of the four striped (1.times.16) liquid crystal elements which varied the transmitted amplitude of the light from 0.03% to 28% of full scale. The light was spectrally recombined and imaged onto a photomultiplier and the resulting carrier frequencies (and their amplitudes) detected by Fourier transformation of the time-varying signal. Spectra of colored-glass filters were taken to demonstrate the spectrometer.
The invention provides calibrated spectrometers in a multi-spectrometer system, where chemical mechanical polishing endpoint detection is an issue. In one aspect of the invention, a spectrometer is calibrated by selecting a filter slide having a predetermined light transmittance or reflectance variation with location (e.g. angular or linear displacement) on the slide. Light is incident on locations on the filter slide, and this incidence light is either transmitted or reflected. Transmitted or reflected light is received by a spectrometer, and the wavelength measured is compared with the known wavelength that corresponds to its location on the slide. The spectrometer is calibrated by normalizing the wavelength readings obtained at various locations on the slide with the known readings dictated by the reference slide. The spectrometers are also calibrated to a standard light source for intensity of light. During polishing of workpieces, each spectrometer monitors surface spectral data, and converts these via its unique normalization factors to normalized values that are then compared with the normalized stored spectral data from the test piece. Once measured data (after normalization) approaches the endpoint set for the test piece within a predetermined degree of difference the endpoint of CMP has been reached and polishing may be manually or automatically terminated.
A spectrophotometer comprises selection means for selecting one or more of the components of a light beam corresponding to different wavelengths, formed by optical micro-filters.
Apparatus for analyzing light having at least one wavelength, the apparatus comprising: (a) a light deflector for deflecting the light so as to provide a deflected light beam characterized by at least one wavelength-dependent angle, respectively corresponding to the at least one wavelength of the light; (b) an encoder, capable of encoding the deflected light beam so as to provide an encoded light beam characterized by at least one angle-dependent polarization state, respectively corresponding to the at least one wavelength-dependent angle; and (c) a decoder, for decoding the encoded light beam so as to determine at least one spectral component of the light.
An imaging system having a programmable spectral transmission function, that includes an input image plane for passing input imaging light into the imaging system; a dispersive optical system for separating the input imaging light into its corresponding spectral components, thus creating spectrally-dispersed image components along a spectrally-dispersed direction. Also included is a spatial light modulator, having a plurality of operational states, for selecting spectral components for imaging; and having a width along the spectrally-dispersed direction; a de-dispersive optical system for re-combining the selected spectral components for imaging onto a detector array; and means for scanning the input imaging light from an object of interest to generate an output area image.
