SU1383161A1 - Method of determining path-length difference of optically anisotropic objects - Google Patents

Abstract

The invention relates to the field of optical instrument making, in particular to the optics of polarization devices and anisotropic media, and can be used in optical technology, analytical chemistry, microelectronics, food and microbiological industry. The purpose of the invention is to increase the accuracy and noise immunity of the measurement. When implementing the method for measuring the path difference of optically anisotropic objects, the wavelength of light from source 1 is scanned within the optical range of iS

Description

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zone using a monochromator 2. The plane of light polarization using a roshon prism 6 is rotated at a constant frequency. The light passing through the object 11 under study is retroreflected with the help of an isotropic reflector 13. With the help of a beam splitter 4, the component of the luminous flux transmitted through the object is selected, the polarization plane 13

which rotates in phase with the plane of polarization of the probing light flux. The signal from the photodetector 17 is filtered with the selection of the fourth harmonic. The wavelength of the probing radiation is recorded at the moment when the minimum amplitude of the fourth harmonic is attained, and the magnitude of the path difference is determined from it. 1 il.

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The invention relates to optical instrument making, in particular to optics of polarization devices and anisotropic media, and can be used in optical technology, analytical chemistry, microelectronics, food and microbiological industry.

The aim of the invention is to increase the accuracy and noise immunity of measurements.

The drawing shows a schematic diagram of the device implementing the method and intended to control the difference in the course of the phase anisotropic plates directly in the process of their manufacture.

The device contains a radiation source 1, a scanning monochromator 2, a condenser 3, a spatial beam splitter 4, a lens 5, a rotating polarization beam splitter 6 like a Rochon prism, a rotary motor 7, a diaphragm 8, a hollow spindle 9 of a surface grinder, a machine drive 10, machined phase plates .11 panshaibu 12 of the machine, an optic reflector in the form of a mirror 13, sprayed onto the outer surface of a glass lap 14, driven by the planet carrier 15, photodetector 16, photodetector (resonant filter 17) f electron zero indicator 18, electron registration unit 19 and current value 20 sensor of the monochromator.

A method for measuring the path difference of optically anisotropic objects is carried out as follows.

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The light radiation of source 1 transmitted through scanning monochromator 2 is concentrated by a capacitor 3 in the central area of spatial beamsplitter 4 formed by the zone of disturbed optical contact between the prisms of beamer 4. Radiation reflected from the central area of beamer 4 is collimated by lens 5 and polarized by a rotating beam splitter driven by the motor 7. The polarization beam splitter 6 is made in the form of a bicontracting prism of the Roche prism type, splitting The incident unpolarized luminous flux to two orthogonally polarized beams, one of which is deflected by the beam splitter 6 from the axis of rotation. The deflected light beam coming out of the splitter 6 is suppressed by the diaphragm 8, and the axially symmetric beam passes through the hollow spindle 9 of the machine, which is driven by the drive 10 and directed to the central phase plate 11, fixed on the optical contact bottom glass faceplate 12 of reflected glass, rigidly connected with the spindle 9 of the machine.

The radiation that has passed through the phase plate is reflected in the opposite direction by an isotropic reflector in the form of a mirror 13 sprayed onto the outer surface of a glass lap 14, which is moved along the block of pasted phase plates by the carrier 15. Retroreflection from mirror 13

The radiation passes through the spindle tube 9 and the polarization beam splitter 6. The components of the reflected radiation, the polarization plane of which is parallel to the polarization plane of the probing radiation, is concentrated by the lens 5 on the central zone of the spatial beam splitter 4, which shields its impact on the photodetector 16, the component of the reflected radiation, orthogonally polarized with respect to probe radiation, deflected by a polarization beam splitter 6 and concentrated by a lens 5 in the peripheral zone l 4 outside the central reflecting platform and fully perceived by the photodetector 16. Since the polarization beam splitter 6 is installed both in the forward and in the reverse course of the rays, it separates from the reflected radiation a component whose polarization plane rotates in phase with the planar t. New polarization of probe radiation. The signal from the photodetector 16 is fed to the input of the resonant selective filter 17, which, in its slit, oscillates at a frequency four times greater than the modulating one, the amplitude of which carries information about the magnitude of the difference in the course of the measured phase plate relative to the wavelength of the probing radiation.

At the moment of equality of the measured path length difference of the probing radiation, the amplitude of the fourth rapMofr NICKY is zero and the zero indicator 18 generates an electron pulse arriving at the counting input of the electronic recording unit 19, the information input KOTOjporo receives information from the sensor 20 of the current value of the wavelength of the scanning monochromator 2. At the time of the pulse from the null indicator, the block 19 fixes the wavelength of the probing radiation, determines the path difference of the fabricated phase plate and an information control system in a process for manufacturing phase plas-

Tink The indicated measurement cycle is periodically repeated with the frequency of the sweep of the spectrum by the monochromator 2. The fabrication of the phase plates terminates when the measured value of the difference in the course of the plates equals the specified one.

The proposed method allows the creation of universal equipment for the production of phase plates for any wavelength, with direct control of their parameters in the manufacturing process without first making a reference of the difference in the path to a given wavelength and the corresponding preparatory changeover of the process equipment. .

Claims (1)

Invention Formula A method for measuring the path difference of optically anisotropic objects, which includes irradiating a test object with a probing polarized luminous flux and photoelectrically recording the linearly polarized component of a luminous flux transmitted through the object, characterized in that, in order to increase the accuracy and interference immunity of the measurement, the wavelength of the probing luminous flux scan within the optical range, and the flatness of its polarization is rotated at a constant frequency that passes through the object under study This retroreflect flow with an isotropic reflector, and prior to photoelectric recording, the component of the transmitted luminous flux, the polarization plane of which rotates in phase with the polarization plane of the probing light flux, is filtered, and after photoelectric recording, the photoelectric signal is filtered with a frequency slit Aw, while registering the wavelength of the probing radiation at the moment when the minimum amplitude of the signal is reached at a frequency of 4.ui. ode object.