SU1254428A1 - Device for measuring holographic characteristics of photoregistering mediums - Google Patents

Abstract

The invention relates to devices for measuring the holographic characteristics of photo-recording media. The core of the invention is to increase productivity and accuracy of measurements. The goal is achieved by introducing a imaging lens, parallel transfer prisms located in the signal channel between the attenuator and the knife filter. In addition, an electronic scheme for multiplying, amplifying and detecting photodetector signals, a photodiode and a video amplifier, a reference hologram and a telescopic system with a point flap, as well as a dual two-position switch were introduced into the readout system. The input window of the exposure photodetector is located on the axis of the zero order of the diffraction of the beam reconstructed from a hologram lens. The reference hologram is displaceable in a plane in front of the cassette. The telescopic system is located behind the cassette along the axis of the reference channel. The point flap is arranged to move in the image plane of the reference source of the holographic scheme. The electronic circuit for multiplying, amplifying and detecting photodetector signals consists of mixers, a local oscillator, a synchronous detector, a total radio frequency signal amplifier, an intermediate frequency amplifier of light beats, and an intermediate frequency amplifier. The output of the local oscillator is connected to the input of the first mixer, the output of which is connected to the amplifier of the total radio frequency signals, the outputs of the amplifiers of the signals of the total radio frequency and the frequency of light beats are connected to the inputs of the second mixer. . 1 silt, y (L

Description

The invention relates to holography and sensitometry of photo-recording media and can be used to select and control exposure modes and processing of recording media for holographic recording of information, as well as for research related to their development.

The purpose of the invention is to improve the performance and accuracy of measurements.

The drawing shows a diagram of the device.

The device consists of a light source 1 - a laser, a holographic circuit (elements) of a test hologram recording and an optical readout circuit (optical elements 19-30), two dual-channel photodetectors — a diffraction (31-32) and an exposure (33-34) electronic circuit of multiplication , amplification and detection of signals - photodetectors (35-44), an optoelectronic illumination circuit (45-46), an electronic oscilloscope 47 and a control unit 48.

The holographic scheme consists of two channels — a reference (3–8) and a signal (9–17) optically diverging from the laser splitter 2 and converging in the frame of the holder (cassette) of the studied Fed 18, in which house there are sequentially located on the optical axis, the shutter 3 (9), swivel mirror 4 (10), attenuator 5 (11), knife filter 6 (14), micro-lens 7 (15), diaphragm 8 (16) with a pinhole. In the signal channel, two parallel prisms 12 and 13 of parallel transfer (periscopic system) are inserted, located between the loosener 11 and the knife filter 14, and displaying the lens 17.

The optical readout circuit consists of a heterodyne ray coupler 19 located on the axis of the holographic reference channel between the splitter 2 and the shutter 3, along the axis of the heterodyne gate 20, two parallel-transfer prisms 21 and 22, a guide mirror 23, and a full-length lens the drum scanner 24 and the aperture stop 25 at the entrance of the exposure photodetector, located along the axis of the reference beam of the holographic scheme of the mobile eHT hologram 26 in the plane (Sassett 18, telescopic syst ems 27.28 behind the cassette 18, the movable point flap 29 and the lens 30, separately

located on the middle axis of the 1st order of diffraction of the heterodyne beam on the hologram lenses of the scanner 24, and the heterodyne beam after the mirror 23 passes through the image from-:

Aperti diaphragm 16 created by the lens 17 on the hologram lenses of the scanner 24, at an angle corresponding to the average carrier spatial frequency of these lenses, and in the zero order of diffraction through the opening of the diaphragm 25 on the photoelectric photoelectric multiplier (PMT) 34, optically coupled through reflection with a photocathode PMT 33, and

+ 1-D order of diffraction of the heterodyne beam on the hologram lenses of the scanner 24 through the collecting lens 30 is focused on the photodiode 45, the prism 12, 13, and 21, 22 parallel transfer

serve to input signal and heterodyne rays inside the drum 24 An electronic circuit multiplying amplification and detection of photodetector signals consists of a two-position input switch For an oscilloscope 35, a dual two-position input switch for multiplier 36, 37, first mixer 38, amplifier 39 for total radio frequency signals, amplifier 40 light beat frequency signals, second mixer 41, intermediate frequency signal amplifier 42 (local oscillator frequency) of synchronous detector 43, local oscillator 44.

The optoelectronic illumination circuit consists of a photodiode 45 and a video amplifier 46, and the code of the first PMT 31 of the output photodetector through

the switch 36 is connected to the signal input of the first balanced mixer 38, the output of the second photomultiplier 32 is connected via switch 35 to the input of the oscilloscope 47 and through the switch 37 to the input of the amplifier 40 of the light beat frequency output of the first photomultiplier 33 of the exposure photoreceiver connected to the signal input

the first balanced mixer 38, the output of the second PMT 34 through the switch 37 to the input of the amplifier 40 signals the frequency of light beats, the outputs of the amplifiers of signals of the total radio frequency 39 and the frequency of light beats 40 are connected to the inputs of the second balanced mixer 41, the output of which is connected to the input of the amplifier 42 intermediate signals frequency 42. The output of the amplifier 42 of the signals of the intermediate frequency and the output of the local oscillator 44 are connected to the inputs of the synchronous detector 43, the output of which is connected to the X input of the oscilloscope 47 and through a switch 35 to the Y input the oscilloscope 47, the output of the photodiode 45 is connected to the input of the video amplifier 4b, the output of which is connected to the input (luminous) Z of the oscilloscope 47,

The device operates in succession in three modes: in the recording mode of the test hologram, in the measurement mode of the family of signal holographic characteristics by the received test hologram and in the measurement mode of the intensities of the reference field, at which the signal characteristics of the family were measured.

In the recording mode of the test hologram, the gates 3 and 9 are opened, the shutter 20 is closed. The drum 24 is fixed in such a position that the signal flow passes in the gap between the hologram lenses without being subjected to any distortion.

The laser beam 1 is split by splinter 2 into two beams, which go to the reference (elements 3-8) and signal (9-17) channels. Knife filters 6 and 1 are oriented orthogonal with respect to each other. As a result of diaphragm 8 and 16 acting as low-pass filters in the hologram registration plane (in the frame window of the cassette 18), two orthogonal one-dimensional illuminance distributions arise: one horizontally (signal) and the other vertically (reference). Thus, the same intensity distribution of the signal field is recorded on a hologram at different values of the parameter — the intensity level of the reference field.

In the mode of removing the families of signal characteristics, two values are measured simultaneously - the intensity value of the signal field at a given point of the frame of the cassette 18 when shooting

0

five

0

five

0

test hologram and the corresponding value of the diffraction efficiency of the resulting test hologram.

This measurement is carried out line by line, each line corresponds to a certain value of the intensity of the reference field, the lines are formed due to the stepped arrangement of the hologram lenses on the reel 24, the number of lines is equal to the number of hologram lenses, usually enough To have 5-8 lines.

The intensity distribution of the signal and reference fields is measured by the so-called optical heterodyne scanning method, and to obtain the field intensity itself, the optical signal is detected by a two-channel photodetector and then multiplied by electrical signals in the electronic device; due to this, the narrowing of the signal frequency band and the suppression of the shot effect of the photoelectric effect are also achieved.

The heterodyne scan is performed by rotating the hologram-lens drum due to the diffraction of the signal beam of the holographic scheme in the mobile + 1st order of the hologram lens and the heterodyne beam in the fixed zero order of the hologram lens. When the drum rotates + 1-st, the order of the wide signal beam oscillates relative to the fixed zero order of the narrow heterodyne beam, obtaining an average Doppler shift of the light frequency by

Doppl.sr

 v ,,.

, er

(one)

where v

Yy

.sr.

-linear speed of movement of the hologram lenses;

- average carrier spatial frequency of holographic lenses.

When the holographic lens is moved, the Doppler shift of the frequency of the light in the signal beam + 1 st order changes in the band

ch

,,

(2)

where is the distance between the scanner

and a hologram; spatial strip

frequencies in the hologram lens; LP - scan line length

on the test hologram with

reading it;

 - wavelength of light. Zero-order heterodyne beam gets through the opening of diaphragm 25 to the photocathode of the PMT 34 of the exposure photoreceiver, is partially absorbed in it, and partially reflected from its surface, the reflected part falls on the photocathode of the PMT 33 of the same photoreceiver. Thus, at the outputs of both PMTs, beat signals appear between the zero-order constant-heterodyne beam field and the current portion of the swinging signal field -t-1th order entering the aperture of the same diaphragm 25. The average frequency of these beats is equal to d „ppl ° (1). The amplitude of these beats is proportional to the product of the amplitudes of the heterodyne field (which in this case is constant) and the total small portion of the signal field + 1-th order, the beam from which at the moment turns out to be collinear with the heterodyne beam. Switch 36-37 in the readout mode of the signal field is in position 1 (top) and the beat signals from the photomultiplier outputs 33 and 34 are fed to the inputs of the electronic multiplication circuit. The signal from the PMT 33 is converted upward in frequency after mixing it with oscillations of the local oscillator 44 of the frequency f in the balanced mixer 38 to the frequency

 f,

+ f.

(3)

g - AOFPL This converted signal is amplified by a bandpass amplifier 39 and mixed in a mixer 41 with a beat-frequency signal amplified in an amplifier 40 by a photomultiplier tube 34. A differential frequency signal equal to the local oscillator frequency is removed from the output of mixer 41. The frequency band of this signal is determined by its amplitude modulation; therefore, it is much narrower than the band defined by the formula (2) this signal is amplified by a narrowband resonant amplifier 42 and detected in a synchronous detector 43, the reference input of which also receives the local oscillator 44. The output signal synchronous detek5

you j5

20

25

thirty

five

0

five

0

five

the torus enters input X and through switch 35 (in the measurement mode of the reference field intensity) to input U. At the same time, a scan of the 1 st order of diffraction of the heterodyne beam on the hologram lens is scanned using a test hologram. This beam is focused on the surface of the test hologram due to the corresponding focal length of the hologram lens. The light flux diffracted in the test hologram propagates along the direction of the reference beam through the telescopic system 27-28 to the diffraction photodetector 31-32. In the measurement mode of the signal characteristics, the flap 29 is inserted into the image of the reference source. Thus, the diffraction photodetector is protected from the diffraction of the signal flow of the holographic scheme on the test hologram (which gives the reconstructed image of the reference source of the holographic scheme ). In the measurement mode of the signal characteristics in the diffraction photodetector, only one PMT 32 is used. The video signal of the current diffraction efficiency comes from the output of the PMT 32 through switch 35 to the input U of the oscilloscope 47. Thus, as a result of the joint effect of the signals from the output of the PMT 32 (to input Y) and from the output of the synchronous detector 43 (to the input X) as the hologram-lens drum-scanner 24 rotates on the oscilloscope 47, a family of signal holographic characteristics of the FRS appears.

In the intensity measurement mode of the reference field, a reference hologram 26 is inserted into the cassette 18 free from the existing FRS, obtained in advance on high-quality material in the same holographic scheme, but with remote knife filters 6 and 14, the point flap 29 is removed, the gate of the signal beam 12 in the holographic the circuit is closed, the gates of the heterodyne beam 20 and the reference beam 3 of the holographic circuit are open the switches 36 and 37 connect the outputs of the photomultiplier 31 and 32 to the inputs of the multiplication circuit. When the drum 24 rotates, the photomultiplier tubes 3I and 32 output the beating signals between the field of the reference beam, which passed in the zero order

reference hologram, and the field of the scanning heterodyne beam diffracted in + 1-M order on the reference hologram. Since the reference hologram was obtained in the same holographic scheme, but with remote knife filters 6 and 14, firstly, it has the same diffraction efficiency across the entire aperture, and, secondly, the scanning diffracted in its + 1M order the heterodyne beam always turns out to be collinear with the beam from the reference source in the aperture of the aperture 8 of the holographic scheme, passing in the zero order of the reference hologram through the point on it where the probe beam currently hits. As a result, the voltage at the output of the synchronous detector is proportional to the intensity of the reference field at this point. Since the reference field along the lines is constant and only changes when moving from one line to another, the oscilloscope 47 operating in the internal scanning mode, synchronized with the rotation of the drum 24, displays a step curve describing the intensity distribution of the reference field — the parameter values where a family of signal holographic characteristics is taken.

The electron beam of the oscilloscope tube should be opened only at the time of the forward scan of the probe beam in the test hologram, i.e. at the time of formation of the signal characteristics. To do this, an optoelectronic illumination circuit is used, which consists of collecting lenses 30, photodiode 45 and video amplifier 46. Lens 30 is placed on the middle diffraction axis + 1-H order of the probe beam on the hologram lenses of the scanner so that it displays the center of scanning the input window of the photodiode 45, so that the photocurrent at its output flows throughout the entire time: while this order falls into the aperture of the lens 30, in turn, this aperture is limited to the dimensions corresponding to the scan window size of the cassette 18. Formed nye thus video pulses are amplified photocurrent video amplifier 46 and act on the brightness control input Z of the oscilloscope 47,

0

five

0

50

five

0

five

Thus, when using the proposed device, the time spent on obtaining families of FRS characteristics is significantly reduced as a result of using the ability to quickly scan using a hologram-lens drum while simultaneously increasing the measurement accuracy due to eliminating the effect of power losses of the coherent light source during automatic reading Correspondence between the coordinates of the current reading points of the test hologram and the signal and reference fields. Practically, the time taken to obtain one family of holographic characteristics of the FRS is the time it takes for a test hologram to be produced, since the actual reading of the family of signal characteristics in the proposed device is the time of one revolution of the hologram of a chio-lens drum, i.e. units of milliseconds. For a halogen-silver FRS, the time for developing and fixing a hologram can take from ten minutes to several tens of seconds, depending on the photochemical process used, for a photothermoplastic material - about a second. Therefore, when using the proposed device, it is more advantageous for halide-silver materials to record test holograms and their appearance by arrays of frames obtained in a wide range of intensities of the signal and reference rays. The required dynamic measurement range can be achieved by optimizing the frequency band of the amplifiers of the beat frequency signals and the total radio frequency by suppressing the radio path noise and the shot noise of the photocurrents passing through the mirror frequency channels and using synchronous detection.

Claims (1)

Invention Formula A device for measuring the holographic characteristics of photographing media containing a coherent light source, a holographic scheme consisting of signal and reference channels containing successively located shutter, guide mirror, attenuator, knife filter, micro lens with filtering diaphragm for spatial frequencies, in the place of convergence of the channels of which the cassette with the medium under study is located, the optical readout system consisting of a heterodyne beam coupler located on the axis of the reference channel to the shutter, and successively located on the optical axis of the shutter of the guide mirror, the scanner and the collecting lens, and the measuring electrical circuit consisting of an exposure and diffraction photodetectors and a two-coordinate oscilloscope by the fact that, in order to increase productivity and accuracy of measurements, an additional 1 Lens objective was introduced into it, parallel transfer prisms located in the signal channel between the attenuator and the knife filter, and in the reading system, between the shutter and the guide mirrors, a radio electronic circuit for multiplying, amplifying and detecting signals of photodetectors, a photodiode and a video amplifier, a reference hologram, a telescopic system with a point flap, and a dual two-position switch, and the scanner is designed as a drum with hologram lenses with a rotation mechanism and parallel-transfer prism prisms, a knife filter, a micro-lens with a filtering diaphragm of the signal channel of a holographic scheme with reflecting The lens and guide mirror of the readout system are placed inside the drum, while the imaging lens is located on the axis of the signal channel whose axis intersects the axis of the readout system and makes an angle equal to the diffraction angle on the center carrier frequency of the holographic lens, the collecting lens is on the middle the diffraction axis + 1-th order of the beam reconstructed from the hologram lens to map the scanning center to the input window of the photodiode, the input window of the exposure photodetector is located on the zero axis On the order of diffraction of a beam reconstructed from a hologram lens, the reference hologram can be moved in the plane in front of the checkout. , Jq | 5. 20 25 jq. 35 40 0 5th, the telescopic system is located behind the cassette along the axis of the reference channel, the point flap is arranged to move in the image plane of the reference source of the holographic scheme, the input window of the diffraction photodetector is located on the axis of the reference channel behind the plane of the position of the point flap, the photodetectors of the exposure and diffraction contain two photoelectronic multipliers whose photocathodes are optically interconnected by an electronic radio multiplication, amplification and detection scheme Photo detector receivers consist of a mixer, a local oscillator, a synchronous detector, a total radio frequency signal amplifier, an intermediate frequency amplifier of light beats, and an intermediate frequency amplifier, the output of the first photoelectric multiplier of the output diffraction or exposure photoreceiver is connected to the inputs of the first mixer, the output photodiode the second photomultiplier diffraction or exposure photodetector is connected through the same p reklyuchatel with the input of the amplifier The signals of the frequency of light beats, I the output of the second photomultiplier tube of the diffraction photodetector is also connected via a switch to the input of the oscilloscope, while the heterodyne output is connected to the input of the first mixer, the output of which is connected to the amplifier of the total radio frequency, the outputs of the amplifiers of the signal of the total radio frequency and frequency of light beats are connected to the inputs of the second mixer, output which is connected to the input of the intermediate frequency signal amplifier, the output of the intermediate frequency signal amplifier and the output of the local oscillator is connected with the inputs of the synchronous detector, the output of which is connected to the X input of the oscilloscope, and through a switch to the U input of the oscilloscope, and the output of the photodiode connected to the input of the video amplifier whose output is connected to, the input Z of the oscilloscope. w