SU1589099A1 - Apparatus for checking optical transfer function of optical system - Google Patents

Abstract

The invention relates to a measurement technique and can be used to control the quality of optical systems, preferably long-focus ones, by determining the optical transfer function. The aim of the invention is to improve the accuracy of the control. The radiation that has passed the test object 2 and the lens of the collimator 3 falls on the test lens 4, in the focal plane of which the analyzing slot 5 and the photoreceiver 6 are located. The control unit 10 eliminates the influence of the device base vibration from the measurement results and provides the step motion mode test object 2 required to align the device. 1 hp f-ly, 3 ill.

Description

SP

00

3158

The invention relates to a measurement technique and can be used to control the quality of optical systems, preferably long focal ones, by determining the optical transfer function (OTF).

The aim of the invention is to increase the accuracy of the control.

 FIG. 1. shows a general diagram of the device in FIG. 2 is a control block diagram; in fig. 3 is a diagram of a switching unit.

The device consists of a collimator jpra 1, in the focal plane of which i the test object 2 is installed, made in: a view of a ring radial raster. The radiation of the collimator 1, which passed the test object 2 and the collimator lens as a parallel beam, enters the input of the test optical system 4, in the focal plane of which the analyzing slit diaphragm is installed 5. Behind the diaphragm 5 there is a radiation receiver 6, to the output of which connected in series a narrowband electric filter 7 and a reading device 8.

The test object 2 is installed on the shaft of the electric motor 9, the input of which is connected to the output of the control unit 10

I

motor speed:. On the shaft of the electric motor 9 is mounted - flax optocoupler 11. Inputs

The motor speed control unit 10 is connected to a variable frequency generator of 12 pulses, with a stable frequency generator of 13 pulses with a single pulse generator of 14 single pulses, with an operating mode switch 15, with a rotational direction switch 16

and with switch 17 stop mode

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The engine speed control unit 10 comprises a pulse width modulator (PWM) 1B, which is the output of control unit 10, a switching unit 19, the output of which is connected to the PWM input 18. A constant source 20 is connected to the inputs of the switching unit 19 the control signal, the operating mode switch 15, the rotational direction switch 16, the stop mode switch 17, and the frequency discriminator 21, which is connected to

With a discriminator 22, with an auxiliary frequency detector 23, with a generator of 12 adjustable frequency pulses and with an optocoupler 11. A switching discriminator 24 and a true motion driver 25 are also connected to the switching device 19.

The 1pulse discriminator 24 is connected to a single-pulse generator 14 and an optical sensor 11, and a true direction of movement driver 25 connects to a sensor output 11. Switching unit 19 contains a reversible pulse counter 26, the counting input of which is connected to the output of the optical sensor 11. Counter input for the Addition-subtraction command, it is connected to the output of the true rotation direction generator 25. The meter installation input is connected to the stop switch 17.

In addition, the switching unit 19 contains the majority element 27 having three inputs: the first input is connected to the counter output of the reversible pulse counter 26, the second input is connected to the output of the switch. 17 stop mode, and the third input of the majority element is connected to its own output. Switching unit 19 also includes an inverter 28, the input of which is connected to the output of the stop mode switch 17, and the output connected to one of the inputs of the first element. EXCLUSIVE OR 29. The output of the EXCLUSIVE -OR element is connected to the control input of the first switch 30. Comm .: The inputs of the first switch 30 are connected to a constant control source 20 and frequency discriminator 21. The output of the first switch 30 is connected to one of the switching inputs of the second switch 31. The other input of the second switch 31 is connected to the output of the pulse discriminator 24.

The control input of the second switch 31 is connected to the switch 15 operating modes. The output of the second switch 31 is connected to one of the inputs of the PWM 18.

Switching unit 19 also contains an OR element 32, one input of which is connected to the output of the majority element 27, and another input connected to the switch 15 operating modes.

The output of the element 32 is connected to one of the inputs of the SHSh 18. In addition, the block 19 contains the second EXCLUSIVE CHI 33, the inputs of which are connected to the output of the rotation direction switch 6 and to the true rotation direction generator 25, and the output is connected to the input of the first EXCLUSIVE OR element 29 .

The device works as follows.

Preliminary, based on the test program of the optical system, the required rotation frequency of the disk 2 and, consequently, the motor shaft 9 is calculated. For example, if the node has a band-pass filter 7, it has a resonant frequency of 1000 Hz and the test object 2 has a raster with a total number of strokes 1000 , then the rotational speed of test-volume 2 should be equal to 1 rev / s. Accordingly, a generator of 13 stable frequency pulses is tuned to a frequency equal to the resonant frequency of the filter 7. If the raster of the optical sensor 11 has 10,000 strokes per circumference, then at the found Rotation frequency of the motor 9 in 1 rev / s, the generator of 12 pulses of the adjustable frequency must be tuned per pulse frequency of 10,000 Hz.

The operator also presets the desired mode of operation by appropriately setting the operation mode switches 15 and the direction of rotation 16.

After performing these actions, the operator switches the stop mode switch 17 from the Stop position to the On position. This starts the operation of the installation and the measurement of the OTF.

The pulses from the I2 generator of the controlled frequency and the signal from the opto-sensor 1 are fed to the frequency detector 21, where two signals are compared and the result is fed to the input of PWM 18 as an electrical signal. The auxiliary frequency detector 23 sets the optimal gain of the system for this frequency of the electric motor 9. with the PWM is fed to the electric motor 9, as a result of which the electric motor 9 comes into rotation

to

15

20

five

0

five

0

five

0

five

in the right direction and with a given frequency.

The motor 9 drives the test object 2 into rotation. In this case, the radiation beam of the collimator 1 is modulated, and therefore the radiation flux passing through the lenses of the collimator 3 and the system under test 4, as well as the analyzing aperture 5 and entering the radiation receiver 6, changes in time.

After linear conversion of the modulated radiation in the radiation receiver 6 into an electrical signal, it is fed to the input of the narrowband filter 7, where the main harmonic modulation frequency is extracted from it, which is then recorded by the counting device 8.

From the output of the filter 7, the signal also goes to the phase discriminator 22, where a phase comparison with the pulses generated by the generator 13 of stable frequency pulses occurs. The phase discriminator 22 detects a temporal divergence of the output pulses of the filter 7 and the generator 3 of stable frequency pulses and outputs a signal proportional in magnitude and sign to the phase shift between the said pulses, while the pulses arrive at the inputs of the phase discriminator 22, it produces a zero signal.

Due to the presence of vibrations of the base, the receiving part of the stand, including the analyzing diaphragm 5 and the radiation receiver 6, moves relative to the radiating part, as a result of these oscillations, the instantaneous phase, and consequently, the instantaneous frequency of the signal coming from the receiver output 6 of the radiation to the narrowband filter 7 The changes continuously in proportion to the law of vibration.

When the phase of the pulses at the output of the radiation receiver due to vibrational oscillations changes, these changes are recorded by the phase discriminator 22, which produces the corresponding signal. This signal, as a control signal, is fed to frequency discriminator 21, as a result of which the instantaneous frequency of rotation of the electric motor 9 changes, and in such a way that the instantaneous speed of the raster image movement along the analyzing diaphragm remains constant and equal to that value in the absence of vibrations .. The frequency of modulation of the signal at the output of the radiation receiver remains constant and equal to the initial value. Thus, by compensating for the vibration of the base, additional measurement error is eliminated.

The stepping mode of the disk is necessary for the alignment of the stand and its task is to fix the disk in any arbitrary angular position. The operation of the device in this mode is as follows. In order to stop the test object 2 in a given position, initially reduce the frequency of rotation of the electric motor 9 by reducing the frequency of the generator 2 to; some minimum value, at: about 0.1 of the nominal frequency of rotation I. Further, the switch switches the fir 17 stop mode to the stop position. In this case, the electric motor 9 goes into braking mode, the stopping of the electric motor 9 will occur in a position that is beyond the desired position. The engine is brought to the required position using a positional system, the operation of which is based on the use of an optocoupler sensor as a feedback sensor.

On command-Stop, coming from the switch 17 of the stop switch, the reversing pulse counter 26 is started, the clock input of which receives the signal from the output of the optocoupler sensor 11, and the input of the true rotational direction of the engine from the driver 25 true direction of rotation.

Command. The stop also goes to the input of the inverter 28, the output signal of which is fed to one of the inputs of the EXCLUSIVE OR 29 element. At the other input of the element 29, a signal is received from the output of the EXCLUSIVE OR 33 element. At the same time, at the output of the 33 element;

have a logical o

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the true direction of rotation coincides with the required J otherwise the output of element 33 is logical 1. The output signal of the second element is EXCLUSIVE OR 33, arriving at the first switch 30 through the first element EXCLUSIVE OR. 29, disconnects frequency discriminator 21 from PWM 18

and instead connects a control signal source 20. The polarity of this signal is such that the engine 9 is reversed, in which case it initially enters a deceleration mode, then stops, and then begins to rotate in the opposite direction. Due to the change in the direction of rotation of the motor, the signal at the output of the second element EXCLUSIVE OR 33 and through the first element EXCLUSIVE OR 29 changes the frequency discriminator 2 to PWM 18 via the first switch 30 and additionally changes the signal to the input Addition- subtracting the reversing counter 26. When the reversing counter 26 is zeroed, a command is sent from its output to the majority element 27, from the output of which the commander is fed to the OR 3 element, from where the signal is fed to the PWM 1.8 input and blocks it, to which the motor 9 stops.

For operation of the device in a step-by-step mode, the switch 15 operating modes is transferred to the Step position. In this case, the command from the switch 15 operating modes enters the second switch 31, which connects the pulse discriminator 24 to the PWM 18. The command from the switch 15 operating modes of the software Step on the element OR 32, which unlocks the output of the PWM 18, as a result of which the PWM output is connected to motor 9. When 14 single pulses are fed from the generator to the pulse discriminator 24, the latter produces a voltage applied to the motor 9 and ensuring its rotation in a direction that corresponds to the field zheniyu switch 1 June .napravleni rotation. In this mode, the engine control module presents a clamped positional control system in which the error measurement is performed by the pulse discriminator 24, the pressure signal is received from the generator 14 of single pulses, and the optocoupler 11 is a position feedback sensor.

The first input of the pulse discriminator 24 receives the pulses of the opto-sensor 11. The signals from the generator 14 of a single pulse are fed to the second input of the pulse discriminator 24. The other inputs of the discriminator 24 receive signals, from the former 25 of the true direction of rotation, as well as from the switch 16 of the direction of rotation. The output signal of the pulse discriminator 24 is fed to the control channel of the electric motor 9, which rotates the specified number of pulses on the generator 14 single pulses.

Thus, it is possible to install the engine shaft in any position with an accuracy equal to the angular pitch of the optical sensor.

Claims (2)

 Invention Formula I. Device for monitoring the optical transfer function of optical systems, mainly for long-focal ones, containing a collimator, in the focal plane of which a test is installed. An object made in the form of an annular radial raster deposited on a rotating disk, mounted on an electric motor shaft. also installed on the motor shaft, the engine speed control unit containing the frequency discriminator and pulse-width modulator, the pulse generator adjustable frequencies analyzing the aperture installed in the focal plane of the optical system under test, radiation receiver, narrow-band electric (} clip and reading device, about the fact that, in order to improve the accuracy of control, a stable frequency pulse generator was inserted into the device; single pulse generator, mode switch, rotational direction switch, stop mode switch, and a switch unit, a constant control source, phase disc iminator, auxiliary frequency discriminator, pulse discriminator, true rotation direction maker, while the outputs of the mode switch, the direction of rotation switch, mode switch, stop ,: the constant control source and frequency discriminator switch 10 five 0 5 0 5 0 5 Q j are sent to the inputs of the switching device, and the output of the switching device is connected to the motor input via a pulse width modulator, one of the frequency discriminator inputs is connected to the output of the adjustable frequency generator, the second frequency discriminator input is connected to the output of the optron sensor, the third frequency discriminator input is connected to the output of the auxiliary frequency discriminator, whose input is connected to the output of the variable frequency generator, the fourth input of the frequency discriminator is connected to The output of the phase discriminator, one of the inputs of the phase discriminator is connected to the output of a stable frequency generator, and the other input is connected to the output of a narrow-band electric filter, one of the inputs of a pulse discriminator is connected to the output of a single pulse generator, and its other input is connected to the output of an optron sensor , its third input is connected to the output of the true direction, rotation, and its fourth input is connected to the rotation direction switch; the input of the true rotation direction driver is connected to the output of the opto-sensor. 2. The device according to claim 1, about tl and - the fact that the switching device contains a reversible counter, majority element, inverter, OR element, two elements EXCLUDE. THE ORDER OR, two ko} at the mutator, while the counting input of the reversible counter is connected to the output of the optocoupler sensor, the input of the reversible counter, Addition-subtraction is connected to the output of the imager. and the setup input is connected to the stop mode switch, the first input of the majority element is connected. The second input is connected to the output of the stop mode switch, the third input is connected to its output, and the output of the majority element is connected to the input of the OR element, the second input of the OR element is connected to the operating mode switch, the output of which is connected to one of the the input of the pulse-width modulator, the input of the inverter is connected to the output of the stop mode switch, and the output of the inverter is connected to. One of the inputs of the EXCLUSIVE OR element, whose output is connected to the control input of the first switch, the first signal input of this switch is connected to the output of the frequency discriminator, and the second signal input is connected to the output of the constant control signal source, the output of the first switch is connected to the first signal source the input of the second switch, and the second signal input of the second switch is connected to the output of the pulse discriminator, the output of the second switch is connected to the input of the pulse-width modulator of the motor, and the control input of the second switch is connected to the mode switch, the second input of the first element is EXCLUSIVE OR connected to the output of the second element EXCLUSIVE ITS OR, one of the inputs of the second element EXCLUSIVE ILI is connected with the switch of the direction of rotation, and the other input with the output of the true direction of rotation driver. 2 Fig.d