RU2219821C2 - Apparatus for detecting critical frequency of light flashing - Google Patents

Abstract

FIELD: medical equipment, namely apparatuses for investigating eyes functioning. SUBSTANCE: apparatus includes ramp voltage generator, voltage-frequency converter, source of light pulses, switch for setting generator in mode for generating rising voltage, switch for setting generator in mode for generating drop voltage, mode change-over switch, tumbler, single-shot multivibrator, gate circuit, counter and display. Ramp voltage generator, voltage-frequency converter and light pulse source are connected in series. Outlet of switches are connected with inlet of mode change-over switch. Outlet of tumbler at normally open contacts is connected with inlet of single-shot multivibrator; outlet of tumbler at normally closed contacts is connected with cleaning inlet of counter. Outlet of single-shot multivibrator is connected with second inlet of gate circuit whose first inlet is connected with outlet of voltage-frequency converter and whose outlet is connected with counting inlet of counter. Outlet of counter is connected with inlet of display. Apparatus also includes additional switch and second single-shot multivibrator whose outlet is connected with third inlet of mode change-over switch. EFFECT: enhanced accuracy of detecting critical frequency of light flashing. 2 dwg

Description

 The invention relates to medical equipment, namely to devices for determining the degree of human fatigue and diagnostic studies.

 A device is known for measuring the critical fusion flicker frequency, comprising a pulse generator, a first inhibit element, a reverse counter, a digital-analog converter, a voltage-frequency converter, a second inhibit element, a light pulse source, a test button connected in series, a trigger that is waiting for a pause multivibrator, waiting a reset multivibrator, as well as a recorder, a comparator, and an I element, and the output of the standby reset multivibrator is connected to the second trigger input hera, converter output voltage - frequency is connected to the input of the recorder, the comparator input is connected to the output of the digital-analog converter, and the output is to the input of the initial installation of the reverse counter, the first input of the element And is connected to the output of the generator, the second to the output of the trigger, and the output to the second the input of the reversible counter, the second inputs of the first and second elements of the prohibition are connected to the output of the trigger (ed. certificate of the USSR 1292734, MKI A 61 V 5/16).

 When measuring the critical frequency of light flicker, the subject is presented with a source of light pulses with a discretely changing value of the frequency of flicker in the range of 20 ... 50 Hz with a step of 1 Hz and an exposure of 1 s. After the critical frequency of light flickers is detected, the value of the frequency of light pulses decreases by 5 Hz and the test is repeated.

 A device is known for measuring the critical fusion flicker frequency, comprising a code-frequency converter, the output of which is connected to the inputs of a light pulse source and a frequency meter, a trigger, the output of which is connected to one input of the code-frequency converter and the first input of the shift register, the second input of which is connected to the output of the OR element, the first input of which is connected to the first input of the trigger and the output of the first key, and the second input to the second input of the trigger and the output of the second key, the outputs of the shift register connected to other inputs of the code-frequency converter, one of the outputs of the shift register is connected to the inputs of the first and second keys (ed. certificate of the USSR 1373399, MKI A 61 V 5/16).

 When measuring the critical frequency of light flicker, the subject is presented with a source of light pulses with a discretely changing value of the frequency of flicker. At the first test step, the frequency of light flicker is equal to the midpoint of the zone of possible values of 20 ... 60 Hz. If the subject sees flickering, the critical frequency of light flickering is in the high-frequency part of the zone of possible values, if not, in the low-frequency part. At the second step, the subject is presented with a flicker frequency equal to the midpoint determined at the first step of the high-frequency or low-frequency part of the zone of possible values, etc. The number of steps is determined by the required measurement accuracy.

 A disadvantage of the known devices is the large number of steps for determining the critical frequency of light flicker, which takes considerable time, leads to additional fatigue of the visual analyzer, and therefore, to a decrease in the accuracy of measurement results.

 Closest to the technical nature of the present invention is a device for measuring the critical frequency of light flickering, containing the keys "Increase frequency" and "Decrease frequency", toggle switch "KCHSM", display unit, one-shot, valve, counter and serially connected mode switch, generator linearly a changing voltage, a voltage-frequency converter, a light pulse source, and the key outputs are connected to the inputs of the mode switch, the normally open switch output is input single-vibrator house, normally closed - with the input of zeroing the counter, the output of the single-vibrator is connected to the second input of the valve, the first input of which is connected to the output of the voltage-frequency converter, the output is to the counting input of the meter, the output of the meter is connected to the input of the display unit (RF patent 2141253, MKI A 61 B 5/16).

 The disadvantage of this device is the low accuracy of measuring the critical frequency of light flickering, since it is determined at a continuously changing frequency, and the human eye is more sensitive to the perception of a discretely changing frequency [1].

 The inventive device allows to increase the accuracy of measuring the critical frequency of light flicker.

 In the present invention, in a device for measuring the critical frequency of light flickering, containing a linearly varying voltage generator, a voltage-to-frequency converter, a light pulse source, a generator setting key in an increasing voltage generation mode, a generator setting key in an incident voltage generation mode, a mode switch, a toggle switch, the first one-shot, valve, counter and display unit, and a ramp generator, voltage-frequency converter and sources light pulses are connected in series, and the key outputs are connected to the inputs of the mode switch, the normally open output of the toggle switch is connected to the input of the one-shot, normally closed to the input of zeroing the counter, the output of the one-shot is connected to the second input of the valve, the first input of which is connected to the output of the voltage-frequency converter, the output is with the counter input of the counter, the counter output is connected to the input of the display unit, an additional key and a second one-shot are introduced, and the key output is connected to the input of the second one-shot Ator, whose output is connected to the third input of the mode switch.

 The inventive device due to the introduction of an additional key and a second one-shot allows you to increase the accuracy of measuring the critical frequency of light flickers, as it is determined at a discretely changing frequency, to which the human eye is more sensitive compared to a continuously changing frequency.

 Thus, the claimed device differs from the known new property, causing a positive effect.

 In FIG. 1 shows a structural diagram of the inventive device, in FIG. 2 is a timing diagram of its operation.

 The inventive device comprises a linearly varying voltage generator 5, a mode switch 6, a voltage-to-frequency converter 7, a first 8 and a second 9 one-shots, a valve 10, a counter 11, a light pulse source 12, an indication unit 13, a key 1 for setting the generator in an increasing voltage generation mode , key 2 for setting the generator in the incident voltage generation mode, key 3 for increasing the frequency of the generator 5 by 0.1 Hz and the toggle switch 4.

 As the generator 5 of a linearly varying voltage, a standard integrator is used on the operational amplifier with input resistors switched by a switch 6 to obtain a different rate of increase in voltage at the output of the generator 5, and by changing the polarity of the input voltage, change the direction of integration (rise or fall of the output voltage).

 Keys 1-3 are manual switches to two positions for closing and opening electrical control circuits and are made in the form of control buttons.

 The device operates as follows. In the initial state, the toggle switch 4 is in the “Measurement” position, as shown in FIG. 1. When the power is turned on, the generator 5 provides a constant voltage to the converter 7, corresponding to the initial frequency F1 = 20 Hz of light flicker. A converter 7 converts this voltage to a frequency that controls the source 12 (time interval 0-T1).

 The test subject closes the key 1 (time T1) and through the switch 6 sets the generator 5 in the mode of generating a ramp voltage corresponding to the rate of change of the frequency of light flicker of the order of 20 Hz / s. Converter 7 converts this voltage into a proportionally changing frequency, which source 12 is converted into light pulses presented to the subject (time interval T1-T2).

 On the time interval T1-T2, the test subject, holding the key 1 in the closed state, determines the moment of fusion of light flickers, at which the key 1 opens (time T2, frequency F2). In this case, the generator 5 maintains a constant voltage at the output corresponding to the frequency F2.

 Then the subject closes the key 2 (time T3) and through the switch 6 sets the generator 5 in the mode of generating a linearly incident voltage corresponding to the rate of change of the frequency of light flicker of the order of 1 Hz / s. Converter 7 converts this voltage into a proportionally changing frequency, which source 12 is converted into light pulses presented to the test subject (time interval T3-T4).

 On the time interval T3-T4, the test subject, holding the key 1 in the closed state, determines the moment of distinguishing light flicker at which the key 1 opens (time T4, frequency F3). In this case, the generator 5 stores a constant voltage at the output corresponding to the frequency F3.

 Next, the test person by sequentially closing the key 3 determines the actual value F of the critical frequency of light flickers (time interval T4-T5). With each closure of the key 3, the second 9 single-shot generates a pulse, the duration of which corresponds to an increase in the frequency at the output of the converter 7 by 0.1 Hz.

 At the end of the measurements, the test subject switches the toggle switch 4 to the “Read” position, the first 8 one-shot generates a pulse of 1 s duration, which opens the valve 10. The frequency from the output of the converter 7 through the valve 10 goes to the counter 11, the counting result is displayed on the display unit 13.

 Thus, the proposed device allows to increase the accuracy of measuring the critical frequency of light flicker due to a discrete change in their frequency at the last stage of measurement.

Sourse of information
1. Copyright certificate 1346136 of the USSR, MKI A 61 B 5/16. A device for studying the critical frequency of flicker fusion. V.A. Maksimovich, V.I. Prokopets (USSR). - 4 p.

Claims (1)

A device for measuring the critical frequency of light flickering, containing a linearly varying voltage generator, a voltage-frequency converter, a light pulse source, a key setting the generator in the rising voltage generation mode, a key setting the generator in the incident voltage generation mode, a mode switch, a toggle switch, a one-shot, a valve, a counter and an indication unit, wherein a linearly varying voltage generator, a voltage-frequency converter and a light pulse source are connected are connected in series, and the outputs of the keys are connected to the inputs of the mode switch, the normally open output of the toggle switch is connected to the input of the one-shot, normally closed to the input of zeroing the counter, the output of the one-shot is connected to the second input of the valve, the first input of which is connected to the output of the voltage-frequency converter, the output is with the counter counter input, the counter output is connected to the input of the display unit, characterized in that a key and a second one-shot are additionally introduced into it, the key output being connected to the input of the second one-shot an amplifier whose output is connected to the third input of the mode switch.

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