SU1697743A1 - Device for measuring critical frequency inducing flicker merging - Google Patents

Abstract

The invention relates to medical technology and can be used for diagnostic purposes. The purpose of the invention is to increase the reliability of the device by simplifying its design. The device contains a 1 code-frequency converter, a source of 2 light pulses, a meter 3 frequencies, the first 4 and second 5 keys, the element OR 6, the register 7 of the successive approximation. The device uses a bit-balancing algorithm that minimizes the time spent on one study. 1 il.

Description

The invention relates to medical technology and can be used for diagnostic purposes.

The aim of the invention is to increase the reliability of the device by simplifying its design.

The drawing shows a functional diagram of a device for measuring a critical flicker frequency.

The device contains a transducer 1 kodgfrekto, source 2 light pulses, meter 3 frequency, the input of which is connected to the input of source 2 and to the output of the converter 1, the first 4 and second 5 keys and the element OR 6, the first input of which is connected to the output of the key 4, and the second the input is with the output of the key 5. The device also contains a sequential register 7, the approximation whose outputs are connected

with converter inputs 1, first input

- with the output of the element OR 6, and the second input

- with the output of key 4. The inputs of the keys 4,5 are connected to one of the outputs of the register 7.

- The device works as follows.

Preliminarily, the zone of permissible flicker frequency measurement values is found.

Af - fmax fmin,

where fmax is the maximum value of the flicker frequency;

fmin - the minimum value of the frequency of flickering.

For various people and conditions, the critical flicker frequency (CFLF) is between 20 and 60 Hz, i.e.

Os

About vj

2

with

20 Hz Ghchsm 60 Hz

the time spent on conducting one test can be minimized if the zone of permissible values of the change in the frequency of the flashes of the stimulus signal is determined on the basis of the characteristic and previously measured values for the particular test subject fmax and fmin,

The subject is presented with a source of 2 light pulses with a flicker frequency value discretely varying in zone A f. The value of fWM can be with equal probability at any point of the Af zone. Therefore, the zone A f can be divided into two equal parts, one of which contains fK4CM, and the other is not. Therefore, the subject at the first test step is presented with the midpoint of the zone A f. In the event that it sits on flicker, is in the high-frequency part of zone A f, if not, then in the low-frequency part, After the measurement carried out at the first step, the width of the permissible zone of change of the flicker frequency decreases to a value equal to 1/2 Af, At the second step The events again select the frequency of flashes, different to the average frequency of the allowable zone, limited in the previous step. Carrying out similar measurements, determine the new value of the zone of acceptable values, which will be equal to 1/4 Af. Thus, the measurement process (kfcm described by the device is a discrete sequence (consisting of I steps) presenting the subject with different values of the flashing frequency of source 2. After each presentation, a new range of flashing frequencies containing 1 kcm cm, which is 2 times less the previous one. The number of steps I is determined by the required measurement accuracy.

The code-frequency converter 1 is constructed in such a way that the number of discrete values of the flicker frequency in the zone Af must necessarily be equal to the limiting binary number determined by the width of the register 7 of the sequential approximation. In addition, a change in the output binary code of register 7 from the extreme value of 000 - 0 to the extreme value of AND - I should cause a corresponding linear change in the discrete values of the flicker frequency FROM fmm TO fmax.

The initial state of the register is 7000 - 0. At the same time, for convenience of operation with the device, source 2 is not illuminated. Before testing, the subject presses any

Of the keys 4,5 and in the highest (left according to the drawing) bit of register 7, a test logical unit appears. A trial code of the register 1000 - 0 means that the subject is presented at the first step to the center frequency of the zone A f.

After that, and then at each subsequent step of the presentation, the subject-presses one of the keys 4 or 5, depending on whether he sees flickers (Yes - key 4) or does not see (No - key 5). If he presses key 4 in the first step, then the unit in the high register of bit 7 is recorded permanently through the second (information) input by the signal from the output of the element OR 6 at the first (clock) input. - If

he presses key 5 in the first step, then the logical zero is finally written to the high bit.

After receiving the reaction of the subject in the first step, the next unit of register 7 will establish a test logical unit, etc., i.e. get a new range of values of the frequency of flashes containing chsm, which is 2 times less than the previous one. At the last 1 st step of presentation

Probe logical unit in the lower half of register 7 blocks the keys 4 and 5. At the same time, the frequency meter 3 indicates the desired frequency Tkchsm with a given accuracy.

Claims (1)

Invention Formula An apparatus for measuring the critical flicker frequency, comprising code-frequency converter, source of light pulses, frequency meter, the input of which is connected to the input of the source of light pulses and the code-frequency converter output, element OR-, first and the second keys, the outputs of which are connected to the inputs of the OR element, differing in that, in order to increase the reliability of the device by simplifying its design, a register is entered into it serial approximation, the outputs of which are connected to the code-frequency converter inputs, the first input is connected to the output of the OR element, the second input is connected to the output of the first key, and one of outputs connected to the inputs of the first and second key.