JPS5991941A - Apparatus for measuring pupil diameter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pupil diameter measuring device, and more particularly to a pupil diameter measuring device that eliminates the influence of a reflected image of ambient light mixed into a pupil image of an eye to be examined.

2. Description of the Related Art Pupillometers have been known that scan the front part of the eye to be examined and measure the size of the pupil region of the eye using the imaged electrical signals obtained thereby.

Conventional devices of this kind extract a rectangular wave corresponding to the size of the pupil of the subject's eye by binarizing the imaged electrical signal as shown in FIGS. Since the device was configured to operate an integral circuit whose width is controlled and measure the diameter and area of the pupil using the output potential (2), unnecessary noise of different polarity was generated in the pupil recognition area of the rectangular wave. The presence of pupil diameter and area has the disadvantage of causing errors in the measured values of the pupil diameter and area. Furthermore, in order to prevent the above-mentioned drawbacks, with conventional devices, it is necessary to sufficiently block out the disturbance light that enters the front part of the subject's eye, and the field of view seen from the subject's eye is extremely limited. The front part of the subject's eye is photographed on a television monitor so that the pupil P is an optically dark area, and the amount of light is detected using the scanning line corresponding to the cursor marker S to determine the width of the optically dark area. It is known that the diameter of the pupil is further integrated for each scanning line to determine the area of the pupil.

FIG. 2 shows a configuration diagram of a conventional example of a pupil diameter measuring circuit.

Reference numeral 1 denotes a television camera, which images the front part of the eye EP by means of an imaging optical system B and outputs a video signal. 2 is a synchronization separation circuit, 2b indicates an H-(3) BYNO pulse, and 2C indicates a v-5yNc pulse. Reference numeral 4 denotes a video signal DC component regeneration circuit, which fixes the video signal to DC at every timing when the clamp pulse 2a is input, thereby adjusting the DC operating point of the video signal against fluctuations in signal output due to changes in subject brightness. to be fixed. Reference numeral 5 denotes a binarization circuit, which inputs a fixed DC video signal and performs binary quantization according to a preset DC slice level. In the video signal obtained by imaging the front part of the living eye, a lower signal level is provided in the pupil area due to a difference in the amount of reflected light compared to the iris and sclera areas that are the periphery of the pupil area. Therefore, by setting the DC slice level to i, the binarization circuit 5 outputs a rectangular wave 5a corresponding to the horizontal width of the pupil area.010 is an integrating circuit, and the rectangular wave 5a is used as an integral gate signal. A signal 10a containing an analog voltage proportional to the time width of the rectangular wave 5a is output. Note that (4) H-BYNO pulse 2'b is input as a reset signal to the integrating circuit 10, and the output 10 is
A has a waveform in which an integral operation and a reset operation are sequentially repeated for each horizontal period of the video signal. 3 is a cursor control circuit that controls the position of pupil diameter measurement.
Input O pulse 2b and V-8YNO pulse 2C,
Cursor pulse 3 once per field of video signal
It is configured to output a. VR is a variable resistor that sets the vertical position of the cursor. Reference numeral 40 denotes a sample and hold circuit, which outputs an analog signal 1 from the integrating circuit at each timing of inputting the cursor pulse 3a.
Performs sampling hold of 0a.

Therefore, the sample and hold circuit 4o outputs a diameter analog signal in which an analog voltage corresponding to the diameter of the pupil is sequentially updated and held every field period of the video signal. 50
shows a recorder that records diametric analog signals. 6° is a TV monitor.

FIG. 3 is a detailed diagram of the integrating circuit 10 described in the above configuration. 11 is an operational amplifier, and an inverting input terminal (5) is connected to an integrating circuit. 12 is a switch circuit for controlling charging and non-charging of the integrating circuit, and the output 5a of the binarization circuit is inputted as a signal for controlling the switch. -voc is the power supply of the current source for the integrating circuit. 13
is a switch circuit for integral voltage reset control, and in this case, the signal input for switch control is H-BYNO pulse 2.
b is connected, and the discharging operation of the integrating capacitor 14 is executed at every timing of H-8YNO.

The manner in which the front part of the eye to be examined is imaged with the television camera 1 in the above configuration and the binarization process and integration operation are performed on the output video signal will be described with reference to FIGS. 4 and 5.

In Fig. 4, P indicates the pupil image of the eye to be examined, and when the video signal scanned at the position 13111 is binarized, a rectangular wave 5
It becomes a.

The switch circuit 12 for charge control of the integrating circuit has a configuration that turns on the gate in response to a positive polarity signal, and a rectangular wave 5.
When a is input to the switch circuit 12, the integrating circuit 10 performs an integrating operation (6) for a time TP, and generates a voltage vP at the output 10a. After the voltage vP is generated, if the switch circuits 12 and 1'5 are both in the ON state, the voltage vP is held in the integral output signal 10a. Furthermore, the switch circuit 13 is configured to turn on the gate in response to a negative polarity signal input, and the H-8YNO pulse 2
b is input, and the holding voltage vP is reset every horizontal scanning period.

Next, FIG. 5 shows a case where optical disturbance light is incident on the pupil region of the pupil image P of the eye to be examined.

In FIG. 5, N indicates a reflected image due to disturbance light, and the level of the video signal scanning this position is provided at a much higher level than the signal level of the peripheral pupil area. The rectangular wave obtained by binarizing the video signal scanned at position 3b is as shown in 5a', and in the time period indicated by TH,
The u-fiber polarity of the binarized output is reversed with respect to other pupil regions and output. When the rectangular wave 5a' is input to the switch circuit 12, the 12 gates operate in the OFF state during the TN time period, so the integration circuit 10 interrupts the integration operation during the TN time period, and the product (7 ) The output waveform becomes as shown in 10a'. In this case, the fourth
An integrated voltage that is lower by the voltage indicated by E than the voltage vPK recognized in the state shown in the figure is output. Therefore, if there is a reflected image due to N disturbance light in the pupil image, the voltage E
will occur as a recognition error of the pupil diameter.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pupil diameter measuring device that solves the above-described drawbacks of the conventional example and eliminates the influence of a reflected image of disturbance light mixed into a pupil image of an eye to be examined.

Examples of the present invention will be shown below. FIG. 6 is a block diagram of an embodiment of the present invention. Here, the same reference numerals as in FIG. 2 indicate the same members.

50 is a bistable multivibrator circuit, which uses the rising edge of the output 5a of the binarization circuit as a set input signal;
Input H-BYNO pulse 2b as a reset signal,
A pulse 30a having a phase T shown in FIG. 7 is output. 31
is a bistable multivibrator circuit with a binary output of 5
The falling edge of a is used as a set input signal, and H-5YNO
It is configured to perform reset with a pulse output obtained by gate-processing the output pulse 2b (8) and the binary output 5a, and output a phase T2 pulse 31a shown in FIG. 32 and 33 indicate counter circuits, which are clocked and 32 has a time width T.
, and 33 counts the time width T2. Note that each counter circuit is configured to be reset at each rise timing of the gate signal. ! +5
is a subtraction circuit, and count data of 32 and 33 are respectively input to the two data input terminals, and t3
Execute subtraction processing of the two input data at timing 5. The data resulting from the subtraction processing here is
This corresponds to the time width of TP shown in the figure.

Furthermore, the output data of the subtraction circuit 35 is sent to a memory circuit 36, and is updated and held every time the cursor pulse is outputted from the cursor control circuit 3. The output data of the mesh circuit 36 is further input to a converter 37 and converted into a diameter analog signal.

In the above configuration, the bistable multivibrator circuit 3
In operation 1, the pulse width of T2 is always output no matter what state the output 5a of the binarization circuit changes. Therefore, even if a reflected image due to N disturbance light exists in the pupil image MP, no recognition error of the pupil diameter occurs.

As explained above, by providing the measurement circuit of the pupillometer with two memory circuits, it is possible to accurately measure the size of the pupil even when the reflected image of disturbance light is mixed in the pupil image of the subject's eye. This has the effect of providing a clinically very useful pupillometer, which enables accurate pupil measurement even under various isopic conditions. In addition to the above-mentioned image pickup tube as an imaging means, for example, a two-dimensional or one-dimensional image sensor R-1 can be used.
Also at Sonozumihibuchi IJI.

(10)

[Brief explanation of drawings]

Fig. 1 is a diagram of the front part of the eye to be examined on a TV monitor, Fig. 2 is a block diagram of a conventional example, Fig. 3 is a block diagram of a conventional integrating circuit, and Figs. 4 and 5 are a diagram of a conventional example. FIG. 6 is a configuration diagram of an embodiment of the present invention, and FIG. 7 is an operation waveform diagram. In the figure, P... Pupil image S... Cursor marker BP... Eye to be examined L... Imaging optical system 1... Television camera 2... Synchronization separation circuit 2b... H-8YNO pulse 2 (! -V-8YNOhaAt)<3...Cursor control circuit 4...DC regeneration circuit 5...Binarization circuit 30.31...Bistable multivibrator circuit (1
1) 3233...Counter circuit 34...Clock generation circuit 35...Subtraction circuit 36...Memory circuit 37...D/A converter 50...Recorder applicant Canon Corporation θ2)

Claims (1)

[Scope of Claims] 1. A front part imaging means for imaging the front part of the eye to be examined by electronic scanning, and a binary value for extracting a rectangular wave corresponding to the size of the pupil of the eye to be examined from the output signal of the imaging means. A pupil diameter measuring device that measures the size of the pupil of an eye to be examined from the output of the binarization means, comprising: a pupil area of the eye to be examined imaged by the imaging means from a scanning reference point of the imaging means; a first storage means for storing the time from a scanning start point of the imaging means to a scanning end point of the pupil region of the subject's eye imaged by the imaging means; A pupil diameter (1) characterized in that the size of the pupil of the eye to be examined is measured by measuring the time difference between the output of the second nuclear storage means and the output of the second storage means. measuring device. 2. The first storage means and the second storage means are each constituted by a counter circuit, and further includes means for generating a reference clock for counting of the counter circuit. The pupil diameter measuring device described.