JPS6232932B2 - - Google Patents

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 that image the front part of the eye to be examined by scanning and measure the size of the pupil region of the eye to be examined using the imaged electrical signals obtained thereby are known.

Conventional devices of this kind extract a rectangular wave corresponding to the size of the pupil of the eye to be examined by binarizing the imaged electrical signal as shown in FIGS. The circuit was configured to operate an integration circuit controlled to a width of , and to measure the diameter and area of the pupil using this output potential. The presence of pupil diameter and area had 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 external light that enters the front part of the eye to be examined.
The field of view seen from the eye to be examined is extremely limited, which has the drawback that clinical application of testing various fixation conditions for the eye to be examined is impossible.

That is, conventionally, the front part of the eye to be examined is photographed on a television monitor as shown in FIG. It is known to detect the pupil diameter from the width of the optically dark area, and then integrate this 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 indicates a television camera, which images the front part of the eye Ep to be examined using an imaging optical system L and outputs a video signal. 2 is a synchronous separation circuit, and 2b is H-
SYNC pulse, 2c shows V-SYNC pulse, respectively. 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. Fix the operating point. 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 appropriately setting the DC slice level, the binarization circuit 5 outputs a rectangular wave 5a corresponding to the horizontal width of the pupil area. Reference numeral 10 denotes an integrating circuit having a configuration to be described later, which inputs 5a as an integral gate signal and outputs a signal 10a containing an analog voltage proportional to the time width of the rectangular wave 5a. In addition,
Integrating circuit 10 receives H-SYNC as a reset signal.
Pulse 2b is input, and output 10a 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 for controlling the position of pupil diameter measurement;
-SYNC pulse 2b and V-SYNC pulse 2c are inputted, and the cursor pulse 3a is outputted once for each field of the video signal. VR is a variable resistor that sets the vertical position of the cursor. Reference numeral 40 indicates a sample and hold circuit, which outputs an analog signal 10 from the integrating circuit at each timing of inputting the cursor pulse 3a.
Perform sampling hold of a. Therefore, the sample and hold circuit 40 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. 5
0 indicates a recorder that records a diameter analog signal. 60 is a television 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 is connected to an integrating circuit. 12 is charging of the integrating circuit,
This is a switch circuit for non-charging control, and the output 5a of the binarization circuit is input as a signal for switch control. -Vcc is the power supply for the current source for the integrating circuit. 13 is a switch circuit for integral voltage reset control; in this case, H-SYNC pulse 2b is connected to the signal input for switch control;
The discharging operation of the integrating capacitor 14 is performed at every timing.

In the above configuration, the front part of the eye to be examined is imaged by the television camera 1, and the output video signal is
Figure 4 shows the execution of the value processing and integration operation.
This will be explained using FIG.

In FIG. 4, P indicates the pupil image of the eye to be examined, and 3
When the video signal scanned at the position b is binarized, it becomes a rectangular wave 5a. The switch circuit 12 for charge control of the integrating circuit is configured to turn on the gate in response to a positive polarity signal input, and when the rectangular wave 5a is input to the switch circuit 12, the integrating circuit 10 changes the time.
Integral operation is performed by Tp, and voltage Vp is applied to output 10a.
occurs. After the voltage Vp is generated, switch circuit 1
2 and 13 are both in the OFF state, the voltage of 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-SYNC 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 naturally provided at a higher level than the signal level of the peripheral pupil area. The video signal scanned at position 3b is
The rectangular wave obtained by value processing looks like 5a',
In the time period indicated by T _N , the recognition 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,
Since the 12 gates operate in the OFF state during the time period T _N , the integrating circuit 10 interrupts the integration operation during the time period T _N , and the integrated output waveform is 1.
It becomes as shown in 0a'. In this case, an integrated voltage that is lower by the voltage indicated by E than the voltage Vp recognized in the state shown in FIG. 4 is output. Therefore, if a reflected image due to N disturbance light exists in the pupil image, the voltage E will be generated as a recognition error of the pupil diameter.

FIG. 6 is a block diagram of an embodiment of the present invention that improves the drawbacks of the conventional example.

The television camera 1, synchronization separation circuit 2, cursor control circuit 3, DC component reproduction circuit 4, binarization circuit 5, sample and hold circuit 40, and recorder 50 are constructed in the same manner as in the conventional example.

15 is a bistable multivibrator circuit which inputs the output 5a of the binarization circuit as a set signal, inputs the H-SYNC pulse 2b as a reset signal, and outputs a reference drive pulse 15a. Reference numeral 20 denotes a sawtooth wave generation circuit having a configuration to be described later, which inputs a reference drive pulse 15a and outputs a reference signal 20a of negative polarity. Reference numeral 25 denotes a sample and hold circuit configured to be described later, which inputs the output 5a of the binarization circuit as a sampling gate signal and performs sampling and holding on the reference signal 20a.

FIG. 7 is a detailed configuration diagram of the sawtooth wave generating circuit 20 and sample hold circuit 25. 2
Reference numeral 1 designates an operational amplifier for the sawtooth wave generating circuit, and an integrating circuit is connected to the inverting input terminal. Reference numeral 22 denotes a sawtooth wave drive switch circuit, which is configured to turn on the gate in response to a negative polarity signal input as a switch control signal.In this case, the switch control signal is a reference drive pulse 15.
a is input. +Vcc is the power supply for the current source for the integrating circuit, and 23 is the integrating capacitor. 26
is an operational amplifier for the sample and hold circuit,
A charging circuit is connected to the inverting input terminal. 27
is a sampling gate switch circuit, which is configured to turn on the gate in response to a positive polarity signal input as a switch control signal; in this case, the output 5a of the binarization circuit is input as the switch control signal. . 28 is a hold capacitor.

With the above configuration, the front part of the eye to be examined is imaged with the television camera 1, and the pupil diameter measurement is performed on the output video signal, with reference to FIG. 8. In FIG. 8, P is the pupil image of the eye to be examined, N is the reflected image due to ambient light, and 5a is the 3
This is the output obtained by binarizing the video signal scanned at position b. Reference drive pulse 15a
Due to the configuration of the bistable multivibrator circuit 15 described above, is reset at the timing of the H-SYNC pulse 2b, and is set at the timing of the first rising edge _t1 of the binarization circuit output 5a to have a positive polarity. Furthermore, 15a is the next H-SYNC pulse 2
It is reset again at b.

During the T _REF period shown in the figure, once the reference drive pulse 15a enters the set state, its positive polarity is maintained regardless of the state of the signal 5a. 20a is a sawtooth wave generation circuit 2
0 output waveform, and the switch circuit 22 outputs T _REF
A sawtooth wave is generated by turning off during the time period. At this time, since 20 constitutes an inverting and integrating circuit, the output 20a becomes a sawtooth wave of negative polarity. Here, the output 20a is a sawtooth wave whose integration operation starts from the scanning start point _t1 of the pupil region of the eye to be examined, and is uniform regardless of the state of the signal of the output 5a of the binarization circuit. Since the integral operation is continuously executed, it can be used as a reference signal for recognizing the diameter of the pupil. 25a is the output waveform of the sample and hold circuit 25. In the sample hold circuit 25, the sampling gate 27 operates at _t1 to _t2 , _t3 to _t4 , and t5 _{to t5} as shown in FIG.
It is turned on during each time period of _t6 .

In each time period above, 25 is the reference signal 20
Execute the sampling operation a. At this time 25
Since it constitutes an inverting amplifier, the reference signal 20a of negative polarity is input, and the output 25a becomes a waveform of positive polarity again. Here, the sampling gate 27 is operated at each time period from t ₂ to _{t 3} and from t ₄ to _{t 5} shown in FIG.
25 temporarily interrupts the sampling operation and enters the hold state, but in the sampling operation to be executed in the next time period,
Output 25a generates a signal that faithfully traces reference signal 20a. When the scanning end point _t6 of the pupil area is reached, the sample hold circuit 2
5 completes the sampling operation and outputs 25
The voltage of Vp is held at a. Here, in the sample and hold circuit 25, no matter how many times the hold state in which the sampling gate 27 is turned off during the period from _t1 to _t6 is repeated, the voltage sampled and held at the timing of _t6 matches Vp.

Therefore, even if there is a reflected image due to N disturbance lights in the pupil image P, no recognition error of the pupil diameter occurs.

The generation of the diameter analog signal by the sample and hold circuit 40 and the operation of the recorder 50 are the same as in the previous embodiment.

In this embodiment, the measurement of the diameter of the pupil has been described, but when measuring the area of the pupil, the measurement can be performed by adding the output potential of the sample and hold circuit 25 described above for the entire vertical synchronization range of the video signal. .

As explained above, by equipping the measuring circuit of the pupillometer with two memory circuits, the size of the pupil can be accurately measured even when the reflected image of disturbance light is mixed into the pupil image of the subject's eye. It becomes possible to
Accurate pupillary measurements can be performed under various fixation conditions, and this has the effect of providing a clinically very useful pupillometer. It is clear that, in addition to the above-mentioned image pickup tube, various image pickup devices such as a two-dimensional or one-dimensional image sensor can be used as the image pickup means. Here, the pupil diameter can be measured using a one-dimensional image sensor, and the pupil area can be measured by optically or mechanically rotating the image sensor.

[Brief explanation of the drawing]

Figure 1 is a diagram of the front part of the eye to be examined on a television monitor, Figure 2 is a configuration diagram of a conventional example, Figure 3 is a configuration diagram of an integrating circuit of a conventional example, and Figures 4 and 5 are conventional examples. FIG. 6 is a configuration diagram of an embodiment of the present invention, FIG. 7 is a configuration diagram of a sawtooth wave generation circuit and a sample hold circuit, and FIG. 8 is an operation waveform diagram. In the figure, P is a pupil image, S is a cursor marker,
Ep is the eye to be examined, L is the imaging optical system, 1 is the television camera, 2 is the synchronization separation circuit, 2b is the H-SYNC pulse, 2c is the V-SYNC pulse, 3 is the cursor control circuit, 4 is the DC component regeneration circuit, 5 is a binarization circuit, 1
5 is a bistable multivibrator circuit, 20 is a sawtooth wave generating circuit, 25 and 40 are sample and hold circuits, and 50 is a recorder.

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 2. 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 sawtooth wave generation circuit that generates a sawtooth wave from a scanning start point of the pupil area of the eye to be examined in a pupil diameter measuring device that has a digitization means and measures the size of the pupil of the eye to be examined from the output of the binarization means. and a sampling and holding circuit that uses the sawtooth wave as an input signal and the output of the binarization means as a gate signal, and detects the size of the pupil from the output of the sampling and holding circuit. measuring device.