JPS5994004A - Pupil diameter measuring apparatus - Google Patents

Abstract

PURPOSE:To improve measuring conditions by automatically varying the opening area of a measuring window prior to the measurement to set the measuring window matching the size of the pupil. CONSTITUTION:A pupil section signal 17a is integrated with an integration circuit 18 and an offset voltage Vo is applied to a pupil lateral diameter signal 19a which is memorized and held in a sample hold circuit 19 after amplified with an amplifier 30. The output signal 30a is inputted into a comparator 32 while into a comparator 34 via a code inverter 33. A saw tooth wave 31a is inputted into other input ends of the two respective comparators. When outputs of the comparators 32 and 34 are ANDed with an AND gate 35, a signal 35a has a lateral diameter corresponding to the pupil diameter of the pupil section signal 17a. The same results are obtained with the vertical diameter. Thus, the measuring window is obtained automatically to match the size of the pupil thereby improving measuring conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is an 11-meter pore diameter measuring device that measures the shape and size of the pupil necessary for diagnosing asthenopia, the degree of refractive accommodation, etc., and changes in these factors over time. Regarding.

The size of the pupil varies depending on the eye to be examined, that is, the patient's age, degree of fatigue, symptoms, and surrounding conditions (brightness), and there are cases where the pupil is constricted or mydriatic. It is well known that there is a difference between

Incidentally, the pupil diameter of an average healthy person is within the range of 5 to 9 mm.

Conventionally, as shown in Fig. 1, a pupil diameter measuring device is used.
The front part of the eye to be examined is observed on a TV monitor, and bright and dark output signals are detected for each scanning line (the pupil P becomes a dark part),
Basic line X is the cursor marker.

It is known to measure the pupil diameter by detecting the Y location on the scanning line, and further to measure the pupil area by performing trap integration for each scanning line.

If measurements are taken outside the pupil area, signals harmful to pupil area detection may be captured due to shading due to uneven illumination of the anterior segment of the subject's eye. r&W(
A measurement window (hereinafter referred to as a measurement window) was installed.

However, the area of this measurement window is a predetermined constant size, and there is a difference in measurement conditions between an eye to be examined with a large pupil and an eye to be examined with a small pupil.

That is, in the case of an eye to be examined with a small pupil, a large space is created between the frame of the measurement window and the pupil, and there is a possibility that the above-mentioned harmful signal may be taken in through this space.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pupil diameter measuring device that solves the above-mentioned drawbacks.

In order to achieve this object, the present invention is characterized in that, before measurement, the 1 m area (size) of the measurement window is automatically changed in advance to set a measurement window that matches the size of the pupil.

In order to set a measurement window that matches the pupil size of the eye to be examined using the present invention, several fields of scanning are required before measurement, but the time required for this is extremely short and practically It does not interfere with measurement in any way.

Hereinafter, embodiments will be described according to the drawings.

FIG. 2 is a block diagram of an embodiment of the present invention. In the figure, E is the eye to be examined, 9 is the objective lens, 10 is the television camera, 10IL is the video signal from the television camera 10, 11 is the amplifier that amplifies the video signal 10a, 11a is the signal passed through the amplifier 11, 12 is the anterior segment of the eye A television monitor for observation, 15 a sync separation circuit that generates a horizontal sync signal and a vertical sync signal from a video signal, 15a a horizontal sync signal, 15b a vertical sync signal, 14 a clamp circuit that roughly ramps the video signal 10a, 15 a clamp 15a is a second inverting and binarizing circuit that inverts and binarizes the video signal clamped by the circuit 14;
Value conversion signal, 16 is a measurement window circuit that limits the measurement range, 16
a is a measurement window pulse; 17 is an integration circuit having two integrators; 17 is a transverse diameter measurement P in which the binarized signal 15a and the measurement window pulse 16& are both controlled by a signal 17& for extracting the Htgh level portion; 19 is an integration circuit A sample hold circuit holds and stores the integration result at 1B, 19 to 19b are a pupil longitudinal diameter signal and a pupil longitudinal diameter signal, respectively, 20 is a sample hold timing generation circuit that generates the sample hold timing of the sample hold circuit 19, and 20a is a sample A hold timing circuit 21 is a display circuit that performs analog-to-digital conversion of the measured value held by the sample hold circuit 19 and displays the result.

The video signal 10 & outputted from the television camera 10 is a signal as shown in FIG. input to the clamp circuit 14.

The video signal which has been amplified twice by the amplifier 11 is received by a television monitor 12 for viewing. The synchronization separation circuit 16 generates + for the horizontal synchronization signal 13a and the vertical synchronization signal 15, which are used as control signals for various circuits in the next stage and thereafter. Now, the video signal 10 & inputted to the clamp circuit 14 is 2-amplified at its lowest level and inputted to the inversion binarization circuit 15 . Here, the video signal of FIG. 6 10a is sliced at a constant DC level L and binary quantization is performed. As a result, there is a 51st bad guy. This binary signal 15a and the measurement window circuit 16''
The measurement window pulse i6a generated by C is connected to the A N D gate 17.
゛The pupil area in the binarized signal after CAND, that is, Shinzuki P
Extract only. This situation is shown in FIGS. 16a and 17a. The integration circuit 1B executes and stops integrating a constant DC voltage according to the opening and closing of the integration gate, but for horizontal 1-view measurement, the pupil line signal acts as the opening/closing of this gate.
Regarding vertical diameter measurement, the gate opening/closing I (acts as a pulse. As a result, opening/closing) is obtained by taking the generation I pulse of the vertical base line Y, which is a cursor marker, and the A and ND of the pupil line signals.
The length of the curve, that is, the level of the pupil line signal is Hi.
gh). The integral output number is stored and held in the sample hold circuit 19 of the pulse 20a.
The diameter signal 19b is converted from analog to digital by a display circuit 21, and the result is displayed digitally.

Now, the variable measurement window, which is a feature of the present invention, will be explained in detail with reference to FIGS. 4 and 5.

FIG. 4 shows a configuration example of a measurement window circuit corresponding to FIG. 3 16a. Inputs are four signals: a horizontal synchronizing signal 15a and a vertical synchronizing signal 19b. The circuit shown in the figure consists of two similar circuits and a circuit for displaying the reference position of the measurement window on the observation television monitor. The circuit indicated by +5 is the circuit that controls the measurement window in the horizontal radial direction, and the ones indicated by 40 to 45 are the circuits that control the measurement window in the vertical radial direction. I will call it. Finally, the code is 61°42,,! 56 to 40 constitute a reference position display circuit. Here, the horizontal window control circuit and the vertical window control circuit have circuit configurations that differ only in that their inputs are a vertical synchronization signal 15b for the horizontal synchronization signal 15aK, and a pupil 4 [outgoing signal 19b] for the pupil horizontal diameter signal 194K. Since the above are exactly the same, the side window control circuit and the reference position display circuit will be explained hereafter. 50 is the pupil transverse diameter signal 19 & 1/
an amplifier that doubles the amplification and applies a predetermined offset voltage, 6
0a is its output, 61 is a sawtooth wave generator that is reset every time a horizontal synchronization signal is input, 51m is its output, 52 is a comparator, 521 is its output, 35 is a sign inverter that inverts the sign of the output 50a of the amplifier 50. 34 is a comparator, 54& is its output, and 55 is a comparator 32. An AND gate that ANDs the outputs 52a and 34a of the comparator 64, 551L is its output, 56 is a comparator that generates the timing of the reference line Y, 57 is a monostable multivibrator, and 68 is a comparator that generates the timing of the reference @X. , 69 is a scanning line extraction circuit, 40 is an OR game), and 40a is its output.

Here, the pupil transverse diameter signal 191L is an output signal that is obtained by integrating the pupil portion signal 17a in the integrating circuit 18 and stored and held in the sample hold circuit 19.

The pupil transverse diameter signal 19a is converted to 1/2 f+! by the amplifier 60. r, and a predetermined offset voltage Vo is applied thereto. This state is shown in FIG. 5, 19a and 30a.

Further, one of these signals is input to a comparator 52, and the other signal is inverted by a sign inverter '54 and input to the comparator 54. The other inputs of these two comparators are both generated by a sawtooth wave generator 51. This is a sawtooth wave 51&. As shown in FIG. 551a, this sawtooth wave 51a has the same period as the horizontal synchronizing signal, and is set to distribute the voltage equally around O volts. Furthermore, the time constant of the sawtooth wave generating circuit 51 is set to be equal to or greater than the time constant of the integrating circuit 1B shown in FIG. Now, the polarities of the input terminals of the comparators 52 and 34 are selected as shown in FIG. 4, and the outputs of the respective comparators are ANDed by the A N D gate 55.

52a, ! A series of relationships as shown in 141L, 55& are obtained.

It is understood that the width signal 55a has a width corresponding to the pupil diameter of the pupil signal 17a. The comparator 56 outputs Htg when the sawtooth wave 51a passes through 0.
h. At the rising edge of this signal, the monostable I/L divisor 67 outputs an extremely short pulse. This pulse is the pulse that generates the reference line Y. On the other hand, the scanning line extraction circuit 39 receives the sawtooth wave 42m in the same manner as the previous 51m and 56, and the comparator 58 receives the sawtooth wave 42m.
Htgh h for the time corresponding to the next scanning line of the scanning line being traced when the signal output from rises
Outputs a pulse that looks like this. This I (Rus is the reference line
This is a pulse that generates These two I(rus outputs) are ORed by an OR gate 40 and the output 40'a is
When mixed with Fig. 11m, a crosshair is imaged on the observation television monitor. During measurement, the pupil is positioned so that the intersection of the crosshairs matches the center of the pupil.

FIG. 6 illustrates a process in which a measurement window suitable for the size of the pupil of the eye to be examined is formed on the television monitor.

The outer rectangle is the television monitor screen, the black circle in the center with diameter P is the pupil, the crosshair on the screen is the reference line, the vertical line is the reference gland Y1, and the horizontal line is the reference line X.

The hatched area in Figure 6(a) is assumed to contain noise with the same brightness as the pupil, and when viewed on the video signal, the levels of this noise and the pupil are exactly the same. It is assumed that the difference cannot be determined at all based on the signal level, and only the positional information differs.

The area between the square indicated by the broken line and the pupil in FIG. 6(,) is a noise-free area, and the conditions for this area will be described later.

FIG. 6(b) is the screen of the first field. Here, the solid line indicates the frame of the measurement window in this state.

Regarding the window frame, see @7 in Figure 1 for each state in Figure 6 (b
) to (f) are shown correspondingly to K, and the final measurement window is as shown in FIG. 7(, ).

Here, FIG. 7(,) is an enlarged view of the measurement window in FIG. 6(f). In FIG. 6(b), D is the amount of offset corresponding to VoK in FIG. 5 501.

From now on, in order to make the figures easier to read, only the noise that is inside the measurement window and is actually measured is hatched, but noise exists in all figures as set in Figure 6 ta+. .

In Fig. 6(b), the scanning line traces from the top of the screen, but until it reaches a noise-free area, the integration circuit 1B in Fig. 2 integrates over the entire screen width Xo, so the integral There is no change in the output, so there is no change in the side window frame either. Once the scanning line traces a noise-free area, the previous integrated output becomes smaller by the length of Xs. When the width of the dark area in the scanning direction is measured using the scanning lines consisting of these, this width is distributed symmetrically around the center of the screen and used as the measurement width for the next scanning line, and this is done sequentially. Ru.

The horizontal window frame shrinks, and as a result, Xz- on both sides of the reference line Y.
A horizontal window frame with a size of 1-D is set.

Furthermore, at the time of the next trace, the integrating circuit is in this state as shown in FIG. 8. That is, FIG. 8 is a time chart and an operation waveform diagram when the horizontal scanning line is traced from the upper side of the square indicated by the broken line to the sixth line in FIG. 6(b), and these correspond to those in FIG. 5. Note 171
It is a noise having the same brightness as the N Lt pupil.

In this way, when the horizontal window frame eventually reaches a noise-free region, the integral output becomes zero, resulting in a window frame in which only the offset is on both sides of the reference line Y. When this thin horizontal window frame reaches the upper end of the pupil, the integral output increases again,
During the next trace, a window frame with a length equivalent to half of that output plus the offset measurement will be created on both sides of the reference line Y, and from now on, if you scan to the bottom of the screen in the same way. A measurement window as shown in FIG. 7(b) is created.

FIG. 6(0) is the screen of the second field. Using the integral output information along the reference line Y obtained in the first field, a vertical window frame is formed using the center axis as the horizontal window, and the window frame is updated for each field.

That is, the width of the dark area in the reference 13 Y direction in the previous field is formed, and this width is divided symmetrically around the center of the screen and used as the measured value in the next field.

In other words, the horizontal window frame is updated for each scanning line, whereas the vertical window frame is updated for each field. Figure 6 f
n+8) are the 5th field and the 6th field, respectively.

Figure 6(f) is the 7th field, and this is the final shape of the measurement window 71j, which is an enlarged view of Figure 7 (+al force).One offset scale was applied to the outside of the pupil. It becomes a measurement window for shape. In order for the measurement window to shrink as described above, it is necessary to draw a donut-shaped area around the pupil that is free from harmful noise, and furthermore, it is necessary to draw a donut-shaped area around the pupil that is free from harmful noise. The condition for not mixing is that the distance from the pupil edge to the nearest harmful noise area is offset LD, J1. This is a big thing.

Note that the measurement window set in this way is not fixed; if the area of the pupil a changes, a measurement window that is widened by D is set as shown in Fig. 6 (sequentially from the stage of fj, offset to the outside of the pupil). I will do it.

FIG. 9 is a schematic diagram of the manual measurement window control circuit. 15 in figure
is a horizontal synchronization signal, 15b is a vertical synchronization signal, and 61 is a variable directivity signal for side window control. ie 'tit pressure source, 62 is an amplifier that doubles the output of 61, 62 is a variable DC voltage source for controlling the vertical window, 63 is an amplifier that doubles the output of 62, 60 is shown in FIG. '51γ40°42-47 II
16a is the measurement window pulse which is the output of the measurement window circuit, and 40a is the output of the reference position display circuit.

The input horizontal synchronizing signal 15a and vertical synchronizing signal 15b have exactly the same function as the above-mentioned automatic measurement window control circuit.

When the variable DC voltage sources 61,65 are manually adjusted, the voltages generated therein are amplified twice by amplifiers 62,64 and input into the circuit 60, respectively. The circuit 60 operates exactly the same as the automatic measurement window circuit described above, and generates the measurement window pulse 16.
1L and output 40a of the reference position display circuit. Thereby, the measurement window formed on the screen can be manually enlarged or reduced in both the vertical and horizontal directions.

As explained above, by having the function of changing the aperture area of the measurement window, it is not affected by individual differences in the eye being examined, and especially when automatically controlling the measurement window, it is possible to measure Since the window changes, it is possible to effectively remove portions unnecessary for measurement and harmful noise in the binary signal without being affected by constriction or mydriasis, and to obtain optimal measurement conditions.

In addition to the above-mentioned image pickup tube, various types of imaging means may be used, such as a two-dimensional or one-dimensional image sensor. FIG. Figure 3 is a time chart showing signals and operation waveform diagrams of each part in Figure 2, Δ Figure 4 is a diagram of the first drawing example of the measurement window circuit, Figure 5 is the diagram of the fourth example. Figures 6 (&) to (f), Figure 7 (, 1 to (f) are diagrams showing the process of forming the measurement window, Figure 8 is a time chart showing the signals and operating waveforms of each part of the diagram related to the change in the horizontal window frame for Figure 6(b), △ Figure 9 is a diagram of the second +: # example of the measurement window circuit, in the figure, W
are measurement windows, X and Y are reference lines as cursor markers, P is a pupil image, E is an eye to be examined, 9 is an objective lens, 10 is a television camera, 12 is a television monitor, 1!1 is a vertical synchronization signal, 1
3a is a horizontal synchronization signal, 16b is a vertical synchronization signal, 15 is an inversion binarization circuit, 16 is a measurement window circuit, 17 is an A N I)
gate, 18 is an integration circuit, 50 is an amplifier that adds an offset voltage, 61A sawtooth wave generator, 52, 54, and 56 are comparators, 65): i AN D ri-), 3
7 Lj Rawanhot Multi High Break, 61.65
is the voltage source of the variable surface 61e 〇W 1qα :35a (d) (e) (C) (a) -JOtsu- 1 6pu 1

Claims (1)

[Scope of Claims] 1. A front part Wk image means for imaging the front part of the eye to be examined by electronic scanning, a measurement window means for limiting the a1° measurement range, and a size of the pupil of the eye to be examined from the output signal of the imaging means. In a pupil diameter measuring device that has a binarization means for extracting a rectangular wave corresponding to a rectangular wave, and measures the size of the pupil of an eye to be examined from the output of the binarization means, the output of the binarization means is integrated. a holding means for storing and storing the output of the means; a means for applying an offset amount to the output of the means; and a means for automatically setting a measurement window larger than the pupil of the eye to be examined by a predetermined amount from the offset fl; A pupil diameter measuring device characterized in that the size of the measurement window is variable depending on the pupil of the eye. 2. The pupil diameter measuring device according to claim 1, comprising means for externally adjusting the size of the measurement window.