JPS61255635A - Automatic eye refraction force measuring apparatus - 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 (Industrial Application Field) The present invention relates to an automatic eye refractive power measurement device that automatically measures the eye refractive power of an eye to be examined, and more specifically, to The present invention relates to an automatic eye refractive power measurement device that can eliminate as much as possible the measurement error of eye refractive power due to distortion of the video signal.

(Prior Art) Conventionally, in an automatic eye refractive power measurement device, a measurement target image is projected onto the fundus of the eye to be examined using a measurement target image projection optical system, and the measurement target image projected onto the fundus is projected onto the imaging surface of an imaging device. The measurement target image is converted into a video signal, the video signal is outputted to the arithmetic processing means, and the in-focus state of the measurement target image projected onto the fundus of the eye is determined based on the video signal. is detected, and the eye refractive power of the eye to be examined is calculated.

(Problems to be Solved by the Invention) Incidentally, the imaging device has dark charge, and since the amount of dark charge changes due to temperature drift, the video signal is distorted due to the temperature change. In addition, the arithmetic processing circuit is composed of various circuit elements, and since the characteristics of each circuit element itself change depending on the temperature, the arithmetic processing circuit itself is also affected by temperature, causing distortion in the video signal. However, there is a problem in that it is difficult to accurately measure the eye refractive power based on the video signal.

(Object of the Invention) The present invention has been made in consideration of the above circumstances, and its purpose is to provide an automatic eye refractive power measurement device that can eliminate measurement errors due to distortion of video signals as much as possible. It is about providing.

(Means for Solving the Problems) A feature of the automatic eye refractive power measuring device according to the present invention is that the arithmetic processing means calculates a correction amount to correct the measurement error of the eye refractive power based on the distortion of the video signal. The measurement target image projection optical system is provided with a reference pattern image for causing the correction processing circuit to calculate the correction amount at a position approximately conjugate with the imaging surface of the imaging device. This is where a correction pattern is provided.

(Function) In this device, before measuring the ocular refractive power of the eye to be examined by projecting the measurement target image onto the fundus of the eye to be examined using the measurement target image projection optical system, a correction pattern is set in advance on the imaging surface of the imaging device. Form a pattern image. Then, the correction processing circuit calculates the correction amount based on the reference pattern image.

The arithmetic processing means takes this correction amount into account and calculates the eye refractive power based on the video signal corresponding to the measurement target image.

This makes it possible to eliminate measurement errors in eye refractive power due to distortion of the video signal.

(Example) Below, an example of the automatic eye refractive power measuring device according to the present invention will be described.

In FIG. 1, 1 is a measurement target image projection optical system, P
is its measurement optical axis. This measurement target image projection optical system 1 has a target image projection means 2 . The target image projecting means 2 is roughly composed of an LED element 3, a condensing lens 4, and a target plate 5. As shown enlarged in FIG. 2, the target plate 5 has a slit rectangular hole 5.
a to 5d are formed, and four deflection prisms 5e to 5h are attached to these rectangular holes, and the illumination light transmitted through these slit holes is directed by each deflection prism in a direction perpendicular to the longitudinal direction of the slit. The beam is polarized to become the measurement target beam. Its measurement target light is.

A pupil splitting mirror 8 via a projection lens 6 and a total reflection mirror 7
An objective lens 10 placed in front of the eye 9 to be examined
and the pupil splitting mirror 8, the intermediate image Q is converted into a parallel beam of light by the objective lens 10, and is projected toward the eye to be examined.
1, measurement target images 11a, llb, llc,
1id (see FIG. 3). When the measurement target images 11a to lid are in focus in the fundus 11, as shown in FIG. 3, the distance m1 between the upper pair of measurement target images and the distance m8 between the lower pair of target images match. When the target image is not focused on the fundus 11, the intervals m1 and 12 are different. For example, when the measurement target image is focused in front of the fundus 11, as shown in FIG. When the distance m becomes smaller than the distance m2, and when the measurement target image is focused behind the fundus 11, the distance m1 becomes larger than the distance m2 as shown in FIG.

When measuring the refractive power, the distance between the target images 64 is "11".
The eye refractive power is determined by the amount of movement when the target image projection plate 2 is moved until the distance m2 matches the distance m2.

On the measurement optical axis P of the measurement target image projection optical system 1, there is a relay lens 1 along with an objective lens 10 and a pupil splitting mirror 8.
2.13, an imaging lens 14, and an imaging device 15 are provided. The reflected light of the measurement target image formed on the fundus 11 of the eye 9 to be examined is guided again to the objective lens 10, where it is formed as an intermediate image Q, passes through the hole 16 of the pupil splitting mirror 8, and is sent to the relay lens. 12.13, and this relay lens 12.13 has the function of converting the measurement target image into a parallel beam of light. The measurement target image is guided as a parallel light beam by the relay lenses 12 and 13 to the imaging lens 14, and is imaged by the imaging lens 14 on the imaging surface 17 of the imaging device 15. The relay lens 13 is configured to move in conjunction with the movable direction of the target image projecting means 2, so that a conjugate relationship is maintained between the imaging surface 17 of the imaging device 15 and the target plate 5. There is.

The imaging device 15 has a function of outputting a video signal corresponding to the measurement target image to the arithmetic processing means 18 and the television monitor 19. The television monitor 19 has a function of displaying a measurement target image on its display surface 20,
This allows the examiner to visually confirm the displayed images corresponding to the measurement target images shown in FIGS. 3 to 5. This makes it easy to confirm in what condition the subject is undergoing the test. The calculation processing means 18 detects the focusing state based on the video signal and measures the refractive power of the eye 9 to be examined, and includes a video signal extraction circuit 21, a rectangular wave generation circuit 22, a calculation circuit 23, and an output circuit 24. It has an extraction command circuit 25. The video signal extraction circuit 21 receives an extraction command from the extraction command circuit 25, and here.

The extraction command circuit 25 has a function of causing the video signal extraction circuit 21 to extract the video signal corresponding to the scanning line number nz+nz (see FIG. 6). Here, the scanning line number n1 corresponds to a scanning line that crosses the measurement target images 11a and llb,
The scanning line number n2 corresponds to the scanning line that crosses the measurement target image 11c and lid. This scanning line number n
The video signal corresponding to 2 is input to the rectangular wave generation circuit 22. This rectangular wave generation circuit 22 has a function of converting the extracted video signal into a rectangular pulse as shown in FIG. In this FIG. 7, rectangular pulses A and B correspond to measurement target images 11a and llb, and rectangular pulses C and B correspond to measurement target images 11a and llb.
D corresponds to the measurement target image 11c and lid. Moreover, the interval Q1 is the measurement target image 11a, ll
b corresponds to the interval m1, and the interval a2 is the measurement target image l
This corresponds to the interval m2 between ie and lid. Measurement of eye refractive power is performed based on this rectangular pulse A-D,
The arithmetic circuit 23 includes leading edges A of rectangular pulses A, B, C, and D.
1. B, C, D trailing edge Ai.

Signals corresponding to B, , C, , D are input as digital signals, and the interval α1 . Q2 is calculated, and the eye refractive power is calculated based on this.

When the video signal is distorted, the measurement target images 11a and llb are formed on the imaging surface 17 of the imaging device 15.

Although the images 11c and lid are not distorted, the display surface 20 of the television monitor 19 shows distorted measurement target images 11a, flb, llc as shown in FIG.
, lld will be displayed. Arithmetic processing means 18
is provided with a correction processing circuit 26 for correcting measurement errors based on this distortion. The correction processing circuit 26 corrects the reference pattern image 2 formed on the imaging surface 17 of the imaging device 15.
7 (described later), and the reference pattern image 27 is formed by the correction pattern 28. As shown in FIG. 9, the correction pattern 28 has a substantially rectangular transmitting part 29 and a light shielding part 30, and here, the area between the relay lens 12 and the relay lens 13 is conjugate with respect to the imaging surface 17. It is set up like this.

This correction pattern 28 is illuminated by an LED element 31, and the illumination light is projected onto the correction pattern 28 via the pupil splitting mirror 8 and the relay lens 12. A reference pattern image 27 as shown in FIG. 10 is displayed on the display surface 20 of the television monitor 19 when no distortion occurs in the video signal.
is formed, and when the video signal is distorted due to temperature drift, a distorted reference pattern image 27 is formed as shown in FIG. 11. Therefore, before calculating the eye refractive power based on the measurement target images 11a, llb, llc, and lid, the scanning line number n? The amount of correction is measured in advance based on the video signal of the reference pattern image 27 corresponding to nl, and next, the measurement of the amount of correction will be explained.

The correction processing circuit 26 stores in advance as a reference value the width r of the rectangular pulse (see FIG. 12) corresponding to the interval r1 of the reference pattern image 27 in the scanning line direction when no distortion occurs in the video signal. measurement target image 11a,
Before projecting llb, lie, and lid onto the fundus 11 of the eye 9 to be examined, the LED element 31 is turned on to form a reference pattern image 27 on the imaging surface 17. Let the width of the rectangular pulse E obtained by projecting the reference pattern image 27 be r3, and the width of the rectangular pulse F be r4. Here, r3 is the scanning line number n2
is obtained from the video signal corresponding to r3
is obtained by the video signal corresponding to scanning line number n1. Therefore, the correction processing circuit 26 calculates and calculates the difference 1rz-r31-tri-r4t between this width rll)r3 and the interval r0 for each scanning line number n1tn2, and corrects this difference 1r2-r31.1rz-r41. It is temporarily stored as a quantity.

In one or more embodiments, the correction pattern 28 is provided between the relay lenses 12 and 13, but a half mirror is provided between the imaging lens 14 and the imaging device 15,
It is also possible to provide an imaging lens and a correction pattern in the opposite direction of the half mirror so that the illumination light of the correction pattern is reflected by the half mirror and formed as a reference pattern image on the imaging surface.

(Effects of the Invention) As explained above, in the present invention, the arithmetic processing means is provided with a correction processing circuit that calculates the correction amount and corrects the measurement error of the eye refractive power based on the distortion of the video signal. The target image projection optical system includes a position approximately conjugate to the imaging surface of the imaging device.
Since a correction pattern is provided that forms a reference pattern image on the imaging surface of the imaging device for causing the correction processing circuit to calculate the amount of correction, it is possible to eliminate measurement errors due to distortion of the video signal as much as possible. This has the effect of improving the measurement accuracy of refractive power.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the main parts of an automatic eye refractive power measuring device according to the present invention, FIG. 2 is a perspective view showing an enlarged detailed structure of the target plate shown in FIG. 1, and FIGS. 3 to 5 is a diagram showing the display state of the measurement target image shown in FIG. 1, FIG. 6 is a diagram showing the display state of the measurement target image displayed on the display screen of a television monitor, and FIG. 7 is a diagram showing the display state of the measurement target image shown in FIG. 1. Explanatory diagram of a rectangular pulse output from the rectangular wave generation circuit of the means, No. 8
The figure is an explanatory diagram of the measurement target image displayed on the display screen of the TV monitor when distortion occurs in the video signal, Figure 9 is a plan view of the correction pattern shown in Figure 1, and Figure 10 is a diagram showing distortion in the video signal. If this does not occur, TV Figure 10
Figure 1

Claims (1)

[Claims] Measurement target image projection that projects a measurement target image onto the fundus of the eye to be examined, guides the measurement target image projected onto the fundus to an imaging surface of an imaging device to form an image, and outputs a video signal corresponding to the measurement target image. An automatic eye refractive power measuring device comprising an optical system and an arithmetic processing means for detecting a focusing state of a measurement target image projected on the fundus of the eye based on the video signal and calculating the eye refractive power of the eye to be examined. , the arithmetic processing means is provided with a correction processing circuit that calculates a correction amount and corrects a measurement error of eye refractive power based on distortion of the video signal, and the measurement target image projection optical system is provided with Automatic eye refractive power measurement characterized in that a correction pattern for forming a reference pattern image on the imaging surface of the imaging device for causing the correction processing circuit to calculate a correction amount is provided at a position substantially conjugate to the imaging surface. Device.