JPH0554772B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to an improvement in an ophthalmological instrument with a light intensity adjustment function (prior art). There is a known method in which an index image is projected, the amount of splitting of the index image is measured, and the eye refractive power is measured based on the split interval. In this conventional ophthalmological instrument, in order to determine the split interval of the index image, the reflected light from the fundus of the eye is detected by the detection optical system and imaged on the photoelectric conversion section, and the index image from the photoelectric conversion section is included. Photoelectric conversion signal A
(see Figure 1) is converted into a rectangular wave signal B, the average interval l of the rectangular wave signal B is determined from its rise and fall, and based on the average interval l, the spherical power, astigmatic axis, and astigmatic power ( S, C, A) are assumed.

(Problems to be Solved by the Invention) However, in this conventional ophthalmological instrument, the average interval l of the rectangular wave signal B changes depending on how the slice level is set. Conventionally, a dozen or so slice levels SL are prepared as shown in Figure 1, and these are selected in sequence to determine the range from which the rectangular wave signal B can be extracted. Slice level SL is used as the optimal slice level, but there are individual differences in the reflectance of the human fundus, and the difference is about 3 times, so if the fundus reflectance is low, Figure 2 As shown in FIG. 2, the output of the index image signal becomes low, and the S/N ratio decreases relatively, causing variations in data, and there is a problem that the eye refractive power cannot be measured accurately. In addition, when the fundus reflectance is high, the two index image signals overlap due to so-called blurring, and the valley between the index image signals increases. becomes difficult. Furthermore, there is a risk that the projection light amount is insufficient due to attenuation of the light amount due to aging of the light source section of the projection optical system, resulting in the same result as when the fundus reflectance is low.

(Object of the Invention) Therefore, an object of the present invention is to provide an ophthalmological instrument that can adjust the amount of projected light according to the amount of reflected light from the fundus of the eye to be examined.

(Means for Solving the Problems) The ophthalmological instrument of the present invention is characterized by: a projection optical system that includes a light source and projects a plurality of indicators onto the fundus of the examinee's eye based on light emitted from the light source; a detection optical system that detects reflected light on the fundus of the subject's eye of the index projected by the projection optical system; and a detection optical system that receives the reflected light detected by the detection optical system and includes a plurality of index image signals. a photoelectric conversion unit that outputs a photoelectric conversion signal; a peak detection unit that detects peak levels of the plurality of index image signals; and a peak detection unit that compares the peak level detected by the peak detection unit with a predetermined level and outputs the result. a comparison section; a light amount control section that receives the output of the comparison section and controls the amount of light from the light source so that the peak level becomes a predetermined level; and a bottom level that detects the bottom of the plurality of index image signals as a bottom level. a detection unit; a slice level setting unit that sets an optimal slice level based on the peak level and the bottom level when the peak level output from the comparison unit and the predetermined level substantially match; The apparatus includes: a rectangular wave converting section that converts the photoelectric conversion signal into a rectangular wave based on the level and outputs the rectangular wave signal; and a signal processing section that receives the rectangular wave signal and performs signal processing.

(Function) According to this device, the amount of projected light can be automatically adjusted according to the amount of reflected light from the fundus of the examined eye, and an index image signal of a level suitable for detection can be obtained, and an appropriate threshold can be adjusted. Correct measurements can be made by obtaining accurate visual target image positions based on the level.

(Example) Hereinafter, an example in which an ophthalmological instrument with a light amount adjustment function according to the present invention is applied to an automatic eye refractive power measurement device will be described based on the drawings.

3 to 10 show a first embodiment of the present invention, and FIG. 3 shows an optical system of an automatic eye refractive power measuring device. In the figure, 1 is an index image projection system, and this index image projection system 1 has the function of projecting a plurality of index images formed by irradiating an index plate used for measuring invisible light onto the fundus of the eye 2 to be examined. 3 is a detection optical system, and this detection optical system detects the reflected light of the target image projected by the target image projection system 1 on the fundus of the eye 2 to be examined, and connects it to an imaging device 4 as a photoelectric conversion unit. 5 is a gaze target projection system, and this gaze target projection system 5 has a function of projecting a gaze target onto the subject's eye 2 when performing objective measurement. ing.

The target image projection system 1 includes an LED as a light source.
(Light emitting diode) 6, this light source 6
emits infrared light, which is invisible light, in order to prevent miosis of the eye 2 to be examined. The infrared light from this light source 6 passes through a condenser lens 7 to an index plate 8.
The index plate 8 is movable in the optical axis x direction. As shown in FIG. 4, this indicator plate 8 has a thin plate 8a having four slits (two sets of parallel upper and lower slits with the same interval l) and is in contact with this thin plate 8a, so that the light passing through the slits is directed along the longitudinal direction of the slits. It is composed of four deflection prisms 8b to 8e that deflect the light beam in a direction perpendicular to the direction. Index board 8
Two sets of parallel index images made of invisible light irradiated on the reflection prisms 9 and 10 and the relay lens 1
1, a reflecting prism 12, a half-moon diaphragm 13 having two half-moon-shaped openings, a slit prism 14 having a slit-like hole 14a, and an image rotator 1.
5. The light is projected onto the fundus of the eye 2 through the pupil of the eye 2 by the objective lens 16 and beam splitter 17. Note that the half-moon diaphragm 13 is arranged at a position conjugate with the pupil of the eye 2 to be examined. image rotator 15
is arranged rotatably with respect to the optical axis y in order to rotate the index image projected onto the fundus of the eye to be examined 2 in a predetermined meridian direction of the eye to be examined, and is rotated with respect to the rotation angle θ/2 of the image rotator 15. The index image projected onto the fundus of the examinee's eye is rotated by θ degrees. The beam splitter 17 has a characteristic of transmitting infrared light and reflecting visible light.

In the detection optical system, the index image reflected on the fundus of the eye 2 to be examined is transmitted through the beam splitter 17, the objective lens 16, the image rotator 15, the slit-shaped hole 14a of the slit prism 14, and the aperture having a circular opening 18a. Aperture 18, relay lens 19, reflective prisms 20, 21, black spot plate 22,
Moving lens 23, reflecting mirror 24, imaging lens 2
5, the image is formed on the imaging surface 4a. Note that the aperture stop 18 is arranged at a position conjugate with the pupil of the eye to be examined, and the aperture 18a allows only light that passes through the pupil of the eye to be examined to pass through. The black spot plate 22 removes light reflected by the objective lens 16 that is harmful to the measurement. The movable lens 23 is integrated with the index plate 8 together with the black dot plate 22, and is aligned with the optical axis Z.
It is now possible to move along the The index plate 8 and the imaging surface 4a are always maintained in a conjugate positional relationship.

Since the index image formed on the imaging surface 4a passes through the image rotator 15 again, it
The target image is rotated by the same angle in the opposite direction to the target image projected onto the fundus of the eye. Therefore, the index image formed on this photographing surface 4a is
Regardless of the rotation angle of the image rotator 15, the orientation of the slit of the index image formed by the index plate 8 is always the same and always maintained in a constant direction. On the other hand, the imaging device 4 outputs a photoelectric conversion signal according to the index image formed on the imaging surface 4a. Based on this photoelectric conversion signal, the display device 26 displays a slit index image (an image reflected from the fundus of the eye 2 to be examined) formed on the imaging surface 4a.

In these target image projection system 1 and detection optical system,
When the index plate 8 moves and the index image is focused on the fundus of the eye 2 to be examined, the moving lens 23 moves to form an image of the focused state on the imaging surface 4a. Then, the imaging device 4 emits a photoelectric conversion signal corresponding to the image formation.
The display device 26 to which this photoelectric conversion signal is input,
As shown in FIG. 5, a state is displayed in which the interval between the two pairs of upper and lower parallel slits of the index image focused on the fundus of the eye to be examined 2 is equal (l ₂ =l ₃ ). Here, if the projected index image is focused in front of the fundus of the subject's eye 2, the display device 26 displays two sets of parallel slits, one above and one below, of the index image at an interval l ₂ as shown in FIG. <l Display the status of ₃ . Further, when the projected slit measurement target image is focused behind the fundus of the eye 2 to be examined, the display device 26 displays two parallel slit intervals above and below the index image, contrary to FIG. _{6 .} Display the status of. Thereby, the examiner can always observe the focused state of the index image projected on the fundus of the eye 2 to be examined.

In the gaze target projection system 5 , light from a light source 27 that emits visible light is irradiated onto a gaze target plate 30 through a color correction filter 28 and a condenser lens 29 . A gaze target is formed on the gaze target board 30. A gaze target image formed by the gaze target plate 30 by irradiation of light from the light source 27 is formed by a collimator lens 31, a moving lens 32, and a reflecting mirror 3.
3, 34, relay lens 35, reflective mirror 36,
The light is projected onto the fundus of the eye 2 to be examined via the objective lens 37, reflection mirror 38, and beam splitter 17.
Note that the movable lens 32 is movable along the optical axis, and in the case of objective measurement, is set at a position that causes the subject to see a cloudy vision according to the refractive power of the subject's eye, and adjusts the accommodative power of the subject's eye. removal and enable accurate objective measurements.

FIG. 7 is a control block diagram of the automatic refractive power measuring device for the eye to be examined. Components in the figure that are the same as those in FIG. 3 are designated by the same reference numerals and their explanations will be omitted. In the figure, the imaging device 4 is connected to a display device 26, a light amount adjustment circuit 39, and a rectangular wave converter 40a. The display device 26 has a function of displaying an image reflected by the fundus of the eye to be examined using the photoelectric conversion signal output from the imaging device 4. Further, the rectangular wave converter 40a has a function of converting the position information of the index image focused on the fundus of the eye to be examined into a rectangular wave.
The output of this rectangular wave converter 40a is output from the signal processor 40.
The signal processing section 40 includes an index image signal detection section 40b, a delay circuit 40c, and a reference signal formation section 40.
d, a timing signal forming section 40e, and an index image position detecting section 40f. Image green positional interval information of the index image is input to the signal processing unit 40, and the CPU 4 calculates the refractive power of the eye to be examined based on this information and displays it on the display device.
1 is connected. A printer 42 for printing out measurement results and a drive control section 43 are connected to this CPU 41. Note that the drive control section 4
3, the index plate 8 and the objective lens 23 are aligned with the optical axes x, z.
a first control unit 4 for moving each along the
3a, a second control section 43b for controlling the rotation of the image rotator 15 around the optical axis y, and a third control section 43c for moving the objective lens 32 along the optical axis. These, CPU4
1 and the signal processing unit 40, the average distance l between the index images is determined, and the refractive power, astigmatism axis, and refractive power (S, C,
A) is required, but since it is not directly related to the present invention, the details of the measurement will be omitted.
Next, the light amount adjustment circuit 39 will be explained.

The light amount adjustment circuit 39 is roughly composed of a peak detection section 44 , a comparison section 45 , a bottom detection section 46 , a slice level setting section 47 , and a light amount control section 48 . A photoelectric conversion signal from the imaging device 4 is input to the peak detection section 44 .
As shown in FIGS. 8 and 9, it has a function of detecting the lower peak of a plurality of index image signals in an analog manner, and its peak level output is as follows.
The signal is input to the comparing section 45 and the slice level setting section 47. The comparison unit 45 has a function of comparing the peak level output with a predetermined level and outputting the comparison result to the light amount control unit 48, and also outputs the comparison result to the slice level setting unit 47 so that the slice level setting unit 47 can detect the bottom. It has a function of allowing the output signal from the section 46 to be accepted. The light amount control unit 48 adjusts the peak level to match the predetermined level based on the comparison result of the comparison unit 45.
The bottom level detection section 46 has a function of adjusting the light amount of the LED 6, and a function of detecting the valley bottoms of the plurality of index image signals A as a bottom level in an analog manner. This bottom level output is input to the slice level setting section 47, and the slice level setting section 47 compares the peak level and the bottom level based on the matching result between the peak level output from the comparison section 45 and the predetermined level. It has a function of outputting the intermediate level to the rectangular wave converter 40a as the optimum slice level.

Next, the operation of the eye refractive power measuring device according to this embodiment will be explained with reference to the flowchart shown in FIG.

First, the peak detection section 44 detects the peak level Vp in an analog manner (step S1). Next, it is determined whether the difference between this peak level Vp and the predetermined level V is greater than or equal to a certain value (step
S2). As shown in FIG. 8, when the peak level Vp is more than a certain value ΔV than the predetermined level V
>V+ΔV), the light amount control unit 48 decreases the amount of light emitted from the LED 6 and repeats this (step
S3). Next, the peak level Vp and the predetermined level V
It is determined whether the difference is less than a certain value (step S4). As shown in FIG. 9, when the peak level Vp is less than a certain value ΔV than the predetermined level (Vp<V−ΔV), the light amount control unit 48 controls the LED 6.
The amount of light emitted is increased (step S5). The difference between the peak level Vp and the predetermined level V is |Vp−V|<
If ΔV, it is assumed that the level of the index image signal is appropriate, and then the bottom level Vb is detected (step S6). The slice level setting section 47 is
The optimum slice level Vs is determined based on the bottom level Vb and the peak level Vp (step S7). Here, the optimum slice level Vs is determined by the arithmetic mean of the bottom level Vb and the peak level Vp. This optimal slice level
Vs is input to the rectangular wave converter 40a, and the rectangular wave converter 40a generates a rectangular wave converted signal B,
This rectangular wave converted signal B is input to the signal processing section 40, and index image signal detection is performed (step S8).
As a result, the average interval l of the rectangular wave signal B is determined, the refractive power is calculated (step S9), and this is repeated until the measurement is completed (step S10).
Spherical power, refractive power, and astigmatic axes (S, C, A) are measured.

Next, a second embodiment of the ophthalmological instrument according to the present invention will be described with reference to FIGS. 11 to 16.

In this embodiment, the peak detection section 44 and the bottom detection section 46 are composed of a common counter 49,
The comparison section 45 is composed of a control calculation section 50. The counter 49 receives the rectangular wave signal B from the rectangular wave converter 40a. This counter 49
has output terminals Qa and Qb. Control calculation unit 5
The output of the counter 49 is input to 0.
This control calculation section 50 performs various controls according to the output of the counter 49, and is designated by symbols a to a in FIG. 12.
It has a function of causing the slice level setting section 47 to set a slice level indicated by k, and a function of outputting a light amount control signal to the light amount control section 48.
The counter 49 has its output terminals Qa and Qb controlled by a rectangular wave conversion signal, and its details will be explained together with the operation of this second embodiment.

The slice level setting section 47 is connected to the control calculation section 50.
The slice levels k to a are set by the control. The index image signal A is sliced according to the slice levels k to a. For example, the first
As shown in FIG. 3, when the amount of reflected light from the fundus of the eye to be examined is small, the output of the index image signal is small, and the index image signal is not sliced at slice level k, so no square wave signal is output and the counter 49 The outputs of the output terminals Qa and Qb are L and L. The slice level set by the slice level setting section 47 is repeated from k to a (step S11).
During slice levels k-f, the outputs of the output terminals Qa and Qb of the counter 49 are L and L, and at the slice level e, the output of the output terminal Qa of the counter 49 becomes Qa=H, and the output of the counter 49 terminal
The output of Qb becomes Qb=L, and the slice level d~
During b, the output of the output terminal Qa of the counter 49 is Qa.
=L, the output of the output terminal Qb of the counter 49 becomes Qb=H, and at slice level a, the output of the output terminal Qa of the counter 49 becomes Qa=H,
The output of the output terminal Qb of the counter 49 becomes Qb=L (step S12). Of the slice level ka, the output of the output terminal Qa of the counter 49 is Qa=
L, slice level d~ at which output terminal Qb=H
slice level d, which is the maximum level between b
is considered the peak level. Next, the control calculation section 50 sets the output of this counter 49 to a predetermined level k.
and a predetermined level j.
That is, it is first determined whether the maximum slice level is within the range of a to i (step S13).
Then, it is determined whether the maximum slice level is j (step S14). If the maximum slice level is in the range a to j, the amount of reflected light is insufficient, so the control calculation section 50 outputs a signal to the light amount control section 48 to increase the amount of light (step 15). As a result, the amount of reflected light increases, and the output level of the index image signal increases as shown in FIG. If this output level rises too much, even at slice level k, the outputs of the output terminals Qa and Qb of the counter 49 will be changed to Qa=L, Qb
=H. The control calculation unit 50
At slice level k based on the output of 9,
The outputs of the output terminals Qa and Qb of the counter 49 are Qa=
Determine whether L, Qb=H or not (step
16). At slice level k, counter 49
The outputs of the output terminals Qa and Qb are Qa=L, Qb=H
If so, the amount of reflected light is too large, and the control calculation section 50 outputs a signal to the light amount control section 48 to reduce the amount of light (step S17). As shown in FIG. 15, at slice level k, the output terminals Qa and Qb of the counter 49
The outputs of the counter 49 are Qa=L and Qb=L, and at the slice level j, the output terminals Qa,
If the output of Qb is Qa=L and Qb=H, then
Assuming that the amount of reflected light is at an appropriate level, the next step is to detect the minimum slice level Vm.
S19). This minimum slice level Vm is determined by changing the slice level from k to a in order.
The outputs of output terminals Qa and Qb of 9 are Qa=L, Qb=
The minimum slice level among those resulting in H is detected as the minimum slice level. In Figure 15,
Slice level b is the minimum slice level Vm. The optimal slice level based on this minimum slice level Vm and the maximum slice level
Calculate Vs (step S20). The index image signal is sliced at this optimum slice level Vs, thereby generating a rectangular wave signal, which is input to the index image signal detecting section 40b to detect the index image position (step S21). Then, the refractive power is calculated and the result is printed out (step S22). It is determined whether the measurement is completed or not, and this process is repeated until the measurement is completed (step S23).

Note that, as shown in FIG. 17, a third peak signal may occur in the valley of the index image signal due to blurring, signal noise, etc. In that case, the counter 49
The outputs of the output terminals Qa and Qb of the counter 49 become Qa=H and Qb=H, and when two peak signals occur in the valley, the outputs of the output terminals Qa and Qb of the counter 49 become Qa=H and Qb=H, respectively.
L, Qb=L, and when three peak signals occur in the valley, the output terminals Qa, Qb of the counter 49
When the output of the counter 49 becomes Qa=H and Qb=L, and four peak signals occur in the valley, the outputs of the output terminals Qa and Qb of the counter 49 become Qa=L and Qb=H,
When four peaks occur in a valley, the result is the same as when no peaks occur in the valley, and this error will be included, but there is almost no problem when four or more peaks occur in the valley. .

(Effects of the Invention) As explained above, the ophthalmological instrument according to the present invention includes: a projection optical system that includes a light source section and projects a plurality of indicators onto the fundus of the examinee's eye based on light emitted from the light source section; a detection optical system that detects reflected light on the fundus of the subject's eye of the index projected by the projection optical system; and a detection optical system that receives the reflected light detected by the detection optical system and includes a plurality of index image signals. a photoelectric conversion unit that outputs a photoelectric conversion signal; a peak detection unit that detects peak levels of the plurality of index image signals; and a peak detection unit that compares the peak level detected by the peak detection unit with a predetermined level and outputs the result. a comparison section; a light amount control section that receives the output of the comparison section and controls the amount of light from the light source so that the peak level becomes a predetermined level; and a bottom level that detects the bottom of the plurality of index image signals as a bottom level. a slice level setting unit that sets an optimal slice level based on the peak level and the bottom level when the peak level output from the detection unit and the comparison unit substantially matches the predetermined level; Since the configuration includes a rectangular wave converter that converts the photoelectric conversion signal into a rectangular wave based on the level and outputs the rectangular wave signal, and a signal processing unit that receives the rectangular wave signal and performs signal processing, By appropriately adjusting the amount of projected light based on the amount of reflected light from the subject's eye, an image signal to be evaluated at a level suitable for detection can be obtained, and an accurate target image position can be obtained by setting an appropriate threshold level. This has the effect of allowing accurate measurements to be made.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are explanatory diagrams for explaining the problems of the prior art and are diagrams showing the relationship between the index image signal and the slice level, and FIG. 3 is a diagram for measuring the eye refractive power of the ophthalmological instrument according to the present invention. Diagram showing the optical system of the device, No. 4
The figure is a perspective view showing the structure of the measurement index plate shown in FIG. 3, FIGS. 5 and 6 are diagrams for explaining the intervals between index images, and FIG.
The control block diagrams of the embodiment, FIGS. 8 and 9, are shown in FIG.
FIG. 10 is a flowchart of the ophthalmological instrument according to the first embodiment, and FIGS. 11 to 16 are diagrams showing the relationship between the index image signal and the slice level according to the present invention. 11 is a circuit diagram thereof, and FIGS. 12 to 15 are diagrams showing the relationship between an index image signal and a slice level for explaining the operation of the ophthalmological instrument according to the present invention. ,
FIG. 16 is a flowchart of the ophthalmological instrument shown in the second embodiment, and FIG. 17 is an explanatory diagram for supplementary explanation of the operation of the second embodiment. DESCRIPTION OF SYMBOLS 1... Projection optical system, 2... Eye to be examined, 3... Detection optical system, 4... Imaging device, 6... LED, 8...
Indicator plate, 40...signal processing section, 44...peak detection section, 45...comparison section, 46...bottom detection section,
47...Slice level setting section, 48...Light amount control section, 40a...Square wave conversion section, A...Target image signal, B...Square wave signal, a to k...Slice level, Vs...Optimum slice Level, Vp...Peak level, Vb...Bottom level, V...Predetermined level.

Claims (1)

[Scope of Claims] 1. A projection optical system that includes a light source section and projects a plurality of indices onto the fundus of the subject's eye based on light emitted from the light source section; a detection optical system that detects reflected light on the fundus; a photoelectric conversion unit that receives the reflected light detected by the detection optical system and outputs a photoelectric conversion signal including a plurality of index image signals; a peak detection section that detects peak levels of a plurality of index image signals; a comparison section that compares the peak level detected by the peak detection section with a predetermined level and outputs the result; and a comparison section that receives the output of the comparison section. a light amount control unit that controls the light amount of the light source so that the peak level becomes a predetermined level; a bottom level detection unit that detects the bottom of the plurality of index image signals as a bottom level; a slice level setting unit that sets an optimal slice level based on the peak level and the bottom level when the peak level and the predetermined level substantially match; and converting the photoelectric signal into a rectangular wave based on the slice level. An ophthalmological instrument with a light amount adjustment function, comprising: a rectangular wave conversion unit that outputs a rectangular wave signal; and a signal processing unit that receives the rectangular wave signal and performs signal processing. 2 The peak detection section and the bottom detection section are:
Claim 1, characterized in that it is connected to the photoelectric conversion section to receive a photoelectric conversion signal, and the peak detection section detects the peak of the index image signal in an analog manner. An ophthalmological instrument with a light intensity adjustment function described in . 3. The peak detection section and the bottom detection section are composed of a common counter into which the output of the rectangular wave conversion section is input, and the comparison section sets the slice level and controls the light amount control section. The slice level setting section sequentially changes the slice level upon detection of the peak level or the bottom level, and the counter and the control calculation section cooperate to set the slice level setting section. The ophthalmological instrument with a light amount adjustment function according to claim 1, wherein an optimum slice level is set.