JPH0819519A - Optical measuring device - Google Patents

Abstract

PURPOSE:To measure accurately the position where a light flux reaches by controlling the peak level of light flux to the specified level, and setting the optimum slice level on the basis of the peak level and bottom level. CONSTITUTION:A signal given by a photographing device 4 is fed to a peak sensing member 44, and the lower one of the peaks of index image signals is sensed analogously, and the peak level output is fed to a comparison part 45 and a slice level setting part 47. The comparison part 45 compares the peak level output with the specified level, and the result is fed to a light quantity control part 48 and the slice level setting part 47. The control part 48 adjusts the light quantity of a light source so that the peak level becomes identical to the specified level. The output of a bottom level given from a bottom level sensing part 46 is fed to the slice level setting part 47, and the intermediate level between the peak bottom is fed as the optimum slice level to a rectangular wave conversion part 40a, depending upon that judgement made by the comparison part 45 whether the peak level is identical to the specified level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an optical measuring device having a detection system for guiding a plurality of light beams to a light receiving element and detecting the arrival positions of the plurality of light beams based on the signals of the light receiving elements.

[0002]

2. Description of the Related Art Conventionally, various optical measuring devices having a detection system for guiding a plurality of light beams to a light receiving element and detecting arrival positions of the plurality of light beams based on signals of the light receiving elements are known. In this type of optical measuring device, as an example, a plurality of index images are projected onto the fundus of the eye to be inspected, and the split amount of the index image is measured to measure the eye refractive power based on the split interval. There is something. In this conventional optical measuring device, in order to obtain the split interval of the index image,
The reflected light from the fundus is detected by the detection optical system to form an image on the photoelectric conversion unit, and the photoelectric conversion signal A (see FIG. 1) including the index image from the photoelectric conversion unit is converted into the rectangular wave signal B. The average interval ι of the rectangular wave signal B is obtained from the rising and falling edges, and the spherical power, the astigmatic axis, and the astigmatic power (S, C, A) are measured based on the average interval ι.

[0003]

However, in this conventional optical measuring device, the average interval ι of the rectangular wave signal B changes depending on the setting method of the slice level. Therefore, in the past, ten or more slice levels SL were prepared as shown in FIG. 1, and these were sequentially selected to determine the range in which the rectangular wave signal B can be extracted, and then the slice in the middle of the range. Although level SL is used as the optimum slice level, there are individual differences in the reflectance of the human fundus, and the difference is approximately
If the fundus reflectance is low, it is about
As shown in, the output of the index image signal becomes low, and S /
There is a problem that the N-ratio decreases and the data varies, and the eye refracting power cannot be accurately measured. Further, when the fundus reflectance is high, the two index image signals are overlapped by so-called blurring and the valley between the index image signals rises, and in the slice level SL of 10 or more prepared in advance, the optimum slice level is set. It will be difficult. Further, there is a possibility that the same result as in the case where the projection light amount is insufficient and the fundus reflectance is low due to the attenuation of the light amount due to the secular change of the light source unit of the projection optical system.

Therefore, an object of the present invention is to provide an optical measuring device capable of adjusting a light receiving level to set an optimum slice level and accurately detecting a light beam arrival position.

[0005]

An optical measuring device according to claim 1 of the present invention comprises a light source section, a projection system for projecting a measurement light beam from the light source section toward an object to be measured, and an object to be measured. In an optical measurement device having a detection optical system for guiding a plurality of measurement light beams from an object onto a photoelectric detector, and a detection system for detecting a plurality of light beam arrival positions on the photoelectric detector, a signal from the photoelectric detector A peak detector for detecting the peak level of the light flux, a controller for controlling the peak level to a predetermined level, a bottom level detector for detecting the bottom level of the valley bottoms of the plurality of light fluxes, and the control A slice level setting unit for setting an optimum slice level based on the peak level and the bottom level when the peak level substantially matches a predetermined level.

[0006]

According to the present invention, an appropriate threshold level can be set, and the arrival position of the luminous flux can be accurately measured.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the optical measuring device according to the present invention is applied to an automatic eye refractive power measuring device will be described below with reference to 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 FIG. 3, 1 is an index image projection system, this index image projection system 1 is a plurality of index images formed by irradiating an index plate used for measurement of invisible light of the eye 2 to be measured as an object to be measured. It has the function of projecting on the fundus. Reference numeral 3 denotes a detection optical system, which detects reflected light at the fundus of the eye 2 to be inspected of the index image projected by the index image projection system 1 and connects it to the imaging surface 4a of the imaging device 4 as a photoelectric device. It has a function to make an image. Reference numeral 5 denotes a gaze target projection system, and this gaze target projection system 5 has a function of projecting a gaze target onto the eye 2 to be examined when objective measurement is performed.

The index image projection system 1 includes an LED (Li
The light source 6 emits infrared light, which is invisible light, in order to prevent the pupil 2 from constricting. Infrared light from the light source 6 is condensed by the condenser lens 7
The index plate 8 is irradiated with the light through the, and the index plate 8 is movable in the optical axis x direction. As shown in Fig. 4, the index plate 8 has four slits (two parallel upper and lower slits with the same interval ι).
It is composed of a thin plate 8a having the above, and four deflection prisms 8b to 8e which are in contact with the thin plate 8a and deflect the light beam passing through the slit in a direction perpendicular to the longitudinal direction of the slit.
Two sets of parallel index images composed of invisible light applied to the index plate 8 include reflecting prisms 9 and 10, a relay lens 11, a reflecting prism 12, a half-moon diaphragm 13 having two half-moon shaped apertures, and a slit-shaped hole. A slit prism 14 having 14a, an image rotator 15, an objective lens 16, and a beam splitter 17 pass through the pupil of the eye 2 to be imaged and project it onto the fundus. The half-moon diaphragm 13 is arranged at a position conjugate with the pupil of the eye 2 to be inspected. The image rotator 15 is rotatably arranged with respect to the optical axis y in order to rotate the index image projected on the fundus of the eye 2 in the predetermined meridian direction of the eye, and the rotation angle θ / The index image projected on the fundus of the eye to be examined with respect to 2 is rotated by an angle of θ degrees. The beam splitter 17 has a property of transmitting infrared light and reflecting visible light.

In the detection optical system, the index image reflected on the fundus of the subject's eye 2 has a beam splitter 17, an objective lens 16, an image rotator 15, a slit-shaped hole 14a of a slit prism 14 and a circular opening 18a. Aperture stop 18, relay lens 19, reflection prisms 20, 21, black spot plate 2
2, an image is formed on the imaging surface 4a via the moving lens 23, the reflection mirror 24, and the imaging lens 25. The aperture stop 18 is arranged at a position conjugate with the pupil of the eye to be inspected, and the opening 18a allows only light passing through the pupil of the eye to be inspected. The black dot plate 22 removes the light reflected by the objective lens 16 and harmful to the measurement. Moving lens
23 is movable together with the black dot plate 22 and the index plate 8 along the optical axis Z. The index plate 8 and the imaging surface 4a are always held in a conjugate positional relationship.

Since the index image formed on the image pickup surface 4a passes through the image rotator 15 again, it rotates in the same angle in the opposite direction as the index image projected on the fundus of the eye 2 to be examined. Therefore, the index image formed on the photographing surface 4a is the image rotator 15.
Regardless of the rotation angle, the slits of the index image formed by the index plate 8 have the same orientation and are always held in a fixed 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. The display device 26 displays the slit index image formed on the imaging surface 4a by the photoelectric conversion signal.
(The image reflected by the fundus of the eye 2 to be inspected) is displayed.

In the index image projection system 1 and the detection optical system, when the index plate 8 moves and the index image is focused on the fundus of the eye 2 to be inspected, the moving lens 23 moves to bring the focused state to the imaging surface 4a.
Is imaged. 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, displays the state in which the parallel slit intervals of the upper and lower two sets of the index image focused on the fundus of the eye 2 to be examined are equal (ι2 = ι3) as shown in FIG. indicate. Here, if the projected index image is focused in front of the fundus of the eye 2 to be inspected, the display device 26 displays two sets of parallel slit intervals ι2 <ι3 above and below the index image as shown in FIG. Display the status of. Further, when the projected slit measurement target image is focused on the back of the fundus of the eye 2 to be inspected, the display device 26 reverses the state of FIG. indicate. Thereby, the examiner can always observe the focused state of the index image projected on the fundus of the eye 2 to be inspected.

In the gaze target projection system 5, light from a light source 27 that emits visible light is applied to a gaze target plate 30 by a color correction filter 28 and a condenser lens 29. A gaze target is formed on the gaze target plate 30. The gazing target image formed by the gazing target plate 30 by irradiation of the light from the light source 27 is a collimator lens 31, a moving lens 32, and a reflecting mirror 3.
3, 34, relay lens 35, reflection mirror 36, objective lens 3
The image is projected onto the fundus of the subject's eye 2 through the 7, the reflection mirror 38, and the beam splitter 17. Incidentally, the moving lens 32 is movable along the optical axis, and in the case of objective measurement, it is set to a position where the subject is made to look into a cloud in accordance with the refractive power of the subject's eye,
It removes the accommodation power of the subject's eye and enables accurate objective measurement.

FIG. 7 is a control block diagram of the automatic refractive power measuring apparatus for the eye to be examined. In the figure, the same components as those in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted. In the figure, the imaging device 4 is connected to the display device 26, the light amount adjustment circuit 39, and the rectangular wave conversion unit 40a. The display device 26 has a function of displaying a reflection image of the fundus of the eye to be inspected by the photoelectric conversion signal output from the imaging device 4. Further, the rectangular wave conversion unit 40a has a function of converting the position information of the index image focused on the fundus of the eye to be inspected into a rectangular wave. This rectangular wave converter
The output of 40a is input to the signal processing unit 40, and the signal processing unit 40
Is an index image signal detection unit 40b, a delay circuit 40c, a reference signal formation unit 40d, a timing signal formation unit 40e, an index image position detection unit 40
It consists of f. This signal processing unit 40 is input with the image interval position information of the index image, and is connected to the CPU41 for calculating the refractive power of the eye to be inspected based on this information and displaying it on the display device, The processing unit 40 functions as a detection system that detects a plurality of light beam arrival positions based on signals from the photoelectric detector. A printer 42 for printing out measurement results and a drive control unit 43 are connected to the CPU 41.
The drive controller 43 is a first controller for moving the index plate 8 and the objective lens 23 along the optical axes x and z, respectively.
43a, a second controller 43b for controlling the rotation of the image rotator 15 around the optical axis y, and a third controller 43c for moving the objective lens 32 along the optical axis.
The CPU 41 and the signal processing unit 40 determine the average interval ι of the index images, and the refractive power, the astigmatic axis, and the refractive power (S, C, A) are determined, but since they are not directly related to the present invention, the A detailed description of the measurement is omitted, and then the light intensity adjustment circuit 39
I will explain.

The light quantity adjusting circuit 39 is generally composed of a peak detecting section 44, a comparing section 45, a bottom detecting section 46, a slice level setting section 47, and a light quantity controlling section 48. A photoelectric conversion signal from the image pickup device 4 is input to the peak detection unit 44, and this peak is detected.
As shown in FIGS. 8 and 9, the peak detector 44 has a function of detecting the lower peak of the plurality of index image signals in an analog manner, and the peak level output is compared. It is input to the section 45 and the slice level setting section 47. The comparison unit 45 is
With the function of comparing the peak level output with a predetermined level and outputting the comparison result to the light amount control unit 48, the slice level setting unit 47 outputs the comparison result from the bottom detection unit 46 to the slice level setting unit 47. It has a function of setting the output signal to be acceptable. The light quantity control unit 48 is a comparison unit.
Based on the comparison result of 45, it has a function of adjusting the light amount of the LED 6 so that the peak level coincides with a predetermined level, and the bottom level detection unit 46 uses the valley bottoms of the plurality of index image signals A as the bottom level and is analog. It has the function to detect.
The output of the bottom level is input to the slice level setting unit 47, and the slice level setting unit 47 determines the peak level and the bottom level based on the match result between the peak level output from the comparison unit 45 and the predetermined level. It has a function of outputting the intermediate level between and as the optimum slice level to the rectangular wave conversion unit 40a.

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

First, the peak detector 44 detects the peak level Vp in an analog manner (step S1). Next, it is determined whether or not the difference between the peak level Vp and the predetermined level V is a certain value or more (step S2). As shown in FIG. 8, when the peak level Vp is equal to or higher than the predetermined level V by a constant value ΔV (Vp> V + ΔV), the light amount control unit 48 reduces the light emission amount of the LED 6 and repeats this (step S3). Next,
It is determined whether the difference between the level Vp and the predetermined level V is less than or equal to a certain value (step S4). When the peak level Vp is below a predetermined value ΔV as shown in Fig. 9.
For (Vp <V−ΔV), the light amount control unit 48 increases the light emission amount of the LED 6 (step S5). If the difference between the peak level Vp and the predetermined level V is | Vp-V | <ΔV, the level of the index image signal is determined to be appropriate, and the bottom level Vb is detected next (step S6). The slice level setting unit 47 determines the optimum slice level Vs based on the bottom level Vb and the peak level Vp (step S7). Here, the optimum slice level Vs is obtained by arithmetically averaging the bottom level Vb and the peak level Vp. This optimum slice level Vs is input to the rectangular wave conversion unit 40a, and the rectangular wave conversion unit 40a
Thus, the rectangular wave conversion signal B is generated, the rectangular wave conversion signal B is input to the signal processing unit 40, and the index image signal is detected (step S8). Thereby, the average interval ι of the rectangular wave signal B is obtained, the refractive power is calculated (step S9), and this is repeated until the measurement is completed (step S10), the spherical power, the refractive power, and the astigmatic axis (S, C, A) are measured.

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

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

The slice level setting unit 47 includes a control calculation unit 50.
The slice levels k to a are set by the control of. The index image signal A is sliced by the slice levels k to a. For example, as shown in FIG. 13, when the amount of reflected light from the fundus of the eye to be inspected is small, the output of the index image signal is small, since the index image signal is not sliced at the slice level k, a rectangular wave signal is not output, Counter 49
The outputs of the output terminals Qa and Qb are L and L. Repeat the slice level of this slice level setting unit 47 from k to a
(Step S11). Counter 4 between slice levels k to f
The outputs of the output terminals Qa and Qb of 9 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 output terminal Qb of the counter 49 becomes Qb = L. The output from the output terminal Qa of the counter 49 is between the slice levels d and b.
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 and the output of the output terminal Qb of the counter 49 becomes Qb.
= L (step S12). Of the slice levels k to a,
The slice level d which is the maximum level among the slice levels d to b where the output of the output terminal Qa of the counter 49 is Qa = L and the output terminal Qb = H is regarded as the peak level. Next, the control calculation unit 50 determines whether the output of the counter 49 is between the predetermined level k and the predetermined level j. That is,
First, it is determined whether or not the maximum slice level is within the range of a to i (step S13). Then, it is determined whether or not the maximum slice level is j (step S14). When the maximum slice level is in the range of a to j, the amount of reflected light is insufficient, so the control calculation unit 50 outputs a signal for increasing the amount of light to the light amount control unit 48 (step S1).
Five). As a result, the amount of reflected light increases, and the output level of the index image signal rises 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 are Qa = L and Qb = H. Based on the output of the counter 49, the control calculation section 50 outputs the output terminals Qa, Q of the counter 49 at the slice level k.
It is determined whether or not the output of b is Qa = L and Qb = H (step S16). At the slice level k, when the outputs of the output terminals Qa and Qb of the counter 49 are Qa = L and Qb = H, the reflected light amount is too large, and therefore the control calculation unit 50 moves toward the light amount control unit 48. And outputs a signal so as to reduce the light amount (step S17). As shown in FIG. 15, at the slice level k, the outputs of the output terminals Qa and Qb of the counter 49 are Qa = L,
When Qb = L and the outputs of the output terminals Qa and Qb of the counter 49 at the slice level j are Qa = L and Qb = H,
Assuming that the amount of reflected light is at an appropriate level, the minimum slice level Vm is detected next (step S19). This minimum slice level Vm changes the slice level in order from k to a, and the output of the output terminals Qa and Qb of the counter 49 is Qa = L,
The minimum of Qb = H is detected as the minimum slice level. In Figure 15, the slice level
b is the minimum slice level Vm. The optimum slice level Vs is calculated based on the minimum slice level Vm and the maximum slice level (step S20). The index image signal is sliced by this optimum slice level Vs, and thereby a rectangular wave signal is generated and input to the index image signal detection unit 40b to detect the index image position (step S21). And
The refractive power is calculated, and the result is printed out (step S22). It is determined whether or not the measurement is completed, and this is repeated until the measurement is completed (step S23).

As shown in FIG. 17, a third peak signal may occur in the valleys of the index image signal due to blurring, signal noise, etc. At that time, the output terminals Qa and Qb of the counter 49 are output.
Output becomes Qa = H, Qb = H, and when two peak signals occur in the valley, the output at the output terminals Qa, Qb of the counter 49 becomes Qa =
When L and Qb = L and three peak signals occur in the valley, the output terminals Qa and Qb of the counter 49 become Qa = H and Qb = L, and four peaks in the valley. Counter 49 when signal is generated
Output terminals Qa and Qb output becomes Qa = L, Qb = H, and four pins
When a peak occurs in a valley, the result is the same as when there is no peak in the valley, and this error is included, but it is almost a problem that four or more peaks occur in the valley. I won't.

As described above, in the embodiment, the light amount of the light source is adjusted to change the light receiving level, but the present invention is not limited to this.

[0023]

Since the optical measuring device according to the present invention is constructed as described above, the light receiving level can be adjusted to set the best slice level, and the light beam arrival position can be accurately detected.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining a defect of a conventional technique, and is a diagram showing a relationship between an index image signal and a slice level when a reflectance of a fundus is large.

FIG. 2 is an explanatory diagram for explaining a problem of the conventional technique and is a diagram showing a relationship between an index image signal and a slice level when the reflectance of the fundus is small.

FIG. 3 is a diagram showing an optical system of an eye refractive power measuring device of the optical measuring device according to the present invention.

FIG. 4 is a perspective view showing the configuration of the measurement index plate shown in FIG.

FIG. 5 is a diagram for explaining the interval between the index images and is an explanatory diagram of a focused state.

FIG. 6 is a diagram for explaining the interval between the index images and is an explanatory diagram in a non-focused state.

FIG. 7 is a control block diagram of the first embodiment of the optical measuring device according to the present invention.

FIG. 8 is a diagram showing a relationship between an index image signal and a slice level according to the first example, showing a case where a difference between a peak level and a predetermined level is a certain value or more.

FIG. 9 is a diagram showing a relationship between an index image signal and a slice level according to the first example, showing a case where a difference between a peak level and a predetermined level is a fixed value or less.

FIG. 10 is a flowchart of the optical measuring device shown in the first embodiment.

FIG. 11 is a diagram showing a second embodiment of the optical measuring device according to the present invention and is a circuit diagram thereof.

FIG. 12 is a diagram showing a relationship between an index image signal and a slice level for explaining the operation of the optical measuring device according to the present invention, showing a setting range of the slice level.

FIG. 13 is a diagram showing the relationship between the index image signal and the slice level for explaining the operation of the optical measuring device according to the present invention, and is an explanatory diagram when the amount of reflected light from the eye to be examined is small.

FIG. 14 is a diagram showing the relationship between the index image signal and the slice level for explaining the operation of the optical measuring device according to the present invention, showing the index image signal when the light amount is increased.

FIG. 15 is a diagram showing a relationship between an index image signal and a slice level for explaining the operation of the optical measuring device according to the present invention, showing an index image signal based on an appropriate illumination light amount.

FIG. 16 is a flowchart of the optical measuring device shown in the second embodiment.

FIG. 17 is an explanatory diagram for supplementarily explaining the operation of the second embodiment.

[Explanation of symbols]

 1 ... Projection optical system 2 ... Eye to be measured (object to be measured) 3 ... Detection optical system 4 ... Imaging device (photoelectric detector) 6 ... LED (light source section) 8 ... Index plate (light source section) 40 ... Signal processing section (detection) System) 44 ... Peak detection section 45 ... Comparison section 46 ... Bottom detection section (bottom level detector) 47 ... Slice level setting section 48 ... Light intensity control section 40a ... Square wave conversion section A ... Index image signal B ... Square wave Signals a to k ... Slice level Vs ... Optimal slice level Vp ... Peak level Vb ... Bottom level V ... Predetermined level

Claims (1)

[Claims] 1. A light source unit, a projection system for projecting a measurement light beam from the light source unit toward an object to be measured, and detection optics for guiding a plurality of measurement light beams from the object to be measured onto a photoelectric detector. In an optical measuring device having a system and a detection system for detecting a plurality of light beam arrival positions on a photoelectric detector, a peak detection unit for detecting the peak level of the light beam by a signal from the photoelectric detector, and this peak level is predetermined. A control unit for controlling the level to be a level, a bottom level detector for detecting the bottom level of the valley bottoms of a plurality of light fluxes, and the peak level when the peak level is substantially matched by the control unit. And an slice measuring unit for setting an optimum slice level based on the bottom level.