JP2001112716A - Ophthalmic examination apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the accuracy of measuring vascular diameters and to apply stable tracking by accurately detecting a specific point during the calculation of a vascular diameter. SOLUTION: A quantity of deviation is input to an illuminating light quantity control means 50 from a vascular position computing means 76 and, when the quantity of deviation is smaller than an allowable value, the control means 50 determines that tracking is applied, and outputs a reflected light distribution sensing start signal to a reflected light distribution sensing means 48. The reflected light distribution sensing means 48 senses an output difference (reflected light distribution) between before and after the peak of a waveform, and outputs the result to the illuminating light quantity control means 50, which in turn compares the result to a set value. When the result is equal to or greater than the set value, a signal is output to an illuminating light distribution changing means 51 so that the distribution of quantities of light of a rectangular tracking indicator T irradiated to the fundus oculi Ea varies.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ophthalmic examination apparatus for examining blood vessels on the fundus.

[0002]

2. Description of the Related Art Conventionally, when measuring the blood flow rate of blood vessels in the fundus oculi, for example, a fluorescent agent is injected intravenously, a video is taken of how the fluorescent agent flows through the blood vessel, and how much the fluorescent agent moves per unit time. To measure blood flow velocity. In addition, a method of measuring the blood vessel diameter from a fundus photograph to know the blood flow is known. However, at present, a desired blood vessel is automatically tracked and irradiated with laser light, a blood flow velocity is obtained from the Doppler signal, and an area including a target blood vessel is imaged when performing automatic tracking, and the image signal is used. An apparatus for obtaining the diameter of a blood vessel is proposed in Japanese Patent Laid-Open Publication No. Hei 8-206077.

In these ophthalmic apparatuses, a one-dimensional CCD is used as a light receiving means for receiving a tracking light flux reflected from the fundus, and a waveform processing of a blood vessel image signal is performed to shift a tracking center position and a blood vessel image position. Tracking is performed by calculating the amount. An algorithm for calculating the deviation between the tracking center position and the position of the blood vessel image by performing waveform processing on the blood vessel image signal is disclosed in Japanese Patent Laid-Open No. Hei 10-234670.
An example is disclosed in Japanese Patent Application Laid-Open Publication No. H11-15095. In addition, a method of calculating a blood vessel diameter by extracting a singular point from a blood vessel image signal is also known.

[0004]

However, in the above-mentioned conventional example, when the brightness is the same at the left and right peripheral portions of the blood vessel portion, it is possible to correctly detect the singular point detected when calculating the blood vessel diameter. However, due to the difference in brightness between the blood vessel part and the blood vessel peripheral part, if there is a difference in the reflected light distribution in the peripheral part of the blood vessel image, it may not be possible to detect an accurate point when detecting a singular point. As a result, there is a problem that a correct blood vessel diameter cannot be calculated.

[0005] Regarding tracking, if the reflected light distribution is uniform, there is no problem if the peak hold waveform and the inverted waveform are added. In the case of a bright image, when the same addition processing is performed, signals corresponding to differences in left and right brightness remain, resulting in a problem that tracking stability is impaired.

An object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide an ophthalmologic examination apparatus that correctly detects a singular point detected when calculating a blood vessel diameter, improves the accuracy of blood vessel diameter measurement, and performs stable tracking.

[0007]

According to the present invention, there is provided an ophthalmic examination apparatus for illuminating an area including a specific blood vessel as a target, and an image of the blood vessel and outputting a video signal. An ophthalmic examination apparatus comprising: an imaging unit; an automatic tracking unit that performs automatic tracking of a blood vessel based on a processing result of an output signal of the imaging unit; and a blood vessel diameter calculation unit that calculates a blood vessel diameter of a blood vessel. A reflection distribution detecting unit that detects a distribution of reflected light in a region including a blood vessel from the output signal and detects an output value of a boundary point with the blood vessel, and a light amount distribution position on the fundus of the illumination light provided in the illumination unit. An illumination light distribution changing unit to be changed and a control unit for controlling the illumination light distribution are provided, and when automatic tracking is started by the automatic tracking unit, the control unit calculates a value calculated from a result of the reflection distribution detection unit. But Controlling the illumination intensity distribution changing means to be smaller than the value, and controls to start the vascular diameter calculation by reducing the said vessel diameter calculating means than the setting value.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the illustrated embodiment. FIG. 1 shows a configuration diagram of a fundus blood flow meter according to an embodiment. A condenser lens 3 is provided on an illumination optical path from an observation light source 1 composed of a tungsten lamp or the like that emits white light to an objective lens 2 facing the eye E. For example, a field lens 4 with a band-pass filter that transmits only light in the yellow range, a ring slit 5 provided at a position substantially conjugate with the pupil Ep of the eye E, and a position substantially conjugate with the crystalline lens of the eye E A light-shielding member 6 provided, a relay lens 7, a transmissive liquid crystal plate 8, which is a fixation target display element movable along an optical path, a relay lens 9, and a light-shielding member provided conjugate with the vicinity of the cornea of the eye E to be examined. 10, a perforated mirror 11, and a band-pass mirror 12 that transmits light in the yellow range and almost reflects other light beams are sequentially arranged.

A fundus observation optical system is provided behind the perforated mirror 11, and includes a focus lens 13, a relay lens 14, a scale plate 15, and an optical path switching mirror that can be inserted into and removed from the optical path. 16, eyepiece 17
Are sequentially arranged to reach the examiner's eye e. When the optical path switching mirror 16 is inserted in the optical path, a television relay lens 18 and a CCD camera 19
The output of the CCD camera 19 is connected to a liquid crystal monitor 20.

An image rotator 21 and a double-side polished galvanometric mirror 22 having a rotation axis perpendicular to the plane of the drawing are arranged on the optical path in the reflection direction of the bandpass mirror 12, and a lower reflection surface 22a of the galvanometric mirror 22 is provided. The second focus lens 23 movable along the optical path is disposed in the reflection direction of, and the lens 24 and the focus unit 25 movable in the optical path are disposed in the reflection direction of the upper reflection surface 22b. . Note that the lens 2
4 has a conjugate relationship with the pupil of the eye E to be examined, and a galvanometric mirror 22 is disposed on this focal plane.

An optical path length compensating meniscus 26, a black spot plate 27 having a light-shielding portion in the optical path, and a concave mirror 28 are arranged behind the galvanometric mirror 22, and reflected by the lower reflecting surface 22a of the galvanometric mirror 22. A relay optical system that guides a light beam that passes through without being guided to the upper reflecting surface 22b of the galvanometric mirror 22 is configured. In addition,
The meniscus 26 for optical path length correction is a galvanometric mirror 2
The positions of the upper reflection surface 22b and the lower reflection surface 22a are used to correct the displacement in the vertical direction in the drawing caused by the thickness of the mirror, and act only in the optical path toward the image rotator 21.

In the focus unit 25, a dichroic mirror 29 and a condenser lens 30 are sequentially arranged on the same optical path as the lens 24, and a mask 31 and a movable mirror 3 are arranged on the optical path in the direction of reflection of the dichroic mirror 29.
2 are arranged, and the focus unit 25 can be integrally moved in a direction indicated by an arrow.

A fixed mirror 33 and an optical path switching mirror 34 that can be retracted from the optical path are arranged in parallel on the optical path in the incident direction of the lens 30. A collimator lens 35 is provided on the optical path in the incident direction of the optical path switching mirror 34. A measuring laser diode 36 that emits coherent, for example, red light is arranged. Further, on the optical path in the incident direction of the movable mirror 32, a beam expander 37 composed of a cylindrical lens or the like, and a tracking light source 38 that emits, for example, green light different from other high-luminance light sources are arranged.

A second focus lens 23, a dichroic mirror 39, a field lens 40, a magnifying lens 41, a one-dimensional CCD 42 with an image intensifier are provided on the optical path in the reflection direction of the lower reflection surface 22a of the galvanometric mirror 22. Are sequentially arranged to form a blood vessel detection system.

On the optical path in the reflection direction of the dichroic mirror 39, an imaging lens 43, a confocal stop 44, a mirror pair 45a provided substantially conjugate with the pupil of the eye E to be examined,
45b is disposed, and photomultipliers 46a and 46b are disposed in the reflection directions of the mirror pairs 45a and 45b, respectively, to form a measuring light receiving optical system. For convenience of illustration, all the optical paths are shown on the same plane, but the reflected optical paths of the mirror pairs 45a and 45b, the tracking light source 3
The measurement optical path in the emission direction 8 and the optical path from the laser diode 36 to the mask 31 are orthogonal to the paper surface.

Further, a system control unit 47 for controlling the entire apparatus is provided.
Is connected to the output of the one-dimensional CCD 42 and the outputs of the photomultipliers 46a and 46b. The output of the system controller 47 is connected to the galvanometric mirror 2
2. The optical path switching mirror 34, the reflection distribution detecting means 48, and the blood vessel diameter calculating means 49 are connected to each other. The output of the reflection distribution detecting means 48 is sequentially connected to the illumination light quantity control means 50, the illumination light distribution changing means 51, and the movable mirror 32.

FIG. 2 mainly shows a configuration diagram of the system control unit 47. The output of the one-dimensional CCD 42 is connected to a sample hold circuit 61 via an amplifier 60, and the output of the sample hold circuit 61 is a peak hold circuit 62 or an inversion circuit. It is connected to an addition circuit 64 via a buffer 63. The output of the addition circuit 64 is a low pass filter 65, a peak hold circuit 66, a sample hold circuit 67,
The D converters 68 are sequentially connected. The outputs of the sample hold circuit 61 and the A / D converter 68 are passed through a bus line to the I / O 69, the memory 70, the MPU 71,
Each is connected to a D / A converter 72. The output of the D / A converter 72 is sequentially connected to a dividing circuit 73, a differentiating circuit 74, a zero-cross comparing circuit 75, a blood vessel position calculating means 76, a galvanometric mirror control circuit 77, and the galvanometric mirror 22.

Further, the output of the one-dimensional CCD 42 is sequentially connected to a timing generator 78, a clock circuit 79, and an MPU 71, and the output of the timing generator 78 is sample-hold circuits 61, 67, and peak-hold circuits 62, 6.
6 and I / O 69 respectively. And I
The output of / O69 is connected to the optical path switching mirror 34,
The output of the input unit 80 is connected to / O69. The output of the I / O 69 is connected to the blood vessel position calculation means 76 and the illumination light quantity control means 50 in this order. Further, the output of the sample and hold circuit 61 is connected to each of the reflection distribution detecting means 48 and the blood vessel diameter calculating means 49, and the output of the reflection distribution detecting means 49 is transmitted to the illumination light quantity control means 50, the illumination light distribution changing means 51, and the movable mirror 32. The output of the illumination light quantity control means 50 is connected to the blood vessel diameter calculation means 49.

An amplifier 60, a sample hold circuit 61,
Peak hold circuit 62, inversion buffer 63, adder circuit 64, low-pass filter 65, peak hold circuit 6
6. The blood vessel site extraction unit 81 is constituted by the sample and hold circuit 67, the division circuit 73, and the differentiation circuit 74. The peak hold circuit 66 and the sample hold circuit 6
7. The ACG unit 82 is constituted by the division circuit 73,
D converter 68, I / O 69, memory 70, MPU 71,
The D / A converter 72 constitutes a processing condition determining unit 83. The zero-crossing comparison circuit 75, the blood vessel position calculation means 76, and the galvanomirror control circuit 77 constitute an automatic tracking control section 84.

FIG. 3 shows the arrangement of each light beam on the pupil Ep of the eye E to be examined. I denotes an image of the ring slit 5 in an area illuminated by yellow illumination light, O denotes a fundus observation light beam and a perforated mirror 11 V is a measurement / blood vessel received light beam, and the upper and lower reflecting surfaces 22a, 22b of the galvanometric mirror 22
Are the images of the effective portions, and Da and Db are the two measurement light-receiving beams, which are the images of the mirror pairs 45a and 45b, respectively. Also, P
2, P2 'denotes the incident position of the measuring light, and the optical path switching mirror 34
The position M of the measurement light selected by switching the position is indicated by a dotted line.
Is an image of the lower reflective surface 22a.

The white light emitted from the observation light source 1 passes through the condenser lens 3, and only the yellow wavelength light is transmitted by the field lens 4 with the band pass filter, passes through the ring slit 5, the light shielding member 6, the relay lens 7, The transmissive liquid crystal 8 is illuminated from behind, and a relay lens 9 and a light shielding member 10 are provided.
The light passes through the band-pass mirror 12 and is reflected by the perforated mirror 11, passes through the band-pass mirror 12, passes through the objective lens 2, and once forms as a fundus illumination light beam image I on the pupil Ep of the eye E to be examined. After that, the fundus oculi Ea is almost uniformly illuminated.
At this time, a fixation target is displayed on the transmissive liquid crystal plate 8, is projected on the fundus oculi Ea of the eye E by illumination light, and is presented to the eye E as a target image. The ring slit 5 and the light shielding members 6 and 10 are used to separate the fundus illumination light and the fundus observation light in the anterior segment of the eye E to be inspected. No problem.

The reflected light from the fundus Ea returns along the same optical path,
It is taken out from the pupil Ep as a fundus observation light beam O, and the objective lens 2, the band-pass mirror 12, the perforated mirror 11
After passing through the opening at the center of the lens, the focus lens 13 and the relay lens 14 to form an image on the scale plate 15 as a fundus image Ea ′, the light reaches the optical path switching mirror 16. Here, when the optical path switching mirror 16 is retracted from the optical path, the examiner's eye e
Makes it possible to observe the fundus image Ea ′ through the eyepiece 17, while the fundus image Ea ′ formed on the scale plate 15 when the optical path switching mirror 16 is inserted in the optical path.
Is re-imaged on the CCD camera 19 by the television relay lens 18 and is projected on the liquid crystal monitor 20. This fundus image E
The apparatus is aligned with the eyepiece lens 17 or the liquid crystal monitor 20 while observing a.

The measurement light emitted from the laser diode 36 is collimated by a collimator lens 35. When the optical path switching mirror 34 is inserted in the optical path, the measurement light is reflected by the optical path switching mirror 34 and the fixed mirror 33, respectively, and is condensed. 30, the optical path switching mirrors 3
When the lens 4 is retracted from the optical path, the direct focusing lens 3
0, and passes through the dichroic mirrors 29, respectively.
Through.

On the other hand, the tracking light emitted from the tracking light source 38 is enlarged in beam diameter by a beam expander 37 at different magnifications in the vertical and horizontal directions, and after being reflected by the movable mirror 32, is shaped into a desired shape by the shaping mask 31. After that, the light is reflected by the dichroic mirror 29 and is superimposed by the condenser lens 30 with the measurement light which is formed in a spot shape at a position conjugate with the center of the opening of the mask 31. Further, the measurement light and the tracking light pass through the lens 24, are reflected once by the upper reflection surface 22b of the galvanometric mirror 22, pass through the black spot plate 27, are reflected by the concave mirror 28, and are returned again to the black spot plate 27 and the optical path length correcting half moon. The light is returned to the direction of the galvanometric mirror 22 through the plate 26.

At this time, the galvanometric mirror 22
Are arranged at conjugate positions of the pupil Ep of the subject's eye E, and have a shape indicated by a broken line M in FIG. 3 on the pupil Ep. The meniscus 26 for correcting the optical path length, the black spot plate 27 and the concave mirror 28 are arranged concentrically on the optical axis and cooperate with each other to form the upper reflecting surface 2 of the galvanometric mirror 22.
A function of a relay optical system for forming an image of 2b and the lower reflecting surface 22a at -1 time is provided. For this reason, the light beam reflected at any one of the positions P1 and P1 'on the back side of the image M of the galvanometric mirror 22 due to the insertion and retreat of the optical path switching mirror 34 into the optical path is turned off by the galvanometric mirror 22. It will be returned to the position of P2, P2 'located in the notch, and will go to the image rotator 21 without being reflected by the galvanometric mirror 22. Both luminous fluxes deflected in the direction of the objective lens 2 by the bandpass mirror 12 via the image rotator 21 are
Is applied to the fundus oculi Ea of the subject's eye E through the eye.

As described above, when the measurement light and the tracking light are reflected in the upper reflection surface 22b of the galvanometric mirror 22 and returned again, they are incident on the galvanometric mirror 22 in a state of being eccentric from the optical axis of the objective lens 2. I do. As a result, the image is formed as a spot image P2 or P2 ′ on the pupil Ep, and then the fundus oculi Ea is irradiated in a point-like manner.

The scattered and reflected light from the fundus oculi Ea is condensed again by the objective lens 2, reflected by the band-pass mirror 12, passes through the image rotator 21, and passes through the galvanometric mirror 2.
2, the measurement light and the tracking light are separated by the dichroic mirror 39 through the second focus lens 23. On the other hand, the tracking light is transmitted through the dichroic mirror 39 and is transmitted by the field lens 40 and the imaging lens 41 to the one-dimensional CCD 4.
The image is formed as a blood vessel image Ev ′ on the image 2 that is larger than the fundus image Ea ′ by the fundus observation optical system.

A part of the scattered and reflected light on the fundus oculi Ea due to the measurement light and the tracking light passes through the band-pass mirror 12 and is guided to the fundus observation optical system behind the perforated mirror 11, and the tracking light is transmitted to the scale plate. An image is formed as a bar-shaped indicator T on the reference numeral 15, and the measurement light is formed as a spot image at the center of the indicator T. As shown in FIG. 4, these images are observed together with the fundus image Ea ′ and the optotype image via the eyepiece 17 or the liquid crystal monitor 20. At this time, a spot image is superimposed and observed at the center of the indicator T, and the indicator T can be moved one-dimensionally on the fundus oculi Ea by an operating member such as an operating rod of the input unit 80.

The output signal of the one-dimensional CCD 42 is supplied to an amplifier 60.
And is input to the sample hold circuit 61.
The output signal of the sample and hold circuit 61 is a reflection distribution detecting means 48, a blood vessel diameter calculating means 49, and a peak hold circuit 6.
2, input to the inversion buffer 63 and the A / D converter 68,
The output signals of the peak hold circuit 62 and the inversion buffer 63 are input to the addition circuit 64 and subjected to addition processing. The output signal of the adding circuit 64 is sequentially input to a low-pass filter 65, a peak hold circuit 66, and a sample hold circuit 67, and further input to an A / D converter 68.

The A / D converter 68 is connected to the I / O
/ O69, memory 70, MPU 71, D / A converter 72
, And the output of the D / A converter 72 is input to a division circuit 73, where the operation of (the output signal of the low-pass filter 65) / (the output of the D / A converter 73) is performed. Done. Further, the output signal of the dividing circuit 73 is input to the differentiating circuit 74, further input to the blood vessel position calculating means 76 through the zero cross comparing circuit 75, and compared with the tracking center position signal output from the I / O 69.

From the blood vessel position calculating means 76, a signal representing the amount of deviation of the blood vessel position with respect to the tracking center position is output to the illumination light amount control means 50 and the galvanometric mirror control circuit 77, and the galvanometric mirror control circuit is controlled. The circuit 77 drives the galvanometric mirror 22 based on the shift amount. Also, the clock circuit 7
9 is input to the MPU 71 and the timing generator 78, and the output of the timing generator 78 is a one-dimensional CCD 42, peak hold circuits 62 and 66, sample and hold circuits 61 and 67, I / O 69, and a division circuit 7.
3 and controls the respective timings.

On the other hand, when the amount of shift is input from the blood vessel position calculating means 76, the illumination light amount control means 50 determines that tracking is applied when the amount of shift is smaller than the allowable value, and determines the amount of reflected light. A reflected light distribution detection start signal is output to the distribution detecting means 48. The reflection distribution detecting means 48 detects an output difference (reflection light distribution) before and after the peak of the waveform,
The result is output to the illumination light quantity control means 50, and the illumination light quantity control means 50 compares this result with a set value. If this result is equal to or greater than the set value, a signal is output to the illumination light distribution changing means 51 so as to change the light intensity distribution of the tracking rectangular indicator T illuminated on the fundus oculi Ea.

At the time of measurement, the examiner first focuses the fundus image Ea '. When the focus knob of the input unit 80 is adjusted, the transmission type liquid crystal plate 8 and
Focus lenses 13, 23, focus unit 25
Move along the optical path in conjunction. When the fundus image Ea 'is in focus, the transmissive liquid crystal plate 8, the scale plate 15, the one-dimensional CCD 42, and the confocal stop 44 are simultaneously conjugate with the fundus Ea.

In an actual examination, the examiner obtains a fundus image E
The depth of the blood vessel Ev to be measured is set while observing the focus state on a ', and the fundus image Ea' is focused. After the focusing is completed, the examiner guides the line of sight of the eye E to change the observation region, and changes the blood vessel E to be measured.
The input unit 80 is operated to move v to an appropriate position. The system control unit 47 drives a control circuit that controls the transmission type liquid crystal panel 8 to move the optotype image on the transmission type liquid crystal panel 8. Then, as shown in FIG. 4, the image rotator 21 is driven by operating the operation rod of the input unit 80 such that the indicator T is rotated and the indicator T is perpendicular to the traveling direction of the blood vessel Ev to be measured. Indicator T
To rotate.

After confirming the tracking, the examiner presses the measurement switch of the input unit 80 to start measurement. The measurement light is reflected by the dichroic mirror 39, passes through the opening of the confocal stop 44, is reflected by the mirror pairs 45a and 45b, and is received by the photomultipliers 46a and 46b, respectively. The outputs of the photomultipliers 46a and 46b are output to the system controller 47, and the received light signal is subjected to frequency analysis to obtain the blood flow velocity of the fundus oculi Ea.

FIG. 5 is a timing chart of the tracking signal waveform, and shows the waveform when the MPU 71 sets the signal level input to the A / D converter 68 to the D / A converter 73 as it is. First, when the reflectance of the peripheral portion of the blood vessel Ev to be tracked to the tracking light is the same, when the examiner starts tracking, the blood vessel image Ev ′ captured by the one-dimensional CCD 42 is generated by the timing generating means 78. It is read at the timing and amplified by the amplifier 60. The output signal of the amplifier 60 is supplied to the sample-and-hold circuit 61 by a timing generator 78.
Is sampled and held at the timing generated in step (1).

Since the blood vessel part is dark and the blood vessel peripheral part is bright, a waveform as shown in FIG. 5D is output here. Higher output levels indicate brighter parts. The output signal of the sample hold circuit 61 is input to the peak hold circuit 62, and the peak hold is performed only during the L level period shown in FIG. 5A generated by the timing generation means 78, and the input signal remains unchanged during other periods. Is output.

The output of the peak hold circuit 62 and the signal obtained by inverting the output of the sample and hold circuit 61 by the inversion buffer 63 are input to the addition circuit 64 and added to each other.
Only the blood vessel image signal having the output waveform as shown in FIG. The output of the adder circuit 64 is input to the low-pass filter 65, where high-frequency components are cut, and the waveform becomes as shown in FIG. The output of the low-pass filter 65 is input to the pick-and-hold circuit 66, the peak hold is performed only during the L-level period shown in FIG.

The sample-and-hold circuit 66 performs sampling during the L level period shown in FIG. 5C, and holds during the H level period. The output signal of the sample-and-hold circuit 66 is shown in FIG. 5 (f) together with the output waveform of the low-pass filter 65 in FIG. 5 (g). This signal is input to the A / D converter 68 and converted into digital data. , MPU 71, and outputs the result from the D / A converter 72 as the gain of the AGC for detecting the blood vessel position in the next sample period.

The output waveform of the D / A converter 72 is input to the division circuit 73 as an AGC gain for detecting a blood vessel position, and the output waveform of the low-pass filter 65 is input as a tracking signal waveform. Division circuit 73
Then, the output signal of the low-pass filter 65 is converted to the D / A converter 7.
The output signal of No. 2 is calculated, and the blood vessel signal to be tracked is subjected to AGC for blood vessel position detection by sampling in a period. FIG. 5H shows the division circuit 7 at this time.
3 shows an output waveform.

The output signal of the dividing circuit 73 is differentiated by a differentiating circuit 74, and the output of the differentiating circuit 74 is input to a zero-cross comparing circuit 75, where it is compared with about 0V. ) Is output. This blood vessel position signal is compared with the tracking center position signal output from the I / O 69 in the blood vessel position calculating means 76, and the shift amount of the blood vessel closest to the tracking center is output to the galvanometric mirror control circuit 77. The galvanometric mirror control circuit 77 drives the galvanometric mirror 22 so as to compensate for this shift amount.

On the other hand, the output of the shift amount calculated by the blood vessel position calculating means 76 is also output to the illumination light amount control means 50, and when the shift amount becomes equal to or less than the set value, the reflection distribution is detected. A detection start signal is output to the means 48.
As a result, the output of the sample hold circuit 61 is input to the reflection distribution detecting means 48. Reflection distribution detecting means 4
At 8, right and left of the extracted blood vessel image signal, for example, two inflection points from the blood vessel image signal portion are detected as singular points.

The result is output to the illumination light quantity control means 50, and the illumination light quantity control means 50 compares the output values, and determines whether the difference is equal to or less than an allowable value. Here, when it is determined that the output values are the same and equal to or smaller than the set value, the illumination light amount control unit 50 does not output a signal for changing the irradiation light amount distribution to the illumination light distribution changing unit 51, and A blood vessel diameter calculation start signal is output to the calculating means 49. Thus, the sampled and held waveform is input to the blood vessel diameter calculating means 49.

The blood vessel diameter calculating means 49 first performs a smoothing process on the sampled and held waveform to remove noise components. FIG. 6A shows the waveform at that time. Next, a blood vessel diameter detection window A is set, and a singular point xT indicated by a cross in FIG. 6B having the lowest output value is detected. Further, with the singular point xT as the center, the output values before and after the singular point xT are the highest, and 近 い,
Singular points xb1 and xb2 indicated by marks are detected. And
{(Output value of xT) + (output value of xb1)} / 2,
{(Output value of xT) + (output value of xb2)} / 2 are calculated, and x1 and x2 in the waveform corresponding to the solution are calculated, and | (address of x1) − (address of x2) |
X (conversion coefficient) is defined as the blood vessel diameter X.

Next, the case where the reflectance of the peripheral part of the blood vessel Ev to be tracked with respect to the tracking light differs between the left and right, and the case where the illumination light distribution is not changed first will be described.
A waveform in one sample period is obtained.

The blood vessel image Ev 'picked up by the one-dimensional CCD 42
Is read out at the timing generated by the timing generation means 78 and amplified by the amplifier 60. The output signal of the amplifier 60 is sampled and held by the sample and hold circuit 61 at the timing generated by the timing generation means 78. Here, when the reflected light distribution is uniform with respect to tracking, that is, when there is no difference in the brightness of the reflected light around the blood vessel, the sample-held waveform is as shown in FIG. Even after the addition processing with the inverted waveform, the waveform shown in FIG. 7B is obtained, and there is no problem in tracking.

On the other hand, when there is a difference in the brightness of the reflected light between the left and right sides of the peripheral portion of the blood vessel, a waveform that causes an output difference between the left and right sides of the blood vessel image signal is output as shown in FIG. Is done. In this case, if the illumination light quantity control means 50 determines that the tracking has started and the deviation calculated by the blood vessel diameter position calculation means 76 has become equal to or less than the allowable value, a detection start signal is output to the reflection distribution detection means 48. You. As a result, the output waveform of the sample and hold circuit 61 is changed to the reflection distribution detecting means 48.
The reflection distribution detecting means 48 detects the peak value of the singular point indicated by x in FIG. 8 in the waveform shown in FIG. Extract singular points.

The extracted information of the singular point is output to the illumination light quantity control means 50, and the illumination light quantity control means 50 compares the output values of the two singular points, and the difference is larger than a predetermined set value. In this case, a signal is output to the illumination light distribution changing means 51 so as to change the illumination light distribution in one step so that the output values of the two singular points are smaller than the set value. Then, the illumination light distribution changing unit 51 that has received the signal,
For example, the position of irradiation on the shaping mask 31 is changed by moving the movable mirror 32.

When the operation of the illumination light distribution changing means 51 is completed, the illumination light quantity control means 50 returns to the reflection distribution detecting means 48.
And a difference between the output value of the two singular points from the reflection distribution detecting means 48 and the set value is compared.
If it is still larger than the set value, the illumination light distribution changing means 51 is again
A signal is output so as to change the distribution of the illumination light, and this operation is repeated until the signal becomes lower than the set value.

Changing the illumination light distribution in this way is as follows.
This is based on the fact that the emitted laser light has a Gaussian distribution. Even after the beam expander 37 changes the aspect ratio with respect to the rectangular opening of the shaping mask 31, the distribution has a high center as shown in FIG. 9A. By moving the movable mirror 32, the intensity distribution of the illumination light on the opening can be changed as shown in FIG. 9B.

When the blood vessel diameter is calculated without changing the illumination light distribution, as shown in FIG. 6 (c), Xb2 is not correctly detected and X 'is obtained. As a result, the blood vessel diameter becomes smaller than the true value X. Will also be smaller. For this reason, the illumination light distribution changing means 51 eliminates the difference in brightness, that is, the difference in the distribution of reflected light, on the left and right sides of the blood vessel image Ev ′, thereby enabling more accurate blood vessel diameter measurement.

When the difference between the reflection distributions on the right and left sides of the blood vessel Ev is large, the illumination light distribution does not fall below the set value even when the illumination light distribution is changed, and the position of the illumination light may diverge without being determined. . Therefore, the illumination light amount control means 50 stores the number of steps at which the illumination light distribution changing means 51 changes the illumination light distribution, and outputs a warning to the examiner when the number of changeable steps is reached. Then, a measurement start signal is output to the blood vessel diameter calculating means 49 so as to calculate the blood vessel diameter.

Here, the illumination light distribution changing means 51 is configured to change the illumination light distribution one step at a time by the illumination light quantity control means 50. However, the illumination light distribution table is stored in the illumination light quantity control means 50 in advance. In advance, the required number of steps is calculated from the output difference between the two specific points from the reflection distribution detecting means 48 and the set value, and the illumination light distribution changing means 51 is controlled to move by that amount. The configuration may be such that

It can be seen that making the reflected light distribution uniform by changing the illumination light distribution also contributes to the stabilization of tracking. That is, similarly to the above, the output of the peak hold circuit 62 and the output of the signal of the sample hold circuit 61 inverted by the inversion buffer 63 are input to the addition circuit 64, added by the addition circuit 64, and shown in FIG. Only the blood vessel image signal having the waveform shown is extracted. This waveform is different from the waveform shown in FIG. 7B in the case where there is no difference in brightness, and it is not possible to extract only the blood vessel image Ev ′ signal, and a portion corresponding to the difference in brightness between left and right remains. .

When the same signal processing as described above is performed on the output of the addition circuit 64, the output waveform of the low-pass filter 65 and the output waveform of the division circuit 73 are shown in FIGS. 7 (e) and 7 (f), respectively. As a result, the blood vessel position signal finally used for tracking has a shape as shown in FIG. 7 (g), and one false signal is generated in addition to the signal indicating the original blood vessel position. In this case, if the fixation tremor occurs earlier than the interval at which the blood vessel image Ev 'is captured and a false signal comes near the location where the blood vessel position signal is located, the false signal is tracked, and tracking is performed from the desired blood vessel. It may come off.

However, by performing the control for moving the movable mirror 32 as described above, the waveform shown in FIG. 7C, in which the left side is dark and the right side is bright, is shown in FIG.
The output of the peak hold circuit 62 and the output obtained by inverting the output of the sample hold circuit 61 by the inverting buffer 63 are similarly input to an adder circuit 64 using these signals, and added. When only the blood vessel image signal is extracted, the output waveform of the adder circuit 64 becomes as shown in FIG. 7 (i), and a portion corresponding to the difference between the left and right brightness as shown in FIG. 7 (d) remains. Instead, only the blood vessel image Ev ′ can be extracted and input to the low-pass filter 65 for processing. Thus, by providing the irradiation light amount control means 50 and changing the light amount distribution on the shaping mask 31, stable tracking can be performed.

In this embodiment, the illumination light distribution changing means 5 is used.
As an example of the control by 1, the movable mirror 32 for bending the laser light in the direction of the shaping mask 31 is moved, but as shown in FIG.
Is configured such that the focal position of the concave lens and the focal position of the convex lens are overlapped by combining two concave and convex cylindrical lenses, and the aspect ratio of the beam is changed. By moving the beam expander 37, the illumination light distribution of the laser light emitted from the tracking light source 38 to the shaping mask 31 can be changed.

The illumination light distribution is changed by inserting a parallel flat plate having a thickness between the beam expander 37 and the shaping mask 31 and changing the angle of the parallel flat plate by the illumination light amount control means 50. The configuration may be such that the tracking light source 38 itself is moved. Further, since the two singular points detected by the reflection distribution detecting means 48 of the present embodiment are the boundary points with the blood vessel Ev, the value calculated by the illumination light amount means 50 from the output value of this boundary point is the difference between the two values. Instead, the ratio may be calculated and compared with the set value.

[0059]

As described above, in the ophthalmic examination apparatus according to the present invention, when the automatic tracking is started, the blood vessel is illuminated from the output signal of the imaging means for illuminating the area including the blood vessel to be inspected and imaging the reflected light. The output value at the boundary point between the two is detected by the reflection distribution detecting means, and when the value calculated from the detection result is greater than the set value, the illumination light distribution changing means is illuminated so as to be equal to or less than the set value. Control to change the light quantity distribution on the fundus of the eye, and the blood vessel diameter calculation unit starts the blood vessel diameter calculation when the value becomes equal to or less than the set value, so that the reflected light distribution around the desired blood vessel is different. Even in the case, the value of the blood vessel diameter calculation can be made highly accurate,
Stable automatic tracking becomes possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an ophthalmologic examination apparatus according to an embodiment.

FIG. 2 is a configuration diagram of a system control unit.

FIG. 3 is an explanatory diagram of a light beam arrangement on a pupil.

FIG. 4 is an explanatory diagram of an observation fundus image.

FIG. 5 is a timing chart of a tracking signal waveform.

FIG. 6 is a graph showing waveform processing of a blood vessel image signal.

FIG. 7 is a graph of singular point extraction.

FIG. 8 is a graph showing a light amount distribution on a shaping mask.

FIG. 9 is a graph for calculating a blood vessel diameter.

FIG. 10 is a perspective view of a second illumination light distribution changing method.

[Explanation of symbols]

 Reference Signs List 1 observation light source 8 transmissive liquid crystal plate 12 band pass mirror 19 CCD camera 20 liquid crystal monitor 21 image rotator 22 galvanometric mirror 25 focus unit 32 movable mirror 36 laser diode 38 tracking light source 42 one-dimensional CCD 46a, 46b photomultiplier 47 System control unit 48 Reflection distribution detection unit 49 Blood vessel diameter calculation unit 50 Illumination light amount control unit 51 Illumination light distribution change unit 61, 67 Sample hold circuit 62, 66 Peak hold circuit 63 Inversion buffer 64 Addition circuit 65 Low-pass filter 71 MPU 73 Divide Circuit 74 Differentiating circuit 75 Zero-cross comparing circuit 76 Blood vessel position calculating means 78 Timing generating means 79 Clock circuit 80 Input unit 81 Blood vessel part extracting unit 82 AGC unit 83 Processing Condition determination unit 84 Automatic tracking control unit

Claims (4)

[Claims] An illumination unit for illuminating a region including a specific blood vessel as a target, an imaging unit for imaging a blood vessel and outputting a video signal, and automatically tracking a blood vessel based on a processing result of an output signal of the imaging unit. And a blood vessel diameter calculating means for calculating the diameter of the blood vessel, the distribution of reflected light in a region including the blood vessel is detected from the output signal of the imaging means, and a boundary point with the blood vessel is detected. Reflection distribution detection means for detecting the output value of the illumination light distribution change means for changing the light amount distribution position on the fundus of the illumination light provided in the illumination means, and a control unit for controlling the illumination light distribution When the automatic tracking is started by the automatic tracking unit, the control unit controls the illumination light distribution changing unit so that a value calculated from a result of the reflection distribution detecting unit is smaller than a set value, Configuration An ophthalmologic examination apparatus, wherein control is performed so that calculation of a blood vessel diameter by the blood vessel diameter calculation means is started when the value becomes smaller than the value. 2. The ophthalmologic examination apparatus according to claim 1, wherein the control unit repeatedly controls the illumination light distribution changing unit until the result of the reflection distribution detecting unit becomes smaller than a set value. 3. The control section stores in advance a light quantity distribution of the illumination light, compares a result of the reflection distribution detecting means with the set value, and calculates a necessary light quantity distribution position from the light quantity distribution stored in advance. The ophthalmologic examination apparatus according to claim 1, wherein the control unit controls the illumination light distribution changing unit by calculating a change amount of the illumination light distribution. 4. The ophthalmologic examination apparatus according to claim 1, wherein the value calculated by the control unit is a value obtained by quantifying an output value at two boundaries with a blood vessel detected by the reflection distribution detecting unit.