JPH0731596A - Eyeground blood flow meter - Google Patents

Abstract

PURPOSE:To provide the quantity of a blood flow in real time by obtaining the correct blood flow speed and the blood vessel diameter from the measured blood vessel position with respect to the irradiating position of a laser beam and the detecting position. CONSTITUTION:A luminous flux from a measuring light source 39 for emitting He-Ne laser beam is projected on the eyeground Ea of a testee eye E, some of reflected light from the eyeground Ea is reflected by a pair of small mirrors 32a in the back of an apertured mirror 30 to be received by a multiplier 41a, and the blood flow speed is calculated by a blood flow speed calculating part 81. The remainder of reflected light fro the eyeground is detected by a CCD sensor 71 of a blood vessel detecting system 67 through an image stabilizer 34 and an observation optical system 35, and the blood vessel diameter is calculated by a blood vessel diameter calculating part 85. The blood flow speed and the blood diameter are obtained in synchronization with each other by a synchronous signal generating circuit 87, and the quantity of a blood flow of a measured blood vessel Ev is calculated from the above signals in a blood flow quantity calculating part 82.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fundus blood flow meter for measuring blood flow velocity in a fundus blood vessel.

[0002]

2. Description of the Related Art FIG. 13 shows a conventional example of a fundus blood flow meter in which a slit lamp normally used for ophthalmic diagnosis is modified for blood flow measurement. The white illumination light emitted from the observation light source 1 and reflected by the perforated mirror 2 passes through the slit 3 and the lens 4, passes through the contact lens 5 that corrects the refractive power of the cornea of the eye E, and then passes through the contact lens 5 of the eye E. Measurement vessels on fundus Ea
Illuminate Ev. The reflected light from the fundus Ea is reflected by the lenses 6a, 6
The stereoscopic observation system including the b, the mirrors 7a and 7b, the mirrors 8a and 8b, and the eyepieces 9a and 9b enables the examiner to observe the fundus Ea of the eye E including the measurement blood vessel Ev.

On the other hand, the measurement light from the He-Ne laser light source 10 passes through the central hole of the perforated mirror 2 and is made coaxial with the illumination light, and then passes through the slit 3 and the lens 4 to the fundus Ea.
Irradiate the measurement blood vessel Ev in a spot shape. The reflected light from the measurement blood vessel Ev includes the scattered light by the blood cells flowing in the blood vessel Ev and the scattered light by the blood vessel wall, and the lenses 6a, 6b, the mirror 7a, which are arranged in two directions forming the angle α ', 7b, mirror 8
The light is received by the photomultipliers 12a and 12b through a and 8b and the fibers 11a and 11b.

The examiner observes the fundus Ea of the eye E to be examined,
The measurement is started after the operation of aligning the laser light with the measurement blood vessel Ev. The received light signals at the photomultipliers 12a and 12b include a predetermined beat signal because the Doppler-shifted component due to the blood cells flowing in the blood vessel Ev interferes with the component reflected by the stationary blood vessel wall. There is. By analyzing the frequency of this beat signal,
The blood flow velocity in Ev is calculated.

FIG. 14 shows an example of the result of frequency analysis of the measured received light signal. The horizontal axis shows frequency and the vertical axis shows power. From each received light signal, Δfmax
Is calculated, and the maximum blood flow velocity in the blood vessel Ev is calculated from this. Δfmax = (κs −κi) ・ υ

Where κs is a wave number vector in the light receiving direction,
κi is the wave number vector in the incident direction, and υ is the velocity vector of blood flow. Each result from each received signal is Δfmax
1 and Δfmax2, Vmax = (λ / n · α) · | Δfmax1−Δfmax2 | / c
It becomes osβ.

Where λ is the wavelength of the laser beam, n is the refractive index of the measurement site, α is the angle between the two light receiving directions in the eye, and β is the angle between the plane formed by the two light receiving directions and the blood flow. is there. As described above, by measuring from two directions, the contributions related to the incident direction are canceled out, and the blood flow of the blood vessel Ev at an arbitrary site on the fundus Ea can be measured.

FIG. 15 shows an example of an image observed by an examiner. The blood vessel Ev to be measured is fitted to the scale SC prepared on the focal planes of the eyepieces 9a and 9b. PS is a spot image of the He-Ne laser light for measurement, and the true blood flow is obtained from the relationship between the intersection line A between the plane formed by the two light receiving directions and the fundus Ea and the angle β formed by the blood flow velocity vector υ. In order to measure the velocity, it is necessary to match the intersection line A with the velocity vector υ.

For that purpose, conventionally, the entire light receiving optical system is rotated, or the observation fundus image is rotated by an image rotator arranged in the light receiving optical system (Feke: IEEE.
Transactions of Biomedical Engineering, Vol BME-3
4, No. 9, Sept. 1987, pp 673 to 680) or a rotary aperture mechanism (Riva: Applied Opties, Vol. 20, No. 1, 1, Ja
n.1981, pp117-120) have been proposed. In addition, an example of configuring a fundus blood flow meter by adding functions to a general fundus camera is "Milbocker: ARVO, Annual Meeting paper presentat
ion No. 2786,4 May 1990 ", which is registered as US Pat. No. 5,106,184.

[0010]

[Problems to be Solved by the Invention]

(1) However, in the above-mentioned conventional example, only the blood flow velocity is measured, but in order to diagnose a peripheral blood flow state such as a fundus blood vessel, the blood vessel diameter is also measured, and the blood flow velocity and the blood vessel diameter are measured. Therefore, it is necessary to determine the flow rate of blood flowing in the blood vessel. However, when performing this type of measurement, the blood flow, blood vessel diameter, and blood vessel position change with time due to pulsation of blood vessels, and therefore the accuracy thereof is significantly reduced when calculating the arterial blood flow.

(2) Further, in the above-mentioned conventional example, in order to match the blood vessel direction and the measurement direction, a mechanism such as an image rotator or a rotary aperture is required, and these devices are large in size and expensive. In the actual measurement, if there is a slight deviation between the blood vessel direction and the measurement direction, a measurement error will occur, and therefore skill will be required for measurement using this type of device.
Further, the relationship between the blood vessel direction and the measurement direction is different in the alignment of the eye to be examined with respect to the diameter of the blood vessel, the eye movement of the eye to be examined, the undulation of the fundus, and the orientation of the blood vessel in the measurement part at the fundus, etc., and accurate measurement is very accurate. difficult.

The first object of the present invention is to solve the above-mentioned problem (1).
The blood flow rate that constantly changes from the blood flow velocity and the blood vessel diameter is solved, the relationship between the blood vessel position and the irradiation and detection positions is held constant, and accurate blood flow measurement can be performed. To provide the total.

A second object of the present invention is the above-mentioned problem.
The object of the present invention is to solve the problem (2) and provide a fundus blood flow meter capable of measuring a blood flow value with high accuracy by matching the blood flow direction with the optical axis of the scattered light detection optical system by a simple operation.

[0014]

A fundus blood flow meter according to a first aspect of the present invention for achieving the above-mentioned object is an irradiation means for guiding coherent measurement light to a measurement site on the fundus and scattering from the measurement site. Condensing means for condensing the reflected light, detecting means for detecting the light flux condensed by the condensing means, and blood flow velocity calculating means for calculating the blood velocity flowing in the blood vessel of the fundus from the output of the detecting means. An illumination unit that guides illumination light to a measurement site or its vicinity, an imaging unit that projects an image of the illumination site onto an imaging surface, a blood vessel diameter calculation unit that calculates a blood vessel diameter from the output of the imaging unit, and a predetermined time. A synchronization signal generating means for generating a synchronization signal a plurality of times, and a control means for operating the blood flow velocity calculating means and the blood vessel diameter calculating means based on the output of the synchronization signal generating means. Characterize.

Further, the fundus blood flow meter according to the second invention measures the blood flow state of the fundus tissue by irradiating the fundus with a single light beam and analyzing the light flux obtained from the fundus tissue. In a flowmeter, an irradiation unit that irradiates a measurement site with a light flux from a light source that generates coherent light, and a detection unit that independently detects the light flux obtained from the measurement site in at least three directions whose direction vectors are not on the same plane. A first signal processing means for obtaining a Doppler shift component corresponding to the blood flow velocity from the output signal of the detection means, and a Doppler shift component of the light flux in at least three directions obtained from the measurement site and the Doppler shift component obtained from the measurement site. A second signal processing means for obtaining the blood flow velocity vector in the blood vessel or its absolute amount from the information on the detection direction of the light flux is provided.

[0016]

In the fundus blood flow meter of the first invention having the above-mentioned configuration, the blood flow velocity measuring means and the blood vessel diameter calculating means are controlled by the synchronizing signal generating circuit, so that the blood flow velocity and the blood vessel diameter can be measured in real time. taking measurement.

Further, in the fundus blood flow meter of the second invention, scattered reflected light from the measurement blood vessel is detected from three or more independent directions, the Doppler shift amount of each direction component of this scattered light is obtained, and this Doppler shift is obtained. The true value of the blood flow velocity vector of the fundus blood vessel is calculated from the amount and the information of the detection direction of the scattered reflected light with respect to the direction of the irradiation light.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is a block diagram of the first embodiment, which utilizes a model of a fundus camera. A visible light cut filter 23, a condenser lens 24, a mirror 25, a field lens 26, and a ring having a ring-shaped opening are provided on an optical path from an illumination light source 21 including a tungsten lamp that emits near-infrared light to an objective lens 22. A slit 27, relay lenses 28 and 29, a perforated mirror 30 having an opening in the center, and an image rotator 31 are arranged.

Further, on the optical path behind the perforated mirror 30, a pair of small mirrors 32a and 32b, an aperture 33, an image stabilizer 34, an observation optical system 35, a lens 36,
An aperture 37, a lens 38, and a measurement light source 39 that emits He—Ne laser light are arranged. Lenses 40a, 40b, photomultipliers 41a, 4 are provided on the optical paths in the respective reflecting directions of the small mirror pairs 32a, 32b.
1b is arranged. In FIG. 1, only members on the optical axis of the small mirror 32a are shown to avoid duplication.

The image stabilizer 34 includes a lens 5
1, 52, galvanometric mirror 53, lens 5
4, 55 and galvanometric mirrors 56 are sequentially arranged, and the galvanometric mirrors 53 and 56 are rotated by operating an operating rod 57 attached to the outside. In this image stabilizer 34, the fundus Ea is the lens 5
The galvanometric mirror 53 is composed of 1 and 52, and the galvanometric mirror 56 is composed of lenses 54 and 55.
It is said to be conjugated. The rotation axis of the galvanometric mirror 53 is set perpendicular to the paper surface, and the rotation axis of the galvanometric mirror 56 is set orthogonal to this rotation axis.

The observation optical system 35 includes a focusing lens 61 and a dichroic mirror 62 which can move on the optical path.
Is provided, in the reflection direction of the dichroic mirror 62,
The television camera 6 through the half mirror 63 and the lens 64.
5 is arranged, and the output of the television camera 65 is connected to the monochrome television monitor 66. Also, half mirror 6
A blood vessel detection system 67 is provided in the reflection direction of 3, and the mirror 6
A one-dimensional CCD sensor 71 with an image intensifier is arranged via 8, a lens 69, and a filter 70.

The outputs of the photomultipliers 41a and 41b are connected to the input side of the blood flow velocity calculation unit 81, and the output of the blood flow velocity calculation unit 81 is connected to the blood flow rate calculation unit 82 and the display unit 83. The output of the blood flow rate calculation unit 82 is connected to the display unit 83. The output of the CCD sensor 71 is connected to the controller 84 and the blood vessel diameter calculation unit 85, and the output of the controller 84 is the galvanometric mirror 53.
Connected to a drive circuit 86 for driving the
Is connected to the blood flow rate calculation unit 82 and the display unit 83. Further, the output signal SS of the synchronization signal generation circuit 87 is CC
D sensor 71, blood flow velocity calculation unit 81, blood vessel diameter calculation unit 85
It is connected to the.

In the fundus blood flow meter having the above structure,
Illumination light, which is near-infrared light emitted from the illumination light source 21, is imaged on the ring slit 27 via the visible light cut filter 23, the condenser lens 24, the mirror 25, and the field lens 24. The illumination light emitted from the ring slit 27 is transmitted through the relay lenses 28 and 29 to the perforated mirror 30.
After being imaged once, the image is formed on the pupil of the eye E to be inspected by the objective lens 24 through the image rotator 31, and the fundus Ea of the eye E is substantially uniformly illuminated. The field lens 26 has a function of efficiently guiding the light flux into the eye E to be inspected.

The reflected light from the fundus Ea is returned to the objective lens 2 again.
4. Go through the image rotator 31 and the perforated mirror 30
The light enters the image stabilizer 34 through the central hole and the aperture 33. In this case, the galvanometric mirrors 53 and 56 can be rotationally moved by operating the operating rod 57 to specify the measurement site on the fundus Ea.

The light flux emitted from the image stabilizer 34 enters the observation optical system 35, and the focusing lens 6
1. After passing through the dichroic mirror 62, the half mirror 6
3 is distributed through the lens 64, one of which is imaged on the television camera 65 having a sensitivity to near infrared light through the lens 64, and the fundus image Ea ′ is displayed on the monochrome television monitor 66. The examiner observes the fundus oculi image Ea ′ displayed on the television monitor 66 by the illumination light, and performs alignment of the device and selection of a measurement site.

The other light beam split by the half mirror 63 enters the blood vessel detection system 67, and is reflected by the mirror 68, the lens 69,
An image is formed on the one-dimensional CCD sensor 71 through the filter 70. Since the filter 70 blocks the wavelength of the laser light of the measurement light source 39, the laser light does not reach the CCD sensor 71, and the CCD sensor 71 captures a blood vessel image by only the illumination light from the illumination light source 21.

The CCD sensor 71 of the blood vessel detection system 67 forms a larger image than the image of the television camera 65, and displays a detailed blood vessel image on the display section 83 via the blood vessel diameter calculation section 85. The output of the CCD sensor 71 is also sent to the controller 84, which analyzes the blood vessel image and
By calculating the one-dimensional movement amount of the blood vessel Ev on the sensor 71, a drive signal to the drive circuit 86 is generated.

FIG. 2 is a block circuit configuration diagram of the controller 84 for producing a drive signal to the drive circuit 86 for operating the galvanometric mirror 53, and FIG. 3 is a timing chart diagram during one scan (about 1 ms). The example of the waveform of is shown. The output of the CCD sensor 71 is connected to a differentiator 93 via an amplifier 91 and a low pass filter 92. The output of the differentiator 93 is connected to the counter 95 via the Xerox comparator 94. The output of the counter 95 is connected to the output unit 97 via the D / A converter 92. Furthermore, the output of the operating rod 57 is input to the output unit 97. The CCD sensor 71, counter 95, D
The / A converter 92 includes a sync signal SS of the sync signal generation circuit 87.
Has been entered.

One-dimensional CCD consisting of 256 pixels
After being amplified by the amplifier 91, the image output W1 of 71 is shaped like a waveform W2 by an appropriate low-pass filter 92 that does not deform the actual fundus image waveform, and differentiated by a differentiator 93 to become a differentiated waveform W3. After that, it passes through the zero-cross comparator 94 and is binarized to form a waveform W4. Waveform
Like W5, the count value for counting while the waveform W4 is low level is cleared for each measurement in synchronization with the signal from the synchronization signal generation circuit 87, and the count value at the end of one scan corresponds to the position of the blood vessel. ing. A signal for driving the galvanometric mirrors 53 and 56 is output from the position signal and the operating rod 57 to the drive circuit 86. In the embodiment, by performing this operation at a rate of 1 KHz, automatic control is performed so as to maintain a constant relationship between the position of the blood vessel to be measured that moves due to eye movement and the irradiation position of the laser light and the position of the detection unit. To do.

The galvanometric mirror 53 has a function of automatically compensating for the involuntary eye movement of the eye E by operating the drive circuit 86. That is, once the examiner designates the blood vessel position to be measured, the galvanometric mirror 5 is arranged so that the blood vessel position imaged on the CCD sensor 71 is always constant.
3 is driven. At this time, the measurement laser light is guided by the half mirror 63 back to the fundus Ea in the reverse optical path and always projected on the designated measurement blood vessel.

The measuring laser beam is coupled to the lens 3 before being coupled to the observation optical system 35 by the dichroic mirror 62.
8 forms a spot on the aperture 37 at a position conjugate with the fundus Ea, and the conjugate relationship is adjusted via the lens 36. Therefore, when the examiner moves the focusing lens 61 on the optical axis to focus the fundus Ea, the image pickup surface of the television camera 65 and the image pickup surface of the one-dimensional CCD sensor 71 are simultaneously conjugated with the fundus Ea. Of the measurement laser light reflected from the blood vessel Ev on the fundus Ea, the light flux that travels straight through the perforated mirror 30 is directly guided to the observation optical system 35 and acts as an index indicating the measurement site by the television camera 65.

A part of the light is reflected by a pair of small mirrors 32a and 32b provided behind the perforated mirror 30. FIG. 4 shows the arrangement of the small mirror pairs 32a and 32b, the illumination light flux, and the observation light flux on the pupil. Small mirror pair 32
Images Ma and Mb by a and 32b respectively show the light receiving light beam position, the image PA of the aperture 33 shows the positions of the observation light beam and the measuring laser beam, and the image PS of the light transmitting portion of the ring slit 27 shows the illumination light beam. The position is shown. The angle at which the measurement site is viewed from the images Ma and Mb corresponds to the measurement angle α in FIG.
Therefore, by processing the signals received by the photomultipliers 41a and 41b in the same manner as in the conventional example, the blood flow velocity in the blood vessel to be measured can be obtained.

FIG. 5 shows the state of the fundus image Ea 'observed on the television monitor 56, and the direction of the A axis of the coordinates is the small mirror pair 3
The direction of the line of intersection between the plane connecting the centers of 2a and 32b and the fundus oculi Ea is shown. S is an image of the measuring laser beam and is a spot image showing the measurement site. The examiner first operates the operating rod 57 to match the spot image S on the blood vessel Ev to be measured. At this time, the spot image S is fixed while being positioned at the center with respect to the field of view of the examiner, and the fundus image Ea ′ is moved and observed.

After that, the image rotator 31 is rotated to match the blood flow direction of the blood vessel Ev to be measured with the direction of the A axis. This means that cosβ = 0 in FIG. That is, when the image rotator 31 is rotated, the fundus image Ea ′ rotates the center of the visual field in the direction of the arrow in the figure. As described above, when the measurement site is selected, the CCD sensor 71 of the blood vessel detection system 67 captures a one-dimensional image in the D axis direction orthogonal to the A axis. That is,
During the measurement, the galvanometric mirror 53 of the image stabilizer 34 is driven so that the position of the blood vessel Ev in the D axis direction becomes constant.

As described in the conventional example, according to the principle of velocity detection, the blood flow velocity is obtained from the interference signal between the scattered reflected light from the blood vessel wall and the scattered reflected light in the blood flow, and therefore, during measurement. Even if the eyeball moves in the A-axis direction, the blood vessel Ev is almost parallel to the A-direction, so the measurement result is not affected. However, when it moves in the D-axis direction, the measurement laser beam deviates from above the blood vessel Ev and measurement becomes impossible. Therefore, the blood vessel detection system 67 and the image stabilizer 34 jointly perform the one-dimensional tracking in the D-axis direction.

The light beams reflected by the small mirror pairs 32a, 32b are condensed by the lenses 67a, 67b and received by the photomultipliers 41a, 41b. The outputs of the photomultipliers 41a and 41b are input to the blood flow velocity calculation unit 81, and the blood flow velocity is calculated. Note that this calculation is performed in synchronization with the synchronization signal SS from the synchronization signal generation circuit 87 input to the blood flow velocity calculation unit 81.

FIG. 6 is a block diagram of the blood flow velocity calculation unit 81. The blood flow velocity calculation unit 81 is composed of two spectrum analyzers 101a and 101b and a signal processing unit 102 which receives these signals. The outputs of the photomultipliers 41a and 41b are connected to the spectrum analyzers 101a and 101b, respectively, and the output of the signal processing unit 102 is connected to the blood flow volume calculation unit 82 and the display unit 83.

The light received by the photomultipliers 41a and 41b is photoelectrically converted into an electric signal and sent to the spectrum analyzers 101a and 101b. The signals Fourier-transformed by these signals are as shown in FIG. 14, and two maximum blood flow rates Δfmax1 and Δfmax2 are calculated by the signal processing unit 102 to calculate the blood flow velocity. The calculated blood flow velocity is sent to the blood flow rate calculation unit 82 and the display unit 83.

FIG. 7 is a block diagram of the blood vessel diameter calculating unit 85, and FIG. 8 is a timing chart thereof, showing the blood vessel diameter calculating unit 8
The output SG of the CCD sensor 71 is output to the comparator 111 of 5
Is connected to the reference voltage output Ve of the reference voltage generating circuit 112, the output Wa of the comparator 111 is connected to the integrator 113, and the integrator 113 outputs the blood vessel diameter signal. Further, the integrator 113 has an initialization signal circuit 114.
Output IS is connected to the sync signal of the sync signal generation circuit 87.
The SS is connected to the CCD sensor 71 and the initialization signal circuit 114.

The signal SG is input from the CCD sensor 71 to the comparator 111 in synchronization with the synchronization signal SS from the synchronization signal generation circuit 87. The comparator 111 receives the reference voltage Ve from the predetermined reference voltage generation circuit 112 and the signal SG.
And the output is input to the integrator 113. The integrator 113 integrates the output Wa of the comparator 111 to obtain the potential V. This potential V is cleared for each measurement by the signal IS from the initialization signal circuit 114. The output potential V of the integrator 113 immediately before being cleared corresponds to the blood vessel diameter.

The blood vessel diameter thus obtained is also sent to the blood flow rate calculation unit 82 and the display unit 83, like the blood flow velocity. The blood flow rate calculation unit 82 calculates the blood flow rate from the blood flow velocity and the blood vessel diameter supplied from the blood flow velocity calculation unit 81 and the blood vessel diameter calculation unit 85, respectively. Blood velocity, blood vessel diameter, blood flow,
For example, it is displayed on a display unit 83 such as a display or plotter, and it is possible to observe the blood vessel diameter, blood flow velocity, and blood flow volume in real time. Then, based on these information, it can be used for diagnosis of arteriosclerosis, diabetes, etc., for example.

In the first embodiment, the operation of the circuit is advanced by using the synchronizing signal SS from the synchronizing signal generating circuit 87. However, this is replaced with a clock circuit and the operation is advanced by the clock signal. May be. The clock signal from the clock circuit is supplied to the blood vessel diameter calculation unit 85 and the blood flow velocity calculation unit 81, and the respective internal counters count the clock signals to determine the timing of each calculation. At this time, the calculated blood vessel diameter and blood flow velocity are
It suffices to set the internal counter so that the values are almost the same.

FIG. 9 shows a second embodiment, which uses the model of the fundus camera as in the first embodiment. From the white illumination light source 121 such as a tongue lamp to the objective lens 12
A bandpass filter 123, a condenser lens 124, a mirror 125, a field lens 126, a ring slit 127, a relay lens 128, and a perforated mirror 129 that pass only light in the yellow-green region are arranged on the optical path reaching 2. . Behind the perforated mirror 129, three sets of small mirrors 131a, 131b, 131c and an aperture 1 are provided.
32, positioner 133, observation optical system 134, lens 1
35, an aperture 136, a lens 137, and a measurement light source 138 that emits a He—Ne laser beam are arranged.

The positioner 133 has lenses 141, 1
42, galvanometric mirror 143, lens 14
4, 145 and a galvanometric mirror 146 are sequentially arranged, and the galvanometric mirrors 143, 1
46 is operated by the operation rod 147. Further, the rotation axis of the galvanometric mirror 143 is set to be perpendicular to the paper surface, and the rotation axis of the galvanometric mirror 146 is set to be orthogonal to this rotation axis. In the positioner 133, the fundus Ea is the lens 14
Galvanometric mirror 143 with 1, 142,
Further, the lenses 144 and 145 make it conjugate with the galvanometric mirror 146.

In the observation optical system 134, a focusing lens 151 that moves on the optical path, a half mirror 152, and a lens 153 are arranged in the reflection direction of the half mirror 152, and a color television camera 15 is formed at the image forming position of the lens 153.
4 are arranged.

Three sets of small mirrors 131a, 131b, 13
In the reflection direction of 1c, three sets of lenses 161a,
161b, 161c, three sets of photomultipliers 162a, 162b, 162c, which are photodetectors, and three sets of signal processing units 163a, 163b, 163c are arranged.
The outputs of these signal processing units 163a, 163b, 163c and the output of the television camera 154 are connected to the television monitor 165 via the processor 164.

In the fundus blood flow meter having such a configuration, the illumination light emitted from the illumination light source 121 has the bandpass filter 123, the condenser lens 124 and the mirror 1.
25, a light source image is formed on the ring slit 127 via the field lens 126. Field lens 1
Reference numeral 26 is for efficiently guiding the subsequent light flux into the eye to be inspected. The image of the ring slit 127 is once formed on the perforated mirror 129 by the relay lens 128 and then formed on the pupil of the eye E to be inspected by the objective lens 122 to illuminate the fundus Ea substantially uniformly. The reflected light from the fundus Ea passes through the objective lens 122 again, passes through the central hole of the perforated mirror 129 and the aperture 132, and enters the positioner 133.

In the positioner 133, when the examiner moves the operating rod 147 in order to specify the place to perform the measurement, the measurement site on the fundus Ea moves in accordance with the movement. That is, in the positioner 133, the lenses 141, 14
Galvanometric mirror 1 by 2, 144, 145
43 and 146 are configured to have a conjugate relationship with the fundus oculi Ea, and by moving the operating rod 147, the respective galvanometric mirrors 143 and 146 are rotated to change the rotation angle, and the measurement site on the fundus oculi Ea is changed. It can be moved vertically and horizontally.

The light flux emitted through the positioner 133 enters the observation optical system 134, and the focusing lens 151 and the lens 153 work together in the observation optical system 134 to form a fundus image on the photographing surface of the color television camera 154. To do.
The output of the television camera 154 displays the fundus image Ea ′ on the television monitor 165 via the processor 164.

On the other hand, the red He-Ne laser light emitted from the measurement light source 138 is transmitted through the lens systems 137, 135, and 135.
The aperture 136 is set to have an appropriate diameter, and the half mirror 152 couples it to the observation system 134. In addition, the lens 137 allows the aperture 13 located at a position conjugate with the fundus Ea.
6, a spot is formed, and the conjugate relation is adjusted through the lens 135. Therefore, the examiner can focus lens 1
When 51 is moved on the optical axis to focus the fundus Ea, the imaging surface of the television camera 154 and the measurement light spot are conjugated, so that the fundus Ea is immediately focused.

The laser beam for measurement coupled to the observation system passes through the positioner 133, then passes through the perforated mirror 129, and through the objective lens 122, in a region including a measurement site for measuring blood vessels on the fundus Ea. It is irradiated to a measuring part.

The examiner aligns the device by looking at the yellow-green fundus image Ea 'output on the television monitor 165, while looking at the displayed fundus image Ea' and the red measurement site by the measuring laser beam. , The operating rod 147 is operated to select the measurement site. That is, by operating the operating rod 147, the galvanometric mirrors 143 and 146 are driven, and the measurement site is moved back and forth and left and right on the fundus Ea, so that the measurement site can be designated.

The measurement light reflected by the blood vessel Ev of the fundus Ea passes through the objective lens 122 and the perforated mirror 129 in the same manner as the illumination light, and a part of the measurement light includes three sets of small mirrors 131a and 131a.
After being reflected by b and 131c, they are received by photomultipliers 162a, 162b and 162c via relay lenses 161a, 161b and 161c, respectively. Further, the light not reflected by the small mirrors 131a, 131b, 131c is guided to the observation optical system 134 via the positioner 133, is imaged on the television camera 154, and acts as a red index indicating the measurement site described above.

Three sets of photomultipliers 162a, 1
The electric signals indicating the intensity changes of the scattered light in the three directions detected by 62b and 162c are converted into signals indicating the Doppler shift amount by the signal processing units 163a, 163b, and 163c using FFT, respectively. A processor 164 that performs signal processing including conversion logic on these three sets of signals
And the blood flow velocity vector is calculated. The calculated blood flow velocity vector is displayed on the television monitor 165 in superimposition with the fundus oculi image Ea ′, or is displayed as a chart showing the time change of the absolute blood flow velocity.

FIG. 10 shows the state of the measurement light on the eye E to be inspected. The laser light for measurement passes through the pupil of the eye E to pass the pupil passing point I1 and is applied to the measurement site A on the fundus Ea. By this irradiation of the measurement laser light, scattered reflected light is generated at the measurement site A designated by the examiner. This scattered reflected light contains light of a wavelength where the velocity vector υ of the blood flow flowing in the blood vessel Ev at the measurement site A is Doppler-shifted by blood, and at the same time, from the blood vessel wall at the measurement site A and the surrounding tissues. It also contains scattered light of the same wavelength as the irradiation light.

The scattered light for detection emitted in the directions K1, K2 and K3 passes through the pupil passing points I2, I3 and I4 on the pupil of the eye E to be guided to the small mirrors 131a, 131b and 131c, respectively. Therefore, the angles formed by the direction vectors κ i, κ 1, κ 2, and κ 3 are fixed by the positional relationship between the small mirrors 131 a, 131 b, and 131 c. However, the direction vector κi,
The direction relation between κ1, κ2, κ3 and velocity vector υ is
It is not constant at all due to the alignment of the eye E with respect to the blood vessel Ev, the eye movement of the eye E, the ups and downs of the fundus Ea, the orientation of the blood vessel Ev at the specified position on the fundus Ea, and the like. In addition, the angle formed between the direction vectors is increased so that the square formed by the pupil passing points I1, I2, I3, and I4 is inscribed in the entire pupil as much as possible so that the measurement accuracy in the process of combining the vectors is improved. ing.

FIG. 11 is an explanatory view of the blood flow velocity vector calculation method, in which the blood flow measurement site A of the blood vessel Ev on the fundus Ea is measured.
Then, the scattered light is generated by the irradiation of the measuring light of the direction vector κ i. This scattered light becomes light whose wavelength is Doppler-shifted by the blood flow of the velocity vector υ at the measurement site A. The scattered light is observed in the directions of direction vectors κ1, κ2, κ3.

The wavelength Doppler shift amount Δf varies depending on the scattering direction and is represented by the following equation. Δfn = (κn −κi) ・ υ / 2π (n = 1, 2, 3, ...)… (1)

Here, the component of the velocity vector υ is (υx,
νy, υz), and the X, Y, and Z direction components of the direction vector (κn −κi) of the scattered light with respect to the incident light are (κnx, κ
ny, κnz), the components of the blood flow velocity vector are obtained from the Doppler shift amounts in the three directions as follows.

Υx = {(κ2y · κ3z-κ2z · κ3y) · Δf1 + (-κ1y · κ3z + κ1z · κ3y) · Δf2 + (κ1y · κ2z-κ1z · κ2y) · Δf3} / A υy = {(-κ2x · κ3z + κ2z · κ3x) · Δf1 + (κ1x · κ3z-κ1z · κ3x) · Δf2 + (-κ1x · κ2z + κ1z · κ2x) · Δf3} / A υz = {(κ2x · κ3y − κ2y · κ3x) · Δf1 +・ Κ3z ＋ κ1y ・ κ3x) ・ Δf2 ＋ (κ1x ・ κ2y-κ1y ・ κ2x) ・ Δf3} / A However, A = κ1x ・ κ2y ・ κ3z ＋ κ1y ・ κ2z ・ κ3x ＋ κ1z ・ κ2x ・ κ3y −κ1z ・ κ2y ・ κ3x−κ1x ・ κ3x-κ1x κ3y − κ1y · κ2x · κ3x… (2)

In this equation (2), the three-dimensional velocity vector representing the true blood flow is measured in the three directions and the direction formed by the incident light and the three scattered lights determined as the parameters of the blood flow meter. This means that it can be calculated from the Doppler shift amount of scattered light. At this time, if the direction of scattered light with respect to the incident light is fixed, no matter what angle the fundus of the eye is relative to the measuring device or in which direction blood flows, the condition is blood flow. Not required as a parameter for flow measurement.

Next, a method of calculating the blood flow velocity without using the above equation (2) will be described. Blood flow velocity vector υ and scattered light
When the angle formed by Kn is close to 90 degrees, the absolute amount of velocity vector υ due to the reception of scattered light in two directions K1 and K2 becomes “Riva: Ap
plied Optics, Vol.18, No.13, 1 July 1979, pp2301 ~
2306 ”, it is calculated by the following equation (3). | Υ | = λ · (Δf1 -Δf2) / (n · α 12 · cosβ 12) ... (3)

Where λ is the wavelength of the incident laser light, n is the refractive index of the fluid medium in the eye, α ₁₂ is the angle between the directions K1 and K2, and β ₁₂ is the vector κ1 and κ2 in the directions K1 and K2. It is the angle formed by the projection of the velocity vector υ on the determined plane and the velocity vector υ.

When this formula (3) is applied to the case of receiving scattered light in three directions according to the present invention, the blood flow velocity vector υ is projected on the plane formed by the directions K1 and K2 and the plane formed by the directions K1 and K3. The absolute quantities │υ ₁₂ │ and │υ ₁₃ │ are respectively expressed by the following equation (4),
(5) ｜ υ ₁₂ ｜ ＝ ｜ υ ｜ ・ cosβ ₁₂ ＝ λ ・ (Δf1−Δf2) / (n ・ α ₁₂ ) ... (4) ｜ υ ₁₃ ｜ ＝ ｜ υ ｜ ・ cosβ ₁₃ = λ ・ (Δf1−Δf3) / (N · α ₁₃ ) (5)

Here, α ₁₃ is the angle between the directions K1 and K3, and the arithmetic processing is performed by the processor 164 using these expressions to obtain the velocity vector or the absolute amount of the velocity vector.

Direction K1 expressed by these two equations (4) and (5)
The velocity vector | υ | can be obtained from the component of the blood flow velocity projected on the two planes of the plane formed by K2 and K2 and the plane formed by the directions K1 and K3, and the angle formed by these two planes. That is, it means that the absolute amount of the velocity vector υ can be calculated from the angle formed by the scattered light in the three directions, which is determined as a parameter of the blood flow meter, and the Doppler shift amount of the scattered light measured in the three directions. There is. In this case, the vector in the incident direction Ki is not necessary for the calculation.

On the television monitor 165 shown in FIG. 12,
The fundus image Ea ′ and the measured blood flow value are displayed at the same time. V1 indicates the velocity vector of the blood flow that is currently being measured, and D1 indicates the absolute value of the blood flow as a numerical value. Furthermore, the velocity vectors at the measurement points designated last time and the time before last are V2 and V3, respectively, and the absolute value of the blood flow is D2 and V2, respectively.
It is shown to be displayed according to D3.

In this second embodiment, three photodetectors are used to detect scattered reflected light in three directions. However, one photodetector is used and the optical path switch is used as a photodetector. It is also possible to install it in front of and to obtain the Doppler shift amount by time division. At this time, by increasing the number of optical path switches, light in more than three directions can be detected, and the direction in which the vector synthesis is most accurate can be selected to measure the true blood flow.

[0069]

As described above, the fundus blood flow meter according to the first aspect of the present invention supplies the synchronizing signal from the synchronizing signal generating means to the blood flow velocity calculating means and the blood vessel diameter calculating means to thereby obtain the blood flow velocity. And the blood vessel diameter can be calculated at the same time in real time, and further, the blood flow volume that changes from moment to moment can be calculated from these results as needed. Further, it is possible to avoid the occurrence of a measurement error or the inability to measure due to the movement of the blood vessel to be measured, which is caused by the eye movement of the subject, the blood flow rate can be accurately measured, and more accurate ophthalmologic diagnosis is guaranteed.

In the fundus blood flow meter according to the second aspect of the invention, the angle spatially occupied by the optical axes of the laser irradiation light and the scattered detection light used during blood flow measurement and the blood flow direction of the fundus of the eye to be examined is the fundus. It is possible to eliminate the influence on the blood flow measurement result. This eliminates the need for a mechanism such as an image rotator, simplifies the device, and eliminates the need for aligning the blood vessel direction with the measurement direction for each examiner, which causes measurement errors due to misalignment. Since it can be avoided, an inexpensive and highly accurate fundus blood flow meter can be supplied. Also,
No skill is required to measure the fundus blood flow, and the measurement operation of the fundus blood flow in many actual medical facilities can be performed easily and highly accurately.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment.

FIG. 2 is a block circuit configuration diagram of a controller.

FIG. 3 is a timing chart diagram.

FIG. 4 is an explanatory diagram showing a relationship between an irradiation light beam and an observation light beam.

FIG. 5 is an explanatory diagram of an observation fundus image.

FIG. 6 is a block diagram of a blood flow velocity calculation unit.

FIG. 7 is a block diagram of a blood vessel diameter calculation unit.

FIG. 8 is a timing chart of the blood vessel diameter calculation unit.

FIG. 9 is a configuration diagram of a second embodiment.

FIG. 10 is an explanatory diagram showing a relationship between an eye to be inspected and measurement light.

FIG. 11 is an explanatory diagram of flow velocity vector calculation.

FIG. 12 is an explanatory diagram of a fundus image and a blood flow value on a television monitor.

FIG. 13 is a schematic diagram of a conventional example.

FIG. 14 is a graph of frequency analysis of a received light signal.

FIG. 15 is an explanatory diagram of an observation image.

[Description of Reference Signs] 31 Image Rotator 32a, 32b, 131a, 131b, 131c Small Mirror Pair 34 Image Stabilizer 35, 134 Observation Optical System 39, 138 Measurement Light Source 53, 56, 143, 146 Galvanometric Mirror 57, 147 Operation Rod 61, 151 Focusing lens 65, 154 Television camera 66, 165 Television monitor 67 Blood vessel detection system 71 CCD sensor 81 Blood flow velocity calculation unit 82 Blood flow amount calculation unit 84 Controller 85 Blood vessel diameter calculation unit 87 Synchronous signal generation circuit 133 Positioner 163a, 163b , 163c Signal processing unit

Claims (12)

[Claims] 1. An irradiation unit that guides coherent measurement light to a measurement site on the fundus, a condensing unit that collects scattered and reflected light from the measurement site, and a light beam that is collected by the condensing unit is detected. Detecting means, blood flow velocity calculating means for calculating the blood velocity flowing in the blood vessels of the fundus from the output of the detecting means, illuminating means for guiding illumination light to the measurement site or its vicinity, and an image of the illumination site on the imaging surface. An image pickup means for projecting onto the image pickup means, a blood vessel diameter calculation means for calculating a blood vessel diameter from the output of the image pickup means, a synchronization signal generation means for generating a synchronization signal a plurality of times within a predetermined time, and an output of the synchronization signal generation means. A fundus blood flow meter comprising: a control unit that causes the blood flow velocity calculation unit and the blood vessel diameter calculation unit to operate based on the blood flow velocity calculation unit. 2. An intraocular blood flow meter according to claim 1, further comprising a differentiating means for differentiating an output from said image pickup means and a blood vessel position calculating means for calculating a blood vessel position from the output of said differentiating means. 3. A second imaging means for imaging a fundus blood vessel, wherein when the fundus blood vessel moves relative to the second imaging means, the second imaging means detects the fundus blood vessel. The fundus blood flow meter according to claim 1, wherein the fundus blood flow meter automatically follows the movement amount. 4. The fundus blood flow meter according to claim 1, further comprising means for calculating a blood flow rate based on the outputs of the blood flow velocity calculation means and the blood vessel diameter calculation means. 5. The fundus blood flow meter according to claim 3, wherein the first imaging unit and the second imaging unit share an imaging optical system. 6. A light source for generating coherent light in a fundus blood flow meter for measuring the blood flow state of the fundus tissue by irradiating the fundus with a single light beam and analyzing the light flux obtained from the fundus tissue. Irradiation means for irradiating the measurement site with the luminous flux from
Detecting means for independently detecting the light flux obtained from the measurement site in at least three directions whose direction vectors are not on the same plane, and first signal processing for obtaining a Doppler shift component corresponding to the blood flow velocity from the output signal of the detecting means. Means for determining the blood flow velocity vector in the blood vessel or its absolute amount from the Doppler shift components of the light flux in at least three directions obtained from the measurement site and the detection direction information of the light flux obtained from the measurement site. A fundus blood flow meter, comprising: two signal processing means. 7. The fundus blood flow meter according to claim 6, wherein the light flux obtained from the measurement site is scattered reflection light or other light emission. 8. The first signal processing means detects a beat wave generated by a light beam having a wavelength Doppler-shifted by blood flow and a light beam scattered from a blood vessel wall or surrounding tissue and having the same wavelength as the irradiation light. The fundus blood flow meter according to claim 6, wherein a Doppler shift component obtained as a result is obtained. 9. The fundus blood flow meter according to claim 6, wherein the detection means are provided in the same number as the number of directions corresponding to the direction in which the light flux from the fundus tissue is detected. 10. The detection means and the first and second signal processing means are paired, and a switching mechanism is provided for guiding a signal to the detection means by switching the direction in which the light flux from the fundus tissue is detected. The fundus blood flow meter according to claim 6. 11. The fundus blood flow meter according to claim 6, wherein the measured blood flow velocity vector is displayed on an image display in superposition with the fundus image. 12. The coherent light irradiating a measurement site and a total of four optical axes of the light beams in three directions obtained from the measurement site and decomposed are arranged in a substantially square shape on the pupil. The fundus blood flow meter described in.