JPH08112262A - Rheometer - Google Patents

Abstract

PURPOSE: To obtain a rheometer which enables measurement with a wider measuring range without increasing a reading speed even in a fast bloodstream velocity by allowing the irradiation of a laser light intermittently at a shorter time interval than a specified time interval. CONSTITUTION: A microcomputer outputs a synchronous pulse to an emission synchronization circuit after a specified time T1 from a vertical synchronization signal TH and an emission synchronization circuit 8 outputs a drive signal to a laser light source section LD based on the synchronous pulse and a laser light is emitted. The driving of the light source is stopped after a specified time T2 to the subsequent vertical synchronous signal TH. In other words, a laser light P is made to irradiate a blood cell in an organic tissue intermittently at a time interval T2 shorter than a reading time interval T1 +T2 of image information. The reflected light is received with a solid image sensor and a signal charge based on the reflection is stored optically. The image information taken with the solid image sensor allows the removal of changes in speckle signal within the reading time interval to obtain a linear corresponding relationship between an AD value and a bloodstream velocity to a large bloodstream velocity area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a blood flow meter which irradiates a blood cell of a living tissue with laser light and detects a blood flow velocity based on a speckle signal reflected by the blood cell.

[0002]

2. Description of the Related Art Conventionally, there is known a blood flow meter which irradiates a blood cell of a living tissue with laser light and detects a blood flow velocity based on a speckle signal reflected by the blood cell. In this blood flow meter, an image formed by reflected light from a living tissue is guided onto an image sensor such as a solid-state image sensor CCD having N pixels, and based on an image signal from the solid-state image sensor, for example, 1 A plurality of frames are continuously stored at a rate of 540 frames per second. At this time, the image of each frame is an image accumulated during 1/540 seconds. Then, for the (m, n) -th pixel of the image sensor based on the stored image information, the k-th output is I _k (m, n), and the k + 1-th output is I _{k + 1} (m,
As n), an AD value (average difference) obtained by integrating the fluctuation rate of speckle in each pixel is calculated based on the following equation (see, for example, Japanese Patent Laid-Open No. 4-28348).

[0003]

[Equation 1] In this arithmetic expression, the denominator is for normalizing the output value of each pixel, whereby the factor caused by the difference in reflectance of the blood vessel part is removed, and the AD value is the fluctuation amount of speckles, that is, the velocity of blood flow. It becomes a function. This AD value indicates the velocity of blood flow. The calculation of this AD value is performed for each pixel,
The blood flow velocity is two-dimensionally displayed based on the AD value at each pixel obtained by this calculation. The relationship between the AD value and the blood flow velocity is shown by the solid line A in FIG. It has been experimentally confirmed that the AD value and the blood flow velocity correspond to each other in a region where the blood flow velocity is small. In addition, in FIG.
For convenience, ground glass is used to find the correspondence between the AD value and the speed.

[0004]

However, it has been experimentally confirmed that when the blood flow velocity exceeds a certain velocity, the fluctuation speed of the speckle signal tends to increase and the AD value tends to decrease. . The applicant of the present invention has the problem that the speckle fluctuation amount is very large with respect to the blood flow velocity, and when the blood flow velocity becomes high, the conventional blood flow meter will accumulate an image for 1/540 seconds. It was discovered that the speckle signal fluctuates during that time, and an image of the average light amount value of this fluctuation range is stored. In order to solve this problem, it is conceivable to further increase the reading speed and capture an image in a short time, but there is a limit to increasing the reading speed.

The present invention has been made for the purpose of solving the problems of the conventional blood flow meter, and widens the measurement range without increasing the reading speed even when the blood flow speed is high. An object is to provide a blood flow meter capable of measurement.

[0006]

The blood flowmeter according to claim 1 of the present application optically accumulates image information based on reflected light from an irradiation system and an irradiation system for irradiating blood cells of living tissue with laser light. , A solid-state image sensor for continuously reading out the light-accumulated image information at a predetermined time interval, and a plurality of frames of image information read from the solid-state image sensor are sequentially stored, and each of the stored image signals is stored. In the blood flowmeter for calculating the blood flow state of the blood cells based on the above, the laser light is intermittently irradiated at a time interval shorter than the predetermined time interval.

The blood flowmeter according to claim 2 of the present application optically accumulates image information based on reflected light from an irradiation system for irradiating blood cells of living tissue with laser light and the biological tissue, and this light accumulation is performed. A solid-state image sensor for continuously reading out image information at predetermined time intervals, and a plurality of frames of image information read out from the solid-state image sensor are sequentially stored, and the blood of the blood cells is stored based on the stored image signals. In a blood flow meter for calculating a flow state, light is accumulated in the solid-state imaging device at a time interval shorter than the predetermined time interval.

[0008]

According to the blood flowmeter of the first aspect of the present invention, the fundus is irradiated with the laser light at a time interval shorter than the time interval for reading the image information.

According to the blood flowmeter of the second aspect of the present invention, the image information optically accumulated is read out at a time interval shorter than the time interval at which the image information is read.

According to the blood flowmeter of the first and second aspects of the present invention, since the image information imaged by the solid-state image pickup device is much shorter than the read time interval, the specifications within the read time interval are specified. It is possible to eliminate the fluctuation of the signal.

[0011]

Embodiments of the blood flow meter according to the present invention will be described below with reference to the drawings.

[0012]

Embodiment 1 FIG. 2 is a schematic view of an optical system of a blood flow meter according to the present invention. In FIG. 2, 1 is an illumination system, 2 is an observation and photographing system, 3 is a fundus camera, and 4 is an eyepiece lens. 5, a solid-state image sensor, 6 a microcomputer as a processing control circuit, 7 a color display, 8 an emission synchronization circuit,
E is the eye to be inspected. The illumination system 1 has a visible light illumination light source unit and a laser light source unit LD, which are not shown. Visible light from the visible light illumination light source unit is guided to a perforated mirror 13 via a total reflection mirror 9, a relay lens 10, a dichroic mirror 11 that transmits visible light and reflects infrared light (wavelength 808 nm), and a relay lens 12. . The visible light reflected by the perforated mirror 13 becomes an annular light flux through the objective lens 14 and enters the eye E from the peripheral portion of the pupil, and the fundus Er is illuminated thereby.

The observation / photographing system 2 has an objective lens 14, a perforated mirror 13, a focusing lens 15, an imaging lens 16, and a dichroic mirror 17. The fundus camera 3 has a quick return mirror 18 and a film 19. The eyepiece lens unit 4 includes a field lens 20, a reflecting prism 21,
The eyepiece lens 22 is generally used. The dichroic mirror 17 reflects infrared light having a wavelength of 808 nm and transmits visible light.

The reflected light from the fundus Er is taken out from the central portion of the eye E to be examined, condensed by the objective lens 14, guided to the focusing lens 15 through the hole of the perforated mirror 13, and formed into an imaging lens. 16 causes the film 19 to have a fundus image Er ′.
Is imaged. Further, the fundus image E is passed through the eyepiece lens unit 4.
r'is observed. FIG. 3 shows a fundus image photographed or observed, and in this FIG. 3, 23 is an optic disc, 2
4 indicates a blood vessel.

The laser light emitted from the laser light source unit LD is guided to the dichroic mirror 11 via a reflection mirror 25 ', reflected by the dichroic mirror 11, and relay lens 12, perforated mirror 13, objective lens 14, It is guided to the fundus via the periphery of the pupil of the eye E to be inspected, and, for example, the blood cell region 25 of the biological tissue shown in FIG. 3 is irradiated. The laser light reflected by the fundus Er is the objective lens 14, the hole portion of the perforated mirror 13, and the focusing lens 1.
5, the light is guided to the dichroic mirror 17 via the imaging lens 16, is reflected by the dichroic mirror 17, and is guided to the solid-state imaging device 5.

The solid-state image pickup device 5 is a microcomputer 6
It is connected to the. As the solid-state image pickup element 5, for example, a frame transfer type is used. As shown in FIG. 4, the solid-state image sensor 5 includes a light receiving portion CCD 26 and a storage portion C.
The CD 27 and the horizontal transfer register 28 are roughly configured,
The signal charges accumulated in the light receiving portion CCD 26 are transferred to the accumulation portion CCD 27 at one time during the vertical blanking period, and the signal charges transferred to the accumulation portion CCD 27 are sequentially transferred from the horizontal transfer register 28 as an image signal S. It is taken out one by one.

This control is performed by the microcomputer 6. Here, the microcomputer 6 has five
The signal charge accumulated in the solid-state image sensor 5 is read out every 1/40 second, and in FIG.
Is a vertical synchronizing signal. The microcomputer 6 outputs a synchronization pulse to the emission synchronization circuit 8 after a predetermined time T1 from the vertical synchronization signal TH, and the emission synchronization circuit 8 outputs a drive signal to the laser light source unit LD based on this synchronization pulse.
As a result, the laser is emitted and the driving is stopped after a predetermined time T2 until the next vertical synchronizing signal signal TH. That is, the blood cells of the living tissue are intermittently irradiated with the laser light P at a time interval T2 shorter than the image information read time interval T1 + T2. The reflected light is received by the solid-state image sensor 5,
Signal charges based on the reflection of the laser light P are optically accumulated in the solid-state image sensor 5. This photo-accumulated signal charge is
The image signal S sequentially read out as an image signal from the horizontal transfer register 28 and read out from the solid-state image sensor 5 is 1
Each frame is recorded in a frame memory (not shown).

According to this embodiment, since the image information picked up by the solid-state image pickup device 5 is much shorter than the read time interval, the fluctuation of the speckle signal within the read time interval can be eliminated, and the broken line in FIG. As shown by B, a linear correspondence relationship between the AD value and the blood flow velocity was obtained up to a region where the blood flow velocity was large.

The microcomputer 6 superimposes the blood flow velocity obtained by the calculation on the fundus image and displays it on the color display 7 in color.

[0020]

Second Embodiment FIG. 6 shows an example in which an interline transfer system is used as the solid-state image sensor 5. The solid-state image sensor 5 is generally composed of a photoelectric conversion unit 29, a vertical transfer register 30, a horizontal transfer register 31, and a sweep drain 32. The photoelectric conversion unit 29 has each element 29a corresponding to each pixel. In the solid-state imaging device 5, the signal charges accumulated in the photoelectric conversion unit 29 are swept out and drained 3
2 is sequentially swept through, and at the time of photographing, the sweep is prohibited during the light accumulation time corresponding to the exposure time shown in FIG. The signal charge accumulated in the photoelectric conversion unit 29 is transferred to the vertical transfer register 30 by applying a sensor gate pulse SG to a transfer gate (not shown), and the signal charge transferred to the vertical transfer register 30 is generated by the vertical transfer pulse. The signal charges vertically transferred to the horizontal transfer register 31 every one horizontal scanning period and transferred to the horizontal transfer register 31 are read by the horizontal transfer clock pulse.

In this embodiment, as shown in FIG. 7, the sensor gate pulse SG is applied to the transfer gate at a time interval shorter than the read time from the vertical synchronizing signal TH to the vertical synchronizing signal TH, and is designated by the symbol Ts. The period shown is the exposure time. It should be noted that the period indicated by the symbol Th is a charge sweeping period in which light accumulation in the photoelectric conversion unit 29 is prohibited.

The operation and effect of this embodiment are almost the same as those of the frame transfer method.

A known structure can be used for these solid-state image pickup devices 5.

[0024]

According to the inventions of claims 1 and 2 of the present application, it is possible to perform measurement with a wide measurement range without increasing the reading speed even when the blood flow speed is high. That is, there is an effect that the linear correspondence between the AD value and the blood flow velocity can be expanded to a region where the blood flow velocity is large.

[Brief description of drawings]

FIG. 1 is a graph showing a correspondence relationship between a moving speed of a ground glass plate and an AV value.

FIG. 2 is a schematic diagram of an optical configuration of a blood flow meter according to the present invention.

FIG. 3 is a diagram showing an example of a fundus image.

FIG. 4 is an explanatory diagram of a frame transfer type solid-state imaging device.

5 is a diagram showing the timing of laser light irradiation and a vertical synchronization signal of a blood flow meter using the frame transfer type solid-state imaging device shown in FIG.

FIG. 6 is an explanatory diagram of an interline transfer type solid-state imaging device.

FIG. 7 is a diagram showing timings of light accumulation and a vertical synchronization signal in a blood flow meter using the interline transfer type solid-state imaging device shown in FIG.

[Explanation of symbols]

 1 ... Irradiation system 5 ... Solid-state image sensor S ... Image signal Er ... Fundus

Claims (2)

[Claims] 1. An irradiation system for irradiating blood cells of living tissue with laser light, and image information based on reflected light from biological tissue is optically accumulated, and the optically accumulated image information is continuously read at predetermined time intervals. In a blood flow meter for sequentially storing the image information for a plurality of frames read from the solid-state image sensor for, and calculating the blood flow state of the blood cells based on each of the stored image signals A blood flowmeter, characterized in that it is configured to irradiate laser light intermittently at a time interval shorter than the predetermined time interval. 2. An irradiation system for irradiating blood cells of a living tissue with a laser beam, and image information based on reflected light from the biological tissue is optically accumulated, and the optically accumulated image information is continuously read at predetermined time intervals. In a blood flow meter for sequentially storing the image information for a plurality of frames read from the solid-state image sensor for, and calculating the blood flow state of the blood cells based on each of the stored image signals A blood flowmeter, wherein the solid-state imaging device is configured to accumulate light at a time interval shorter than the predetermined time interval.