JPH07148170A - Optical biological measuring apparatus - Google Patents

Abstract

PURPOSE:To measure diffuse transmission reflected light from a wide irradiated area simultaneously by sending a beam on a point of an object to be measured and using a two-dimensional detector. CONSTITUTION:The decreasing rate of a luminous energy compensating filter 10 decreases from the center of the filter 10 radially and concentrically outward. The filter 10 has a bore at the center of concentric circles having each light decreasing rate, and an optical fiber 12 is passed through the bore and is fixed to the filter 10 using a shading ring 14. A near-infrared beam travels through the optical fiber 12 and irradiates the object. The diffuse transmission reflected light from the object travels through the filter 10 and is detected by a two-dimensional detector 18 facing the filter 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical biometric apparatus for irradiating a living body of a subject with near-infrared light and detecting the diffuse transmitted / reflected light to nondestructively obtain information in the subject. Is. Such an optical biometric device is used, for example, as a biological oxygen monitor or optical CT.

[0002]

2. Description of the Related Art Near-infrared rays in the range of 600 to 1200 nm have good permeability to living organisms and maintain sufficient intensity for measurement even after passing a distance of several cm in living organisms. Conveniently, since the absorption spectra of hemoglobin and cytochrome oxidase, which are important substances that reflect biological functions, exist in this wavelength range, this property of near-infrared light is utilized to eliminate biological functions. Invasive measurements are performed.

The near-infrared light is applied to the living body, and the near-infrared light is scattered at various parts of the living body and transmitted through the living body to be CC.
It is known that light is received by a two-dimensional detector such as a D camera and the absorption distribution inside the living body is imaged by calculation.

When the object to be measured is large, such as when the subject is an adult's head, the transmission measurement method in which the subject is sandwiched and the light receiving point is set on the side opposite to the light transmitting point is the light extinction amount. Is beyond the measurement range, so it cannot be performed. However,
As shown in (A), the light-sending fiber 1 is pressed against the subject 3, and the contact point with the subject 3 is used as the light-sending point, and a distance of several cm on the subject on the same side as the light-sending point. It is possible to measure the light diffusely transmitted and reflected in the living body by the light receiving fiber 2 at the light receiving point separated by r. As a result, a method for obtaining a signal inside the living body is performed in an oxygen monitor or the like. Hereinafter, such measurement light emitted at the light receiving point on the same side as the light transmitting point and away from the light transmitting point will be referred to as diffuse transmitted / reflected light. When the measurement light from the light transmitting point is diffused, transmitted and reflected in the subject 3,
Information within the measurement range 7 indicated by a broken line in (A) is obtained.

On the other hand, as shown in FIG. 1 (B), the measuring light from the light transmitting fiber 1 is spread by the lens 4 and the subject 3 is examined.
There is a method in which the detector 5 having a large area detects the diffuse reflection of the incident point of the subject 3 itself. In this case, information about the surface depth of the subject within 1 mm is obtained and used for measuring the color of the subject. FIG. 1B is an example of 45-degree incidence and 90-degree measurement. Even if the incident direction and the measurement direction are not limited to this example, the method of FIG. 1B is simply called a diffuse reflection method. The target method of the present invention is the diffuse transmission reflection method, which utilizes the point that information on the deep part of the subject can be obtained by separating the light transmitting point and the light receiving point.

[0006]

When a two-dimensional detector is used as the light receiving portion of the diffuse transmission reflection method, the amount of light that appears at the light receiving point greatly differs depending on the distance r between the light transmitting point and the light receiving point. As shown in FIG. 2 (A), when the measurement light is incident on the subject 7 of the living body from the light transmission point, the measurement light is diffused and transmitted to the light reception point on the same side as the light transmission point and separated by a distance rmm. The intensity of the reflected light is obtained by solving the diffusion equation for stationary light. The solution is given as the equation (7) in "APPLIED OPTICS" Vol. 28, PP. 2331-2336 (1989), for example. The following formula (1) is obtained by integrating the formula (7) with respect to time.

[0007]

[Equation 1]

Here, R (r) is the intensity of light per unit area at the light receiving point at a distance of rmm from the light transmitting point,
This is the intensity when the intensity of light incident on the light transmitting point is set to 1 per unit area. Therefore, the unit of R (r) is mm ^-2 . Z ₀ is a virtual incident depth, and Z ₀ = 1 mm. D
Is the diffusion coefficient, given by D = 1/3 (μa + μs'),
The unit is mm. μa is the absorption coefficient and μs' is the transport-corrected scattering coefficient.
Therefore, here, it is set to 2 mm ⁻¹ .

In equation (1), the absorption coefficient μa is 0.01 m.
The calculation results when m ⁻¹ and 0.02 mm ⁻¹ are shown in FIG. When the distance r between the light transmitting point and the light receiving point is 10 mm and when the distance r is 50 mm, the received light amount differs by several digits. Therefore, the dynamic range of a normal two-dimensional detector cannot be obtained. This means that it is not possible to measure simultaneously over a wide light receiving area when transmitting light from one point. An object of the present invention is to send light to a subject from one point and simultaneously measure diffuse transmitted reflected light over a wide light receiving area by using a two-dimensional detector.

[0010]

According to the present invention, a light transmitting means for irradiating a subject with measuring light from one light transmitting point of the subject,
A two-dimensional detector that detects the diffuse transmitted reflected light of the measurement light emitted from a large number of light receiving points on the subject away from the light transmitting point, and is provided between the subject and the two-dimensional detector. And a light amount compensation filter whose extinction rate decreases as the distance from the light transmission point increases toward the outside.

In a preferred aspect of the present invention, a light guide having a plurality of light guide paths bundled in a relative positional relationship with each other, one end surface of which is arranged to face a subject, and the other end surface of the light guide. From the light guide means for irradiating the subject with the measurement light through one light guide path of the light guide and the other end surface of the light guide other than the light guide path for light transmission at the other end surface of the light guide. It is installed between the two-dimensional detector that detects the diffuse transmitted and reflected light of the measurement light emitted from the light guide and the other end surface of the light guide and the two-dimensional detector. And a light amount compensation filter for

In a further preferred aspect of the present invention, the light transmitting means includes a light transmitting fiber for guiding the measurement light from the light source, and the light transmitting fiber is fixed or interlocked with a part of the light amount compensating filter, and the light amount compensating filter is provided. And the light transmitting fiber are simultaneously moved to scan the light transmitting point.

The light amount compensating filter reduces the transmitted light so as to compensate for the relationship that the diffuse transmitted reflected light is attenuated as the distance r from the light transmitting point to the light receiving point is increased as shown in FIG. 2B. The filter is designed so that the light rate decreases concentrically toward the outside.

[0014]

When the near-infrared light is made incident on the subject from one light-transmitting point and the two-dimensional distribution of the light diffusely transmitted and reflected in the subject is measured, the light quantity compensation filter is provided. When the sending point is located at the center of the filter,
The two-dimensional intensity distribution of light is compressed over a wide range of the distance r so that the light falls within the dynamic range of the two-dimensional detector over a wide area. When the light transmitting point is located at the center of the change in the extinction ratio of the filter, the detection signal can be easily processed, and the effect of compressing the two-dimensional intensity distribution of the light at the light receiving point is great. It should be noted that the extinction ratio of the filter may be smaller as it goes away from the light transmitting point, and the line connecting the points of equal transmissivity is not limited to the concentric circles, but may be a polygon, a hexagon, or the like. The extinction rate may change continuously or in steps. The point is that the two-dimensional intensity distribution of the emitted light may be compressed so that it falls within the dynamic range of the two-dimensional detector.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 shows a first embodiment. Reference numeral 10 is a light amount compensation filter according to the present invention, and its extinction ratio is set so as to decrease concentrically from the center toward the outside. A hole is opened in the center of the concentric circle of the extinction ratio of the filter 10, and one end of the light transmitting fiber 12 is passed through the hole, and the light transmitting ring 12 causes the light transmitting fiber 12 to move.
It is fixed to. The filter 10 is pressed against the subject 16 with the light transmitting fiber 12 fixed, and the subject is irradiated with near-infrared measurement light from the light transmitting fiber 12. The diffuse transmitted reflected light from the subject is emitted through the filter 10,
It is detected by the two-dimensional detector 18 provided so as to face the filter 10. The two-dimensional detector 18 is a detector including an optical system and a two-dimensional light receiving element, such as a CCD camera.

As shown in FIG. 4, the optical characteristics of the light quantity compensating filter 10 are such that the extinction ratio is the largest at the center,
It has the characteristic that it decreases concentrically toward the periphery. The solid line is an example of a filter designed so that the extinction ratio changes continuously, and the broken line is a filter designed so that the extinction ratio changes stepwise. A shaded portion 12a of the central portion is a hole into which the light transmitting fiber 12 is inserted, and a portion 14a around it, which is indicated by a broken line, is a portion of the light shielding ring 14. These parts cannot be measured because diffused / reflected light from the living body is not emitted.

The light amount compensating filter 10 can be obtained by exposing a photographic film so as to form a pattern showing a change in extinction ratio as shown in FIG. One method for concentrically adjusting the exposure amount is a method in which light is actually made incident on a living body from one point and the photographic film is exposed by the diffuse transmitted reflected light. In order to change the extinction ratio stepwise, films having different extinction ratios may be laminated concentrically. The present invention is not limited to how to make the light amount compensation filter 10.

In this embodiment, as shown in FIG.
The filter 10 is in close contact with the subject 16 and the optical fiber 1
Irradiate measurement light from 2. The diffuse transmitted reflected light from the subject 16 is strong near the light-sending point and attenuates as it goes away from the light-sending point as shown in FIG. 2 (B). However, the filter 10 having the extinction characteristic as shown in FIG.
Since the intensities of the light from the respective portions of the subject 16 that have passed through and are emitted are compensated to almost the same level, it is possible to measure a wide range at the same time. The measurement data is restored by dividing it by the extinction rate of the filter 10 which is known in advance.

If the light transmitting fiber 12 is fixed to the filter 10 as shown in FIG. 3, even if the light transmitting point is moved, the surrounding extinction ratio is automatically set to a required value. Shading ring 14
Although the shadowed part of the optical fiber 12 cannot be measured,
The information of those parts can be obtained by moving the light transmitting point, so there is no problem.

FIG. 5 shows a second embodiment. (A) is a schematic perspective view and (B) is a perspective view showing an optical compensation filter. Instead of directly observing the subject 16 with the two-dimensional detector 18, the subject 1 is examined by the light guide 20.
The two-dimensional information 6 is once guided to another plane, and the light emitted from the plane is observed by the two-dimensional detector 18.

The light guide 20 has a plurality of optical fibers bundled in a relative positional relationship with each other, and one end surface of which comes into contact with the subject 16. The other end surface of the light guide 20 serves as a light guide entrance / exit surface 22 and is guided to one end surface of the light guide scanning unit outer box 24. The optical compensation filter 10 is arranged on the light guide entrance / exit surface 22,
The light transmitting fiber 12 is fixed to the center of the concentric circle of the change of the extinction ratio of the optical compensation filter 10 as in the embodiment of FIG. In the light guide 20, the arrangement of the optical fibers on the end surface which is in contact with the subject 16 and the arrangement of the optical fibers on the light guide entrance / exit surface 22 are set to be the same.
The image of the subject 16 is reproduced on the light guide entrance / exit surface 22. The contact area between the light guide 20 and the subject 16 and the area of the light guide entrance / exit surface 22 do not necessarily have to be the same, and may be reproduced on the light guide entrance / exit surface 22 as a reduced or enlarged image. .

A two-dimensional detector 18 is disposed inside the light guide scanning unit outer box 24 so as to face the light guide entrance / exit surface 22 via the filter 10. The light emitted from the light transmitting fiber 12 is transmitted to the subject 16 via one optical fiber of the light guide 20, and the remaining optical fibers function as a light receiving fiber.

The light transmitting point can be scanned by moving the filter 10 in the vertical and horizontal directions as indicated by the arrow. In this way, a two-dimensional image of a large number of diffuse transmitted / reflected light when light is sequentially transmitted from all the optical fibers of the light guide 20 is obtained, and the two-dimensional image is obtained by calculation for obtaining the distribution of the absorber inside. Can be made with raw data.

In the embodiment of FIG. 5, by providing the light guide 20, (1) it can be applied even if the surface of the subject 16 is not flat, and (2) the light guide 20 in close contact with the subject 16 is fixed. Until now, light guide entrance / exit surface 2
3) that the light-sending point can be scanned by switching the light-sending fiber on the plane 2 and that (3) it is easy to shield light
It has one advantage. In the embodiment shown in FIG. 5, a required number of independent detectors may be arranged instead of the two-dimensional detector 18, and these detectors may be made to correspond one-to-one to the respective optical fibers of the light guide 22.

[0025]

According to the present invention, by providing a light quantity compensation filter, it becomes possible to perform diffuse transmission reflection measurement using a two-dimensional detector, and it is possible to obtain a large number of measurement point information at the same time.
Efficiency is improved. The present invention according to claim 2 can achieve the following effects when used for diffuse reflectance measurement. (1) It can be applied even if the surface of the subject is not flat. (2) The light-sending point can be changed by switching the light-sending fiber on the flat surface of the light guide entrance / exit surface while keeping the light guide in close contact with the subject. Being able to scan and easy to block light. Then, by further providing a light amount compensation filter, it can be used for diffuse transmission / reflection measurement. By fixing the optical fiber of the light transmitting means to the light amount compensation filter, it becomes possible to scan the light transmitting point while maintaining the dimming characteristic around the light transmitting point.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for comparing and explaining a diffuse transmission reflection method (A) and a diffuse reflection method (B).

2A and 2B are diagrams showing the intensity of diffuse transmitted reflected light in relation to the distance from a light transmitting point, FIG. 2A is a diagram schematically showing diffuse transmitted reflected light, and FIG. 2B is a diagram showing calculation results. is there.

FIG. 3 is a perspective view showing a first embodiment.

FIG. 4 is a diagram showing a dimming characteristic of a light quantity compensation filter in the embodiment.

5A and 5B are diagrams showing a second embodiment, wherein FIG. 5A is a schematic perspective view and FIG. 5B is a perspective view showing a light amount compensation filter.

[Explanation of symbols]

 10 Light Compensation Filter 12 Optical Fiber 14 Light-shielding Ring 16 Subject 18 Two-dimensional Detector 20 Light Guide

Claims (4)

[Claims] 1. A light transmitting means for irradiating a subject with measuring light from one light transmitting point of the subject, and diffuse transmission reflection light of the measuring light emitted from a large number of light receiving points on the subject distant from the light transmitting point. A two-dimensional detector that detects the light, and a light amount compensation filter that is provided between the subject and the two-dimensional detector, and that the extinction rate decreases toward the outside from the light-sending point and away from the light-sending point. An optical biometric device characterized by the above. 2. A light guide having a plurality of light guide paths bundled in a relative positional relationship with each other, one end surface of which is arranged to face a subject, and another light guide from the other end surface of the light guide. A light-transmitting means for irradiating a subject with measurement light through one light guide path, and a measurement exiting from a light guide path opposite to the other end surface of the light guide and other than the light guide path for light transmission at the other end surface of the light guide. An optical biometric device, comprising: a two-dimensional detector that detects diffuse transmitted / reflected light. 3. The optical biometric measurement according to claim 2, further comprising a light amount compensation filter having a reduced extinction ratio from the center to the outside between the other end surface of the light guide and the two-dimensional detector. apparatus. 4. The light transmitting means is provided with a light transmitting fiber for guiding the measuring light from the light source, and the light transmitting fiber is fixed or linked to a part of the light amount compensating filter, and the light amount compensating filter and the light transmitting fiber are simultaneously provided. The optical biometric device according to claim 1 or 3, wherein the optical biometric device is moved to scan the light transmitting point.