JPH09178660A - Method and apparatus for measurement of optical characteristic of light scattering object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply measure an anisotropic scattering parameter by a method wherein the intensity distribution of scattered and reflected light is measured in a part near the input point of beam light on an object and the optical characteristic value of the intensity distribution which agrees with the intensity distribution of a theoretical computation is found. SOLUTION: The light-output part 6 and the light-receiving part 8 of a light input and output element 2 are pressed to the surface of an object 5, a light source 3 is started, and thin beams light is input on an input point P on the object 5 through the output part 6. The input light is scattered inside the object 5, and a part is output as reflected light from the surface of the object 5. Scattered and reflected light whose intensity distribution depends on the scattering characteristic of the object 5 is received in a part near the input point P by the light receiving part 8 whose resolution is fine so as to be guided to a photodetector 12 by a light-receiving element 11. The photodetector 12 detects it so to be sent to a data acquisition system 13. The system 13 stores an intensity distribution by a theoretical computation regarding many scattering characteristics, and it estimates the scattering characteristic value of the object 5 having the scattering characteristic value of a corresponding intensity distribution when the intensity distribution which is measured by the photodetector 12 agrees with, or closely resembles, any intensity distribution by the theoretical computation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for measuring a parameter representing an optical characteristic of an object that scatters light, such as a food, an industrial material, a living body, and the like. This technology can be used for inspection of industrial materials such as plastics by light, food inspection by light, biological diagnosis by light, treatment by light, and the like.

[0002]

2. Description of the Related Art In the fields of inspection of industrial materials by light, food inspection by light, biological diagnosis by light, treatment by light, etc., it is important to investigate the scattering and absorption characteristics of an object that strongly scatters light. is there. The scattering characteristics include a scattering coefficient μ _s , an equivalent scattering coefficient μ _s ′, a scattering phase function (angular distribution) p (θ), and an anisotropic scattering parameter g. The absorption characteristics include an absorption coefficient μ _a . Several simple methods for measuring the equivalent scattering coefficient μ _s ′ and the absorption coefficient μ _a have been considered, but the measurement of other properties requires preparing a thin sample of 1 mm or less and requiring special and time-consuming measurement. (R.
A. Groenhuis et al. , “Scatt
ering and absoφtion of t
urbid materials determination
d from reflection measurement
ments. 1: Theory, "Applied O
ptics, Vol. 22, pp. 2456-246
2 (1983). And R. A. Groenhuis
et al. , "Scattering and a
bsorption of turbine material
ials determined from refl
action measurements. 2: Mea
surging methods and caliber
, "Applied Optics, Vol.
22, pp. 2463-2467 (1983) and the like).

[0003]

However, these conventional techniques irradiate a scatterer with a light beam, measure the intensity distribution of the scattered reflected light, and easily determine the equivalent scattering coefficient μ _s ′ and the absorption coefficient μ _a. This conventional technique measures the intensity distribution of reflected light by guiding the incident beam with an optical fiber and using a microscope or a single optical fiber to mechanically move the reflected light, This technique can measure the equivalent scattering coefficient and absorption coefficient of an object, but cannot measure anisotropic scattering parameters.

[0004] The present invention has been made in view of the above circumstances, and is a light scattering device capable of simply measuring anisotropic scattering parameters and also easily measuring other optical characteristics. It is an object of the present invention to provide a method and an apparatus for measuring the optical properties of an object.

[0005]

To solve this problem, the optical characteristic measuring method for a light-scattering object according to the present invention is designed so that a thin beam of light is made incident on an incident point on an object and a range in the vicinity of the incident point. It is characterized in that the intensity distribution of the scattered reflected light is measured, and the optical characteristic value of the intensity distribution that matches or approximates to the theoretical distribution is obtained and used as an estimated value.

The optical characteristic measuring device for a light-scattering object according to the present invention further comprises a light emitting element having a light emitting portion capable of contacting the surface of the object and a plurality of light receiving portions having a light receiving portion capable of contacting the surface of the object. The light emitting portion and the light receiving portion are closely arranged adjacent to each other, and the light receiving element is connected to a light intensity distribution detecting device.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings showing an embodiment. First, a measuring apparatus used when the method for measuring the optical characteristics of a light scattering object according to the present invention will be described.

In FIG. 1, reference numeral 1 denotes an optical characteristic measuring device. The optical characteristic measuring device 1 includes a light input / output element 2, a light source device 3, and a light intensity distribution detecting device 4. As shown in FIGS. 2 and 3, the light input / output element 2 includes a light output element 7 having a light output unit 6 at the tip end capable of contacting the surface of the object 5,
A plurality of light-receiving elements 11 each having a light-receiving section 8 at the front end capable of contacting the surface of the object 5 are provided with a light-emitting section 6 and a light-receiving section 8 respectively.
Are tightly bound together in a region surrounded by the non-reflection region 9. The base end of the light emitting element 7 is connected to the light source device 3, and the base end of the light receiving element 11 is connected to the light intensity distribution detecting device 4. The light intensity distribution detection device 4 has a light detector 12 and a data acquisition device 13. In this embodiment, each of the light emitting element 7 and the light receiving element 11 is constituted by an optical fiber. If the diameter of the core of the optical fiber is about 0.1 mm, the light emitting section 6 and the light receiving section 8 are densely arranged in a straight line. The length of a straight line when about 50 pieces are arranged next to each other is about 5 mm. The light emitting portion 6 and the light receiving portion 8 of the light input / output device 2 are, in addition, a CC in which CCD elements and photodiodes 14 are arranged in a matrix as shown in FIG.
The light receiving section 8 may be configured with the light receiving surface of the D camera, and the light emitting section 6 made of an optical fiber or the like may be arranged at the center or end of the light receiving section 8. Further, as shown in FIG.
The light receiving section 8 may be configured by arranging a D element or a photodiode 14 and the light emitting section 6 made of an optical fiber or the like may be arranged at the center or at the end. The data acquisition device 13 is composed of a computer.

The method for measuring the optical characteristics of a light-scattering object according to the present invention is carried out as follows using the optical characteristic measuring apparatus constructed as described above.

First, the light emitting part 6 and the light receiving part 8 of the light input / output element 2 are pressed against the surface of the object 5, and in this state, the light source device 3 of the optical characteristic measuring device 1 is started, and the thin beam light, for example, the diameter is reduced. A light beam of 0.1 mm or less is incident on an incident point P on the object 5 through the light emitting section 6 of the light input / output element 2. The incident light is scattered in the object 5 and a part of the light is emitted from the surface of the object 5 as scattered reflected light. The intensity distribution of the scattered reflected light depends on the scattering characteristics (scattering coefficient μ _s , equivalent scattering coefficient μ _s ′), scattering phase function (angle distribution) p (θ), and anisotropic scattering parameter g. The light reflected from the object 5 is received by the light receiving unit 8 having a spatial resolution of about 0.1 mm in the vicinity of the incident point P, for example, in a range of about 5 mm from the incident point P, and the light is guided by the light receiving element 11. Detector 1
2 and sends the signal to the data acquisition device 13 to determine the light intensity distribution. On the other hand, the data acquisition device 13 has a curve A (g = 0.6) and a curve B (g = 0.
7), a large number of scattering characteristics, such as C (g = 0.8), are calculated by intensity calculation by theoretical calculation and accumulated. When the measured intensity distribution of the scattered reflected light coincides with or approximates to the intensity distribution obtained by any theoretical calculation, the scattering characteristic value of the intensity distribution obtained by the corresponding theoretical calculation is estimated as the scattering characteristic value of the object 5. In the case of the example shown in FIG. 6, the measured intensity distribution D of the scattered reflected light is close to the intensity distribution A obtained by theoretical calculation.
6. It is estimated that the equivalent scattering coefficient μ _s ′ is 1.0 mm ⁻¹ . Scattered and reflected light from the object 5 in a range far from the incident point,
For example, if a scattered / reflected light intensity distribution in a range of 5 mm or more from the incident point P is used, the absorption coefficient μ _a can also be determined by _a conventional method.

[0011]

EXAMPLE A suspension of latex particles having a particle size of d = 0.65 μm was used as an object, and an optical fiber having a diameter of 0.5 mm was connected to 25
A light emitting element having a width of 12.5 mm was formed by binding the books so that all the tips are aligned in a straight line, and one of the light emitting elements was used as a light emitting element, and the rest was measured as a light receiving element. FIG. 7 shows the results. It can be seen that the equivalent scattering coefficient μ _s ′ and the anisotropic scattering parameter g match well between the measured value and the theoretical value.

[0012]

According to the present invention, a large number (several tens) of optical fibers are arranged in a line, one end is in contact with the object to be measured, a part of the multi-end is introduced into a light source, and the rest is introduced into a photodetector. The fiber connected to the light source is one of the endmost fibers in the line, and the remaining fibers are connected to the detector. The detector measures the distribution of the scattered reflected light that irradiates the object, scatters inside, and returns to the surface. By examining the intensity distribution of the scattered reflected light, an anisotropic scattering parameter and an equivalent scattering coefficient μ _s ′ among light scattering characteristics of the object are obtained. Thus, in the present invention, a number of fibers are arranged in a line, light is incident on one of the ends, and scattered and reflected light is guided to the detector by the other fibers. Thus, the fiber can be spatially resolved by the thickness of the fiber (0.02 mm to 0.50 mm), and the intensity distribution can be measured at one time. As described above, according to the present invention, fibers and the like are arranged in a line, light is incident on one of the ends thereof, and detection is performed by another fiber, so that the spatial resolution is good. The intensity distribution can be measured. However, as described above, the measurement of the scattered reflected light does not necessarily need to be guided by a fiber, and an optical sensor such as a CCD or a photodiode arranged in a line (one-dimensionally) may be used. However, the scattered reflected light must be measured from very close to the incident point. Alternatively, a small hole is made in the center of an optical sensor such as a two-dimensionally arranged CCD to irradiate the object with incident light, or one of the arranged CCD sensors is irradiated with a semiconductor laser or a light emitting device. It may be a light emitter such as a diode.

As is apparent from the above description, according to the present invention, the anisotropic scattering parameter can be easily measured, and at the same time, other optical characteristics can be easily measured. Characteristic measurement methods and equipment can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view of an optical characteristic measuring device of a light scattering object.

FIG. 2 is an explanatory view of an end view of a distal end portion of a fiber bundle.

FIG. 3 is an explanatory side view of the tip of the fiber bundle.

FIG. 4 is a structural explanatory view of a light input / output element using a two-dimensional CCD light sensor.

FIG. 5 is a structural explanatory view of a light input / output element using a one-dimensional CCD light sensor.

FIG. 6 is a graph showing the measurement principle of the anisotropic scattering parameter and the equivalent scattering coefficient.

FIG. 7 is a graph showing a comparison between a theoretical value and a measured value of a reflected light intensity distribution and a measured value and a theoretical value of an anisotropic scattering parameter and an equivalent scattering coefficient μ _s ′.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 optical characteristic measuring device 2 light input / output element 3 light source device 4 light intensity distribution detecting device 5 object 6 light emitting unit 7 light emitting element 8 light receiving unit 9 non-reflection area 11 light receiving element 12 light detector 13 data acquisition device 14 CCD Photodetectors such as elements and photodiodes

Claims (5)

[Claims] 1. A narrow beam of light is made incident on an incident point on an object, the intensity distribution of scattered reflected light in a range in the vicinity of the incident point is measured, and the intensity distribution of the intensity distribution that agrees with or approximates to the theoretical intensity distribution is measured. A method for measuring optical characteristics of a light-scattering object, characterized in that an optical characteristic value is obtained and used as an estimated value. 2. The method for measuring optical characteristics of a light-scattering object according to claim 1, wherein the beam light has a diameter of about 0.1 mm, and the range is 5 mm or more from the incident point. 3. A light emitting element having a light emitting portion capable of contacting the surface of an object and a plurality of light receiving elements having a light receiving portion capable of contacting the surface of the object, the light emitting portion and the light receiving portion. Are closely arranged, and the light receiving elements are connected to a light intensity distribution detecting device. An optical characteristic measuring device for a light scattering object. 4. The apparatus according to claim 3, wherein the light emitting element and the light receiving element are optical fibers. 5. The apparatus according to claim 3, wherein the light receiving element is an optical sensor.