JPH11118716A - Method and apparatus for optical inspection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To visualize a deep area up to several millimeter under the cuticle where a melanin pigment is present by selectively detecting luminescence generated from a part where a non-scattering component of an inspection light entering an object to be inspected is condensed. SOLUTION: An inspection light 23 enters a sample 35 through a lens 31 and a non-scattering component of the light is condensed to an inspection part 37. A scattering light and luminescence generated at an image formation area pass through the lens 31, are reflected at mirrors 29, 27 and enter a space filter 20. The filter 20 selectively passes the scattering light and luminescence. The luminescence passes a dichroic mirror 19 and enters a sharp cut filter 51, where the scattering light is removed. The luminescence out from the filter 51 enters a spectroscope 57 through a mirror 53. The spectroscope 57 separates the luminescence for every wavelength and guides to a photodetector 59. The photodetector 59 detects intensities, and an analyzing part 61 displays at a CRT 63 an area 65 of the sample 35 where a lot of melanin pigment is present.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical inspection method and an optical inspection apparatus for non-invasively measuring the internal structure of an optical scatterer (test object) represented by a biological tissue. In particular, the present invention relates to an optical inspection method and an optical inspection device that enable visualization of a spatial region where melanin pigment and the like contained in skin are present.

[0002]

2. Description of the Related Art X-ray CT, MRI, ultrasonic tomography, PET and the like have been put to practical use as a method for non-invasively measuring anatomical information and pathological / physiological information of a living tissue. Further, attempts have been made to visualize tissue structure changes that cannot be visualized by these measurement techniques using light waves. This technical field is generally called optical CT technology (see Applied Physics, Vol. 62, No. 1, p10-17, etc.).

There are roughly two types of optical CT.
One is a method for detecting forward scattered transmitted light, and the other is a method for detecting back scattered light. In optical CT, an electromagnetic wave from visible light to near-infrared light, which has relatively little absorption in a living body, is usually used as incident light (inspection light). In comparison, the scattering in the living body is strong and the scattering process is very complicated (for example, The Journal of Investigative Der
matology, Vol. 77, No. 1, p13-19 (1981) Reference 1). In order to visualize the internal structure with high accuracy by detecting the forward scattered transmitted light, how to mathematically process the scattering process remains as a difficult subject. On the other hand, attempts to visualize the structure of the tissue surface layer by detecting backscattered light have been performed using several methods, and a relatively accurate internal image has been obtained (for example,
Dermatology, Vol. 186, p50-54 (1993) Reference 2, Sc
ience, Vol. 254, p1178-1181 (1991) Reference 3].

[0004]

For example, in the above Reference 2, a Nipkow disk is mounted on a confocal optical microscope,
A device capable of rapidly visualizing the three-dimensional structure of the skin has been proposed. According to this method, it is possible to visualize the structure at about 100 microns on the surface of the skin. However, due to scattering, it is not possible to image deeper internal structures.

[0005] It is an object of the present invention to provide an optical inspection method and an optical inspection apparatus which enable visualization of a melanin pigment existing region up to several millimeters beneath the epidermis.

[0006]

In order to solve the above-mentioned problems, an optical inspection method according to the present invention irradiates inspection light to an object having spatially non-uniform light absorption characteristics and light scattering characteristics. Then, the non-scattering component of the inspection light that has entered the test object is condensed on an arbitrary portion within the test object, and luminescence generated from the portion is selectively detected, and the wavelength-intensity of the detected luminescence is detected. The characteristic is measured, and a part in the test object showing the characteristic having a specific tendency is displayed.

Further, the optical inspection apparatus of the present invention irradiates an inspection object having spatially non-uniform light absorption characteristics and light scattering characteristics with inspection light and enters the inspection light into the inspection object. An irradiating optical system for condensing the non-scattered component on an arbitrary portion in the test object, a detecting optical system for selectively detecting luminescence generated from the portion, and a spectroscopic means for dispersing the detected luminescence. A photodetector for measuring the intensity of the separated luminescence; and characteristic display means for displaying the characteristics of the wavelength and the intensity of the separated luminescence in association with the site in the test object. And

[0008] When the constituent material of the tissue portion to be observed emits luminescence different from that of other tissue constituent materials, the difference in luminescence is detected and displayed by imaging or the like, so that the deeper structure of the tissue can be invaded in a non-invasive manner. Observable.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of an optical inspection apparatus according to one embodiment of the present invention. This optical inspection device has a light source 11 such as an argon laser. The light source 11 has a wavelength of 48.
Emit inspection light 12 of 8 nm or 514 nm. Inspection light 1
2 passes through an isolator 13 disposed on the exit side of the light source 11 for preventing return reflection, and
Is incident on an optical chopper 15 disposed on the exit side of the optical chopper. The optical chopper 15 is a light intensity modulator that repeats passing and blocking light at a predetermined short cycle. The signal-to-noise ratio is increased by extracting, as a signal, only a component synchronized with the frequency (for example, 2 kHz) of the optical chopper 15 from the output of the photodetector 59 described later.

The light exiting the optical chopper 15 strikes a mirror 17 disposed on the exit side of the optical chopper 15 and is reflected downward in the figure. The light reflected by the mirror 17 is
The light enters the dichroic mirror 19. In this embodiment, the dichroic mirror 19 is set so as to reflect the inspection light having a wavelength of 488 nm and pass the luminescence 50 (emitted from a sample 35 described later) having a wavelength of about 500 nm or more longer than the inspection light. . The dichroic mirror 19 is placed at a point where an optical axis of an irradiation optical system that emits inspection light in the direction of the sample 35 and an optical axis of an optical system that detects luminescence emitted from the sample intersect.

The inspection light reflected by the dichroic mirror 19 is incident on a spatial filter 20 including two convex lenses 21 and 25 and a pinhole 23 disposed between the two lenses. The inspection light is condensed by the lens 21, passes through the pinhole 23, and becomes a parallel light beam by the lens 25. The pinhole 23 has a conjugate relationship with a measurement site 37 in the sample 35 described later, and an image of the pinhole is formed on the measurement site 37 in the sample 35. Further, the scattered light and luminescence generated from the measurement site 37 are selectively generated in the pinhole 2.
Pass 3 The diameter of the pinhole 23 is set to be several times or less (for example, 1 to 3 μm or less) the inspection light (for example, argon laser wavelength around 500 nm).

The inspection light that has passed through the lens 25 and has become a parallel light beam enters a deflector composed of two movable mirrors 27 and 29 (such as galvanometer mirrors) arranged on the exit side of the lens 25. This deflector reflects the inspection light downward in the drawing and scans the inspection light in a plane perpendicular to the optical axis of the sample 35.

The inspection light reflected by the movable mirror 29 enters an objective lens 31 disposed on the exit side of the mirror. The inspection light is collected by the objective lens 31 toward the inspection site 37 in the sample 35. Here is sample 3
Reference numeral 5 denotes a substance having a considerably large light absorption and light scattering like human skin, and only a small part (non-scattering component) of the light irradiated from the objective lens 31 to the surface of the sample 35 is condensed on the inspection part 37. . However, information for estimating the structure inside the sample 35 can be obtained by selectively detecting the luminescence as an action of this small part of the non-scattering component and performing signal processing.

The objective lens 31 is movable in the optical axis direction by a driving mechanism 33 such as a ball screw or a piezoelectric actuator. This movement of the objective lens 31 can change the position (depth) of the inspection part 37 in the optical axis direction. In this embodiment, the sample 35 is mounted on the moving stage 41, and the stage 41 can be moved up and down to change the position of the inspection part 37 in the optical axis direction.

The sample 35 is fixed on a sample holder 39. The sample holder 39 is placed on the moving stage 41. Stage 41 is sample 3
5 is moved in the optical axis direction and the plane perpendicular to the optical axis, and the inspection site is three-dimensionally scanned in the object to be inspected.

As described above, the inspection light forms an image on the inspection portion 37 in the sample 35, and the scattered light and luminescence (fluorescence, phosphorescence, etc.) generated in the image formation area of the inspection light have a fixed solid angle. Originally, the light enters the objective lens 31, passes through the lens 31, is reflected by the mirrors 29 and 27, and is reflected by the spatial filter 20.
to go into. As described above, the filter 20 selectively transmits the scattered light and the luminescence generated from the imaging region of the inspection site 37 as described above. The light that has passed through the spatial filter 20 impinges on the dichroic mirror 19 described above. At this time,
From the characteristics of the dichroic mirror, the scattered light is reflected by the dichroic mirror 19 because it has the same wavelength as the inspection light. On the other hand, since the luminescence has a longer wavelength than the inspection light, it passes through the dichroic mirror 19 to the left in the drawing.

The light that has passed through the dichroic mirror 19 then enters the sharp cut filter 51, where scattered light partially mixed with the luminescence is removed. The luminescence emitted from the filter 51 enters a spectroscope 57 via a mirror 53 and a lens 55.

The spectroscope 57 divides the luminescence for each wavelength and guides the luminescence to the photodetector 59. As the spectral optical system, a dispersion medium such as a diffraction grating and a prism, a multilayer film reflecting mirror (dichroic mirror), a color glass filter, and the like can be used. The photodetector 59 detects the intensity for each luminescence wavelength. The output of the photodetector 59 is sent to an analyzer 61 constituted by a microcomputer or the like after only the modulation component synchronized with the frequency of the optical chopper 15 is amplified. The analysis unit 61 performs a process described below,
An image signal is supplied to 63, and an area 65 particularly rich in melanin pigment inside the sample is displayed on the screen. If necessary, the output of the detector can be calculated in an electric circuit.

Next, an example in which a human skin tissue is inspected using the optical inspection apparatus shown in FIG. 1 will be described. FIG. 2 is a graph showing the result of spectroscopic analysis of a human skin tissue sample using the optical inspection apparatus of FIG. The horizontal axis is the wavelength of luminescence (nm), and the vertical axis is the luminescence intensity (arbitrary unit). The target test tissues in each of the graphs A to D are (A) a stratum corneum, (B) a region where melanin pigments are concentrated (melanocytes), (C) a dermis, and (D) a fat layer.

Referring to each graph of FIG. 2, (A) stratum corneum,
Both (C) the dermis and (D) the fat layer have a peak near 550 nm, and the longer wavelength side is a curve that is generally downwardly sloping downward. On the other hand, only (B) melanocyte is a two-bred camel-like curve having one more peak near 630 nm. Therefore, the first wavelength is set to around 560 nm, the second wavelength is set to around 630 nm, and a portion where the intensity of the second wavelength ÷ the intensity of the first wavelength is equal to or more than a certain value is displayed as a portion suspected to be a melanocyte. If this is generalized, a specific tendency will be grasped by comparing the intensities of different wavelengths in luminescence from one site.

FIG. 3 is a graph in which the vertical axis represents the value (intensity ratio) obtained by dividing the luminescence intensity at 630 nm by the luminescence intensity at 560 nm, and the horizontal axis represents the depth of the inspection site. That is, it is a graph in which a change in the intensity ratio is examined while scanning the sample in the depth direction. In FIG. 3, the clear peaks are 160 μm, 310 μm, and 460 μm in depth.
m, 640 μm, 800 μm, and a total of 6 in the vicinity of 1040 μm. Here, for example, by displaying an image of a portion having an intensity ratio of 1 or more while scanning the inspection site also in the direction perpendicular to the optical axis, it is possible to display an area under the skin estimated to be melanocytes.

In this example, the case of melanocytes has been described. However, if the luminescence spectrum is different from that of other tissue structures, the existence region can be estimated using the apparatus of the present invention.

FIG. 4 is a diagram showing a configuration of an optical inspection apparatus according to another embodiment of the present invention. This optical inspection apparatus differs from the optical inspection apparatus of FIG. 1 in the following points. (1) A polarizing beam splitter 101 for separating scattered light from the inspection site 37 and a photodetector 103 for measuring the intensity of the scattered light are provided. That is, the polarizing beam splitter 101 and the quarter-wave plate are arranged in this order between the isolator 13 and the dichroic mirror 19. The inspection light emitted from the polarization beam splitter 101 is reflected by the dichroic mirror 19 to the right in the drawing through the quarter-wave plate 105, passes through the spatial filter 20, the galvanomirrors 27 and 29, and the objective lens 31, and returns to the sample 35. The inspection site 37 is reached. The scattered light emitted from the inspection site 37 returns to the optical path in the opposite direction and returns to the dichroic mirror 19.
Come back to. Since the scattered light has basically the same wavelength as the inspection light, it is reflected by the dichroic mirror 19 upward in the figure,
The light again passes through the quarter-wave plate 105 and enters the polarization beam splitter 101. At this time, since the scattered light has passed through the quarter-wave plate 105 twice after exiting the light source 11, the phase of the light has changed by 90 °. Therefore, the scattered light is reflected by the polarizing beam splitter 101 to the left side of the drawing, and the scattered light 102
Is extracted as The scattered light 102 is transmitted to the light detector 10
3 and the intensity is measured.

(2) The spectroscope comprises a second dichroic mirror 121 and two photodetectors 123 and 125. That is, the luminescence that has passed through the sharp cut filter 51 is deflected by the mirror 53 and then enters the second dichroic mirror 121. This mirror is 5
It is designed so that light having a wavelength near 60 nm is almost reflected, and light near 630 nm is almost transmitted. These wavelength-separated lights are detected by 123 and 125 light detectors. As for the output signals of the three optical detectors 123, 125, and 103, only the intensity modulation component of the optical chopper is amplified using a synchronization signal detection device such as a lock-in amplifier, if necessary. If the luminescence is weak, a photomultiplier can be used for the light detectors 123 and 125. These wavelength-separated light intensity signals are input to an arithmetic unit 127, the ratio of which is output, and input and recorded in a computer.

A procedure for measuring the test object 35 will be described. First, the test object 35 is fixed to the stage 41. When the objective lens 31 is moved closer to the test object 35, a strong signal is observed by the optical detector 103 when the laser focuses on the surface of the test object. By using this position as a reference, it is easy to compare structures in the object. Next, the objective lens 31 is brought closer to the object by a desired distance by the movable arm 111 attached to the stage 41, and in this state, optical signals are detected by the photodetectors 123 and 125. This signal ratio is recorded in correspondence with the position of the movable arm 111. By repeating this operation at different arm positions by moving the stage 41, the region where melanin exists in the test object becomes clear.

In the present embodiment, an argon laser is used as a light source, but a near-infrared laser or an infrared laser having a high permeability to tissue can also be used.

[0027]

As is clear from the above description, according to the present invention, it is possible to clarify the existing region of the structure emitting different luminescence inside the tissue. For example, it is possible to visualize the region where the melanin pigment exists up to several millimeters under the epidermis.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an optical inspection device according to one embodiment of the present invention.

FIG. 2 is a graph showing a result of spectral analysis of a human skin tissue sample using the optical inspection apparatus of FIG. 1; The horizontal axis is the wavelength of luminescence (nm), and the vertical axis is the luminescence intensity (arbitrary unit).

FIG. 3 shows a value (intensity ratio) obtained by dividing the intensity of luminescence at 630 nm by the intensity of luminescence at 560 nm on the vertical axis.
It is the graph which expressed the depth of the test | inspection part on a horizontal axis.

FIG. 4 is a diagram showing a configuration of an optical inspection device according to another embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 11 light source 12 inspection light 13 isolator 15 optical chopper 17 mirror 19 dichroic mirror 20 spatial filter 21 lens 23 pinhole 25 lens 27, 29 movable mirror 31 objective lens 33 drive mechanism 35 sample 37 measurement site 39 sample holder 41 moving stage 50 luminescence Reference Signs List 51 Sharp cut filter 53 Mirror 55 Lens 57 Spectroscope 59 Photodetector 61 Analytical unit 63 CRT 65 Region with many melanin pigments 101 Polarized beam splitter 102 Scattered light 103 Photodetector 105 Quarter wave plate 111 Movable arm 121 Second Dichroic mirror 123, 125 Optical detector 127 Arithmetic unit

Claims (6)

[Claims] 1. An inspection object having spatially non-uniform light absorption characteristics and light scattering characteristics is irradiated with inspection light, and a non-scattering component of the inspection light entering the inspection object is extracted from the inspection object. Focus on an arbitrary site in the body, selectively detect the luminescence generated from the site, measure the wavelength-intensity characteristics of the detected luminescence, and determine the site in the test object where the characteristics show a specific tendency. An optical inspection method characterized by displaying: 2. The method according to claim 1, wherein the specific tendency is grasped by comparing the intensity of the luminescence of the first wavelength and the intensity of the luminescence of the second wavelength in the luminescence from one part. Optical inspection method. 3. The method according to claim 2, wherein the first wavelength is around 560 nm,
3. The optical device according to claim 2, wherein the second wavelength is around 630 nm, and a region where the intensity of the second wavelength ÷ the intensity of the first wavelength is equal to or more than a certain value is displayed as a site suspected to be a melanocyte. Inspection methods. 4. A test object having spatially non-uniform light absorption characteristics and light scattering characteristics is irradiated with test light, and a non-scattered component of the test light entering the test object is extracted from the test object. An irradiation optical system for condensing light on an arbitrary part in the body, a detection optical system for selectively detecting luminescence generated from the part, a spectroscopic means for dispersing the detected luminescence, and a measurement of the intensity of the separated luminescence An optical inspection apparatus, comprising: a photodetector that emits light; and a characteristic display unit that displays characteristics of the wavelength and intensity of the separated luminescence corresponding to a part in the test object. 5. The method according to claim 1, wherein the characteristic display means compares the intensity of the luminescence of the first wavelength and the intensity of the luminescence of the second wavelength during the luminescence from one part to grasp and display the specific tendency. The optical inspection apparatus according to claim 4, wherein: 6. The method according to claim 1, wherein the first wavelength is around 560 nm,
6. The optical device according to claim 5, wherein the second wavelength is around 630 nm, and a portion where the intensity of the second wavelength ÷ the intensity of the first wavelength is equal to or more than a certain value is displayed as a portion suspected to be a melanocyte. Inspection equipment.