JP2708381B2 - Optical image measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical image measuring apparatus for irradiating a measurement object with a light beam such as a laser beam instead of an X-ray source to generate a two-dimensional image.

[0002]

2. Description of the Related Art Substances such as living organisms, dense fog, fumes, thick clouds, sprays, and polluted water are generally opaque media due to multiple scattering of light. In order to image the internal state of a measurement object or the shape of an object that is naturally or artificially covered with an artificial coating such as paint or plastic, a light beam is applied to the target object. It is necessary to detect light that has been irradiated and transmitted through the object or light reflected from inside the object. In this case, it is necessary to selectively and highly sensitively distinguish signal light that travels substantially linearly in a specific direction and has required information from scattered light generated in the object and spreading in all directions. As a method for this distinction, there are a temporal distinction method and a spatial distinction method.

[0003] As a method of time distinction, for example,
BBDas, KMYoo, and RRAlfano "Ultrafast time-ga
ted imaging in thick tissues: a step toward optica
lmammography "Optics letters, Vol. 18, pp1092-10
94 (1993). In this method, for example, an ultrashort light pulse having an extremely short time width of 10 ^-12 seconds or less is incident on the measurement unit, and a time gate is installed in front of a detector for detecting light. By passing only the portion that seems to be the straight traveling light that reaches first, the straight traveling light and the scattered light are distinguished.

On the other hand, as a method of spatial distinction, for example,
M. Toida, M. Kondo, H. Ichimura, and H. Inaba, "Experi
mental verification of image detection in highly
scattering media using antenna properties of optic
al heterodynemicroscope scheme ", Electronics lette
rs, Vol. 26, pp. 700-701 (1990). This method uses an optical heterodyne detection method. By superimposing a light beam from a local oscillator on a signal light, only the straight light component of the received light that matches the wavefront of the light beam from the local oscillator is enhanced. Detection is possible with sensitivity.

In order to improve the spatial resolution,
The following methods (a) and (b) are employed. (a) A method of focusing a light beam on an object to be measured.

This method is described, for example, in JAIzatt, MRHee,
GMOwen, EASwanson, and JGFujimoto, "Optical
coherence microscopy in scattering media "OpticsL
etters, Vol. 19, pp. 590-592 (1994). However, this is a method developed for samples as thin as, for example, 1 mm. When the sample is irradiated with light, the light is strongly scattered before reaching the deep part of the sample, and it is difficult to focus the light on the deep part of the thick sample. Therefore, in this method, there is a limit to the thickness of the sample that can be measured, and this method is not suitable for thick scatterers. (b) A method of irradiating a sample with a light beam made thin and parallel.

In the case of this method, the spatial resolution is substantially determined by the size of the beam diameter, and the spatial resolution can be improved as the beam diameter decreases. However, it is extremely difficult to propagate a parallel beam with a narrow diffraction limit into a thick scatterer. Further, in a medium having a complicated refractive index distribution such as a biological system, there is a problem that the beam diameter becomes non-uniform.

[0008]

Incidentally, recently, an optical heterodyne laser microscope having a high spatial resolution has been developed. An example of this is T.Sawatari "Optical he
terodyne scanning microscope "Applsed Optics, Vol
12, pp 2768-2772 (1973). Many of these types of microscopes are of the focused beam type and are intended exclusively for samples with a thickness of the order of hundreds of μm to 1 mm. Therefore, it is not suitable for measuring a thick sample.

Further, among such microscopes, there is a method of irradiating a sample with a parallel light beam. In this method, reflected light from a minute scatterer is detected while moving a point light source as reference light, and the position of the scatterer is determined from the relationship between the light intensity and the movement position.

[0010] As described above, the conventional devices are all limited to thin samples, and are not suitable for relatively thick samples having a thickness of several mm to several cm. In addition, a spatial scan of the probe beam is required to generate a two-dimensional image, so that it takes a long time for the measurement and the apparatus configuration becomes large.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method of measuring light transmitted through a relatively thick measurement object that becomes opaque due to multiple scattering of light, or measurement object. Optical image that can detect light reflected from inside with high spatial resolution and generate a two-dimensional or three-dimensional image in real time without scanning the object It is intended to provide a measuring device.

[0012]

SUMMARY OF THE INVENTION The present invention, first it focusing light transmitting through the irradiation means, the measurement object is irradiated with light which is expanded to a first beam diameter on the measurement object including a scatterer 1
A lens as a spatial filter provided at the focal point of the first lens, and a second lens for expanding light passing through the aperture to a second beam diameter larger than the first beam diameter. Irradiating the measurement object
The frequency that shifts the frequency of light having the same frequency as
The frequency is shifted by the shift means and the frequency shift means.
Third lens for expanding the shifted light and generating a reference light
When the generated light that is enlarged by the second lens
Synthesizing means for synthesizing the reference light, the light synthesized by the synthesizing means were separated by two-dimensional space, wherein the frequency sheet
Photoelectric conversion means for converting into an electric signal of an intermediate frequency component corresponding to the shift .

Further, the present invention provides an irradiating means for irradiating a measuring object including a scatterer with light expanded to a first beam diameter, and condensing light transmitted through the measuring object or reflected from the measuring object. as well as, frequency and first telescope to expand the beam diameter to a larger second beam diameter than said first beam diameter, for the irradiation light to the measurement object
Frequency shifting means for generating a number-shifted reference light;
The reference light generated by the frequency shift means is reduced.
Both of which expand to a beam diameter equal to the second beam diameter.
2 telescopes, and light expanded by the second telescope to light expanded by the first telescope.
And combining means for combining the reference light, the light synthesized by the synthesizing means were separated by two-dimensional space, wherein the frequency shift
And a photoelectric conversion means for converting into an electric signal of an intermediate frequency component corresponding to the above.

Further, the present invention provides an irradiating means for irradiating a measuring object including a scatterer with light expanded to a first beam diameter, and spatial filtering of light transmitted through the measuring object or reflected from the measuring object. And the first bead.
The reference light is generated by shifting the frequency of the expanded light
A frequency shifter, a synthesizer that synthesizes the filtered light with the reference light generated by the frequency shifter , and a second light that is larger than the first beam diameter by combining the light synthesized by the synthesizer. A telescope that expands to a beam diameter, and the light that is expanded by this telescope is separated in a two-dimensional space to support the frequency shift
And a photoelectric conversion unit for converting the electric signal into an intermediate frequency component electric signal.

[0015]

The telescope has a first lens for condensing light, an aperture as a spatial filter provided at a focal point of the first lens, and a second lens for expanding a beam diameter of light passing through the aperture. Lens.

The photoelectric conversion means moves a plurality of one-dimensional or two-dimensionally arranged photoelectric conversion elements or at least one photoelectric conversion element in a one-dimensional or two-dimensional space by a driving means. Furthermore, irradiating means for irradiating a light expanded in the first beam diameter on the measurement object comprises scatterers, means for spatial filtering the light reflected from the light or the measurement object has passed through the measurement object, the first Like beam
A circuit that shifts the frequency of the expanded light to generate a reference light
Wave number shifting means, and the spatially filtered light
Synthesizing means for synthesizing the reference light generated by the frequency shifting means, a plurality of optical fibers having one end arranged two-dimensionally or one-dimensionally , and the synthesized light incident on one end, and each of the optical fibers provided at the other end, an intermediate corresponding light guided by the optical fiber to said frequency shift
A plurality of two-dimensional or one-dimensional photoelectric conversion elements for converting the electric signals into electric signals of frequency components . In addition, the synthesizing means
The combined light by the telescope to the first beam diameter.
To a larger second beam diameter and guide it to an optical fiber
Is also good.

[0018]

That is, the irradiating means irradiates the measuring object including the scatterer with light having a large beam diameter, and the telescope condenses the light transmitted through the measuring object or the light reflected from the measuring object, and performs spatial filtering. The beam diameter is expanded again. The combining means combines reference light with the light expanded by the telescope, and the combined light is separated in a two-dimensional space by the photoelectric conversion means and converted into a required electric signal.

As described above, the light transmitted through the measuring object or the light having a large beam diameter reflected from the measuring object is further expanded by the telescope or the beam expanding means, so that the beam can be remotely scanned in real time without scanning the beam. High spatial resolution two-dimensional or three-dimensional imaging can be performed objectively or nondestructively.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the principle of the present invention will be described. In FIG. 1, a sample 11 as a measurement object is irradiated with a laser beam 12 having an enlarged diameter. The laser light (referred to as signal light) transmitted through the sample 11 is transmitted through a telescope TS.
Passes through a first lens 13, an aperture 14, and a second lens 15 which constitute the objective lens of FIG.
Is incident on. Local oscillation light (hereinafter, referred to as local light or reference light) 17 is incident on the beam splitter 16, the local light 17 is superimposed on the signal light, and these beat light components are converted into a plurality of photoelectric conversion elements 18. Are detected by the photodetector array 19 arranged two-dimensionally. Each photoelectric conversion element 18 receives incident light in a space geometrically determined by the beam shape of the local light, and performs photoelectric conversion for heterodyne detection.

The multiple scattered light generated in the sample 11, the refracted light caused by the internal structure and state of the sample 11,
Noise light such as diffracted light has a higher spatial frequency on the Fourier transform plane than straight traveling light. Therefore, spatial filtering is performed by the aperture 14 disposed on the focal plane of the first lens 13 of the telescope TS. Nevertheless, the scattered light that reaches the light receiving surface of the detector array 19 is reflected by the light receiving angle (fieled
of view) Only components having an incident angle smaller than θ (approximately λ / D, λ is the wavelength, and D is the diameter of the photoelectric conversion element 18) are detected, and spatial sorting with extremely high performance can be performed.

Therefore, the light receiving aperture D _A of the laser beam 12 projected onto the sample is such that the focal length of the first lens 13 is f ₁ , the focal length of the second lens 15 is f ₂ , and the magnification M =
When f ₂ / f ₁ and the distance from the second lens 15 to the light receiving surface of the photoelectric conversion element 18 are L, D _A = (D + θL) / M approximately. For measuring the spatial resolution is approximately equal to D _A, it is seen that depending on the size of the diameter of the incident light.

The spatial resolution can be improved by increasing the magnification M of the telescope. For this reason, the spatial resolution of several tens μm or less is reduced to the normal several hundred μm.
It can be easily realized with a photoelectric conversion element 18 having a diameter of μm and a telescope magnification of about 10 times.

If the diameter of the photoelectric conversion element 18 is reduced, the light receiving angle of the optical heterodyne detection is increased, and the directivity of each photoelectric conversion element is reduced. Therefore, the size of the photoelectric conversion element is reduced. There are limitations.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 2 shows a first embodiment of the present invention. In FIG. 2, a laser oscillator 21 generates a laser beam LB. The type of the laser oscillator 21, the wavelength and output characteristics of the laser light, for example, the output, the polarization plane, and in the case of a pulse, the pulse width and the peak output can be changed according to the sample. The wavelength is, for example, 0.6 to 1.3 in the case of a living body.
μm is appropriate, and about 9 to 10μ for fog or smoke
m, 0.4 to 0.5 μm is appropriate for sewage or turbid water. Laser light L generated from the laser oscillator 21
B is split by a beam splitter 22, one of which is incident on a beam expander 23.
The laser light whose diameter has been enlarged by the beam expander 23 is incident on the sample 24. The sample 24 is placed on, for example, a movable table (not shown), and the movable table allows the sample 24 to move in the horizontal and vertical (up and down) directions. The laser light (signal light) transmitted through the sample 24 is condensed by an objective lens 26 forming a first telescope 25, passes through an aperture 27 as a spatial filter, and then forms a first telescope 25. Enlarged by lens 28. The expanded signal light is incident on the beam splitter 29.

On the other hand, the other laser beam split by the beam splitter 22 is supplied to a photoacoustic modulator 31 via a mirror 30. In this photoacoustic modulator 31, the laser light is shifted in frequency to generate a local light (reference light) LCB. The beam diameter of the local light LCB is expanded by the lenses 33 and 34 forming the second telescope 32. A first and a second telescope 25,
32 are the same as each other, or the magnification of the second telescope 32 is made larger than that of the first telescope 25,
The diameter of the local light is the same as or larger than the signal light.

The local light whose diameter has been enlarged by the second telescope 32 enters the beam splitter 29 via a mirror 35 and is superimposed on the signal light. The beat light component generated as a result of the wavefront synthesis by the beam splitter 29 is detected by the photodetector array 36. The photodetector array 36 is configured by, for example, arranging a plurality of photoelectric conversion elements 37 two-dimensionally. The photoelectric conversion element 37 is, for example, a PIN photodiode,
An optical semiconductor element such as an avalanche photodiode is applied.

The signal output from the photodetector array 36 is supplied, for example, in a time series to a signal processing section 38 comprising a demodulator, an analog / digital converter and the like, where it is demodulated and digitized. The output signal of the signal processing unit 38 is supplied to a computer 39, and a two-dimensional image is generated by a known process. The generated image is supplied to the display 40 and displayed.

According to the first embodiment, the sample 24
Noise light such as multiple scattered light generated within the sample, refracted light and diffracted light resulting from the internal structure and state of the sample 24 is spatially filtered by an aperture 27 disposed on a focal plane of a lens 26 of the first telescope 25. Is done. Nevertheless, the scattered light that reaches the light receiving surface of the photoelectric conversion element 37 is
Only components having an incident angle smaller than the light receiving angle of the photoelectric conversion element 37 are detected. Therefore, extremely high-resolution spatial sorting becomes possible.

The spatial resolution can be improved by enlarging the signal light transmitted through the sample 24 using a telescope. Therefore, a spatial resolution of several tens of μm or less can be easily realized by a normal photodetector array having photoelectric conversion elements having a diameter of several hundred μm and a telescope having a magnification of about 10 times.

Further, the diameter of the laser beam is expanded by the beam expander, and the expanded laser beam is irradiated on the sample. Therefore, an image of a predetermined area of the sample can be generated as a two-dimensional image without scanning the sample with a laser beam, so that the size of the apparatus can be reduced.

In the first embodiment, the sample 24
The signal light transmitted through was enlarged using a telescope,
The signal light reflected from the sample 24 may be enlarged using a telescope and used for detecting a two-dimensional image based on the reflected light.

Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment,
The same portions as those in the first embodiment are denoted by the same reference numerals, and only different portions will be described.

Although two telescopes are used in the first embodiment, one telescope is used in this embodiment. That is, the diameter of the laser light generated from the laser oscillator 21 is expanded by the beam expander 23. The laser beam whose diameter is enlarged is split by the beam splitter 22, and one of the beams is incident on the sample 24. The signal light transmitted through the sample 24 is condensed by the lens 41, passes through the aperture 27, and is enlarged by the lens 42. The magnifications of the lenses 41 and 42 are, for example, the same. The expanded signal light is incident on the beam splitter 29.

On the other hand, the other laser beam split by the beam splitter 22
Is supplied to the photoacoustic modulator 31 via the. The local light LCB generated by the photoacoustic modulator 31 is incident on the beam splitter 29 via a lens 44 and a mirror 35,
Superimposed on the signal light. This beam splitter 2
The light wave-synthesized by 9 is supplied to a beam expander 45. The beam expander 45 is a so-called telescope, and expands a beam diameter and performs collimation. The combined light whose diameter has been enlarged by the beam expander 45 is detected by the photodetector array 36.

According to the second embodiment, after the signal light and the local light are combined, the beam diameter is expanded and collimated by the beam expander 45. Therefore, 1
Spatial resolution can be improved with only one telescope. Moreover, the telescope and the photodetector array 3
The spatial resolution can be further improved by extremely narrowing the distance from the gap 6. Further, by selecting only the magnification of the beam expander 45, the spatial resolution of the apparatus can be freely selected.

FIG. 4 shows a third embodiment of the present invention. Although the first and second embodiments have described the transmission type apparatus for detecting the light transmitted through the sample, this embodiment shows a reflection type apparatus for detecting the light reflected from the sample. The same parts as those in the first and second embodiments are denoted by the same reference numerals.

In FIG. 4, a laser beam LB generated by a laser oscillator 21 is expanded in diameter by a beam expander 23 and is incident on a beam splitter 22. One of the laser beams split by the beam splitter 22 is supplied to a polarization beam splitter (PBS) 46 and a λ / 4 plate 4.
7 sequentially enters the sample 24. The laser light (signal light) reflected by the sample 24 is λ /
4 plate 47, through polarizing beam splitter 46
1 is incident. Since the signal light incident on the lens 41 passes through the λ / 4 plate 47 twice, the signal light undergoes a rotation of the polarization plane corresponding to a phase change of λ / 2. The signal light condensed by the lens 41 and passed through the aperture 27 is made parallel by the lens 42 and is incident on the beam splitter 29.

On the other hand, the other laser beam split by the beam splitter 22 is supplied to a photoacoustic modulator 31. The frequency-shifted local light LCB output from the photoacoustic modulator 31 is incident on the beam splitter 29 via the λ / 2 plate 48 and the mirror 35, and is superimposed on the signal light. The light wave-synthesized by the beam splitter 29 is supplied to the beam expander 45. The light whose diameter has been expanded by the beam expander 45 is detected by the photodetector array 36. According to this embodiment, the same effects as those of the first and second embodiments can be obtained.

FIG. 5 shows a fourth embodiment of the present invention, in which the present invention is applied to an optical interferometer system using the same principle as that of the third embodiment. . In FIG. 5, the light source 51 is a low coherent light source,
For example, it is composed of a super luminescent diode and a light emitting diode. The beam generated from the light source 51 passes through the beam expander 23, enters the beam splitter 22, and is split. One of the beams enters the sample 24, and the beam reflected by the sample 24 enters the beam splitter 22 again. The other beam split by the beam splitter 22 is incident on, for example, a mirror 52 constituting a frequency shifter. The mirror 52 is reciprocally movable along the optical axis, and the frequency of the beam is shifted by the mirror 52 to generate a local light LCB. As the frequency shifter, for example, a photoacoustic modulator that can give the same frequency shift as that of the mirror 52 can be used. Local light LC reflected by the mirror 52
B is re-incident on the beam splitter 22 and is combined with the reflected light from the sample 24. The combined light is used as a lens 26 constituting a telescope, an aperture 27 for spatial filtering, and a lens 2 for expanding a beam diameter.
Go through 8. The combined light whose diameter is enlarged by the lens 28 is detected by the photodetector array 36.

As described above, by using a low coherent light source, information in the depth direction of the sample can be obtained. Therefore, by using this optical interferometer system, a three-dimensional image with high spatial resolution can be obtained.

FIG. 6 shows a fifth embodiment of the present invention, and the same parts as those in FIG. 5 are denoted by the same reference numerals. This embodiment shows a configuration for measuring an image by using reflected light and transmitted light from a sample using the optical interferometer system shown in FIG.

In FIG. 6, a mirror 52a is provided behind the sample 24. For this reason, the reflected light from the sample 24 and the sample 24
, Is reflected by the mirror 52a, and the transmitted light that has passed through the sample 24 again provides image information in which both overlap.

Then, next, the light transmitted through the sample 24 is reflected by the mirror 52a so as not to return to the beam splitter 22 again. That is, information of only the reflected light is taken out from the photodetector array 36 that has performed the same operation as in FIG. 5, and this information is subtracted from the previously obtained image information of the overlapped reflected light and transmitted light, thereby obtaining It is possible to detect image information based on transmitted light that has transmitted through the sample 24 twice. Furthermore, by repeating such an operation, it is possible to construct a two-dimensional image by transmitted light and reflected light almost simultaneously. In order to perform such an operation, a mechanical or electrical mechanism such as periodically moving or tilting the mirror 52a out of the optical path may be provided.

FIG. 7 shows a sixth embodiment of the present invention, which is a combination of the transmission type shown in FIG. 3 and the reflection type shown in FIG. 7, the same parts as those in FIGS. 3 and 4 are denoted by the same reference numerals. With such a configuration, the transmitted light and the reflected light from the sample 24 can be measured at the same time, and two-dimensional images of both can be obtained simultaneously in real time.

FIG. 8 shows a seventh embodiment of the present invention, which is a modification of the first embodiment, and shows only a part of the first embodiment. The first embodiment uses the photodetector array 36 in which a plurality of photoelectric conversion elements are two-dimensionally arranged. In this embodiment, a single photoelectric conversion element 71 is two-dimensionally moved by a driving unit 72. It is what it was. The two-dimensional image can be obtained by moving the photoelectric conversion element 71 two-dimensionally and processing the output signal of the photoelectric conversion element 71 in a time-series manner as in the first embodiment.

According to this embodiment, the photodetector array 36
As in the case where is used, a two-dimensional image with high spatial resolution can be obtained. In this embodiment, the number of photoelectric conversion elements is not limited to a single one, but is a one-dimensional photodetector array in which a plurality of photoelectric conversion elements are arranged one-dimensionally, and this photodetector array is orthogonal to the array direction of the photoelectric conversion elements. You may move in the direction in which you do.

FIG. 9 shows the configuration of the two-dimensional photodetector array. This photodetector array is, for example, shown in FIG.
As shown in (a), a plurality of photoelectric conversion elements 37 are N × N
FIG. 9 (b)
As shown in FIG. 7, a plurality of photoelectric conversion elements 37 are concentrically arranged two-dimensionally. The photodetector array 36 shown in FIG. 9B has high efficiency because it is similar to the beam shapes of the signal light and the local light.

FIG. 10 shows a configuration example of a photodetector array having an arbitrary shape and size using an optical fiber. The photodetector array 91 detects the combined light of the signal light and the local light through the optical fiber bundle 93. One end of an optical fiber bundle 93 in which a plurality of optical fibers 92 are bundled constitutes a light receiving section, and a photoelectric conversion element 96 is provided at the other end of each optical fiber 92.
The combined light of the signal light and the local light is incident on the light receiving unit. The shape and size of the light receiving unit are set so as to match the shape and size of the light beam obtained by combining the signal light and the local light. However, since the optical fiber bundle is used, the size and arrangement of the photoelectric conversion element 96 are changed. The method is completely arbitrary, and the photoelectric conversion element 96 can be installed at a place far away from the light receiving section. As described above, the combined light can be detected by each of the photoelectric conversion elements 96 provided at the other end of each of the optical fibers 92. Further, by using the optical fiber bundle, any shape and any shape can be obtained. A two-dimensional photodetector array having a size of

FIG. 11 specifically shows the signal processing system shown in FIG. FIG. 11A shows a photodetector array 36.
This is an example in which the output signals of the photodetector array 36 are processed in time series.
Is connected. The output signal of each photoelectric conversion element 37 is sequentially extracted by the switch circuit 101 and supplied to the computer 39 via the signal processing unit 102 including a demodulator and the like.

FIG. 11B shows an example in which the output signals of the photodetector array 36 are processed in parallel.
A signal processing unit 103 including a demodulator and the like is connected to each of the photoelectric conversion elements 37 of No. 6. These output signals of the signal processing unit 103 are supplied to the computer 38 in parallel.

FIGS. 12 (a), 12 (b) and 12 (c) show the structures of the signal processing units 38, 102 and 103, respectively. In FIG. 12A, an intermediate frequency output signal IFS, which is an output signal of the photodetector array 36, is supplied to an amplifier 38.
a, is supplied to a square detector (DET) 38c via a band-pass filter (BPF) 38b. This square detector 3
The detection output signal 8c is rectified by a rectifier circuit (RECT) 38d, and only a low-pass component is extracted by a low-pass filter (LPF) 38e. The output signal of the low-pass filter 38e is supplied to an analog / digital converter (A
/ D) is converted into a digital signal by 38f and supplied to the computer 39.

In FIG. 12B, the photodetector array 3
The intermediate frequency output signal IFS from 6 is supplied to a rectifier circuit 38i via an amplifier 38g and a band-pass filter 38h. The rectified output signal of the rectifier circuit 38i is supplied to an analog / digital converter 38 via a low-pass filter 38j.
k, converted into a digital signal, and supplied to the computer 39.

In FIG. 12C, the photodetector array 3
6 is supplied to one input terminal of the lock-in amplifier 38l. A reference signal (synchronous detection signal) RFS for the lock-in amplifier is supplied to the other input terminal of the lock-in amplifier 38l. As the reference signal RFS, for example, an intermediate frequency output or a modulation signal obtained by modulating a signal light at an appropriate modulation frequency is used. This lock-in amplifier 38l is suitable for detecting a narrow band of a signal synchronized with the frequency of the reference signal. This detection output signal is supplied to an analog / digital converter 38m, converted into a digital signal, and then supplied to a computer 39. The signal processing unit using this lock-in amplifier can improve the signal-to-noise ratio.

Next, actual experimental results will be described.
With the configuration shown in FIG. 8, a one-dimensional image output could be obtained by irradiating the sample with laser light and moving a single photoelectric conversion element in the horizontal direction. As a sample, for example, a pattern based on the U.S. NBS (National Standards Agency), that is, a test chart composed of bars 50 μm wide and 50 μm apart, 2 cm thick
Are placed. Therefore, the laser beam applied to the sample passes through the test chart and then the scatterer. The positional relationship between the test chart and the scatterer may be reversed. The laser used in this experiment was λ = 0.8μ
m, the diameter of the beam = 1 mm, the magnification of the telescope is 11 times, and the diameter of the photoelectric conversion element is 400 μm.

As the scatterer, intralipid -10% fat emulsion for intravenous injection was mixed with physiological saline to give 1% intralipid -10%. Intralipid-10% is commonly used for simulating biological systems. At a wavelength of about 1 μm, it is said that a mixed solution of 2% concentration of intralipid-10% and 98% of water shows almost the same scattering characteristics as human breast meat. Also,
It is said that if the intralipid has a concentration of 1.5%, the scattering property is close to that of chicken. Therefore, the sample is considered to correspond to a human breast with a thickness of 1 cm in terms of scattering characteristics.

In this experiment, the laser light applied to the sample was strongly scattered in the intralipid liquid, but only the light component that passed through the intralipid liquid almost linearly was detected by optical heterodyne detection. That is, the portion where the laser light is blocked by the bar has a transmittance of 0%, and the portion located between the bars has the transmittance of 100% because the laser light is transmitted therethrough. . Therefore, five peaks of transmittance were detected for five bars, and the mutual interval was detected to be 100 μm. Thus, it can be said that five 50 μm-wide bars were completely separated and detected. Therefore, it was confirmed that the resolution of the image of this device was better than 50 μm.

Similarly, according to the structure shown in FIG. 8, a human body having a diameter of 60 μm is placed behind a human hair having a thickness of 4 cm.
The sample was irradiated with laser light by placing 1% concentration of intralipid-10%, and a single photoelectric conversion element was moved in the horizontal direction, whereby a one-dimensional image could be detected. That is, it was possible to reliably detect human hair having a diameter of 60 μm through a 4% -thick 1% concentration intralipid-10%.

In the above embodiment, a laser in an optical region, a superluminescent diode or a light emitting diode as a low coherent light source is used as the irradiation light, but an electromagnetic wave region such as a microwave or a far infrared ray can be applied. It is. Of course, various modifications can be made without departing from the spirit of the invention.

[0060]

As described above in detail, according to the present invention, light transmitted through a relatively thick measuring object which becomes opaque due to multiple scattering of light or light reflected from the measuring object can be obtained with high spatial resolution. It is possible to provide an optical image measurement device capable of detecting and capable of non-destructively generating a two-dimensional or three-dimensional image in real time without scanning a measurement object with a light beam.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing the principle of the present invention.

FIG. 2 is a configuration diagram showing a first embodiment of the present invention.

FIG. 3 is a configuration diagram showing a second embodiment of the present invention.

FIG. 4 is a configuration diagram showing a third embodiment of the present invention.

FIG. 5 is a configuration diagram showing a fourth embodiment of the present invention.

FIG. 6 is a configuration diagram showing a fifth embodiment of the present invention.

FIG. 7 is a configuration diagram showing a sixth embodiment of the present invention.

FIG. 8 shows a seventh embodiment of the present invention, and is a configuration diagram showing only a part of the first embodiment.

FIG. 9 is a plan view showing a two-dimensional photodetector array.

FIG. 10 is a configuration diagram showing a modification of the photodetector array.

FIG. 11 is a configuration diagram specifically showing a signal processing system.

FIG. 12 is a configuration diagram specifically showing a signal processing unit.

[Explanation of symbols]

TS: Telescope, 11, 24: Sample, 14, 2
7 ... Aperture, 16, 29 ... Beam splitter, 1
8, 37, 71, 96: photoelectric conversion element, 19, 36: photodetector array, 21: laser oscillator, 23, 45: beam expander, 25: first telescope, 31: photoacoustic modulator (A / O), 32... Second telescope, 38, 1
02, 103 ... signal processing unit, 39 ... computer, 40
... Displays, 41, 42 ... Lens, 46 ... Polarization beam splitter, 51 ... Light source, 72 ... Driver, 92 ... Optical fiber, 93 ... Optical fiber bundle, 94 ... Branch coupler, 1
01 ... Switch circuit.

Continuation of the front page (56) References JP-A-3-111737 (JP, A) JP-A-4-27844 (JP, A) JP-A-2-111346 (JP, A) JP-A-2-150747 (JP) JP-A-2-110345 (JP, A) JP-A-3-72238 (JP, A) JP-A-4-34337 (JP, A) JP-A-51-98072 (JP, A) 2-240545 (JP, A) JP-A-4-31746 (JP, A)

Claims (8)

(57) [Claims] 1. First beam diameterExpanded toLight scatterer
Irradiating means for irradiating a measurement object including: and condensing light transmitted through the measurement objectFirstA first lens and a spatial filter provided at the focal point of the first lens.
And the light passing through the aperture is larger than the first beam diameter.
A second lens that expands to a second beam diameter,Light having the same frequency as the light irradiated on the measurement object
Frequency shifting means for shifting the frequency of Light whose frequency has been shifted by the frequency shifting means
A third lens that expands and generates a reference beam; Said To the light magnified by the second lensSaid generated
WasCombining means for combining the reference light, and the light combined by the combining means separated in a two-dimensional space
AndOf the intermediate frequency component corresponding to the frequency shiftTelegraph
And photoelectric conversion means for converting the
Optical image measurement device. 2. A scatterer for emitting light expanded to a first beam diameter.
Irradiating means for irradiating the measurement object including: light transmitted through the measurement object or light reflected from the measurement object
And the beam diameter of the first beam
Expand to a second beam diameter larger than the diameterFirstTelesco
AndThe frequency shifts with respect to the light applied to the measurement object.
Frequency shifting means for generating the reference light, The reference light generated by the frequency shift means is reduced.
Both of which expand to a beam diameter equal to the second beam diameter.
Two telescopes, The first To the light magnified by the telescopeThe said
Magnified by two telescopesWhen combining reference light
And the light combined by this combining means in a two-dimensional space
AndOf the intermediate frequency component corresponding to the frequency shiftTelegraph
And photoelectric conversion means for converting the
Optical image measurement device. 3. A scatterer for emitting light expanded to a first beam diameter.
Irradiating means for irradiating the measurement object including: light transmitted through the measurement object or light reflected from the measurement object
Means for spatially filteringThe frequency of the light expanded similarly to the first beam is shifted.
Frequency shift means for generating a reference light; Said To the filtered lightTo the frequency shift means
GeneratedCombining means for combining reference light, and the first beam
Expand to a second beam diameter larger than the diameterTelescope
And thisTelescopeLight expanded by two-dimensional space
Separate andOf the intermediate frequency component corresponding to the frequency shiftElectric
And photoelectric conversion means for converting the signal into an air signal.
Optical image measurement device. 4. The telescope includes a first lens for condensing light, an aperture as a spatial filter provided at a focal point of the first lens, and a beam diameter of light passing through the aperture. The optical image measurement device according to claim 2, further comprising a second lens. 5. The optical image measurement device according to claim 1, wherein said photoelectric conversion means includes a plurality of photoelectric conversion elements arranged one-dimensionally or two-dimensionally. 6. The photoelectric conversion device according to claim 1, wherein the photoelectric conversion device includes at least one photoelectric conversion device and a driving device for moving the photoelectric conversion device in a one-dimensional or two-dimensional space. 3. The optical image measurement device according to 3. 7. A scatterer for emitting light expanded to a first beam diameter.
Irradiating means for irradiating the measurement object including: light transmitted through the measurement object or light reflected from the measurement object
Means for spatially filteringThe frequency of the light expanded similarly to the first beam is shifted.
To generate a reference beam Frequency shifting means;  To the spatially filtered lightThe frequency shift hand
Generated by the stageCombining means for combining reference light, one end two-dimensionalOr one-dimensionalAt one end,
A plurality of optical fibers into which the formed light is incident; and
The led lightAn intermediate frequency component corresponding to the frequency shift
MinuteTwo-dimensional conversion to electrical signalsOr one-dimensionalMultiple photoelectric
An optical image measurement device, comprising: a conversion element.
Place. 8. The light synthesized by the synthesizing means,
Expanding to a second beam diameter larger than the first beam diameter,
The optical image measurement device according to claim 7 , further comprising a telescope for guiding the optical fiber .