JP2009008393A - Optical image measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical image measuring device capable of observing a tomogram of an observation target object with high resolution and contrast, and applicable also to measurement. <P>SOLUTION: Scanning is performed with a light beam from a light source 1 corresponding to a pinhole array of an axially-rotating Nipkow disk 7, and the light beam is divided into searching light toward the target object 18 and reference light toward a reference optical path by a beam splitter 12. The searching light from the target object and the reference light through the reference optical path are synthesized by the beam splitter, to thereby generated interference light. The interference light is detected by a two-dimensional imaging means 22, and reflection intensity information inside the target object is acquired from an image signal. In this constitution, since a light beam scanning means by the Nipkow disk and the two-dimensional imaging means are utilized, an interference optical system can be realized simply. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical image measurement device, more specifically, to irradiate a measurement target object with a light beam from a light source, and to detect and perform image processing on reflected light from the target object using an optical interference phenomenon. The present invention relates to an optical image measurement device that acquires tomographic information of a target object.

  2. Description of the Related Art Conventionally, many apparatuses that measure a three-dimensional surface shape of a measurement target object or tomographic information inside a sample using a laser light source or other light sources are known. For example, it is known that a confocal optical microscope can improve resolution in the depth direction as compared with a normal optical microscope, and can observe and measure a fine sample surface shape structure.

  For example, in Patent Document 1 below, as one of confocal optical system technologies, a light beam from a laser light source is illuminated on a sample object via a rotating disk of a pinhole array, and reflected light from the sample is reflected. A basic configuration of an optical microscope is disclosed in which detection is performed again via a rotating disk.

  Patent Document 2 has a configuration in which a light beam from a laser light source is scanned on a sample via a pinhole disk, and interference light generated by reflected light from a measurement sample and reference light from a reference mirror is detected. It is disclosed. This document suggests that by changing the distance between the measurement sample and the objective lens, the three-dimensional shape of the sample surface can be accurately measured from the position where the interference signal has the maximum light amount.

  On the other hand, in recent years, optical coherence tomography (OCT) using an interference phenomenon of a low-coherence light beam (partial coherent light) has attracted attention. According to OCT, it is possible to observe and measure a predetermined tomographic image of an object to be measured in a non-contact non-invasive manner, and it has begun to be applied as an inspection apparatus in medicine, biology, or the industrial field.

  For example, in Patent Document 3, as an initial OCT, a beat that is output by synthesizing a reference light in which the frequency of irradiation light is shifted and a reflected light from a measurement target object is output. A configuration in which a reflection tomographic image of a target object is imaged by detecting a component is shown.

  Patent Document 4 discloses a configuration of an OCT having a light source having a characteristic of a short coherence length, an interferometer using an optical fiber, a phase modulation unit, a lateral scanning mechanism, an ultrasonic light modulation element, a movement control unit for an optical path length, and the like. Is disclosed. This document discloses a basic technique for effectively detecting a tomographic image of a sample specimen including a confocal effect by an optical fiber by detecting interference light guided through the optical fiber. .

  Patent Document 5 discloses an optical tomographic observation apparatus using a light source that generates low-coherence light and an optical fiber interferometer, and has an end structure such as an endoscope or a body cavity mirror through one of the optical paths of the interferometer. A structure that is skillfully combined with is disclosed. In this document, by using an endoscope or the like inserted into a body cavity, a two-dimensional reflected image by a CCD or the like provided as a conventional observation apparatus and an interference signal detection process obtained through an interferometer are used. A technique capable of imaging a tomographic image in the depth direction of an affected tissue is shown.

  Patent Document 6 includes a semiconductor laser light source capable of sweeping an optical frequency, a Michelson interferometer, and a one-dimensional or two-dimensional image sensor, and an image signal output during the optical frequency sweep period. A configuration for calculating a tomographic image by performing Fourier transform processing is disclosed. This method is advantageous in that it eliminates the need for a scanning mechanism that involves mechanical movement in the direction of the optical axis, forms a stable interference optical system, and enables measurement in a short time.

  In Patent Document 7, a light beam is divided into a reference arm and a measurement arm, and the intensity of light that appears by interference between the measurement light via the measurement arm and the reference light via the reference arm is measured using a spectroscope. The structure which detects via is disclosed. The reference arm is provided with a means for changing the phase of light, and shows a configuration for optical tomography of transparent, partially transparent, and opaque objects by analyzing the signal from the spectrometer. Has been.

  In Patent Document 8, a light beam from a light source is divided into a signal light path passing through a subject to be measured and a reference light path passing through a predetermined reflecting mirror, and the interference optical system divides the detection light into two. A system is disclosed in which two CCD sensors for receiving light are provided and the interference light divided in two is periodically blocked and received. The two CCD sensors are configured to receive interference light pulses having different phases and obtain image information of the inner layer of the subject through simple signal processing.

  In Patent Document 9, a light beam from a light source is divided into a signal light path that passes through a subject to be measured and a reference light path that passes through a predetermined reflecting mirror, and the interference optical system divides detection light into three parts. A method of receiving light by providing three CCD sensors for receiving light is disclosed. The three CCD sensors have a configuration in which image information of an inner layer of a subject can be obtained by receiving interference light pulses having different phases and performing simple signal processing.

Patent Document 10 is provided with means for generating a plurality of interference images having different phases in time and means for cutting out the plurality of interference images by high-speed switching in an OCT apparatus using an interferometer. An apparatus for measuring a tomographic image by detecting an interference image with an image sensor such as a CCD and performing a calculation between a plurality of images is disclosed.
JP-T-1-503493 JP-A-6-242380 (Japanese Patent No. 3294246) JP-A-4-174345 (Japanese Patent Publication No. 6-35946) Japanese National Patent Publication No. 6-511112 (Patent No. 3479069) JP 2000-126188 (Patent No. 3318295) JP-A-10-332329 (Patent No. 3332802) JP 11-325849 A Japanese Patent Laid-Open No. 2001-330558 (Patent No. 3594875) Japanese Patent Laying-Open No. 2005-241464 JP 2005-245740 A

  However, since the configuration shown in Patent Document 1 does not use an interferometer, it cannot be directly applied to tomographic observation inside a sample such as OCT. On the other hand, in the configuration shown in Patent Document 2, although an interferometer is included, the low-coherence property of the light source is not used, and background light related to scattering inside the sample is not performed. For this reason, it is impossible to apply to the tomographic observation and measurement inside the sample such as OCT.

  The configurations shown in Patent Documents 3 to 5 disclose a basic OCT method called “time domain method”. In these configurations, since the scanning of the observation target in the depth direction is performed by controlling the movement of the reflection mirror in the optical axis direction with respect to the reference light, the focus state of the irradiation light directed toward the observation target is applied to the entire tomographic image. It cannot be maintained optimally across the board, and it is difficult to achieve high resolution in the in-plane direction perpendicular to the optical axis (depth direction).

  The configuration disclosed in Patent Document 6 discloses an OCT method using a wavelength sweep of a light source called “swept source method”. This method requires a special laser light source that can stably control the frequency of light over a desired range. This type of light source has a limited variety and wavelength, and the light source itself is expensive. is there.

  The configuration disclosed in Patent Document 7 discloses an OCT method using a spectroscopic detector called a “spectral domain method”. Since this method extracts tomographic image information based on numerical calculation processing, there is a merit that mechanical scanning in the depth direction is not necessary, but the measurement range in the depth direction is limited by the characteristics of the spectrometer. There is also a problem that it is difficult to improve the resolving power in the direction orthogonal to the depth direction.

  The configurations disclosed in Patent Documents 8 to 10 disclose a new OCT method using a two-dimensional image sensor as a detector. In this method, when a strong scatterer such as a living body is observed, the image sensor is saturated due to the presence of strong background light superimposed as a DC component on the detector, and the gradation of the signal component having tomographic information is improved. There is a problem that it is difficult. Further, in the configuration shown in Patent Document 8, there is a problem that it is difficult to strictly align the two CCD elements, and in the configuration shown in Patent Document 9, there are three CCD elements. Furthermore, the configuration of Patent Document 10 has a problem that the light source utilization efficiency is poor, and it is expensive to use and requires a special switching light source and other configurations.

  Accordingly, an object of the present invention has been devised to solve the above-described problems, and a tomogram of an observation target object can be obtained with a high resolving power by using a simpler device configuration at a lower price than the conventional method. It is to provide a highly practical optical image measuring device that can be observed with contrast and can be applied to measurement.

The present invention (Claim 1)
Light that obtains tomographic image information of a target object by irradiating a predetermined portion of the measurement target object with a light beam from a light source, and detecting and image-processing reflected light from the target object using an optical interference phenomenon In the image measuring device,
A light source that generates a low coherent light beam;
A pinhole means disposed on a passage surface of the light beam for scanning the light beam from the light source;
A light splitting member for splitting the light beam that has passed through the pinhole means into search light that travels toward a target object and reference light that travels toward a predetermined reference optical path;
Two-dimensional imaging means for detecting interference light synthesized between the search light from the target object guided through the light splitting member and the reference light through the reference light path;
Signal processing means for acquiring reflection intensity information inside the target object from the video signal output from the two-dimensional imaging means;
It is provided with.

The present invention (Claim 3)
Light that obtains tomographic image information of a target object by irradiating a predetermined portion of the measurement target object with a light beam from a light source, and detecting and image-processing reflected light from the target object using an optical interference phenomenon In the image measuring device,
A light source that generates a low coherent light beam;
A pinhole means disposed on a passage surface of the light beam for scanning the light beam from the light source;
A light splitting member for splitting the light beam that has passed through the pinhole means into search light that travels toward a target object and reference light that travels toward a predetermined reference optical path;
Light modulating means for periodically phase-shifting the reference light in the reference light path;
Two-dimensional imaging means for detecting interference light synthesized between the search light from the target object guided through the light splitting member and the reference light through the light modulation means;
Signal processing means for extracting phase information of interference light corresponding to light modulation by the light modulation means from the video signal output from the two-dimensional imaging means to obtain tomographic image information of the target object;
It is provided with.

The present invention (Claim 8)
Light that obtains tomographic image information of a target object by irradiating a predetermined portion of the measurement target object with a light beam from a light source, and detecting and image-processing reflected light from the target object using an optical interference phenomenon In the image measuring device,
A light source that generates a low coherent light beam;
A pinhole means disposed on a passage surface of the light beam for scanning the light beam from the light source;
A light splitting member for splitting the light beam that has passed through the pinhole means into search light that travels toward a target object and reference light that travels along a predetermined reference optical path;
Light modulating means for periodically phase-shifting the reference light in the reference light path;
Optical means for allowing the interference light combined between the search light from the target object guided through the light splitting member and the reference light through the light modulation means to pass again through the pinhole means; ,
Two-dimensional imaging means for detecting interference light that has passed through the pinhole means;
Signal processing means for extracting phase information of interference light corresponding to light modulation by the light modulation means from the video signal output from the two-dimensional imaging means to obtain tomographic image information of the target object;
It is provided with.

  According to the configuration of the present invention, since the light beam scanning means and the two-dimensional imaging means using the Niipou disk are used, the interference optical system can be easily realized, and electrical control and detection signal processing are also easy. is there. In particular, the Nipkow disk-type light beam scanning means can reduce the adjustment effort with a straight and simple optical path configuration without the need to fold the optical system, compared to a system using a galvanometer mirror, etc. Can be manufactured at a low price, so that the price of the entire apparatus can be reduced.

  In addition, according to the configuration of the present invention, it is possible to combine the effects of a confocal optical system and a low coherence interferometer, a tomographic image with high resolving power, low background noise, high gradation and contrast (on the optical axis). It is possible to acquire a vertical cross-sectional image) based on the output image of the image sensor. Taking advantage of this characteristic, three-dimensional image information (3D image) inside the observation target object is obtained by collecting a plurality of cross-sectional images while moving the measurement sample or the reference mirror in the depth direction and performing image processing. It is also possible to obtain.

  In the future, if the two-dimensional image sensor is changed to a higher-definition, higher-sensitivity, and higher-speed one, the version of the apparatus can be easily upgraded. Can be realized.

  In the following, the present invention will be described in detail based on embodiments shown in the drawings.

  In FIG. 1, reference numeral 1 denotes an incandescent light source such as a xenon lamp or a halogen lamp that generates high-intensity infrared light having a wide spectrum, or a semiconductor light source such as a high-intensity light emitting diode (Super Luminescent Diode: SLD). A light source having low coherence (a little coherence) necessary for observing a tomographic image. The light beam from the light source 1 enters the incident end surface 3 a of the optical fiber 3 through the lens 2. The optical fiber 3 is a multimode optical fiber having a core system of about several hundred microns to several millimeters, for example.

  The light beam transmitted through the optical fiber 3 is emitted from the end face 3b of the fiber, and illuminates the surface of the Nipkow disc 7 through the lens 4, the diaphragm 5, the lens 6, and the like. The illumination optical system for the Nipkow disk 7 through these lenses and the stop is designed to be in the Koehler illumination mode, for example, so that the brightness in the illumination area is uniform.

  The Nipkow disk 7 has a total of 10,000 fine pinholes with a predetermined arrangement at intervals of several hundred microns at a predetermined part of a metal disk made of a thin stainless steel plate or the like with a diameter of about several tens of microns to one hundred microns. About 20,000, and constitutes a pinhole means for scanning the light beam. The Nipkow disc 7 is disposed on a plane conjugate with the measurement plane of the measurement target object 18 on the plane through which the light beam from the light source 1 passes, and is connected to the motor 8 via the rotary shaft 8a and rotates at a predetermined speed. . The Nipkow disk (rotating disk) 7 scans the light beam from the light source 1 in accordance with the rotation and the pinhole arrangement. By passing through this nipou disc, the light beam from the light source can improve the spatial coherence.

  The light beam that has passed through the Nipkow disk 7 passes through the lens 9 and the mirror 10 and then enters a beam splitter (BS) 12 that functions as a light splitting member. At the position of the beam splitter 12, the optical path is divided into four directions: an optical path 11a on the light source side, a reference optical path 11b, a search optical path 11c, and a detection optical path 11d.

  The light beam traveling in the reference optical path 11b reaches the plane mirror (reference mirror) 15 perpendicular to the optical path via the ND filter 13 and the lens 14, and is reflected there. The mirror 15 is connected to a piezoelectric element (piezoelectric vibrator) 16, and this vibrator moves the mirror 15 in the optical axis direction (the direction of the arrow 16 a) at a low frequency of, for example, about 60 Hz, so that the periodicity of the light beam is increased. Phase shift is performed. These plane mirrors and the piezoelectric vibrator constitute light modulating means for periodically shifting the phase of the reference light in the reference light path. Further, the optical path 11b of the reference light needs to have the same optical path length as compared to the search optical path 11c, and the distance from the beam splitter 12 to the reference mirror 15 is the distance between the optical path 11b of the reference light and the search optical path 11c. It is appropriately set as necessary so that the optical path lengths are equal.

  On the other hand, the light beam traveling on the search optical path 11 c is imaged on a predetermined part of the measurement target object 18 via the lens 17. The measurement target object 18 is installed on a stage 19, and the stage 19 can be moved in the optical axis direction as indicated by an arrow 19 a by the action of the stepping motor 20. In other words, the stage 19 and the motor 20 are for scanning the measurement sample in the depth direction, and the optical path length of the search optical path becomes variable by the movement of the stage 19 in the optical axis direction, and the three-dimensional measurement object 18 is measured. Tomographic image information can be acquired.

  In the embodiment of FIG. 1, the observation target object 18 has a certain degree of light permeability, such as an extracted biological sample such as a biological tissue, a food or plant sample, a polymer industrial component, or the like. Any observation target is assumed as long as it is shown.

  The reflected light from the measurement target object 18 passes through the beam splitter 12 via the lens 17 and is combined with the reference light returning from the reference optical path 11b, and interference light is generated in the detection optical path 11d. This interference light forms an image on the imaging surface of a two-dimensional imaging element (two-dimensional imaging means such as a CCD camera) 22 through the lens 21 as detection light.

  The video signal from the image sensor 22 is sent to the signal processing circuit 23. The signal processing circuit 23 includes a logarithmic amplification circuit for video signals, a filter circuit, an A / D converter, various other arithmetic processing circuits, and the like, and an output signal processed and generated therein is a computer (Personal Computer: PC) 24.

  The PC 24 can control the overall operation of the optical system and can further process the video signal obtained via the image sensor 22 and the signal processing circuit 23. The signal processing circuit 23 or a circuit including the PC 24 constitutes signal processing means for acquiring reflection intensity information inside the target object or acquiring tomographic image information of the target object.

Via the PC 24, reflection intensity information or tomographic images are transferred to a display device 25 such as a liquid crystal television monitor for display, and if necessary, control can be performed such as transferring to a storage device 26 for storage. it can.
FIG. 2 is an explanatory view showing the structure of a Niipou disk used in the system of FIG. The Nipkow disc 7 is rotatable in a predetermined direction (in the direction of the arrow 8b) at a predetermined speed around the rotation shaft 8a of the motor. For example, a part of the passage area 27 corresponding to the observation range is enlarged and viewed. As shown in the region 28, fine holes (pinholes) 29 having a predetermined size are provided in an aligned manner. The pin holes 29 on the disk are processed to have a diameter of several tens of microns to one hundred microns or less, and a total number of 10,000 to 20,000 or more are opened at intervals of several hundred microns. is there.

  The drilling of these pinholes can be realized at a low cost during mass production using a photoetching technique or the like on a predetermined metal plate. In addition, it is well known in the art that the pinhole arrangement method can minimize illumination unevenness and scanning unevenness by designing and manufacturing, for example, a spiral array 30 having an equal pitch.

  In the optical system as shown in FIG. 1, the light beam from the light source passes through the nipou disk 7 and is scanned on the measurement surface of the measurement target object 18 according to the rotation of the nipou disk and the arrangement of its pinholes. The pinhole effect can improve spatial coherence. That is, in the optical system of FIG. 1, the introduction of the Niipou disc 7 improves the visibility of the interference fringes observed by the image sensor 22 as compared with the case where the disc is not introduced. Thus, it becomes possible to more efficiently detect the interference signal that is the basis of the tomographic image information.

  In general, when a highly diffusive object such as a human biological tissue or biological sample is observed by OCT, the contrast of the detected interference fringes is low due to the influence of the direct current component (DC component) superimposed as background light, The signal component (AC component) of the tomographic image is often orders of magnitude smaller than the DC component. The influence of the DC component can be removed by performing computation between frames on the video signal from the two-dimensional image sensor. That is, with respect to the frame image obtained from the image sensor, for example, if subtraction between adjacent frame images is performed, unnecessary DC components are removed, and tomographic image information inside the target object is extracted as AC components. The

  The above concept will be described below using simple mathematical expressions that are easier to understand. For example, in the two-dimensional image pickup device 22 (see FIG. 1), interference fringe signals detected in continuously output image frames (three frames as an example) can be simply described as follows. .

_{I F-1 = I D +} I A (-sinα)
I _F = I _D + I _A (cos α)
I _{F + 1} = I _D + I _A (sin α)
_{Here, I F-1, I F} , the signal strength of the representative pixel in the frame adjacent each _{I F + 1} is, _{I D} is the DC component, _{I A} is the AC component (signal component of the tomographic image), alpha is the fringe It is a phase. In the above formula, it is assumed that the phase difference of interference fringes between adjacent frames is 90 degrees with each other. Such a condition is obtained by changing the drive waveform of the light modulation unit to the scanning speed of the depth scanning unit. Appropriately setting according to this can be realized locally in the image space.

In an actual measurement system, I _D >> I _A , that is, the direct current component is usually overwhelmingly larger than the signal component to be obtained. Here, for example, the following calculation is performed as an example.

^{_{(I F - I F-1}} ) 2 = I A 2 (1 + 2cosα × sinα)
^{_{(I F + 1 - I F}} ) 2 = I A 2 (1-2cosα × sinα)
Therefore,
^{_{(I F - I F-1}} ) 2 + (I F + 1 -I F) 2 = 2I A 2
In other words, by subtracting between frames, unnecessary DC components can be reliably removed, and if a simple calculation including addition / subtraction and multiplication is performed on three frame images, the accompanying phase term is also eliminated. can do.

  As a result, the necessary AC component (signal component) can be easily extracted by such arithmetic processing. In particular, according to the configuration of the present invention, the interference fringe-derived signal obtained from the image pickup device can be obtained with a higher contrast than the case where there is no nipou disk due to the effect of improving the coherence using the nipou disk. This is advantageous in terms of improving the accuracy of the tomographic information obtained as a calculation result.

  Practically, the calculation including the subtraction between the frames described above is simple and simple by using a digital memory and a subtraction circuit after A / D conversion of the video signal in the signal processing circuit 23 of FIG. It can be executed with high accuracy. After such digital processing, it is also possible to execute more complex operations that take into account noise reduction and image quality improvement by further passing through a signal processing circuit such as a DSP, and the target is extremely accurate. Reflection intensity information inside the object can be extracted.

  FIG. 3 shows a configuration of a system different from the optical system of FIG. 1 as another embodiment of the present invention. In FIG. 3, the same optical elements as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted. Hereinafter, differences from FIG. 1 will be mainly described.

  A light beam from the light source 1 for tomographic image observation is transmitted through the optical fiber 3 and irradiated onto the surface of the Nipkow disk 7 by the lens 4, the diaphragm 5, the lens 6, and the like. The light beam that has passed through the nipou disk is split by the beam splitter 12 into an optical path 11b for reference light and an optical path 11c for search light. The light beam that has traveled along the optical path 11 b of the reference light is guided through the ND filter 13, the lens 14, the mirror 29, and the lens 31, and then reflected by the mirror 15. The mirror 15 is attached to the piezoelectric element 16 and can perform a periodic phase shift of the light beam of the reference light. Further, in the optical path of the reference light, a shutter (not shown) or the like is provided in the vicinity of the mirror 15, and the function of this shutter is used to block the optical path of the reference light as necessary. It can also be used to obtain a reflected image.

  On the other hand, the light beam traveling on the optical path 11 c of the search light enters the measurement target object 18 after passing through the lenses 17 and 32. In FIG. 3, the lenses (17, 32) arranged in the optical path 11c of the search light and the lenses (14, 31) arranged in the optical path 11b of the reference light are designed so that their characteristics match. In addition, since the optical path lengths are equally symmetrically arranged, highly accurate interference measurement can be performed. In the reference optical path 11b, unlike the embodiment of FIG. 1, the piezoelectric element 15 to which the mirror 15 is fixed is connected to the stage 19 and can be moved by the motor 20 in the optical axis direction (the direction of the arrow 19a). ing. By moving the stage 19 in the optical axis direction, the optical path length of the reference optical path becomes variable, and three-dimensional tomographic image information of the measurement target object 18 can be acquired.

  The reflected light from the measurement symmetric object 18 is combined with the reference light via the optical path of the reference light in the beam splitter 12 to generate interference light. The interference light is imaged on a predetermined portion of the Nipkow disk 7 via the lens 33, and the interference light (detection light) that has passed through the pinhole group of the Niipou disk is further passed through the lens 21 to a two-dimensional CCD or the like. An image is formed on the image sensor 22. As described above, the video signal output from the image sensor is subjected to predetermined processing via the signal processing circuit 23 and a predetermined tomographic image is extracted based on calculation processing between frames. The tomographic image obtained including the image processing in the PC 24 can be displayed on the display means 25 such as a liquid crystal television monitor, and can be stored in the storage device 26 as necessary.

  FIG. 4 is an explanatory diagram showing the structure of a Niipou disc used in the system of FIG. The Nipkow disc 7 rotates at a predetermined speed around the rotating shaft 8a of the motor. In FIG. 4, for example, if the light passage region corresponding to the observation region on the light projection side is 27, the detection side ( The light passage region corresponding to the observation region on the light receiving side is located at 34 position. As is apparent from this figure, the arrangement of the pinholes 29 on the Nipkow disk is set symmetrically on the light projecting side and the light receiving side, and is designed so that the symmetry is maintained even when the disk rotates. Yes. The diameter and interval of the pinholes are, for example, about 100 microns and 500 microns, respectively, and such precise and fine hole processing can be realized using a photoetching technique or the like on a predetermined metal plate. As already mentioned.

  In the optical system of FIG. 3 that employs the nipou disk of FIG. 4, the light beam from the light source passes through the nipou disk 7 and the spatial coherence is improved, as in the optical system of FIGS. Is done. As a result, the visibility of the interference fringes observed on the image sensor 22 is improved, so that the interference signal can be detected more clearly, and it is advantageous in that tomographic image information is extracted effectively.

  As is clear from FIG. 4, in the optical system of FIG. 3, a position 27 through which the light beam passes through the lens 6 on the projection side and a position through which the interference light passes through the lens 33 on the detection side. 34 is different on the Nipkow disc 7 and is set very precisely and symmetrically on the disc. In this way, when the detection light passes through a pinhole different from the light projecting side on the Nipkow disc, the detection light is received without being affected by the reflected light (stray light) on the light projecting side disc. This is important in that it can be captured by the two-dimensional image sensor 22 as an element.

  In the system configuration of FIG. 3 and FIG. 4, since the light beam is projected through the pinhole and the detection light is received through the pinhole, the influence of the optical noise is removed by the confocal effect, and the detection signal There is an effect that SN and gradation are also improved. 3 and 4, as a result, it is possible to improve the contrast of the detected interference fringe signal and obtain a tomographic image with high resolving power.

  FIG. 5 is an explanatory diagram when an arbitrary measurement target object is assumed as a measurement target. FIG. 5A shows a coordinate system that can be assumed for the measurement object. As shown in FIG. 5A, in the measurement system of the optical tomography measuring apparatus according to the present invention, an XY image in a direction orthogonal to the optical axis of the optical system and a direction along the optical axis of the optical system. YZ images (or an XZ image not shown) can be considered. 1 or 3 in the present invention, the video signal obtained through the two-dimensional image sensor 22 and the signal processing circuit 23 is an XY image in which a cross section in a direction perpendicular to the optical axis is detected. Is shown. Therefore, if a plurality of these XY images are collected in the Z-axis direction according to the movement of the measurement target object 18 or the reference mirror 15 as shown in FIG. It is possible to acquire three-dimensional information.

  In FIG. 5C, after collecting three-dimensional information inside the object, various image processing by software is performed by the PC 24 (see FIG. 1 or FIG. 3) and processed so that it can be visually displayed. It is an illustration figure displayed on the monitor screen. FIG. 5D is an exemplary diagram in which further image processing is performed on the image data collected in the manner shown in FIG. 5B and a cross-sectional image of the object in the XZ direction is displayed. Such various types of tomographic image measurement are extremely useful in, for example, biological tissue observation and cell examination in the medical and biological fields, or in precision measurement of fine industrial parts in the industrial field.

1 is a configuration diagram of a system showing an embodiment of an optical image measurement device according to the present invention. It is explanatory drawing which showed the structure of the nipou disk used in FIG. It is the block diagram of the system which showed the other Example of the optical image measuring device which concerns on this invention. It is explanatory drawing which showed the structure of the nipou disk used in FIG. It is explanatory drawing at the time of assuming the three-dimensional tomographic measurement of a measurement object.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 3 Optical fiber 7 Nipou disk 12 Beam splitter 15 Reference mirror 18 Measurement object 22 Two-dimensional image sensor 25 Display apparatus 29 Pinhole

Claims (10)

Light that obtains tomographic image information of a target object by irradiating a predetermined portion of the measurement target object with a light beam from a light source, and detecting and image-processing reflected light from the target object using an optical interference phenomenon In the image measuring device,
A light source that generates a low coherent light beam;
A pinhole means disposed on a passage surface of the light beam for scanning the light beam from the light source;
A light splitting member for splitting the light beam that has passed through the pinhole means into search light that travels toward a target object and reference light that travels toward a predetermined reference optical path;
Two-dimensional imaging means for detecting interference light synthesized between the search light from the target object guided through the light splitting member and the reference light through the reference light path;
Signal processing means for obtaining reflection intensity information inside the target object from the video signal output from the two-dimensional imaging means;
An optical image measurement device comprising:   2. The reflection intensity information inside the target object is obtained by performing predetermined arithmetic processing between a plurality of frame images of the video signal output from the two-dimensional imaging means and removing a direct current component. The optical image measuring device described in 1. Light that obtains tomographic image information of a target object by irradiating a predetermined portion of the measurement target object with a light beam from a light source, and detecting and image-processing reflected light from the target object using an optical interference phenomenon In the image measuring device,
A light source that generates a low coherent light beam;
A pinhole means disposed on a passage surface of the light beam for scanning the light beam from the light source;
A light splitting member for splitting the light beam that has passed through the pinhole means into search light that travels toward a target object and reference light that travels toward a predetermined reference optical path;
Light modulating means for periodically phase-shifting the reference light in the reference light path;
Two-dimensional imaging means for detecting interference light synthesized between the search light from the target object guided through the light splitting member and the reference light through the light modulation means;
Signal processing means for extracting phase information of interference light corresponding to light modulation by the light modulation means from the video signal output from the two-dimensional imaging means to obtain tomographic image information of the target object;
An optical image measurement device comprising:   A predetermined calculation process is performed between a plurality of frame images of the video signal output from the two-dimensional imaging means to remove a DC component, and phase information of interference light corresponding to light modulation by the light modulation means is processed. The tomographic image information of a target object is acquired, The optical image measuring device of Claim 3 characterized by the above-mentioned.   The optical image measurement according to any one of claims 1 to 4, wherein the pinhole means is constituted by a Niipou disk in which a plurality of pinholes rotating around a predetermined axis are arranged in a predetermined arrangement. apparatus.   The optical path length of either one of the optical path of the search light or the reference optical path is variably controlled, and three-dimensional tomographic image information of the measurement target object can be acquired in accordance with the variability control. Item 6. The optical image measurement device according to any one of Items 1 to 5.   7. The optical image measurement device according to claim 3, wherein the phase shift of the reference light by the light modulation unit is periodically performed according to a frame rate of the two-dimensional imaging unit. . Light that obtains tomographic image information of a target object by irradiating a predetermined portion of the measurement target object with a light beam from a light source, and detecting and image-processing reflected light from the target object using an optical interference phenomenon In the image measuring device,
A light source that generates a low coherent light beam;
A pinhole means disposed on a passage surface of the light beam for scanning the light beam from the light source;
A light splitting member for splitting the light beam that has passed through the pinhole means into search light that travels toward a target object and reference light that travels along a predetermined reference optical path;
Light modulating means for periodically phase-shifting the reference light in the reference light path;
Optical means for allowing the interference light combined between the search light from the target object guided through the light splitting member and the reference light through the light modulation means to pass again through the pinhole means; ,
Two-dimensional imaging means for detecting interference light that has passed through the pinhole means;
Signal processing means for extracting phase information of interference light corresponding to light modulation by the light modulation means from the video signal output from the two-dimensional imaging means to obtain tomographic image information of the target object;
An optical image measurement device comprising:   A predetermined calculation process is performed between a plurality of frame images of the video signal output from the two-dimensional imaging means to remove a DC component, and phase information of interference light corresponding to light modulation by the light modulation means is processed. The tomographic image information of a target object is acquired, The optical image measuring device of Claim 8 characterized by the above-mentioned.   The pinhole means is constituted by a nippo disk in which a plurality of pinholes rotating around a predetermined axis are arranged in a predetermined arrangement, and the light projecting beam from the light source and the light receiving beam to the imaging means are rotated on the disk. 10. The optical image measuring device according to claim 8, wherein the optical image measuring device passes through a region that is geometrically symmetrical about the axis.

Images