JP2010008168A - Imaging apparatus, endoscopic apparatus, tomographic image photographing apparatus and imaging method used in them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To take an image having high resolving power and to reduce a production cost in an imaging apparatus. <P>SOLUTION: The imaging apparatus 1 is constituted so that the light emitted from a light source is deflected on the basis of the control of a control circuit by a twin-axis deflector and an object is two-dimensionally scanned in horizontal directions and vertical directions by first scanning frequency fH and second scanning frequency fV. The respective scanning frequencies are set so that not fH but 2×fH may become a multiple of fV and constituted so that the scanning routes of light may not be overlapped with each other in one reciprocating scanning in the vertical direction. The control circuit reconstitutes an image on the basis of the light detection signal output from a photodetector by the detection of the reflected light from the object. The image data of one imaging frame can be obtained during one reciprocating scanning of light in the vertical direction and the number of effective scanning lines is increased to take an image. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention irradiates an object while scanning a light beam two-dimensionally, and detects the reflected light with a single light receiver (one light receiving element) to electrically reconstruct the image of the object. In particular, the present invention relates to a small endoscope apparatus that performs image diagnosis inside a body using an optical fiber as a transmission path, a tomographic imaging (optical coherence tomography) apparatus that obtains a tomographic image of a tissue using an optical interference effect, and The present invention relates to an imaging method used for them.

  2. Description of the Related Art In recent years, an imaging apparatus is known that irradiates an object while scanning light rays two-dimensionally, detects the reflected light with a single light receiver, and electrically reconstructs the image of the object. ing. In such an imaging apparatus, generally, fH is an integral multiple of fV, where fH is a horizontal scanning frequency with a high scanning frequency and fV is a low scanning frequency. That is, for example, the imaging apparatus captures an image of one frame while performing vertical scanning for ½ cycle.

  Further, in Patent Document 1, as a modification of such an imaging apparatus, for example, it is incorporated in a small-diameter housing, and is configured using an optical fiber and a condensing lens for coupling a light source and reflected light to the outside. A small-sized endoscope is disclosed. The endoscope apparatus described in Patent Document 1 is a wavelength scanning optical coherence tomography system (Optical Coherence Tomography), and is configured to be able to capture two-dimensional images in the horizontal direction and the depth direction.

By the way, for example, when scanning light beams in the vertical direction and the horizontal direction, the number of scanning lines corresponding to the vertical resolution of the image that can be captured matches the ratio of the horizontal scanning frequency to the vertical scanning frequency, so that high resolution is achieved. In order to capture the image, it is necessary to increase the ratio of the scanning frequencies. However, there is a limit to increasing the scanning frequency of one axis due to constraints on the structure of the deflector or the manufacturing cost, and the scanning frequency of the other axis is lowered because it is necessary to secure the necessary frame rate. Sometimes you can't. For this reason, there is a limit to increasing the ratio of scanning frequencies, and an image with a desired resolution may not be captured. Such a problem becomes more prominent when, for example, it is necessary to use a small deflector that narrows the selectable scan frequency selection range. Patent Document 1 does not disclose a solution for such a problem.
JP 2007-24677 A

  The present invention has been made in view of the above problems, and can increase the number of effective scanning lines, display an image with high resolution, and can be manufactured at low cost. It is an object of the present invention to provide an apparatus, a tomographic imaging apparatus, and an imaging method used for them.

  In order to achieve the above object, a first aspect of the present invention is a two-axis deflector that irradiates an object by two-dimensionally scanning a light beam from a light source at a predetermined scanning frequency for each of two axes, and the deflector. A light receiver that detects reflected light that is irradiated and reflected by the object; a control circuit that electrically reconstructs an image showing the object based on a light reception signal of the light receiver and scanning position information of the deflector; The scanning frequency for each of the two axes is fH when the scanning frequency for the axis with the higher scanning frequency is fH and the scanning frequency for the axis with the lower scanning frequency is fV. It is not a multiple of fV, and N × fH is set to be a multiple of fV, where N is a natural number of 2 or more.

  Invention of Claim 2 is an endoscope apparatus which has an imaging device of Claim 1, Comprising: At least the said inside in the housing | casing provided with the condensing lens for condensing the light from a target object A deflector is housed.

  A third aspect of the present invention is a tomographic imaging apparatus having the imaging apparatus according to the first aspect, wherein the light beam from the light source is branched into irradiation light and reference light to the target object, and the target object. An optical interference unit that generates interference light between the reflected light from the reference light and the reference light, wherein the light receiver is configured to detect the interference light instead of the reflected light, and the phase interval of the interference Is configured to further have a resolution in the depth direction.

  According to the invention of claim 4, the light beam from the light source is scanned two-dimensionally at a predetermined scanning frequency for each of the two axes to irradiate the object, and based on the reflected light from the object and the scanning position information of the light beam In the imaging method for electrically reconstructing an image showing an object, the scanning frequency for each of the two axes is fH as the scanning frequency for the axis having the higher scanning frequency, and scanning for the axis having the lower scanning frequency. When the frequency is fV, fH is not a multiple of fV, N is a natural number of 2 or more, and N × fH is set to be a multiple of fV.

  According to the first aspect of the present invention, imaging is performed for one screen (one frame) every time N / 2 reciprocating scanning is performed in the scanning direction with respect to the axis having the lower scanning frequency. The number can be effectively multiplied by N times. Therefore, even when a deflector that does not have a large scanning frequency ratio for each of the two axes is used, it is possible to capture an image with a higher resolution than in the past and to reduce manufacturing costs. In addition, since the image can be picked up by scanning in a manner close to the raster scan in which the light beam is scanned substantially horizontally, it is easy to reconstruct the picked-up image based on the light reception signal and the scanning position information of the deflector. is there.

  According to the second aspect of the present invention, an endoscope apparatus that is particularly required to have a small deflector and that cannot increase the ratio of scanning frequencies picks up a high-resolution image as described above. be able to.

  According to the invention of claim 3, the tomographic imaging apparatus can capture a tomographic image having a high resolution with respect to the axis having the lower scanning frequency of the light beam.

  According to the fourth aspect of the present invention, the number of scanning lines can be effectively increased N times as described above. Therefore, even when a deflector that does not have a large ratio of scanning frequencies for each of the two axes is used. Therefore, it is possible to capture an image with a higher resolution than in the past, and to reduce the manufacturing cost. In addition, since the image can be picked up by scanning in a manner close to the raster scan in which the light beam is scanned substantially horizontally, it is easy to reconstruct the picked-up image based on the light reception signal and the scanning position information of the deflector. is there.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block configuration diagram illustrating an example of an imaging apparatus according to the first embodiment. The imaging apparatus 1 drives the light source 2 by driving the light source 2, the deflector 10 that deflects the incident light beam and reflects it toward the imaging object (hereinafter referred to as an object) 101, the light source 2 using a laser diode, for example. A light source 2a that emits light, a light receiver 3 that detects reflected light reflected by the object 101 and outputs a light reception signal accordingly, an amplifier 3a that amplifies the light reception signal output from the light receiver 3, and a deflection A drive circuit unit 4 that drives the device 10 and a control circuit 5 that controls the drive circuit unit 4 and electrically reconstructs a captured image based on the received light signal. As will be described later, the deflector 10 is a so-called biaxial type configured to be capable of two-dimensionally scanning a light beam emitted from the light source 2. The imaging device 1 is configured to generate matrix image data (image data) indicating a captured image based on a light reception signal under the control of the control circuit 5 and output the image data to, for example, an external personal computer 100 or the like. ing. The imaging device 1 is not limited to the personal computer 100, and is configured to output captured image data to various devices such as a monitor device and a printer.

  The deflector 10 includes a first mirror device 11 and a second mirror device 12 that swing about one axis and linearly reciprocately scan each incident light beam, and are configured to be able to scan the light beam about two axes. ing. In the present embodiment, by combining the uniaxial first mirror device 11 and the second mirror device 12, the biaxial deflector 10 can be easily configured, and the manufacturing cost can be reduced. In addition, the size and shape of the deflector 10, the size of the scanning angle, and the like can be set relatively freely according to the type of light beam used and the required scanning range, so that imaging can be performed according to various applications. The apparatus 1 can be manufactured easily.

  As will be described later, the light receiver 3 is arranged so as to be able to receive the reflected light reflected by the surface of the object 101 as the light beam is scanned by the deflector 10. The light receiver 3 converts the incident light into a light reception signal corresponding to the intensity and outputs the light reception signal. The received light signal is amplified by the amplifier 3 a and then input to the control circuit 5. In this embodiment, the light receiver 3 is not an image sensor having a pixel array, but a light receiving element having, for example, one photodiode can be used. In order to improve the light receiving efficiency of the light receiver 3, a lens or a concave mirror may be disposed on the front surface of the light receiver 3.

  FIG. 2 shows the first mirror device 11. The first mirror device 11 is a MEMS (Micro Electro Mechanical System) element manufactured by processing an SOI (Silicon On Insulator) substrate 110 having an oxide insulating layer 110a as a box layer by a so-called micromachining technique. The first mirror device 11 includes a mirror part 111 that is a metal film and reflects incident light, a movable plate 112 having a rectangular shape provided on the upper surface thereof, and beams on both sides of the movable plate 112. The torsion springs 113 are formed so as to be lined up in a row, and the fixing part 114 is disposed so as to surround the periphery of the movable plate 112 and supports the end of the torsion spring 113. The movable plate 112 is supported by the fixed portion 114 via the torsion spring 113 so as to be swingable while twisting the torsion spring 113. Comb electrodes 115 are formed on the side edge of the movable plate 112 to which the torsion spring 113 is not connected and the portion of the fixed portion 114 that faces the side edge. Yes. When a voltage is periodically applied between the electrode on the movable plate 112 side and the electrode on the fixed portion 114 side of the comb-tooth electrode 115, an electrostatic attractive force is generated between both electrodes, and this electrostatic attractive force is movable. It acts on the side edge of the plate 112 substantially perpendicularly. That is, the first mirror device 11 is driven by electrostatic torque around the torsion spring 113 generated in the movable plate 112 when a drive voltage is applied to the comb-tooth electrode 115, and the movable plate 112 rotates the torsion spring 113 around the rotation shaft. Swing as. The first mirror device 11 is configured to swing the movable plate 112 at a predetermined first scanning frequency as will be described later.

  For example, the second mirror device 12 periodically swings a reflecting mirror (not shown) using a small motor that is not a MEMS element, other small actuators, or the like as a power source. In the present embodiment, the second mirror device 12 has, for example, a transmission mechanism that converts the rotational motion of a small motor into a reciprocating motion and transmits the reciprocating motion to the swing axis of the reflecting mirror. For example, the second mirror device 12 is configured to swing the reflecting mirror at a predetermined frequency (second scanning frequency) while a predetermined drive voltage is continuously applied to the small motor. The second mirror device 12 may be a MEMS element type like the first mirror device 11 described above, and the first mirror device 11 is not a MEMS element like the second mirror device 12. A thing may be used.

  The light beam emitted from the light source 2 enters the mirror unit 111 of the first mirror device 11. The light beam reflected by the mirror unit 111 and scanned by the first mirror device 11 enters the reflection mirror of the second mirror device 12 and is reflected toward the object 101. In the present embodiment, the second mirror device 12 is arranged so as to scan the light beam in a direction orthogonal to the light beam scanning direction by the first mirror device 11. In the present embodiment, the scanning direction by the first mirror device 11 corresponds to the horizontal direction toward the object 101, and the scanning direction by the second mirror device 12 corresponds to the vertical direction toward the object 101. The light beam emitted from the light source 2 is two-dimensionally applied to the object 101 in two directions perpendicular to each other, for example, in the horizontal direction and the vertical direction, with respect to the two axes by the first mirror device 11 and the second mirror device 12. Scanned.

  The drive circuit unit 4 includes a horizontal mirror drive circuit 41 that drives the first mirror device 11 and a vertical mirror drive circuit 42 that drives the second mirror device 12. Based on the first drive signal transmitted from the control circuit 5, the horizontal mirror drive circuit 41 applies a drive voltage for swinging the first mirror device 11 to drive the first mirror device 11. Further, the vertical mirror drive circuit 42 applies a drive voltage for swinging the second mirror device 12 based on the second drive signal transmitted from the control circuit 5 to drive the second mirror device 12. To do. The second mirror device 12 is driven to swing at the second scanning frequency when the drive voltage is applied from the vertical mirror drive circuit 42 as described above.

  In the present embodiment, the control circuit 5 performs control so that the movable plate 112 of the first mirror device 11 swings with a resonance phenomenon. The control circuit 5 has a frequency that is approximately twice the resonance frequency so that the first scanning frequency becomes the resonance frequency of the vibration system constituted by the mirror unit 111 and the movable plate 112 of the first mirror device 11 and the torsion spring 113. The first drive signal is transmitted. Based on this first drive signal, the horizontal mirror drive circuit 41 applies a rectangular-wave drive voltage having a frequency approximately twice the first scanning frequency to the first mirror device 11. Thus, the first mirror device 11 is configured to be driven at the first scanning frequency with a resonance phenomenon and to have a large swing angle. When the swing angle is increased, the light beam can be scanned at a wide angle, so that a large angle of view of an image captured by the imaging device 1 can be ensured. Note that the application mode and the drive frequency of the drive voltage are not limited to those described above. For example, the drive voltage may be applied in a sine waveform or the like.

  As described above, the control circuit 5 transmits the drive signal to the drive circuit unit 4 to drive the deflector 10, and the received light signal input from the light receiver 3 via the amplifier 3 a and the scanning position of the deflector 10. Based on the information, an image showing the captured object 101 is electrically reconstructed. In the present embodiment, the image is configured by arranging a predetermined number of pixels in a matrix in the horizontal direction and the vertical direction corresponding to the scanning direction of the light beam. Such a reconstruction of the matrix image is performed by assigning a light reception signal indicating the brightness of each pixel to each pixel according to the scanning position information, as will be described later. As the scanning position information of the deflector 10, for example, information indicating the scanning position of the light beam that can be calculated by the control circuit 5 in accordance with a drive signal sent to the drive circuit unit 4 to drive the deflector 10 is used. Can do. Thereby, the scanning position information can be calculated without the need for providing a sensor or the like for detecting the scanning position. For example, the scanning position information may be calculated using a sensor or the like that detects the swing angle of the first mirror device 11 or the second mirror device 12 of the other deflector 10.

  Here, in the present embodiment, the first scanning frequency is set higher than the second scanning frequency, and the scanning frequencies for these two axes are set to have a predetermined relationship with each other. Hereinafter, the scanning frequency for the axis having the higher scanning frequency, that is, the first scanning frequency of the first mirror device 11 is fH, and the scanning frequency for the axis having the lower scanning frequency, that is, the second frequency of the second mirror device 12 is used. Let the scanning frequency be fV. In the present embodiment, the first scanning frequency fH is not a multiple of the second scanning frequency fV, and 2 × fH is set to be a multiple of the second scanning frequency fV. The control circuit 5 drives the first mirror device 11 and the second mirror device 12 at the first scanning frequency and the second scanning frequency set as described above, and scans the light beam through a scanning path described later. Let Further, the control circuit 5 responds to the light reception signal input from the light receiver 3 with a predetermined procedure corresponding to the relationship between the first scanning frequency and the second scanning frequency, that is, when 2 × fH is a multiple of fV. The image data is converted into image data indicating a matrix image by a predetermined procedure. Since the image data is output to the personal computer 100 or the like, the personal computer 100 or the like can display or record a captured image indicated by the image data. The imaging device 1 itself may be provided with a liquid crystal display panel, a storage device, and the like, and the imaging device 1 alone may be configured to display a captured image, record video, or the like. Hereinafter, the light beam scanning operation and the image data reconstruction operation performed by the imaging apparatus 1 will be described.

  First, the light beam scanning path will be described. FIGS. 3A to 3F and FIG. 4 show light beam scanning paths (scanning lines). To simplify the explanation, the scanning frequency ratio of horizontal scanning and vertical scanning is set to 3.5, and the light beam is horizontally shifted from the top to the bottom of the scanning range, starting from the upper left end of the scanning range of the substantially rectangular light beam. Assume that vertical scanning is performed while scanning. First, when the light beam is vertically scanned from top to bottom, as shown in FIG. 3A, the light beam is scanned from left to right (first scanning line) and right while the scanning position is displaced downward. From left to right (second scanning line) and from left to right (third scanning line). Thereafter, the scanning position of the light beam reaches the lower end of the scanning range around the center of the left and right in the middle of scanning from right to left. That is, at the time of vertical scanning from top to bottom, 3.5 scan lines are irradiated onto the object 101 and imaged. Next, as shown in FIG. 3 (b), when the light beam is vertically scanned from the bottom to the top, the light beam moves upward from the left and right central portions that become the lower end of the scanning range during the vertical operation from the top to the bottom. The scanning position is displaced from the center to the left while being displaced. At this time, the fourth scanning line is scanned including a portion scanned by half during vertical scanning from top to bottom. Thereafter, the light beam is displaced from left to right (fifth scanning line), from right to left (sixth scanning line), and from left to right (seventh scanning line), and reaches the upper right end of the scanning range. . As a result, even during vertical operation from bottom to top, 3.5 scanning lines are irradiated and imaged. That is, in the present embodiment, as shown in FIG. 3C, a total of seven scanning lines are irradiated on the object 101 without overlapping each other during one vertical reciprocating scan in the vertical direction. become.

  As described above, after the light beam has been scanned up and down once in the vertical direction from the upper left end of the scanning range, the light beam scans from the upper right end of the scanning range to the lower left as shown in FIG. (First scanning line), scanning from left to right (second scanning line) and from right to left (third scanning line). Thereafter, the lower end of the scanning range is reached at the left and right center of the scanning range during scanning from left to right. Thereafter, as shown in FIG. 3E, the light beam is vertically scanned from the bottom to the top, and the scanning position of the light beam is displaced upward from the left and right center portion which became the lower end of the scanning range during the vertical operation from top to bottom. However, scanning is performed from the center to the right (fourth scanning line). The light beam is scanned from right to left (fifth scanning line), from left to right (sixth scanning line), and from right to left (seventh scanning line), and reaches the upper left end of the scanning range. . Thus, during vertical scanning from top to bottom, 3.5 scan lines are irradiated onto the object 101 and imaged. Even during vertical operation from bottom to top, 3.5 scanning lines are irradiated and imaged. As described above, when 2 × fH is set to be a multiple of the second scanning frequency fV, an imaging frame composed of seven scanning lines is obtained during two vertical reciprocations. Two images are taken, and the light beam returns to the original position.

  Next, a procedure for reconstructing a captured image will be described. In the present embodiment, the first scanning frequency and the second scanning frequency are configured by configuring one imaging frame indicating one image with a total of seven scanning lines during one vertical reciprocation of vertical scanning. An image can be captured with the number of scanning lines that is twice the number of scanning lines, which is larger than the number of scanning lines (3.5) determined when the ratio is 3.5. In other words, the imaging apparatus 1 can capture an image corresponding to twice the resolution in the vertical direction as compared with the prior art. In the following description, in the case where 2 × fH is set to be a multiple of the second scanning frequency fV as described above, X × Y (X = 1, 2,..., NHA, Y = 1, 2,..., NVA) is an example of an image reconstruction procedure when capturing an image of matrix image data composed of pixels. The control circuit 5 determines, based on the received light signal, which is serial data, for each predetermined portion of the plurality of pixels of the matrix video data according to the scanning position information of the light beam calculated from the drive signal output to the drive circuit unit 4. Reconstruct the image. Reconstruction of the matrix image data is performed by dividing each row of the matrix image data to be reconstructed into two at the center of the row and complementarily assigning time-series received light signals as follows.

  FIG. 4 shows the scanning order of rays from the first scanning frame to the fourth scanning frame corresponding to two imaging frames in the present embodiment. The first scanning frame and the second scanning frame in FIG. 4 correspond to FIGS. 3A and 3B, respectively. Further, the third scanning frame and the fourth scanning frame in FIG. 4 correspond to FIGS. 3C and 3D, respectively. The control circuit 5 handles the first half portion of the serial data of the received light signal corresponding to one imaging frame as matrix image data of the portion corresponding to the first scanning frame shown in FIG. Further, the latter half of the serial data of the received light signal is treated as matrix image data corresponding to the second scanning frame in FIG. The control circuit 5 combines the image data for the first and second scanning frames to form image data for one imaging frame. The control circuit 5 handles the first half of the serial data of the received light signal corresponding to the next imaging frame as the third scan frame and the second half as the matrix image data corresponding to the fourth scan frame. . The control circuit 5 combines the image data for the third and fourth scanning frames to form image data for the imaging frame.

  First, with respect to the first scanning frame, the received light signal data digitized in time series is sequentially assigned to a part of the matrix image data in synchronization with the light beam vertically crossing the deflector 10 from the top to the bottom of the scanning range. As the matrix image data, the control circuit 5 assigns the rows in the order of j = 1 → NVA, that is, the order from 1 to NVA, and the columns in the following order. That is, the columns are allocated in the order of i = 1 → NHA / 2 when the row is j = 4n + 1 (n = 0, 1, 2,...). As for the columns, if j = 4n + 2 rows, i = NHA / 2 → NHA is assigned. For columns, if j = 4n + 3 rows, i = NHA → NHA / 2 is assigned in this order. As for the columns, if j = 4n + 4 rows, i = NHA / 2 → 1 is assigned. At this time, during one horizontal scanning, the scanning position is changed in the vertical direction by two rows of matrix image data.

  For the second scanning frame, in synchronization with the deflector 10 vertically crossing from the bottom to the top of the scanning range, the control circuit 5 allocates the rows as matrix image data in the order of j = NVA → 1 for the rows. The columns are assigned in the following order. That is, for columns, if j = 4n + 3 rows, i = NHA / 2 → 1 is assigned. In addition, for a column, when j = 4n + 2 rows, i = 1 → NHA / 2 is assigned in this order. Furthermore, for a column, when j = 4n + 1 rows, i = NHA / 2 → NHA is assigned in this order. If j = 4n + 4 rows for the column, i = NHA → NHA / 2 is assigned in this order. At this time, during one horizontal scanning, the scanning position is changed in the vertical direction by two rows of matrix image data.

  Similarly, for the third scanning frame, in synchronization with the deflector 10 vertically crossing the scanning range from top to bottom, the control circuit 5 sets the matrix image data as j = 1 → NVA for the row. Allocates in order, columns are allocated in the following order. That is, for columns, if j = 4n + 1 rows, i = NHA → NHA / 2 is assigned in this order. Further, when the row is j = 4n + 2 with respect to the column, i = NHA / 2 → 1 is assigned in this order. Furthermore, the columns are allocated in the order of i = 1 → NHA / 2 when the row is j = 4n + 3 rows. For j = 4n + 4 rows, i = NHA / 2 → NHA is assigned in this order. At this time, during one horizontal scanning, the scanning position is changed in the vertical direction by two rows of matrix image data.

  In addition, for the fourth scanning frame, the control circuit 5 synchronizes the light beam vertically with the deflector 10 from the bottom to the top of the scanning range. The columns are allocated in the order shown below. That is, for columns, if j = 4n + 3 rows, i = NHA / 2 → NHA is assigned. Also, when the column is j = 4n + 2 rows, i = NHA → NHA / 2 is assigned in this order. Furthermore, for a column, if j = 4n + 1 rows, i = NHA / 2 → 1 is assigned. If j = 4n + 4 rows for the column, i = 1 → NHA / 2. At this time, during one horizontal scanning, the scanning position is changed in the vertical direction by two rows of matrix image data.

  The control circuit 5 synthesizes the matrix image data for the first scanning frame and the second scanning frame created as described above as one imaging frame, and the matrix image for the third scanning frame and the fourth scanning frame. The data is combined as one imaging frame. The control circuit 5 is configured to perform this image reconstruction processing by accumulating, for example, light reception signals for one or two imaging frames in a memory or the like in the control circuit 5. That is, the control circuit 5 reads out the received light signal from the memory or the like according to the predetermined procedure, and captures the imaging frame in accordance with the drive signal transmitted to the drive circuit unit 4 so as to be synchronized with the horizontal scanning and vertical scanning of the deflector 10. Is generated and output as image data. Note that it is not always necessary to have a one-to-one correspondence between the light reception signal during one round-trip of the vertical scanning and the matrix image data for one imaging frame as described above. For example, a non-display portion is provided in a part of the imaging image. If it is desired to provide it, the reconstruction process may be performed after adding blank data corresponding to the display portion to the received light signal.

  As described above, in the present embodiment, since the first scanning frequency fH is not a multiple of the second scanning frequency fV, and 2xfH is set to be a multiple of fV, a general horizontal scanning frequency fH is set. Compared with the method of setting the value as a multiple of the vertical scanning frequency fV, the number of effective scanning lines can be doubled. Therefore, even when the deflector 10 having a high scanning frequency ratio for each of the two axes is used, it is possible to capture an image with a higher resolution than in the past, and the deflector 10 can be configured at low cost. Therefore, manufacturing cost can be reduced. In addition, since the image can be picked up by scanning in a manner close to the raster scan that scans the light beam substantially horizontally, the picked-up image can be easily reconstructed based on the light reception signal and the scanning position information of the deflector. it can.

(Second Embodiment)
FIG. 5 shows a configuration of an endoscope apparatus using an imaging apparatus according to the second embodiment of the present invention. In the description of the second embodiment, the same components as those in the above-described first embodiment are denoted by the same reference numerals, and only the portions different from those in the above-described first embodiment will be described. The endoscope device (imaging device) 21 connects an endoscope device main body 21a, a small endoscope tip portion (hereinafter referred to as a tip portion) 21b, and the endoscope device main body 21a and the tip portion 21b. Cable portion 21c and the like. The endoscope apparatus 21 is configured to capture an image of the object 101 at a position close to the distal end portion 21b, and output the captured image as image data to an external personal computer 100 or the like. As compared with the imaging device 1 of the first embodiment, the endoscope device 21 is a biaxial gimbal type instead of the deflector 10 using the uniaxial first mirror device 11 and the second mirror device 12. It has the deflector 20 comprised using the mirror apparatus. The endoscope apparatus 21 has a drive circuit unit 24 for driving the deflector 20 instead of the drive circuit unit 4.

  The endoscope apparatus main body 21a accommodates a light source 2, a light source power source 2a, a light receiver 3, an amplifier 3a, a control circuit 5, a drive circuit unit 24, and the like. The distal end portion 21 b is covered with a small casing 26 and has a deflector 20 and a condensing lens 27 for condensing the reflected light from the object 101. The deflector 20 is housed inside the housing 26, and the condenser lens 27 is provided on the surface of the housing 26. For example, the cable portion 21 c guides the light beam emitted from the light source 2 to the inside of the housing 26, and guides the reflected light collected by the condenser lens 27 from the inside of the housing 26 to the light receiver 3. It has an optical fiber 29 that emits light. The cable portion 21 c has wiring (not shown) for applying a driving voltage from the driving circuit portion 24 to the deflector 20.

  FIG. 6 shows the deflector 20. Similar to the first mirror device 11, the deflector 20 is a MEMS element manufactured by processing the SOI substrate 110 using a so-called micromachining technique. The deflector 20 includes a mirror part 211 that is a metal film and reflects incident light, and a movable plate 212 having, for example, a rectangular shape with the mirror part 211 provided on the upper surface. On both sides of the movable plate 212, two first torsion springs 213 formed in a row and arranged in a line are provided. A movable frame 214 that surrounds the movable plate 212 and supports the end of the first torsion spring 213 is provided around the movable plate 212. Two second torsion springs 215 formed in a row in a beam shape so as to be substantially orthogonal to the longitudinal direction of the first torsion spring 213 are provided at both end portions of the movable frame 214. Around the movable frame 214, a fixed portion 216 is formed so as to surround the movable frame 214 and supports the end of the second torsion spring 215. The first torsion spring 213 forms a rotation axis of the movable plate 212, and the second torsion spring 215 forms a rotation axis of the movable frame 214. The first torsion spring 213 and the second torsion spring 215 are the front of the movable plate 212, that will be described later, so that the axis formed by each of the rotation centers of the movable plate 212 passes through the center of gravity of the movable plate 212 when viewed from above. Thus, they are formed so as to be substantially orthogonal to each other when viewed from the direction in which the light beam is scanned. The width dimensions of the first torsion spring 213 and the second torsion spring 215 are, for example, about 5 μm and about 30 μm, respectively. Similarly to the first mirror device 11 described above, the deflector 20 also rotates the movable plate 212 using electrostatic force. In order to rotate the movable plate 212, a first comb electrode 217 is formed at a portion where the first torsion spring 213 is not formed between the movable plate 212 and the movable frame 214, and is fixed to the movable frame 214. A second comb electrode 218 is formed at a portion where the second torsion spring 215 between the portion 216 and the portion 216 is not formed. The first comb electrode 217 and the second comb electrode 218 have comb teeth formed so as to mesh with each other in a pair.

  In this deflector 20, by changing the potentials of, for example, the three electrode portions 219 formed on the upper surface of the fixed portion 216, between the pair of comb teeth constituting the first comb electrode 217 and the second comb. The driving voltage can be independently applied between the pair of comb teeth constituting the tooth electrode 218. The first comb electrode 217 and the second comb electrode 218 generate an electrostatic force that acts in a direction attracting each other between the comb teeth when a drive voltage is applied thereto. The movable plate 212 swings relative to the movable frame 214 with the electrostatic force of the first comb electrode 217 as a driving force and the first torsion spring 213 as a rotation axis. In addition, the movable plate 212 swings with respect to the fixed portion 216 using the second torsion spring 215 as a rotation axis using the electrostatic force of the second comb electrode 218 as a driving force including the movable plate 212. As a result, the first torsion spring 213 swings with respect to the fixed portion 216 in a direction substantially perpendicular to the swing direction. That is, the deflector 20 is configured using a biaxial gimbal type mirror device in which the movable plate 212 on which the mirror portion 211 is formed can swing about two axes.

  Based on the drive signal from the control circuit 5, the drive circuit unit 24 periodically applies a drive voltage to the first comb electrode 217 and the second comb electrode 218 of the deflector 20 to drive the deflector 20. . In the second embodiment, the control circuit 5 drives the drive circuit unit 24 to the first comb electrode 217 with a cycle twice the natural frequency of the system of the first torsion spring 213 and the movable plate 212 described above. Apply voltage. Thereby, the movable plate 212 is driven and oscillated with respect to the first torsion spring 213 at the first scanning frequency equal to the natural frequency. Similarly, the control circuit 5 has a period twice as long as the natural frequency of the system of the second torsion spring 215, the movable frame 214, and the movable plate 212 from the drive circuit unit 24 to the second comb electrode 218. The drive voltage is applied. Accordingly, the movable frame 214 and the movable plate 212 are driven and oscillated with respect to the second torsion spring 215 at the second scanning frequency equal to the natural frequency. As described above, in the present embodiment, the deflector 20 is swung with the resonance phenomenon for both of the two axes, so that the scanning angle of the light beam can be increased for both of the two axes. Imaging can be performed. Note that the driving method of the deflector 20 is not limited to this, and only one of the first scanning frequency and the second scanning frequency is set as the natural frequency of the vibration system corresponding to the first scanning frequency or the second scanning frequency. You may make it move. Further, both the two axes may be oscillated at an arbitrary frequency not accompanied by a resonance phenomenon.

  In the second embodiment, by using the deflector 20, the light beam emitted from the light source 2 can be scanned on the object 101 using one mirror element. In the second embodiment, from the difference in spring constant between the first torsion spring 213 and the second torsion spring 215 and the difference in mass between the movable plate 212 and the movable frame 214 including the movable plate 212, the first scanning frequency is obtained. In comparison, the second scanning frequency is considerably reduced. The deflector 20 scans the light beam reflected by the mirror unit 211 toward the object 101 in a substantially horizontal direction by swinging the first torsion spring 213 of the movable plate 212. Further, the deflector 20 scans the light beam reflected by the mirror unit 211 in the substantially vertical direction toward the object 101 by the movable plate 212 swinging about the second torsion spring 215 together with the movable frame 214. Therefore, the endoscope apparatus 21 can pick up an image by two-dimensionally scanning a light beam on the object 101. At this time, for example, as in the first embodiment, when the first scanning frequency is fH and the second scanning frequency is fV, the control circuit 5 is not a multiple of fV, and 2 × fH is fV. The drive circuit unit 24 is controlled so as to be a multiple. The image reconstruction process is also performed in the same manner as in the first embodiment. As a result, the number of effective scanning lines can be increased to capture an image as described above, and an image with a higher resolution can be captured compared to the conventional case, and the manufacturing cost can be reduced. .

  In the second embodiment, the deflector 20 can be reduced in size compared to the case where two uniaxial mirror devices are used in combination as in the first embodiment. Further, since the center position of the mirror unit 211 is hardly displaced at the time of driving, the size of the light beam incident on the mirror unit 211 is changed from 1 mm, which is equivalent to the laser diameter emitted from the light source 2 according to the size of the mirror unit 211. The diameter can be reduced to about 5 mm or less. The deflector 20 can have a smaller volume. Therefore, the distal end portion 21b of the endoscope apparatus 21 can be further downsized.

  In the second embodiment, as described above, each part provided in the endoscope apparatus main body 21a such as the light source 2 and the light receiver 3 may be accommodated in the distal end part 21b, for example. . Further, when the light source 2 and the light receiver 3 are housed in the distal end portion 21b together with the deflector 20, only the wiring for passing an electrical signal can be arranged as the cable portion 21c without using an optical fiber. Furthermore, instead of the deflector 20, a deflector using two uniaxial mirror devices as in the first embodiment described above may be used.

(Third embodiment)
FIG. 7 shows a configuration of a tomographic imaging apparatus using an imaging apparatus according to the third embodiment of the present invention. The tomographic imaging apparatus (imaging apparatus) 31 captures a tomographic image having resolution in the depth direction by causing the light from the light source to interfere with the reflected light and sweeping the phase interval of the interference. The tomographic imaging apparatus 31 is used, for example, as a non-invasive system for diagnosing a subject such as a part of a human body, and is also called an optical coherence tomography (Optical Coherence Tomography) system (hereinafter referred to as OCT). be called. As the OCT, a time domain OCT (TD-OCT) and a frequency domain OCT (FD-OCT) are known, but the tomography apparatus 31 is a time domain OCT.

  As shown in the figure, the tomographic imaging apparatus 31 includes a light source 2, a light source driver 32 a that emits a light beam from the light source 2 based on the control of the control circuit 5, and a light beam from the light source 2 to the reference light and the object 101. An optical interference unit 36 that branches into irradiation light and generates interference light between reflected light from the object 101 and reference light, and a phase scanning unit 37 that scans the phase of the reference light are provided. In addition, the tomographic imaging apparatus 31 includes a deflector 20 that two-dimensionally scans the object 101 with a light beam emitted from the light source 2, a drive circuit unit 24 that drives the deflector 20, and a light receiver 3 that detects interference light. And an amplifier 3 a that amplifies the light reception signal from the light receiver 3 and inputs the amplified signal to the control circuit 5. In the present embodiment, the light source 2 and the light interference unit 36, the light interference unit 36 and the deflector 20, the phase scanning unit 37, and the light receiver 3 are connected to each other using an optical fiber 29 so that light can be guided. Yes. Moreover, as the optical interference part 36, the optical coupler (splitter) is used, for example. The tomographic imaging apparatus 31 does not necessarily need to use an optical fiber, and a half mirror or a beam splitter may be used instead of the optical coupler in order to cause the light to interfere.

  The deflector 20 is, for example, a biaxial gimbal mirror type similar to that described in the second embodiment, but is a combination of uniaxial mirror devices similar to those described in the first embodiment. There may be. The phase scanning unit 37 is realized, for example, by providing a collimator lens or a movable mirror in the optical path and moving the movable mirror in the optical path direction, but may have another configuration that uses a delay of light in the optical path.

  The control circuit 5 transmits a modulation signal to the light source driver 32a, and controls the emission of light from the light source 2. In addition, the control circuit 5 transmits a drive signal to the drive circuit unit 24 in the same manner as in the first embodiment and the like, and drives the deflector 20 at a predetermined scanning frequency for two axes. For example, as in the first embodiment described above, when the first scanning frequency of the deflector 20 is fH and the second scanning frequency is fV, the control circuit 5 is not a multiple of fV, but 2 × fH is fV. The drive circuit unit 24 is controlled to be a multiple of. The control circuit 5 receives the light reception signal output from the light receiver 3 and amplified by the amplifier 3a. Based on the light reception signal and the scanning position information, the control circuit 5 receives the image signal. Perform reconfiguration processing.

  In the third embodiment, the light beam from the light source 2 is guided to the optical interference unit 36 via the optical fiber 29, for example. The reference light from the optical interference unit 36 is guided to the phase scanning unit 37 through the optical fiber 29. In the phase scanning unit 37, the reference light becomes parallel light by the collimator lens, is reflected by the movable mirror, and returns to the optical interference unit 36 through the optical fiber 29. On the other hand, the irradiation light from the light interference unit 36 is reflected by the deflector 20 and is applied to the object 101. The irradiation light is focused on the object 101 by the lenses 38a and 38b, and the object 101 is two-dimensionally scanned by the deflector 20. As the irradiation light, infrared rays are preferable, and near infrared rays are particularly preferable. This is because near-infrared light has a high ability to transmit the object 101 and has a small absorption spectrum of water, and is suitable for measurement of biological components in an aqueous solution such as blood. Irradiation light is absorbed and reflected at various locations inside the object 101, and the reflected light returns to the light interference unit 36 via the deflector 20 and the lenses 38 b and 38 a.

  Here, in the optical interference unit 36, the reflected light and the reference light interfere so as to strengthen each other when the phases match. The interference light from the light interference unit 36 is input to the light receiver 3 through the collimator lens 3c. The tomographic imaging apparatus 31 can obtain a resolution in the depth direction of the object 101 and obtain a tomographic image by sweeping the phase interval of the interference between the reference light and the irradiation light by the phase scanning unit 37. . The light reception signal from the light receiver 3 is processed by the control circuit 5, and the three-dimensional distribution of the biological component of the object 101 is measured. Here, the three dimensions are three dimensions by adding one dimension in the internal direction of the object 101 to two dimensions along the surface of the object 101. The three-dimensional distribution of the biological component is the three-dimensional presence / absence of the biological component to be measured or the three-dimensional concentration distribution of the biological component. As described above, the measurement in the internal direction, that is, the depth direction by OCT is added to the two-dimensional scanning of the irradiation light by the deflector 20, and the three-dimensional measurement of the object 101 is possible.

  In the control circuit 5, for example, image data indicating a tomographic image showing a three-dimensional distribution as a measurement result is generated. The generation of the image data is performed in a predetermined procedure corresponding to the case where 2 × fH is a multiple of fV based on the light reception signal and the scanning position information, as in the first embodiment. The generated image data is output to the display unit 300, and an image is displayed on the display unit 300 based on the image data. The display unit 300 is a display, for example, and may be a printer. Note that the processing performed by the control circuit 5 is not limited to the measurement of the three-dimensional distribution of the biological component, and performs, for example, the formation of a tomographic image of the subject using a light source in a wavelength region that does not absorb light by a specific biological component. It may be configured to be possible.

  In the third embodiment, as described above, the number of scanning lines in the horizontal direction can be effectively increased in the irradiation light that scans the object 101 as in the first embodiment. Accordingly, the axis with the lower scanning frequency is used as compared with the case of using a two-dimensional deflector in which the horizontal scanning frequency fH is a multiple of the vertical scanning frequency fV as in the prior art without increasing the manufacturing cost. Three-dimensional tomographic imaging can be performed by increasing the resolution about a certain vertical axis, that is, in the vertical direction.

  In addition, this invention is not limited to the structure of the said embodiment, A various deformation | transformation is possible suitably in the range which does not change the meaning of invention. For example, in the first to third embodiments, when the first scanning frequency is fH and the second scanning frequency is fV, fH is not a multiple of fV, and N is a natural number of 2 or more, and N × fH Each scanning frequency may be set so that is a multiple of fV. Thereby, the light beam can be scanned effectively with the number of scanning lines N times the ratio between the first scanning frequency and the second scanning frequency, and the resolution of the image to be captured can be increased. At this time, the control circuit 5 may convert the image data indicating the matrix image according to a predetermined procedure corresponding to the value of N based on the light reception signal and the scanning position information. In other words, in the imaging apparatus 1, the endoscope apparatus 21, and the tomographic imaging apparatus 31 of the first to third embodiments, each scanning frequency is set so that N = 2. At this time, the control circuit 5 performs the image reconstruction process as described above so as to correspond to N = 2.

  Hereinafter, as an example of the above, referring to FIGS. 8A to 8F and FIGS. 9A and 9B, for example, in the configuration as in the first embodiment, the scanning frequency is N = 3. An example of the scanning path of the light beam of the imaging apparatus in which is set will be specifically described. For simplicity of explanation, the scanning frequency ratio of horizontal scanning and vertical scanning is set to 10: 3, and the vertical scanning is performed while the light beam is horizontally scanned from the top to the bottom of the scanning range, starting from the upper left end of the scanning range of the light beam. Suppose that First, when the light beam is vertically scanned from top to bottom, as shown in FIG. 8A, the light beam is scanned from left to right (first scanning line) and right while the scanning position is displaced downward. From left to right (second scanning line) and from left to right (third scanning line). Thereafter, the scanning position of the light beam reaches the lower end of the scanning range at a position that is shifted to the left by about 1/3 of the right and left width from the right end while scanning from the right to the left. That is, at the time of vertical scanning from top to bottom, 3 and 1/3 scanning lines are scanned. Next, as shown in FIG. 8B, when the light beam is vertically scanned from bottom to top, the light beam scans upward from the portion that became the lower end of the scanning range during the vertical operation from top to bottom. While the position is displaced, it is displaced toward the left. At this time, the fourth scanning line is scanned, including a portion scanned by 1/3 during vertical scanning from top to bottom. The light beam is scanned from left to right (fifth scanning line) and from right to left (sixth scanning line), and is shifted to the right by about 2/3 from the left end while scanning from left to right. The upper end of the scanning range is reached, and the direction of vertical scanning changes downward. Thereafter, as shown in FIG. 8C, the light beam is scanned to the right end (seventh), and scanned from right to left (eighth), from left to right (9th), and from right to left (tenth). And reach the lower left corner.

  At this time, the control circuit 5 performs image reconstruction processing according to a predetermined procedure corresponding to a value of N = 3 based on the light reception signal and the scanning position information of the light beam. That is, as in the case of N = 2 as shown in the first embodiment, the control circuit 5 alternates the vertical direction of the rows every 1/3 period scanning frames in the vertical direction. In order, the data indicated by the received light signal is assigned as matrix image data. For the columns, the data indicated by the received light signal is assigned in the order corresponding to the scanning direction of the light beam as the image data of the range in which the light beam is scanned in the scanning frame according to the row of the matrix image data. . As described above, the image data can be appropriately reconstructed by assigning the data indicated by the received light signal as the image data in a predetermined procedure corresponding to the value of N = 3. When the image reconstruction process is performed based on the procedure corresponding to the N value, the load of the control circuit 5 due to the process increases as the N value increases. Therefore, the value of N is preferably about 9 or less, for example.

  FIG. 9A is a combination of the scanning line paths shown in FIGS. 8A to 8C at this time. In this way, when N = 3, a total of 10 scanning lines are scanned without overlapping each other while the vertical scanning is reciprocated 1.5 times up and down. By configuring the imaging frame, the resolution of the captured image can be increased. That is, when N = 3, an image can be picked up by the number of scanning lines that is three times the number of normal scanning lines determined when the ratio of the first scanning frequency to the second scanning frequency is 10: 3. Therefore, it is possible to effectively capture an image corresponding to a resolution three times that in the vertical direction as compared with the conventional case. Similarly to this, during the subsequent vertical scan 1.5 reciprocations, a total of 10 scanning lines overlap each other as shown in FIGS. 8D to 8F and FIG. 9B. Scanned without. That is, when N = 3, two imaging frames composed of 10 scanning lines are imaged while the vertical scanning is reciprocated up and down three times, and the light beam returns to the original position.

  As described above, in the description of the present invention, the ratio between the first scanning frequency and the second scanning frequency is assumed to be 3.5 (7: 2), 10: 3, etc. for the sake of simplicity. Actually, the present invention is not limited to this, and various ratios can be set. More preferably, the ratio of the scanning frequencies may be such that the ratio of the first scanning frequency to the second scanning frequency is greater than 10: 1. The number of horizontal scanning lines increases. Thereby, the number of effective scanning lines can be increased from 10 × N, and a higher resolution image can be taken.

1 is a block diagram illustrating an example of an imaging apparatus according to a first embodiment of the present invention. The perspective view which shows the 1st mirror apparatus of the said imaging device. (A) is a figure which shows the scanning path of the light beam of the 1st scanning frame of the said imaging device, (b) is a figure which shows the scanning path of the light beam of the 2nd scanning frame of the imaging device, (c) is (a) and FIG. 4B is a diagram illustrating a combination of (b), (d) is a diagram illustrating a scanning path of a light beam of a third scanning frame of the imaging apparatus, and (e) is a scanning path of a light beam of a fourth scanning frame of the imaging apparatus. The figure shown, (f) is a figure which synthesize | combines and shows (d) and (e). FIG. 4 is a diagram illustrating a procedure for reconstructing images of first to fourth scanning frames of the imaging apparatus. The block diagram which shows an example of the endoscope apparatus which concerns on 2nd Embodiment of this invention. The perspective view which shows the deflector of the said endoscope apparatus. The block diagram which shows an example of the tomography apparatus which concerns on 3rd Embodiment of this invention. (A) thru | or (f) is a figure which shows the modification of the scanning path | route of the light ray of the imaging device which concerns on 1st Embodiment of this invention. 8A is a diagram illustrating the combined scanning paths of the light beams illustrated in FIGS. 8A to 8C, and FIG. 8B is a combined schematic illustrating the scanning paths of the light beams illustrated in FIGS. 8D to 8E. Figure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Light source 5 Control circuit 10, 20 Deflector (mirror device)
DESCRIPTION OF SYMBOLS 11 1st mirror apparatus 12 2nd mirror apparatus 21 Endoscope apparatus (imaging apparatus)
26 Condensing lens 27 Housing 31 Tomographic imaging device (imaging device)
36 Optical interference part

Claims (4)

A two-axis deflector that two-dimensionally scans light beams from the light source with a predetermined scanning frequency for each of the two axes and irradiates the object, and reflected light that is irradiated from the deflector and reflected by the object is detected. In an imaging apparatus comprising: a light receiver; and a control circuit that electrically reconstructs an image showing the object based on a light reception signal of the light receiver and scanning position information of the deflector;
The scanning frequency for each of the two axes is fH, where fH is the scanning frequency for the axis with the higher scanning frequency and fV is the scanning frequency for the axis with the lower scanning frequency, and , N is a natural number of 2 or more, and N × fH is set to be a multiple of fV.   An endoscope apparatus having the imaging apparatus according to claim 1, wherein at least the deflector is housed in a housing provided with a condensing lens for condensing light from an object. An endoscope apparatus characterized by that. A tomography apparatus having the imaging apparatus according to claim 1,
The light source from the light source is further divided into irradiation light and reference light to the object, and further includes an optical interference unit that generates interference light between the reflected light from the object and the reference light,
The light receiver is configured to detect the interference light instead of the reflected light, and further configured to have a resolution in a depth direction by sweeping a phase interval of interference. A tomographic imaging apparatus. A light beam from a light source is scanned two-dimensionally at a predetermined scanning frequency for each of two axes to irradiate the object, and an image indicating the object is electrically generated based on the reflected light from the object and the scanning position information of the light beam. In an imaging method that reconstructs automatically,
The scanning frequency for each of the two axes is fH, where fH is the scanning frequency for the axis with the higher scanning frequency and fV is the scanning frequency for the axis with the lower scanning frequency, and , N is a natural number of 2 or more, and N × fH is set to be a multiple of fV.

Images