JP5364619B2 - Distance image sensor - Google Patents

Description

  The present invention relates to a distance image sensor.

  Patent Document 1 discloses a charge distribution type distance image sensor. When this distance image sensor is applied to a distance measurement of TOF (Time Of Flight) type, it is known that the distance resolution is improved by increasing the modulation frequency of the light source (modulated light).

JP 2004-294420 A

  However, it has been found that even if the modulation frequency of the light source is increased in order to improve the distance resolution, the distance resolution cannot actually be improved.

  In other words, in acquiring a distance image, it is necessary to increase the modulation frequency of the light source and the frequency of the transfer signal for charge distribution, but the parasitic capacitance and parasitic resistance in the imaging region dull the waveform of the transfer signal. As a result, the charges cannot be accurately distributed. If charges are not distributed according to distance, the distance obtained from these charge ratios will not be accurate.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a distance image capturing apparatus capable of obtaining an accurate and high-resolution distance image.

  In order to solve the above-described problem, a distance image capturing apparatus according to the present invention includes an imaging region that receives reflected light of light emitted from an object, the imaging region includes a plurality of pixels, and each of the pixels includes A plurality of transfer electrodes for distributing charges generated in response to the incidence of light into different semiconductor regions in synchronization with a transfer signal, and up to the object according to a ratio of charges output from within the semiconductor region A distance distribution type imaging device that requires a distance of a sensor, a sensor driving circuit that provides a transfer signal to the transfer electrode of the pixel, an oscillator that generates a reference clock for the transfer signal, and a synchronization with the reference clock A light source driving circuit that drives the light source that generates the emitted light, a region having a predetermined size in the imaging region, and the designated region and the sensor driving circuit are electrically connected A region specifying means for connecting and electrically disconnecting the imaging area other than the specified area and the sensor drive circuit; and when the area specified by the area specifying means is narrowed, the oscillator And a frequency control circuit for setting a high frequency of the reference clock.

  According to this apparatus, since the area designating unit electrically disconnects the imaging area other than the designated area in the imaging area and the sensor drive circuit, the transfer signal applied to the transfer electrode in the designated area Even if the frequency is increased, the parasitic capacitance and parasitic resistance of the disconnected region can be prevented from causing signal delay and waveform deformation, so that the accuracy of charge distribution is improved and the transfer signal and the light source Since both driving signal frequencies are increased, the distance resolution can be improved.

  Note that the pixels in the imaging region are cut as described above, and it is not necessary to cut the elements necessary for obtaining the distance image and the sensor drive circuit. For example, when a dummy pixel for detecting a reference temperature or a black level is provided in the imaging region, it is not necessary to forcibly cut these pixels and the sensor drive circuit.

  The frequency of the transfer signal and the drive signal of the light source may be increased by the frequency control circuit with the frequency of the reference clock output from the oscillator. As long as the oscillator has a variable frequency, for example, a voltage controlled oscillation circuit can be used.

  The apparatus of the present invention selectively selects a distance image of the first area specified by the area specifying means or a distance image of the second area specified by the area specifying means and narrower than the first area. A control device for outputting is provided.

  Since the area designation means obtains a distance image of the first area with a relatively low distance resolution and a distance image of the second area with a high distance resolution, the control device selectively uses the distance image as a display. Can be output. Since a high-resolution distance image can be viewed as necessary, when this is applied to, for example, an endoscope of medical technology, convenience is improved.

  The apparatus of the present invention also includes a first frame memory that accumulates a distance image of the first area designated by the area designating means, and a second area that is narrower than the first area designated by the area designating means. A second frame memory for storing a distance image; and an image processing apparatus for deleting data of a region corresponding to the second region from the distance image of the first region, and combining the distance image of the second region with the deleted region And.

  Of course, if the relative information of both the first area, which is a large area, and the second area, which is a small area, can be observed simultaneously, the large area can be displayed simultaneously while paying attention to the distance image of the small area. Thus, the state of the point of interest in the entire image can be grasped. The distance image of the first region and the distance image of the second region may be superimposed as they are, but in this case, the original distance image of the first region becomes noise in the region corresponding to the second region. Therefore, the image processing apparatus deletes the data of the area corresponding to the second area from the distance image of the first area, and synthesizes the distance image of the second area with the deleted area.

  These distance images may be still images, but can be displayed as moving images if the acquisition timings of both images are alternately switched in a short time and combined and displayed.

  Further, the first area is an entire area of the imaging area, and the second area is a partial area smaller than the entire area. In other words, the distance image is usually acquired in the entire area of the imaging region, and when the user particularly wants to observe a specific portion, the distance image of the partial region can be acquired with high resolution.

  According to the distance image capturing apparatus of the present invention, an accurate and high resolution distance image can be obtained.

It is a block diagram of the distance image pick-up device of a 1st embodiment. It is a top view of a distance image sensor. It is a circuit block diagram of a distance image sensor. FIG. 6 is a circuit diagram in the vicinity of a transfer electrode in a single pixel. It is a figure which shows the cross-sectional structure of a single pixel. It is a timing chart of various signals, such as a drive signal and a transfer signal of a light source. It is a flowchart of imaging mode switching control. It is a figure which shows an example of a display screen. It is a block diagram of the range image pick-up device of a 2nd embodiment. It is a figure which shows an example of a display screen.

  Hereinafter, the distance image capturing device according to the embodiment will be described. In addition, the same code | symbol shall be used for the same element and the overlapping description is abbreviate | omitted.

  FIG. 1 is a block diagram of the distance image capturing apparatus of the first embodiment, and FIG. 2 is a plan view of the distance image sensor 1.

  The distance image capturing apparatus includes a distance image sensor 1 and a peripheral circuit that controls the distance image sensor 1. The distance image sensor 1 includes an imaging region IMR that receives the reflected light RLTD of the emitted light LED toward the object OBJ, and the imaging region IMR includes a plurality of pixels P (m, n) as shown in FIG. I have. Note that m and n are natural numbers and indicate the row position and the column position of the two-dimensionally arranged pixels, respectively. As the distance image sensor 1, a one-dimensional array of pixels in the imaging region IMR can also be used.

  Referring to FIG. 2, each pixel P (m, n) in the imaging region IMR is two-dimensionally arranged, and these are formed in the semiconductor substrate 2. A horizontal decoder 21 and a vertical decoder 22 for designating an imaging area are arranged along two different sides of the imaging area, and these correspond to the area designation signal SR input from the control device shown in FIG. Thus, the pixel of the address designated by the region designation signal SR and the sensor drive circuit DRV are electrically connected, and the pixel of the other address and the sensor drive circuit DRV are electrically disconnected.

  In the semiconductor substrate 2, an amplifier circuit AMP that amplifies an output signal from each pixel is formed in addition to a sensor drive circuit DRV that generates a transfer signal to be applied to a transfer electrode in the pixel.

  Referring to FIG. 1, the sensor drive circuit DRV is supplied with a drive signal SD having a predetermined frequency from the oscillator 14. In the sensor drive circuit DRV, the amplitude is adjusted as necessary in synchronization with the drive signal and transferred. A signal VTx is generated and applied to each pixel P (m, n) (see FIG. 3).

  The drive signal SD is a reference clock output from the oscillator 14, and this reference clock is also input to the light source drive circuit 11. The light source drive circuit 11 performs amplitude adjustment and the like in synchronization with the reference clock, generates a light source drive signal, and applies it to the light source 10. The light source 10 emits light in synchronization with the light source drive signal. That is, the transfer signal given from the sensor drive circuit DRV to the transfer electrode of each pixel and the light source drive signal given from the light source drive circuit 11 to the light source 10 are synchronized, and the rise and fall times coincide. .

  The emitted light LED from the light source 10 is applied to the object OBJ, and the reflected light RLTD reflected by the object OBJ is incident on each pixel P (m, n) in the imaging region IMR. More specifically, the light source 10 emits a modulated signal subjected to light intensity modulation of a square wave or a sine wave. A configuration in which the reflected light RLTD to the imaging region IMR is incident from the back surface (the surface where the transfer electrode is not formed) of the substrate is preferable. An imaging lens (not shown) is disposed in front of the light incident surface. In the case of a back-illuminated distance image sensor, the semiconductor substrate 2 is thinned and preferably has a thickness of 50 μm or less. Of course, the present invention can also be applied to the surface incidence type distance image sensor 1 without reducing the thickness of the semiconductor substrate 2.

  The distance image pickup device distributes charges generated in response to the incidence of light into different semiconductor regions fd1 and fd2 (see FIG. 5) in synchronization with the transfer signal VTx (see FIG. 5). ), And is a charge distribution type distance image pickup device in which the distance L from the distance image sensor 1 to the object OBJ is obtained in accordance with the ratio of charges output from the semiconductor regions fd1 and fd2.

  Further, as described above, this apparatus includes the oscillator 14 that generates the reference clock of the transfer signal VTx, and the light source driving circuit 11 that drives the light source 10 that generates the emitted light LED in synchronization with the reference clock. Yes. Here, the reference clock of the oscillator 14 is controlled by the frequency control circuit 13. When a command of a specific frequency is input from the control device 12 to the frequency control circuit 13, the frequency control circuit 13 generates a control signal such that the reference clock of the input frequency is generated by the oscillator 14. Is input to the oscillator 14.

  If the frequency of the oscillator 14 is variable, for example, a voltage controlled oscillation circuit (VCO) can be used. In this case, a voltage giving a specified frequency is input from the frequency control circuit 13 to the oscillator 14. The configuration of the oscillator 14 may be a PLL frequency synthesizer using a blog programmable frequency divider. In this case, a frequency dividing ratio that gives a specified frequency may be input from the frequency control circuit 13 to the PLL frequency synthesizer.

  The output from each pixel in the imaging region IMR is amplified by the amplifier circuit AMP and input to the control device as the output signal SO. In the present invention, since the charge generated according to the reflected light delayed from the drive signal of the light source 10 is distributed in synchronization with the drive signal, the ratio of the distributed charge is the distance L to the light object OBJ. It is proportional to 2 times (round trip time). Since the output signal SO includes distance information from each pixel, the control device 12 can obtain a distance image in the imaging region IMR, and this distance image is displayed on the display DSP.

  Unlike a normal luminance image, a distance image can express a sense of distance by, for example, lowering the luminance or changing the color as it is farther away. Of course, it is preferable to capture the data of each pixel of the distance image in the three-dimensional coordinate space and display it as a three-dimensional image on the display DSP. In addition, when displaying a three-dimensional image, it is also possible to apply a stereoscopic television technique using polarized glasses.

  As described above, the control device 12 generates the region specifying signal SR that specifies the region to be imaged, and this is generated according to the region specifying information input to the input device 15 by the user. The input device 15 is an interface such as a mouse, a pointer, or a keyboard. For example, in a medical field, the user wants to increase the resolution of a distance image at a specific location while observing the distance image with a display DSP. Specify the location. When the input device 15 is a pointer, when the user clicks on a specific part displayed in the image, a given range is designated as an area from the clicked point, and the resolution of the distance image in this area is improved. Let

  FIG. 3 is a circuit configuration diagram of the distance image sensor.

  When the area designation signal SR is input to the horizontal decoder 21 and the coder 22 in the vertical direction, the switches SW1 and SW2 of the pixels at the designated address are turned on, and the switches SW1 and SW2 of the other pixels are turned off. The pixel P (m, n) includes a transfer electrode group TX. Each transfer electrode group TX and the horizontal line H1 are connected via a switch SW1, and each of the plurality of horizontal lines H1 is a switch. It is connected to the signal line from the sensor drive circuit DRV via SW2. From the horizontal decoder 21, there are a plurality of vertical lines V1 for supplying a control voltage for controlling the switch SW1.

  Therefore, if the horizontal decoder 21 controls the voltage of the vertical line V1, the switch SW1 can be turned on to designate the pixel in the column where this line exists, and the vertical decoder 22 can switch the switch SW2 of the horizontal line H1. Is turned on and connected to the sensor drive circuit DRV, the transfer signal VTx can be supplied to the pixel by designating the pixel in this row.

  Conversely, if the horizontal decoder 21 controls the voltage of the vertical line V1, turns off the switch SW1, and cancels the designation of the pixel in the column where this line exists, these pixels are electrically connected from the sensor drive circuit DRV. If the vertical decoder 22 turns off the switch SW2 of the horizontal line H1, the pixels in the corresponding row are electrically disconnected from the sensor drive circuit DRV, and the transfer signal VTx is It will not be supplied to the pixel. In the figure, the pixels P (2,2), P (2,3), P (3,2), and P (3,3) in the central area are designated and connected to them. It is shown that the switches SW1 and SW2 are ON and the remaining pixels are not specified.

  As described above, the area designating unit (the horizontal decoder 21, the vertical decoder 22, and the control device 12) of the present invention designates an area having a predetermined size in the imaging area IMR, and the designated area and the sensor drive circuit DRV. Are electrically connected, and the imaging region other than the designated region and the sensor drive circuit DRV are electrically disconnected. Here, when the area designated by this area designating means becomes narrow, the frequency control circuit 13 shown in FIG. 1 sets the frequency of the reference clock of the oscillator 14 high. That is, the narrower the designated area, the higher the frequency of the transfer signal VTx.

  According to this apparatus, since the area designating unit electrically disconnects the imaging area other than the designated area in the imaging area IMR and the sensor drive circuit DRV, it is applied to the transfer electrode group TX in the designated area. Even if the frequency of the transfer signal VTx is increased, the parasitic capacitance and parasitic resistance in the disconnected region can be prevented from causing signal delay and waveform deformation, so that the accuracy of charge distribution is improved. In addition, since both the transfer signal VTx and the drive signal frequency of the light source 10 are increased, the distance resolution in a narrow region can be improved. The frequency of the transfer signal VTx and the drive signal of the light source 10 may be increased by the frequency control circuit 13 with the frequency of the reference clock output from the oscillator 14 (see FIG. 1).

  Note that the pixels in the imaging region are cut as described above, and it is not necessary to cut the elements necessary for obtaining the distance image and the sensor drive circuit. For example, when a dummy pixel for detecting a reference temperature or a black level is provided in the imaging region, it is not necessary to forcibly cut these pixels and the sensor drive circuit.

  FIG. 4 is a circuit diagram in the vicinity of the transfer electrode in a single pixel.

  Each pixel includes transfer electrodes TX1 and TX2 for distributing charges generated in the photodiode PD formed in the semiconductor substrate. The transfer electrodes TX1 and TX2 are gate electrodes of MOS field effect transistors. However, the transfer signal input via the switch SW1 is applied to the transfer electrode TX1 as it is, and separately from this, the switch SW1 ′ (FIG. 1). The transfer signal whose phase is inverted by 180 ° is applied to the transfer electrode TX2 through (not shown). That is, the transfer signal applied to the transfer electrode TX1 and the transfer electrode TX2 is a signal having an opposite phase. When a high level signal is input to each transfer electrode TX1, TX2, the transistor is turned on, and the charge generated in the photodiode PD flows and accumulates in another semiconductor region adjacent to each.

  FIG. 5 is a diagram showing a cross-sectional configuration of a single pixel.

  Each pixel P (m, n) of the distance image sensor 1 is formed in a surface region of a high-concentration P-type (second conductivity type) semiconductor substrate 2 at a lower concentration than the semiconductor substrate (second conductivity type). ) And a pair of high-concentration N-type (first conductivity type) semiconductor regions (charge storage regions: floating diffusion regions) fd1 and fd2 formed on the surface side of the semiconductor region 3. . An insulating layer 5 is formed on the surface of the semiconductor substrate, and a photogate electrode PG is formed on the P-type semiconductor region 3 between the storage regions fd1 and fd2 via the insulating layer 5, The light detection region 4 immediately below the photogate electrode. The potential of the light detection region 4 can be controlled by the voltage applied to the photogate electrode PG.

  The signal extraction electrodes Vfd1 and Vfd2 are provided in electrical connection on the storage regions fd1 and fd2, respectively. Further, the transfer electrodes TX1 and TX2 are located between the photogate electrode PG and the signal extraction electrodes Vfd1 and Vfd2. An N-type semiconductor has electrons as carriers in an electrically neutral state, and is positively ionized when carriers are removed. That is, the high-concentration N-type accumulation regions fd1 and fd2 are greatly recessed downward to constitute a potential well.

  A slight positive DC potential is applied to the photogate electrode PG as necessary. In the light detection region 4 as the light receiving region, hole electron pairs are generated in response to the incidence of light. However, when a positive potential is applied to the transfer electrodes TX1 and TX2 functioning as the gate electrodes, TX1 and TX2 The potential of the region immediately below becomes an intermediate value between the potential of the light detection region 4 and the potentials of the storage regions fd1 and fd2, and a potential step from the light detection region 4 to the storage regions fd1 and fd2 is formed. Electrons fall and accumulate in the potential well of fd2.

  This structure employs a structure in which electrodes are provided on the storage regions fd1 and fd2 and a signal is taken out. However, a high-concentration region for signal extraction is separately provided next to the storage regions fd1 and fd2. It is also possible to place another transfer electrode on the region between the regions fd1 and fd2 and provide an electrode on the high concentration region to extract a signal.

  In the following description, for the purpose of clarifying the description, reference numerals TX1 and TX2 are transfer electrodes, and the voltage of a transfer signal applied between these and the ground potential is also shown. Reference numeral PG denotes a photogate electrode and also indicates a DC voltage applied between these and the ground potential. The semiconductor region 3 is connected to the ground potential. The charges extracted from the signal extraction electrodes Vfd1 and Vfd2 are read out by the read circuit RC formed in the semiconductor region 3. The read circuit is not limited to the semiconductor region 3 and may be formed on the semiconductor substrate 2.

  Since various configurations of the readout circuit RC are known, a known readout circuit may be used. Basically, the read circuit RC holds the charges Q1 and Q2 stored in the storage regions fd1 and fd2, and converts them into a voltage for reading. The amount of charge transferred into the right storage region fd1 during the period when the voltage of the transfer signal TX1 is high is Q1, and the amount of charge transferred into the storage region fd2 at the left when the voltage of the transfer signal TX2 is high. Is Q2, there is a delay time between the emitted light and the reflected light by the ratio of the charge amount Q2 to the total charge amount (Q1 + Q2), which corresponds to twice the distance L to the object. Note that the detection accuracy is improved by integrating the charges. It should be noted that a normal luminance image can be obtained by reading out the entire charge amount Q1 + Q2.

  FIG. 6 is a timing chart of various signals such as a light source drive signal and a transfer signal.

  In the figure, an intensity signal LED of light emitted from the light source and an intensity signal RLTD of reflected light are shown. In the figure, for simplification, these waveforms are shown as square waves, but they are actually sine waves. That is, the drive signal to the light source is a square wave, but the intensity signal of the emitted light is not a perfect square wave, but a sine wave from which high-frequency components are removed, and the reflected light waveform is also a sine wave. Because. The delay time of the reflected light with respect to the emitted light corresponds to the distance to the object. That is, the period from the time t2 to the time t3 is the time during which the light travels the reciprocating distance of the distance from the light source to the object. Of course, the drive signal to the light source is a square wave, and the rise and fall times thereof coincide with the rise and fall times of the transfer signal TX1.

  A period from the current reset start time t1 to the next reset start time t7 is defined as one unit detection period (1 Phase). Between times t1 and t2, the storage regions fd1 and fd2 are connected to the reference potential, and the storage regions fd1 and fd2 are reset to the initial state.

  Thereafter, from time t2 to time t7, transfer voltages TX1 and TX2 composed of opposite-phase square waves are accumulated while being applied to the transfer electrodes TX1 and TX2, and then the charges in the accumulation regions fd1 and fd2 are stored in the readout circuit RC. At time t6 to t7 at the end of the transfer, output signal SO is output from read circuit RC. Thereafter, reset is performed again at times t7 to t8, and the next accumulation is started.

  Here, when the entire imaging region is designated, as described above, the waveforms of the transfer signals TX1 and TX2 are deformed due to the parasitic capacitance and the parasitic resistance, and an unintended delay occurs. It will be. In this case, an accurate distance image cannot be obtained. Of course, a range image having a certain accuracy can be produced, but the accuracy is not sufficient. On the other hand, when the partial area of the imaging area is specified, the influence of the parasitic capacitance and parasitic resistance in the non-designated area is suppressed, so that the waveform deformation of the transfer signals TX1 and TX2 is suppressed, and unintended delay is also suppressed. Will be. Therefore, an accurate distance image can be obtained.

  For example, a case where 50 × 50 pixels or 10 × 10 pixels are designated will be supplementarily described.

  Assuming that the drive current from the sensor drive circuit DRV is 1 mA, the voltage amplitude is 3 V, and the load capacity is 10 pF (0.004 pF per pixel) when 50 × 50 pixels are specified, the time required for the rise of the clock is 30 ns. Similarly, in the case of 10 × 10 pixels, since the load capacitance is 0.4 pF (10 × 10 × 0.004 pF), the time required for rising is 1.2 ns. For example, when the frequency f of the modulated transfer signal is set to 100 MHz and driven at a very high speed, if the load capacity is large (the number of pixels is large), the transfer signal becomes extremely dull and the distance accuracy deteriorates. However, when only a necessary area is selected by partially selecting the number of pixels, since the load capacity is small, the transfer signal is close to a square wave (or sine wave) without being dulled, and therefore it is possible to perform charge distribution with high accuracy. Become.

  Thereby, when the frequency is increased, the distance resolution can be increased, and the distance can be measured with higher accuracy. For example, 10 MHz can be employed as the low frequency for designating the entire region, and 100 MHz can be employed as the high frequency for designating the partial region.

  A supplementary explanation will be given for the distance resolution.

The distance L is the light speed c (m / s), the transfer signal period T (s), the charge Q2 and Q1 signal quantities A (V), B (V), and the delay time of the reflected light. When the phase difference is φ, it is given by the following equation.
L = cT / 2 × (| A | / (| A | + | B |)) = cT / 2 × φ
φ = | A | / (| A | + | B |) = 1 / (1+ (| B | / | A |))
Assuming that the distance error due to noise is σL, the read noise is σ _read , the shot noise is σ _shot , and the coefficient k (V / e) is the conversion efficiency, σL is given by the following equation.
σL = cT / 2 × σφ = cT / 2 × C
C = 1 / (1+ (| B | / | A |))-1 / (1 + D1 / D2)
D1 = | A−2 × ((σ _read ² + σ _shot ² ) ^0.5 × k) / 2 ^0.5 |
D2 = | B + 2 × ((σ _read ² + σ _shot ² ) ^0.5 × k) / 2 ^0.5 |
That is, the distance resolution is determined by the sum of squares of the read noise and the shot noise, but when the signal amount is large, the shot noise becomes dominant. Further, the accuracy is improved by increasing the modulation frequency (= shortening the emission pulse width). Here, assuming that k = (16 μV / e), read noise = 0.3 (mV) (rms), and total signal amplitude 1 V (A = 0.5 V, B = 0.5 V), the frequency f = 100 MHz. Thus, it is possible to obtain a resolution of about 1 mm by performing charge distribution. For example, if the distance accuracy is 9.6 mm at a frequency of 10 MHz and the distance measurement range is 15 mm, the distance accuracy is 4.8 mm and the distance measurement range is 7.5 mm at a frequency of 20 MHz, and the distance accuracy is 1. The distance measurement range is 9 mm and the distance measurement range is 3 mm. At a frequency of 100 MHz, the distance accuracy is 1.0 mm and the distance measurement range is 1 mm.

  FIG. 7 is a flowchart of imaging mode switching control.

  When imaging is started, first, the entire area designation selection mode is executed (S1), the entire area of the imaging area is designated, and a transfer signal is given to the transfer electrode in this area. Next, it is determined whether or not the user designates a partial area (S2). When the partial area is designated, the process shifts to the partial area selection mode (S3). Otherwise, the entire area selection mode is continued (S1). Next, it is determined whether or not to cancel the partial area selection mode (S4). If the user does not request cancellation, the partial area selection mode is continued (S3). If the user wants to cancel, then it is determined whether or not to end the imaging (S5), and if the imaging is not ended, the process returns to the all area selection mode (S1). In addition, when the imaging is finished, the imaging is finished.

  Here, in the partial region selection mode, as described above, the pixels in the designated region are made active (connected to the sensor drive circuit), and the other pixels for imaging are made inactive (disconnected from the sensor drive circuit). . The frequency f of the transfer signal and the light source drive signal is determined according to the selected area, and the transfer electrode and the light source are driven by these signals, respectively.

  FIG. 8 is a diagram illustrating an example of a display screen. In this example, an example in which the present apparatus is applied to an endoscopic camera is shown. In this figure, an image showing an esophagus and an inner wall of the intestine is drawn.

  FIG. 8A is a distance image in the case of the all area selection mode, in which the entire area R1 of the imaging area is designated, and an image with a low distance resolution is displayed on the screen of the display. When the user designates a region R2 surrounded by a dotted line in the screen, the mode shifts to the partial region selection mode in FIG. In this case, the reference clock speeds up, the distance resolution of the region R2 is improved, and the site of interest can be observed well. The user can perform appropriate observation by switching the resolution.

  In other words, the control device 12 (see FIG. 1) of this apparatus can detect the distance image of the first area specified by the area specifying means or the second area R2 narrower than the first area R1 specified by the area specifying means. The distance image is selectively output to the display. Since a high-resolution distance image can be viewed as needed, convenience is improved when this is applied to an endoscope or the like of medical technology. In an endoscope or the like, usually, a distance image is acquired in the entire area of the imaging region, and when the user wants to specifically observe a specific portion, the distance image of the partial region can be acquired with high resolution. Of course, this device can also be applied to other fields.

  FIG. 9 is a block diagram of a distance image capturing apparatus according to the second embodiment.

  This apparatus stores the distance image output from the control device 12 in the entire area frame memory M1 or the partial area frame memory M2 via the switch SW, and inputs the stored distance image to the image processing apparatus IP. And the synthesized image is displayed on the display DSP. Other configurations and operations are the same as those of the distance image capturing apparatus of the first embodiment.

  In other words, this apparatus has a distance between the first frame memory M1 that stores the distance image of the first area R1 specified by the area specifying means and the second area R2 that is narrower than the first area R1 specified by the area specifying means. A second frame memory M2 for accumulating images, and the image processing apparatus IP deletes the data of the area corresponding to the second area R2 from the distance image of the first area R1, and the second area in the deleted area The distance image of R2 is synthesized.

  FIG. 10 is a diagram showing an example of the display screen in this case.

  FIG. 10A shows the all area designation mode, and the screen in this case is the same as in FIG. On the other hand, FIG. 10B displays a composite image. That is, in FIG. 10B, the relative information of both the first region R1 that is a large region and the second region R2 that is a small region can be observed simultaneously, that is, while paying attention to the distance image of the small region R2. In addition, since the large area is displayed at the same time, it is possible to grasp the state of the point of interest in the entire image.

  The distance image of the first region R1 and the distance image of the second region R2 may be superimposed as they are, but in this case, in the region corresponding to the second region R2, the original first region R1 Since the distance image becomes noise, the image processing apparatus IP deletes the data of the area corresponding to the second area R2 from the distance image of the first area R1, and synthesizes the distance image of the second area R2 with the deleted area. I am going to do that. These distance images may be still images, but can be displayed as moving images if the acquisition timings of both images are alternately switched in a short time and combined and displayed.

DESCRIPTION OF SYMBOLS 1 ... Distance image sensor, 11 ... Light source drive circuit, 14 ... Oscillator, IMR ... Imaging area, DRV ... Sensor drive circuit, 12 ... Control device (area designation means), 21, 22... Decoder (area specifying means) 21, 22, 13... Frequency control circuit.

Claims (4)

An imaging region that receives reflected light of light emitted from an object is provided, and the imaging region includes a plurality of pixels, and each of the pixels differs in synchronization with a transfer signal with a charge generated according to the incidence of light. A charge distribution-type distance image capturing device that includes a plurality of transfer electrodes that are distributed in a semiconductor region, and that determines a distance to the object in accordance with a ratio of charges output from the semiconductor region,
A sensor driving circuit for applying a transfer signal to the transfer electrode of the pixel;
An oscillator for generating a reference clock for the transfer signal;
A light source driving circuit for driving the light source for generating the emitted light in synchronization with the reference clock;
An area of a predetermined size is designated within the imaging area, the designated area and the sensor driving circuit are electrically connected, and an imaging area other than the designated area and the sensor driving circuit An area specifying means for electrically cutting
When the region specified by the region specifying means is narrowed, a frequency control circuit that sets a high frequency of the reference clock of the oscillator;
A range image capturing apparatus comprising:   A control device that selectively outputs a distance image of the first area specified by the area specifying means or a distance image of a second area specified by the area specifying means and narrower than the first area; The range image capturing apparatus according to claim 1, wherein A first frame memory for storing a distance image of the first area designated by the area designation means;
A second frame memory for storing a distance image of a second area narrower than the first area specified by the area specifying means;
An image processing device that deletes data of a region corresponding to the second region from the distance image of the first region, and combines the distance image of the second region with the deleted region;
The range image capturing device according to claim 1, further comprising: The range image capturing apparatus according to claim 2, wherein the first area is an entire area of the imaging area, and the second area is a partial area smaller than the entire area.

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