JP5587756B2 - Optical distance measuring device, distance measuring method of optical distance measuring device, and distance measuring program - Google Patents

Description

  The present invention relates to an optical distance measuring device that measures the distance to a subject based on image data obtained by imaging the subject with an image sensor.

  As a distance measuring method of such an optical distance measuring device, a stereo image method described in Patent Document 1, a spatial encoding method described in Patent Document 2, a light propagation time measuring method described in Patent Document 3, and the like are known. It has been. In the stereo image method, a distance to a subject is measured based on the principle of triangulation from a plurality of image data obtained by imaging the subject with two or more imaging devices arranged at predetermined intervals. In the spatial code method, a monochrome projection pattern is projected onto a subject a plurality of times while changing the pattern, and the distance to the subject is measured based on a code formed by blinking on the subject. In the light propagation time measurement method, pulsed light is irradiated, and the distance to the subject is measured based on the time until the irradiated light is reflected by the object and received by the image sensor.

JP 2007-114168 A JP 2007-315864 A Japanese Patent Laid-Open No. 2002-22425

  Here, when measuring the distance to the subject using the stereo image method, it is necessary to mount a plurality of imaging devices. When measuring the distance to the subject using the spatial coding method, it is necessary to mount a pattern projection device that projects while changing the projection pattern. When measuring the distance to the subject using the light propagation time measurement method, it is necessary to measure an extremely short time when the distance to the subject is short. For example, two photoelectric conversion elements are provided for one pixel. It is necessary to mount a special image sensor that can measure the time based on the difference in the amount of light detected from these photoelectric conversion elements. Therefore, when measuring the distance to the subject using each of these methods, there is a problem that it is difficult to reduce the manufacturing cost of the optical distance measuring device.

  In view of this point, an object of the present invention is to provide an optical distance measuring device that can be manufactured at low cost. Another object of the present invention is to propose a distance measuring method and a distance measuring program used in such an optical distance measuring device.

In order to solve the above problems, the optical distance measuring device of the present invention is
A light source, and a pattern projection device that includes an element that transmits or reflects a part of the light beam from the light source to project a predetermined projection pattern onto the subject, and projects the projection pattern intermittently onto the subject;
An image sensor that captures the subject when the predetermined projection pattern is projected to acquire first image data, and captures the subject when the predetermined projection pattern is not projected; An imaging device for acquiring two image data;
A difference image data extraction unit that acquires third image data including only reflected light of the predetermined projection pattern from a difference between the first image data and the second image data;
An autocorrelation coefficient acquisition unit that calculates an autocorrelation coefficient between pixels of the third image data for a predetermined pixel;
And a distance acquisition unit that acquires a distance to the subject based on an autocorrelation coefficient of the predetermined pixel.

  The inventors of the present invention provide an autocorrelation coefficient between pixels obtained for each pixel of the third image data obtained by photographing reflected light of a predetermined projection pattern projected on the subject, and a distance to the subject corresponding to each pixel. And the distance to the subject can be acquired based on the autocorrelation coefficient of the pixels. According to the present invention, since the distance can be measured based on the first image data and the second image data obtained by imaging the subject from one viewpoint, only one imaging device is required. In addition, in order to acquire the first image data and the second image data, it is only necessary to form a state in which the projection pattern is projected onto the subject and a state in which the pattern is not projected onto the subject. Basically, the projection pattern itself is changed. There is no need to let them. Therefore, the pattern projection apparatus can be simplified. Furthermore, it is not necessary to use a special image sensor for imaging, and a general-purpose image sensor can be used. Therefore, the manufacturing cost of the optical distance measuring device can be suppressed. The elements that transmit or reflect a part of the light from the light source in order to project a predetermined projection pattern onto the subject include a photomask, a transmissive liquid crystal panel, a reflective liquid crystal panel, and a digital micromirror device. There is a spatial modulation element. Moreover, the pattern projection apparatus may not only project the projection pattern fixed by these elements, but may change the projection pattern as necessary. Further, although the autocorrelation coefficient may be calculated for all pixels as the predetermined pixel, the distance of only the representative point may be calculated depending on the size of the object to be measured. An autocorrelation coefficient may be calculated.

  In the present invention, in order to obtain the distance to the subject based on the autocorrelation coefficient of the pixel, the autocorrelation coefficient of the pixel of the third image data is associated with the distance to the subject. It is preferable that the distance acquisition unit has a table stored and held, and acquires the distance to the subject by referring to the table based on the autocorrelation coefficient of the pixel.

  In the present invention, there is provided an optical element that guides the projection light from the light source to the subject and guides the reflected light from the subject to the image sensor, and the optical path of the projection light from the optical element to the subject The optical path of the reflected light from the subject to the optical element is common, and it is desirable that the projection illumination field angle by the pattern projection device and the imaging field angle by the imaging device are the same. In this way, a part of the optical path of the projection light from the pattern projection device to the subject and a part of the optical path of the reflected light from the subject to the imaging device are a common optical path, so the device is downsized. Easy to do. In addition, since the projection illumination angle of view and the imaging angle of view are the same, it is possible to suppress the occurrence of a shadow on the subject when the first image data is acquired. Therefore, it is possible to accurately extract the third image data including only the reflected light of the predetermined projection pattern.

  In the present invention, the image sensor is an interlace scanning method, and the pattern projection device projects the predetermined projection pattern in synchronization with either the odd field or the even field of the image sensor, and the imaging It is preferable that the apparatus acquires the first image data in one of the odd field and the even field and acquires the second image data in either one. In this way, it is possible to obtain the first image data and the second image data almost in real time using a CCD image sensor or the like.

  In the present invention, the image sensor is assumed to be a two-dimensional image sensor, but may be a one-dimensional image sensor as long as the shape and movement of the object to be measured are limited to a specified direction. If a one-dimensional image sensor is used, the manufacturing cost of the apparatus can be further suppressed, and high-speed scanning is also possible.

  In the present invention, the light source preferably emits near infrared rays. That is, if the pattern projection device projects a predetermined projection pattern onto the subject using infrared rays in the wavelength range of 0.7 μm to 1.1 μm, the pattern projection device is located in the vicinity of the subject who is the subject or the subject. The distance to the subject can be measured without making humans aware of the projection pattern.

  In the present invention, the pattern projection apparatus preferably includes a photomask moving mechanism that moves the element in the optical axis direction. In this way, since the position of the image formation point of the projection pattern can be changed by moving the element that changes the light amount from the light source two-dimensionally, the sensitivity to the distance at the time of acquiring the first image data is improved. Can be adjusted.

Next, the present invention is a distance measuring method of an optical distance measuring device,
The image sensor captures the first image data in a state where a predetermined projection pattern is projected onto the subject, and the image sensor does not project the predetermined projection pattern onto the subject. An image acquisition step of performing imaging to acquire second image data;
A difference image extraction step of extracting third image data including only reflected light of the predetermined projection pattern from the difference between the first image data and the second image data;
An autocorrelation coefficient calculating step for calculating an autocorrelation coefficient between pixels of the third image data for a predetermined pixel;
It is desirable to include a distance acquisition step of acquiring a distance to the subject based on the autocorrelation coefficient of the pixel.

  According to the present invention, since the distance can be measured based on the first image data and the second image data obtained by imaging the subject from one viewpoint, only one imaging device is required. Further, in order to acquire the first image data and the second image data, a state in which a projection pattern is projected onto the subject and a state in which no pattern is projected onto the subject may be formed, and basically the projection pattern itself is changed. There is no need. Therefore, the pattern projection apparatus can be simplified. Furthermore, it is not necessary to use a special image sensor for imaging, and a general-purpose image sensor can be used. Therefore, the manufacturing cost of the optical distance measuring device can be suppressed.

Next, the present invention provides an optical distance measuring device for measuring a distance to a subject by the distance measuring method described above.
A light source, and a pattern projection device that includes an element that transmits or reflects a part of the light beam from the light source to project a predetermined projection pattern onto the subject, and projects the projection pattern intermittently onto the subject;
An image sensor that captures the subject when the predetermined projection pattern is projected to acquire first image data, and captures the subject when the predetermined projection pattern is not projected; An imaging device for acquiring two image data;
A computer that is connected to the imaging device and includes an image memory for storing and holding the first image data and the second image data acquired by the imaging device;
And a distance measurement program that causes the computer to perform the difference image extraction step, the autocorrelation coefficient calculation step, and the distance acquisition step.

  According to the present invention, the first image data and the second image data acquired by the imaging device are subjected to image processing by the computer, and the distance to the subject is acquired. Since it is not necessary to use a dedicated control device for image processing and distance acquisition, the manufacturing cost of the device can be further reduced.

  Next, the present invention can be a distance measurement program for the optical distance measuring device.

  According to the present invention, it is possible to measure the distance to the subject based on the image data acquired by one imaging device. In addition, a pattern projection apparatus that projects a predetermined pattern onto a subject can be configured simply. Furthermore, a general-purpose image sensor can be used for acquiring image data. Therefore, the manufacturing cost of the apparatus can be suppressed.

It is a schematic block diagram of the optical distance measuring device to which this invention is applied. It is an example of the pattern projected with a photomask. It is a timing chart which shows the vertical synchronizing signal of the CCD image sensor of an imaging device, and the control signal for blinking the light source of a pattern projector. It is a schematic diagram of the 3rd image data for demonstrating the calculation method of an autocorrelation coefficient. It is a graph which shows the relationship between the autocorrelation coefficient of a pixel, and the distance to a to-be-photographed object. It is a schematic flowchart which shows the distance measuring method of an optical distance measuring device. It is explanatory drawing of 1st image data, 2nd image data, 3rd image data, and distance image data.

  Embodiments of an optical distance measuring device to which the present invention is applied will be described below with reference to the drawings.

(overall structure)
FIG. 1 is a schematic configuration diagram of an optical distance measuring device to which the present invention is applied. The optical distance measuring device 1 drives and controls the pattern projection device 2 that intermittently projects a predetermined projection pattern onto the subject 100, the imaging device 3, the pattern projection device 2, and the imaging device 3, and the imaging device. 3 includes a control device 4 that calculates the distance D to the subject 100 by calculating the image data acquired by the computer 3. The subject in this example is a column 100a and a wall 100b.

  The pattern projection apparatus 2 includes a light emitting element (LED) that emits near infrared rays having a wavelength of 0.85 μm as the light source 5. In addition, a photomask (element that transmits a part of the light beam from the light source) 6, a prism (optical element) 7, and the like for projecting a predetermined projection pattern on the optical path of the projection light from the light source 5 toward the subject 100, An objective lens 8 is provided.

  FIG. 2 is an example of a pattern projected by the photomask 6. As shown in FIG. 2, the photomask 6 has a random pattern that partially passes the projection light emitted from the light source 5. The photomask 6 can be moved in the optical axis direction by a photomask moving mechanism 9 including a piezo element.

  The imaging device 3 includes an interlace scanning CCD image sensor 10 as an imaging device. Further, a prism 7 and an objective lens 8 are provided on the optical path between the CCD image sensor 10 and the subject 100. The imaging device 3 shares the prism 7 and the objective lens 8 with the pattern projection device 2.

  The prism 7 is formed by bonding two triangular prisms 7 a and 7 b, and the projection light from the light source 5 of the pattern projection device 2 is transmitted to the bonding surface 7 c and guided to the subject 100, and from the subject 100. A thin film having optical characteristics for reflecting the reflected light in a direction different from the optical path of the projection light and guiding it to the CCD image sensor 10 is formed. Thereby, the optical path of the projection light from the prism 7 via the objective lens 8 to the subject 100 and the optical path of the reflected light from the subject 100 to the prism 7 via the objective lens 8 are common. Note that the projection illumination angle of view by the pattern projection device 2 and the imaging angle of view by the imaging device 3 are the same and overlap.

  The control device 4 includes a drive control unit 12 that drives and controls the light source 5 of the pattern projection device 2 via the driver 11 and drives and controls the CCD image sensor 10 of the imaging device 3. Further, the control device 4 includes an image memory 13 that temporarily stores and holds image data acquired by the CCD image sensor 10 by imaging the subject 100. Furthermore, the control device 4 includes a difference image data extraction unit 14, an autocorrelation coefficient acquisition unit 15, a distance acquisition unit 16, and a table storage unit 17.

  FIG. 3 is a timing chart showing a vertical synchronization signal of the CCD image sensor 10 of the imaging device 3 and a control signal for causing the light source 5 of the pattern projection device 2 to blink. As shown in FIG. 3, the drive control unit 12 drives and controls the light source 5 to project a predetermined projection pattern in synchronization with the odd field of the CCD image sensor 10. Further, the drive control unit 12 drives and controls the CCD image sensor 10 to acquire first image data obtained by imaging the subject 100 in a state where the projection pattern is projected in an odd field, and a predetermined projection pattern. The second image data obtained by imaging the subject 100 in a state where no is projected is acquired in the even field. Further, the drive control unit 12 drives and controls the imaging device 3 to transfer the first image data and the second image data from the imaging device 3 to the control device 4.

  The image memory 13 includes a first image memory 13a that stores and holds the first image data in a two-dimensionally developed state, and a second image memory 13b that stores and holds the second image data in a two-dimensionally developed state. The first image data developed in the first image memory 13a and the second image data developed in the second image memory 13b are sequentially updated as the CCD image sensor 10 captures images. The second image data developed in the second memory is sequentially output to the monitor 18 connected to the optical distance measuring device 1.

  The difference image data extraction unit 14 uses the difference between the first image data two-dimensionally developed in the first image memory 13a and the second image data two-dimensionally developed in the second image memory 13b as a predetermined projection pattern. Extracted as third image data including only reflected light. In this example, the first image data and the second image data are converted into monochrome based on the luminance of each pixel, and then the second image data is subtracted from the first image data to extract the third image data.

The autocorrelation coefficient acquisition unit 15 calculates an autocorrelation coefficient between pixels of the third image data for each pixel P. FIG. 4 is a schematic diagram of third image data for explaining a method of calculating an autocorrelation coefficient. The autocorrelation coefficient R (x, y) is defined by the following equation with N × N pixels including the pixel P (x, y) at the coordinates (x, y) of the third image data as one block Q.
R (x, y): autocorrelation coefficient I (x, y) at coordinates (x, y): luminance N: block size <I>: average luminance in the block

N is preferably about 8 pixels, and R (x, y) is obtained by sliding the block Q for each pixel. When the calculation time is limited, or when the definition of the distance image may be low, the block Q may be slid each time the autocorrelation coefficient R (x, y) is calculated for a plurality of pixels. Good. In the above equation, <I> ² is used as a normalization factor for correcting the light quantity due to the reflectance of the object to be measured.

  Here, the inventors of the present invention calculated the autocorrelation coefficient R (x, y) between the pixels obtained for each pixel P (x, y) and the distance to the subject 100 corresponding to each pixel P. It has been found that there is a correlation with D, and the distance D to the subject 100 can be acquired based on the autocorrelation coefficient R (x, y) of each pixel P (x, y). That is, if the pattern projection device 2 constitutes an imaging optical system and the imaging point is set at a certain distance from the projection unit, the size of the image of the light spot by the photomask is inversely proportional to the distance, Light spots projected on adjacent objects overlap each other and the autocorrelation coefficient increases. Here, mathematically, the Fourier transform of the autocorrelation coefficient is uniquely equivalent to a direct Fourier transform of the image. Therefore, a correlation between the Fourier transform of the third image and the distance may be taken.

  FIG. 5 is a graph showing the relationship between the autocorrelation coefficient R (x, y) of the pixel P (x, y) and the distance D to the subject 100 corresponding to the pixel P (x, y). FIG. 5 shows an autocorrelation coefficient R (x when the optical distance measuring device 1 is fixed and the distance from the optical distance measuring device 1 to the cylinder 100a is changed between 2 m and 40 cm in front of the wall 100b. , Y) and the distance D. The correlation distance between pixels when obtaining the autocorrelation coefficient R (x, y) is 4 pixels. As shown in FIG. 5, as the distance D between the optical distance measuring device 1 and the cylinder 100a becomes shorter, each pixel P (x, y) becomes highly correlated with the neighboring pixel P. The value of the autocorrelation coefficient R (x, y) of each pixel P (x, y) is high. It is also recognized that there is a correspondence between the autocorrelation coefficient R (x, y) and the distance D to the subject 100. Therefore, if the autocorrelation coefficient R (x, y) of each pixel P (x, y) of the third image data is calculated, the autocorrelation coefficient R (x, y) of each pixel P (x, y) It becomes possible to grasp the distance D to the subject 100 based on the above.

  Next, when the autocorrelation coefficient R (x, y) of each pixel P (x, y) is calculated, the distance acquisition unit 16 refers to the table stored and held in the table storage unit 17. The distance D to the part of the subject 100 corresponding to each pixel P (x, y) is acquired. Further, the distance acquisition unit 16 generates distance image data by performing a coloring process for attaching a color associated with the acquired distance D to each pixel P (x, y), and the distance image data is monitored 18. Output to.

  Here, the table shows the autocorrelation coefficient R (x, y) calculated for each pixel P (x, y) of the third image data and the optical distance measuring device 1 for each pixel P (x, y). The distance D to the corresponding part of the subject 100 is measured in advance, and is stored and held in a form in which the autocorrelation coefficient R (x, y) and the distance D to the subject 100 are associated with each other. As shown in the graph of the distance to the cylinder in FIG. 5, there is a range where a linear correspondence is recognized between the autocorrelation coefficient R (x, y) and the distance D to the subject 100. The distance acquisition unit 16 can calculate the distance D to the subject 100 based on the autocorrelation coefficient R (x, y) of each pixel P (x, y) without referring to the table. .

(Distance measurement method)
FIG. 6 is a schematic flowchart showing a distance measuring method of the optical distance measuring apparatus 1. 7A to 7D are explanatory diagrams of the first image data, the second image data, the third image data, and the distance image data, respectively. In each of FIGS. 7A to 7D, the subject 100 is the cylinder 100a and the wall 100b shown in FIG. In each of FIGS. 7A to 7D, the image data at the left end is obtained by imaging the first state in which the column 100a is arranged at a position close to the wall 100b. Is obtained by imaging the second state in which the cylinder 100a is separated from the wall 100b and is positioned closer to the optical distance measuring device 1 than the first state. This is obtained by imaging the third state that is further away from the wall 100b and is located closer to the optical distance measuring device 1 than the second state.

  When measuring the distance D to the subject 100, the imaging device 3 starts imaging with the CCD image sensor 10, and the pattern projection device 2 projects a predetermined projection pattern in synchronization with the odd field of the CCD image sensor 10. . Thereby, as shown in FIG. 7A, the CCD image sensor 10 acquires the first image data of the subject 100 in a state where a predetermined projection pattern is projected in an odd field. Further, as shown in FIG. 7B, the second image data of the subject 100 in a state where a predetermined projection pattern is not projected is acquired in the even field (step ST1).

  When the first image data and the second image data are acquired, the difference image data extraction unit 14 subtracts the second image data from the first image data to obtain a predetermined projection pattern as shown in FIG. The third image data including only the reflected light is extracted (step ST2).

  When the third image data is extracted, the autocorrelation coefficient acquisition unit 15 calculates the autocorrelation coefficient R (x, y) between the pixels of the third image data to each pixel P (x, y) of the third image data. y) is calculated (step ST3). In addition, when the autocorrelation coefficient R (x, y) of each pixel P (x, y) is calculated, the distance acquisition unit 16 creates a table based on the calculated autocorrelation coefficient R (x, y). Referring to, distance D to subject 100 is acquired (step ST4). Thereafter, each pixel P (x, y) is colored corresponding to the distance D, and distance image data is generated as shown in FIG. 7D and output to the monitor 18 (step ST5).

(Function and effect)
According to this example, since the distance D to the subject can be measured based on the first image data and the second image data obtained by imaging the subject 100 from one viewpoint, the optical distance measuring device 1 is used for the imaging device 3. It is sufficient to provide one. Further, in order to acquire the first image data and the second image data, it is only necessary to form a state in which a projection pattern is projected onto the subject 100 and a state in which no pattern is projected onto the subject 100, and it is necessary to change the projection pattern itself. There is no. Therefore, the pattern projection device 2 can have a simple configuration. Furthermore, it is not necessary to use a special image sensor for imaging, and a general-purpose CCD image sensor 10 can be used. Therefore, the manufacturing cost of the optical distance measuring device 1 can be suppressed.

  Further, according to this example, the table is stored and held in a form in which the autocorrelation coefficient R (x, y) of each pixel P (x, y) and the distance D to the subject 100 are associated with each other. The distance acquisition unit 16 acquires the distance D to the subject 100 with reference to the table based on the autocorrelation coefficient R (x, y) of each pixel P (x, y). Accordingly, the distance D to the subject 100 can be acquired regardless of the projection pattern projected by the photomask 6.

  Furthermore, in this example, since the distance D is acquired for each pixel P (x, y) of the third image data, the shape of the subject 100 can be grasped.

  Further, according to this example, a part of the optical path of the projection light from the pattern projection device 2 to the subject 100 and the part of the optical path of the reflected light from the subject 100 to the imaging device 3 are a common optical path. Therefore, it becomes easy to reduce the size of the optical distance measuring device 1.

  Furthermore, in this example, since the projection illumination angle of view and the imaging angle of view are the same and overlap, it is possible to suppress the occurrence of a shadow on the subject 100 when acquiring the first image data. Therefore, it is possible to accurately extract the third image data including only the reflected light of the predetermined projection pattern.

  In this example, the pattern projection device 2 projects a predetermined projection pattern in synchronization with the odd field of the CCD image sensor 10, and the imaging device 3 acquires the first image data in the odd field, and in the even field. Second image data is acquired. Therefore, the first image data and the second image data can be acquired almost in real time. Also, the video of the subject 100 can be output from the monitor 18 using the second image data.

  Furthermore, in this example, the pattern projection apparatus 2 includes a photomask moving mechanism 9 that moves the photomask 6 in the optical axis direction. Therefore, by moving the photomask 6 and changing the position of the image formation point of the projection pattern, it is possible to adjust the sensitivity with respect to the distance when the first image data is acquired.

  Further, since the light source 5 of the pattern projection apparatus 2 for projecting a predetermined projection pattern emits near infrared rays, the projection pattern is applied to a person who is the subject 100 or a person located near the subject 100. The distance D to the subject 100 can be measured without being conscious of the projection.

  Here, the control device 4 can be configured using a computer to which the pattern projection device 2 and the imaging device 3 are connected.

  In this case, the first program for driving and controlling the pattern projection device 2 and the imaging device 3 is operated on the computer, and imaging by the image sensor is performed while a predetermined projection pattern is projected onto the subject 100. The first image data is acquired and an image acquisition process is performed in which the second image data is acquired by performing imaging with the image sensor in a state where a predetermined projection pattern is not projected onto the subject 100. Further, the first image data and the second image data acquired by the imaging device 3 are sequentially transferred from the imaging device 3 to the computer, and stored and held in the image memory 13 of the computer.

  Thereafter, the second program for acquiring the distance D to the subject 100 is operated on the computer, and the computer is caused to calculate the difference between the first image data and the second image data acquired by the imaging device 3. A differential image extraction step for extracting third image data including only reflected light of a predetermined projection pattern, and an autocorrelation coefficient R (x, y) between the pixels of the third image data is set for each pixel of the third image data. The distance for obtaining the distance D to the subject 100 based on the autocorrelation coefficient calculation step for calculating P (x, y) and the autocorrelation coefficient R (x, y) of each pixel P (x, y) Let the acquisition process be performed. Note that the first program and the second program may be a single program. Of course, the program may be converted to hardware and replaced with a gate array or the like.

(Other embodiments)
In the above example, the first image data obtained by imaging the subject 100 with the projection pattern projected is acquired in the odd field, and the subject 100 is imaged without the predetermined projection pattern being projected. The obtained second image data is acquired from the even field adjacent to the odd field from which the first image data was acquired. However, the first image data and the second image data are acquired from the discrete fields instead of the adjacent fields. It doesn't matter.

  In the above example, the image pickup apparatus 3 includes the interlaced CCD image sensor 10 as the image pickup device, but acquires the first image data and the second image data using the progressive scan image sensor. May be. A CMOS type image sensor may be used.

  Furthermore, in the above example, the autocorrelation coefficient is calculated for all the pixels, but depending on the size of the object to be measured, the distance of only the representative point may be calculated. An autocorrelation coefficient may be calculated.

  In the above example, the light source 5 emits a light beam having a wavelength of 0.85 μm. However, the wavelength of the light emitted from the light source 5 is not limited to this, and the CCD image sensor 10 or the CMOS type is used. As long as it is a near infrared ray having a wavelength that can be imaged by the image sensor, for example, a light ray having a wavelength of 0.7 to 1.1 μm, it can be appropriately selected. Here, even in a general image sensor distributed as a general-purpose product, the wavelength sensitivity extends to about 1.0 μm. In addition, when acquiring 1st image data using the light ray with a longer wavelength, it is desirable to make the light source intensity | strength of the pattern projector 2 sufficient. In addition, it is desirable to assume use in an environment where a sufficient SN ratio can be obtained. Here, when using near-infrared light, it is needless to say that it is necessary to appropriately change the wavelength selectivity of an infrared cutoff filter that is usually arranged in front of the light receiving surface of the image sensor. There are also image sensors with increased sensitivity to infrared wavelengths and a wider wavelength range, and when using them, longer wavelength light sources can be used. It is an effective means to calculate the difference between the first and second image data described above in order to eliminate the background light of the same wavelength without fail regardless of which wavelength is selected.

  Further, the predetermined projection pattern projected by the photomask 6 may be a regular projection pattern such as a stripe. Further, the projection pattern may be different depending on the subject 100 and the imaging environment. In this case, instead of the photomask 6, a spatial modulation element that transmits or reflects a part of light from a light source such as a transmissive liquid crystal panel, a reflective liquid crystal panel, or a digital micromirror device is used. The projection pattern can be changed.

  In applications where accuracy is not required, it is needless to say that the optical paths of the pattern projection device 2 and the imaging device 3 do not have to be shared, and independent optical systems may be used.

  Furthermore, a one-dimensional CCD image sensor may be employed as the CCD image sensor 10 as long as the shape and movement of the object to be measured are limited to a specified direction. If a one-dimensional CCD image sensor is used, the manufacturing cost of the apparatus can be further suppressed, and high-speed scanning is also possible.

1. Optical distance measuring device 2. Pattern projection device 3. Imaging device 4. Control device 5. Light source 6. Photo mask 7. Prism 8. Objective lens 9. Photo mask moving mechanism 10. CCD image sensor, 11 driver, 12 drive control unit, 13 image memory, 13a first image memory, 13b second image memory, 14 differential image data extraction unit, 15 autocorrelation coefficient acquisition unit , 16 / distance acquisition unit, 17 / table storage unit, 18 / monitor, 100 / subject, 100a / cylinder, 100b / wall, D / distance, P / pixel, Q / pixel area

Claims (10)

A light source, and a pattern projection device that includes an element that transmits or reflects a part of the light beam from the light source to project a predetermined projection pattern onto the subject, and projects the projection pattern intermittently onto the subject;
An image sensor that captures the subject when the predetermined projection pattern is projected to acquire first image data, and captures the subject when the predetermined projection pattern is not projected; An imaging device for acquiring two image data;
A difference image data extraction unit that acquires third image data including only reflected light of the predetermined projection pattern from a difference between the first image data and the second image data;
An autocorrelation coefficient acquisition unit that calculates an autocorrelation coefficient between pixels of the third image data for a predetermined pixel;
An optical distance measuring device comprising: a distance acquisition unit that acquires a distance to the subject based on an autocorrelation coefficient of the predetermined pixel. In claim 1,
A table that stores and holds the autocorrelation coefficients of the pixels of the third image data in association with the distance to the subject;
The distance acquisition unit refers to the table based on the autocorrelation coefficient of the pixel and acquires the distance to the subject. In claim 1 or 2,
An optical element that guides the projection light from the light source to the subject and guides the reflected light from the subject to the image sensor;
The optical path of the projection light from the optical element to the subject and the optical path of the reflected light from the subject to the optical element are common,
An optical distance measuring device characterized in that a projection illumination angle of view by the pattern projection device and an imaging angle of view by the imaging device are the same. In any one of claims 1 to 3,
The image sensor is an interlace scanning method,
The pattern projection device projects the predetermined projection pattern in synchronization with either the odd field or the even field of the image sensor,
The optical imaging apparatus according to claim 1, wherein the imaging device acquires the first image data in one of the odd field and the even field, and acquires the second image data in either one. In any one of claims 1 to 3,
The optical distance measuring device, wherein the image sensor is a one-dimensional image sensor. In any one of claims 1 to 5,
The optical distance measuring device, wherein the light source emits near infrared rays. In any one of claims 1 to 6,
The said pattern projection apparatus is provided with the photomask moving mechanism which moves the said element to an optical axis direction, The optical distance measuring device characterized by the above-mentioned. The image sensor captures the first image data in a state where a predetermined projection pattern is projected onto the subject, and the image sensor does not project the predetermined projection pattern onto the subject. An image acquisition step of performing imaging to acquire second image data;
A difference image extraction step of extracting third image data including only reflected light of the predetermined projection pattern from the difference between the first image data and the second image data;
An autocorrelation coefficient calculating step for calculating an autocorrelation coefficient between pixels of the third image data for a predetermined pixel;
And a distance acquisition step of acquiring a distance to the subject based on the autocorrelation coefficient of the pixel. In the optical distance measuring device which measures the distance to a subject by the distance measuring method according to claim 8,
A light source, and a pattern projection device that includes an element that transmits or reflects a part of the light beam from the light source to project a predetermined projection pattern onto the subject, and projects the projection pattern intermittently onto the subject;
An image sensor that captures the subject when the predetermined projection pattern is projected to acquire first image data, and captures the subject when the predetermined projection pattern is not projected; An imaging device for acquiring two image data;
A computer that is connected to the imaging device and includes an image memory for storing and holding the first image data and the second image data acquired by the imaging device;
An optical distance measurement apparatus comprising: a distance measurement program that causes the computer to perform the difference image extraction step, the autocorrelation coefficient calculation step, and the distance acquisition step.   The program for distance measurement of the optical distance measuring device according to claim 9.