JP2013205089A - Information acquisition device and object detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an information acquisition device and an object detection device mounted with the same, which can appropriately detect a distance to a detection object even when laser light of a plurality of wavelength bands is emitted from a laser light source of a single mode in actual measurement.SOLUTION: An information acquisition device 1 includes: a projection optical system 100; a light-receiving optical system 200; a heater 170; a heater control unit 21c; memory 28 for holding a reference template based on a reference image; and a distance acquisition unit 21b which refers to an actually measured image and the reference template, and acquires distance information on the basis of a positional relation between a segment area on the reference image and a comparison area on the actually measured image for the segment area. The heater control unit 21c changes a temperature of a laser light source 110 by the heater 170 on the basis of the determination that the laser light source 110 is shifted from a single mode oscillation state to a multimode oscillation state.

Description

  The present invention relates to an object detection apparatus that detects an object in a target area based on the state of reflected light when light is projected onto the target area, and an information acquisition apparatus suitable for use in the object detection apparatus.

  Conventionally, object detection devices using light have been developed in various fields. An object detection apparatus using a so-called distance image sensor can detect not only a planar image on a two-dimensional plane but also the shape and movement of the detection target object in the depth direction. In such an object detection apparatus, light in a predetermined wavelength band is projected from a laser light source or an LED (Light Emitting Diode) onto a target area, and the reflected light is received by a light receiving element such as a CMOS image sensor. Various types of distance image sensors are known.

  In a distance image sensor of a type that irradiates a target region with laser light having a predetermined dot pattern, reflected light from the target region of laser light having a dot pattern is received by a light receiving element. Then, based on the light receiving position of the dot on the light receiving element, the distance to each part of the detection target object (irradiation position of each dot on the detection target object) is detected using triangulation (for example, Patent Literature 1, Non-Patent Document 1).

JP 2012-32379 A

19th Annual Conference of the Robotics Society of Japan (September 18-20, 2001) Proceedings, P1279-1280

  In the object detection apparatus, for example, a single mode semiconductor laser that oscillates laser light in a single wavelength band and a diffractive optical element are used. The diffractive optical element converts laser light having a single wavelength band into laser light having a predetermined dot pattern by diffractive action. The dot pattern acquired by the light receiving element when this dot pattern is irradiated onto the reference surface is held in advance as a reference pattern, and the dot on the reference pattern is received on the dot pattern received by the light receiving element during actual operation. The distance to the detection target object is detected depending on which position it is moved to.

  However, in the single mode semiconductor laser, when the operating environment reaches a predetermined condition such as a temperature condition, the laser light may oscillate in a plurality of wavelength bands (multimode). When the laser light source oscillates in multimode in this way, the laser light is subjected to different diffractive effects by the diffractive optical element depending on the respective wavelengths, so that the dot pattern generated by the diffractive optical element changes from the reference pattern. . For this reason, the light reception position of a dot cannot be detected appropriately, but the problem that the detection accuracy of the distance to each part of a detection target object deteriorates arises.

  The present invention has been made in view of this point, and even when laser light of a plurality of wavelength bands is emitted from a single-mode laser light source at the time of actual measurement, the distance to the detection target object can be properly detected. An object is to provide an information acquisition apparatus and an object detection apparatus equipped with the information acquisition apparatus.

  A 1st aspect of this invention is related with the information acquisition apparatus which acquires the information of a target area | region using light. An information acquisition apparatus according to this aspect includes a laser light source that oscillates laser light and a diffractive optical element, and the laser light emitted from the laser light source is applied to a target region in a predetermined dot pattern by a diffractive action by the diffractive optical element. A projection optical system for projecting, a light receiving optical system for arranging the target area by an image sensor, arranged side by side with a predetermined distance from the projection optical system, and adjusting the temperature of the laser light source A temperature adjustment element; a temperature control unit that controls the temperature adjustment element; and a storage unit that holds reference information based on a reference dot pattern imaged by the light receiving optical system when the laser beam is irradiated on a reference surface; Referring to the actual measurement information based on the actual measurement dot pattern imaged by the image sensor at the time of actual measurement and the reference information, Comprising a irradiation area, based on the positional relationship between the actual dot pattern on the area corresponding to the reference region, and the distance acquisition section that acquires distance information for the reference region. The temperature control unit has determined that the laser light source has shifted from a single mode oscillation state in which laser light mainly in one wavelength band is emitted to a multimode oscillation state in which laser light in a plurality of wavelength bands is emitted. Based on the above, the temperature of the laser light source is changed by the temperature adjusting element.

  A 2nd aspect of this invention is related with an object detection apparatus. The object detection apparatus according to this aspect includes the information acquisition apparatus according to the first aspect.

  According to the present invention, an information acquisition device capable of appropriately detecting the distance to a detection target object even when laser light of a plurality of wavelength bands is emitted from a single mode laser light source at the time of actual measurement, and an object equipped with the information acquisition device A detection device can be provided.

  The effects and significance of the present invention will become more apparent from the following description of embodiments. However, the embodiment described below is merely an example when the present invention is implemented, and the present invention is not limited to the following embodiment.

It is a figure which shows the structure of the object detection apparatus which concerns on embodiment. It is a figure which shows the structure of the information acquisition apparatus and information processing apparatus which concern on embodiment. It is a perspective view which shows the external appearance of the projection optical system which concerns on embodiment, and a light-receiving optical system. It is a figure which shows the irradiation state of the laser beam with respect to the target area | region which concerns on embodiment, and the light reception state of the laser beam on an image sensor. It is a figure explaining the production | generation method of the reference pattern which concerns on embodiment. It is a figure explaining the distance detection method which concerns on embodiment. It is a figure explaining the method to hold | maintain a reference template according to the temperature change which concerns on embodiment. It is a figure which shows the example of the waveform of the laser beam of the single mode which concerns on embodiment, and the dot pattern on a light receiving element. It is a flowchart which shows the process of distance acquisition which concerns on embodiment. It is a flowchart which shows the heater control process which concerns on embodiment. It is a flowchart which shows the heater control process which concerns on the example of a change. It is a flowchart which shows the heater control process which concerns on the example of a change. It is a flowchart which shows the heater control process which concerns on the example of a change.

Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, an information acquisition device of a type that irradiates a target area with laser light having a predetermined dot pattern is exemplified.

  First, FIG. 1 shows a schematic configuration of the object detection apparatus according to the present embodiment. As illustrated, the object detection device includes an information acquisition device 1 and an information processing device 2. The television 3 is controlled by a signal from the information processing device 2.

  The information acquisition device 1 projects infrared light over the entire target area and receives the reflected light with a CMOS image sensor, whereby the distance between each part of the object in the target area (hereinafter referred to as “three-dimensional distance information”). To get. The acquired three-dimensional distance information is sent to the information processing apparatus 2 via the cable 4.

  The information processing apparatus 2 is, for example, a television control controller, a game machine, a personal computer, or the like. The information processing device 2 detects an object in the target area based on the three-dimensional distance information received from the information acquisition device 1, and controls the television 3 based on the detection result.

  For example, the information processing apparatus 2 detects a person based on the received three-dimensional distance information and detects the movement of the person from the change in the three-dimensional distance information. For example, when the information processing device 2 is a television control controller, the information processing device 2 detects the person's gesture from the received three-dimensional distance information, and outputs a control signal to the television 3 in accordance with the gesture. The application program to be installed is installed. In this case, the user can cause the television 3 to execute a predetermined function such as channel switching or volume up / down by making a predetermined gesture while watching the television 3.

  Further, for example, when the information processing device 2 is a game machine, the information processing device 2 detects the person's movement from the received three-dimensional distance information, and displays a character on the television screen according to the detected movement. An application program that operates and changes the game battle situation is installed. In this case, the user can experience a sense of realism in which he / she plays a game as a character on the television screen by making a predetermined movement while watching the television 3.

  FIG. 2 is a diagram illustrating configurations of the information acquisition device 1 and the information processing device 2.

  The information acquisition apparatus 1 includes a projection optical system 100 and a light receiving optical system 200 as a configuration of an optical unit. The projection optical system 100 and the light receiving optical system 200 are arranged in the information acquisition apparatus 1 so as to be aligned in the X-axis direction.

  The projection optical system 100 includes a laser light source 110, a collimator lens 120, a leakage mirror 130, a diffractive optical element (DOE) 140, an FMD (Front Monitor Diode) 150, a temperature sensor 160, and a heater 170. I have. The light receiving optical system 200 includes an aperture 210, an imaging lens 220, a filter 230, and a CMOS image sensor 240. In addition, the information acquisition apparatus 1 includes a CPU (Central Processing Unit) 21, a laser drive circuit 22, a PD signal processing circuit 23, a temperature detection circuit 24, a temperature adjustment circuit 25, and an image pickup as a circuit unit. A signal processing circuit 26, an input / output circuit 27, and a memory 28 are provided.

The laser light source 110 is a single mode semiconductor laser that oscillates in a single longitudinal mode and stably outputs laser light in a certain wavelength band. The laser light source 110 outputs laser light in a narrow wavelength band having a wavelength of about 830 nm in a direction away from the light receiving optical system 200 (X-axis negative direction). The collimator lens 120 converts the laser light emitted from the laser light source 110 into light slightly spread from parallel light (hereinafter simply referred to as “parallel light”).

  The leakage mirror 130 is formed of a multilayer film of dielectric thin films, and the number of layers and the thickness of the film are designed so that the reflectance is slightly lower than 100% and the transmittance is several steps smaller than the reflectance. The leakage mirror 130 reflects most of the laser light incident from the collimator lens 120 side in the direction toward the DOE 140 (Z-axis direction) and transmits the remaining part in the direction toward the FMD 150 (X-axis negative direction).

  The DOE 140 has a diffraction pattern on the incident surface. Due to the diffractive action of this diffraction pattern, the laser light incident on the DOE 140 is converted into laser light having a predetermined dot pattern and irradiated onto the target area.

  The diffraction pattern of the DOE 140 has, for example, a structure in which a step type diffraction hologram is formed in a predetermined pattern. The diffraction hologram is adjusted in pattern and pitch so as to convert the laser light converted into parallel light by the collimator lens 120 into laser light of a dot pattern.

  The DOE 140 irradiates the target region with the laser beam incident from the leakage mirror 130 as a laser beam having a dot pattern that spreads radially. The size of each dot in the dot pattern depends on the beam size of the laser light when entering the DOE 140.

  The FMD 150 receives the laser light transmitted through the leakage mirror 130 and outputs an electrical signal corresponding to the amount of received light.

  The temperature sensor 160 is configured by an NTC (negative temperaturecoefficient) thermistor. The NTC thermistor has a characteristic that the resistance value decreases with increasing temperature, and detects the temperature around the laser light source 110 from the change in resistance value. Then, the NTC thermistor outputs a signal corresponding to the detected temperature to the temperature detection circuit 24.

  The heater 170 is composed of a PTC (positive temperature coefficient) thermistor. The PTC thermistor has a characteristic in which the resistance suddenly increases at a predetermined temperature (Curie temperature), and a static characteristic (voltage-current characteristic) in which the resistance value fluctuates so as to have a constant power value with respect to an applied voltage exceeding a predetermined value. have. The PTC thermistor adjusts the ambient temperature of the laser light source 110 by generating heat at a constant temperature using static characteristics according to the output signal from the temperature adjustment circuit 25. The Curie temperature of the PTC thermistor is set slightly higher than the upper limit temperature that the laser light source 110 is supposed to reach during actual operation.

  The laser light reflected from the target area enters the imaging lens 220 via the aperture 210.

  The aperture 210 stops the light from the outside so as to match the F number of the imaging lens 220. The imaging lens 220 collects the light incident through the aperture 210 on the CMOS image sensor 240. The filter 230 is an IR filter (Infrared Filter) that transmits light in the infrared wavelength band including the emission wavelength (about 830 nm) of the laser light source 110 and cuts the wavelength band of visible light.

  The CMOS image sensor 240 receives the light collected by the imaging lens 220 and outputs a signal (charge) corresponding to the amount of received light to the imaging signal processing circuit 26 for each pixel. Here, in the CMOS image sensor 240, the output speed of the signal is increased so that the signal (charge) of the pixel can be output to the imaging signal processing circuit 26 with high response from the light reception in each pixel.

  The CPU 21 controls each unit according to a control program stored in the memory 28. With such a control program, the CPU 21 has a laser control unit 21a for controlling the laser light source 110, a distance acquisition unit 21b for generating three-dimensional distance information, and a heater control unit 21c for controlling the heater 170. Functions are granted.

  The laser drive circuit 22 drives the laser light source 110 according to a control signal from the CPU 21. The PD signal processing circuit 23 amplifies and digitizes the voltage signal corresponding to the amount of received light output from the FMD 150 and outputs it to the CPU 21. Based on the signal supplied from the PD signal processing circuit 23, the CPU 21 determines to amplify or decrease the light amount of the laser light source 110 by processing by the laser control unit 21a. When it is determined that the light amount of the laser light source 110 needs to be changed, the laser control unit 21 a transmits a control signal for changing the light emission amount of the laser light source 110 to the laser driving circuit 22. Thereby, the power of the laser beam emitted from the laser light source 110 is controlled to be substantially constant.

  The temperature detection circuit 24 digitizes a signal corresponding to the temperature output from the temperature sensor 160 and outputs it to the CPU 21. In the present embodiment, the temperature detection circuit 24 outputs the detected temperature in units of 0.2 ° C. The CPU 21 detects the emission wavelength variation of the laser light source 110 based on the signal supplied from the temperature detection circuit 24, and replaces the reference template for distance detection as will be described later. Note that the reference template replacement process according to the temperature change will be described later with reference to FIG.

  The temperature adjustment circuit 25 drives the heater 170 according to a control signal from the CPU 21. When the CPU 21 determines that the laser light source 110 is oscillating laser light in a plurality of wavelength bands instead of a single wavelength band by processing by the heater control unit 21c, the CPU 21 starts or stops the heater 170, and the laser light source Adjust the temperature around 110. The heater 170 driving process will be described later with reference to FIG.

  The imaging signal processing circuit 26 controls the CMOS image sensor 240 and sequentially takes in the signal (charge) of each pixel generated by the CMOS image sensor 240 for each line. Then, the captured signals are sequentially output to the CPU 21. Based on the signal (imaging signal) supplied from the imaging signal processing circuit 26, the CPU 21 calculates the distance from the information acquisition device 1 to each part of the detection target by processing by the distance acquisition unit 21b. Further, the CPU 21 adjusts the light receiving sensitivity of the CMOS image sensor 240 when the temperature around the laser light source 110 changes to a predetermined temperature or more by the drive control of the heater 170. The input / output circuit 27 controls data communication with the information processing apparatus 2.

  The information processing apparatus 2 includes a CPU 31, an input / output circuit 32, and a memory 33. In addition to the configuration shown in the figure, the information processing apparatus 2 is configured to communicate with the television 3, and to read information stored in an external memory such as a CD-ROM and install it in the memory 33. However, the configuration of these peripheral circuits is not shown for the sake of convenience.

  The CPU 31 controls each unit according to a control program (application program) stored in the memory 33. With such a control program, the CPU 31 is provided with the function of the object detection unit 31a for detecting an object in the image. Such a control program is read from a CD-ROM by a drive device (not shown) and installed in the memory 33, for example.

For example, when the control program is a game program, the object detection unit 31a detects a person in the image and its movement from the three-dimensional distance information supplied from the information acquisition device 1. Then, a process for operating the character on the television screen according to the detected movement is executed by the control program.

  When the control program is a program for controlling the function of the television 3, the object detection unit 31 a detects a person in the image and its movement (gesture) from the three-dimensional distance information supplied from the information acquisition device 1. To do. Then, processing for controlling functions (channel switching, volume adjustment, etc.) of the television 3 is executed by the control program in accordance with the detected movement (gesture).

  The input / output circuit 32 controls data communication with the information acquisition device 1.

  FIG. 3 is a perspective view showing an installation state of the projection optical system 100 and the light receiving optical system 200.

  The projection optical system 100 and the light receiving optical system 200 are disposed on the base plate 300. The optical members constituting the projection optical system 100 are installed in the housing 100a, and the housing 100a is installed on the base plate 300. Thereby, the projection optical system 100 is arranged on the base plate 300.

  The laser light source 110 is accommodated in a metal laser holder 110a having excellent thermal conductivity such as zinc or aluminum, and the laser holder 110a is bonded and fixed to the housing 100a.

  A circuit board 180 is disposed on the side surface (Y-axis negative direction) of the laser holder 110a, and a temperature sensor 160 (see FIG. 2) is provided between the circuit board 180 and the side surface (Y-axis negative direction) of the laser holder 110a. ) Is arranged. The temperature sensor 160 is electrically connected to the circuit board 180 and detects the temperature around the laser light source 110.

  A heater 170 is arranged on the upper surface (Z-axis positive direction) of the laser holder 110a. The heater 170 is bonded and fixed to a stainless steel flat plate 170a having excellent thermal conductivity, and the flat plate 170a is bonded and fixed to the upper surface (Z-axis positive direction) of the laser holder 110a. Although not shown, the heater 170 is electrically connected to the circuit board 180 and drives the heater 170 to adjust the temperature around the laser light source 110 via the flat plate 170a and the laser holder 110a.

  Reference numerals 150a and 240a denote FPCs (flexible printed circuit boards) for supplying signals from the FMD 150, the temperature sensor 160, the heater 170, and the CMOS image sensor 240 to a circuit board (not shown), respectively.

  The optical member constituting the light receiving optical system 200 is installed in the lens holder 200a, and the lens holder 200a is attached to the base plate 300 from the back surface of the base plate 300. As a result, the light receiving optical system 200 is disposed on the base plate 300. In the light receiving optical system 200, since optical members are arranged in the Z-axis direction, the height in the Z-axis direction is higher than that of the projection optical system 100. In the base plate 300, in order to suppress the height in the Z-axis direction, the periphery of the arrangement position of the light receiving optical system 200 is raised by one step in the Z-axis direction.

  In the installation state shown in FIG. 3, the positions of the exit pupil of the projection optical system 100 and the entrance pupil of the light receiving optical system 200 substantially coincide with each other in the Z-axis direction. Further, the projection optical system 100 and the light receiving optical system 200 are arranged with a predetermined distance in the X-axis direction so that the projection center of the projection optical system 100 and the imaging center of the light-receiving optical system 200 are aligned on a straight line parallel to the X axis. Installed at.

  The installation interval between the projection optical system 100 and the light receiving optical system 200 is set according to the distance between the information acquisition device 1 and the reference plane of the target area. The distance between the reference plane and the information acquisition device 1 varies depending on how far away the target is to be detected. The closer the distance to the target to be detected is, the narrower the installation interval between the projection optical system 100 and the light receiving optical system 200 is. Conversely, as the distance to the target to be detected increases, the installation interval between the projection optical system 100 and the light receiving optical system 200 increases. In the present embodiment, the installation interval between the projection optical system 100 and the light receiving optical system 200 is adjusted with a target at a certain distance (for example, several meters) as a detection target.

  FIG. 4A is a diagram schematically showing the irradiation state of the laser light on the target region, and FIG. 4B is a diagram schematically showing the light receiving state of the laser light in the CMOS image sensor 240. In FIG. 4B, for the sake of convenience, a flat surface (screen) in the target area and a light receiving state when a person is present in front of the screen are shown.

  As shown in FIG. 4A, the projection optical system 100 irradiates a target region with laser light having a dot pattern (hereinafter, the entire laser light having this pattern is referred to as “DP light”). . In FIG. 4A, the luminous flux region of DP light is indicated by a solid line frame. In the light flux of DP light, dot regions (hereinafter simply referred to as “dots”) due to the diffraction effect by the DOE 140 are scattered according to a dot pattern due to the diffraction effect by the DOE 140.

  When a flat surface (screen) is present in the target area, DP light reflected thereby is distributed on the CMOS image sensor 240 as shown in FIG.

  In FIG. 4B, the entire DP light receiving area on the CMOS image sensor 240 is indicated by a dashed frame, and the DP light receiving area incident on the imaging effective area of the CMOS image sensor 240 is indicated by a solid frame. Has been. The effective imaging area of the CMOS image sensor 240 is an area where the CMOS image sensor 240 receives a DP light and outputs a signal as a sensor, and has a size of, for example, VGA (horizontal 640 pixels × vertical 480 pixels). . Further, the light of Dt0 on the target area shown in FIG. 10A enters the position of Dt′0 shown in FIG. An image of a person in front of the screen is taken upside down on the CMOS image sensor 240 in the vertical and horizontal directions.

  Here, the distance detection method will be described with reference to FIGS.

  FIG. 5 is a diagram for explaining a reference pattern setting method used in the distance detection method.

  As shown in FIG. 5A, a flat reflection plane RS perpendicular to the Z-axis direction is disposed at a position of a predetermined distance Ls from the projection optical system 100. The emitted DP light is reflected by the reflection plane RS and enters the CMOS image sensor 240 of the light receiving optical system 200. Thereby, an electrical signal for each pixel in the effective imaging area is output from the CMOS image sensor 240. The output electric signal value (pixel value) for each pixel is developed on the memory 28 of FIG.

  Hereinafter, an image including all pixel values obtained by reflection from the reflection surface RS is referred to as a “reference image”, and the reflection surface RS is referred to as a “reference surface”. Then, as shown in FIG. 5B, a “reference pattern region” is set on the standard image. FIG. 5B shows a state in which the light receiving surface is seen through in the positive direction of the Z axis from the back side of the CMOS image sensor 240. The same applies to the drawings after FIG.

A plurality of segment areas having a predetermined size are set for the reference pattern area set in this way. The size of the segment area is determined in consideration of the contour extraction accuracy of the object based on the obtained distance information, the load of the calculation amount of distance detection for the CPU 21, and the error occurrence rate by the distance detection method described later. In the present embodiment, the size of the segment area is set to 15 horizontal pixels × 15 vertical pixels.

  With reference to FIG.5 (c), the segment area | region set to a reference pattern area | region is demonstrated. In FIG. 5C, for the sake of convenience, the size of each segment area is indicated by 7 pixels wide by 7 pixels high, and the center pixel of each segment area is indicated by a cross.

  As shown in FIG. 5C, the segment areas are set such that adjacent segment areas are arranged at intervals of one pixel in the X-axis direction and the Y-axis direction with respect to the reference pattern area. That is, a certain segment area is set at a position shifted by one pixel with respect to a segment area adjacent to the segment area in the X-axis direction and the Y-axis direction. At this time, each segment area is dotted with dots in a unique pattern. Therefore, the pattern of pixel values in the segment area is different for each segment area. The narrower the interval between adjacent segment areas, the greater the number of segment areas included in the reference pattern area, and the resolution of distance detection in the in-plane direction (XY plane direction) of the target area is enhanced.

  Thus, information on the position of the reference pattern area on the CMOS image sensor 240, pixel values (reference patterns) of all pixels included in the reference pattern area, and segment area information set for the reference pattern area are shown in FIG. 2 memory 28. These pieces of information stored in the memory 28 are hereinafter referred to as “reference templates”.

  The CPU 21 in FIG. 2 refers to the reference template when calculating the distance from the projection optical system 100 to each part of the detection target object. When calculating the distance, the CPU 21 calculates the distance to each part of the object based on the shift amount of the dot pattern in each segment area obtained from the reference template.

  For example, as shown in FIG. 5A, when an object is present at a position closer than the distance Ls, DP light (DPn) corresponding to a predetermined segment area Sn on the reference pattern is reflected by the object, and the segment area Sn. It is incident on a different region Sn ′. Since the projection optical system 100 and the light receiving optical system 200 are adjacent to each other in the X-axis direction, the displacement direction of the region Sn ′ with respect to the segment region Sn is parallel to the X-axis. In the case of FIG. 5A, since the object is at a position closer than the distance Ls, the region Sn 'is displaced in the positive direction of the X axis with respect to the segment region Sn. If the object is at a position farther than the distance Ls, the region Sn ′ is displaced in the negative X-axis direction with respect to the segment region Sn.

  Based on the displacement direction and displacement amount of the region Sn ′ with respect to the segment region Sn, the distance Lr from the projection optical system 100 to the part of the object irradiated with DP light (DPn) is triangulated using the distance Ls. Calculated based on Similarly, the distance from the projection optical system 100 is calculated for the part of the object corresponding to another segment area. The details of this calculation method are described in, for example, Non-Patent Document 1 (The 19th Annual Conference of the Robotics Society of Japan (September 18-20, 2001) Proceedings, P1279-1280).

  In this distance calculation, it is detected to which position the segment area Sn of the reference template has been displaced during actual measurement. This detection is performed by collating the dot pattern obtained from the DP light irradiated onto the CMOS image sensor 240 at the time of actual measurement with the dot pattern included in the segment region Sn. Hereinafter, an image made up of all the pixel values obtained from the DP light irradiated to the imaging effective area on the CMOS image sensor 240 at the time of actual measurement will be referred to as “measured image”. The effective imaging area of the CMOS image sensor 240 at the time of actual measurement is, for example, the size of VGA (horizontal 640 pixels × vertical 480 pixels), as in the case of acquiring the reference image.

  6A to 6E are diagrams for explaining such a distance detection method. FIG. 6A is a diagram showing a reference pattern region set in a standard image on the CMOS image sensor 240, and FIG. 6B is a diagram showing an actually measured image on the CMOS image sensor 240 at the time of actual measurement. FIG. 6C to FIG. 6E are diagrams for explaining a matching method between the dot pattern of the DP light included in the actual measurement image and the dot pattern included in the segment area of the reference template. For convenience, FIGS. 6 (a) and 6 (b) show only a part of the segment areas, and FIGS. 6 (c) to 6 (e) show the size of each segment area. It is shown by pixel × 9 pixels vertically. In addition, in the actual measurement image of FIG. 6 (b), for convenience, as shown in FIG. 4 (b), there is a person in front of the reference plane as a detection target object, and the image of the person is reflected. It is shown.

  When searching for the displacement position at the time of actual measurement of the segment area Si in FIG. 6A, as shown in FIG. 6B, the search area Ri is set for the segment area Si on the actual measurement image. The search area Ri has a predetermined width in the X-axis direction. The segment area Si is sent one pixel at a time in the search area Ri in the X-axis direction, and the dot pattern of the segment area Si is compared with the dot pattern on the measured image at each feed position. Hereinafter, a region corresponding to each feed position on the actually measured image is referred to as a “comparison region”. A plurality of comparison areas having the same size as the segment area Si are set in the search area Ri, and the comparison areas adjacent in the X-axis direction are shifted by one pixel from each other.

  The search area Ri is determined by the direction in which the detection target object is farther from the information acquisition apparatus 1 than the reference plane and how much distance is in the detectable direction. In FIG. 6, a shift of x pixels in the X-axis positive direction from a position shifted by x pixels in the negative X-axis direction from the pixel position (center pixel position) on the measured image corresponding to the pixel position of the segment region Si on the reference image. The search area Ri is set so that the segment area Si is sent in the range (hereinafter referred to as “search range Li”). In the present embodiment, a range from a position shifted by −30 pixels from the center pixel position to a position shifted by +30 pixels is set as the search range Li.

  While the segment area Si is fed pixel by pixel in the X axis direction in the comparison area, the degree of matching between the dot pattern of the segment area Si stored in the reference template and the dot pattern of the DP light of the measured image is obtained at each feed position. It is done. As described above, the segment area Si is sent only in the X-axis direction in the search area Ri as described above. Normally, the dot pattern of the segment area set by the reference template is a predetermined value in the X-axis direction at the time of actual measurement. This is because the displacement occurs only within the range.

  At the time of actual measurement, depending on the position of the detection target object, the dot pattern corresponding to the segment area may protrude from the actual measurement image in the X-axis direction. For example, when a dot pattern corresponding to the segment area S1 on the negative X-axis side of the reference pattern area is reflected by an object at a distance farther than the reference plane, the dot pattern corresponding to the segment area S1 is X more than the measured image. Positioned in the negative axis direction. In this case, since the dot pattern corresponding to the segment area is not within the effective imaging area of the CMOS image sensor 240, the segment area cannot be properly matched. However, since it is possible to perform matching appropriately in areas other than the end segment areas, there is little influence on object distance detection.

In addition, when matching is performed appropriately for the end region, the effective imaging region of the CMOS image sensor 240 at the time of actual measurement may be made larger than the effective imaging region of the CMOS image sensor 240 at the time of acquiring the reference image. What can be used should be used. For example, when an effective imaging area is set with a size of VGA (horizontal 640 pixels × vertical 480 pixels) at the time of acquiring a reference image, 30 pixels in the X-axis positive direction and X-axis negative direction than that when actually measured. The effective imaging area is set by a size that is larger. As a result, the actually measured image becomes larger than the reference image, but matching can be appropriately performed for the end segment area.

  When detecting the matching degree, first, the pixel value of each pixel in the reference pattern area and the pixel value of each pixel in each segment area of the actually measured image are binarized and stored in the memory 28. For example, when the pixel values of the reference image and the actually measured image are 8-bit gradations, among the pixel values of 0 to 255, the pixels that are equal to or greater than the predetermined threshold are the pixel values 1 and the pixels that are less than the predetermined threshold are pixels The value is converted to 0 and stored in the memory 28. Thereafter, the similarity between the comparison region and the segment region Si is obtained. That is, the difference between the pixel value of each pixel in the segment area Si and the pixel value of the corresponding pixel in the comparison area is obtained. A value Rsad obtained by adding the obtained difference to all the pixels in the comparison region is acquired as a value indicating the similarity.

  For example, as shown in FIG. 6C, when pixels of m columns × n rows are included in one segment area, the pixel values T (i, j) of the pixels of i columns and j rows of the segment area ) And the pixel value I (i, j) of the pixel in the comparison area i column and j row. Then, the difference is obtained for all the pixels in the segment area, and the value Rsad of the equation shown in FIG. 6C is obtained from the sum of the differences. The smaller the value Rsad, the higher the degree of similarity between the segment area and the comparison area.

  Thus, as shown in FIG. 6D, the value Rsad is obtained for all the comparison regions of the search region Ri for the segment region Si. FIG. 6E is a graph schematically showing the value Rsad at each feed position in the search area Ri. When the value Rsad is obtained for all the comparison regions of the search region Ri for the segment region Si, first, the minimum value Bt1 is referred to from the obtained value Rsad. Next, the second smallest value Bt2 is referred to from the obtained value Rsad. If the position of the minimum value Bt1 and the second smallest value Bt2 is two pixels or more and the difference value Es is less than the threshold value, the search for the segment area Si is considered as an error. On the other hand, if the difference value Es is equal to or greater than the threshold value, the comparison area Ci corresponding to the minimum value Bt1 is determined as the movement area of the segment area Si. For example, as shown in FIG. 6D, the comparison area Ci corresponding to the segment area Si is in the positive direction of the X axis with respect to the pixel position Si0 on the measured image at the same position as the pixel position of the segment area Si on the reference image. It is detected at a position shifted by α pixels. This is because the dot pattern of the DP light on the measured image is displaced in the X-axis positive direction from the segment area Si0 on the reference image by a detection target object (person) that is present at a position closer to the reference plane. Note that as the size of the segment region Si increases, the uniqueness of the dot pattern included in the segment region Si increases and the error rate decreases. For example, when the size of the segment region Si is set to 15 pixels wide × 15 pixels vertically, the distance detection usually does not cause an error, and matching can be performed appropriately.

  Thus, when the displacement position of each segment region is searched from the dot pattern of DP light acquired at the time of actual measurement, detection corresponding to each segment region is performed by triangulation based on the displacement position as described above. The distance to the part of the target object is obtained.

  In this manner, the same segment area search is performed for all the segment areas from the segment area S1 to the segment area Sn.

  FIG. 7A is a graph showing fluctuations in the emission wavelength of the laser light source 110 according to temperature changes. The horizontal axis represents the ambient temperature Tc of the laser light source 110, and the vertical axis represents the emission wavelength of the laser light source 110. The horizontal axis is scaled in increments of 0.2 ° C., as is the case with the fine detection temperature in the temperature detection circuit 24.

  Referring to FIG. 7A, the emission wavelength of the laser beam is stable at about 823.5 nm in the section where the ambient environment temperature Tc is 25 ° C. to 27.0 ° C. When the ambient environment temperature Tc reaches 27.2 ° C., the emission wavelength of the laser light varies to approximately 824.4 nm. This is a so-called mode in which the element temperature of the laser light source 110 changes as the ambient temperature Tc of the laser light source 110 changes, and the oscillation mode jumps to the adjacent longitudinal mode due to changes in the resonator length and gain spectrum. This is because a hopping phenomenon has occurred. After the mode hop occurs, the emission wavelength of the laser light is stable at about 824.4 nm.

  Next, when the ambient environment temperature Tc reaches 31.0 ° C., a mode hop occurs in the same manner, and the emission wavelength of the laser light changes to approximately 825.3 nm. Thereafter, the emission wavelength of the laser light is stable at about 825.3 nm. Further, when the ambient environment temperature Tc reaches 34.4 ° C., a mode hop occurs, and the emission wavelength of the laser light fluctuates to approximately 826.2 nm. Thereafter, except when the ambient environment temperature Tc is 37.6 ° C. It is stable at about 826.2 nm.

  Thus, in principle, in a single-mode semiconductor laser, the wavelength of the laser light does not continuously change according to the temperature change, but the wavelength changes by about 1 nm at the timing when the mode hop occurs. Therefore, the dot pattern is shifted at the timing when the mode hop occurs. In this case, the dot pattern can shift not only in the X-axis direction but also in the Y-axis direction. If the dot pattern deviates in the Y-axis direction, matching between the actually measured dot pattern and the dot pattern held in the reference template cannot be performed properly.

  Further, referring to FIG. 7A, even if a single mode semiconductor laser is used, a laser beam having a stable wavelength band is not always obtained in a temperature band where no mode hop occurs. I understand that. For example, the emission wavelength of the laser light when the ambient environment temperature Tc is 37.6 ° C. is about 826.7 nm, which is about 0.5 nm higher than the wavelengths at the front and rear temperatures.

  FIG. 8A shows the distribution of the output intensity of the laser beam obtained by the spectrum analyzer when the ambient environment temperature Tc is Tc1 (= 27.2 ° C.), and FIG. 8B shows the ambient environment temperature Tc is Tc2. It is a figure which shows typically distribution of the output intensity of the laser beam obtained by the spectrum analyzer at the time of (= 37.6 degreeC). 8A and 8B, the horizontal axis represents the wavelength (nm) of the laser beam, and the vertical axis represents the relative light output intensity (dBm) with respect to 1 mW. Note that the spectrum analyzer is generally used, and analyzes the distribution of the intensity of the light output according to the wavelength.

  Referring to FIG. 8A, when the ambient environment temperature Tc is Tc1, the laser light source 110 oscillates with high light intensity only when the center wavelength is 824.4 nm. That is, in the case of the ambient environment temperature Tc1, the laser light source 110 oscillates in a single mode. On the other hand, referring to FIG. 8B, when the ambient environment temperature Tc is Tc2, the laser light source 110 oscillates with a large light intensity in a plurality of wavelength bands whose center wavelengths are 826.2 nm and 827.1 nm. Yes. That is, in the case of the ambient environment temperature Tc2, the laser light source 110 oscillates in multimode. In addition, although the example which oscillates in two wavelength bands was shown in FIG.8 (b), it can also oscillate in three or more wavelength bands.

  8C and 8D are diagrams conceptually showing an example of dot incidence on the CMOS image sensor 240 and the output level of the pixel value when the laser light source 110 oscillates in a single mode. FIGS. 8E and 8F are diagrams conceptually showing an example of dot incidence on the CMOS image sensor 240 and the output level of the pixel value when the laser light source 110 oscillates in multimode. In FIGS. 8D and 8F, each pixel is indicated by darker hatching as the amount of incident dots is larger and the pixel value is higher.

  Referring to FIG. 8C, when the laser light source 110 oscillates in a single mode, as described above, the laser light is subjected to a predetermined diffraction action by the DOE 140 and has a dot Dt1 having a predetermined light intensity. A dot pattern is incident on the CMOS image sensor 240. At this time, as shown in FIG. 8D, a pixel value corresponding to the light intensity of the dot Dt1 is output from the CMOS image sensor 240. Then, it is determined whether each pixel value is equal to or greater than a predetermined threshold, and the pixel value is binarized. In the case of FIG. 8D, since a sufficiently large pixel value is output, it is identified that the dot Dt1 is incident on a dark hatched portion that exceeds the threshold value.

  On the other hand, when the laser light source 110 oscillates in a multi-mode, the laser light includes a plurality of wavelength bands. Therefore, the DOE 140 receives a different diffractive action depending on each wavelength, thereby producing a dot pattern. Is done. In this case, as shown in FIG. 8E, the laser light is a CMOS image sensor in a dot pattern in which one dot Dt1 (see FIG. 8C) in the single mode is separated into a plurality of dots Dt2. Incident on 240. At this time, the dot Dt2 is separated into a plurality of parts, so that the light intensity is lower than that in the single mode of FIG. Therefore, as shown in FIG. 8F, each pixel value is low according to the light intensity of the separated dot Dt2. Therefore, when the laser light source 110 oscillates in the multi mode, there is a possibility that the incident state of the dot Dt2 cannot be properly recognized.

  As described above, when the laser light source 110 oscillates in the multi-mode, it is difficult to identify dots on the CMOS image sensor 240, and there is a possibility that proper matching processing cannot be performed. As described above, when the reference template is generated in advance using the dot pattern of the laser light emitted in the single mode, if the laser light is emitted in the multimode at the time of actual measurement, the dot pattern is larger than that in the single mode. Fluctuating, and the matching accuracy between the dot pattern held in the reference template and the dot pattern acquired at the time of actual measurement is significantly deteriorated.

  Note that in a single mode semiconductor laser, the conditions, frequency, etc. for oscillating laser light in multiple modes vary depending on the individual semiconductor laser manufacturer. Further, as shown in FIG. 7A, in a single mode semiconductor laser, the temperature band in which laser light is oscillated in a multimode is in a very short range.

  As described above, when the laser light source 110 that oscillates in the single mode is used, the wavelength of the laser light output from the laser light source 110 changes stepwise for each predetermined temperature zone due to mode hopping. In addition, even within one temperature range, the laser light source 110 may oscillate in a multi-mode, which may cause deterioration in dot pattern matching accuracy.

  Therefore, in this embodiment, a reference template is prepared in advance for each temperature zone having a substantially constant wavelength, and is stored in the memory 28. At this time, the reference template of each temperature zone is acquired by imaging a dot pattern when the laser light source 110 oscillates in a single mode. At the time of actual measurement, the matching process described in FIGS. 6A to 6E is performed using a reference template in a temperature range including the temperature of the laser light source 110. Further, when it is determined that the laser light source 110 oscillates in the multimode, the heater 170 changes the temperature around the laser light source 110 so as to be out of the temperature band in which the laser light source 110 oscillates in the multimode.

FIG. 7B shows the reference template table RT. The reference template table RT is stored in the memory 28 in advance. Note that, in the reference template table RT of FIG. 7B, only the reference templates in some temperature zones are shown for convenience.

  In the reference template table RT, a reference template acquired at a wavelength corresponding to each temperature zone is stored in association with the temperature zone. The reference pattern areas of the reference template corresponding to each temperature zone are set to the same position with the same size. In the temperature zone, the temperature shown in FIG. 7A until the next mode hop occurs after the mode hop is set is set. Therefore, in the temperature zone adjacent to each other, the wavelength of the laser beam is shifted by about 1 nm.

  For example, when the temperature zone is 31.0 ° C. to 34.2 ° C., the dot pattern is obtained in a state where the laser light source 110 oscillates in a single mode and the wavelength of the laser light is approximately 825.3 nm (for example, temperature 32 ° C.) Is irradiated onto the reflection plane RS, and a reference image is acquired. Then, a reference template Rc is generated based on the acquired standard image, and the generated reference template Rc is set as a reference template in the temperature range of 31.0 ° C. to 34.2 ° C. Further, when the temperature range is 34.4 ° C. to 38.6 ° C., the dot pattern is obtained in a state where the laser light source 110 oscillates in a single mode and the wavelength of the laser light is approximately 826.2 nm (for example, temperature 36 ° C.). Is irradiated onto the reflection plane RS, and a reference image is acquired. Then, a reference template Rd is generated based on the acquired standard image, and the generated reference template Rd is set as a reference template in the temperature range of 34.4 ° C. to 38.6 ° C. Similarly, in the other temperature zones, the dot pattern is irradiated onto the reflection plane RS in a state where the wavelength of the laser beam is the wavelength of each temperature zone, and reference templates (Ra, Rb, Re,...) Are generated. The generated reference template is set as a reference template for the corresponding temperature zone.

  FIG. 9 is a flowchart showing distance acquisition processing. The processing of FIG. 9 is performed by the function of the distance acquisition unit 21b of the CPU 21 of FIG.

  Referring to FIG. 9, first, the CPU 21 acquires the current temperature around the laser light source 110 by the temperature sensor 160 (S101). Then, the CPU 21 sets the reference template in the temperature zone corresponding to the current temperature among the reference templates held in the reference template table RT as the reference template Rt used for distance measurement (S102). Thereafter, the CPU 21 determines whether it is the distance acquisition timing (S103). If it is not the distance acquisition timing (S103: NO), the process returns to S103 unless the shutdown is performed (S104: NO).

  When the distance acquisition timing is reached (S103: YES), the CPU 21 acquires the current temperature around the laser light source 110 by the temperature sensor 160 (S105). Then, the CPU 21 compares the acquired current temperature with the temperature zone Wu corresponding to the reference template currently set for distance measurement, and determines whether the current temperature is out of the temperature zone Wu (S106). If the current temperature is not out of the temperature zone Wu (S106: NO), the process proceeds to S108. If the current temperature is out of the temperature zone Wu (S106: YES), the CPU 21 is held in the reference template table RT. Among the reference templates, the reference template in the temperature range corresponding to the current temperature is reset to the reference template Rt used for distance measurement (S107).

  Thereafter, the CPU 21 uses the reference template Rt to collate with the dot pattern of the actually measured image and acquire the distance (S108). And CPU21 returns a process to S103 and repeats the process of distance acquisition.

  FIG. 10 is a flowchart showing the control process of the heater 170. The control process of FIG. 10 is performed to shift the laser light source 110 from the multimode oscillation state to the single mode oscillation state. This control process is performed in parallel with the control process of FIG. Moreover, this control process is performed by the function of the heater control part 21c of CPU21 of FIG.

  The CPU 21 acquires the ratio (matching error rate) Er of the segment areas in which the search is an error to the total segment areas in the search of the segment areas at the time of distance acquisition in S108 of FIG. 9 (S201). Then, the CPU 21 determines whether or not the matching error rate Er exceeds the threshold value Esh (S202). In addition, since the appropriate reference template corresponding to the current temperature is used in the processing of S106 and S107 in FIG. 9, it is normally assumed that the matching error rate does not exceed the threshold value Esh. However, as described above, when the laser light source 110 oscillates in the multi mode, the dot pattern at the time of actual measurement fluctuates greatly, and the matching error rate significantly increases. Therefore, even if the reference template corresponding to the current temperature is used as described above, it can be assumed that the laser light source 110 oscillates in a multimode when the matching error rate Er is large.

  If the matching error rate Er does not exceed the threshold value Esh (S202: NO), the CPU 21 advances the process to S203, and returns the process to S201 unless shutdown is performed (S203: NO). On the other hand, if the matching error rate Er exceeds the threshold value Esh (S202: YES), the CPU 21 determines that the laser light source 110 is oscillating in the multimode, advances the process to S204, and controls the heater 170.

  In S204, the CPU 21 determines whether or not the heater 170 is currently activated (S204).

  If the heater 170 is not currently activated (S204: NO), the CPU 21 activates the heater 170 (S205). As a result, the laser light source 110 is warmed, and the temperature of the laser light source 110 shifts from the temperature oscillating in the multimode to the temperature oscillating in the single mode. After starting the heater 170, the CPU 21 refers to the temperature detected by the temperature sensor 160 and waits for the temperature change ΔTu of the laser light source 110 after starting the heater 170 to exceed a predetermined temperature range ΔT0 (S206). Here, the temperature range ΔT0 is set to be slightly wider than the temperature range in which the laser light source 110 oscillates in the multimode, and is appropriately adjusted according to the tendency of the laser light source 110 to generate the multimode. Thereby, when the temperature change ΔTu exceeds the temperature range ΔT0, the laser light source 110 oscillates in a single mode.

  As described above, the temperature band in which the laser light source 110 oscillates in the multimode is very short, for example, about 0.4 ° C. in the case of FIG. In this case, at least by raising the temperature by 0.4 ° C. or more, the temperature of the laser light source 110 deviates from the temperature band in which oscillation occurs in the multimode, and the laser light source 110 oscillates in single mode.

  Thus, when the temperature change ΔTu exceeds the temperature range ΔT0 (S206: YES) and the laser light source 110 oscillates in the single mode, distance matching is appropriately performed in the distance acquisition step (S108) in the flowchart of FIG. Will come to be.

  Note that if the heater 170 is driven in S205 of FIG. 10 to increase the temperature of the laser light source 110, a mode hop may occur and the dot pattern may change. However, also in this case, the reference template is reset according to the temperature in S106 and S107 in FIG. 9, and thus distance matching is appropriately performed.

When the temperature change ΔTu thus exceeds the temperature range ΔT0, the CPU 21 increases the light receiving sensitivity of the CMOS image sensor 240 (S207). The CMOS image sensor 240 adjusts the light receiving sensitivity by increasing the exposure time or amplifying the output signal. In general, when the temperature of a laser element of a semiconductor laser rises, the amount of emitted laser light tends to decrease. Therefore, when the heater 170 is activated and the temperature around the laser light source 110 rises, the amount of laser light emitted from the laser light source 110 decreases, and the output signal (pixel value) on the CMOS image sensor 240 slightly decreases. To do. If the pixel value decreases in this way, the pixel value may fall below a threshold value for binarizing the measured image, which may have an undesired influence on the matching process.

  Therefore, after the heater 170 is started, in advance, in S207, the light receiving sensitivity of the CMOS image sensor 240 is increased to prepare for a decrease in the light emission amount of the laser light. Can keep. For this reason, distance matching can be performed more appropriately.

  After increasing the light receiving sensitivity of the CMOS image sensor 240 in this way, the CPU 21 returns the process to S201. In this case, since the laser light source 110 normally shifts to the single mode state by the processes of S205 and S206, the determination of the next S202 is NO.

  In S206 of FIG. 10, the heater 170 continues to be driven even after the temperature change ΔTu exceeds the temperature range ΔT0. For this reason, the temperature of the laser light source 110 continues to rise after that, and gradually moves away from the temperature at which oscillation occurs in the multimode. However, when the temperature rises in this way, the temperature of the laser light source 110 eventually reaches the next temperature (higher temperature) that oscillates in the multimode. Thereby, determination of S202 of FIG. 10 becomes YES and a process is advanced to S204. In this case, since the heater 170 is already in the drive state, in the process flowchart of FIG. 10, it is determined YES in S204, and the process proceeds to S208.

  If the determination in S204 is YES, the CPU 21 stops the heater 170 (S208). As a result, the temperature of the laser light source 110 that has been lifted decreases, and the laser light source 110 shifts from a temperature that oscillates in the multimode to a temperature that oscillates in the single mode. Thereafter, the CPU 21 refers to the temperature detected by the temperature sensor 160 and waits for the temperature change ΔTd of the laser light source 110 after stopping the heater 170 to exceed the temperature range ΔT0 (S209). When the temperature change ΔTd exceeds the temperature range ΔT0, the laser light source 110 oscillates in a single mode. Thereby, distance matching can be appropriately performed at the subsequent distance acquisition timing.

  When the temperature change ΔTd exceeds the temperature range ΔT0 after the heater 170 is stopped in this way, the CPU 21 decreases the light receiving sensitivity of the CMOS image sensor 240 increased in S207 (S210). Thereby, the CMOS image sensor 240 is adjusted to the light receiving sensitivity suitable for the light emission amount of the laser light from the laser light source 110.

  In S209, the heater 170 continues to be stopped even after the temperature change ΔTd exceeds the temperature range ΔT0. For this reason, the temperature of the laser light source 110 continues to decrease thereafter, and gradually deviates from the temperature at which oscillation occurs in the multimode. However, when the temperature decreases in this manner, the temperature of the laser light source 110 eventually reaches the next temperature (lower temperature) that oscillates in the multimode. In this case, in the process flowchart of FIG. 10, it is determined NO in S204, and the process proceeds to S205.

In this way, the heater 170 is started or stopped, and the laser light source 110 is adjusted from a state in which it oscillates in the multi mode to a state in which it oscillates in the single mode. And CPU21 returns the process of FIG. 10 to S201, and repeats the temperature adjustment process of the laser light source 110 again.

  As described above, according to the present embodiment, when the laser light oscillates in the multi mode, the temperature around the laser light source 110 is adjusted by the heater 170 so that the temperature of the laser light is emitted in the single mode. The distance can be detected properly.

  In addition, according to the present embodiment, since the light receiving sensitivity of the CMOS image sensor 240 is adjusted according to the start and stop of the heater 170, the pixel value can be kept appropriate even after the temperature rises due to the start of the heater 170. it can. Therefore, the distance can be detected more appropriately.

  In addition, according to the present embodiment, the reference template used for distance acquisition is replaced with an appropriate reference template according to the temperature change, so that the dot pattern is shifted in the Y-axis direction due to the wavelength shift of the laser light due to the temperature change. However, the distance can be detected appropriately.

  Moreover, according to this Embodiment, a reference template can be appropriately replaced by replacing a reference template at the timing when a mode hop in which the wavelength fluctuates stepwise occurs.

  Furthermore, in the present embodiment, the distance to the detection object is appropriately changed by changing the reference template according to the wavelength variation (temperature variation) without changing the wavelength constant by a temperature control element such as a Peltier element. It can measure with high accuracy. Thus, the cost and size of the object detection device can be reduced.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made to the embodiment of the present invention in addition to the above. .

  For example, in the above embodiment, after the heater 170 is started, the heater 170 remains started unless the matching error rate Er next exceeds a predetermined threshold value Esh. However, the flowchart shown in FIG. In addition, the heater 170 may be stopped after a predetermined time has elapsed since the activation of the heater 170.

  FIG. 11 is a flowchart showing stop control processing of the heater 170. The control process of FIG. 11 is executed when it is determined in the control process of FIG. 10 that the matching error rate Er does not exceed the threshold value Esh (S202: NO).

  Referring to FIG. 11, CPU 21 first determines whether heater 170 is currently activated (S301). If the heater 170 is not currently activated (S301: NO), the CPU 21 advances the process to S203 in FIG. If the heater 170 is currently activated (S301: YES), the CPU 21 determines whether the elapsed time (driving time) from the activation of the heater 170 exceeds a predetermined threshold Ts (S302). The driving time of the heater 170 is previously measured by the CPU 21 in the process of S205 in FIG. When the driving time of the heater 170 exceeds the threshold Ts (S302: YES), the CPU 21 stops the heater 170 (S303), and decreases the light receiving sensitivity of the CMOS image sensor 240 raised in S207 of FIG. 10 (S304). . On the other hand, when the driving time of the heater 170 does not exceed the threshold Ts (S302: NO), the CPU 21 advances the processing to S203 in FIG. 10 while driving the heater 170.

In this way, in this modified example, the heater 170 is automatically stopped when a predetermined time elapses after the heater 170 is started. As described above, the temperature band in which the laser light source 110 oscillates in multimode is very small. Further, since the temperature of the laser light source 110 rises by itself due to light emission, even if the heater 170 is stopped in this way, the temperature of the laser light source 110 does not normally return to the same temperature as when the heater 170 is started. It is assumed that 110 deviates from the temperature band in which oscillation occurs in the multimode. Therefore, as in this modified example, when a predetermined time has elapsed since the activation of the heater 170, power consumption can be suppressed by automatically stopping the heater 170. Note that after the heater 170 is automatically stopped, the laser light source 110 may return to the temperature band in which the laser light source oscillates in the multi mode. In this case, since the laser light source 110 can oscillate again in multi-mode, when detecting the distance more accurately, the heater 170 is stopped only when the matching error rate is deteriorated as in the above embodiment. Or it is better to start.

  In the case of this modification, the temperature range to be raised by the activation of the heater 170 can be adjusted by adjusting the threshold value Ts. As described above, since the temperature band in which the laser light source 110 oscillates in the multimode is very short, the temperature range raised by the activation of the heater 170 may be small, and therefore the threshold value Ts may be short. If the threshold value Ts is shortened in this way, the amount of decrease in the amount of laser light emitted as the temperature rises can be made small. Therefore, when the threshold value Ts is set short in this modification, the light receiving sensitivity adjustment step (S207, S210, S304) of the CMOS image sensor 240 may be omitted.

  Note that S302 in the flowchart of FIG. 11 can be changed so that the heater 170 is stopped when the temperature increase after starting the heater 170 exceeds a predetermined threshold. The predetermined time of claim 5 includes a time until a temperature rise reaches or exceeds a predetermined temperature range in addition to a mode in which the time is set in advance as shown in FIG.

  Moreover, in the said embodiment, even if the reference template according to temperature was used, when the matching error rate exceeded the predetermined threshold value, it determined with the laser light source 110 being in the state which is oscillating in multimode. However, it may be determined by other methods that the laser light source 110 is in a state of oscillating in a multimode. For example, for each laser light source 110, laser light is emitted while changing the temperature, the wavelength of the laser light is measured with a spectrum analyzer, and the temperature band in which the laser light is emitted in multimode is determined from the measurement result. You may make it acquire. In this case, the acquired temperature band is held in the memory 28. In the actual operation, when the temperature of the laser light source 110 is included in the temperature band held in the memory 28, it is determined that the laser light source 110 is in a multimode oscillation state, and the heater 170 is driven.

  FIG. 12 is a flowchart showing the control process of the heater 170 in this case. The control process of FIG. 12 is executed instead of the control process of FIG.

  Referring to FIG. 12, the CPU 21 first determines whether or not the current temperature is included in the multimode oscillation temperature range previously stored in the memory 28 (S401). When the current temperature is included in the multi-mode oscillation temperature range (S401: YES), the CPU 21 performs start-up and stop processing of the heater 170 (S204 to S210) as in the above embodiment. On the other hand, when the current temperature is not included in the multimode oscillation temperature range (S401: NO), the CPU 21 advances the process to S203, and returns the process to S401 unless shutdown is performed (S203: NO).

  As a result, as in the above embodiment, when the laser light source 110 oscillates in multimode, the heater 170 adjusts the temperature around the laser light source 110 so that the laser light source 110 oscillates in single mode. The distance can be detected properly.

  In this modified example, if the temperature range in which the laser light source 110 oscillates in a multimode varies due to some factor after the manufacture and shipment of the information acquisition apparatus 1, it becomes impossible to appropriately control the temperature of the laser light source 110. Accordingly, the laser light source 110 oscillates in a multimode by a method capable of grasping a change in the laser light emission state of the laser light source 110 as appropriate, such as evaluating the matching error rate as in the above embodiment. It is better to judge whether or not.

  Further, instead of the method of measuring the wavelength state of the laser light with a spectrum analyzer, the control shown in FIG. 13 is performed during a predetermined idle operation so that the temperature range where the laser light source 110 oscillates in the multimode is acquired. May be.

  In this control, during a predetermined idle operation, the laser light source 110 and the heater 170 are activated (S501), and distance measurement is executed by the processing of FIG. 9 (S502). Then, at the distance acquisition timing, the matching error rate Er is obtained (S503), and when the obtained matching error rate Er exceeds the threshold value Esh (S504: YES), the laser light source 110 is oscillating in multimode. The current temperature at that time is stored in the memory 28 (S505). The above process is repeated until the temperature of the laser light source 110 reaches the operation upper limit temperature of the laser light source 110 (S506). Then, when the temperature of the laser light source 110 reaches the operation upper limit temperature (S506: YES), the laser light source 110 and the heater 170 are stopped, and the process ends.

  In this process, the temperature held in the memory 28 in S505 is referred to as the temperature at which the laser light source 110 oscillates in multimode. That is, the processing flow of FIG. 12 is executed using the temperature held in the memory 28 as the multimode oscillation temperature zone in S401 of FIG.

  In the above embodiment, the heater 170 is driven to warm the periphery of the laser light source 110 and adjust the temperature. For example, a ventilation hole is provided in the vicinity of the laser light source 110, and air is blown from the ventilation hole. The temperature of the laser light source 110 may be adjusted by sending and cooling the periphery of the laser light source 110. In this case, since it is necessary to provide a blowing means such as a fan in order to generate wind, the information acquisition device 1 is likely to be increased in size. For this reason, as described above, it is desirable to warm the laser light source 110 with the heater 170 using a PTC thermistor.

  Note that the present invention is also applicable to a configuration in which the temperature of the laser light source 110 is controlled to be substantially constant by a temperature control element such as a Peltier element. That is, even if temperature control is performed using a Peltier element, the temperature of the laser light source 110 changes within a predetermined temperature range. For this reason, a temperature at which the laser light source 110 oscillates in a multimode may be included in the temperature range. In such a case, instead of providing the heater 170, the temperature range controlled by the Peltier element is shifted in the direction in which the temperature rises or falls from the current temperature range. As a result, the temperature of the laser light source 110 changes to a temperature at which the laser light source 110 oscillates in a single mode.

  In the above embodiment, the reference template is held at the temperature interval from the occurrence of the mode hop until the next occurrence of the mode hop. However, after the occurrence of the mode hop, the next mode hop is 2 The reference template may be held at a temperature interval until it occurs more than once. In this case, the calculation amount for the CPU 21 can be suppressed.

In the above embodiment, the segment areas are set so that the adjacent segment areas overlap each other, but the segment areas may be set so that the segment areas adjacent to the left and right do not overlap each other. The segment areas may be set so that the segment areas adjacent in the vertical direction do not overlap each other. Further, the shift amount of the segment areas adjacent in the vertical and horizontal directions is not limited to one pixel, and the shift amount may be set to another number of pixels. Moreover, in the said embodiment, although the magnitude | size of the segment area | region was set to horizontal 15 pixels x vertical 15 pixels, it can set arbitrarily according to detection accuracy. Furthermore, in the said embodiment, although the segment area | region was set to square shape, a rectangle may be sufficient.

  In the above embodiment, the pixel values of the pixels included in the segment area and the comparison area are binarized before calculating the matching rate between the segment area and the comparison area. Matching may be performed using the values as they are. In the above embodiment, the pixel value obtained by the CMOS image sensor 240 is binarized as it is. However, the pixel value is subjected to correction processing such as predetermined pixel weighting processing and background light removal processing. After performing, it may be binarized or multi-valued.

  Further, in the above embodiment, the distance information is obtained by using the triangulation method and stored in the memory 27. However, when the main purpose is to extract the contour of the object, the distance using the triangulation method is set. The displacement amount (pixel displacement amount) of the segment area may be acquired as the distance information without calculating.

  Further, in the above embodiment, the filter 230 is disposed to remove light in a wavelength band other than the wavelength band of the laser light irradiated to the target region. For example, light other than the laser light irradiated to the target region is used. In the case where a circuit configuration for removing the signal component is removed from the signal output from the CMOS image sensor 240, the filter 230 can be omitted. Further, the arrangement position of the aperture 210 may be between any two imaging lenses.

  In the above embodiment, the CMOS image sensor 240 is used as the light receiving element, but a CCD image sensor may be used instead. Furthermore, the configurations of the projection optical system 100 and the light receiving optical system 200 can be changed as appropriate. The information acquisition device 1 and the information processing device 2 may be integrated, or the information acquisition device 1 and the information processing device 2 may be integrated with a television, a game machine, or a personal computer.

  The embodiments of the present invention can be appropriately modified in various ways within the scope of the technical idea shown in the claims.

DESCRIPTION OF SYMBOLS 1 ... Information acquisition apparatus 21 ... CPU (distance acquisition part, temperature control part)
21b ... Distance acquisition unit 21c ... Heater control unit (temperature control unit)
25 ... Temperature adjustment circuit (Temperature controller)
26 ... Imaging signal processing circuit (distance acquisition unit)
28 ... Memory (storage unit)
DESCRIPTION OF SYMBOLS 100 ... Projection optical system 110 ... Laser light source 140 ... DOE (diffractive optical element)
170… Heater (temperature adjustment element)
200 ... Light receiving optical system 240 ... CMOS image sensor (image sensor)
S1 to Sn: Segment area (reference area)
Ra to Re ... Reference template (reference information)
Er ... Matching error rate (matching rate)

Claims (8)

In an information acquisition device that acquires information on a target area using light,
A projection optical system that includes a laser light source that oscillates laser light and a diffractive optical element, and that projects the laser light emitted from the laser light source onto a target area with a predetermined dot pattern by diffractive action by the diffractive optical element;
A light receiving optical system that is arranged so as to be laterally separated by a predetermined distance with respect to the projection optical system, and that captures the target area by an image sensor;
A temperature adjusting element for adjusting the temperature of the laser light source;
A temperature control unit for controlling the temperature adjusting element;
A storage unit that holds reference information based on a reference dot pattern imaged by the light receiving optical system when the laser beam is irradiated on a reference surface;
Referring to the actual measurement information based on the actual measurement dot pattern imaged by the image sensor at the time of actual measurement and the reference information, a reference area on the standard dot pattern and an area on the actual measurement dot pattern corresponding to the reference area A distance acquisition unit that acquires distance information with respect to the reference region based on the positional relationship;
The temperature control unit has determined that the laser light source has shifted from a single mode oscillation state in which laser light mainly in one wavelength band is emitted to a multimode oscillation state in which laser light in a plurality of wavelength bands is emitted. And changing the temperature of the laser light source by the temperature adjusting element,
An information acquisition apparatus characterized by that. The information acquisition device according to claim 1,
The distance acquisition unit increases the light receiving sensitivity of the image sensor based on the temperature control unit using the temperature adjustment element to increase the temperature of the laser light source.
An information acquisition apparatus characterized by that. In the information acquisition device according to claim 1 or 2,
The temperature adjustment element is a heater that raises the temperature of the laser light source.
An information acquisition apparatus characterized by that. In the information acquisition device according to claim 3,
The temperature control unit drives the heater based on the determination that the laser light source has shifted from the single mode oscillation state to the multi-mode oscillation state, and then the laser light source is again the single mode oscillation state. Based on determining that the mode has shifted from the mode oscillation state to the multi-mode oscillation state, the heater is stopped.
An information acquisition apparatus characterized by that. In the information acquisition device according to claim 3,
The temperature control unit drives the heater for a predetermined time based on determining that the laser light source has shifted from the single-mode oscillation state to the multi-mode oscillation state.
An information acquisition apparatus characterized by that. In the information acquisition device according to any one of claims 1 to 5,
The storage unit holds a plurality of types of the reference information according to the wavelength of the laser beam,
The distance acquisition unit selects the reference information corresponding to the current wavelength from the plurality of types of reference information stored in the storage unit, and acquires the distance information using the selected reference information. Run,
An information acquisition apparatus characterized by that. The information acquisition apparatus according to claim 6,
The reference information held in the storage unit is acquired based on laser light when the laser light source oscillates in the single mode,
The temperature control unit controls the temperature adjustment element based on a matching rate between the actual measurement information acquired at the time of actual measurement and the reference information selected by the distance acquisition unit.
An information acquisition apparatus characterized by that.   The object detection apparatus which has an information acquisition apparatus as described in any one of Claims 1 thru | or 7.

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