JP2010203864A - Object detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microminiature object detection device capable of detecting not only existence, a direction or a distance of a detection object but also a shape or a size thereof. <P>SOLUTION: This object detection device 1 includes: a rotation driving means for rotating a light emitting element 3, and a diffraction optical element 4 for changing light irradiated therefrom into linear light; an imaging element 5 for generating a pattern of reflected light by receiving the reflected light reflected from a detection object existing in a detection domain formed by scanning by the linear light in a direction orthogonal to the linear direction; and a detection circuit 6 for detecting the existence, the direction, the shape or the size of the detection object from the pattern of the reflected light generated by the imaging element. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an object detection apparatus that detects an object (detected object) such as a human body, an automobile, or an obstacle using visible light, near-infrared light, or far-infrared light, and in particular, MEMS (Micro Electro Mechanical Systems) technology. The object detection apparatus is miniaturized using a small optical deflector formed by the above.

  Conventionally, it has been proposed to reduce the size of an object detection device using an optical deflector formed in an ultra-small size using the MEMS technology.

  For example, the object detection apparatus disclosed in Patent Document 1 is a light emitting element that irradiates a detection area with light, a light reception element that receives reflected light reflected from an object to be detected in the detection area, and rotates the light reception element. And a rotation driving means for detecting and a detection means for obtaining an intensity distribution of the reflected light received by the light receiving element.

  The rotational driving means is connected to at least a pair of piezoelectric unimorph diaphragms, a support body having a hollow portion for fixing and supporting one end of the piezoelectric unimorph diaphragms, and the piezoelectric unimorph diaphragms via elastic bodies, The piezoelectric unimorph diaphragm is configured to include a substrate that rotates and vibrates in the cavity by piezoelectric driving, and the light receiving element is disposed on the substrate.

  The detection means detects the presence and direction of the detected object from the intensity distribution of the reflected light with respect to the rotation angle of the substrate.

  According to this object detection device, it is possible to detect the presence and direction of an object to be detected using a light emitting diode as a light emitting element. Further, by providing a plurality of the light receiving elements on the same plane, the distance from the plane to the object to be detected can be obtained.

JP 2008-249212 A

  However, in the object detection apparatus as described above, it is desired to detect not only the presence, direction and distance of the detected object, but also the shape and size of the detected object. Further, if the distance to the object to be detected can be obtained without installing a plurality of light receiving elements, further downsizing of the article detection apparatus can be achieved.

  An object of the present invention is to provide an ultra-small object detection apparatus that can detect not only the presence, direction, or distance of an object to be detected, but also the shape and size.

  The object detection apparatus of the present invention includes a light emitting element, a diffractive optical element that converts light emitted from the light emitting element into linear light, a rotation driving unit that rotates the light emitting element and the diffractive optical element, and the line. An image sensor that receives reflected light reflected from an object to be detected in a detection region formed by scanning the light in a direction orthogonal to the line direction, and generates a pattern of the reflected light by the image sensor Detecting means for detecting the presence, direction, shape, or size of the object to be detected from the generated reflected light pattern, and the rotation driving means includes at least a pair of piezoelectric unimorph diaphragms, and the piezoelectric unimorphs. A support that fixes and supports one end of the diaphragm, and a substrate that is connected to the piezoelectric unimorph diaphragm and that vibrates and rotates by piezoelectric driving of the piezoelectric unimorph diaphragm. Characterized in that said light emitting element on the plate and the diffractive optical element is disposed.

  According to the object detection device of the present invention, the light emitted from the light emitting element is converted into linear light by the diffractive optical element. The linear light is scanned in a direction orthogonal to the linear direction while being rotationally oscillated by the piezoelectric drive of the piezoelectric unimorph diaphragm, thereby forming a planar linear light pattern.

  At this time, if there is an object in the detection area, the reflected light pattern of the linear light generated by the image sensor is distorted according to the shape and size of the object. If the range is detected by the detection means, the shape and size of the object can also be known. That is, the shape and size of an object can be detected in addition to the presence and direction of an object without performing conventional complicated image processing.

  Further, according to the object detection device of the present invention, since the shape of the object is detected based on the distortion of the reflected light pattern, the resolution of the image sensor is lower than that of a general camera image sensor. As a result, the manufacturing cost of the apparatus can be reduced by using an inexpensive image sensor. Further, since the reflected light pattern necessary for detecting the object can be generated with a low resolution, the sensitivity can be increased by setting the number of pixels for imaging low. This makes it possible to detect the shape of the object even when the light emitted from the light emitting element is weak.

  In the object detection device according to the aspect of the invention, it is preferable that the light emitting element is controlled to emit pulsed light synchronized with the imaging frequency of the imaging element.

  In this case, the distance to the detected object can be calculated without providing a plurality of light receiving elements by applying the pulsed light to the detected object and measuring the time until the reflected light is received. Further, by adding the calculation result of the distance and the calculation result of the shape of the object, it is possible to calculate the exact size of the detection object.

  In a preferred embodiment of the present invention, a light emitting diode (LED) can be used as the light emitting element. For example, a laser source and a device for driving the laser source have a complicated structure and are expensive, and laser light may damage the retina when it enters the human eye due to its high directivity and convergence. On the other hand, in addition to being simpler and less expensive than a laser source, an LED has excellent directivity and convergence as a light-emitting element, and thus has excellent safety in terms of eye-safety.

  Further, in the present invention, since the object can be detected even if the light emitted from the light emitting element is weak, it is possible to avoid the problem of performance deterioration due to the temperature rise of the LED, which is a problem when emitting a large amount of light. .

  Further, as the light emitting element, a vertical cavity surface emitting laser (VCSEL) can be used. In the case of a VCSEL, since the divergence angle is smaller than that of the LED, it is possible to detect far away. Further, since the output is lower than that of a general edge-emitting laser, the eye-safe problem is alleviated.

  The object detection apparatus of the present invention includes a control unit that controls a light emission frequency of the light emitting element or a rotation speed of the rotation driving unit, and the control unit performs a first control for scanning the presence / absence of an object to be detected. It is desirable to have a mode and a second control mode for scanning the type of object to be detected. In the first control mode, the light emission frequency of the light emitting element or the rotation speed of the rotation driving means is controlled to be relatively low, and in the second control mode, the light emission frequency of the light emitting element or the rotation speed of the rotation driving means is relatively controlled. High control.

  The first mode by this control means is a mode for detecting only the presence / absence of an object, and the number of scanning lines is not so required. In the first mode, when an object is present in the detection area, the presence of the object is known from the distortion of the scanning line light.

  Next, in the second mode by the control unit, imaging is performed by relatively increasing the light emission frequency of the light emitting element or the rotation speed of the rotation driving unit and increasing the number of scanning lines as compared with the first mode. The resolution of the image data in the element can be increased, and the direction, distance, shape and size of the object can be detected.

  As a result, with this control means, the presence and distance of an object are detected by rough scanning in the first mode, and the shape and size of the object are detected by fine scanning in the second mode thereafter. Can do. For this reason, it becomes possible to fully utilize the capability of the arithmetic element used as a detection means. That is, even if an inexpensive arithmetic element with low processing capability is used, the object can be detected, and the manufacturing cost can be suppressed.

The perspective view which shows the object detection apparatus of one Embodiment of this invention. 1 is a perspective view showing an optical scanner according to an embodiment of the present invention. FIG. 4A is a perspective view showing the optical scanner when stationary, and FIG. 4B is an explanatory perspective view showing when the optical scanner is driven. An explanatory plan view showing a substrate of an optical scanner. Sectional drawing which follows the VV line | wire of FIG. Explanatory drawing which shows that the light emitted from the light source is converted into linear light. BRIEF DESCRIPTION OF THE DRAWINGS Explanatory perspective view which shows irradiation of the linear light pattern of the object detection apparatus of one Embodiment of this invention. It is explanatory drawing which shows the principle of the object detection of this invention, (a) is a pattern figure of the reflected light when a to-be-detected area does not have a to-be-detected area, (b) is a case in which a to-be-detected object exists in a to-be-detected area. Reflected light pattern diagram. BRIEF DESCRIPTION OF THE DRAWINGS Explanatory perspective view which shows irradiation of the pulsed light by the object detection apparatus of one Embodiment of this invention.

  As shown in FIG. 1, the object detection apparatus 1 of this embodiment includes an optical scanner 2 using MEMS. A light emitting element 3 and a diffractive optical element 4 for converting light from the light emitting element 3 into linear light 16 (FIGS. 6 and 7) are provided on a substrate 12 (FIG. 4) that rotates and vibrates in the optical scanner 2. It is joined.

  In addition, the object detection device 1 of the present embodiment includes the imaging element 5 that generates the reflected light 17 reflected from the detection object W (see FIG. 9) in the detection area of the linear light 16 from the light emitting element 3; And a detection circuit 6 that detects the reflected light 17 generated by the image sensor 5.

  The light emitting element 3 is composed of an LED that generates incoherent light that is inexpensive and easy to handle, and irradiates the detection region with visible light or near infrared light.

  As the image sensor 5, a CMOS image sensor used in a general video camera can be used. In the case of object detection, since it is not necessary to be full color, a monochrome CMOS image sensor for a surveillance camera is sufficient. The resolution of the image sensor can also be a low resolution less than VGA, so that the manufacturing cost can be reduced.

  The light emission central axis of the light emitting element 3 and the image pickup central axis of the image pickup element 5 are arranged to coincide with each other.

  The image sensor 5 may be mounted by a general method in which the image sensor 5 is electrically connected to the package by wire bonding after die bonding with a die attach agent. However, if it is a CMOS image sensor with a through electrode, it can be connected by a solder ball grid array (hereinafter referred to as BGA).

  Next, the principle of rotational vibration of the optical scanner 2 will be described with reference to FIGS.

  The optical scanner 2 is formed by forming a piezoelectric thin film such as lead zirconate titanate (hereinafter PZT) on a silicon wafer, etching the silicon wafer into a cantilever structure, and expanding and contracting the piezoelectric body by applying a voltage. The piezoelectric unimorph diaphragm 8 taken out as the tip displacement is used as a basic driving source.

  As shown in FIG. 2, the optical scanner 2 includes piezoelectric vibrating portions 9 and 10 in which a plurality of piezoelectric unimorph diaphragms 8 are connected while being folded back, and a support 11 that fixes and supports one end of each piezoelectric vibrating portion 9 and 10. And a substrate 12 that rotationally vibrates and is connected between the pair of piezoelectric vibrating portions 9 and 10.

  As shown in FIG. 3A, the folded piezoelectric unimorph diaphragm 8 constituting each of the piezoelectric vibrating portions 9 and 10 is skipped by one to form two lines of electrical wiring.

  As shown in FIG. 3 (b), the deflection principle of the substrate 12 is such that the piezoelectric unimorph diaphragms 8 are alternately turned up and down by applying reverse applied voltages to the odd-numbered and even-numbered piezoelectric unimorph diaphragms 8 respectively. And a large deflection angle is generated at the tip portions of the piezoelectric vibrating portions 9 and 10.

  Although the displacement amount of the piezoelectric unimorph diaphragm 8 itself is very small, a large deflection angle can be given by integrating the displacement, and a practically sufficient deflection angle can be obtained without using mechanical resonance.

  As shown in FIGS. 4 and 5, the substrate 12 includes an electrode wiring 13, and the light emitting element 3 is connected to the electrode wiring by flip chip mounting. This connection can be performed by, for example, AuSn eutectic bonding, Au-Au solid phase diffusion bonding, or bonding by the illustrated Au bump 15. According to this bonding, it is easy to dispose the diffractive optical element 4 on the light emitting element 3 as compared with the known wire bonding, and the wire bonding wire is disconnected even when the substrate 12 rotates and vibrates. There is an advantage that there is a low risk of doing so. But you may mount by wire bonding.

  The light emitting element 3 may be bonded by mounting a chip on the substrate 12 with a die bonder, or may be bonded on a processed wafer of the optical scanner 2 at a wafer level.

  In normal flip chip mounting, the growth substrate GaAs or sapphire is positioned on the uppermost surface. However, the presence of the growth substrate having a thickness of 100 μm or more with respect to the light emitting device 3 having a thickness of 10 μm or less is the light emitting element 3. And diffractive optical element 4 may be obstructed.

  In order to avoid this, after bonding the LED as the light emitting element 3 on the substrate 12, the growth substrate may be removed to leave only the epi-growth light emitting portion, so-called thin film LED may be used. In the case of the thin-film LED, the substrate 12 can be oscillated and rotated according to the design of the optical scanner 2 because the mass of the substrate 12 hardly changes.

  The diffractive optical element 4 is a planar optical element in which a transparent resin coated on a glass wafer or a plastic substrate is pressed with a finely processed mold to form a complex concavo-convex pattern on the surface, and light emission bonded to the substrate 12 Arranged on the element 3.

  In order to dispose the diffractive optical element 4, for example, as shown in the drawing, a method of directly adhering to the light emitting element 3 via the optical adhesive 14, and an adhesion to only the substrate 12 without adhering to the light emitting element 3. There is a way to do it. Which one is selected is determined in consideration of the overall dimensions, the light emission wavelength of the LED, the material of the diffractive optical element, the linearization rate, and the like.

  As shown in FIGS. 6A to 6F, the diffractive optical element 4 converts Lambertian alignment light from the light emitting element 3 into linear light 16 having a one-dimensional alignment. For example, in the case of an LED, since the coherency is small compared to a laser, it does not have a strict sense of a linear shape, but is clearly linear compared to a basic light emission pattern (FIGS. 6A and 6B). It is possible to form an orientation (FIGS. 6E and 6F) that is visible to the orientation.

  Next, the principle of object detection will be described.

  First, as shown in FIG. 7, the linear light 16 formed by the light emitting element 3 and the diffractive optical element 4 is scanned in a direction orthogonal to the linear direction of the linear light 16 while being rotationally oscillated by the optical scanner 2. Thus, a pattern of planar linear light 16 is formed.

  When there is no object in the detection area, the pattern of the linear light 16 is generated in the image pickup device 5 as a pattern of the reflected light 17 of the linear light 16 without being disturbed (FIG. 8A )). On the other hand, when an object is present in the detection area, the pattern of the reflected light 17 of the linear light 16 is such that the pattern of each linear light 16 is distorted according to the shape and size of the object. 5 (FIG. 8B).

  By detecting the distortion position and distortion range of the reflected light 17 of each imaged linear light 16 by the detection means, not only the presence and direction of the object but also the shape and size thereof without complicated image processing. Can be detected.

  At this time, as shown in FIG. 9, when the light emission of the light emitting element 3 is a pulsed light synchronized with the imaging frequency of the imaging element 5, the time until the light is reflected by the object and returns to the imaging element is measured. It is possible to calculate the distance to the object based on the principle of time of flight (TOF).

  Moreover, the size of the object can be accurately detected by adding the results of the distance and the shape of the object.

  In the present embodiment, a detection circuit 6 having a CPU is provided as a control means for controlling the light emission frequency of the light emitting element 3 or the rotation speed of the substrate 12 by the optical scanner 2. The CPU has a first control mode for scanning the presence / absence of the detected object and a second control mode for scanning the type of the detected object. In the first control mode, the light emission frequency of the light emitting element 3 or the rotation speed of the substrate 12 by the optical scanner 2 is controlled relatively low, and in the second control mode, the light emission frequency or the rotation speed is relatively high. Control.

  This first control mode is a mode for detecting only the presence / absence of an object, and does not require a large number of scanning lines. For example, the scanning frequency may be set to 10 Hz and the linear light 16 may be scanned. In the first control mode, when an object is present in the detection area, the presence of the object is known from the distortion of the linear light 16.

  In the second control mode, compared with the first mode, the light emission frequency or the rotation speed is relatively high. For example, by setting the scanning frequency to 100 Hz and increasing the number of scanning lines, the image data in the image sensor is increased. Can be detected and the direction, distance, shape and size of the object can be detected.

  As a result, the presence and distance of the object can be detected by the rough scan in the first control mode, and the shape and size of the object can be detected by the fine scan in the second control mode thereafter. It is possible to make full use of these capabilities. That is, even if an inexpensive arithmetic element with low processing capability is used, the object can be detected, and the manufacturing cost can be suppressed.

The small object detection device of the present invention is suitably used in the following fields.
・ Detection of passengers in the passenger seat of a car (Difference between adult / child and human / dog)
・ Automobile pre-crash detection system ・ Product sorting in different types of mixed lines

A diffractive optical element in which an AlGaAs LED chip having a substrate size of 2 mm square and a chip size of 4 mm square is flip-chip mounted with a 300 μm square and an emission wavelength of 830 nm is molded on a glass wafer. The device was bonded with a UV curable resin. This optical scanner and a 300,000 pixel monochrome CMOS image sensor produced in a separate process were mounted on an HTCC package with the optical axis aligned. Finally, the package was sealed with glass with a double-sided AR coating for a wavelength of 830 nm.

  This package, the control circuit, and the power supply unit were combined into a single housing to produce an extremely small object detection device that is about the size of a match box.

  This device was applied to the detection of an occupant of an automobile, that is, an application for detecting whether a person is sitting in a passenger seat.

  The scanning frequency was 10 Hz during rough scanning, 100 Hz during fine scanning, and the light emission output was 5 mW. The scanning angle was 60 ° in all optical angles. The imaging element was provided with a visible light cut filter and set to capture only the scanning line light.

  As a result, it was found that not only whether a person is sitting, but also whether it is an adult or a child, a child or a dog, can be discriminated by the distortion of the linear light and can be used sufficiently for occupant detection.

DESCRIPTION OF SYMBOLS 1 ... Object detection apparatus, 2 ... Optical scanner, 3 ... Light emitting element, 4 ... Diffraction optical element, 5 ... Imaging element, 6 ... Detection circuit, 8 ... Piezoelectric unimorph diaphragm, 9 ... Piezoelectric vibration part, 10 ... Piezoelectric unimorph vibration Group of plates, 11 ... support, 12 ... substrate, 13 ... electrode wiring, 14 ... optical adhesive, 15 ... Au bump, 16 ... linear light, 17 ... reflected light, W ... detected object.

Claims (4)

A light emitting element;
A diffractive optical element that converts light emitted from the light emitting element into linear light;
Rotation driving means for rotating the light emitting element and the diffractive optical element;
An imaging device that receives reflected light reflected from an object to be detected in a detection region formed by scanning the linear light in a direction perpendicular to the linear direction, and generates a pattern of the reflected light;
Detecting means for detecting the presence, direction, shape or size of the object to be detected from the pattern of the reflected light generated by the image sensor;
The rotation driving means includes at least a pair of piezoelectric unimorph diaphragms, a support that fixes and supports one end of the piezoelectric unimorph diaphragm, and is connected to the piezoelectric unimorph diaphragm and is driven by piezoelectric driving of the piezoelectric unimorph diaphragm. An object detection apparatus comprising: a substrate that rotates and vibrates, wherein the light emitting element and the diffractive optical element are disposed on the substrate.   The object detection apparatus according to claim 1, wherein the light emitting element emits pulsed light synchronized with a photographing frequency of the image pickup element.   The object detection device according to claim 1, wherein the light emitting element is a light emitting diode. The object detection device according to any one of claims 1 to 3,
Control means for controlling at least the light emission frequency of the light emitting element or the rotational speed of the rotation driving means
The control means has a first control mode for scanning the presence / absence of an object to be detected and a second control mode for scanning the type of the object to be detected,
In the first control mode, the light emission frequency of the light emitting element or the rotation speed of the rotation driving unit is controlled to be relatively low, and in the second control mode, the light emission frequency of the light emitting element or the rotation driving unit of the rotation driving unit is controlled. An object detection apparatus characterized by controlling a rotational speed to be relatively high.