JP2009128026A - Apparatus and method for detecting object - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly accurately detect objects by an extremely simple constitution through the use of the reaction of a laser light source caused by an extremely small scattered return light. <P>SOLUTION: An object detection apparatus is provided with the light source 10 for emitting a laser beam; a photo-detector 20 for detecting output changes of the light source 10 caused by incoherent light among scattered light generated when a laser beam emitted from the light source 10 hits an object; and a detector 30 for detecting the presence or absence of an object to be detected on the basis of detection results by the photo-detector 20. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an object detection apparatus and an object detection method for detecting an object on an optical path of a laser beam.

  The conventional type laser object sensor uses a laser beam emitted from a light source to capture a change in state by blocking, reflecting, or strongly scattering a certain object. In this method, if the signal from the object to be measured (information due to state change) does not reach the photodetector, it will not be at a practical level. Therefore, highly accurate and stable optical axis alignment, focus control on the object to be measured, Position control, irradiation of a strong luminance beam to the object to be measured, and the like are required, and a complicated servo configuration is required.

  In addition, when the presence of transmitted light is observed, the position of the light detector generally needs to be installed at a location far away from the light source. When viewing reflected light, the reflector is installed at a location away from the light source. In addition, it is necessary to manage the position of the detector with high accuracy.

  Here, Patent Document 1 discloses a semiconductor laser digital vibration displacement measuring apparatus that detects Doppler beat waves by irradiating an object with laser light. Further, Patent Document 2 discloses a sensing technique using return light to a laser.

Japanese Patent No. 3282746 Japanese Patent Laid-Open No. 51-126646

  However, when detecting strong scattered light such as a laser Doppler velocimeter, it is necessary to increase the measurement sensitivity by placing the object to be measured not far from the light source or detector, and its application range is extremely limited. Will receive. Also, since sensing using the return light to the laser uses a relatively high region where the return light rate exceeds 0.01%, so-called return light noise is large and unstable and practical. Absent.

  The present invention has been made to solve such problems. That is, the present invention includes a light source that emits laser light, a light receiving unit that detects an output change of the light source due to incoherent light among scattered light generated when the laser light emitted from the light source strikes an object, It is an object detection apparatus provided with the detection means which detects the presence or absence of the object used as a detection target based on the detection result by a means.

  In the present invention, since the laser beam emitted from the light source hits the object and the influence of the incoherent light on the output of the light source among the scattered light generated at that time is detected by the light receiving means, the coherence length of the light source Even a distant object can be detected using extremely small scattered return light (incoherent light).

  According to the present invention, in addition to the above-described configuration, the lens for condensing the laser light emitted from the light source, the driving means for adjusting the focal position of the lens, the focal position of the lens is adjusted by the driving means, and the light receiving means It is also an object detection apparatus provided with the control means which controls so that a detection value may become the maximum.

  In the present invention, the focal position of the lens is adjusted so that the detection value by the light receiving means is maximized by utilizing the fact that the scattered return light is strongest when the object is at the focal position of the lens that collects the laser light. By adjusting, even a very small scattered return light can be detected with high accuracy. Further, according to the present invention, the distance to the object can be detected based on the focal position when the detection value by the light receiving means is maximized.

  In addition, by using multimode laser light as the laser light emitted from the light source, or using laser light in an oscillation mode that is mode-hopped from the oscillation mode closest to the laser light oscillation threshold, extremely small scattering return Even light can be detected with high accuracy.

  In the present invention, since an object on the optical path of the laser light emitted from the light source can be detected, the laser light is reflected by the reflecting means or the laser light is branched by the branching means. It can be set to expand the object detection range.

  In addition, the present invention is an object detection method using a laser light emitting device including a light source that emits laser light and a light receiving unit that detects an output change of the laser light emitted from the light source, and the laser light emitted from the light source. Is an object detection method in which the light receiving means detects the output change of the light source due to incoherent light among the scattered light generated when the light hits the object, and detects the presence or absence of the object to be detected based on the detection result.

  In the present invention, since the laser beam emitted from the light source hits the object and the influence of the incoherent light on the output of the light source among the scattered light generated at that time is detected by the light receiving means, the coherence length of the light source Even a distant object can be detected using extremely small scattered return light (incoherent light).

  The present invention is also an object detection method in which the focal length of a lens that collects laser light emitted from a light source is adjusted, and control is performed so that the detection value by the light receiving means is maximized.

  In the present invention, the focal position of the lens is adjusted so that the detection value by the light receiving means is maximized by utilizing the fact that the scattered return light is strongest when the object is at the focal position of the lens that collects the laser light. By adjusting, even a very small scattered return light can be detected with high accuracy. Further, according to the present invention, the distance to the object can be detected based on the focal position when the detection value by the light receiving means is maximized.

  In the object detection method of the present invention, multimode laser light is used as laser light emitted from the light source, or laser light in an oscillation mode that is mode-hopped from the oscillation mode closest to the laser light oscillation threshold is used. Thus, even a very small amount of scattered return light can be detected with high accuracy.

  Further, in the object detection method of the present invention, since an object on the optical path of the laser light emitted from the light source can be detected, the laser light is reflected by the reflecting means, or the laser light is branched by the branching means, An object detection range can be expanded by setting a desired optical path.

  Therefore, according to the present invention, it is possible to detect an object with a very simple configuration and high accuracy by utilizing a reaction of a laser light source by extremely small scattered return light.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The object detection device and the object detection method according to the present embodiment have a configuration for detecting whether or not an object to be detected exists on the optical path of the laser light, and based on this configuration, the distance to the object is determined. It can also be detected.

  In particular, this embodiment has advantages such as simplified device configuration and relaxed installation restrictions compared to conventional photosensors, so it is suitable for sensing with a mobile object in addition to fixed sensing. It becomes.

  That is, in the conventional photosensor shown in FIG. 8, the light emitted from the laser light source on the left side is set to enter the photosensor on the right side. At this time, if a blocking object enters the optical path, the light is interrupted, so that the optical sensor can detect this and send a signal to a device that notifies or records the presence of an intruder (object).

  Therefore, in such a setting, it is necessary to install the light source and the optical sensor at a certain distance. If you want to make both installations closer, you can use a reflector, but in that case the mirror still needs to be installed away from the light source and the light sensor, and the position of the light sensor can receive the mirror reflected light well. Must be installed accurately.

  For this reason, for example, when detecting that an object has entered the vehicle, it is difficult to install a mirror in the adjacent car, and it is not easy to set the position of the optical sensor that receives the reflected light well. . As described above, the optical sensing according to the conventional method has many restrictions on installation, requires maintenance, and is not suitable for sensing with a moving body.

<First Embodiment>
FIG. 1 is a schematic diagram for explaining a first embodiment of the present invention. That is, the object detection apparatus according to the first embodiment includes a light source (for example, a semiconductor laser) 10 that emits laser light, and a photodetector (for example, a photodiode) that detects an output of the laser light emitted from the light source 10. 20 and a detector 30 that detects the presence or absence of an object to be detected based on the detection result of the light detector 20. In this light detector 20, the laser light emitted from the light source 10 is applied to the object. A change in the output of the light source 10 due to incoherent light (return light) among the scattered light generated upon hitting is detected, and the presence or absence of an object to be detected is determined from this detection result.

  Specifically, a lens 11 for collimating the laser light emitted from the light source 10 is provided, and a beam splitter 12 for branching the laser light is disposed at the subsequent stage of the lens 11. One of the laser beams branched by the beam splitter 12 goes straight as it is and becomes an optical path for object detection. The other of the laser beams branched by the beam splitter 12 is reflected at a right angle and enters the photodetector 20. The photodetector 20 outputs an electrical signal corresponding to the amount of incident light. As a result, the output of the laser light emitted from the light source 10 can be monitored.

  An amplifier 21 that amplifies the output signal is provided at the subsequent stage of the photodetector 20, and a filter 22 that passes only a predetermined frequency band is provided at the subsequent stage, and a signal that has passed through the filter 22 is sent to the detector 30. ing.

  Next, the operation (object detection method) of the object detection apparatus according to the present embodiment will be described. First, the laser light emitted from the light source 10 is collimated into parallel light by the lens 11 and emitted far away. At this time, the optical path is divided into two by the beam splitter 12 arranged at the rear stage of the lens 11, and one of them is put into the photodetector 20 without surface scattering (PD optical path). Then, the electric signal from the photodetector 20 is amplified by the amplifier 21, and the signal is monitored as sound by an acoustic device, for example.

  At this time, if a certain vibration scatterer (for example, paper that is not a mirror surface) is in another optical path (detection optical path) branched by the beam splitter 12, incoherent light of the scatterer is returned as a light source. Will come back to 10. A part of the incoherent scattered light returns to the semiconductor laser as the light source 10 in spite of the extremely small intensity of about 0.01% or less of the emitted laser light, and generates a return light reaction signal.

  This generated signal is reliably generated in an acoustic signal band of 1 Hz to 100 kHz as long as the degree of temporal coherence of the laser beam remains, and when this signal is monitored by an acoustic amplifier (amplifier 21), it is detected with good S / N and is a detection target. The frequency of the output sound is changed in response to the vibration state of the object. This sound can be heard as if a bird screams. Note that the return light reaction signal does not necessarily have to be output as a sound, and may be handled later in the form of an electrical signal whose frequency changes. In the following description, this return light reaction signal will be referred to as Peep Signal (PS).

  The detector 30 detects this PS, and if a PS exceeding a preset threshold (a signal absolute value or a frequency change threshold) is input, an object to be detected exists on the detection optical path. to decide.

  The detectable distance of the object according to the present embodiment varies depending on the coherence length of the semiconductor laser that is the light source 10. For example, if a general-purpose red laser for DVD (single mode) outputs several mW, the coherence length is about 20 cm, and the detectable distance is about 5 m to 7 m.

  Further, if a DFB (Distributed Feedback) laser having a longer coherence length or a VCSEL (Vertical Cavity Surface Emitting Laser) is used, a longer distance can be detected. In addition, in the present embodiment, since the output change of the light source 10 due to the return light due to the incoherent light among the scattered light generated when the laser light hits the object is detected, the coherence of the laser light emitted from the light source 10 is detected. It is possible to detect even an object that is more distant than the length.

  Further, even a very weak signal such as scattered light can be detected sufficiently even if the scattering surface does not necessarily enter the optical path perpendicularly. Further, even black paper or cloth can be detected as long as scattered light is emitted. At this time, the amount of laser light emitted from the light source 10 can be sensed even at several mW or less (for example, 1 mW).

  Further, PS is generated without any problem even if the detection optical path is bent by a mirror and the object is a scatterer on the bent optical path. In other words, if the detectable distance depends on the coherence length of the laser beam, PS will be generated if a detection light path is blocked by a scatterer regardless of how it bends or how it branches. The branching will be described later.)

  If the phenomenon by the structure of this embodiment is utilized, the optical sensing which is simple and easy to install will be possible. The signal from the optical detector 20 is amplified and put in a filter having a certain characteristic frequency (for example, per 1 kHz) corresponding to PS, and if the signal is detected, a scatterer characterized by vibration corresponding to the signal ( (Object) can be detected. Of course, if a filter is not used, it can be used as a scatterer (object) against any vibration.

  Further, the PS signal can be analyzed more quantitatively by using, for example, a voiceprint spectrum analyzer, and the inherent vibration of the scatterer (object) can be analyzed and identified as “individuality”. In other words, by configuring such a feature extractor as the detector 30, it becomes possible to identify and recognize the substance to be measured (living organism), and it can be applied to personal authentication similar to a fingerprint or a voiceprint. Become.

  For example, each human is considered to have a unique “vibration state”. If you hold a scattered light card with your finger and hold it over the laser beam path (detection beam path), you can detect the inherent vibration of that person. As a result, it can be used to some extent to determine whether or not the person is the person. Of course, the vibration state may change due to illness or fatigue, but it can also be used to determine the health condition.

  Furthermore, using this technique, the laser beam can be used for non-contact diagnosis of an isolated patient. Recently, the occurrence of new infectious diseases is known (Thurs, etc.), and the situation in which contact-type diagnosis such as thermometers and stethoscopes is difficult is increasing. According to the present embodiment, since the configuration is simple, it can be expected to check the state of the circulatory organ and sound by irradiating the chest and throat of the patient in the isolation room for a short time and detecting the scattered light.

  Moreover, the object detection apparatus of this embodiment has versatility in terms of installation and is easy to use. As long as the laser beam is emitted, PS can be detected when a scatterer that blocks the optical path enters, and can be detected. The light source 10, the photodetector 20, and the detector 30 and a power source (not shown) can be accommodated in one casing on the same side, and can be closed as a single product.

  Further, installation is easy and complicated optical path adjustment is unnecessary. In addition, if the object detection device of the present embodiment is attached to a moving body, it can be detected as long as the scatterer enters the detection optical path. It is possible to use it for prevention and optical sensors of robots.

  Furthermore, in the object detection apparatus of the present embodiment shown in FIG. 1, the lens 11 at the rear stage of the light source 10 may be a condensed light beam instead of collimating the laser light. In this case, if there is an object to be detected at the condensing point, the signal level of PS increases dramatically compared to the case of collimated light. For example, compared to the case where laser light is used as collimated light, a PS level of about 10 times or more can be obtained when the condensed light is used.

  When the lens 11 is a condensing type, an object existing at the focal position can be adjusted manually or by setting a specific focal position in advance by lens design. Can be detected with high sensitivity. This is suitable when the detection range is determined to some extent or when it is desired to accurately detect an object within a specific range, in consideration of the detection accuracy (threshold for object detection) at the detector 30. It is also possible to prevent false detection outside a specific range.

  Moreover, you may make it the structure which can adjust the focus position of the lens 11 used as a condensed light ray. FIG. 2 is a schematic diagram illustrating an example provided with a configuration capable of adjusting the focal position of a lens. That is, in this object detection device, in addition to the configuration including the light source 10, the beam splitter 12, the photodetector 20, the amplifier 21, the filter 22, and the detector 30, the laser beam is condensed by the lens 11, A lens driving unit 110 that adjusts the focal position and a control unit 111 that adjusts the focal position of the lens 11 by the lens driving unit 110 and performs feedback control so that the detection value by the photodetector 20 is maximized.

  With this configuration, the control unit 111 changes the focus position of the lens 11 by controlling the focus position, and adjusts the detection value of the photodetector 20 to be maximized by applying focus servo. Note that the control unit 111 normally sets the focal position of the lens 111 to infinity, and applies focus servo when the PS is detected. This makes it possible to detect an object on the detection optical path with high accuracy.

  In addition, when the control unit 111 applies focus servo and the detection value of the light detector 20 becomes maximum, the detection unit 30 receives a signal given to the lens driving unit 110 at this time and calculates the focal position of the lens 11. Then, it is possible to detect the distance from the focal position to the object in a certain distance range. Furthermore, when this configuration is made with laser arrays having different condensing distances, distance recognition can be performed instantaneously (simultaneously). Further, this configuration can be a microphone or a vibration sensor of a specific part.

Second Embodiment
FIG. 3 is a schematic diagram for explaining a second embodiment of the present invention. This object detection device is characterized in that the detection optical path is terminated and safety measures are applied. That is, the object detection apparatus according to the second embodiment is the same as that of the first embodiment in that it includes a light source 10, a lens 11, a beam splitter 12, a photodetector 20, an amplifier 21, a filter 22, and a detector 30. The difference is that a substance that induces light scattering is disposed at the end of the detection optical path that passes through the beam splitter 12.

  Thereby, it can prevent that the laser beam radiate | emitted to the detection optical path is radiated | emitted to infinity. In particular, when a DFB laser having a long coherence length is used as the light source 10, a signal from a distant scatterer may be detected as noise. Therefore, this can be avoided by terminating the detection optical path as in the present embodiment.

  Here, when terminated with a substance that induces light scattering, PS is generated, so that it can be used without blackbody reflection or scattering. For example, an absorption type ND filter 13 having no reflected light is suitable. In addition, a non-scattering type beam termination device called Beam Trp or Beam Block can be used.

  The operation (object detection method) of the object detection apparatus according to the second embodiment is the same as that of the first embodiment. That is, the laser light emitted from the light source 10 is collimated into parallel light by the lens 11 and emitted far away. At this time, the optical path is branched into two by the beam splitter 12 arranged at the rear stage of the lens 11, and one of the optical paths is put into the photodetector 20 having no surface scattering (PD optical path). Then, the electric signal from the photodetector 20 is amplified by the amplifier 21, and the signal is monitored as sound by an acoustic device, for example.

  At this time, if there is a vibration scatterer having another optical path (detection optical path) branched by the beam splitter 12 (for example, paper that is not a mirror surface), incoherent light of the scatterer is returned as the light source 10. Come back to. Then, the influence of the light source 10 due to the return light is captured by the photodetector 20, PS is generated, and the presence or absence of an object is determined by the detector 30.

  Although not shown, in the object detection device of the second embodiment, similarly to the first embodiment, the lens 11 is a condensing type so that an object at a specific distance can be detected with high sensitivity. The focal position of the lens 11 may be adjusted by a lens driving unit. Further, the adjustment of the focal position may be feedback-controlled by the control unit so that the detection value of the photodetector 20 is maximized, or the focal position of the lens 11 is calculated from the feedback control signal, You may make it detect the distance to an object.

<Third Embodiment>
FIG. 4 is a schematic diagram for explaining a third embodiment of the present invention. This object detection device is characterized in that the detection optical path is folded back many times by a mirror to make the sensing range planar. That is, the object detection apparatus according to the third embodiment is the same as that of the first embodiment in that it includes the light source 10, the lens 11, the beam splitter 12, the photodetector 20, the amplifier 21, the filter 22, and the detector 30. The difference is that the detection optical path passing through the beam splitter 12 is reflected by a plurality of mirrors 120, a return optical path is set, and the optical path is terminated.

  In this way, even if the detection optical path is folded back by a plurality of mirrors 120, if it falls within the detectable distance depending on the coherence length of the light source 10, it can be detected if the scatterer (object) blocks somewhere in the sensed light, The detection range (area) can be expanded.

  The operation (object detection method) of the object detection apparatus according to the third embodiment is the same as that of the first embodiment. That is, the laser light emitted from the light source 10 is collimated into parallel light by the lens 11 and emitted far away. At this time, the optical path is branched into two by the beam splitter 12 arranged at the rear stage of the lens 11, and one of the optical paths is put into the photodetector 20 having no surface scattering (PD optical path). Then, the electric signal from the photodetector 20 is amplified by the amplifier 21, and the signal is monitored as sound by an acoustic device, for example.

  At this time, if there is a vibration scatterer (for example, paper that is not a mirror surface) in the detection light path branched by the beam splitter 12 or the detection light path folded by the plurality of mirrors 120, incoherent light of the scatterer returns. It returns to the light source 10 as light. Then, the influence of the light source 10 due to the return light is captured by the photodetector 20, PS is generated, and the presence or absence of an object is determined by the detector 30.

  Although not shown, in the object detection device of the third embodiment, similarly to the first embodiment, the lens 11 is a condensing type so that an object at a specific distance can be detected with high sensitivity. The focal position of the lens 11 may be adjusted by a lens driving unit. Further, the adjustment of the focal position may be feedback-controlled by the control unit so that the detection value of the photodetector 20 is maximized, or the focal position of the lens 11 is calculated from the feedback control signal, You may make it detect the distance to an object.

  In this embodiment, in addition to the configuration in which the detection optical path is folded back by the mirror 120, it is possible to scan a light beam with a rotating galvanometer mirror to perform a wide range of detection. In this case, the mirror 120 is unnecessary.

<Fourth embodiment>
FIG. 5 is a schematic diagram for explaining the fourth embodiment of the present embodiment. This object detection device is characterized in that the detection optical path is branched by a plurality of beam splitters 121 to widen the sensing range. That is, the object detection apparatus according to the fourth embodiment is the same as that of the first embodiment in that it includes a light source 10, a lens 11, a beam splitter 12, a photodetector 20, an amplifier 21, a filter 22, and a detector 30. The difference is that the detection optical path passing through the beam splitter 12 is branched by a plurality of beam splitters 121, and the detection optical path is divided into a plurality of branches.

  As described above, even if the detection optical path is branched by the plurality of beam splitters 121, since it can be detected that the scatterer blocks light in any of the branch optical paths, it is possible to detect the entering body over a wide range.

  The merit of the present embodiment is that, when the approaching body places, for example, a black body in the detection optical path, the detection becomes difficult, but by making the optical path configuration that makes it difficult to determine the mainstream detection optical path, Such interference can be reduced. Also, by installing a plurality of such object detection devices, it becomes possible to detect the act of inserting a black body, thereby clearing the security problem. Further, if the coherence can be maintained even if the optical fiber is used as a part of the detection optical path, light scattering by the entry body on the detection optical path after being emitted from the optical fiber can be detected.

  The operation (object detection method) of the object detection apparatus according to the fourth embodiment is the same as that of the first embodiment. That is, the laser light emitted from the light source 10 is collimated into parallel light by the lens 11 and emitted far away. At this time, the optical path is branched into two by the beam splitter 12 arranged at the rear stage of the lens 11, and one of the optical paths is put into the photodetector 20 having no surface scattering (PD optical path). Then, the electric signal from the photodetector 20 is amplified by the amplifier 21, and the signal is monitored as sound by an acoustic device, for example.

  At this time, if there is a vibration scatterer (for example, non-specular paper) in the detection optical path branched by the beam splitter 12 or the detection optical path branched by the plurality of beam splitters 121, incoherent light of the scatterer returns. It returns to the light source 10 as light. Then, the influence of the light source 10 due to the return light is captured by the photodetector 20, PS is generated, and the presence or absence of an object is determined by the detector 30.

  Although not shown, in the object detection device of the fourth embodiment, as in the first embodiment, the lens 11 is a condensing type so that an object at a specific distance can be detected with high sensitivity. The focal position of the lens 11 may be adjusted by a lens driving unit. Further, the adjustment of the focal position may be feedback-controlled by the control unit so that the detection value of the photodetector 20 is maximized, or the focal position of the lens 11 is calculated from the feedback control signal, You may make it detect the distance to an object.

<Fifth Embodiment>
FIG. 6 is a schematic diagram for explaining the fifth embodiment of the present embodiment. This object detection apparatus is characterized in that a rear monitor photodiode provided in a package of a light source (semiconductor laser) 10 is usually used as the photodetector 20. In FIG. 6, only the light source 10, the photodetector 20, and the lens 11 are shown, but the other configurations are the same as those shown in FIG.

  Thus, by using the rear monitor photodiode provided in the package of the light source 10 as the photodetector 20, the beam splitter 12 required in the configuration of the first embodiment as shown in FIG. In addition, it is not necessary to prepare the photodetector 20 separately and perform optical axis alignment. Therefore, it is possible to greatly simplify the configuration of the object detection device.

  The operation (object detection method) of the object detection apparatus according to the fifth embodiment is the same as that of the first embodiment. That is, the laser light emitted from the light source 10 is collimated into parallel light by the lens 11 and emitted far away. On the other hand, the rear monitor photodiode provided in the package of the light source 10 is used as the light detector 20 to detect the amount of laser light emitted from the light source 10. Then, the electric signal from the photodetector 20 is amplified by an amplifier, and the signal is monitored as sound by an acoustic device, for example.

  At this time, if there is a vibration scatterer (for example, paper that is not a mirror surface) in the optical path (detection optical path) of the laser light emitted from the light source 10, incoherent light of the scatterer returns to the light source 10 as return light. Come. Then, the influence of the light source 10 due to the return light is captured by the photodetector 20 which is a photodiode for rear monitoring, PS is generated, and the detector 30 determines the presence or absence of an object.

  Although not shown, in the object detection device of the fifth embodiment, as in the first embodiment, the lens 11 is a condensing type so that an object at a specific distance can be detected with high sensitivity. The focal position of the lens 11 may be adjusted by a lens driving unit. Further, the adjustment of the focal position may be feedback-controlled by the control unit so that the detection value of the photodetector 20 is maximized, or the focal position of the lens 11 is calculated from the feedback control signal, You may make it detect the distance to an object.

<Sixth Embodiment>
FIG. 7 is a schematic diagram for explaining the sixth embodiment of the present embodiment. This object detection device is characterized in that a beam splitter 12 composed of a half mirror is integrally attached to the light capturing surface of the photodetector 20. In FIG. 7, only the light source 10, the lens 11, and the photodetector 20 (including the beam splitter 12 attached integrally) are shown, but the other configurations are the same as those shown in FIG. 1.

  As described above, since the beam splitter 12 is integrally attached to the photodetector 20, it is not necessary to prepare the photodetector 20 and the beam splitter 12 separately and align the optical axes, thereby simplifying the apparatus and Cost can be reduced. In addition, there is an advantage that the detection optical path can be freely set only by changing the mounting angle of the photodetector 20.

  The operation (object detection method) of the object detection apparatus according to the sixth embodiment is the same as that of the first embodiment. That is, the laser light emitted from the light source 10 is collimated into parallel light by the lens 11 and emitted far away. At this time, the optical path is branched into two by the beam splitter 12 provided integrally with the optical detector 20, and one is put into the optical detector 20 without surface scattering (PD optical path). Then, the electric signal from the photodetector 20 is amplified by an amplifier, and the signal is monitored as sound by an acoustic device, for example.

  At this time, if there is a vibration scatterer (for example, paper that is not a mirror surface) in the detection optical path branched by the beam splitter 12, incoherent light of the scatterer returns to the light source 10 as return light. Then, the influence of the light source 10 due to the return light is captured by the photodetector 20, PS is generated, and the presence or absence of an object is determined by the detector.

  Although not shown, in the object detection device of the sixth embodiment, as in the first embodiment, the lens 11 is a condensing type so that an object at a specific distance can be detected with high sensitivity. The focal position of the lens 11 may be adjusted by a lens driving unit. Further, the adjustment of the focal position may be feedback-controlled by the control unit so that the detection value of the photodetector 20 is maximized, or the focal position of the lens 11 is calculated from the feedback control signal, You may make it detect the distance to an object.

  In the object detection apparatus according to each of the embodiments described above, a semiconductor laser is used as the light source 10, and this semiconductor laser emits a multimode laser beam in addition to a single mode laser beam. Is applicable. Further, when the semiconductor laser is used as the light source 10, when used in the mode hop state, the PS due to the return light from the object becomes stronger than when the mode hop is not performed, and the object can be detected with higher accuracy. . Here, the mode hop state is a state in which mode hopping is performed with respect to the oscillation mode (state in which mode hopping is not performed) that is closest to the laser light oscillation threshold of the semiconductor laser that is the light source 10, and the amount of current supplied to the semiconductor laser. It is possible to enter a mode hop state by, for example.

<Effect of embodiment>
In the object detection apparatus and the object detection method according to the present embodiment, it is possible to detect the return light with a scattered light level from a very weak distance (the return light level is 0.01% or less). Thus, it becomes possible to detect an object with high precision by utilizing the clear reaction to a very weak return light level. This phenomenon is qualitatively different from return light noise, which has been a problem at a level exceeding 0.01%. The generated “noise” is in the acoustic frequency range (several kHz) and the signal (PS) is clear, so that the object can be detected with a simple configuration and at low cost.

Further, since the apparatus configuration can be made very simple, the following advantages are obtained.
(1) Since a light receiver can be configured on the light source side, it is possible to commercialize a single box set.
(2) Since installation can be insensitive to the optical path, no special accuracy is required.
(3) By appropriately arranging mirrors and beam splitters, sensing in a wide range is possible, and it is possible to apply to regions and fields that have been difficult to apply in conventional light detection.
(4) The presence of the target object can be detected by installing the object detection device of the present embodiment on the moving body. For this reason, it can be used as a vehicle collision prevention or robot sensor.
(5) Since the optical output can be used even at 1 mW or less, it can be used in a very easy area in terms of laser safety standards.
(6) If a VCSEL or the like is used as the light source, it can be used with low power and long life, and can be constantly monitored.
(7) By extracting vibration features such as voiceprints, it is possible to connect to personal authentication and the like.
(8) Audio can be captured by scattering on ground glass or curtains.
(9) By hitting the human body, it can be used for medical examinations.

It is a mimetic diagram explaining a 1st embodiment of the present invention. It is a schematic diagram which shows the example provided with the structure which can adjust the focus position of a lens. It is a schematic diagram explaining 2nd Embodiment of this invention. It is a schematic diagram explaining 3rd Embodiment of this invention. It is a schematic diagram explaining 4th Embodiment of this embodiment. It is a schematic diagram explaining 5th Embodiment of this embodiment. It is a schematic diagram explaining 6th Embodiment of this embodiment. It is a schematic diagram explaining a conventional optical sensor.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Light source, 11 ... Lens, 12 ... Beam splitter, 13 ... ND filter, 20 ... Photo detector, 21 ... Amplifier, 22 ... Filter, 30 ... Detector, 120 ... Mirror, 121 ... Beam splitter

Claims (18)

A light source that emits laser light;
A light receiving means for detecting an output change of the light source due to incoherent light among scattered light generated when the laser light emitted from the light source hits an object;
An object detection apparatus comprising: detection means for detecting the presence or absence of an object to be detected based on a detection result by the light receiving means. A lens for condensing laser light emitted from the light source;
Driving means for adjusting the focal position of the lens;
The object detection apparatus according to claim 1, further comprising: a control unit that adjusts a focal position of the lens by the driving unit and controls so that a detection value by the light receiving unit is maximized. The said detection means detects the distance to the said object based on the focal distance of the said lens at the time of control which the detection value by the said light-receiving means performed by the said control means becomes the maximum. Object detection device. The object detection apparatus according to claim 1, wherein the light source emits multimode laser light. The object detection apparatus according to claim 1, wherein the light source emits laser light in an oscillation mode that is mode-hopped from an oscillation mode that is closest to an oscillation threshold value of the laser light. The object detection apparatus according to claim 2, wherein the light source emits multimode laser light. The object detection device according to claim 2, wherein the light source emits laser light in an oscillation mode that is mode-hopped from an oscillation mode that is closest to an oscillation threshold value of laser light. The object detection apparatus according to claim 1, further comprising a reflection unit configured to reflect laser light emitted from the light source. The object detection apparatus according to claim 1, further comprising a branching unit that branches the laser light emitted from the light source. In an object detection method using a laser light emitting device comprising: a light source that emits laser light; and a light receiving unit that detects an output change of the laser light emitted from the light source.
The light receiving means detects an output change of the light source due to incoherent light among scattered light generated when the laser light emitted from the light source strikes an object, and the presence or absence of an object to be detected based on the detection result The object detection method characterized by detecting. 11. The object detection method according to claim 10, wherein a focal length of a lens that collects laser light emitted from the light source is adjusted, and control is performed so that a detection value by the light receiving unit is maximized. The object detection method according to claim 11, wherein a distance to the object is detected based on a focal length of the lens when control is performed so that a detection value by the light receiving unit is maximized. The object detection method according to claim 10, wherein multimode laser light is emitted from the light source. 11. The object detection method according to claim 10, wherein the laser light emitted from the light source is emitted in an oscillation mode that is mode-hopped from an oscillation mode closest to an oscillation threshold of the laser light. The object detection method according to claim 11, wherein multimode laser light is emitted from the light source. The object detection method according to claim 11, wherein the laser beam emitted from the light source is emitted in an oscillation mode that is mode-hopped from an oscillation mode closest to an oscillation threshold of the laser beam. The object detection method according to claim 10, wherein the laser beam emitted from the light source is reflected by a reflection unit, and an object on an optical path including a path due to the reflection is detected. The object detection method according to claim 10, wherein the laser light emitted from the light source is branched by a branching unit, and objects on a plurality of optical paths are detected by the branching.

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