JP2007171087A - Light-emitting/receiving device and object-detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the attenuation of light due to sunlight and water, and to appropriately receive the light-emitted from a light-emitting section and reflected by an object by a light-receiving section. <P>SOLUTION: A light-emitting/receiving device 2 comprises the light-emitting section 3 for emitting a light toward space in which an object X exists and the light-receiving section 4 for receiving reflected light, when the light emitted from the light-emitting section 3 is reflected by the object X. The wavelength of the light emitted from the light-emitting section 3 is selected so that the amount of light received by the light-receiving section 4 of object direct-reflected light, which emitted from the light-emitting section 3, is directly made incident on the object X is reflected by the object X, and is directly received by the light-receiving section 4, becomes relatively larger, to the extent that the object direct reflected light and sunlight received by the light-receiving section 4 can be discriminated and that the amount of light received by the light-receiving section 4 of object water transmission reflected light, which emitted from the light-emitting section 3 is made incident on the object X is reflected by the object X, and is received by the light-receiving section 4, when water is present in an optical path leading to the light receiving section 4, becomes relatively larger, to the extent that the object water transmission reflected light and the object direct reflected light are decided as being of the same kind. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improved technique for a light projecting / receiving device that emits light to an object from a light projecting unit and receives light reflected from the object by a light receiving unit.

  As is well known, for example, an object detection device that is mounted on an automated guided vehicle (AGV) or the like and detects an object such as an obstacle in a traveling region detects the presence or absence of an object using light projection and reception. The one configured in the above is widely used.

  In general, this type of object detection device incorporates a light projecting / receiving device in order to perform light projecting / receiving, as described above. Such a light projecting / receiving device includes a light projecting unit that emits light into a space where an object exists, and a light receiving unit that receives light reflected from the object when the light emitted from the light projecting unit enters the object. Are commonly used (see, for example, Patent Document 1 below).

JP 2005-55226 A

  By the way, in recent years, this type of object detection apparatus is often used outdoors, and it has been required to accurately detect an object to be detected even outdoors.

  However, when the light projecting / receiving device as disclosed in Patent Document 1 is used outdoors, the light received by the light receiving unit is other than the light emitted from the light projecting unit and reflected by the object, Sunlight is received by the light receiving unit. In such a case, it is impossible to identify whether the light received by the light receiving unit is due to the light emitted from the light projecting unit and reflected by the object, or due to sunlight, For example, even when there is no object, there is a possibility of erroneous detection that the object is present when sunlight is received by the light receiving unit.

  Furthermore, on the optical path from the light projecting part to the light receiving part through the object, such as when the surface of the object to be detected is wet due to the influence of rain, etc. Water may be involved. However, in such a case, when the light projecting / receiving device as disclosed in the above-mentioned Patent Document 1 is used, the light emitted from the light projecting unit is attenuated by passing through the water intervening on the optical path. The amount of light becomes weak when it is received by the unit, and even if an object is present, there is a risk of erroneous detection that the object is not present.

  An object of the present invention is to reduce the influence of receiving sunlight and the influence of light attenuation by water, and accurately receive the light emitted from the light projecting section and reflected by the object by the light receiving section. There is.

  The present invention, which was created to solve the above-described problems, includes a light projecting unit that emits light into a space where an object exists, and the light emitted from the light projecting unit is reflected by the object when the light enters the object. In a light projecting / receiving device including a light receiving unit that receives the reflected light, the light emitted from the light projecting unit is directly incident on the object, reflected by the object, and directly received by the light receiving unit. Until the reflected light and the sunlight received by the light receiving unit can be distinguished, the amount of light received by the light receiving unit of the object direct reflected light is relatively large and emitted from the light projecting unit. Object water passing reflected light received by the light receiving unit and light directly reflected by the object when light is incident on the object and water is present on the optical path from the object reflected to the light receiving unit. And the object water passing reflection until it can be judged as the same kind Wherein as the amount of light received by the light receiving portion is relatively large, characterized in that selects the wavelength of light emitted from the light projecting unit.

  According to the above configuration, only by selecting the light emitted from the light projecting unit, the object direct reflected light and the sunlight are identified, and the object direct reflected light and the water passing reflected light are determined to be the same type. It becomes possible. Therefore, it is possible to accurately receive the reflected light from the object while reducing the influence of sunlight, and water is present on the optical path from the light projecting unit through the object to the light receiving unit. However, the attenuation of the light emitted from the light projecting unit is reduced as much as possible by such water, and it becomes possible to make the light having a sufficient amount of light incident on the light receiving unit.

  In the above configuration, it is preferable that the light receiving unit is configured to selectively receive light in the same wavelength band as the light emitted from the light projecting unit.

  In this way, the proportion of sunlight incident on the light receiving unit is more accurately reduced, and more stable light projecting and receiving can be realized.

  The above configuration may further include a scanning unit that scans light emitted from the light projecting unit into a space where the object exists.

  In this way, the area irradiated with the light emitted from the light projecting unit is enlarged, and the light can be incident on the object more accurately.

  The light detection device configured as described above may further include a detection unit that detects the object based on the light received by the light reception unit, thereby configuring the object detection device.

  In this way, the influence of both sunlight and water intervening on the optical path from the light projecting unit through the object to the light receiving unit is reduced, and the object to be detected is accurately detected without being erroneously detected. Can be detected.

  According to the present invention as described above, the object direct reflected light and the sunlight are discriminated by only selecting the light emitted from the light projecting unit, and the object direct reflected light and the water passing reflected light are of the same type. As a result, light can be projected and received stably.

  Hereinafter, an object detection apparatus according to a first embodiment of the present invention will be described with reference to FIG.

  FIG. 1 illustrates a schematic configuration of a device under test detection apparatus according to the present embodiment. As shown in the figure, the object detection device 1 includes a light projecting / receiving device 2 as a main component. The light projecting / receiving device 2 includes a light projecting unit 3 that emits light to a space in which the object X exists, and reflected light that is reflected by the object X when the light emitted from the light projecting unit 3 enters the object X. And a light receiving unit 4 for receiving light. In the figure, reference numeral 5 denotes an optical lens that makes the beam diameter of the light emitted from the light projecting unit 3 constant, and reference numeral 6 denotes an optical lens that focuses the light reflected by the object X onto the light receiving unit 4.

  The light projecting unit 3 uses, for example, a laser light emitting diode or a semiconductor laser as a light source. The wavelength of the light emitted from the light projecting unit 3 is such that the light emitted from the light projecting unit 3 is directly incident on the object, reflected by the object X, and directly received by the light receiving unit 4. Until the light received by the light receiving unit 4 can be discriminated from the light received by the light receiving unit 4 of the directly reflected light of the object, and the light emitted from the light projecting unit 3 is the object. The object water passing reflected light received by the light receiving unit 4 and the object direct reflected light are of the same type when incident on X and water is present on the optical path from the object X to the light receiving unit 4 after being reflected by the object X The light receiving amount of the object water passing reflected light at the light receiving unit 4 is selected to be relatively large until it can be determined. Here, “the object water passing reflected light and the object direct reflected light can be determined to be the same type” means that the amount of light received when the object water passing reflected light is received by the light receiving unit 4 and the object direct reflected light. Means that the amount of light received when the light is received by the light receiving unit 4 is substantially the same.

Specifically, the intensity of sunlight has a distribution in intensity depending on the wavelength component of light contained in sunlight. Electromagnetic waves including visible light emitted from the sun are partially attenuated by components in the atmosphere and reach the ground. The wavelength characteristics of the intensity of sunlight on the ground are shown in FIG. As shown in the figure, the intensity of sunlight is the strongest in the wavelength region of visible light, and gradually decreases as the wavelength increases. In FIG. 2, the intensity of the wavelength at which a chemical component such as H ₂ O is displayed indicates that the intensity of sunlight is attenuated by the chemical component in the atmosphere. Furthermore, the intensity of sunlight has intermittent wavelength components that locally weaken as the wavelength increases. More specifically, typical values of wavelengths at which dips where the intensity of sunlight is weakened are about 0.8 μm, 0.95 μm, 1.12 μm, 1.34 μm to 1.46 μm, 1 .8 μm to 1.96 μm can be mentioned, and the wavelength within this range is emitted from the light projecting unit 3, and the light projecting wavelength is selectively received by the light receiving unit 4. It becomes small, and it becomes possible to distinguish between the object directly reflected light received by the light receiving unit 4 and sunlight.

  On the other hand, the absorption coefficient of light with respect to water also varies significantly depending on the wavelength of light. The wavelength characteristic of the absorption coefficient of light with respect to water is shown in FIG. As shown in the figure, the absorption coefficient of light with respect to water tends to gradually increase as the wavelength of light increases. Therefore, as the wavelength emitted from the light projecting unit 3 becomes shorter, the attenuation of light due to water absorption is reduced, and the direct reflected light of the object and the reflected light irradiated to the object through the water are of the same type. It becomes possible to judge.

  However, when the absorption coefficient of water is taken into consideration, the amount of light attenuation due to water absorption decreases as the wavelength of light emitted from the light projecting unit 3 becomes shorter. The intensity becomes strong, and it becomes difficult to distinguish between the object directly reflected light and sunlight. Therefore, the wavelength emitted from the light projecting unit 3 is particularly the wavelength in the wavelength range in which the intensity of the sunlight is weakened in consideration of both the wavelength characteristic of the sunlight intensity and the wavelength characteristic of the water absorption coefficient. It is necessary to select a short region. Specifically, the wavelength of light emitted from the light projecting unit is set to 0.795 μm to 0.805 μm (preferably 0.8 μm), 0.94 μm to 0.96 μm (preferably 0.95 μm), or 1. If it selects in 10 micrometers-1.14 micrometers (preferably 1.12 micrometers), it will become possible to implement | achieve stable light projection / reception, reducing the influence of absorption to sunlight and water.

  The light receiving unit 4 is composed of an optical sensor such as a photodiode. Furthermore, in the present embodiment, the optical filter 7 that selectively transmits light in the same wavelength band as the light emitted from the light projecting unit 3 on the optical path where the light reflected by the object X reaches the light receiving unit 4. It arrange | positions and the ratio which sunlight injects into the light-receiving part 4 is reduced.

  Furthermore, the object detection device 1 includes a detection unit 8. The detection unit 8 is connected to the light projecting unit 3 through the signal line 9 and is connected to the light receiving unit 4 through the signal line 10, and the light emitted from the light projecting unit 3 and the light receiving unit The object X is detected by calculating the distance to the object X based on the light received at 4 and detecting the distance to the object X. In addition, as a calculation method of the distance in the detection unit 8, for example, the intensity of light is modulated in a pulse shape, and the time difference between the light emitted from the light projecting unit 3 and the light received by the light receiving unit 4 is calculated. The TOF method for obtaining the distance, the AM signal intensity modulated at a certain frequency, and the modulation signal component of the light emitted from the light projecting unit 3 and the modulation signal component of the light received by the light receiving unit 4 An AM method for obtaining a distance from the phase difference can be applied.

  As described above, according to the object detection device 1 according to the present embodiment, the object direct reflection light and the sunlight are identified and the object direct reflection light is selected only by selecting the light emitted from the light projecting unit 3. And the water passing reflected light can be determined to be of the same type, and the influence of both sunlight and water intervening on the optical path from the light projecting unit 3 through the object X to the light receiving unit 4 can be reduced. However, it is possible to accurately detect the object X to be detected without erroneous detection.

  An object detection apparatus according to a second embodiment of the present invention will be described with reference to FIG. The second embodiment includes the same detection unit as that of the first embodiment. The second embodiment is different from the first embodiment in the structure of the light projecting / receiving device incorporated in the object detection device, and in particular, the scanning unit that scans the light emitted from the light projecting unit into the space where the object exists. Is in place. Below, it demonstrates centering on the light projection / reception apparatus integrated in the object detection apparatus which concerns on 2nd embodiment. In FIG. 4, constituent elements common to the first embodiment are denoted by the same reference numerals.

  FIG. 4 illustrates a schematic configuration of the object detection apparatus according to the second embodiment. As shown in the figure, the scanning unit 22 of the light projecting / receiving device 21 incorporated in the object detection device 20 has a rotating shaft 23a on one shaft 24a and a motor 24 having both shafts projecting common rotating shafts 23a and 23b on the top and bottom. And a light receiving mirror 26 attached to the other rotating shaft 23b in the same phase. Then, the light emitted from the light projecting unit 3 is reflected by the light projecting mirror 25 to scan the space where the object X exists, and the reflected light reflected by the object X is reflected by the light receiving mirror 26 to the light receiving unit 4. Incident. Therefore, since light is scanned in the space where the object exists, the object X can be more accurately irradiated with the light emitted from the light projecting unit 3. Although not shown in the figure, by configuring the rotational position information of the motor 24 to be input to the detection unit 8, the detection unit 8 can calculate the calculation distance to the object X and the input rotational position information of the motor 24. In combination, the position of the object X in the scanning region may be detected.

As described above, according to the object detection device 20 according to the second embodiment, just by selecting the light emitted from the light projecting unit 3 as in the first embodiment, the object direct reflected light and the sun are selected. In addition to discriminating light, it is possible to determine that the object direct reflected light and the water passing reflected light are of the same type, and the sunlight and the light path from the light projecting unit 3 through the object X to the light receiving unit 4 It is possible to accurately detect the object X to be detected without erroneous detection while reducing the influence of both of the intervening water. In addition, since the light emitted from the light projecting unit 3 is scanned in the space where the object X exists by the light projecting mirror 25, the detectable range of the object X can be expanded.

  An object detection apparatus according to a third embodiment of the present invention will be described with reference to FIG. Similarly to the second embodiment, the third embodiment also has a scanning unit in the light projecting / receiving device. The third embodiment differs from the second embodiment in that a half mirror is provided in the light projecting / receiving device. Thus, by sharing a part of the light path between the light projecting unit and the light receiving unit, the light projecting mirror also serves as the light receiving mirror. Below, it demonstrates centering around the light projection / reception apparatus integrated in the object detection apparatus which concerns on 3rd embodiment. In FIG. 5, constituent elements common to the first embodiment and the second embodiment are denoted by the same reference numerals.

  FIG. 5 illustrates a schematic configuration of an object detection device according to the third embodiment of the present invention. As shown in the figure, the scanning unit 32 of the light projecting / receiving device 31 incorporated in the object detection device 30 is configured by attaching a light projecting mirror 25 to a rotating shaft 34 projecting downward from a motor 33. Then, the light emitted from the light projecting unit 3 is reflected upward by the half mirror 35, reflected by the light projecting mirror 25 and scanned in the space where the object X exists, and the reflected light reflected by the object X is reflected. The light is reflected again by the light projection mirror 25, passes through the half mirror 35, and enters the light receiving unit 4.

  As described above, according to the object detection device 30 according to the third embodiment, it is possible to obtain the same functions and effects as those of the second embodiment described above.

It is the schematic which shows the object detection apparatus which concerns on 1st embodiment of this invention. It is a figure which shows the wavelength characteristic of the intensity | strength of sunlight. It is a figure which shows the wavelength characteristic of the absorption coefficient of water. It is the schematic which shows the object detection apparatus which concerns on 2nd embodiment of this invention. It is the schematic which shows the object detection apparatus which concerns on 3rd embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Object detection apparatus 2 Light projection / reception apparatus 3 Light projection part 4 Light reception part 7 Optical filter 8 Detection part X Object

Claims (4)

A light projecting / receiving unit that includes a light projecting unit that emits light into a space where an object exists and a light receiving unit that receives reflected light reflected by the object when the light emitted from the light projecting unit is incident on the object. In the device
The light directly emitted from the light projecting unit is directly incident on the object, reflected by the object and directly received by the light receiving unit, and sunlight received by the light receiving unit can be distinguished. The amount of light received by the light receiving part of the object directly reflected light is relatively large until
The object water received by the light receiving unit when light emitted from the light projecting unit is incident on the object and water is present on the optical path from the object reflected to the light receiving unit. The amount of light received by the light receiving unit of the object water passing reflected light is relatively large until it can be determined that the passing reflected light and the object direct reflected light are the same type.
The light projecting / receiving device, wherein a wavelength of light emitted from the light projecting unit is selected.   The light projecting / receiving device according to claim 1, wherein the light receiving unit is configured to selectively receive light in the same wavelength band as the light emitted from the light projecting unit.   The light projecting / receiving device according to claim 1, further comprising a scanning unit that scans light emitted from the light projecting unit into a space where the object exists.   The object detection apparatus according to claim 1, further comprising a detection unit that detects the object based on light received by the light reception unit.

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