JP2006258802A - Light receiving device and range finder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light receiving device which can receive a light wave over a wide range. <P>SOLUTION: The light receiving device comprises a light receiving element 3, a lens 2 which concentrates the reflecting light 12, 13 into the light receiving element 3. A lens 2 includes at least three or more sections which are different in the focal lengths. The lens 2 includes at least three or more sections which are different in the focal lengths, so impinging of a stable light amount into the light receiving element 3 can be carried out over the wide range. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wave receiving device that receives waves such as light, electromagnetic waves, and sound waves, and a distance measuring device using such a wave receiving device.

  The distance measuring device emits light, electromagnetic waves, sound waves, etc. toward the object to be measured, receives the wave reflected by the object to be measured, and calculates the distance based on the phase difference between the emitted wave and the received wave. Measuring.

  As a photoelectron detection device used in a laser distance measuring device, for example, in US Pat. No. 6,759,649, as shown in FIG. 6, a light receiving element 101, a lens 102 for condensing light on the light receiving element 101, and a center of the lens 102 A laser diode 103 disposed in the vicinity of the lens, a lens 104 that is attached to the center of the lens 102 and that collimates the light emitted from the laser diode 103, and an inclined mirror 105 disposed in front of the lens 104. An apparatus is disclosed.

The light emitted from the laser diode 103 becomes parallel light 106 when passing through the lens 102, and irradiates a distance measuring object (not shown) via the tilt mirror 105. The light 107 reflected by the distance measuring object passes through the tilt mirror 105 and is collected by the lens 102 and enters the light receiving element 101. In the distance measurement, based on the phase difference between the light projection signal 108 inputted and driven by the laser diode 103 and the light reception signal 109 converted by the light receiving element 101, the time from light emission to light reception is obtained. The distance to the object to be measured may be calculated by multiplying time by the speed of light.
US Pat. No. 6,759,649

  In such a distance measuring apparatus, when the distance from the lens 102 to the object to be measured is sufficiently long, as shown in FIG. 6, the light 107 reflected by the object to be measured becomes substantially parallel light. The light enters the lens 102, is condensed by a predetermined focal length of the lens 102, and enters the light receiving element 101. However, when the distance from the lens 102 to the object to be measured becomes short, the light 107 reflected by the object to be measured enters the lens 102 while spreading as shown in FIG. When the light reflected by the distance measuring object is incident on the lens 102 while spreading, the focus of the light passing through the lens 102 is shifted to a position farther than the light receiving element 101 as shown in FIG.

  Moreover, in the use of such a distance measuring device, a retro reflector (regressive reflection plate) may be used as a reflection plate for laser light of a distance measurement object. As shown in FIG. 8, the retroreflector (regressive reflector) generally has a higher reflectivity as the observation angle is closer to 0, and the reflectivity decreases as the observation angle increases. When such a retroreflector (regressive reflection plate) is used, the distance from the lens 102 to the object to be measured becomes short, and the light reflected by the object to be measured is incident on the lens 102 while spreading. As shown in FIG. 4, light having low reflectance is incident on the outer diameter side portion of the lens 102 and the focal point is shifted from the light receiving element 101, so that the light hardly enters the light receiving element 101. Further, the light passing through the vicinity of the central portion of the lens 102 is blocked by the lens 104 disposed in the vicinity of the central portion of the lens 102 and cannot enter the light receiving element 101. As a result, as shown in FIG. 9, when the distance of the object to be measured becomes closer than a certain distance, a situation where a sufficient amount of light does not enter the light receiving element 101 occurs.

  As described above, in the configuration in which the lens 104 and the laser diode 103 are disposed in the central portion of the lens 102 for condensing the light to the light receiving element 101 and in the vicinity of the central portion, the distance to the distance measuring object is closer than a predetermined distance. If so, there may be a situation in which distance measurement cannot be performed. It is considered that the same phenomenon can occur not only when laser light or the like is used but also when various waves such as electromagnetic waves or sound waves are used.

  In view of such a problem, the present invention receives a wave that is incident on a wave receiving means in a wide range when there is an obstacle that obstructs the progression of the wave in the central part of the lens that aggregates the wave or in the vicinity of the central part. A device is provided.

  The wave receiving apparatus according to the present invention includes a wave receiving unit that receives a wave and a lens that collects the wave toward the wave receiving unit, and the lens includes at least three portions having different focal lengths. It is a feature.

  Further, the distance measuring device according to the present invention includes a wave receiving means for receiving a wave, a lens for concentrating the waves toward the wave receiving means, a wave emitting means for emitting a wave toward the distance measuring object, and a wave emitting means. The distance measurement object is based on the wave emitted from the wave and the elapsed time until the wave is emitted from the wave emission means, and the emitted wave is reflected by the distance measurement object and received by the wave reception means via the lens. Distance deriving means for deriving the distance to the lens, and the lens is characterized by comprising at least three portions having different focal lengths. The distance deriving means may derive the distance to the distance measuring object based on, for example, the phase difference from the wave reflected by the distance measuring object and incident on the wave receiving means via the lens.

  In addition, the lens may include at least two or more portions where the parallel waves incident on the lens are collected by the wave receiving means and portions where the focal length is shorter than the portion and the focal lengths are different from each other.

  In addition, the lens is provided with a portion for concentrating the parallel wave incident on the lens in the receiving means on the outer diameter side portion of the lens, and the focal length is shorter on the inner diameter side portion of the lens than on the outer diameter side portion of the lens. It is good also as a structure provided with at least 2 or more parts from which a focal distance differs.

  According to this wave receiving apparatus, since the lens includes at least three portions having different focal lengths, waves can be incident on the wave receiving means in a wide range with respect to the distance from the wave source. For example, a portion for concentrating the parallel waves incident on the lens on the receiving means is provided on the outer diameter side portion of the lens, and the inner diameter side portion of the lens has a shorter focal length than the outer diameter side portion of the lens, and each has a focal length of In a configuration having at least two different portions, when the wave source is sufficiently far and parallel light is incident on the lens, the waves passing through the outer diameter side portion of the lens are concentrated on the receiving means. be able to. Also, when the wave source approaches and the focal point of the wave incident on the outer diameter side portion of the lens shifts away from the wave receiving means, the inner diameter side portion of the lens whose focal length is shorter than the outer diameter side portion of the lens Waves that have passed through can be concentrated in the receiving means. Further, since the inner diameter side portion of the lens has at least two portions having different focal lengths, the range in which the waves can be collected by the wave receiving means is wide. In addition, this wave receiving device stably collects waves in the wave receiving means even when there are obstacles that obstruct the wave progression in the central part of the lens and in the vicinity of the central part of the lens. Can be made.

  In addition, the distance measuring device according to the present invention has the configuration of the above-described wave receiving device, and can measure the distance to the distance measuring object in a wider range. For example, a portion for concentrating the parallel waves incident on the lens on the receiving means is provided on the outer diameter side portion of the lens, and the inner diameter side portion of the lens has a shorter focal length than the outer diameter side portion of the lens, and each has a focal length of In the structure having at least two different portions, when the distance to the object to be measured is close and the reflected wave is incident on the lens while spreading, the wave incident on the inner diameter side portion of the lens is The reflectance is higher than that of the wave incident on the outer diameter side portion. In this distance measuring device, when the distance to the object to be measured becomes close and the reflected wave is incident on the lens while spreading, the wave passing through the inner diameter side portion of the lens is incident on the wave receiving means. . This makes it possible to obtain the information necessary for distance measurement from the wave incident on the wave receiving means even when the distance to the distance measurement object is short, and to measure the distance to the distance measurement object in a wider range. Can do.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of a wave receiving device and a distance measuring device according to the invention will be described with reference to the drawings.

  This distance measuring device 10 measures the distance to a distance measuring object using a laser beam. As shown in FIG. 1, a projector 1 as a wave emitting means, a lens 2, and a wave receiving means. The light receiving element 3 and the distance deriving means 4 are provided. In FIG. 1, reference numeral 5 denotes a reflector as a distance measuring object. In this embodiment, the lens 2 and the light receiving element 3 constitute a wave receiving device. The light receiving element 3 is disposed at a position away from the lens 2 by a predetermined distance on the central axis of the lens 2. The projector 1 is disposed near the center of the lens 2 between the lens 2 and the light receiving element 3.

  The projector 1 includes a laser diode 6 and a lens 7. In this embodiment, the laser diode 6 receives a predetermined input signal corresponding to the laser light to be oscillated, and oscillates the laser light adjusted to an amplitude corresponding to the input signal. The light emitted from the laser diode 6 passes through the lens 7 to become parallel light 11, passes through the lens 2, and is emitted to the reflecting plate 5 that is a distance measuring object. In this embodiment, although not shown, the light emitted from the laser diode 6 is received and photoelectrically converted by the light receiving element provided to the laser diode 6 via an optical fiber, so that the laser diode 6 A projection signal 11a of the emitted light 11 is obtained.

  The lens 2 collects the light 12 and 13 reflected by the reflecting plate 5 toward the light receiving element 3, and includes at least three portions having different focal lengths. In this embodiment, as shown in FIG. 2, the lens 2 includes a transmission portion 16 that transmits light emitted from the projector 1 at the center. As shown in FIG. 3, the outer diameter side portion 17 of the lens 2 is formed with a predetermined focal length that causes the incident parallel light 14 to be concentrated on the light receiving element 3. The inner diameter side portion 18 of the lens 2 is formed by concentrically forming a plurality of portions having a shorter focal length than the outer diameter side portion 17 of the lens 2, and the focal length is gradually reduced from the outside toward the inside. ing.

  Since the focal length of the inner diameter side portion 18 of the lens 2 is gradually reduced from the outside toward the inside, the distance of the reflecting plate 5 becomes close as shown in FIG. When incident, the light 12 that has passed through the outer diameter side portion 17 of the lens 2 does not enter the light receiving element 3, but the light 13 that has passed through the inner diameter side portion 18 of the lens 2 enters the light receiving element 3. Further, when a retroreflector (regressive reflection plate) is used for the reflecting plate 5, the light 13 incident on the inner diameter side portion 18 of the lens 2 is changed to the light 12 incident on the outer diameter side portion 17 of the lens 2. The reflectance is higher than that (see FIG. 13). If this lens 2 is used, as shown in FIG. 4, the light 13 incident on the inner diameter side portion 18 of the lens 2 can be incident on the light receiving element 3 even when the distance from the reflector 5 is short. Even when a retroreflector (regressive reflection plate) is used for the reflection plate 5, the reflectance of light incident on the light receiving element 3 does not decrease, and a stable amount of light can be incident on the light receiving element 3.

  When receiving light, the light receiving element 3 is an element that photoelectrically converts the received light and outputs a light reception signal.

  The distance deriving unit 4 emits a wave from the wave emitting unit 1, and the emitted wave is reflected by the distance measuring object 5 and is received by the wave receiving unit 3 through the lens 2. The distance to the distance measuring object 5 is derived. Such elapsed time can be calculated based on the phase difference between the wave emitted from the wave emitting means 1 and the wave reflected by the distance measuring object 5 and incident on the wave receiving means 3 via the lens 2. . In this embodiment, the distance deriving means 4 derives the distance to the distance measuring object 5 based on the phase difference from the wave reflected by the distance measuring object 5 and incident on the wave receiving means 3 via the lens 2. is doing. Specifically, the distance deriving unit 4 includes the light 11 emitted from the laser diode 6 based on the light projection signal 1 a of the light 11 emitted from the laser diode 6 and the light reception signal 3 a output from the light receiving element 3. Then, the phase difference of the light 12 (13) reflected by the reflecting plate 5 and incident on the light receiving element 3 is obtained, and the time until the light 11 irradiated by the laser diode 6 enters the light receiving element 3 is calculated. And the distance to the reflecting plate 5 is calculated | required by multiplying this with the speed of light.

  In the distance measuring device 10, when the distance to the reflecting plate 5 is sufficiently long, reflected light 14 that is substantially parallel to the lens 2 is incident on the lens 2 and passes through the outer diameter side portion 17 of the lens 2, as shown in FIG. The incident light enters the light receiving element 3. Further, since the focal length of the inner diameter side portion 18 of the lens 2 for concentrating the light on the light receiving element 3 is gradually reduced from the outside toward the inside, the distance of the reflecting plate 5 becomes close and the reflected light spreads. When the light enters the lens 2, the light 13 that has passed through the inner diameter side portion 18 of the lens 2 gradually enters the light receiving element 3 as shown in FIG. 1. As a result, even when the distance to the reflecting plate 5 is short, information necessary for distance measurement can be obtained from the light incident on the light receiving element 3. As described above, it is possible to provide a distance measuring device in which a stable amount of light can be incident on the light receiving element 3 in a wide range and a range in which the distance can be measured is wide. Further, by using such a wave receiving device, the projector 1 can be disposed in the vicinity of the center portion of the lens 2, so that the distance measuring device can be made compact.

  As mentioned above, although one Embodiment of the wave receiving device and distance measuring device which concern on this invention was described based on drawing, the wave receiving device and distance measuring device which concern on this invention are not limited to this.

  For example, in the above-described embodiment, the inner diameter side portion of the lens has a plurality of concentrically arranged portions having a shorter focal length than the outer diameter side portion of the lens, and the focal length is gradually reduced from the outside toward the inside. However, the lens is not limited to this as long as the lens has at least three portions having different focal lengths. For example, the inner diameter side portion of the lens may be divided into a plurality of sectors, and the focal length may be made different so that the focal length is gradually reduced.

  As shown in FIG. 5, the lens 31 is provided with a portion having a different focal length in the inner diameter side portion 32 of the lens 31, and in the boundary region of the portion having a different focal length of the inner diameter side portion 32 of the lens 31, The focal length is gradually reduced as it goes to make the focal length smooth and continuous. In addition, since this lens 31 has substantially no boundary at a portion where the focal length is different, the amount of light incident on the light receiving element can be stabilized. Moreover, although what has arrange | positioned the light projector in the center part vicinity of the lens was illustrated, it is not limited to this.

  Further, the laser distance measuring device using laser light is exemplified as the distance measuring device. However, the wave receiving device and the distance measuring device according to the present invention are not limited to the case of using light such as laser light, but also electromagnetic waves and sound waves. It is applicable when using various waves such as.

  For example, when using a very high frequency radio wave called a microwave, a dielectric lens that can control the traveling direction of the radio wave in the same manner as a lens in light may be used instead of the optical lens in the above embodiment. . The dielectric lens refracts radio waves in the dielectric lens due to a difference in dielectric constant. Due to this known phenomenon, the present invention can be applied to electromagnetic waves by using dielectric lenses having partially different focal lengths. Further, a microwave transmitter can be used instead of the projector as the wave emitting means, and a microwave receiver can be used instead of the light receiving element as the wave receiving means.

  The present invention is also applicable to the case of using sound waves generated by air vibration. In this case, an acoustic lens that can control the traveling direction of the sound wave in the same manner as the lens in the light may be used instead of the optical lens in the above embodiment. For example, in the case of sound waves, the traveling speed of sound waves changes in the same manner as described above due to the difference in air density. That is, if there is a spatial region with a high air density, it is well known as an acoustic lens that an effect similar to that of a lens can be obtained for sound waves. Due to this well-known phenomenon, the present invention can be applied to sound waves by using acoustic lenses having partially different focal lengths. Further, a sound wave transmitter can be used in place of the projector as the wave emitting means, and a sound wave receiver can be used in place of the light receiving element as the wave receiving means.

The figure which shows the ranging apparatus which concerns on one Embodiment of this invention. 1 is a plan view showing a lens used in a wave receiving device and a distance measuring device according to an embodiment of the present invention. The figure which shows the ranging apparatus which concerns on one Embodiment of this invention. The figure which shows the relationship between the distance with the reflecting plate in the distance measuring device which concerns on one Embodiment of this invention, and the light quantity which injects into a light receiving element. Sectional drawing which shows other embodiment of the lens used for the wave receiving device and distance measuring device which concern on this invention. The figure which shows the well-known example of a photoelectron detector. The figure which shows the well-known example of a photoelectron detector. The figure which shows the relationship between an observation angle and a reflectance. The figure which shows the relationship between the distance with the reflecting plate in the conventional laser ranging apparatus, and the light quantity which injects into a light receiving element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light projector 1a Light projection signal 2 Lens 3 Light receiving element 3a Light reception signal 4 Distance derivation means 5 Reflector 6 Laser diode 7 Lens 10 Distance measuring device 11 Light emitted by laser diode 11 Parallel light 11a Light projection signals 12, 13 Reflected light 14 Parallel light 16 Transmitting portion 17 Outer diameter side portion 18 Inner diameter side portion

Claims (10)

Receiving means for receiving waves, and a lens for concentrating the waves toward the receiving means,
The wave receiving device according to claim 1, wherein the lens includes at least three portions having different focal lengths.   The lens includes a portion for concentrating parallel waves incident on the lens on the receiving means, and at least two portions having a focal length shorter than the portion and different focal lengths. Item 4. The wave receiving device according to Item 1.   The lens has a portion for concentrating parallel waves incident on the lens in the receiving means on the outer diameter side portion of the lens, the inner diameter side portion of the lens has a shorter focal length than the outer diameter side portion of the lens, The wave receiving device according to claim 2, comprising at least two portions having different distances.   The wave receiving device according to any one of claims 1 to 3, wherein a focal length of a boundary region of a portion having a different focal length on the inner diameter side of the lens is smoothly continuous. Receiving means for receiving waves,
A lens for concentrating waves toward the wave receiving means;
Wave launching means for emitting waves toward the object to be measured;
A wave is emitted from the wave emitting means, and a distance to the distance measuring object is derived based on an elapsed time until the emitted wave is reflected by the distance measuring object and received by the wave receiving means through the lens. A distance deriving means for
The lens has at least three parts having different focal lengths. Receiving means for receiving waves,
A lens for concentrating waves toward the wave receiving means;
Wave launching means for emitting waves toward the object to be measured;
Distance deriving means for deriving the distance to the distance measuring object based on the phase difference between the wave emitted from the wave emitting means and the wave reflected by the distance measuring object and entering the wave receiving means via the lens And
The lens has at least three portions having different focal lengths.   2. The lens according to claim 1, further comprising: a portion for concentrating parallel waves incident on the lens on the wave receiving means; and at least two portions having a focal length shorter than the portion and different focal lengths. Item 7. The distance measuring device according to Item 5 or 6.   The lens has a portion for concentrating parallel waves incident on the lens in the receiving means on the outer diameter side portion of the lens, the inner diameter side portion of the lens has a shorter focal length than the outer diameter side portion of the lens, The distance measuring device according to claim 5 or 6, comprising at least two portions having different distances.   9. The distance measuring device according to claim 5, wherein focal lengths of portions having different focal lengths of the lens are smoothly continuous.   9. The distance measuring device according to claim 5, wherein the wave emitting means is disposed in the vicinity of the center of the lens.

Images