Light-emitting device, light-receiving device, light-emitting and light-receiving device, light-emitting method, light-receiving method, program, and recording medium
The device addresses light saturation issues in distance measuring devices by using a reflective element with varied surface angles and reflectivities, ensuring accurate light reception from different distances.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- PIONEER IP
- Filing Date
- 2026-04-17
- Publication Date
- 2026-06-25
AI Technical Summary
The saturation of the light-receiving element due to varying intensities of reflected light from different angles of a polygon mirror in distance measuring devices, particularly when measuring short distances, is a challenge.
A light-emitting and light-receiving device with a reflective element having multiple surfaces angled differently with respect to the pivot axis, where at least one surface has lower reflectivity than others, to manage light intensity and prevent saturation.
Prevents saturation of the light-receiving element by maintaining lower light intensity, especially for reflections from short distances, thereby enhancing measurement accuracy.
Smart Images
Figure 2026105013000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a light projection device, a light reception device, and a light projection / reception device.
Background Art
[0002] A distance measuring device that measures the distance to an object by irradiating the object with light and receiving and analyzing the light reflected by the object is known. In such a distance measuring device, a polygon mirror that rotates around a rotation axis and has a plurality of reflecting surfaces is used as a reflecting element for reflecting the light emitted from a light source for projection or guiding the return light from the object to a light receiving element. In order to enable light to be emitted in various directions using such a polygon mirror, a polygon mirror provided with a plurality of reflecting surfaces at different angles with respect to the rotation axis has been proposed (for example, Patent Document 1).
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] Since the amount of return light from an object is inversely proportional to the square of the distance to the object, the return light from an object at a short distance may saturate the light receiving element. When a polygon mirror as in the above prior art is used, the light reflected by each of the plurality of reflecting surfaces is emitted in different directions. Therefore, for example, when light is emitted in the direction of the ground, there is a problem that the return light may saturate the light receiving element because the light is reflected at a shorter distance compared to when it is emitted in other directions with different heights.
[0005] Thus, one example of a problem is that depending on the angle between each reflective surface of the polygon mirror and the axis of rotation, the intensity of the reflected light may increase, potentially saturating the photodetector.
[0006] The present invention has been made in view of the above-mentioned points, and one of its objectives is to provide a light-emitting device, a light-receiving device, or a light-emitting / receiving device that can emit and receive light while suppressing the saturation of the light-receiving element. [Means for solving the problem]
[0007] The invention described in claim 1 is a light-emitting and light-receiving device that emits light toward a predetermined area and receives the emitted light reflected by an object within the predetermined area as reflected light, comprising: a light source that emits the emitted light; a reflective element that rotates around a pivot axis, reflects the emitted light toward the predetermined area, and reflects the reflected light; and a light-receiving element that receives the reflected light, wherein the reflective element has a plurality of surfaces to which the emitted light and the reflected light are incident and which each has a different angle with respect to the pivot axis, and one of the plurality of surfaces has a lower reflectivity with respect to the emitted light and the reflected light than the other surfaces. [Brief explanation of the drawing]
[0008] [Figure 1] This is a block diagram showing the configuration of the distance measuring device in this embodiment. [Figure 2A] This is a schematic diagram illustrating the operation of the distance measuring device in this embodiment. [Figure 2B] This is a schematic diagram illustrating the operation of the distance measuring device in this embodiment. [Figure 3] This is a schematic diagram illustrating the illumination of light reflected from the reflective surface of a polygon mirror. [Figure 4A] This is a schematic diagram illustrating the reflection of light by the reflective surface S1 of a polygon mirror. [Figure 4B] This is a schematic diagram illustrating the reflection of light by the reflective surface S2 of a polygon mirror. [Figure 4C] This is a schematic diagram illustrating the reflection of light by the reflective surface S3 of a polygon mirror. [Figure 4D] It is a schematic diagram showing the reflection of light by the reflecting surface S4 of the polygon mirror. [Figure 5A] It is a diagram showing the reflecting surface of the polygon mirror of Example 1. [Figure 5B] It is a diagram showing the reflecting surface of the polygon mirror of Example 1. [Figure 6] It is a schematic diagram showing the relationship between the moving body equipped with the distance measuring device of this example and the scanning light. [Figure 7A] It is a diagram showing another example of the reflecting surface of the polygon mirror of Example 1. [Figure 7B] It is a diagram showing another example of the reflecting surface of the polygon mirror of Example 1. [Figure 7C] It is a diagram showing another example of the reflecting surface of the polygon mirror of Example 1. [Figure 8A] It is a diagram showing another example of the reflecting surface of the polygon mirror of Example 1. [Figure 8B] It is a diagram showing another example of the reflecting surface of the polygon mirror of Example 1. [Figure 8C] It is a diagram showing another example of the reflecting surface of the polygon mirror of Example 1. [Figure 9A] It is a diagram showing another example of the reflecting surface of the polygon mirror of Example 1. [Figure 9B] It is a diagram showing another example of the reflecting surface of the polygon mirror of Example 1. [Figure 9C] It is a diagram showing another example of the reflecting surface of the polygon mirror of Example 1. [Figure 10A] It is a diagram showing another example of the reflecting surface of the polygon mirror of Example 1. [Figure 10B] It is a diagram showing another example of the reflecting surface of the polygon mirror of Example 1. [[ID=4s]] [Figure 11A] It is a diagram showing the reflecting surface of the polygon mirror of Example 2. [Figure 11B] It is a diagram showing another example of the reflecting surface of the polygon mirror of Example 2. [Figure 12A] It is a diagram showing another example of the reflecting surface of the polygon mirror of Example 2. [Figure 12B]This is a diagram showing another example of the reflecting surface of the polygon mirror of Example 2. [Figure 12C] This is a diagram showing another example of the reflecting surface of the polygon mirror of Example 2. [Figure 13A] This is a diagram showing another example of the reflecting surface of the polygon mirror of Example 2. [Figure 13B] This is a diagram showing another example of the reflecting surface of the polygon mirror of Example 2. [Figure 13C] This is a diagram showing another example of the reflecting surface of the polygon mirror of Example 2.
Modes for Carrying Out the Invention
[0009] Preferred embodiments of the present invention will be described in detail below. In the descriptions of the following embodiments and the accompanying drawings, the same reference numerals are given to substantially the same or equivalent parts.
Examples
[0010] FIG. 1 is a block diagram showing the configuration of the distance measuring device 100 of Example 1. The distance measuring device 100 is an optical distance measuring device that optically measures the distance to an object. The distance measuring device 100 is mounted on a moving body such as a vehicle, and measures the distance to an object by irradiating light in the traveling direction of the moving body.
[0011] The distance measuring device 100 includes a light source unit 11 including a light source 11A and a light source drive circuit 11B. The light source 11A generates and emits pulsed laser light. The light source drive circuit 11B generates a drive signal for the light source 11A to emit laser light and applies it to the light source 11A.
[0012] The distance measuring device 100 has an optical scanning unit 12 that scans a target area (scanning target area) to be measured using laser light emitted from the light source 11A of the light source unit 11. The optical scanning unit 12 has a polygon mirror 12A and a mirror driving circuit 12B that drives the polygon mirror 12A. The polygon mirror 12A is a rotating polyhedron that rotates around a pivot axis and has multiple reflective surfaces. The optical scanning unit 12 scans the scanning target area by changing the irradiation direction by reflecting the laser light emitted from the light source 11A off the reflective surfaces of the polygon mirror 12A.
[0013] The distance measuring device 100 has a distance measuring unit 13 that measures the distance to an object. The distance measuring unit 13 has a light receiving unit 13A and a distance calculation unit 13B. The light receiving unit 13A receives light (hereinafter referred to as reflected light) that has been reflected by the object from the scanning light irradiated by the scanning of the optical scanning unit 12. The light receiving unit 13A is composed of a light receiving element such as an APD (Avalanche Photodiode), and generates a received light signal by converting the intensity of the received reflected light into an electrical signal. The distance calculation unit 13B calculates the distance between the distance measuring device 100 and the object based on the received light signal generated by the light receiving unit 13A.
[0014] The distance measuring device 100 has a control unit 14 consisting of a CPU (Central Processing Unit) and the like. The control unit 14 controls the operation of the light source unit 11, the optical scanning unit 12, and the distance measuring unit 13.
[0015] Figure 2A schematically shows an example of the arrangement of the light source 11A and the polygon mirror 12A, and the path of the laser beam emitted from the light source 11A when it irradiates the object OJT.
[0016] A beam splitter BS is provided in the optical path of the laser beam L1 emitted from the light source 11A. The laser beam L1 passes through the beam splitter BS and is incident on one of the multiple reflective surfaces of the polygon mirror 12A. The laser beam L1 is reflected by the reflective surface of the polygon mirror 12A and emitted as scanning light L2 toward the scanning target area R0.
[0017] Figure 2B schematically shows an example of the arrangement of the beam splitter BS and the light receiving unit 13A, and the path of the reflected light when the laser light reflected by the object OJT is received by the light receiving unit 13A of the distance measuring unit 13.
[0018] The scanning light L2 reflected by the object OJT is incident as a return light L3 on one of the reflective surfaces of the polygon mirror 12A. The return light L3 reflected by the reflective surface of the polygon mirror 12A is further reflected by the beam splitter BS and is received as a return light L4 by the light receiving unit 13A of the distance measuring unit 13. The light receiving unit 13A generates a received signal based on the intensity of the return light L4.
[0019] The distance calculation unit 13B of the distance measuring unit 13 calculates the distance between the light receiving unit 13A and the object OJT based on the light receiving signal generated by the light receiving unit 13A. For example, the distance calculation unit 13B calculates the distance to the object OJT using the TOF (Time of Flight) method.
[0020] Next, the polygon mirror 12A of this embodiment will be described in detail. The polygon mirror 12A is positioned such that the axis direction of the rotation axis RA is vertical. The polygon mirror 12A has reflective surfaces S1 to S4, each with a different angle with respect to the vertically downward direction of the rotation axis RA (hereinafter referred to as the angle with the rotation axis RA).
[0021] As shown in Figure 3, the laser beam L1 incident on the polygon mirror 12A is reflected by one of the reflective surfaces S1 to S4 and projected as scanning light L2 towards one of the four regions F1 to F4 with different heights within the scanning target region R0.
[0022] Figures 4A to 4D schematically show the angles between each of the reflective surfaces S1 to S4 of the polygon mirror 12A and the rotation axis RA, and the direction in which the laser light L1 reflected from each reflective surface is emitted as scanning light L2.
[0023] The reflective surface S1 is formed such that the angle θ1 it makes with the rotation axis RA is smaller than the angle it makes with the other reflective surfaces (S2, S3, and S4) and the rotation axis RA. Since the polygon mirror 12A is positioned so that the axis direction of the rotation axis RA is vertical, light incident on the reflective surface S1 is reflected in a lower direction than when it is incident on the other reflective surfaces. Therefore, as shown in Figure 4A, the laser light L1 reflected by the reflective surface S1 is directed as scanning light L2 towards region F1, which is the lowest-height region among regions F1 to F4 of the scanning target region R0.
[0024] The reflective surface S2 is formed such that the angle θ2 between the reflective surface S2 and the rotation axis RA is greater than the angle θ1 between the reflective surface S1 and the rotation axis RA, and smaller than the angle between the other reflective surfaces (S3 and S4) and the rotation axis RA. Therefore, as shown in Figure 4B, the laser light L1 reflected by the reflective surface S2 is irradiated as scanning light L2 towards region F2, which is higher than region F1 and lower than regions F3 and F4.
[0025] The reflective surface S3 is formed such that the angle θ3 it makes with the rotation axis RA is greater than the angle θ1 between the reflective surface S1 and the rotation axis RA, and the angle θ2 between the reflective surface S2 and the rotation axis RA, and smaller than the angle between the reflective surface S4 and the rotation axis RA. Therefore, as shown in Figure 4C, the laser light L1 reflected by the reflective surface S3 is irradiated as scanning light L2 towards region F3, which is higher than regions F1 and F2 and lower than region F4.
[0026] The reflective surface S4 is formed such that the angle θ4 it makes with the rotation axis RA is larger than the angle θ1 between the reflective surface S1 and the rotation axis RA, the angle θ2 between the reflective surface S2 and the rotation axis RA, and the angle θ3 between the reflective surface S3 and the rotation axis RA. Therefore, as shown in Figure 4D, the laser light L1 reflected by the reflective surface S4 is irradiated as scanning light L2 toward region F4, which is the highest region among regions F1 to F4.
[0027] Furthermore, the polygon mirror 12A in this embodiment is configured such that the reflectivity of the reflective surface S1 with respect to incident light is lower than the reflectivity of the other reflective surfaces S2 to S4.
[0028] Figure 5A shows an example of the reflective surface of the polygon mirror 12A. A low-reflectivity film LF1, consisting of a low-reflectivity metal film or dielectric multilayer film, is formed on the surface of the reflective surface S1. As a result, the reflective surface S1 has a lower reflectivity than the reflective surfaces S2, S3, and S4.
[0029] Furthermore, not only the reflective surface S1 but also other reflective surfaces may be configured to have different reflectances. Figure 5B shows an example of such a polygon mirror 12A reflective surface. For example, a low-reflectance film LF2 is formed on the surface of the reflective surface S2, which has a higher reflectance than the low-reflectance film LF1 formed on the surface of the reflective surface S1. As a result, the reflective surface S2 has a reflectance that is higher than that of the reflective surface S1 and lower than that of the reflective surfaces S3 and S4.
[0030] According to the configuration of the polygon mirror 12A as shown in Figure 5A or Figure 5B, the light reflected by the reflective surface S1 is of lower intensity than the light reflected by the reflective surfaces S2, S3, and S4. As shown in Figures 4A and 4B, the laser light L1 emitted from the light source 11A and reflected by the reflective surface S1 is irradiated as scanning light L2 towards the low-intensity region F1 within the scanning target region R0. Therefore, region F1 is irradiated with scanning light L2 of lower intensity compared to the other regions F2 to F4.
[0031] Furthermore, the reflected laser light L3, which is reflected by the object OJT, is reflected by the reflective surfaces S1 to S4 of the polygon mirror 12A and received by the light receiving unit 13A. At this time, the reflected light from the object OJT within region F1 is reflected by the reflective surface S1 and then received by the light receiving unit 13A. Therefore, the reflected light from region F1 is reflected by the reflective surface S1, which has low reflectivity, and is received by the light receiving unit 13A as reflected light of low intensity.
[0032] Figure 6 is a schematic diagram showing the relationship between the mobile body VH on which the distance measuring device 100 of this embodiment is mounted and the scanning light L2 emitted from the distance measuring device 100. In the figure, the scanning light L2 emitted after being reflected by the reflective surface S1 (hereinafter referred to as the scanning light L2 from the reflective surface S1) is shown as L2(S1), and the scanning light L2 emitted after being reflected by the reflective surface S3 (hereinafter referred to as the scanning light L2 from the reflective surface S3) is shown as L2(S3).
[0033] As shown in Figure 4A, the scanning light L2 from the reflective surface S1 is directed toward a lower region F1 within the scanning target region R0. Therefore, the scanning light L2 from the reflective surface S1 is reflected by, for example, the road surface on which the moving object VH travels. In other words, the scanning light L2 from the reflective surface S1 is reflected over a shorter distance than the scanning light L2 from the reflective surface S3 is reflected by the target object OJT. Consequently, unlike in this embodiment, if the reflective surface S1 had the same reflectivity as the other reflective surfaces S2 to S4, the reflected laser light emitted from the reflective surface S1 and then reflected by the road surface on which the moving object VH travels would be high-intensity light, saturating the light-receiving element of the light-receiving unit 13A.
[0034] In contrast, the distance measuring device 100 of this embodiment is configured such that the reflectance of the reflective surface S1 is lower than that of the reflective surfaces S2 to S4. Therefore, even when light is reflected from an object at a short distance, such as the road surface on which the moving body VH travels, the intensity of the reflected light can be kept low, thus preventing saturation of the light-receiving element.
[0035] Furthermore, the method for creating differences in reflectivity between the reflective surfaces S1 to S4 of the polygon mirror 12A is not limited to the formation of low-reflectivity metal films or dielectric multilayer films. For example, as shown in Figures 7A to C, differences in reflectivity may be created by utilizing light scattering and diffraction by forming uneven structures on the surfaces of reflective surfaces S1 and S2. As shown in Figure 7A, no uneven structure is formed on the surface of reflective surface S4. In contrast, as shown in Figure 7B, an uneven structure US is formed on the surface of reflective surface S2. As a result, scattering or diffraction of light incident on reflective surface S2 occurs, and the reflectivity of reflective surface S2 becomes lower than that of reflective surface S4. Also, as shown in Figure 7C, even more uneven structures US are formed on the surface of reflective surface S1, and the reflectivity of reflective surface S1 becomes even lower than that of reflective surface S2.
[0036] Furthermore, instead of using a common polygon mirror 12A for both the emission of scanning light L2 and the reception of reflected light L3 as described above, separate polygon mirrors may be provided for emission and reception. In such cases, as shown in Figures 8A-C, polygon mirrors with varying reflectivity can be used for reception by randomly forming low-reflection regions LA on the surfaces of reflective surfaces S1 and S2. As shown in Figure 8A, no low-reflection regions LA are formed on the surface of reflective surface S4. In contrast, as shown in Figure 8B, low-reflection regions LA are randomly formed on the surface of reflective surface S2, resulting in a lower reflectivity for the entire surface than that of reflective surface S4. Also, as shown in Figure 8C, low-reflection regions LA are formed over an even wider area on the surface of reflective surface S1, resulting in an even lower reflectivity than that of reflective surface S2.
[0037] Similarly, as polygon mirrors for receiving light, as shown in Figures 9A-C, polygon mirrors with different reflectivity can be used by forming a low-reflection region LA in the center of the reflective surfaces S1 and S2. As shown in Figure 9A, no low-reflection region LA is formed on the surface of reflective surface S4. In contrast, as shown in Figure 9B, a low-reflection region LA is formed in the center of reflective surface S2, resulting in a lower reflectivity for the entire surface than reflective surface S4. Furthermore, as shown in Figure 9C, an even larger low-reflection region LA is formed in the center of reflective surface S1, resulting in an even lower reflectivity than reflective surface S2.
[0038] Furthermore, if a polygon mirror having a reflective surface with randomly formed low-reflection regions LA, as shown in Figures 8B and 8C, is to be used for both the emission of scanning light L2 and the reception of reflected light L3, this can be achieved by providing, for example, a strip-shaped emission region EA on the reflective surface, as shown in Figure 10A. With this configuration, when emitting scanning light L2, the emission region EA is used to irradiate the scanning light L2 with a constant reflectivity, and when receiving reflected light L3, the reflected light L3 is reflected while lowering the average reflectivity of the entire surface. Similarly, if a polygon mirror having a reflective surface with a low-reflection region LA formed in the center, as shown in Figures 9B and 9C, is to be used for both the emission of scanning light L2 and the reception of reflected light L3, this can be achieved by providing a emission region EA on the reflective surface, as shown in Figure 10B. [Examples]
[0039] Next, Embodiment 2 of the present invention will be described. In the distance measuring device of this embodiment, a polygon mirror for receiving light used to receive the reflected light L3 is provided separately from the polygon mirror used to emit the scanning light L2.
[0040] Figure 11A shows an example of the light-receiving polygon mirror 22A of this embodiment. The light-receiving polygon mirror 22A has reflective surfaces S1, S2, S3, and S4, each having a different angle with respect to the rotation axis RA, similar to the polygon mirror 12A of Embodiment 1. The angles that the reflective surfaces S1 to S4 make with respect to the rotation axis RA are also configured in the same way as those of the polygon mirror 12A of Embodiment 1.
[0041] The reflective surface S1 is provided with a central region CA and a peripheral region SA surrounding the central region CA. The central region CA is configured such that its reflectivity per unit area is equivalent to that of reflective surfaces S2, S3, and S4. On the other hand, the peripheral region SA has a low-reflectivity region formed from a low-reflectivity metal film or dielectric multilayer film. As a result, the reflective surface S1 has a lower reflectivity as an average of the entire surface than the reflective surfaces S2, S3, and S4.
[0042] Furthermore, not only the reflective surface S1, but other reflective surfaces may also be configured to have different reflectances using a similar method. Figure 11B shows an example of a reflective surface of such a light-receiving polygon mirror 22A. The reflective surface S2 is provided with a central region CA that is smaller in area than the central region CA of the reflective surface S1, and a peripheral region SA that is larger in area than the peripheral region SA of the reflective surface S1. As a result, the average reflectance of the entire surface of the reflective surface S2 is higher than the reflectance of the reflective surface S1, and lower than the reflectances of the reflective surfaces S3 and S4.
[0043] According to the configuration of the light-receiving polygon mirror 22A as shown in Figure 11A or Figure 11B, the light reflected by the reflective surface S1 is of lower intensity than the light reflected by the reflective surfaces S2 to S4. Similar to Example 1, the reflected light from the object OJT in region F1 is reflected by the reflective surface S1 and then received by the light-receiving unit 13A. Therefore, the reflected light from region F1 is reflected by the reflective surface S1, which has low reflectivity, and is received by the light-receiving unit 13A as reflected light of lower intensity than the reflected light reflected by the reflective surfaces S2 to S4 (i.e., the reflected light from regions F2 to F4). As a result, even when the laser light is reflected by an object at a short distance, such as the road surface on which the moving object VH travels, the intensity of the reflected light can be kept low, thus preventing saturation of the light-receiving element.
[0044] Furthermore, in the light-receiving polygon mirror 22A of this embodiment, the reflectivity per unit area is relatively high in the central region CA of the reflective surface S1, while the peripheral region SA is a low-reflectivity region. As a result, the amount of light reflected by the reflective surface S1 can be made smaller than the amount of light reflected by the other reflective surfaces S2 to S4, and the outer edge of the light reflected by the reflective surface S1 (i.e., the diameter in the direction perpendicular to the direction of light propagation) can be made smaller than the outer edge of the light reflected by the other reflective surfaces S2 to S4.
[0045] A condensing lens (not shown) is provided between the light-receiving polygon mirror 22A and the light-receiving unit 13A to collect the reflected light and guide it to the light-receiving unit 13A. The numerical aperture (NA) of this condensing lens and the distance between the condensing lens and the light-receiving unit 13A are set to a distance that can be considered as infinity. Therefore, light from a short distance will not be sufficiently focused due to the spherical aberration of the condensing lens and will be received by the light-receiving element.
[0046] However, in the light-receiving polygon mirror 22A of this embodiment, it is possible to reduce the outer edge of the light on the reflective surface S1, which is expected to reflect back light from a short distance, so that the light from a short distance can be sufficiently focused by the focusing lens. Therefore, the light-receiving unit 13A can receive back light from a short distance in a focused state.
[0047] In Figures 11A and 11B, the case where the reflectance per unit area of the central region CA is equal to that of the reflective surface S4 is explained, but these may be different. For example, as shown in Figures 12A-C, a low-reflectance region LA2 with a higher reflectance than the low-reflectance region LA1 of the peripheral region SA may be formed in the central region CA of the reflective surfaces S1 and S2.
[0048] Furthermore, as shown in Figures 13A-C, a low-reflection region may be provided in the center of the reflective surface to create a difference in the size of the outer edge of the reflected light. For example, as shown in Figure 13A, a low-reflection region LA is provided in the center of the reflective surface S3. On the reflective surface S4, light with the dashed line portion in Figure 13A as its outer edge is reflected. In contrast, as shown in Figure 13B, a low-reflection region LA1, which is narrower in width than the low-reflection region of the reflective surface S3, is provided in the center of the reflective surface S2. A low-reflection region LA2 is provided in the peripheral area surrounding the center of the reflective surface S2. As a result, the reflective surface S2 reflects light with an outer edge smaller than the dashed line portion. Also, as shown in Figure 13C, the reflective surface S1 has a low-reflection region LA except for the central area which is even smaller than the low-reflection region LA1 in the center of the reflective surface S2. As a result, the reflective surface S1 reflects light with an outer edge even smaller than the outer edge of the light reflected by the reflective surface S2.
[0049] It should be noted that the embodiments of the present invention are not limited to those shown in the above examples. For example, Embodiment 1 and Embodiment 2 may be combined, for instance, with the light-emitting polygon mirror configured as in Embodiment 1 and the light-receiving polygon mirror configured as in Embodiment 2.
[0050] Furthermore, although the above embodiment described a case in which the polygon mirror has four reflective surfaces S1 to S4, the number of reflective surfaces is not limited to this. That is, the polygon mirror only needs to have multiple reflective surfaces, each with a different angle with respect to the pivot axis, and at least one of these reflective surfaces having a lower reflectivity than the others.
[0051] Furthermore, the series of processes described in the above embodiment can be carried out by computer processing according to a program stored on a recording medium such as ROM. [Explanation of Symbols]
[0052] 100 Rangefinder 11 Light source section 11A light source 11B Light source drive circuit 12 Optical scanning unit 12A Polygon Mirror 12B Mirror drive unit 13 Ranging section 13A light receiving section 13B Distance calculation section 14 Control Unit
Claims
1. A light-emitting and receiving device that emits light toward a predetermined area and receives the emitted light reflected by an object within the predetermined area as reflected light, A light source that emits the aforementioned emitted light, A reflective element that rotates around a pivot axis, reflects the emitted light and emits it toward the predetermined region, and reflects the returned light, A light-receiving element that receives the reflected light, It has, The reflective element has multiple surfaces to which the emitted light and the reflected light are incident and which each have different angles with respect to the pivot axis. A light-emitting and receiving device characterized in that one of the plurality of surfaces has a lower reflectivity with respect to the emitted light and the reflected light than the other surfaces.
2. The light-emitting and receiving device according to claim 1, characterized in that the first surface of the reflective element has a first region and a second region having a lower reflectivity than the first region.
3. Each of the plurality of surfaces of the reflective element has a first region and a second region having a lower reflectivity than the first region. The light-emitting and receiving device according to claim 1, characterized in that the first region of the surface 1 has a smaller area than the first region of the other surface.
4. The light-emitting and receiving device according to claim 2 or 3, characterized in that the second region is arranged around the first region.
5. A light transmission and reception method performed by a light transmission and reception device having a light source, a reflecting element that rotates around a pivot axis and has multiple surfaces, each having a different angle with the pivot axis, and one of the multiple surfaces having a lower reflectivity than the other surfaces, and a light receiving element, The light source emits light toward a predetermined area, The reflective element rotates around the pivot axis and reflects the emitted light, which is then emitted toward the predetermined region. The reflective element is used to reflect the reflected light, which is the outgoing light, that has been reflected by an object within the predetermined region. The light-receiving element receives the reflected light, A method for transmitting and receiving light, characterized by including the following:
6. A computer controls a light-emitting and light-receiving device having a light source, a reflecting element that rotates around a pivot axis and has multiple surfaces, each having a different angle with the pivot axis, and one of the multiple surfaces having a lower reflectivity than the other surfaces, and a light-receiving element. The steps include controlling the light source to emit light toward a predetermined area, The steps include controlling the reflective element to rotate around the pivot axis, reflecting the emitted light and directing it toward the predetermined area, The steps include controlling the reflective element to reflect the reflected light, which is the outgoing light, that has been reflected by an object within the predetermined region, The steps include controlling the light-receiving element to receive the reflected light, A program characterized by causing the execution of a specific action.
7. A computer controls a light-emitting and light-receiving device having a light source, a reflecting element that rotates around a pivot axis and has multiple surfaces, each having a different angle with the pivot axis, and one of the multiple surfaces having a lower reflectivity than the other surfaces, and a light-receiving element. The steps include controlling the light source to emit light toward a predetermined area, The steps include controlling the reflective element to rotate around the pivot axis, reflecting the emitted light and directing it toward the predetermined area, The steps include controlling the reflective element to reflect the reflected light, which is the outgoing light, that has been reflected by an object within the predetermined region, The steps include controlling the light-receiving element to receive the reflected light, A recording medium that stores a program that executes a program.