Polygon mirror

Abstract

The present invention, in order to reflect laser light, comprises: a mirror surface (2) disposed on a lateral surface; and an index part (3) that is disposed on a convex polygonal surface (11) perpendicular to the lateral surface so as to serve as an index indicating the base point of rotation, and that includes a recess formed in a concave shape.

Description

Polygon mirror

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to a polygon mirror.

[0002] It is generally known to use a polygon mirror for laser scanning (see, for example, Patent Document 1). When a polygon mirror is attached to a motor, an index indicating the base point of rotation is sometimes provided on the motor to perform balance correction to suppress vibrations caused by misalignment of parts. However, the index indicating the base point of rotation is provided on the motor, not on the polygon mirror.

[0003] Japanese Patent Application Laid-Open No. 2020-170049

[0004] According to the embodiment, it is possible to provide a polygon mirror in which an index indicating the base point of rotation is appropriately provided.

[0005] A polygon mirror according to an embodiment of the present invention comprises a mirror surface provided on a side surface to reflect laser light, and an index portion including a concave recess provided on a convex polygonal surface perpendicular to the side surface as an index indicating the base point of rotation.

[0006] FIG. 1 is a perspective view showing the configuration of a polygon mirror according to a first embodiment of the present invention. FIG. 2 is an enlarged view of the vicinity of the index portion of the surface of the polygon mirror according to the first embodiment. FIG. 3 is a cross-sectional view of the vicinity of the index portion of the surface of the polygon mirror according to the first embodiment shown in FIG. 2 taken along line A-A. FIG. 4 is a perspective view showing the configuration of a polygon mirror according to a second embodiment of the present invention. FIG. 5 is an enlarged view of the vicinity of the index portion of the surface of the polygon mirror according to the second embodiment. FIG. 6 is a cross-sectional view of the vicinity of the index portion of the surface of the polygon mirror according to the second embodiment taken along line B-B. FIG. 7 is an enlarged view of the vicinity of the index portion of the surface of a modified polygon mirror according to the second embodiment.

[0007] 1 is a perspective view showing the configuration of a polygon mirror 1 according to a first embodiment of the present invention. In the drawings, the same parts are given the same reference numerals.

[0008] The polygon mirror 1 is an optical component that scans a laser by rotating. The polygon mirror 1 is attached to a motor and used. For example, the polygon mirror 1 is used in LiDAR (light detection and ranging). LiDAR is an optical sensor technology that irradiates an object with a scanning laser beam, measures the distance and position of the object, and identifies the properties of the object.

[0009] The polygon mirror 1 has a columnar shape with a convex polygonal cross section (or front and back surfaces). The polygon mirror 1 has a circular hole H1 that penetrates from the center of the front surface to the back surface. The rotation shaft of a motor to which the polygon mirror 1 is attached is inserted and fixed into the hole H1. Here, the polygon mirror 1 is mainly described as having a columnar shape with a square cross section (i.e., a rectangular parallelepiped), but it may have any shape as long as the cross section is a columnar shape with any convex polygonal cross section. Furthermore, the polygon mirror 1 may have a shape similar to a tilt mirror. A tilt mirror has a convex polygonal shape with parallel front and back surfaces and trapezoidal side surfaces (mirror surfaces 2) that are inclined with respect to the perpendicular to the front and back surfaces.

[0010] The polygon mirror 1 has a plurality of mirror surfaces 2 and an index portion 3. The mirror surfaces 2 reflect laser light emitted from a light source when the polygon mirror 1 rotates. The laser light reflected by the mirror surfaces 2 is irradiated onto an object in a scanning manner. The mirror surfaces 2 correspond to the side surfaces of the polygon mirror 1. Therefore, the number of mirror surfaces 2 is the number of side surfaces of the polygon mirror 1. Here, the polygon mirror 1 is described as a rectangular parallelepiped, so the number of mirror surfaces 2 is four.

[0011] The index unit 3 is an index that indicates the base point of rotation of the polygon mirror 1 (or the multiple mirror surfaces 2) in order to perform balance correction to suppress vibrations caused by misalignment of parts, etc. The index unit 3 is provided near one of the multiple vertices of the convex polygonal (e.g., quadrangular) surface 11 of the polygon mirror 1. The surface 11 is a convex polygonal surface that is perpendicular to the multiple surfaces (side surfaces) on which the multiple mirror surfaces 2 of the polygon mirror 1 are respectively arranged. The surface 11 may be the front surface of the polygon mirror 1 or the back surface of the polygon mirror 1. For example, the surface 11 of the polygon mirror 1 is the surface on which a motor is attached.

[0012] The index portion 3 will be described in detail with reference to Figures 2 and 3. Figure 2 is an enlarged view of the vicinity of the index portion 3 on the surface 11 of the polygon mirror 1. Figure 3 is a cross-sectional view taken along line A-A of the vicinity of the index portion 3 on the surface 11 shown in Figure 2.

[0013] The index portion 3 is configured such that ink 31 is applied to a recess D11 formed near one vertex of the surface 11 so as to fill the recess D11.

[0014] Any material may be used as the ink 31 as long as it can function as an index indicating the base point of rotation. For example, if a sensor is used to detect the index portion 3 (the base point of rotation) using color contrast (changes in light reflectance), the ink 31 must not reflect light.

[0015] If a sensor capable of detecting steps is used as the sensor for detecting the index portion 3, the ink 31 does not need to be applied, and the recess D11 alone can function as an index. For example, a sensor capable of detecting steps is a laser distance sensor or a capacitance-type macro sensor.

[0016] The recess D11 serves as a frame for applying the ink 31. Providing the recess D11 prevents variations in the application (marking) of the ink 31. For example, when applying the ink 31, the ink 31 is more likely to fit inside the recess D11, and the ink 31 is always applied over a constant area.

[0017] Furthermore, even if the index portion 3 is rubbed during transportation or packaging of the polygon mirror 1, the provision of the recess D11 makes it difficult for the rubbed ink 31 to spread outside the recess D11. It is also desirable that the ink 31 does not rise higher than the surface 11 on which the recess D11 is provided. This makes it possible to prevent the ink 31 from rubbing against other members (for example, packaging materials).

[0018] According to this embodiment, by providing the recess D11 as the index part 3 indicating the base point of rotation, the ink 31 can be appropriately applied to the recess D11 and the ink 31 can be prevented from rubbing off.

[0019] For example, unlike this embodiment, a polygon mirror having an index portion with ink 31 applied directly to its surface 11 without a recess D11 will be described below. If this polygon mirror is transported in a container such as a plastic tray, the surface 11 will come into contact with the container during transport, causing the ink 31 in the index portion to also come into contact with the container. This makes the ink 31 more likely to rub against the container. In contrast, providing the recess D11 as in this embodiment prevents the container from coming into contact with the ink 31, thereby preventing the ink 31 from rubbing against it.

[0020] Furthermore, if a sensor capable of detecting a step is used as the sensor for detecting the base point of rotation of the polygon mirror 1, the index part 3 may be formed only with the recess D11, and may not be coated with ink 31. This eliminates the need to worry about the ink 31 on the index part 3 being rubbed off when the polygon mirror 1 is transported or packed.

[0021] Second Embodiment FIG. 4 is a perspective view showing the configuration of a polygon mirror 1A according to a second embodiment of the present invention.

[0022] The polygon mirror 1A is the same as the polygon mirror 1 of the first embodiment except that the surface 11 and the index portion 3 are replaced with a surface 11A and an index portion 3A. In other respects, the polygon mirror 1A is the same as the first embodiment.

[0023] A ring-shaped protrusion P11 is formed on the surface 11A on which the index portion 3A is provided. The ring-shaped protrusion P11 is formed in a ring-shaped protrusion shape that extends over the entire surface 11A, with the hole H1 as its center.

[0024] For example, the ring-shaped protrusion P11 is provided for the purpose of fixing the polygon mirror 1A, preventing deformation of the mirror surface 2, or serving as a reference for processing the polygon mirror 1A. Note that the ring-shaped protrusion P11 may or may not be provided for any purpose.

[0025] The index portion 3A will be described with reference to Figures 5 and 6. Figure 5 is an enlarged view of the vicinity of the index portion 3A on the surface 11A of the polygon mirror 1A. Figure 6 is a cross-sectional view taken along line B-B of the vicinity of the index portion 3A on the surface 11A shown in Figure 5.

[0026] The index section 3A is similar to the index section 3 according to the first embodiment except for the difference in configuration. Here, the differences from the index section 3 according to the first embodiment will be mainly described.

[0027] The index portion 3A includes a recess D11A, a protrusion P12, and ink 31.

[0028] The recess D11A is formed so as to extend linearly from near the vertex of the surface 11A toward the center of the surface 11A and reach the ring-shaped protrusion P11. That is, the recess D11A is provided near the vertex of the surface 11A so as to draw a diagonal line of the surface 11A.

[0029] The protrusion P12 is formed in the widthwise center of the recess D11A so as to protrude linearly parallel to the recess D11A. The upper surface of the protrusion P12 is the surface to which the ink 31 is applied. As in the first embodiment, the ink 31 does not necessarily have to be applied.

[0030] For example, when applying ink 31 to the flat surface 11A with a marker with a rounded tip, the thickness of the applied ink 31 varies depending on the pressure of the marker. Therefore, it is not easy to apply ink 31 only to a predetermined area of ​​the flat surface 11A. In contrast, the index part 3A has recesses D11A formed on both sides of the protrusion P12, making it easy to always apply ink 31 only to the predetermined area (the upper surface of the protrusion P12).

[0031] The height of the upper surface of the convex portion P12 may be changed as desired. For example, the convex portion P12 can be easily formed by designing the height of the upper surface of the convex portion P12 to be the same height as the surface 11A. Specifically, the portion of the surface 11A to be the convex portion P12 (the portion to which the ink 31 is applied) is determined, and recesses D11A are formed on both sides of the convex portion P12 so that the convex portion P12 remains, thereby easily forming the convex portion P12 on the surface 11A.

[0032] Furthermore, by making the height of the upper surfaces of the protrusions P12 lower than the surface 11A, it is possible to prevent the ink 31 applied to the upper surfaces of the protrusions P12 from rubbing against other members (packaging material, etc.). Furthermore, by making the height of the protrusions P12 plus the height of the ink 31 lower than the surface 11A in a state in which the ink 31 is applied to the protrusions P12, it is possible to further prevent the ink 31 from rubbing against other members (packaging material, etc.).

[0033] In the index portion 3A, the protrusion P12 and recess D11A do not have to reach the apex of the surface 11A as shown in Fig. 5. For example, as shown in Fig. 7, in the index portion 3Aa, the recess D11Aa is formed so that both sides of the protrusion P12a are connected to the apex. A ring-shaped protrusion P11 is provided on the side opposite the apex of the protrusion P12a. This makes it easier to apply ink 31 to the top surface of the protrusion P12a.

[0034] According to this embodiment, by providing the recessed portion D11A and the protruding portion P12 as the index portion 3A, the ink 31 can be appropriately applied to the upper surface of the protruding portion P12.

[0035] Furthermore, as in the first embodiment, the index portion 3A may be configured only by the shapes of the recessed portion D11A and the protruding portion P12, without applying the ink 31. This eliminates the need to worry about the ink 31 on the index portion 3A being rubbed off when transporting or packaging the polygon mirror 1A.

[0036] It is to be understood that additional advantages and modifications may readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

Claims

1. A polygon mirror comprising: a mirror surface provided on a side surface to reflect laser light; and an index portion including a concave recess provided on a convex polygonal surface different from the side surface as an index indicating the base point of rotation.

2. The polygon mirror according to claim 1, characterized in that the index portion has ink applied to the inside of the recess.

3. The polygon mirror according to claim 1, characterized in that the index portion includes a protrusion formed in a protruding shape inside the recess.

4. The polygon mirror according to claim 3, characterized in that the upper surfaces of the convex portions are coated with ink.

5. The polygon mirror according to claim 3, characterized in that the height of the convex portion is equal to or less than the height of the face of the convex polygon.

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