Reflective optical unit and encoder

Abstract

The invention provides a reflective optical unit capable of reducing signal fluctuation and an encoder. This reflective optical unit (1) is provided with a substrate (40), and a light-emitting element (10) and a light-receiving element (30) which are positioned on the substrate (40). The difference between a first height (H1) with respect to the substrate (40) of a first surface (S1) of the light-emitting element (10) facing the opposite side to the substrate (40) and a second height (H2) with respect to the substrate (40) of a second surface (S2) of the light-receiving element (30) facing the opposite side to the substrate (40) is equal to or less than the thickness of the light-emitting element (10), and the light-emitting element (10) has a thin film shape.

Description

Technical Field

[0001] This disclosure relates to reflective optical units and encoders. Specifically, this disclosure relates to a reflective optical unit for a rotary encoder, having, for example, the configuration described below. Background Technology

[0002] Previously, technologies associated with encoders were known. For example, Patent Document 1 discloses a method for suppressing the reduction in angular resolution or angular accuracy caused by axial positional changes of the code disk's rotation axis in a reflective rotary encoder using an optical sensor in which the light-receiving element and the light-emitting element are not on the same plane.

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2021-015071 Summary of the Invention

[0004] Technical issues For example, in the prior art described in Patent Document 1, for reflective rotary encoders, there is a need to achieve higher measurement accuracy than before in applications seeking greater space savings. For example, in the prior art, there is room for improvement in reducing signal fluctuations.

[0005] The purpose of this disclosure is to provide a reflective optical unit and encoder that can reduce signal fluctuations.

[0006] Technical solution Therefore, the inventors conducted in-depth research and eventually came up with the idea of ​​a "reflective optical unit" with the structure described in the title and an "encoder" with the reflective optical unit. (1) A reflective optical unit, comprising: Substrate; and The light-emitting element and the light-receiving element are located on the substrate. The difference between the first height and the second height is less than or equal to the thickness of the light-emitting element. The first height is the height of the first surface of the light-emitting element facing the side opposite to the substrate relative to the substrate, and the second height is the height of the second surface of the light-receiving element facing the side opposite to the substrate relative to the substrate. The light-emitting element has a thin-film shape. (2) As the reflective optical unit described in (1) above, wherein, The tolerance of the difference is within the range of 0μm to 5μm. (3) As the reflective optical unit described in (1) or (2) above, wherein, The reflective optical unit includes a reflector that reflects light emitted from the light-emitting surface of the light-emitting element toward the light-receiving surface of the light-receiving element. If the first optical path length between the light-emitting surface included in the first surface and the reflective surface of the reflector is set as L1, and the second optical path length between the light-receiving surface included in the second surface and the reflective surface is set as L2, then the error between L1 and L2 is within the range of 0% to 5%. (4) As a reflective optical unit as described in any one of (1) to (3) above, wherein, The light-receiving element is located directly above the substrate. The light-emitting element is located directly above the light-receiving element. (5) As the reflective optical unit described in (4) above, wherein, The edge of the light-emitting element and the circuit pattern on the second surface are directly electrically connected by a conductive material without the use of wires. (6) As the reflective optical unit described in (4) above, wherein, The light-emitting element is electrically connected to a circuit pattern located on the second surface via a transparent electrode covering the entire surface of the light-emitting element. (7) As a reflective optical unit as described in any one of (4) to (6) above, wherein, The light-receiving element has a recess on the second surface where the light-emitting element is disposed. (8) As a reflective optical unit as described in any one of (1) to (7) above, wherein, The reflective optical unit has a plurality of light-emitting elements close to each other. (9) As a reflective optical unit as described in any one of (1) to (8) above, wherein, The thickness of the light-emitting element is within the range of 0.5μm to 20μm. (10) An encoder having the reflective optical unit described in (3) above. (11) As the encoder described in (10) above, wherein, The encoder includes a rotary encoder. The reflector includes a code disk.

[0018] Technical effect According to this disclosure, a reflective optical unit and encoder capable of reducing signal fluctuations can be provided. Attached Figure Description

[0019] Figure 1A This is a perspective view schematically showing a first example of the configuration of a reflective optical unit according to an embodiment of the present disclosure.

[0020] Figure 1B It is Figure 1A An enlarged image obtained by magnifying the portion enclosed by a single-dot dashed line.

[0021] Figure 2 It schematically shows along Figure 1A The cross-sectional view of the section intercepted by the arrow II-II.

[0022] Figure 3 This is a first cross-sectional view schematically showing a second example of the configuration of a reflective optical unit according to an embodiment of the present disclosure.

[0023] Figure 4 This is a second cross-sectional view schematically showing a second example of the configuration of a reflective optical unit according to an embodiment of the present disclosure.

[0024] Figure 5 This is a cross-sectional view schematically showing a third example of the configuration of a reflective optical unit according to an embodiment of the present disclosure.

[0025] Figure 6 This is a cross-sectional view schematically showing a fourth example of the configuration of a reflective optical unit according to an embodiment of the present disclosure.

[0026] Figure 7A This is a cross-sectional view schematically showing a first example of the configuration of a reflective optical unit of the comparative example of this disclosure.

[0027] Figure 7B This is a cross-sectional view schematically showing a fifth example of the configuration of a reflective optical unit according to an embodiment of the present disclosure.

[0028] Figure 8A This is a cross-sectional view schematically showing a second example of the configuration of the reflective optical unit of the comparative example of this disclosure.

[0029] Figure 8B This is a cross-sectional view schematically showing a sixth example of the configuration of a reflective optical unit according to an embodiment of the present disclosure.

[0030] Figure 9A This is a cross-sectional view schematically showing a third example of the configuration of the reflective optical unit of the comparative example of this disclosure.

[0031] Figure 9B This is a cross-sectional view schematically showing a seventh example of the configuration of a reflective optical unit according to one embodiment of the present invention.

[0032] Figure 10 This is a schematic diagram illustrating an example of the configuration of a conventional transmissive optical rotary encoder.

[0033] Figure 11 This is a schematic diagram illustrating an example of the configuration of a conventional reflective optical rotary encoder.

[0034] Figure 12A This is a first schematic diagram used to illustrate the first subject of a conventional reflective optical rotary encoder.

[0035] Figure 12B This is a second schematic diagram used to illustrate the first topic of a conventional reflective optical rotary encoder.

[0036] Figure 13 This is a schematic diagram used to illustrate the second topic of a conventional reflective optical rotary encoder.

[0037] Symbol Explanation 1: Reflective optical unit; 10: Light-emitting element; 11: Light-emitting surface; 20: Reflector; 30: Light-receiving element; 31: Light-receiving surface; 32: Recess; 33: Protective component; 40: Substrate; 50: Wire; 60: Transparent electrode; 100: Optical rotary encoder; 110: Light-emitting element; 111: Light-emitting surface; 120: Code disk; 130: Light-receiving element; 131: Light-receiving surface; 140: Substrate; 200: Optical rotary encoder; 210: Light-emitting element; 220: Code disk 230: Light-receiving element; 231: Light-receiving surface; 240: Substrate; A: Distance; D1: Thickness; D2: Thickness; D3: Thickness; D4: Thickness; H1: First height; H2: Second height; L1: First optical path length; L2: Second optical path length; P1: Circuit pattern; P2: Circuit pattern; P3: Circuit pattern; S: Conductive material; S1: First surface; S2: Second surface; d1: First distance; d2: Second distance; d3: Third distance; d4: Fourth distance. Detailed Implementation

[0038] A more detailed explanation of the background and problems of existing technologies will be provided.

[0039] Encoders are known as devices for detecting the amount, direction, or angle of mechanical movement. Encoders are broadly classified into magnetic and optical types. Optical encoders are further divided into transmissive and reflective types. Transmissive encoders are superior in performance, but reflective encoders are advantageous in terms of cost and manufacturing. In recent years, the share of reflective encoders among optical encoders has been increasing.

[0040] An encoder is a device that converts mechanical movement, direction, or angle into electrical signals. Encoders are broadly classified into linear encoders and rotary encoders. A rotary encoder is a sensor device that converts rotational motion into electrical signals. Rotary encoders are used in a wide variety of machinery or devices, such as industrial robots, machine tools, and elevators.

[0041] Rotary encoders include transmissive rotary encoders, which have light-emitting elements and light-receiving elements arranged opposite each other, with a code disk that transmits / blocks light inserted into the space between the light-emitting and light-receiving elements. Alternatively, rotary encoders include reflective rotary encoders, which have light-emitting elements and light-receiving elements arranged on the same plane, with a code disk that reflects / blocks light positioned above the light-emitting and light-receiving elements.

[0042] Reflective rotary encoders have the following structure: the light-emitting element and the light-receiving element are arranged on the same plane, and a code disk that reflects / does not reflect light is set on it. Reflective rotary encoders have the following advantages: they are easy to miniaturize or thin, further simplifying the assembly process. Therefore, reflective rotary encoders are widely used in applications where space saving is particularly important, or in ultra-small actuators or collaborative robots.

[0043] Figure 10 This is a schematic diagram illustrating an example of the configuration of a conventional transmissive optical rotary encoder 200. The optical rotary encoder 200 includes a light-emitting element 210, a code disk 220, a light-receiving element 230, and a substrate 240. The light-receiving element 230 has a light-receiving surface 231 that receives light emitted from the light-emitting element 210 and transmitted through the code disk 220. In the transmissive optical rotary encoder 200, since the optical axis is a uniform straight line, it can support high resolution. However, the thickness D2 increases throughout the entire encoder, from the light-emitting element 210 to the substrate 240. Furthermore, it is necessary to align the light-emitting element 210, the code disk 220, and the light-receiving element 230 with each other.

[0044] Figure 11This is a schematic diagram illustrating an example of the configuration of a conventional reflective optical rotary encoder 100. The optical rotary encoder 100 includes a light-emitting element 110, a code disk 120, a light-receiving element 130, and a substrate 140. The light-receiving element 130 has a light-receiving surface 131 that receives light emitted from the light-emitting element 110 and reflected by the code disk 120. The reflective optical rotary encoder 100 can be thinned. The thickness D1 is reduced throughout the entire encoder, including from the code disk 120 to the substrate 140. On the other hand, in the reflective structure, the following two points are problematic.

[0045] Figure 12A This is a first schematic diagram used to illustrate the first subject of a conventional reflective optical rotary encoder 100. Figure 12B This is a second schematic diagram used to illustrate the first aspect of a conventional reflective optical rotary encoder 100. (Refer to...) Figure 12A and Figure 12B The first challenge of the conventional reflective optical rotary encoder 100 will be explained. The first challenge is to match the heights of the "light-emitting surface 111 of the light-emitting element 110" and the "light-receiving surface 131 of the light-receiving element 130" used in the reflective optical rotary encoder 100.

[0046] For example, such as Figure 12A As shown, if the heights of the emitting surface 111 and the receiving surface 131 are significantly different, the optical path length ratio changes according to the distance A between the receiving element 130 and the code disk 120. The "optical path length ratio" refers to, for example, the ratio of the optical path length between the emitting surface 111 and the code disk 120 to the optical path length between the code disk 120 and the receiving surface 131. If the optical path length ratio changes according to the distance A, the intensity, position, and incident angle of the light incident on the receiving surface 131 of the receiving element 130 all change, resulting in increased signal fluctuations.

[0047] The variation in distance A includes, for example, the variation that occurs in each individual optical rotary encoder 100 due to individual differences when the code disk 120 is configured in each of the plurality of optical rotary encoders 100. Alternatively, the variation in distance A may also include, for example, the variation caused by the normal rotational operation of the code disk 120 when using the optical rotary encoder 100, and may also include the variation caused by major external factors, including vibrations from the outside.

[0048] On the other hand, such as Figure 12B As shown, by setting the optical path length between the emitting surface 111 and the code disk 120 to the optical path length between the code disk 120 and the receiving surface 131 to a 1:1 ratio, the optical path length ratio remains constant at 1 even if the distance A changes. As a result, the impact of changes in distance A on the signal is reduced. That is, compared with... Figure 12AThe different configurations shown reduce signal fluctuations.

[0049] As mentioned above, regarding the first issue, in order to stably achieve a structure with an optical path length ratio close to 1, it is sought to reduce the difference between the height of the light-receiving surface 131 and the height of the light-emitting surface 111, as well as to reduce the tolerance of this height difference.

[0050] Figure 13 This is a schematic diagram illustrating a second problem of a conventional reflective optical rotary encoder 100. The second problem is to reduce the distance between the "light-emitting position of the light-emitting element 110" and the "light-receiving position of the light-receiving element 130". It is believed that the shorter the optical path length, i.e., the closer the light-emitting and light-receiving positions are, the stronger the signal strength and the better the signal-to-noise ratio (S / N ratio). In the case of assuming a structure where the light-emitting element 110 is arranged adjacent to the light-receiving position of the light-receiving element 130, the optical path length may become longer for the light-receiving surface 131, which is farther from the light-emitting element 110. Therefore, in this second problem, the aim is to reduce the distance between the light-emitting position of the light-emitting element 110 and the light-receiving position of the light-receiving element 130.

[0051] This disclosure relates to a reflective optical unit 1, which is used in conjunction with a reflector 20 (described later as a code disk) for an encoder, comprising a light-emitting element 10 and a light-receiving element 30. By using a thin-film light-emitting element 10, tolerances in the height direction can be reduced, thus lowering signal fluctuations. Furthermore, this disclosure relates to a reflective optical unit 1 that can increase signal strength by bringing the light-receiving position of the light-receiving element 30 and the light-emitting position of the light-emitting element 10 closer together. Moreover, this disclosure relates to a reflective optical unit 1 that can also avoid signal fluctuations caused by the driving wires of the light-emitting element 10.

[0052] Hereinafter, one embodiment of the present disclosure will be described with reference to the accompanying drawings. The numerical values ​​of various parameters, etc., described in the following description are merely examples and do not limit the scope of the present disclosure. The scope of the present disclosure should be determined solely based on the claims.

[0053] Figure 1A This is a perspective view schematically showing a first example of the configuration of a reflective optical unit 1 according to an embodiment of the present disclosure. Figure 1B It is Figure 1A The magnified image is obtained by enlarging the part I enclosed by a single dotted line. Figure 2 It schematically shows along Figure 1A The cross-sectional view of the section intercepted by arrow II-II. Figures 1A to 2 The illustration of the reflector 20, described later, of the reflective optical unit 1 is omitted. The reflector 20, for example... Figure 7B As shown in the diagram. (See reference.) Figures 1A to 2 The first example of the configuration and function of a reflective optical unit 1 according to one embodiment of the present disclosure will be described. In addition to a reflector 20, the reflective optical unit 1 also includes a light-emitting element 10, a light-receiving element 30, a substrate 40, and a wire 50.

[0054] The reflective optical unit 1 is used, for example, in an encoder. In this disclosure, an "encoder" includes a device that converts, for example, mechanical movement, direction, or angle into an electrical signal. An encoder may include, for example, a rotary encoder. This rotary encoder is a sensor device that converts rotary motion into an electrical signal. This rotary encoder can be used in a wide variety of machines or devices, such as industrial robots, machine tools, or elevators. The rotary encoder may be, for example, an optical reflective encoder. The encoder has a reflective optical unit 1. In this case, the reflector 20 may include a code disk.

[0055] The reflective optical unit 1, for example, has a stacked structure. In the reflective optical unit 1, the light-emitting element 10 and the light-receiving element 30 are located on the substrate 40. In the reflective optical unit 1, the substrate 40, the light-receiving element 30, and the light-emitting element 10 can be stacked sequentially. For example, the light-receiving element 30 can be located directly above the substrate 40. The light-emitting element 10 can be further located directly above the light-receiving element 30, which is located directly above the substrate 40. In the reflective optical unit 1, light is emitted from the light-emitting element 10 towards the light-receiving element 30 located on the opposite side of the substrate 40. Figure 7B The reflector 20 shown in the figure illuminates the light. The light from the light-emitting element 10 is reflected by the reflector 20 and detected by the light-receiving element 30, which is located on the same side as the light-emitting element 10 relative to the reflector 20.

[0056] As a concept for the reflective optical unit 1, instead of the conventional light-emitting element which typically has a height of 150 to 300 μm, a "thin-film shaped (and narrow-emitting area) light-emitting element 10" is mounted "near the light-receiving surface 31 of the light-receiving element 30". The reflective optical unit 1 is configured such that the distance to the light-receiving surface 31 of the light-receiving element 30 is minimized, for example, a thin-film shaped light-emitting element 10 with a thickness of less than 10 μm and a width of less than 200 μm for the emitting area. The reflective optical unit 1 uses the center of the plurality of light-receiving surfaces 31 as a candidate for the placement position of the light-emitting element 10 in such a way that light can effectively enter any one of the plurality of light-receiving surfaces 31.

[0057] The light-emitting element 10 includes, for example, an LED (Light-Emitting Diode) element or an LD (Laser Diode) element. LEDs include, for example, micro-LEDs or thin-film point light source LEDs. LDs include, for example, thin-film VCSELs (Vertical Cavity Surface Emitting Lasers). The light-emitting element 10 irradiates light toward the reflector 20 with a wavelength having high light sensitivity in the light-receiving element 30 and capable of being used for encoder-based signal processing. For example, the light-emitting surface 11 of the light-emitting element 10 is contained in a first surface S1 of the light-emitting element 10 facing the side opposite to the substrate 40.

[0058] The light-emitting element 10 has a thin-film shape. In this disclosure, "thin-film shape" includes, for example, a shape that is thin enough to be considered a film. The thin-film shape may, for example, include a shape with a thickness of 20 μm or less. The light-emitting element 10 may also have a thickness relative to the first optical path length between the light-emitting surface 11 and the reflective surface of the reflector 20, for example, less than 5%, more preferably less than 3%, and even more preferably less than 1%. The thickness of the light-emitting element 10 may, for example, be in the range of less than 20 μm. The thickness of the light-emitting element 10 is preferably in the range of 0.5 μm to 20 μm, more preferably in the range of 1 μm to 20 μm, and even more preferably in the range of 1 μm to 10 μm.

[0059] The light-emitting element 10 has a thin film thickness; alternatively, the width of the light-emitting surface 11 associated with the light-emitting region can be around several hundred μm. For example... Figure 1A and 1B As shown, the light-emitting element 10 can, for example, have a rectangular shape with both sides being approximately several hundred μm in diameter, or a square shape. The light-emitting element 10 is, for example, disposed at the center of the second surface S2 of the light-receiving element 30 facing the side opposite to the substrate 40. The light-emitting element 10 is located between one column of a plurality of light-receiving surfaces 31 arranged in rows. The plurality of light-receiving surfaces 31 are arranged in rows on both sides of the light-emitting element 10.

[0060] The edge of the light-emitting element 10 is directly electrically connected to the circuit pattern P1 on the second surface S2 of the light-receiving element 30 via a conductive material S without the use of wires 50. In this disclosure, the "conductive material S" includes, for example, solder or a thin-film electrode material (e.g., Au film or ITO film) formed together with an insulating film. Since the light-emitting element 10, having a thin-film shape, is located at approximately the same height as the circuit pattern P1 on the second surface S2, the edge of the light-emitting element 10 can be directly mounted to the circuit pattern P1 via the conductive material S, for example, by soldering or forming a thin-film electrode material (e.g., Au film or ITO film) together with an insulating film. The light-emitting element 10 is directly electrically connected to one end of the circuit pattern P1 via the conductive material S, and indirectly connected to the circuit pattern P2 on the substrate 40 via wires 50 from the other end of the circuit pattern P1. Thus, an electrical connection between the light-emitting element 10 and the substrate 40 is achieved. The conductive material S is only used in... Figure 1A and Figure 1B The figures shown are shown in the figures below and have been omitted in other figures for ease of illustration.

[0061] The light-receiving element 30 includes, for example, any detection element capable of detecting light emitted from the light-emitting element 10 and reflected by the reflector 20. This detection element includes, for example, a photodiode (PD). The photodiode includes, for example, a silicon (Si) PD. The light-receiving element 30 has a predetermined light-receiving sensitivity to the wavelength of light emitted from the light-emitting element 10, converts the light into an electrical signal, and outputs the electrical signal required for encoder-based signal processing. For example, the light-receiving surface 31 of the light-receiving element 30 is contained in a second surface S2 of the light-receiving element 30 facing the side opposite to the substrate 40.

[0062] The light-receiving element 30 can also be configured such that the width of the light-receiving surface 31 associated with the light-receiving area is about several hundred μm. The light-receiving surface 31 of the light-receiving element 30 can also have a rectangular shape, for example, with both sides being about several hundred μm in size. The light-receiving surface 31 of the light-receiving element 30 can be arranged relative to the light-emitting element 10 such that the side adjacent to the light-emitting element 10 is the short side and the side perpendicular to that side is the long side.

[0063] The light-receiving element 30 may have multiple light-receiving surfaces 31 on the second surface S2. For example, the light-receiving element 30 may also have multiple light-receiving surfaces 31 arranged in a row on both sides of the light-emitting element 10 disposed in the center of the second surface S2. Figure 2 As shown, the pair of light-receiving surfaces 31 located on both sides of the light-emitting element 10 can also be arranged symmetrically in the left-right direction relative to the light-emitting element 10. For example, the distance between the light-receiving surface 31 located on one side of the light-emitting element 10 and the distance between the light-receiving surface 31 located on the other side of the light-emitting element 10 and the light-emitting element 10 can also be the same.

[0064] The difference between the first height H1 and the second height H2 is less than or equal to the thickness of the light-emitting element 10. The first height H1 is the height of the first surface S1 of the light-emitting element 10 facing the side opposite to the substrate 40 relative to the substrate 40, and the second height H2 is the height of the second surface S2 of the light-receiving element 30 facing the side opposite to the substrate 40 relative to the substrate 40. For example, as... Figure 2 As shown, when the light-emitting element 10 is directly disposed on the second surface S2 of the light-receiving element 30, the difference between the first height H1 and the second height H2 is the same as the thickness of the light-emitting element 10. When the thickness of the light-emitting element 10 is 10 μm, this difference is 10 μm.

[0065] The tolerance between the first height H1 and the second height H2 is, for example, contained in the range of 0 μm to 5 μm. More preferably, this tolerance is contained in the range of 0 μm to 3 μm, and even more preferably, in the range of 0 μm to 1 μm. For example, when the thickness of the light-emitting element 10 is 10 μm, due to the individual differences in the encoder as a product when the reflective optical unit 1 is arranged in each of the plurality of encoders, this difference can also be contained in the range of 5 μm to 15 μm.

[0066] like Figure 1A and Figure 1B As shown, in addition to the circuit pattern P1 that is electrically connected to the edge of the light-emitting element 10 via a conductive material S, the light-receiving element 30 also has multiple circuit patterns P3 arranged around the edge of the light-receiving element 30 in a manner that surrounds multiple light-receiving surfaces 31. The multiple circuit patterns P3 are respectively electrically connected to the circuit pattern P2 on the substrate 40 via wires 50. Thus, an electrical connection between the light-receiving element 30 and the substrate 40 is achieved.

[0067] The substrate 40 includes, for example, any component that supports the light-emitting element 10 and the light-receiving element 30 and enables electrical connections to each element. The substrate 40 may include, for example, a printed circuit board (PCB) with excellent processability and mounting properties. Wiring patterns and electrodes are disposed on the surface of the substrate 40. For example, multiple circuit patterns P2 are disposed on the surface of the substrate 40. One of the multiple circuit patterns P2 is electrically connected to the light-emitting element 10 via a wire 50, a circuit pattern P1, and a conductive material S, as described above. Multiple of the multiple circuit patterns P2 are electrically connected to the circuit pattern P3 of the light-receiving element 30 via wires 50, as described above.

[0068] The wire 50 includes wires made of, for example, any conductive material. Materials include, for example, gold (Au), silver (Ag), or copper (Cu). The wire 50 may include, for example, an Au wire. The wire 50 is used, for example, when it is difficult to directly electrically connect the circuit pattern P3 of the light-receiving element 30, which has a predetermined thickness different from the light-emitting element 10 having a thin-film shape, and the circuit pattern P2 of the substrate 40, using a conductive material S. When the distance between the circuit pattern P3 of the light-receiving element 30 and the circuit pattern P2 of the substrate 40 is large, the wire 50 is arranged across the distance between the circuit pattern P3 of the light-receiving element 30 and the circuit pattern P2 of the substrate 40, serving to electrically connect them to each other.

[0069] Figure 3 This is a first cross-sectional view schematically showing a second example of the configuration of a reflective optical unit 1 according to an embodiment of the present disclosure. Figure 4 This is a second cross-sectional view schematically showing a second example of the configuration of a reflective optical unit 1 according to an embodiment of the present disclosure. Figure 3 Cross-sectional view and Figure 4 The cross-sectional views are respectively with Figure 2 The cross-sectional view corresponds to this. Figure 3 and Figure 4 The diagram of the reflector 20, described later, of the reflective optical unit 1 is omitted. The reflector 20, for example, is in... Figure 7B As shown in the diagram. (See reference.) Figure 3 and Figure 4 A second example of the configuration and function of the reflective optical unit 1 according to one embodiment of this disclosure will be described.

[0070] In the first example described above, the light-emitting element 10 is disposed on the flat portion of the second surface S2 of the light-receiving element 30, but the shape of the second surface S2 on which the light-emitting element 10 is disposed is not limited to a flat shape. For example, the light-receiving element 30 may have a recess 32 on the second surface S2 for disposing of the light-emitting element 10. That is, the shape of the second surface S2 on which the light-emitting element 10 is disposed may also be a concave shape.

[0071] The recess 32 may, for example, have a depth such that the difference between the first height H1 of the first surface S1 relative to the substrate 40 and the second height H2 of the second surface S2 relative to the substrate 40 is less than or equal to the thickness of the light-emitting element 10. For example, the recess 32 may also be configured with a depth less than twice the thickness of the light-emitting element 10. When the recess 32 is configured with the same depth as the thickness of the light-emitting element 10, the light-emitting surface 11 included in the first surface S1 and the light-receiving surface 31 included in the second surface S2 are at the same height relative to the substrate 40. For example, the light-emitting element 10 may also be disposed in the recess 32, which is a recess with a depth corresponding to the thickness of the light-emitting element 10.

[0072] As described above, the tolerance between the first height H1 and the second height H2 is, for example, within the range of 0 μm to 5 μm. For example, when the thickness of the light-emitting element 10 is 10 μm and the recess 32 is formed at the same depth as the thickness of the light-emitting element 10, the difference between the first height H1 and the second height H2 may also be included in the range of +5 μm to -5 μm due to the individual differences of the encoder as a product when the reflective optical unit 1 is arranged in each of the plurality of encoders.

[0073] like Figure 4 As shown, if the light-emitting element 10 is disposed in the recess 32, the light-emitting surface 11 is surrounded by the edge of the recess 32. Therefore, through Figure 3 and Figure 4 The processing of the recess 32 on the second surface S2 of the light-receiving element 30 as shown reduces the intensity of the light emitted from the light-emitting element 10 that is not reflected by the reflector 20 and directly incident on the light-receiving surface 31 from the light-emitting element 10.

[0074] Figure 5 This is a cross-sectional view schematically showing a third example of the configuration of a reflective optical unit 1 according to an embodiment of the present disclosure. Figure 5 The cross-sectional view corresponds to Figure 2 A cross-sectional view. In Figure 5 The diagram of the reflector 20, described later, of the reflective optical unit 1 is omitted. The reflector 20, for example, is in... Figure 7B As shown in the diagram. (See reference.) Figure 5 The third example of the configuration and function of the reflective optical unit 1 according to one embodiment of the present disclosure will be described in detail.

[0075] The reflective optical unit 1 may also include a protective member 33 of light-shielding resin disposed at the corner of the recess 32 of the light-receiving element 30. The protective member 33 may be configured to surround the light-emitting element 10 disposed in the recess 32. Therefore, by... Figure 5 The processing of the recess 32 on the second surface S2 of the light-receiving element 30 as shown, and the arrangement of the protective member 33 of the light-shielding resin, further reduce the intensity of the light emitted from the light-emitting element 10 that is not reflected by the reflector 20 and directly incident on the light-receiving surface 31 from the light-emitting element 10.

[0076] The protective member 33 can be used in combination with the recess 32 disposed on the second surface S2 of the light-receiving element 30, as in the third example described above, or it can be used alone without being combined with the recess 32. For example, the protective member 33 can also be disposed in a manner that surrounds the light-emitting element 10 when the light-emitting element 10 is disposed on the flat portion of the second surface S2 without the recess 32 being formed.

[0077] Figure 6This is a cross-sectional view schematically showing a fourth example of the configuration of a reflective optical unit 1 according to an embodiment of the present disclosure. Figure 6 The cross-sectional view corresponds to Figure 2 A cross-sectional view. In Figure 6 The diagram of the reflector 20, described later, of the reflective optical unit 1 is omitted. The reflector 20, for example, is in... Figure 7B As shown in the diagram. (See reference.) Figure 6 The following will mainly describe a fourth example of the configuration of the reflective optical unit 1 according to one embodiment of the present disclosure.

[0078] In the first to third examples described above, only a single light-emitting element 10 is disposed on the second surface S2 of the light-receiving element 30, but this is not a limitation. Multiple light-emitting elements 10 may also be disposed on the second surface S2 of the light-receiving element 30. In this case, the multiple light-emitting elements 10 of the reflective optical unit 1 can be close to each other. Figure 6 In this example, two light-emitting elements 10 are arranged close to each other on the second surface S2. For example, the distance between the two light-emitting elements 10 can be around tens of μm.

[0079] Figure 7A This is a cross-sectional view schematically showing a first example of the configuration of the reflective optical unit 1 of the comparative example of this disclosure. Figure 7B This is a cross-sectional view schematically showing a fifth example of the configuration of a reflective optical unit 1 according to an embodiment of the present disclosure. Figure 7A and Figure 7B The cross-sectional view corresponds to Figure 2 A cross-sectional view. In Figure 7A and Figure 7B The reflector 20 of the reflective optical unit 1 is clearly shown in the image. (Refer to...) Figure 7A and Figure 7B The fifth example of the configuration and function of the reflective optical unit 1 according to one embodiment of the present disclosure will be described.

[0080] like Figure 7B As shown, the reflector 20 is, for example, a code disk. The reflector 20 is located on the side opposite to the substrate 40, relative to the light-emitting element 10 and the light-receiving element 30. The reflector 20 is arranged so as to face the light-emitting surface 11 of the light-emitting element 10 and the light-receiving surface 31 of the light-receiving element 30. The reflector 20 is configured to be rotatable about a central axis.

[0081] The reflector 20 reflects light emitted from the light-emitting surface 11 of the light-emitting element 10 toward the light-receiving surface 31 of the light-receiving element 30. Figure 7BThe diagram shows a first optical path length L1 between the light-emitting surface 11 of the first surface S1 of the light-emitting element 10 and the reflective surface of the reflector 20, and a second optical path length L2 between the light-receiving surface 31 of the second surface S2 of the light-receiving element 30 and the reflective surface of the reflector 20. The error between the first optical path length L1 and the second optical path length L2 is, for example, contained in the range of 0% to 5%. More preferably, the error between the first optical path length L1 and the second optical path length L2 is contained in the range of 0% to 3%, and even more preferably, in the range of 0% to 1%.

[0082] The error between the first optical path length L1 and the second optical path length L2 refers, for example, to the ratio of the difference between the first optical path length L1 and the second optical path length L2 relative to either the first optical path length L1 or the second optical path length L2. The error between the first optical path length L1 and the second optical path length L2 can, for example, represent the degree to which the first optical path length L1 deviates from the thickness D3 of the light-emitting element 10 relative to the second optical path length L2. For instance, the smaller the thickness D3 of the light-emitting element 10 is relative to both the first optical path length L1 and the second optical path length L2, the smaller the error between the first optical path length L1 and the second optical path length L2.

[0083] The light-emitting element 10 has a thickness D3, which is, for example, small enough to be considered a film relative to each of the first optical path length L1 and the second optical path length L2. For example, in the case where the thickness D3 of the light-emitting element 10 having a thin-film shape is 10 μm, and the first optical path length L1 and the second optical path length L2 are each about several hundred μm to 1 mm, the light-emitting element 10 can also have a thickness D3 that is, for example, less than 5% of the first optical path length L1 and the second optical path length L2. The light-emitting element 10 can be considered a film that is sufficiently thin relative to each optical path length, which has a length of, for example, several hundred μm to about 1 mm.

[0084] By comparison Figure 7A and Figure 7B It can be understood that the reflective optical unit 1 reduces the tolerance of the height difference between the emitting surface 11 of the emitting element 10 and the receiving surface 31 of the receiving element 30. For example, in Figure 7A In the comparative example shown, consider a structure where the light-emitting element 10 is positioned next to the light-receiving element 30. In this case, the height difference between the light-emitting surface 11 of the light-emitting element 10 and the light-receiving surface 31 of the light-receiving element 30 is affected by the tolerances of both the thickness D3 of the light-emitting element 10 and the thickness D4 of the light-receiving element 30. For example, assuming the thicknesses of both the light-emitting element 10 and the light-receiving element 30 are approximately 200 μm, even with a tolerance of 10%, a difference of 20 μm × 2 = 40 μm could still occur.

[0085] On the other hand, Figure 7B In one embodiment of the reflective optical unit 1 shown, the light-emitting element 10 is disposed on the second surface S2 of the light-receiving element 30 and has a thin film shape, thereby having a very small thickness D3. Therefore, the heights of the light-emitting surface 11 of the light-emitting element 10 and the light-receiving surface 31 of the light-receiving element 30 are approximately the same. The light-emitting surface 11 of the light-emitting element 10, which is not in contact with the substrate 40, and the light-receiving surface 31 of the light-receiving element 30, which is not in contact with the substrate 40, are located on approximately the same plane. That is, the light-emitting surface 11 and the light-receiving surface 31 are located at approximately the same height.

[0086] Furthermore, since the thickness D3 of the light-emitting element 10 is small, the tolerance of the thickness D3 of the light-emitting element 10 also becomes smaller. For example, assuming the thickness of the light-emitting element 10 is about 10 μm, if the tolerance is 10%, the difference converges to 1 μm. As described above, the height difference between the light-emitting surface 11 of the light-emitting element 10 and the light-receiving surface 31 of the light-receiving element 30 is only affected by the small tolerance of the thickness D3 of the light-emitting element 10. As a result, the tolerance of this difference also becomes smaller. As described above, the tolerance of this difference can, for example, be contained in the range of 0 μm to 5 μm.

[0087] Figure 8A This is a cross-sectional view schematically showing a second example of the configuration of the reflective optical unit 1 of the comparative example of this disclosure. Figure 8B This is a cross-sectional view schematically showing a sixth example of the configuration of a reflective optical unit 1 according to an embodiment of the present disclosure. Figure 8A and Figure 8B The cross-sectional view corresponds to Figure 2 A cross-sectional view. In Figure 8A and Figure 8B The reflector 20 of the reflective optical unit 1 is clearly shown in the image. (Refer to...) Figure 8A and Figure 8B The sixth example of the configuration and function of the reflective optical unit 1 according to one embodiment of the present disclosure will be described.

[0088] If Figure 8A and Figure 8B By comparison, it can be understood that the reflective optical unit 1 reduces the distance between the light-emitting surface 11 of the light-emitting element 10 and the light-receiving surface 31 of the light-receiving element 30, thereby increasing the signal strength of the electrical signal required by the encoder. For example, in Figure 8AIn the comparative example shown, consider a structure where the light-emitting element 10 is positioned next to the light-receiving element 30. In this case, the distance between the light-receiving surface 31 of the light-receiving element 30 and the light-emitting surface 11 of the light-emitting element 10 is the sum of a first distance d1 extending from the end of the light-receiving surface 31 to the end of the light-receiving element 30, a second distance d2 between the light-receiving element 30 and the light-emitting element 10, and a third distance d3 extending from the end of the light-emitting element 10 to the end of the light-emitting surface 11. Assuming the first distance d1 is 100 μm, the second distance d2 is 150 μm, and the third distance d3 is 50 μm, the distance between the light-receiving surface 31 and the light-emitting surface 11 is 300 μm.

[0089] On the other hand, Figure 8B In one embodiment of the reflective optical unit 1 shown, the light-emitting element 10 has a thin-film shape, and the light-emitting surface 11 can be arranged substantially throughout the thin film of the light-emitting element 10. Furthermore, the light-emitting element 10 can be arranged near the light-receiving surface 31 directly above the light-receiving element 30. Therefore, the fourth distance d4 between the light-receiving surface 31 of the light-receiving element 30 and the light-emitting surface 11 of the light-emitting element 10 can also be less than 100 μm. For the reflective optical unit 1, since the fourth distance d4 between the light-emitting surface 11 of the light-emitting element 10 and the light-receiving surface 31 of the light-receiving element 30 is small, the light-emitting surface 11 and the light-receiving surface 31 are brought closer together, increasing the amount of light incident from the light-emitting surface 11 via the reflector 20 on the light-receiving surface 31. As a result, the reflective optical unit 1 improves the signal strength of the electrical signal required by the encoder.

[0090] Figure 9A This is a cross-sectional view schematically showing a third example of the configuration of the reflective optical unit 1 of the comparative example of this disclosure. Figure 9B This is a cross-sectional view schematically showing a seventh example of the configuration of a reflective optical unit 1 according to an embodiment of the present disclosure. Figure 9A and Figure 9B The cross-sectional view corresponds to Figure 2 A cross-sectional view. In Figure 9A and Figure 9B The reflector 20 of the reflective optical unit 1 is clearly shown in the image. (Refer to...) Figure 9A and Figure 9B The seventh example of the configuration and function of the reflective optical unit 1 according to one embodiment of the present disclosure will be described.

[0091] If Figure 9A and Figure 9B By comparison, it can be understood that the reflective optical unit 1 does not require wiring for the light-emitting element 10, and can also avoid the shadow cast by the wire 50 relative to the light-emitting surface 11 of the light-emitting element 10. For example, in Figure 9AIn the comparative example shown, consider a structure where the light-emitting element 10 is positioned next to the light-receiving element 30. In this case, a height difference is created between the light-emitting surface 11 of the light-emitting element 10 and the substrate 40. Therefore, a wire 50 is required, for example, as wiring for electrically connecting the light-emitting element 10 to the substrate 40. To prevent the wire 50 from casting shadows, the wire 50 needs to be positioned outside the light-emitting surface 11, which is the light-emitting area of ​​the light-emitting element 10, and on the opposite side to the light-receiving element 30.

[0092] On the other hand, Figure 9B In one embodiment of the reflective optical unit 1 shown, the light-emitting element 10 has a thin film shape with a very small thickness. Therefore, the reflective optical unit 1 can also achieve wiring using a transparent electrode 60 instead of wiring using a wire 50 after the light-emitting element 10 is mounted. In this case, the light-emitting element 10, through the transparent electrode 60 covering the entire surface of the light-emitting element 10, interacts with, for example... Figure 1A and Figure 1B The circuit pattern P1 shown is electrically connected on the second surface S2 of the light-receiving element 30. Thus, the reflective optical unit 1 can eliminate the influence of the wire 50 on the light-emitting surface 11 of the light-emitting element 10, and can arrange the light-receiving surface 31 on both sides sandwiching the light-emitting element 10. The reflective optical unit 1 can also avoid signal fluctuations caused by the wire 50 used to drive the light-emitting element 10.

[0093] As described above, according to the structure of this disclosure, it has the following multiple characteristic stages.

[0094] First, the reflective optical unit 1 uses a "thin-film shaped light-emitting element 10". By using the "thin-film shaped light-emitting element 10", the second surface S2 of the light-receiving element 30 and the first surface S1 of the light-emitting element 10 are located approximately on the same plane. As a result, even if the position of the reflector 20, which serves as the code disk, changes slightly up or down relative to the substrate 40, the reflective optical unit 1 can maintain a ratio of approximately 1:1 between the first optical path length L1 and the second optical path length L2. For example, the error between the first optical path length L1 and the second optical path length L2 is within the range of 0% to 5%. Therefore, the reflective optical unit 1 can also reduce the impact of errors on the electrical signal. The reflective optical unit 1 can reduce signal fluctuations.

[0095] Second, the reflective optical unit 1 defines the light-emitting position and the light-receiving position. The shorter the optical path length between each of the light-emitting surface 11 of the light-emitting element 10 and the light-receiving surface 31 of the light-receiving element 30 and the reflector 20, which serves as the code disk, the stronger the electrical signal strength and the higher the reliability of the measurement in the encoder. The reflective optical unit 1 can improve the electrical signal strength by reducing the distance between the light-emitting surface 11 of the light-emitting element 10 and the light-receiving surface 31 of the light-receiving element 30.

[0096] Third, the reflective optical unit 1 specifies the height tolerances of the light-emitting element 10 and the light-receiving element 30. For example, since the light-emitting element 10 is located directly above the light-receiving element 30, the height tolerance of the light-receiving element 30 will not affect the height difference between the light-receiving surface 31 and the light-emitting surface 11. In this case, only the height tolerance of the light-emitting element 10 affects the height difference. In order to achieve higher accuracy measurement than the prior art, the reflective optical unit 1 reduces the difference and tolerance between the first height H1 of the first surface S1 relative to the substrate 40 and the second height H2 of the second surface S2 relative to the substrate 40, thereby reducing signal fluctuations.

[0097] Conventional light-emitting elements have a height of approximately 200 μm, while the height (thickness D3) of the light-emitting element 10 in the reflective optical unit 1 of one embodiment of this disclosure is, for example, within the range of 0.5 μm to 20 μm. Therefore, the tolerance in the height direction of the light-emitting element 10 is sufficiently small compared to conventional light-emitting elements. In view of this, the reflective optical unit 1, compared to conventional structures, can reduce the tolerance of the difference between the first height H1 of the first surface S1 relative to the substrate 40 and the second height H2 of the second surface S2 relative to the substrate 40. For example, this tolerance can also be within the range of 0 μm to 5 μm.

[0098] Fourth, the reflective optical unit 1 does not require wiring in the light-emitting element 10. Since the reflective optical unit 1 uses a light-emitting element 10 with a thin-film shape, it is not necessary to directly connect the wire 50 to the light-emitting element 10. Instead, the end edge of the light-emitting element 10 and the circuit pattern P1 located on the second surface S2 can be directly electrically connected via a conductive material S without using the wire 50. Alternatively, the light-emitting element 10 can also be electrically connected to the circuit pattern P1 located on the second surface S2 via a transparent electrode 60 covering the entire surface of the light-emitting element 10.

[0099] As described above, the conductor 50 does not block the light emitted from the light-emitting element 10, thus the reflective optical unit 1 can configure the light-receiving surface 31 in any direction centered on the light-emitting element 10 to mitigate the degradation of the electrical signal. The reflective optical unit 1 can also configure the light-receiving surface 31 on both sides sandwiching the light-emitting element 10 without affecting the light-emitting state of the light-emitting element 10 due to the conductor 50. The reflective optical unit 1 can receive light through these light-receiving surfaces 31 without affecting the light-emitting state of the light-emitting element 10 due to the conductor 50.

[0100] like Figure 3 and Figure 4As shown, the light-receiving element 30 has a recess 32 on the second surface S2 for arranging the light-emitting element 10. Therefore, by adding processing to the recess 32 on the second surface S2, the reflective optical unit 1 can further reduce the height difference between the light-receiving surface 31 and the light-emitting surface 11. Furthermore, the processing of the recess 32 by the reflective optical unit 1 can reduce direct light incidence from the light-emitting surface 11 of the light-emitting element 10 onto the light-receiving surface 31. This effect is further amplified by the protective member 33 of the light-shielding resin disposed around the light-emitting element 10.

[0101] It will be apparent to those skilled in the art that this disclosure may be implemented in other predetermined ways besides the embodiments described above without departing from the spirit or essential characteristics of this disclosure. Therefore, the foregoing description is illustrative and not limiting. The scope of the disclosure is not defined by the foregoing description but by the appended claims. All modifications within their equivalents are included therein.

[0102] For example, the shape, pattern, size, arrangement, orientation, type, and number of each of the above-described components are not limited to those shown in the description and accompanying drawings. The shape, pattern, size, arrangement, orientation, type, and number of each component can be arbitrarily configured, as long as its function can be achieved. The constituent elements of the illustrated reflective optical unit 1 are functional concepts. The specific form of each constituent element is not limited to those shown in the drawings.

[0103] In the above embodiment, although the tolerance for the difference between the first height H1 and the second height H2 has been described as being within the range of 0 μm to 5 μm, it is not limited thereto. The tolerance for this difference may also be within a range larger than 5 μm.

[0104] In the above embodiment, although the reflective optical unit 1 has been described as having a reflective plate 20 that reflects light emitted from the light-emitting surface 11 of the light-emitting element 10 toward the light-receiving surface 31 of the light-receiving element 30, it is not limited thereto. The reflective plate 20 of the encoder does not need to be part of the reflective optical unit 1. That is, the reflective optical unit 1 itself may not have a reflective plate 20. The encoder may have a reflective optical unit 1 and a reflective plate 20 with a different configuration than the reflective optical unit 1.

[0105] In the above embodiment, although it was stated that the error between the first optical path length L1 and the second optical path length L2 is within the range of 0% to 5%, it is not limited thereto. The error can be within the range of greater than 5%.

[0106] In the above embodiment, although the case where the light-emitting element 10 is located directly above the light-receiving element 30 has been described, it is not limited to this. Any other arrangement is possible as long as the light-emitting element 10 and the light-receiving element 30 are located on the substrate 40. For example, both the light-emitting element 10 and the light-receiving element 30 may be located directly above the substrate 40. In this case, the light-receiving element 30 may have the same thin-film shape as the light-emitting element 10.

[0107] In the above embodiments, although the case where the edge of the light-emitting element 10 is directly electrically connected to the circuit pattern P1 located on the second surface S2 via a conductive material S without using a wire 50 has been described, it is not limited to this. The edge of the light-emitting element 10 and the circuit pattern P1 located on the second surface S2 can be electrically connected via a wire 50 instead of a conductive material S. Alternatively, the light-emitting element 10 can be directly electrically connected to the circuit pattern P2 on the substrate 40 via a wire 50 without using the circuit pattern P1.

[0108] In the above embodiment, although the case where the light-emitting element 10 is electrically connected to the circuit pattern P1 located on the second surface S2 via a transparent electrode 60 covering the entire surface of the light-emitting element 10 has been described, it is not limited thereto. The light-emitting element 10 can be electrically connected to the circuit pattern P1 via a wire 50 instead of the transparent electrode 60. Alternatively, the light-emitting element 10 can be electrically connected directly to the circuit pattern P2 on the substrate 40 via a wire 50 without using the circuit pattern P1.

[0109] In the above embodiment, although the light-receiving element 30 has been described with respect to having a recess 32 on the second surface S2 for arranging the light-emitting element 10, it is not limited thereto. The light-receiving element 30 may be configured to not have the recess 32 and the second surface S2 may be flat.

[0110] In the above embodiment, although a plurality of light-emitting elements 10 close to each other have been described for the reflective optical unit 1, it is not limited thereto. The plurality of light-emitting elements 10 may not be close to each other. Alternatively, the reflective optical unit 1 may not have a plurality of light-emitting elements 10, but only a single light-emitting element 10.

[0111] In the above embodiments, although the thickness of the light-emitting element 10 has been described as being in the range of 0.5 μm to 20 μm, it is not limited thereto. If the light-emitting element 10 has a thin film shape, the thickness of the light-emitting element 10 may be in the range of greater than 20 μm or less than 0.5 μm.

[0112] In the above embodiments, although the reflective optical unit 1 has been described for use in an encoder, it is not limited thereto. The reflective optical unit 1 can be used in any other device besides the encoder.

[0113] In the above embodiments, the encoder is described as including a rotary encoder, but is not limited thereto. The encoder may include other types of encoders different from rotary encoders. For example, the encoder may include a linear encoder. In this case, the reflector 20 may also include a reflective linear scale.

Claims

1. A reflective optical unit, characterized in that, have: Substrate; and The light-emitting element and the light-receiving element are located on the substrate. The difference between the first height and the second height is less than or equal to the thickness of the light-emitting element. The first height is the height of the first surface of the light-emitting element facing the side opposite to the substrate relative to the substrate, and the second height is the height of the second surface of the light-receiving element facing the side opposite to the substrate relative to the substrate. The light-emitting element has a thin-film shape.

2. The reflective optical unit according to claim 1, characterized in that, The tolerance of the difference is within the range of 0μm to 5μm.

3. The reflective optical unit according to claim 1, characterized in that, The reflective optical unit includes a reflector that reflects light emitted from the light-emitting surface of the light-emitting element toward the light-receiving surface of the light-receiving element. If the first optical path length between the light-emitting surface included in the first surface and the reflective surface of the reflector is set as L1, and the second optical path length between the light-receiving surface included in the second surface and the reflective surface is set as L2, then the error between L1 and L2 is within the range of 0% to 5%.

4. The reflective optical unit according to any one of claims 1 to 3, characterized in that, The light-receiving element is located directly above the substrate. The light-emitting element is located directly above the light-receiving element.

5. The reflective optical unit according to claim 4, characterized in that, The edge of the light-emitting element and the circuit pattern on the second surface are directly electrically connected by a conductive material without the use of wires.

6. The reflective optical unit according to claim 4, characterized in that, The light-emitting element is electrically connected to a circuit pattern located on the second surface via a transparent electrode covering the entire surface of the light-emitting element.

7. The reflective optical unit according to claim 4, characterized in that, The light-receiving element has a recess on the second surface where the light-emitting element is disposed.

8. The reflective optical unit according to any one of claims 1 to 3, characterized in that, The reflective optical unit has a plurality of light-emitting elements close to each other.

9. The reflective optical unit according to any one of claims 1 to 3, characterized in that, The thickness of the light-emitting element is within the range of 0.5μm to 20μm.

10. An encoder, characterized in that, The encoder has the reflective optical unit as described in claim 3.

11. The encoder according to claim 10, characterized in that, The encoder includes a rotary encoder. The reflector includes a code disk.

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