Optical module

Abstract

The present invention provides an optical module that simplifies the configuration while improving detection accuracy. [Solution] The optical module 4 comprises a support 11 having a bottom wall portion 18 and a side wall portion 19, a light-emitting element 13 disposed on the bottom wall portion 18, a light-transmitting member 21 disposed on the end face 19b of the side wall portion 19, and a resin member 22 formed on the surface 21a of the light-transmitting member 21. The surface 21a has an inner region R1 and an outer region R2 facing the end face 19b. The resin member 22 is integrally formed over the inner region R1 and the outer region R2. The refractive index of the resin member 22 with respect to light having the central wavelength of light emitted from the light-emitting element 13 is smaller than the refractive index of the light-transmitting member 21 with respect to light having the same central wavelength. The light-transmitting member 21 is joined to the side wall portion 19 by a portion formed on the outer region R2 of the resin member 22.

Description

Technical Field

[0001] The present invention relates to an optical module for an encoder applied to a reflective encoder, and to a reflective encoder. Background Art

[0002] Patent Document 1 describes a reflective encoder. This reflective encoder includes: a base portion on which a light receiving element and a light emitting element are arranged; a wall portion arranged on the base portion so as to surround the light receiving element and the light emitting element; and a mask plate joined onto the wall portion. In this reflective encoder, light emitted from the light emitting element and reflected by a rotating plate passes through a slit formed in the mask plate and enters the light receiving element. Prior Art Literature Patent Literature

[0003] Patent Document 1 Japanese Unexamined Patent Application Publication No. 2019-158851 Summary of the Invention Problems to be Solved by the Invention

[0004] The reflective encoder as described above is required to have a simplified configuration and also required to have improved detection accuracy. Accordingly, an object of the present invention is to provide an optical module for an encoder and a reflective encoder that can simplify the configuration and can improve detection accuracy. Means for Solving the Problems

[0005] The optical module for encoders of the present invention is an optical module applicable to a reflective encoder, and comprises a support having a bottom wall and a side wall that surrounds a region on the bottom wall when viewed from the thickness direction of the bottom wall; a light-receiving element and a light-emitting element disposed on the bottom wall so as to be surrounded by the side wall; a light-transmitting member disposed on the end face of the side wall opposite to the bottom wall so as to cover the space surrounded by the side wall and having a surface facing the bottom wall; and a resin member formed on the surface of the light-transmitting member, wherein the surface of the light-transmitting member has an inner region facing the light-emitting element and an outer region surrounding the inner region and facing the end face, the resin member is integrally formed over the inner region and the outer region so as to have a portion facing the light-emitting element, the refractive index of the resin member for light having the central wavelength of the light emitted from the light-emitting element is smaller than the refractive index of the light-transmitting member for light having the central wavelength, and the light-transmitting member is joined to the side wall by a portion formed on the outer region of the resin member.

[0006] In this encoder optical module, a resin member is formed on the surface facing the bottom wall of the light-transmitting member, and this resin member is integrally formed across the inner and outer regions of the surface of the light-transmitting member so that it has a portion facing the light-emitting element. The refractive index of the resin member for light with the central wavelength of the light emitted from the light-emitting element is smaller than the refractive index of the light-transmitting member for light with the same central wavelength. This allows the resin member to function as an anti-reflective layer, suppressing the reflection of light from the light-emitting element by the light-transmitting member. As a result, it is possible to suppress the incident of light reflected from the surface of the light-transmitting member as noise light on the photodetector, thereby improving detection accuracy. Furthermore, the light-transmitting member is joined to the side wall by a portion formed on the outer region of the resin member. This eliminates the need to provide a separate joining member between the light-transmitting member and the side wall, in addition to the resin member that functions as an anti-reflective layer, thus simplifying the configuration. Moreover, when this encoder optical module is applied to a reflective encoder, the distance from the photodetector and light-emitting element to the rotating plate can be shortened compared to, for example, when the light-transmitting member is arranged on the side wall via an anti-reflective layer and a joining member. When the distance from the light-receiving element and light-emitting element to the rotating plate is short, the spreading of light between the light-receiving element and light-emitting element and the rotating plate can be suppressed. As a result, the amount of light received by the light-receiving element can be increased, and the detection accuracy can be improved. Furthermore, if the bonding member is a resin adhesive that does not transmit light, the resin adhesive may protrude into the inside of the side wall, and the surface of the light-transmitting member may be obstructed by the protruding resin adhesive, potentially reducing the light transmission area. In contrast, since this optical module does not require a bonding member, such a reduction in the light transmission area can be suppressed, and the detection accuracy can be improved. Therefore, this encoder optical module simplifies the configuration and improves detection accuracy.

[0007] The resin component may be formed over the entire inner region. In this case, the reflection of light emitted from the light-emitting element and spread out onto the surface of the light-transmitting component can be more reliably suppressed, further improving detection accuracy.

[0008] When light having the central wavelength of light emitted from a light-emitting element is incident on the interface between the light-transmitting member and the resin member at an incident angle of 45 degrees from the resin member side, the reflectance at the interface may be smaller than the reflectance at the interface when light having the same central wavelength is incident on the interface at an incident angle of 45 degrees from the light-transmitting member side. In this case, it is possible to more reliably suppress the reflection at the interface of light emitted from the light-emitting element and incident on the interface between the light-transmitting member and the resin member at an angle other than perpendicular to the interface. As a result, detection accuracy can be further improved.

[0009] The light transmittance of the resin material to light with wavelengths between 800 nm and 900 nm may be 90% or higher. In this case, when a light-emitting element that emits light with such wavelengths is used, the resin material can be effectively transmitted to the light emitted from the light-emitting element. As a result, detection accuracy can be further improved.

[0010] The resin component may be an adhesive film. In this case, since the heated resin component hardens in a relatively short time, the light-transmitting component can be precisely bonded to the end face of the side wall using the resin component.

[0011] The resin component may be a die attach film. In this case, since the heated resin component hardens in a relatively short time, the light-transmitting component can be precisely bonded to the end face of the side wall using the resin component.

[0012] The light-emitting element may be placed on a light-receiving element. In this case, when the optical module for the encoder is applied to a reflective encoder, the distance between the light-emitting element and the rotating plate can be shortened, further improving detection accuracy.

[0013] The encoder optical module further comprises a fiber optic plate having an input surface formed by one end face of a plurality of optical fibers and an output surface formed by the other end faces of a plurality of optical fibers, the light-receiving element having a light-receiving surface facing away from the bottom wall, and the fiber optic plate may be arranged on the light-receiving element such that the output surface faces the light-receiving surface. In this case, the light incident on the input surface can be reliably guided to the light-receiving surface, and the detection accuracy can be further improved.

[0014] The encoder optical module may further include an adhesive film positioned between the light-receiving surface and the output surface, which bonds a fiber optic plate to the light-receiving element. In this case, since the heated adhesive film hardens in a relatively short time, the fiber optic plate can be precisely bonded to the light-receiving element by the adhesive film.

[0015] An anti-reflective layer may be formed on the surface of the light-transmitting member opposite to the bottom wall. In this case, the reflection of light on the surface of the light-transmitting member opposite to the bottom wall can be suppressed, and the amount of light received by the light-receiving element can be increased. As a result, detection accuracy can be further improved.

[0016] The encoder optical module may further include a wire connected to the bottom wall and the light-receiving element, and a resin member covering the wire. In this case, the wire can be protected from oil and physical external forces that may be scattered when using a reflective encoder.

[0017] The reflective encoder of the present invention comprises a rotating plate having a light reflection pattern and an optical module for the encoder. For the reasons mentioned above, this reflective encoder allows for a simplified configuration and improved detection accuracy. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide an optical module for an encoder and a reflective encoder that can simplify the configuration and improve detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] [Figure 1] It is a perspective view of a reflective encoder according to an embodiment. [Figure 2] It is a cross-sectional view of the optical module shown in FIG. 1. [Figure 3] It is a diagram showing the propagation path of light in a simulation related to reflectance. [Figure 4] It is a graph showing the results of a simulation related to reflectance. [Figure 5] (a) and (b) are cross-sectional views of optical modules according to modified examples. DESCRIPTION OF EMBODIMENTS

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals are used for identical or corresponding elements, and duplicate descriptions are omitted. [Configuration of Reflective Encoder]

[0021] As shown in FIG. 1, the reflective encoder 1 includes a rotating shaft 2, a rotating plate 3, an optical module (optical module for encoder) 4, and a processing unit 5. The rotating shaft 2 rotates about an axis A as a center line. The reflective encoder 1 is, for example, an absolute rotary encoder, and is a device for detecting the absolute angle of a measurement object connected to the rotating shaft 2.

[0022] The rotating plate 3 is fixed to the rotation shaft 2 and rotates together with the rotation shaft 2. The rotating plate 3 is a so-called code wheel. The rotating plate 3 is formed in a disc shape and is attached to the rotation shaft 2 at its center so as to be positioned perpendicular to axis A. The rotating plate 3 has a main surface 3a facing the optical module 4. A light reflection pattern 3b is formed on the main surface 3a, which reflects light emitted from the optical module 4. The light reflection pattern 3b represents a predetermined pattern such as a Gray code. The light reflection pattern 3b is a light reflective film formed of a metal such as Cr. The parts of the rotating plate 3 where the light reflection pattern 3b is not formed are configured to reduce light reflection.

[0023] The optical module 4 is an encoder optical module applied to the reflective encoder 1 and is fixed so as to face a part of the main surface 3a of the rotating plate 3. That is, the optical module 4 faces a part of the light reflection pattern 3b. The optical module 4 has a light-receiving element 12 and a light-emitting element 13, which will be described later. The processing unit 5 is, for example, a signal processing circuit that encodes the light detection result in the light-receiving element 12 of the optical module 4 and outputs a Gray code that represents the absolute value of the rotation angle of the rotating axis 2.

[0024] In the reflective encoder 1, when the light reflection pattern 3b is positioned on the optical axis of the light emitted from the light-emitting element 13 of the optical module 4, the light is reflected by the light reflection pattern 3b, and the reflected light enters the light-receiving element 12 of the optical module 4. On the other hand, if the light reflection pattern 3b is not positioned on the optical axis of the light emitted from the light-emitting element 13, the light from the light-emitting element 13 passes through the rotating plate 3 and does not enter the light-receiving element 12. [Optical module configuration]

[0025] As shown in Figure 2, the optical module 4 comprises a support 11, a light-receiving element 12, a light-emitting element 13, a fiber optic plate 14, an adhesive film 15, a wire 16, a resin member 17, a light-transmitting member 21, a resin member 22, and an anti-reflective layer 23.

[0026] The support 11 has a bottom wall portion 18 which is a substrate member, and a side wall portion 19 disposed on the bottom wall portion 18. The bottom wall portion 18 has a rectangular plate shape and a flat surface 18a. The bottom wall portion 18 may be formed of, for example, glass epoxy resin. The bottom wall portion 18 has wiring (not shown) to which the wire 16 is connected. Hereinafter, the thickness direction of the bottom wall portion 18 (the direction perpendicular to the surface 18a) will be referred to as direction D1, and the direction perpendicular to direction D1 will be referred to as direction D2.

[0027] The side wall portion 19 surrounds the area on the bottom wall portion 18 when viewed from the thickness direction of the bottom wall portion 18. The side wall portion 19 is provided along the outer edge of the surface 18a and has a rectangular frame shape when viewed from direction D1. The side wall portion 19 may be formed from the same material as the bottom wall portion 18, for example, glass epoxy resin. The side wall portion 19 has an inner surface 19a and an end surface 19b located on the opposite side from the bottom wall portion 18.

[0028] The light-receiving element 12 is a rectangular plate-shaped light-receiving chip that detects light reflected by the light reflection pattern 3b. The light-receiving element 12 has a light-receiving section 121. The light-receiving section 121 is, for example, a photodiode or a photodiode array and has a light-receiving surface 121a on the upper surface 12a side of the light-receiving element 12. The light-receiving surface 121a constitutes a part of the upper surface 12a. The light-receiving element 12 is arranged on the surface 18a such that it is surrounded by side walls 19 and the light-receiving surface 121a faces away from the bottom wall 18. The light-receiving element 12 converts light incident on the light-receiving surface 121a into an electrical signal and outputs the converted electrical signal to the processing unit 5. The light-receiving element 12 has wiring (not shown) to which a wire 16 for outputting the electrical signal is connected.

[0029] The light-emitting element 13 is a light source that emits light toward the rotating plate 3, and is, for example, an LED (Light Emitting Diode). The light-emitting element 13 has a light-emitting surface 13a from which light is emitted. The light-emitting element 13 is arranged on the upper surface 12a of the light-receiving element 12 such that it is surrounded by the side walls 19 and the light-emitting surface 13a faces away from the bottom wall 18. In this embodiment, the light-emitting element 13 is located in the central part of the upper surface 12a. In this example, the light-emitting element 13 is located between two light-receiving elements 12 aligned in direction D2. The light-emitting element 13 emits light having a wavelength of, for example, 800 nm or more and 900 nm or less. In this example, the light-emitting element 13 emits light having a wavelength of about 850 nm.

[0030] A fiber optic plate (hereinafter also referred to as "FOP") 14 is an optical component formed by bundling together multiple optical fibers. The FOP 14 contains, for example, tens of millions of optical fibers having a diameter of several nanometers to tens of nanometers. The FOP 14 has a rectangular parallelepiped shape and has an input surface 14a and an output surface 14b. The input surface 14a is composed of one end face of the multiple optical fibers contained in the FOP 14, and the output surface 14b is composed of the other end faces of the same multiple optical fibers. In this embodiment, the input surface 14a and the output surface 14b are parallel to each other and face opposite directions in direction D1.

[0031] The FOP14 is positioned on the photodetector 12 such that its input surface 14a and output surface 14b are parallel to the photodetector 12's light-receiving surface 121a, and its output surface 14b faces the light-receiving surface 121a. Light incident on the input surface 14a of the FOP14 propagates through each optical fiber constituting the FOP14 and is emitted from the output surface 14b toward the light-receiving surface 121a. The light incident on the input surface 14a is emitted from the output surface 14b without spreading within the FOP14.

[0032] The adhesive film 15 is positioned between the light-receiving surface 121a and the output surface 14b, and bonds the FOP 14 to the light-receiving element 12. The adhesive film 15 is in contact with both the light-receiving surface 121a and the output surface 14b. When viewed from direction D1, the outer edge of the adhesive film 15 overlaps with the outer edge of the FOP 14, and the adhesive film 15 does not protrude beyond the FOP 14. The adhesive film 15 may be, for example, a die attach film. A die attach film is formed in a film shape and can bond objects to both sides. In this example, one side of the die attach film is bonded to the light-receiving surface 121a, and the other side is bonded to the output surface 14b. The die attach film is bonded to the object to be bonded, for example, by heating and curing. The die attach film may also be used, for example, to fix the substrate when cutting (dicing) the substrate that will become the FOP 14 during the manufacturing of the optical module 4. In this case, the die attach film is first attached to the surface of the substrate. A dicing tape is provided on the surface of the die attach film opposite to the substrate, and the dicing tape secures the substrate to the base (e.g., a dicing frame) on which it is placed during cutting. After the cutting process is complete, the dicing tape is peeled off from the die attach film.

[0033] Wire 16 is a bonding wire connected to the bottom wall portion 18 and the light-receiving element 12. One end of wire 16 is connected to the exposed portion on the surface 18a of the wiring of the bottom wall portion 18, and the other end of wire 16 is connected to the exposed portion on the upper surface 12a of the wiring of the light-receiving element 12. Wire 16 is curved so as to be convex toward the opposite side of the bottom wall portion 18 (the side on which the light-receiving element 12 is located relative to the bottom wall portion 18).

[0034] The resin member 17 is positioned on the surface 18a of the bottom wall portion 18 and covers the wire 16. In this embodiment, the resin member 17 covers the entire wire 16. That is, the wire 16 is not exposed from the resin member 17. The resin member 17 is positioned on both sides of the light-receiving element 12 in direction D2. The resin member 17 is in contact with the surface 18a of the bottom wall portion 18, the upper surface 12a and side surface 12b of the light-receiving element 12, the outer edge of the adhesive film 15, and the outer edge of the FOP 14. The resin member 17 does not extend to the peripheral edge of the surface 18a and is not in contact with the inner surface 19a of the side wall portion 19. The peripheral edge of the surface 18a is the inner portion of the surface 18a adjacent to the side wall portion 19. The peripheral edge of the surface 18a is exposed from the resin member 17.

[0035] The light-transmitting member 21 is positioned on the end face 19b of the side wall portion 19 so as to cover the space enclosed by the side wall portion 19. The light-transmitting member 21 has, for example, a rectangular plate shape and has a surface 21a facing the bottom wall portion 18 and a surface 21b located on the opposite side of the bottom wall portion 18. The light-transmitting member 21 is made of a light-transmitting material such as glass. The thickness of the light-transmitting member 21 may be, for example, about 0.3 mm.

[0036] The surface 21a of the light-transmitting member 21 has an inner region R1 facing the light-emitting element 13 and an outer region R2 surrounding the inner region R1 and facing the end face 19b. When viewed from direction D1, the inner region R1 is located inside the inner surface 19a of the side wall portion 19 and in this embodiment has a rectangular shape. When viewed from direction D1, the outer region R2 overlaps with the end face 19b and in this embodiment has a rectangular frame shape. The inner region R1 and the outer region R2 are continuous flat regions.

[0037] The resin member 22 is formed on the surface 21a of the light-transmitting member 21. More specifically, the resin member 22 is integrally formed over the inner region R1 and the outer region R2 such that it has a portion facing the light-emitting element 13. When viewed from direction D1, the resin member 22 overlaps with the light-emitting surface 13a of the light-emitting element 13. In this embodiment, the resin member 22 is formed over the entire surface 21a. That is, the resin member 22 is formed over the entire inner region R1 and the entire outer region R2. The resin member 22 is made of a light-transmitting resin material (for example, silicone resin or acrylic resin). The light transmittance of the resin member 22 for light emitted from the light-emitting element 13 (for example, light having a wavelength of 800 nm to 900 nm) is, for example, 90% or more. The thickness of the resin member 22 may be, for example, about 30 μm. The resin member 22 may be a thermosetting resin or a thermoplastic resin.

[0038] The resin member 22 has a surface 22a facing the bottom wall portion 18 and a surface 22b located on the opposite side of the bottom wall portion 18. The portion of surface 22a facing the end face 19b of the side wall portion 19 is in contact with the end face 19b, and the entire surface 22b is in contact with the surface 21a of the light-transmitting member 21. The light-transmitting member 21 is joined to the side wall portion 19 by the resin member 22, more specifically by a portion formed on the outer region R2 of the resin member 22. The resin member 22 is made of an adhesive film, such as a die-attach film. This die-attach film, like the die-attach film that constitutes the adhesive film 15, may be used, for example, to fix the substrate to a base when cutting (dicing) the substrate that will become the light-transmitting member 21 during the manufacturing of the optical module 4. In this case, the die-attach film is first attached to the surface of the substrate. A dicing tape is provided on the surface of the die-attach film opposite to the substrate, and the substrate is fixed to the base on which it is placed when cutting by the dicing tape. After the cutting process is complete, the dicing tape is peeled off the die attach film.

[0039] Light emitted from the light-emitting element 13 enters the resin member 22 from the surface 22a side, passes through the interface S (surfaces 22b and 21a) between the resin member 22 and the light-transmitting member 21, and enters the light-transmitting member 21. The refractive index of the resin member 22 with respect to light having the central wavelength of the light emitted from the light-emitting element 13 is smaller than the refractive index of the light-transmitting member 21 with respect to light having the same central wavelength. In other words, at the interface S, the light from the light-emitting element 13 enters from the member with the smaller refractive index (resin member 22) to the member with the larger refractive index (light-transmitting member 21). Therefore, the resin member 22 functions as an anti-reflective layer for light entering the light-transmitting member 21 from the light-emitting element 13 side.

[0040] The anti-reflective layer 23 is formed as a film on the surface 21b of the light-transmitting member 21 and prevents light reflection on the surface 21b. The anti-reflective layer 23 is formed over the entire surface 21b. The thickness of the anti-reflective layer 23 may be, for example, about 3 μm.

[0041] Referring to Figures 3 and 4, the reflectance of light at the interface S between the resin member 22 and the light-transmitting member 21 will be explained. The reflectance when light is incident on the interface S was simulated by changing the conditions (direction and angle of incidence of light). In Figure 3, the arrows indicating incident light are labeled "IN", the arrows indicating reflected light are labeled "R", and the arrows indicating transmitted light are labeled "T".

[0042] As shown in Figure 3, under condition A, light was incident on the interface S from the resin member 22 side at an incident angle of 0°, and under condition B, light was incident on the interface S from the resin member 22 side at an incident angle of 45°. Condition B corresponds to the case where light that has spread from the light-emitting element 13 to the resin member 22 is incident on the interface S. Under condition C, light was incident on the interface S from the light-transmitting member 21 side at an incident angle of 0°, and under condition D, light was incident on the interface S from the light-transmitting member 21 side at an incident angle of 45°. Condition D corresponds to the case where light that has spread from the light reflection pattern 3b of the rotating plate 3 to the light-transmitting member 21 is incident on the interface S. In this simulation, the refractive index of the light-transmitting member 21 was set to 1.50 and the refractive index of the resin member 22 was set to 1.40.

[0043] Figure 4 shows the simulation results of reflectance when the wavelength of incident light is varied in the range of 400 nm to 1200 nm under each condition. The results for conditions A and C were in agreement and are therefore shown as a single overlapping solid line in Figure 4. As shown in Figure 4, for example, in the wavelength band from 800 nm to 900 nm, the reflectance was approximately 0.015% under conditions A and C, approximately 0.025% under condition B, and approximately 0.030% under condition D.

[0044] Furthermore, at all wavelengths simulated, the reflectance under condition B was smaller than the reflectance under condition D. From these simulation results, it can be seen that in the optical module 4, the reflectance at interface S (hereinafter also referred to as reflectance X1) when light with the central wavelength emitted from the light-emitting element 13 is incident at the interface S from the resin member 22 side at an incident angle of 45 degrees is smaller than the reflectance at interface S (hereinafter also referred to as reflectance X2) when light with the same central wavelength is incident at the interface S from the light-transmitting member 21 side at an incident angle of 45 degrees. In other words, the optical module 4 is configured such that reflectance X1 is smaller than reflectance X2. [Mechanism of Action and Effects]

[0045] As described above, in the optical module 4, a resin member 22 is formed on the surface 21a of the light-transmitting member 21 that faces the bottom wall portion 18. The resin member 22 is integrally formed across the inner region R1 and the outer region R2 of the surface 21a so that it has a portion facing the light-emitting element 13. The refractive index of the resin member 22 with respect to light having the central wavelength of the light emitted from the light-emitting element 13 is smaller than the refractive index of the light-transmitting member 21 with respect to light having the same central wavelength. This allows the resin member 22 to function as an anti-reflective layer, suppressing the reflection of light from the light-emitting element 13 by the light-transmitting member 21. As a result, it is possible to suppress the incident light reflected from the surface 21a as noise light on the photodetector 12, thereby improving detection accuracy. Furthermore, the presence of the resin member 22 also suppresses reflection at the surface 21a of light that is reflected by the light reflection pattern 3b and returns to the optical module 4. As a result, the amount of light incident on the photodetector 12 can be increased, thereby improving detection accuracy. The light-transmitting member 21 is joined to the side wall portion 19 by a portion formed on the outer region R2 of the resin member 22. This eliminates the need to provide a bonding member (e.g., resin adhesive) between the light-transmitting member 21 and the side wall portion 19, separate from the resin member 22 which functions as an anti-reflective layer, thus simplifying the configuration. Furthermore, when the optical module 4 is applied to the reflective encoder 1, the distance from the light-receiving element 12 and light-emitting element 13 to the rotating plate 3 can be shortened compared to, for example, when the light-transmitting member 21 is arranged on the side wall portion 19 via an anti-reflective layer and a bonding member. A shorter distance from the light-receiving element 12 and light-emitting element 13 to the rotating plate 3 suppresses the spreading of light between the light-receiving element 12 and light-emitting element 13 and the rotating plate 3. As a result, the amount of light received by the light-receiving element 12 can be increased, improving detection accuracy. Furthermore, if the joining material is a resin adhesive that does not transmit light, the resin adhesive may protrude into the side wall portion 19, and the surface 21a of the light-transmitting member 21 may be obstructed by the protruding resin adhesive, potentially reducing the light transmission area.In contrast, since the optical module 4 does not require a bonding member, it is possible to suppress such a reduction in the light transmission area and improve detection accuracy. Therefore, the optical module 4 allows for a simplified configuration and improved detection accuracy.

[0046] The resin member 22 is formed over the entire inner region R1. This makes it possible to more reliably suppress the reflection of light emitted from the light-emitting element 13 and spread out on the surface 21a of the light-transmitting member 21, thereby further improving detection accuracy.

[0047] When light having the central wavelength of light emitted from the light-emitting element 13 is incident on the interface S between the light-transmitting member 21 and the resin member 22 from the resin member 22 side at an incident angle of 45 degrees, the reflectance X1 at the interface S is smaller than the reflectance X2 at the interface S when light having the same central wavelength is incident on the interface S from the light-transmitting member 21 side at an incident angle of 45 degrees. This makes it possible to more reliably suppress the reflection at the interface S of light emitted from the light-emitting element 13 that is incident on the interface S at an angle other than perpendicular to it. In other words, by making the reflectance X1 smaller than the reflectance X2, the incidence of noise light (light reflected from the surface 21a of the light going out from the optical module 4) on the photodetector 12 is suppressed. As a result, the detection accuracy can be further improved.

[0048] The light transmittance of the resin member 22 for light with wavelengths between 800 nm and 900 nm is 90% or more. This allows the light emitted from the light-emitting element 13 to pass through the resin member 22 well when using a light-emitting element 13 that emits light with these wavelengths. As a result, detection accuracy can be further improved.

[0049] The resin member 22 is an adhesive film (die attach film). As a result, the heated resin member 22 hardens in a relatively short time, allowing the light-transmitting member 21 to be accurately bonded to the end face 19b of the side wall portion 19 by the resin member 22. That is, for example, if the resin member 22 is not an adhesive film but a resin member that takes time to harden after heating, there is a risk that the position of the light-transmitting member 21 may shift while the resin material is hardening. In contrast, if the resin member 22 is an adhesive film, the heated resin member 22 hardens in a relatively short time, so such displacement of the light-transmitting member 21 can be suppressed, and the light-transmitting member 21 can be accurately bonded to the side wall portion 19 by the resin member 22. As a result, the yield of the optical module 4 can be improved.

[0050] The light-emitting element 13 is positioned on the light-receiving element 12. This allows the distance between the light-emitting element 13 and the rotating plate 3 to be shortened when the optical module 4 is applied to the reflective encoder 1, thereby further improving detection accuracy.

[0051] The optical module 4 further comprises an FOP 14 having an input surface 14a formed by one end face of a plurality of optical fibers and an output surface 14b formed by the other end faces of a plurality of optical fibers. The photodetector 12 has a photodetector surface 121a facing away from the bottom wall 18, and the FOP 14 is positioned on the photodetector 12 such that the output surface 14b faces the photodetector surface 121a. This ensures that light incident on the input surface 14a is reliably guided to the photodetector surface 121a, further improving detection accuracy.

[0052] The optical module 4 is positioned between the light-receiving surface 121a and the output surface 14b and includes an adhesive film 15 for bonding the FOP 14 to the light-receiving element 12. As a result, the heated adhesive film 15 hardens in a relatively short time, allowing the FOP 14 to be bonded to the light-receiving element 12 with high precision. That is, for example, if the component used to bond the FOP 14 to the light-receiving element 12 were a resin component that takes time to harden after heating, rather than an adhesive film 15, there is a risk that the position of the FOP 14 may shift while the resin material is hardening. In contrast, when the component used to bond the FOP 14 to the light-receiving element 12 is an adhesive film 15, the heated adhesive film 15 hardens in a relatively short time, which can suppress such displacement of the FOP 14, and the FOP 14 can be bonded to the light-receiving element 12 with high precision. As a result, the yield of the optical module 4 can be improved.

[0053] An anti-reflective layer 23 is formed on the surface 21b of the light-transmitting member 21 opposite to the bottom wall portion 18. This suppresses light reflection on the surface 21b, increasing the amount of light received by the light-receiving element 12. As a result, detection accuracy can be further improved.

[0054] The optical module 4 includes a wire 16 connected to the bottom wall 18 and the light-receiving element 12, and a resin member 17 covering the wire 16. This protects the wire 16 from oil and physical external forces that may be scattered when the reflective encoder 1 is in use. [Differentiation]

[0055] The optical module 4 may be configured as shown in the first modified example in Figure 5(a) or the second modified example in Figure 5(b). In the first modified example, the optical module 4 does not include the FOP 14, the adhesive film 15, and the resin member 17. Therefore, the light-receiving surface 121a is exposed on the upper surface 12a of the light-receiving element 12, and light transmitted through the resin member 22 is directly incident on the light-receiving surface 121a. In addition, the wire 16 is exposed without being covered by the resin member 17.

[0056] This first modification also allows for a simplified configuration and improved detection accuracy, similar to the above embodiment. Furthermore, in the first modification, the optical module 4 does not include the FOP 14, adhesive film 15, and resin member 17, thus further simplifying the configuration of the optical module 4.

[0057] In the second modified example shown in Figure 5(b), the optical module 4 does not include the FOP 14 and the adhesive film 15. Therefore, the light-receiving surface 121a is exposed on the upper surface 12a of the light-receiving element 12, and light transmitted through the resin member 22 is directly incident on the light-receiving surface 121a. In this modified example, the optical module 4 also includes a pair of light-receiving elements 12 arranged side by side in direction D2. The light-emitting element 13 is positioned between the pair of light-receiving elements 12. The position of the light-emitting surface 13a in direction D1 coincides with the position of the light-receiving surface 121a.

[0058] This second modification also simplifies the configuration and improves detection accuracy, similar to the above embodiment. Furthermore, in the second modification, the optical module 4 does not include the FOP 14 and the adhesive film 15, thus further simplifying the configuration of the optical module 4.

[0059] The present invention is not limited to the embodiments and modifications described above. For example, the materials and shapes of each component are not limited to those described above, but can be made from a variety of materials and shapes. For example, the resin member 22 only needs to be formed in a part of the inner region R1 such that it has a portion facing the light-emitting element 13, and does not need to be formed over the entire inner region R1. The resin member 22 only needs to be formed in a part of the outer region R2 such that the light-transmitting member 21 can be joined to the side wall portion 19, and does not need to be formed over the entire outer region R2. The resin member 22 may be formed by curing a resin material that has been heated and melted. The light transmittance of the resin member 22 for light having a wavelength of 800 nm or more and 900 nm or less may be less than 90%.

[0060] The resin member 17 does not have to cover the entire wire 16, but may cover only a part of the wire 16. The anti-reflective layer 23 may be formed on a part of the surface 21b of the light-transmitting member 21, or it may be omitted.

[0061] The features of the above embodiments and modified examples may be combined with each other. For example, in the first modified example shown in Figure 5(a), the optical module 4 may include the FOP 14 and the adhesive film 15. In the first modified example, the optical module 4 may include the resin member 17. In the second modified example shown in Figure 5(b), the optical module 4 may include the FOP 14 and the adhesive film 15. In the second modified example, the optical module 4 may not include the resin member 17.

[0062] The number of light-receiving sections 121 (light-receiving surfaces 121a) of the light-receiving element 12 is not limited and may be one or more. The light-receiving element 12 may be connected to the wiring of the bottom wall portion 18 via bumps instead of wires 16. [Explanation of Symbols]

[0063] 1...Reflective encoder, 3...Rotating plate, 3b...Light reflection pattern, 4...Optical module (optical module for encoder), 11...Support, 12...Photodetector, 13...Light-emitting element, 14...FOP (Fiber Optic Plate), 14a...Input surface, 14b...Output surface, 15...Adhesive film, 16...Wire, 17...Resin component, 18...Bottom wall, 18a...Surface, 19...Side wall, 19b...End face, 21...Light-transmitting component, 21a, 21b...Surface, 22...Resin component, 23...Anti-reflective layer, 121a...Photodetector surface, D1, D2...Direction, R1...Inner region, R2...Outer region, S...Interface.

Claims

1. A support having a bottom wall and a side wall that surrounds the area on the bottom wall when viewed from the thickness direction of the bottom wall, A light-emitting element is placed on the bottom wall so as to be surrounded by the side wall, A light-transmitting member is positioned on the end face of the side wall opposite to the bottom wall so as to cover the space enclosed by the side wall, and has a surface facing the bottom wall. The light-transmitting member comprises a resin member formed on the surface thereof, The surface of the light-transmitting member has an inner region facing the light-emitting element and an outer region surrounding the inner region and facing the end face. The resin member is integrally formed over the inner region and the outer region such that it has a portion facing the light-emitting element. The refractive index of the resin member with respect to light having the central wavelength of the light emitted from the light-emitting element is smaller than the refractive index of the light-transmitting member with respect to light having the central wavelength. An optical module in which the light-transmitting member is joined to the side wall by a portion formed on the outer region of the resin member.

2. The optical module according to claim 1, wherein the resin member is formed over the entire inner region.

3. The optical module according to claim 1 or 2, wherein the reflectance at the interface when light having the central wavelength is incident on the interface between the light-transmitting member and the resin member from the resin member side at an incident angle of 45 degrees is smaller than the reflectance at the interface when light having the central wavelength is incident on the interface from the light-transmitting member side at an incident angle of 45 degrees.

4. The optical module according to any one of claims 1 to 3, wherein the light transmittance of the resin member for light having a wavelength of 800 nm or more and 900 nm or less is 90% or more.

5. The optical module according to any one of claims 1 to 4, wherein the resin member is an adhesive film.

6. The optical module according to any one of claims 1 to 5, wherein the resin member is a die attach film.

7. The optical module according to any one of claims 1 to 6, wherein an anti-reflective layer is formed on the surface of the light-transmitting member opposite to the bottom wall portion.

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