JPWO2019162998A1 - Absolute encoder - Google Patents

Abstract

The absolute encoder includes an optical scale having an optical pattern, a light emitting element (31) for irradiating the optical scale with light, and a light receiving element (32) for receiving reflected light from the optical scale as a light transmitting resin (33A). The module package (300B), which includes a module package (300B) covered with a light receiving element (32) and a control unit that calculates an absolute rotation angle of the optical scale based on a signal output according to the reflected light. At the center of the light emitting surface (310) of the light emitting element (31) and the light receiving surface (320) of the light emitting element (31) exposed on the surface of the light transmissive resin (33A) facing the optical scale. A light-shielding resin (34B) passing through an intermediate position between and is arranged.

Description

  The present invention relates to an absolute encoder that detects an absolute rotation angle of a measurement object.

  One of the rotary encoders for detecting the absolute rotation angle of the object to be measured is an absolute encoder. An absolute encoder is an encoder that calculates an absolute rotation angle of an optical scale based on an optical signal reflected by an optical pattern on the optical scale and incident on a light receiving element. In the absolute encoder, when an unnecessary light beam other than the light beam used for calculating the absolute rotation angle is incident on the light receiving element, the detection accuracy of the absolute rotation angle is reduced. Therefore, it is desired to remove the unnecessary light beam.

  In the optical encoder disclosed in Patent Document 1, a light source, a photodetector, and a light source slit are sealed in a package, and a light shielding portion is formed at one end of the light source slit. With this configuration, the optical encoder disclosed in Patent Literature 1 prevents unnecessary light rays from traveling at the light shielding portion.

JP 2007-333667 A

  However, in the above-described conventional technique, it is not possible to suppress a decrease in angle detection accuracy due to multiple reflection between a package and an optical scale. The multiple reflection between the package and the optical scale is a phenomenon in which a light beam emitted from a light source is reflected by the optical scale, reflected by the surface of the package, and further reflected by the optical scale. The detection accuracy is degraded when the multiple reflected light enters the photodetector. Since the amount of light and the pattern of the light beam due to the multiple reflection change according to the rotation of the optical scale, it is difficult to remove the light beam by the arithmetic unit. For this reason, Patent Literature 1 has a problem that the absolute rotation angle of the measurement target cannot be detected with high accuracy.

  The present invention has been made in view of the above, and an object of the present invention is to provide an absolute encoder that can accurately detect an absolute rotation angle of an object to be measured.

  In order to solve the above-described problems and achieve the object, an absolute encoder of the present invention includes an optical scale having an optical pattern, a light-emitting element that irradiates light to the optical scale, and a light-receiving element that receives reflected light from the optical scale. And a control unit for calculating an absolute rotation angle of the optical scale based on a signal output from the light receiving element according to the reflected light. Further, the absolute encoder of the present invention is configured such that the module package is exposed on the surface of the light-transmitting resin facing the optical scale, and has an intermediate position between the center of the light-emitting surface of the light-emitting element and the center of the light-receiving surface of the light-receiving element. A light-shielding part that passes is arranged.

  The absolute encoder according to the present invention has an effect that the absolute rotation angle of the object to be measured can be accurately detected.

FIG. 1 is a diagram showing a configuration of an absolute encoder according to a first embodiment of the present invention. Sectional view showing the configuration of the module package according to the first embodiment. Top view showing the configuration of the module package according to the first embodiment. FIG. 2 is a block diagram illustrating a configuration of an angle calculation unit included in the absolute encoder according to the first embodiment. FIG. 4 is a diagram showing a waveform example of a signal received from the light receiving element by the angle calculation unit of the absolute encoder according to the first embodiment. FIG. 5 is a diagram showing a waveform of FIG. 5 corrected to have a uniform distribution. FIG. 6 is a diagram for explaining a method of calculating a coarse absolute rotation angle from the waveform shown in FIG. FIG. 7 is a view for explaining a method of calculating a fine absolute rotation angle from the coarse absolute rotation angle described in FIG. Diagram for explaining an example of stray light generated by a module package of a comparative example FIG. 4 is a diagram for explaining a path of a light ray in the module package according to the first embodiment; FIG. 7 is a diagram for explaining how the module package according to the first embodiment prevents multiple reflected light from entering a light receiving element. FIG. 5 is a diagram illustrating an example of a waveform of a signal detected by the light receiving element of the module package according to the first embodiment The figure which shows the example of the waveform of the signal detected by the light receiving element of the module package of a comparative example FIG. 7 is a diagram for explaining an arrangement position of a light shielding resin included in the module package according to the first embodiment. FIG. 9 is a view for explaining a third example of stray light generated by the module package of the comparative example. FIG. 3 is a diagram for explaining a dimensional relationship of components included in the module package according to the first embodiment. FIG. 8 is a diagram illustrating a first configuration example of a module package according to a second embodiment; FIG. 9 is a diagram illustrating a second configuration example of the module package according to the second embodiment;

  Hereinafter, an absolute encoder according to an embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited by these embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a configuration of the absolute encoder according to the first embodiment of the present invention. The absolute encoder 1 is a device that detects a rotation angle of a rotating body that is an object to be measured, and includes an optical scale 2, a module package 300, and a control unit 4. The rotation angle detected by the absolute encoder 1 is an absolute rotation angle. In FIG. 1, the upper surface of the module package 300, which is the surface facing the optical scale 2, is shown on the lower side, and the bottom surface of the module package 300 is shown on the upper side.

  The optical scale 2 is connected to a rotating shaft 5 provided in a rotating device such as a motor, and rotates according to the rotation of the rotating shaft 5. The optical scale 2 is configured using a disk-shaped member. The optical scale 2 includes, on the upper surface of a disk-shaped member, a reflective portion 201 which is a linear pattern indicating “bright” of light and dark, and a non-reflective portion 202 which is a linear pattern indicating “dark”. Have optical patterns 200 arranged alternately.

  The reflecting portion 201 is a portion that reflects a light beam from the light emitting element 31 described later, and the non-reflecting portion 202 is a portion that absorbs or scatters a light beam from the light emitting element 31. A plurality of reflectors 201 are arranged in a direction from the center of the disk-shaped member toward the outer periphery. Further, a plurality of non-reflective portions 202 are arranged in a direction from the center of the disk-shaped member toward the outer periphery. In other words, the plurality of reflecting portions 201 and the plurality of non-reflecting portions 202 are arranged such that one end of the linear shape faces the center of the optical pattern 200 and the other end faces the outer direction of the optical pattern 200.

  The non-reflection unit 202 is disposed between the reflection units 201, and the reflection unit 201 is disposed between the non-reflection units 202. In the optical scale 2, the reflection units 201 and the non-reflection units 202 are alternately arranged such that the reflection units 201 and the non-reflection units 202 are arranged radially in the annular region of the outer periphery of the disc-shaped member. . The reflection part 201 and the non-reflection part 202 have various dimensional widths. In other words, the reflection units 201 are arranged at various intervals, and the non-reflection units 202 are arranged at various intervals.

  Since the optical pattern 200 is a pattern in which the reflecting portion 201 and the non-reflecting portion 202 are arranged at various intervals, when the rotating optical pattern 200 is irradiated with a light beam, reflection and non-reflection of the light beam are reflected. This is repeated according to the arrangement interval of the portion 201 and the non-reflective portion 202. Thereby, the reflection unit 201 and the non-reflection unit 202 function to modulate a light intensity distribution projected on the light receiving element 32 described later.

  The optical scale 2 is provided with only one track having an optical pattern 200 composed of a reflection part 201 and a non-reflection part 202. The reflection unit 201 and the non-reflection unit 202 are arranged at intervals characterizing the rotation angle of the optical scale 2. As described above, the optical scale 2 has the optical pattern 200 unique to the rotation angle. As an arrangement pattern of the reflection unit 201 and the non-reflection unit 202, for example, a pseudo random code pattern such as an M sequence is used.

  The optical scale 2 is formed from a metal substrate such as stainless steel, for example. When the optical pattern 200 is formed, the non-reflective portion 202 is formed on the surface of the metal base by plating technology or the like, and the reflective portion 201 is formed by mirror-finishing the metal base. Note that the optical pattern 200 may be formed by any method as long as the reflection portion 201 and the non-reflection portion 202 can be formed.

  The module package 300 is a light emitting and receiving module including a light emitting element 31 having a light emitting function and a light receiving element 32 having a light receiving function. The module package 300 is arranged above the optical pattern 200 so as to face the optical pattern 200. The module package 300 detects, among the light emitted from the light emitting element 31, light reflected by the optical pattern 200 and entering the light receiving element 32, and outputs a signal corresponding to the detected light to the control unit 4. .

  The control unit 4 is connected to the light receiving element 32 at a later stage than the light receiving element 32. The control unit 4 includes an angle calculation unit 41 and a light emission amount adjustment unit 42. The angle calculator 41 calculates an absolute rotation angle of the optical scale 2 based on a signal output from the light receiving element 32 included in the module package 300. The absolute rotation angle calculated by the angle calculation unit 41 corresponds to the rotation position of the rotation shaft 5. As described above, the angle calculation unit 41 calculates the rotation position of the rotation shaft 5 based on the signal corresponding to the encoded optical pattern 200. The angle calculation unit 41 outputs the absolute rotation angle indicating the position data of the rotating shaft 5 to an external device as position data. The light emission amount adjusting unit 42 adjusts the light emission amount of the light emitted from the light emitting element 31 based on the signal output from the light receiving element 32.

  As described above, in the absolute encoder 1, the angle calculation unit 41 calculates the absolute rotation angle from the signal corresponding to the light beam incident on the light receiving element 32. The control unit 4 may control the rotation of the measurement target based on the absolute rotation angle. Since the absolute encoder 1 does not need to integrate the pulse signals output from the light receiving element 32, it does not need to return to the origin when the power is turned on, and can start up quickly.

  FIG. 2 is a cross-sectional view illustrating the configuration of the module package according to the first embodiment. FIG. 3 is a top view illustrating the configuration of the module package according to the first embodiment. 2 and 3 show a configuration of a module package 300A which is an example of the module package 300.

  2, the upper surface of the module package 300A facing the optical pattern 200 is shown on the lower side, and the bottom surface of the module package 300A is shown on the upper side. Also, in FIGS. 9 to 11 and FIGS. 15 to 18 described later, the upper surface of the module package is shown on the lower side, and the bottom surface of the module package is shown on the upper side. In FIG. 2, hatching of the package substrate 30A and the light transmitting resin 33A is omitted. Also, in FIGS. 9 to 11 and FIGS. 15 to 18 described below, hatching of the package substrate and the light transmitting resin is omitted. FIG. 3 is a top view of the module package 300A, which is hatched to clarify correspondence with the cross-sectional view of FIG.

  The module package 300A includes a package substrate 30A, a light emitting element 31, a light receiving element 32, a light transmitting resin 33A, and a light shielding resin 34A as a light shielding part. In the following description, for convenience of description, the direction in which the top and bottom surfaces of the package substrate 30A are arranged may be referred to as a horizontal direction, and the direction perpendicular to the top and bottom surfaces of the package substrate 30A may be referred to as a vertical direction.

  The package substrate 30A is a substrate on which the light emitting element 31 and the light receiving element 32 are mounted, and is connected to an encoder substrate (not shown). The encoder board is a board that executes various processes at a stage subsequent to the module package 300A, and has the control unit 4 disposed therein. Specifically, the encoder board has a processing circuit that executes the processing of the control unit 4. The upper surface of the package substrate 30A has a rectangular shape, and terminals are provided on all four sides. Each terminal is connected to the encoder board. For the terminals provided on the package substrate 30A, through-holes on the end faces or back electrodes are applied. By providing terminals on all four sides of the package substrate 30A, mounting accuracy of the light emitting element 31 and the light receiving element 32 is improved.

  The package substrate 30A has a rectangular upper surface, and the light emitting element 31 and the light receiving element 32 are arranged on the rectangular upper surface. It is desirable that the package substrate 30A be formed of a substrate similar to the encoder substrate. The encoder board is composed of, for example, a glass epoxy board. In this case, it is desirable that the package substrate 30A is also formed of a glass epoxy substrate.

  The light emitting element 31 is an element that emits light, and irradiates the optical scale 2 with light. For example, a near-infrared point light source LED (Light Emitting Diode) is applied to the light emitting element 31. The light emitting element 31 has a light emitting surface 310 disposed on an upper surface thereof, and emits light from the light emitting surface 310. The light emitting element 31 is joined to the package substrate 30A such that the light emitting surface 310 is in the horizontal direction.

  The light receiving element 32 is an element that receives light, and receives light reflected from the optical scale 2. As the light receiving element 32, an imaging device such as a CMOS (Complementary Metal Oxide Semiconductor) image sensor or a CCD (Charge Coupled Device) image sensor, which is composed of a set of pixels arranged one-dimensionally, is applied. The light receiving element 32 has a light receiving surface 320 disposed on an upper surface thereof, and receives light at the light receiving surface 320. The light receiving element 32 is joined to the package substrate 30A such that the light receiving surface 320 is in a horizontal direction.

  The light receiving element 32 outputs a signal corresponding to the light reflected from the optical scale 2. Specifically, the light receiving element 32 converts light received on the light receiving surface 320 into an analog voltage signal, and further converts the analog voltage signal into an A / D (Analog-to-Digital) conversion built in the light receiving element 32. The signal is converted into a digital signal by the device and output to the control unit 4 at the subsequent stage. Here, illustration of the A / D converter is omitted. The signal output from the A / D converter to the control unit 4 is a signal corresponding to the light reflected by the optical scale 2 and received by the light receiving element 32. Therefore, the signal received by the control unit 4 corresponds to the rotational position of the optical scale 2.

  The light transmitting resin 33A is formed so as to cover the upper surface of the package substrate 30A. Therefore, the bottom surface and the top surface of the light transmissive resin 33A have a rectangular shape. The light transmitting resin 33A covers the light emitting element 31 and the light receiving element 32 on the package substrate 30A in order to protect the light emitting element 31 and the light receiving element 32. The light transmissive resin 33A is made of, for example, an epoxy resin in order to match the linear expansion coefficient with the package substrate 30A.

  The light-shielding resin 34A is a member for suppressing the progress of stray light, which is an unnecessary light beam, and is made of an epoxy resin or the like, like the light-transmitting resin 33A. Stray light, which is unnecessary light, is light that is not desired to be incident on the light receiving element 32. An example of unnecessary light is light that is Fresnel-reflected at the interface between the light-transmitting resin 33A and the outside. The light-shielding resin 34 </ b> A absorbs or scatters light that does not want to be incident on the light receiving element 32, of the light emitted from the light emitting element 31. The light absorbed or scattered by the light-shielding resin 34A includes light emitted from the light emitting element 31, light emitted from the light emitting element 31 and reflected in the light transmitting resin 33A, and light emitted from the light emitting element 31. This is light that has been multiple-reflected between the package substrate 30A and the optical scale 2.

  The light-shielding resin 34A has a plate-like shape, and is disposed between the light emitting element 31 and the light receiving element 32 such that the plate-like front surface and the back surface are in the vertical direction. Specifically, the light-shielding resin 34A is arranged so as to separate the region where the light emitting element 31 is arranged from the region where the light receiving element 32 is arranged. That is, as shown in FIGS. 2 and 3, a region 420 on the left side of the light transmitting resin 33A in which the light emitting element 31 is disposed, and a region 421 on the right side of the light transmitting resin 33A in which the light receiving element 32 is disposed. The light-shielding resin 34A is arranged so as to be divided. In this case, a light-shielding resin 34A is formed on the package substrate 30A so that the light-transmitting resin 33A on the light emitting element 31 side and the light transmitting resin 33A on the light receiving element 32 are not connected. In FIG. 2, the first horizontal surface of the light-shielding resin 34A is in the same plane as the upper surface of the light-transmitting resin 33A, and the second horizontal surface of the light-shielding resin 34A is the light-transmitting resin. The case where it is in the same plane as the bottom surface of 33A is shown. Since the horizontal first surface of the light-shielding resin 34A is in the same plane as the upper surface of the light-transmitting resin 33A, the light-shielding resin 34A is exposed on the upper surface of the module package 300A. In other words, the light-shielding resin 34A is exposed from the light-transmitting resin 33A on the surface of the light-transmitting resin 33A facing the optical scale 2.

  The light-shielding resin 34A is arranged so that the light emitted from the light emitting element 31 to the optical pattern 200 does not shield the light that is desired to be incident on the light receiving element 32. That is, the light-shielding resin 34A is arranged so that the path of the light beam to be incident on the light receiving element 32 does not pass through the light-shielding resin 34A. In the module package 300A, the light-shielding resin 34A is arranged so that the front and back surfaces of the plate-like light-shielding resin 34A are perpendicular to the upper surface of the package substrate 30A.

  By the way, it is known that the glass epoxy substrate transmits a part of light such as near infrared rays. For this reason, when a glass epoxy substrate is applied to the package substrate 30A, the light beam emitted from the light emitting element 31 is transmitted directly or reflected in the light transmitting resin 33A to the package substrate 30A, and is unnecessary for the light receiving element 32. Could arrive as a light beam. In such a case, a black glass epoxy substrate may be applied to the package substrate 30A. Applying a metal film, a black resist, or a combination of these to the surface of the glass epoxy substrate so that light does not enter the glass epoxy substrate or propagate the light inside the glass epoxy substrate can prevent unnecessary light from reaching. It is effective in preventing. Note that a method using another material may be applied as long as the same effect as the method using these materials can be obtained.

  Here, the configuration of the angle calculation unit 41 will be described. FIG. 4 is a block diagram illustrating a configuration of an angle calculation unit included in the absolute encoder according to the first embodiment. The angle calculation unit 41 includes a light amount distribution correction unit 411, an edge detection unit 412, a coarse detection unit 413, a high precision detection unit 414, and a rotation angle detection unit 415.

  The signal output from the light receiving element 32 is sent to the light amount distribution correction unit 411. Accordingly, the light amount distribution correction unit 411 receives a signal from the light receiving element 32. The waveform of the signal that the light receiving element 32 inputs to the light amount distribution correction unit 411 is, for example, a waveform as shown in FIG. 5 in which the horizontal axis represents the pixel position and the vertical axis represents the signal intensity.

  FIG. 5 is a diagram illustrating an example of a waveform of a signal received from the light receiving element by the angle calculation unit of the absolute encoder according to the first embodiment. The horizontal axis of the graph shown in FIG. 5 is a pixel, and the vertical axis is the signal intensity. In the graphs shown in FIGS. 6 to 8, 12 and 13, which will be described later, similarly to the graph of FIG. 5, the horizontal axis represents pixels, and the vertical axis represents signal intensity.

  The level 1 signal 14 in FIG. 5 corresponds to the pattern at the reflection section 201 of the optical scale 2, and the level 0 signal 15 corresponds to the pattern at the non-reflection section 202 of the optical scale 2.

  The signal intensity of the level 1 signal 14 and the level 0 signal 15 becomes non-uniform for each pixel due to the light amount distribution of the light emitting element 31 itself, the gain variation of each pixel of the light receiving element 32, and the like. Therefore, the light amount distribution correction unit 411 corrects a distribution in which the maximum value of the signal intensity is not uniform to a distribution in which the maximum value of the signal intensity is uniform. Here, the light amount distribution correction unit 411 corrects the signal intensity shown in FIG. 5 to the signal intensity shown in FIG.

  FIG. 6 is a diagram showing a waveform obtained by correcting the waveform shown in FIG. 5 into a uniform distribution. As shown in FIG. 6, the light amount distribution correction unit 411 corrects the level 1 signal 14 and the level 0 signal 15 so that the maximum value of the signal intensity for each pixel becomes uniform. In other words, the light amount distribution correction unit 411 corrects the signal waveform such that the level 1 signal 14 is the same for each pixel and the level 0 signal 15 is the same for each pixel. In FIG. 6, the corrected waveform is shown as a corrected waveform 16.

  The correction method by the light amount distribution correction unit 411 may be any method as long as it is a method of making the light amount distribution uniform. The light quantity distribution correction unit 411 sends the corrected waveform 16 to the edge detection unit 412.

  The edge detection unit 412 calculates a pixel value whose signal intensity matches a preset threshold level 17 for each edge based on the corrected waveform 16. The edge detection unit 412 sends the calculated pixel value to the coarse detection unit 413 as an edge pixel value.

  The coarse detection unit 413 decodes a bit pattern projected on the light receiving element 32 from the optical pattern 200 of the optical scale 2 based on the edge pixel value, and calculates a coarse absolute rotation angle. Here, a method of calculating a coarse absolute rotation angle will be described with reference to FIG.

  FIG. 7 is a diagram for explaining a method of calculating a coarse absolute rotation angle from the waveform shown in FIG. In FIG. 7, a bit string corresponding to the corrected waveform 16 is indicated by a bit string 18. The coarse detection unit 413 converts the corrected waveform 16 into a bit string 18 of “1” or “0” based on the position of the edge indicated by the edge pixel value, as shown in FIG. Further, the coarse detection unit 413 refers to a look-up table 19 stored in advance in a memory (not shown) of the control unit 4 and obtains a coarse absolute rotation angle 100 from a code that matches the bit string 18. The lookup table 19 is a table that stores a bit string corresponding to the optical pattern 200. The coarse detection unit 413 sends the coarse absolute rotation angle 100 to the high precision detection unit 414.

  The high-accuracy detection unit 414 calculates the amount of phase shift of the pattern projected on the light receiving element 32 with high accuracy based on the coarse absolute rotation angle 100. The coarse absolute rotation angle 100 obtained by the coarse detection unit 413 is the absolute rotation angle 100 of the optical scale 2 in bit units. Therefore, the high-accuracy detection unit 414 calculates a fine absolute rotation angle by detecting the amount of phase shift from the reference pixel, which is the reference pixel, to the position of the closest edge pixel.

  FIG. 8 is a diagram for explaining a method of calculating a fine absolute rotation angle from the coarse absolute rotation angle described in FIG. As shown in FIG. 8, the high-precision detection unit 414 detects the phase shift amount 20 from the reference pixel 21 to the edge pixel position 22 that is the position of the edge pixel closest to the reference pixel 21. The reference pixel 21 is a pixel used as a reference when calculating a fine absolute rotation angle, and may be any pixel. The phase shift amount 20 corresponds to the difference between the position of the reference pixel 21 and the edge pixel position 22. The high precision detection unit 414 sends the coarse absolute rotation angle 100 and the phase shift amount 20 to the rotation angle detection unit 415.

  The rotation angle detection unit 415 calculates an absolute rotation angle finer than one bit unit of the optical scale 2 based on the phase shift amount 20. Specifically, the rotation angle detection unit 415 adds the coarse absolute rotation angle 100 calculated by the coarse detection unit 413 and the phase shift amount 20 calculated by the high-precision detection unit 414 to obtain a fine absolute rotation angle. calculate. The rotation angle detection unit 415 outputs the calculated fine absolute rotation angle as position data to an external device.

  Thus, the absolute encoder 1 receives the light reflected by the optical pattern 200 of the optical scale 2 among the light emitted from the light emitting element 31 by the light receiving element 32 and calculates the absolute rotation angle from the light quantity distribution pattern of the received light. Is detected. At this time, if stray light, which is an unnecessary light ray, enters the light receiving element 32, the signal quality of the light ray received by the light receiving element 32 deteriorates, and an error is superimposed on the edge pixel position 22 detected by the edge detection unit 412. For this reason, an error is superimposed on the absolute rotation angle. In order to detect the absolute rotation angle with high accuracy, it is necessary to suppress stray light, which is an unnecessary light beam. This stray light is an unnecessary light ray and causes deterioration in the detection accuracy of the absolute rotation angle.

  Here, a stray light path that deteriorates the detection accuracy of the absolute rotation angle will be described. Here, among the stray light paths, paths of light rays that are multiply reflected in the module package of the comparative example will be described.

  FIG. 9 is a diagram illustrating an example of stray light generated by the module package of the comparative example. Here, stray light generated in the module package 300X of the comparative example will be described. FIG. 9 shows a cross-sectional view of the module package 300X of the comparative example.

  The module package 300X of the comparative example has a package substrate 30X similar to the package substrate 30A, a light emitting element 31X similar to the light emitting element 31, a light receiving element 32X similar to the light receiving element 32, and a light similar to the light transmitting resin 33A. And a transparent resin 33X. The light emitting element 31X has a light emitting surface 310X similar to the light emitting surface 310, and the light receiving element 32X has a light receiving surface 320X similar to the light receiving surface 320. Further, the module package 300X of the comparative example does not include the light-shielding resin 34A.

  FIG. 9 illustrates an example of a light beam emitted from the light emitting element 31X, reflected in the module package 300X of the comparative example, and incident on the light receiving element 32X. Since the light emitting element 31X is an isotropic diffusion light source, light rays are emitted in all directions. Thus, the light beams emitted from the light emitting element 31X travel in various directions. For this reason, when there is no light-shielding resin 34A, as shown in FIG. 9, in the module package 300X, there is a light beam that enters the light receiving element 32X after repeating Fresnel reflection at the interface of the light-transmitting resin 33X. That is, in the light-transmitting resin 33X, the light beam is Fresnel-reflected on the upper surface and the side surface of the light-transmitting resin 33X, and a part of the Fresnel-reflected light beam enters the light receiving surface 320X. As a result, stray light other than the desired light enters the light receiving surface 320X, and deteriorates the absolute rotation angle detection accuracy.

  Therefore, in the first embodiment, as shown in FIG. 2, in the module package 300A, the light shielding resin 34A is divided so that the region 420 where the light emitting element 31 is arranged and the region 421 where the light receiving element 32 is arranged are divided. Is installed.

  As described above, since the light-shielding resin 34A is disposed in the module package 300A, the light emitted from the light emitting element 31 is shifted from the left area 420 on the light emitting element 31 side to the right area on the light receiving element 32 side. 421 can be prevented. Therefore, it is possible to prevent stray light, which is a part of the light beam reflected by the light transmitting resin 33A, from entering the light receiving surface 320.

  FIG. 10 is a diagram for explaining the paths of light rays in the module package according to the first embodiment. FIG. 10 shows a cross-sectional view of a module package 300B which is an example of the module package 300. The module package 300B includes a package substrate 30B, a light emitting element 31, a light receiving element 32, a light transmitting resin 33A, and a light shielding resin 34B as a light shielding part. A groove is provided in the package substrate 30B, and a part of the light shielding resin 34B is inserted. The light shielding resin 34B is formed of the same member as the light shielding resin 34A.

  In the module package 300B, the light beams emitted from the light emitting element 31 travel in various directions. In this case, in the light-transmitting resin 33A, light rays are reflected on the upper surface and side surfaces of the light-transmitting resin 33A in a region 401 on the left side of the region where the light-shielding resin 34B is arranged. A region 401 on the left side of the region where the light-shielding resin 34B is disposed is a region in the light-transmitting resin 33A where the light-emitting element 31 is disposed.

  Further, the light beam applied to the light shielding resin 34B is absorbed or scattered by the light shielding resin 34B. In other words, the light emitted from the light emitting element 31 is blocked by the light shielding resin 34B. Accordingly, stray light does not enter the region 402 on the right side of the region where the light-shielding resin 34B is disposed in the light-transmitting resin 33A. The area 402 on the right side of the area where the light-shielding resin 34B is arranged is an area in the light-transmitting resin 33A where the light receiving element 32 is arranged.

  As described above, since the light-blocking resin 34B is disposed in the module package 300B, it is possible to prevent light emitted from the light emitting element 31 from entering the right region 402 from the left region 401. Therefore, it is possible to prevent stray light, which is a part of the light beam reflected by the light transmitting resin 33A, from entering the light receiving surface 320.

  In the module package 300B, it is desirable that the light-shielding resin 34B be inserted into the package substrate 30B so that no gap is formed between the light-shielding resin 34B and the package substrate 30B. Note that a slight gap may be formed between the light-shielding resin 34B and the package substrate 30B, and even in this case, the effect of suppressing unnecessary light beams hardly changes.

  When the module package 300B is manufactured, for example, the light emitting element 31 and the light receiving element 32 are mounted on the package substrate 30B, and the upper surface side of the package substrate 30B is molded with the light transmitting resin 33A. Thereafter, a groove is formed between the light emitting element 31 and the light receiving element 32 by cutting the light transmissive resin 33A and the package substrate 30B or the like. Specifically, a groove is dug in the vertical direction by dicing or the like in a region between the light emitting element 31 and the light receiving element 32 in the light transmitting resin 33A. Then, this groove is further dug vertically in the package substrate 30B halfway. After the groove is formed in the light-transmitting resin 33A, the light-blocking resin 34B is embedded in the groove, so that the light-blocking resin 34B can be molded in the module package 300B. Thus, the light-shielding resin 34B is disposed in the region where the package substrate 30B is dug and the region where the light-transmitting resin 33A is dug. The manufacturing method is not limited as long as the module package 300B has the light-transmitting resin 33A and the light-shielding resin 34B.

  By the way, when the module package 300X of the comparative example is applied, a light beam multiple-reflected between the module package 300X and the optical pattern 200 may enter the light receiving element 32X. On the other hand, in the module package 300B, the light beams that are multiple-reflected between the module package 300B and the optical pattern 200 do not enter the light receiving element 32.

  FIG. 11 is a diagram for explaining how the module package according to the first embodiment prevents multiple reflected light from entering a light receiving element. Here, a light path between the module package 300B and the optical scale 2 will be described. FIG. 11 shows a cross-sectional view of the module package 300B.

  A part of the light beam emitted from the light emitting element 31 is reflected by the reflecting portion 201 of the optical pattern 200 provided in the optical scale 2 and then sent to the surface of the light transmitting resin 33A of the module package 300B. The light beam sent to the surface of the light transmitting resin 33A is absorbed or scattered by the light shielding resin 34B. Thus, in the module package 300B, the light beam transmitted to the surface of the light transmitting resin 33A does not advance to the reflecting portion 201 of the optical pattern 200 again.

  In the case of the module package 300X of the comparative example, that is, when there is no light-blocking resin 34B, a part of the light beam emitted from the light emitting element 31X is reflected by the reflection part 201 of the optical pattern 200 provided in the optical scale 2, and thereafter, The light is reflected on the surface of the light transmitting resin 33X of the module package 300X. Further, the light beam reflected on the surface of the light-transmitting resin 33X is reflected on the reflecting portion 201 of the optical pattern 200 and enters the light receiving element 32X. As described above, an unnecessary light path may be generated due to multiple reflection between the module package 300 </ b> X of the comparative example and the optical scale 2.

  In FIG. 11, the path of the light ray indicated by the solid line is a normal light path 901 required for detecting the absolute rotation angle, and the path of the light ray indicated by the broken line is the light path 902 of the unnecessary light. In the case of the module package 300B, the light beam in the light beam path 901 is reflected at the position P52 of the optical scale 2 and then enters the light receiving element 32. On the other hand, in the case of the module package 300X of the comparative example shown in FIG. 9, the light ray in the light path 902 is reflected at the position P51 of the optical scale 2 and then reflected by the light transmitting resin 33X. At the position P53, and enters the light receiving element 32X. In this case, the position P52 where the light beam traveling along the regular light beam path 901 is reflected by the optical scale 2 and the positions P51 and P53 where unnecessary light beams traveling along the light beam path 902 are reflected by the optical scale 2 are optical The position of the expression scale 2 in the radial direction is different. The waveform corresponding to the light beam reflected at the position P52 is an ideal waveform, whereas the waveform corresponding to the light beam reflected at the positions P51 and P53 is shifted from the ideal waveform. . This is because the pattern passing through the positions P51 and P53, which are two points having different radial positions, is incident on the light receiving element 32X. As a result, an unnecessary light beam depending on the position on the optical scale 2 is generated. . Therefore, when the light receiving element 32X receives the light beams reflected at the positions P51 and P53, the signal detected by the light receiving element 32X has a waveform distorted from an ideal waveform.

  Here, the waveform of the signal when only the light beam of the normal light path 901 is received, and the waveform of the signal when both the light beam of the normal light path 901 and the light beam of the non-normal light path 902 are received are described. The comparison will be described.

  The waveform of the signal when only the light beam on the regular light beam path 901 is received is the signal of the light beam detected by the light receiving element 32 of the module package 300A or 300B of the first embodiment. On the other hand, the waveform of the signal when both the light beam on the regular light beam path 901 and the light beam on the irregular light beam path 902 are received is the signal of the light beam detected by the light receiving element 32X of the module package 300X of the comparative example.

  FIG. 12 is a diagram illustrating a waveform example of a signal detected by the light receiving element of the module package according to the first embodiment. FIG. 13 is a diagram illustrating a waveform example of a signal detected by the light receiving element of the module package of the comparative example.

  The waveform of the signal shown in FIG. 12 is a waveform 71 when the light receiving element 32 of the module package 300A or the module package 300B receives only the light beam in the normal light beam path 901. The waveform of the signal shown in FIG. 13 is the waveform 72 when the light receiving element 32X of the module package 300X receives the light beams in both the normal light path 901 and the irregular light path 902. The waveform 71 shown in FIG. 12 is an ideal waveform based on the light beam of the normal light path 901, whereas the waveform 72 shown in FIG. 13 is a distorted waveform 71 shown in FIG. As described above, when the unnecessary light ray in the light ray path 902 is superimposed on the light ray in the normal light ray path 901, the waveform 71 shown in FIG. 12 becomes a distorted waveform like the waveform 72 shown in FIG.

  A signal corresponding to an unnecessary light ray in the light ray path 902 changes according to a reflection position on the optical pattern 200. That is, since the optical pattern 200 has various patterns arranged for each position, a signal corresponding to an unnecessary light ray in the light path 902 generates various signals for each irradiation position of the light ray on the optical pattern 200. . As described above, the unnecessary light rays reflected by the optical pattern 200 are variously affected by each rotation position of the optical pattern 200. On the other hand, the amount of unnecessary light reflected in the light transmitting resin 33A is always constant regardless of the optical pattern 200. Therefore, it is more difficult to correct the unnecessary light beam reflected by the optical pattern 200 than the unnecessary light beam reflected in the light transmitting resin 33A.

  As described above, the unnecessary light beam reflected by the optical pattern 200 changes the influence at each position of the reflection corresponding to the absolute rotation angle. Therefore, the unnecessary light beam is unnecessary only by the correction when the absolute encoder 1 is shipped. The effects of light cannot be eliminated.

  In the case of the module package 300 </ b> B, the unnecessary light beam path 902 passes through an intermediate position between the light emitting surface 310 of the light emitting element 31 and the light receiving surface 320 of the light receiving element 32. Therefore, the light-shielding resin 34B of the module package 300B is disposed at an intermediate position between the light emitting surface 310 and the light receiving surface 320. As a result, after the light beam in the light beam path 902 is reflected by the optical scale 2, the light beam is irradiated on the light shielding resin 34B exposed on the upper surface of the light transmitting resin 33A, and is absorbed or scattered by the light shielding resin 34B. Accordingly, since the light beam in the light path 902 is not reflected on the upper surface of the package substrate 30B, the light beam in the light path 902 is not irradiated on the optical scale 2. Therefore, since the light beam in the light path 902 is not reflected by the optical scale 2, the light beam in the light path 902 does not irradiate the light receiving surface 320. The light-shielding resin 34A of the module package 300A may be arranged at an intermediate position between the light emitting surface 310 and the light receiving surface 320.

  Here, the arrangement positions of the light-shielding resins 34A and 34B will be specifically described. FIG. 14 is a diagram for explaining an arrangement position of the light shielding resin included in the module package according to the first embodiment. The arrangement position of the light-shielding resin 34A when the module package 300A is viewed from the upper surface is the same as the arrangement position of the light-shielding resin 34B when the module package 300B is viewed from the upper surface. Therefore, here, the arrangement position of the light shielding resin 34B in the module package 300B will be described.

  FIG. 14 is a top view of the module package 300B, which is hatched to clarify the correspondence with the sectional view of FIG. As shown in FIG. 14, in the module package 300B, the light-shielding resin 34B is disposed so as to pass through an intermediate position between the center of the light emitting surface 310 and the center of the light receiving surface 320. Specifically, the light-shielding resin 34B is set so that the distance from the center of the light-shielding resin 34B to the center of the light-emitting surface 310 is equal to the distance from the center of the light-shielding resin 34B to the center of the light-receiving surface 320. Be placed.

  Here, a case has been described where the center of the light-blocking resin 34B is located at an intermediate position between the light-emitting surface 310 and the light-receiving surface 320. It is sufficient that the light-shielding resin 34B exists. Therefore, the center of the light-shielding resin 34B may be shifted from an intermediate position between the light emitting surface 310 and the light receiving surface 320.

  When the module package 300X of the comparative example is applied, the light beam reflected by the optical pattern 200 may be multiple-reflected between the light receiving element 32X and the light transmitting resin 33X and may enter the light receiving element 32X.

  FIG. 15 is a diagram illustrating a third example of stray light generated by the module package of the comparative example. Here, a case in which the light beam reflected by the optical pattern 200 is multiple-reflected between the light receiving element 32X and the light transmitting resin 33X will be described. FIG. 15 shows a cross-sectional view of the module package 300X of the comparative example.

  As shown in FIG. 15, when the module package 300X of the comparative example is applied, a light beam emitted from the light emitting element 31X is reflected by the optical scale 2, and thereafter, is irradiated on the light receiving element 32X. Part of the light beam irradiated on the light receiving element 32X is reflected around the light receiving surface 320X or the light receiving surface 320X itself. The light is reflected by the light receiving surface 320X itself because the light receiving surface 320X is made of a reflective material.

  The light beam reflected on the periphery of the light receiving surface 320X or on the light receiving surface 320X itself is reflected on the surface of the light transmitting resin 33X by Fresnel reflection, and travels to the light receiving element 32X again. The position P52 where the light ray traveling along the regular ray path 901 is reflected by the optical scale 2 and the position P54 where the unnecessary light ray traveling along the irregular ray path 903 is reflected by the optical scale 2 are the optical scale 2 Are shifted in the radial direction of the optical pattern 200 provided. That is, the position P54 is shifted in the radial direction of the rotary shaft 5 from the position P52.

  For this reason, the optical path length before reaching the light receiving element 32X is different between the light path 901 and the light path 903. Therefore, the magnification of the bit pattern of the optical scale 2 when reaching the light receiving element 32X is different between the light beam path 901 and the light beam path 903. Therefore, when the light receiving element 32X receives both the light ray on the light ray path 901 and the light ray on the light ray path 903, distortion occurs in the light amount distribution received by the light receiving element 32X. In other words, when the light receiving element 32X receives the light beam in the light path 903, the light amount distribution when the light receiving element 32X receives only the light beam in the light path 901 is distorted. Therefore, when the light receiving element 32X receives the light beam on the light beam path 903, an error occurs in the detection accuracy of the absolute rotation angle.

  As the relative distance between the module package 300X and the optical scale 2 increases, the angle of the light beam incident on the light receiving element 32X becomes closer to the vertical, so that unnecessary light rays are more likely to enter the light receiving element 32X. Therefore, as the module package 300X and the optical scale 2 are farther apart, multiple reflection between the light receiving element 32X and the light transmitting resin 33X is more likely to occur.

  In the first embodiment, by adjusting the dimensional relationship of the components included in the module packages 300A and 300B, it is possible to prevent unnecessary light beams in the light beam path 903 from entering the light receiving element 32. The dimensional relationship of the components included in the module package 300A is the same as the dimensional relationship of the components included in the module package 300B. Therefore, here, the dimensional relationship of the components included in the module package 300B will be described.

  FIG. 16 is a diagram for explaining a dimensional relationship of components included in the module package according to the first embodiment. It is assumed that the module package 300B and the optical scale 2 are arranged at positions separated by the maximum allowable distance. The distance from the upper surface of the module package 300B to the optical scale 2 is distance L1, and the distance from the center of the light emitting surface 310 to the end face of the light receiving element 32 on the light emitting element 31 side is distance L2. In this case, the angle θ1 of the light beam incident on the end face of the light receiving element 32 on the light emitting element 31 side is determined by the distance L1 and the distance L2. In this case, the angle θ1 is calculated after the refractive index n1 of the light transmitting resin 33A and the refractive index nx of air between the light transmitting resin 33A and the optical scale 2 are applied to Snell's law. Is done. According to Snell's law, when the angle of a light beam incident on the light transmitting resin 33A from the air side is an angle θx, n1 × sinθ1 = nx × sinθx. Further, if a distance between an emission point of the light beam from the light transmitting resin 33A to the air side and an incident point of the light beam from the air side to the light transmitting resin 33A is a distance L0, tan θx = L0 / (2 × L1). As described above, the angle θ1 is calculated using the angle θx, and the angle θx is calculated using the distances L1 and L0. Assuming that the distance from the light receiving surface 320 in the same plane as the upper surface of the light receiving element 32 to the upper surface of the light transmitting resin 33A is a distance L3, the distance L0 is calculated from the distances L1, L2, and L3. Therefore, the angle θ1 is calculated using the distances L1, L2, L3.

  The distance from the end of the light receiving element 32 on the light emitting element 31 side to the end of the light receiving surface 320 on the side opposite to the light emitting element 31 side is defined as a distance L4. Note that the end of the light receiving element 32 on the light emitting element 31 side is a side end surface extending in the vertical direction, and the end of the light receiving surface 320 opposite to the light emitting element 31 side is a vertical end of the member having the light receiving surface 320. It is a side end surface extending in the direction.

  Assuming that a distance between a position where light is first incident on the light emitting element 31 side end of the light receiving element 32 and a position where light is incident for the second time is Lx, Lx = 2 × tan θ1 × L3.

  Here, if Lx> L4, the light firstly incident on the light-emitting element 31 side end of the light-receiving element 32 along the light ray path 903 deviates from the light-receiving surface 320 at the second incidence. Further, the second incidence of light incident on the right side of the end of the light receiving element 32 on the light emitting element 31 side also deviates from the light receiving surface 320.

for that reason,
2 × tan θ1 × L3> L4 (1)
When the relationship is established, it is possible to prevent the light that is multiply reflected between the light receiving element 32 and the light transmitting resin 33A from being incident on the light receiving surface 320. Note that, as described above, since the angle θ1 can be calculated using the distances L1, L2, and L3, the above relationship (1) is
(L2 / L1) × L3> L4 (2)
Can be rewritten as

  Since the module package 300B is configured to satisfy Expression (1), it is possible to prevent unnecessary light beams from being incident on the light receiving element 32. Note that the distance L1 may be a distance from the upper surface of the module package 300B to the optical pattern 200.

  Here, a hardware configuration of the control unit 4 will be described. The control unit 4 can be realized by a control circuit, that is, a processor and a memory. The processor is a CPU (Central Processing Unit) or the like. The memory is a random access memory (RAM) or a read only memory (ROM).

  The control unit 4 is realized by a processor reading and executing a program stored in a memory. It can be said that this program causes a computer to execute the procedure or method of the control unit 4. The memory is also used as a temporary memory when the processor executes various processes.

  Further, the control unit 4 may be realized by dedicated hardware. Further, some of the functions of the control unit 4 may be realized by dedicated hardware, and some may be realized by software or firmware.

  The light-shielding resin 34B described with reference to FIGS. 10 and 16 is not limited to being arranged at an intermediate position between the center of the light emitting surface 310 and the center of the light receiving surface 320, but may be arranged in another region. .

  As described above, in the module package 300A of the first embodiment, the entire light emitting element 31 and the light receiving element 32 mounted on the package substrate 30A are covered with the light transmitting resin 33A, and light is shielded between the light emitting element 31 and the light receiving element 32. The conductive resin 34A is provided. Similarly, in the module package 300B, the light emitting element 31 and the light receiving element 32 mounted on the package substrate 30B are entirely covered with a light transmitting resin 33A, and a light shielding resin 34B is provided between the light emitting element 31 and the light receiving element 32. I have. Therefore, in the module packages 300A and 300B, unnecessary light rays that directly enter the light receiving element 32 from the light emitting element 31 can be removed by the light shielding resins 34A and 34B, so that the absolute rotation angle can be detected with high accuracy. Becomes

  In the module package 300A, the light-shielding resin 34A is provided at an intermediate position between the center of the light-emitting surface 310 of the light-emitting element 31 and the center of the light-receiving surface 320 of the light-receiving element 32. Unnecessary light rays due to multiple reflection with the optical scale 2 can be suppressed. Similarly, in the module package 300B, since the light shielding resin 34B is provided at an intermediate position between the center of the light emitting surface 310 of the light emitting element 31 and the center of the light receiving surface 320 of the light receiving element 32, the light transmitting resin 33A Unnecessary light rays due to multiple reflection between the optical scale 2 and the optical scale 2 can be suppressed. Therefore, the module packages 300A and 300B can detect the absolute rotation angle with high accuracy.

  In addition, since the module packages 300A and 300B are configured to satisfy the above-described expression (1), it is possible to prevent unnecessary light beams from entering the light receiving element 32. Therefore, the module packages 300A and 300B can detect the absolute rotation angle with high accuracy.

  Further, since the package substrates 30A and 30B are formed of glass epoxy substrates, and the light-transmitting resin 33A and the light-shielding resins 34A and 34B are both formed of an epoxy resin, cracks at the time of temperature change can be suppressed. it can. This makes it possible to enhance the reliability of the module packages 300A and 300B.

  As described above, according to the first embodiment, the module packages 300A and 300B are arranged such that the light-shielding resin 34A is located at an intermediate position between the center of the light-emitting surface 310 of the light-emitting element 31 and the center of the light-receiving surface 320 of the light-receiving element 32. , 34B, it is possible to accurately detect the absolute rotation angle of the measurement object.

Embodiment 2 FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, the upper surface of the light-transmitting resin is inclined with respect to the light-receiving surface 320 of the light-receiving element 32, so that the light reflected by the light-transmitting resin enters the light-receiving surface 320 of the light-receiving element 32. Suppress.

  FIG. 17 is a diagram illustrating a first configuration example of the module package according to the second embodiment. 17, components that achieve the same functions as those of the module package 300A of the first embodiment shown in FIG. 2 or the module package 300B of the first embodiment shown in FIG. 10 are denoted by the same reference numerals. , Overlapping description will be omitted.

  The module package 300C according to the second embodiment includes a package substrate 30B, a light emitting element 31, a light receiving element 32, a light transmitting resin 33C, and a light shielding resin 34C that is a light shielding part. As described above, the module package 300C includes the light transmitting resin 33C instead of the light transmitting resin 33A.

  The light-shielding resin 34C has a shorter vertical length than the light-shielding resins 34A and 34B, but the other configuration is the same. The light transmitting resin 33C is formed using the same member as the light transmitting resin 33A, and has a different shape from the light transmitting resin 33A. The light-transmitting resin 33C covers the entire light-emitting element 31 and light-receiving element 32 on the package substrate 30B, similarly to the light-transmitting resin 33A.

  The light-transmitting resin 33C has a region 403 on the left side of the region where the light-shielding resin 34C is arranged, and a region 404 on the right side of the region where the light-shielding resin 34C is arranged. The upper surface of the light transmitting resin 33C in the region 403 is the upper surface 150, and the upper surface of the light transmitting resin 33C in the region 404 is the upper surface 151.

  The horizontal first surface of the light-shielding resin 34C is in the same plane as the upper surface 150 of the light-transmitting resin 33C in the region 403. The second horizontal surface of the light-shielding resin 34C is in contact with the package substrate 30B inside the package substrate 30B.

  In the first embodiment, the case has been described where the upper surface, which is the surface on the optical scale 2 side, of the light transmitting resin 33A has a flat shape. However, in the second embodiment, the upper surface 151 of the light transmitting resin 33C has a slope. Is provided. In the module package 300C, of the upper surface of the light-transmitting resin 33C, the upper surface 151 on the light receiving element 32 side is inclined not parallel to the light receiving surface 320 in the same plane as the upper surface of the light receiving element 32. Specifically, the thickness of the light-transmitting resin 33C in the region 404 is gradually increased from the end on the light-shielding resin 34C side toward the end on the opposite side to the light-shielding resin 34C. The thickness of the light-transmitting resin 33C in the region 404 at the end on the light-shielding resin 34C side is the same as the thickness of the light-transmitting resin 33C in the region 403. In the module package 300C, the angle between the upper surface 150 and the upper surface 151 is an angle θ2. In other words, the inclination angle of the upper surface 151 is the angle θ2.

  As described above, the absolute encoder 1 according to the second embodiment has the same basic configuration as the absolute encoder 1 according to the first embodiment, but the shape of the region 404 of the light-transmitting resin 33C is different from that of the light-transmitting resin. The shape is different from the shape in the region 402 of 33A.

  As shown in FIG. 15, in the module package 300X of the comparative example, unnecessary light rays from the optical scale 2 enter the light receiving element 32X. In this case, the ray path 903 of the unnecessary ray and the normal ray path 901 have substantially the same incident angle to the light receiving element 32X. Specifically, the angle at which an unnecessary light beam is Fresnel-reflected on the upper surface of the light transmitting resin 33X and enters the light receiving element 32X is substantially the same as the angle at which a regular light beam enters the light receiving element 32X. Therefore, in the second embodiment, the upper surface 151 that receives light rays and reflects unnecessary light rays is inclined from the horizontal direction. Thus, the upper surface 151 is provided with a gradient so that unnecessary light rays are reflected at a wide reflection angle.

  With such a configuration, in the module package 300C, the light beam reflected by the light receiving element 32 is Fresnel-reflected on the upper surface 151 of the light transmitting resin 33C, but the angle of the reflected light beam is the angle θ2 which is the gradient angle of the upper surface 151. Lean. Therefore, unnecessary light beams reflected by the light receiving element 32 and the upper surface 151 are less likely to enter the light receiving surface 320 of the light receiving element 32. Unnecessary light rays due to multiple reflection between the light receiving element 32 and the light transmitting resin 33C are less likely to be incident on the light receiving surface 320 as the angle θ2 that is the inclination angle is larger. Therefore, the light transmitting resin 33C in the region 403 can be thinner as the angle θ2 is larger. As described above, in the module package 300C, the thickness of the light transmitting resin 33C can be reduced as compared with the light transmitting resin 33A of the first embodiment.

  Note that the module package 300C may include a package substrate 30A instead of the package substrate 30B. In other words, the light transmitting resin 33C may be applied to the module package 300A. In this case, the module package 300A includes a light-transmitting resin 33C instead of the light-transmitting resin 33A, and includes a light-shielding resin 34C instead of the light-shielding resin 34A.

  Also, in FIG. 17, the case where the upper surface 151 is provided with a gradient is described, but the upper surface 150 may be provided with the same gradient as the upper surface 151. FIG. 18 is a diagram illustrating a second configuration example of the module package according to the second embodiment. Components that achieve the same functions as those of the module package 300C illustrated in FIG. 17 among the components illustrated in FIG. 18 are denoted by the same reference numerals, and redundant description will be omitted.

  The module package 300D includes a package substrate 30B, a light emitting element 31, a light receiving element 32, a light transmitting resin 33D, and a light shielding resin 34C as a light shielding part. As described above, the module package 300D includes the light transmitting resin 33D instead of the light transmitting resin 33C.

  The light transmitting resin 33D is formed using the same member as the light transmitting resin 33C, and has a different shape from the light transmitting resin 33C. The light transmissive resin 33D covers the entire light emitting element 31 and light receiving element 32 on the package substrate 30B, similarly to the light transmissive resin 33C.

  The light-transmitting resin 33D has a region 405 on the left side of the region where the light-shielding resin 34C is arranged, and a region 406 on the right side of the region where the light-shielding resin 34C is arranged. The upper surface of the light transmitting resin 33D in the region 405 is the upper surface 152, and the upper surface of the light transmitting resin 33D in the region 406 is the upper surface 153. The region 406 is a region similar to the region 404, and the upper surface 153 is a surface similar to the upper surface 151.

  In the module package 300D, the upper surface 152 of the light-transmitting resin 33D is inclined not parallel to the light receiving surface 320 in the same plane as the upper surface of the light receiving element 32. Specifically, the thickness of the light-transmitting resin 33D in the region 405 gradually decreases from the end on the light-shielding resin 34C side toward the end on the opposite side to the light-shielding resin 34C. .

  The thickness of the light-transmitting resin 33D at the end of the region 405 on the side of the light-shielding resin 34C is the same as the thickness of the region 406 at the end of the region 406 on the side of the light-shielding resin 34C. In the module package 300D, the angle formed between the bottom surface of the light transmitting resin 33D and the upper surface 152 is an angle θ2, and the angle formed between the bottom surface of the light transmitting resin 33D and the upper surface 153 is an angle θ2. In other words, the inclination angle of the upper surfaces 152 and 153 is the angle θ2.

  As described above, in the second embodiment, since the upper surfaces 151 and 153 of the light transmitting resins 33C and 33D on the light receiving element 32 side are provided with a gradient, the light transmitting resins 33C and 33D are reflected after the light rays are reflected by the light receiving element 32. When Fresnel reflection is performed on the upper surfaces 151 and 153, the light is reflected while being inclined by an angle θ2 that is a gradient angle. For this reason, unnecessary light beams that are multiple reflected are less likely to be incident on the light receiving surface 320. As a result, the module packages 300C and 300D can detect the absolute rotation angle with high accuracy. Further, since the thickness of the light-transmitting resins 33C and 33D can be reduced, the material cost for manufacturing the module packages 300C and 300D can be reduced, and the absolute rotation angle can be detected at low cost. It becomes possible.

  Note that the module package 300D may include a package substrate 30A instead of the package substrate 30B. In other words, the light transmitting resin 33D may be applied to the module package 300A. In this case, the module package 300A includes a light-transmitting resin 33D instead of the light-transmitting resin 33A, and includes a light-shielding resin 34C instead of the light-shielding resin 34A.

  Further, the light-shielding resin 34C described with reference to FIGS. 17 and 18 is not limited to being disposed at an intermediate position between the center of the light emitting surface 310 and the center of the light receiving surface 320, and may be disposed in another region. .

  As described above, according to the second embodiment, since the upper surfaces 151 and 153 of the light-transmitting resins 33C and 33D are inclined, unnecessary light rays reflected by the upper surfaces 151 and 153 of the light-transmitting resins 33C and 33D can be removed. It becomes difficult to enter the light receiving surface 320. Therefore, it is possible to accurately detect the absolute rotation angle of the measurement object.

  Although the first and second embodiments have described the case where the absolute encoder 1 is a rotary encoder that detects a rotation angle, the absolute encoder 1 can be applied to a linear encoder that detects a linear movement amount. is there.

  The configurations described in the above embodiments are merely examples of the contents of the present invention, and can be combined with other known technologies, and can be combined with other known technologies without departing from the gist of the present invention. Parts can be omitted or changed.

  Reference Signs List 1 absolute encoder, 2 optical scale, 4 control unit, 5 rotary shaft, 19 look-up table, 30A, 30B package board, 31, 31X light emitting element, 32, 32X light receiving element, 33A, 33C, 33D, 33X Resin, 34A, 34B, 34C light-shielding resin, 41 angle calculation unit, 42 light emission amount adjustment unit, 150 to 153 top surface, 200 optical patterns, 201 reflection unit, 202 non-reflection unit, 300, 300A, 300B, 300X module package, 310, 310X light-emitting surface, 320, 320X light-receiving surface, 411 light amount distribution correction unit, 412 edge detection unit, 413 coarse detection unit, 414 high-precision detection unit, 415 rotation angle detection unit, 901 to 903 ray path.

In order to solve the above-described problems and achieve the object, an absolute encoder according to the present invention includes an optical scale having an optical pattern, a light emitting element that irradiates light to the optical scale, and a light receiving element that receives reflected light from the optical scale. And a control unit for calculating an absolute rotation angle of the optical scale based on a signal output from the light receiving element according to the reflected light. Further, in the absolute encoder of the present invention, the module package may be configured such that the angle of the light beam irradiated to the light emitting element side end of the light receiving element is θ1, and the distance from the light receiving surface of the light receiving element to the upper surface of the light transmitting resin is L3. When a distance from an end of the light receiving element on the light emitting element side to an end of the light receiving surface opposite to the light emitting element is L4, 2 × tan θ1 × L3> L4 is satisfied. .

Claims (5)

An optical scale having an optical pattern;
A module package in which a light-emitting element that irradiates light to the optical scale and a light-receiving element that receives reflected light from the optical scale are covered with a light-transmitting resin,
A control unit that calculates an absolute rotation angle of the optical scale based on a signal output by the light receiving element according to the reflected light,
With
The module package includes:
A light-shielding portion that is exposed on a surface of the light-transmitting resin that faces the optical scale and that passes through a middle position between the center of the light-emitting surface of the light-emitting element and the center of the light-receiving surface of the light-receiving element is disposed.
Absolute encoder. The module package further includes a package substrate on which the light emitting element and the light receiving element are mounted,
The light shielding portion is disposed in a region where the package substrate is dug and a region where the light transmitting resin is dug.
The absolute encoder according to claim 1, wherein: The package substrate is a glass epoxy substrate,
The light-transmitting resin and the light-shielding portion are epoxy-based resins,
The absolute encoder according to claim 2, wherein: An optical scale having an optical pattern;
A module package in which a light-emitting element that irradiates light to the optical scale and a light-receiving element that receives reflected light from the optical scale are covered with a light-transmitting resin,
A control unit that calculates an absolute rotation angle of the optical scale based on a signal output by the light receiving element according to the reflected light,
With
The module package includes:
The angle of a light beam applied to the light emitting element side end of the light receiving element is θ1, the distance from the light receiving surface of the light receiving element to the upper surface of the light transmitting resin is L3, and the light emitting element of the light receiving element is When a distance from an end of the light receiving surface to an end of the light receiving surface opposite to the light emitting element side is L4, 2 × tan θ1 × L3> L4 is satisfied.
Absolute encoder. An optical scale having an optical pattern;
A module package in which a light-emitting element that irradiates light to the optical scale and a light-receiving element that receives reflected light from the optical scale are covered with a light-transmitting resin,
A control unit that calculates an absolute rotation angle of the optical scale based on a signal output by the light receiving element according to the reflected light,
With
The light-transmitting resin has an upper surface, which is a surface facing the optical scale, inclined with respect to a light-receiving surface of the light-receiving element,
Absolute encoder.

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