JP4869641B2 - Optical encoder - Google Patents

Description

  The present invention relates to an optical encoder that detects the position and the like of an object to be detected.

  Conventionally, for example, Patent Document 1 proposes an optical encoder having a small sensor head in which a light source and a photodetector are integrated with a light-transmitting resin. 18A and 18B show the configuration of the optical encoder disclosed in Patent Document 1. FIG. A chip-like light emitting element 24 as a light source and a chip-like light receiving element 26 as a photodetector are die bonded to the same surface of the lead frame 30. Then, the light receiving element 24 and the light receiving element 26 are molded with a light transmitting resin. At the same time, a sensor head in which a member made of a light transmitting material is attached and integrated is configured. With this configuration, the number of parts is small, and the manufacturing cost can be reduced.

JP-A-64-74415

However, in the case where the light emitting element and the light receiving element are mounted on the lead frame as in the above-described conventional example, the sensor head is molded and integrated with the light transmitting resin, or the light transmitting material is pasted on the light transmitting resin. The following problems will occur. For example, as shown in FIG. 15, the light La emitted from the light emitting portion of the light source 70 has a direction along the normal line N of the interface 80 at the interface 80 between the light transmitting resin 60 and the outside (generally air). Consider the case of forming an angle θ2. When the refractive index of the outside medium is n1, the refractive index of the light transmitting resin 60 is n2, and the refraction angle θ1 of the refracted light Lb1 toward the outside, the relationship of the following equation (1) is established according to Snell's law.
n1 · sin θ1 = n2 · sin θ2 (1)

The outside medium is generally air. For this reason, the refractive index of the external medium is approximately n1≈1. Further, the refractive index of the light transmitting material such as light transmitting resin or glass is n2> 1. For this reason, there is a critical angle θcr at which the light La is totally reflected at the interface 80 between the light transmitting resin 60 and the outside. The critical angle θcr is when θ1 = 90 degrees in the equation (1), and can be expressed by the equation (2).
θcr = sin ⁻¹ (n1 / n2) (2)

In the range of the angle θ2 larger than the critical angle θcr as shown in the equation (3), the light La emitted from the light emitting portion of the light source 70 is totally reflected at the interface between the light transmitting resin and the outside.
θ2 ≧ sin ⁻¹ (n1 / n2) (3)

  On the other hand, in the optical encoder shown in FIG. 16A, the scale 91 having the lattice pattern with the pitch P2 moves relative to the sensor head 92. As a result, the light emitted from the light source is diffracted under the influence of the grating pattern formed on the scale 91. For this reason, a displacement signal having a period P2 is obtained from the sensor head 92.

  Here, the “displacement signal” is a signal obtained by performing signal processing on a plurality of analog signals whose phases that periodically change according to the relative movement between the scale 91 and the sensor head 92 are shifted by a certain angle, or this analog signal. It is a converted digital signal. An example of two-phase analog signals of A phase and B phase that are 90 degrees out of phase is shown in FIG. 16B, and an example of a digital signal is shown in FIG. 16C.

  For example, there is a case where the light Lb2 that is totally reflected by the interface 80 between the light transmitting resin 60 and the outside of the light La emitted from the light emitting portion of the light source 70 shown in FIG. 15 enters the light receiving portion of the photodetector 90. . In this case, the DC components Adc and Bdc of the analog signal increase as shown in FIG. The analog displacement signal shown in FIG. 17A is a voltage obtained by converting the photocurrent received by the light receiving unit of the photodetector 90 into a voltage. In order to increase the S / N ratio of the displacement signal and improve the accuracy of position detection, it is desirable to increase the amplitude of the displacement signal as much as possible.

  On the other hand, when the DC component becomes large and the displacement signal voltage is equal to or higher than the operating voltage of the displacement signal processing circuit as shown in FIG. 17B, the problem of displacement signal saturation occurs. In particular, when a low-voltage driven processing circuit is desired, it is necessary to reduce the DC component in order to obtain a displacement signal having a large amplitude without saturation.

  The present invention has been made in view of the above, and provides an inexpensive optical encoder that prevents saturation of the displacement signal by reducing the above-described DC component and has a large displacement signal amplitude with respect to the DC component. The purpose is to do.

In order to solve the above-described problems and achieve the object, according to the first aspect of the present invention, there is provided a sensor head comprising a package in which at least one light source and at least one photodetector are arranged side by side and integrated with a light transmitting resin. The sensor head is composed of a scale that is displaced relative to the sensor head, and the light emitted from the light emitting part of the light source is reflected and diffracted by the scale, and the reflected and diffracted light is received by the light receiving part of the photodetector. In an optical encoder that outputs a displacement signal from
Of the light emitted from an arbitrary point of the light emitting part of the light source, the light totally reflected at the interface between the light transmitting resin and the outside is incident on at least a part of the light receiving part of the light detector , and the light detector The relationship between the distance between the light emitting part of the light source and the light receiving part of the light detector, the thickness of the light transmitting resin, and the refractive index of the light transmitting resin so that the light enters from the center of the light receiving part. An optical encoder characterized by being set can be provided.

  Moreover, according to the preferable aspect of this invention, it is desirable for the surface which opposes the scale of light transmissive resin to be substantially flat.

Further, according to a preferred aspect of the present invention, the surface facing the scale of the light transmitting resin, the surface of the light emitting part of the light source, and the surface of the light receiving part of the photodetector are substantially parallel,
The thickness from the surface of the light emitting part of the light source to the surface facing the scale of the light transmitting resin is t11,
The thickness from the surface of the light receiving portion of the photodetector to the surface facing the scale of the light transmitting resin is t21,
The distance in the direction parallel to the surface of the light transmitting resin from an arbitrary point of the light emitting part of the light source to the center of the light receiving part of the photodetector is dc,
The refractive index of the outside medium is n1,
When the refractive index of the light transmitting resin is n2, respectively.
tan ⁻¹ (dc / (t11 + t21)) <sin ⁻¹ (n1 / n2)
It is desirable to satisfy the following conditional expression.

Further, according to a preferred aspect of the present invention, the surface facing the scale of the light transmitting resin, the surface of the light emitting part of the light source, and the surface of the light receiving part of the photodetector are substantially parallel,
The thickness from the surface of the light emitting part of the light source to the surface facing the scale of the light transmitting resin is t111,
The thickness from the light receiving surface of the photodetector to the surface facing the scale of the light transmitting resin is t211;
The longest distance among the distances in the direction parallel to the surface of the light transmitting resin from an arbitrary point of the light emitting part of the light source to the light receiving part of the photodetector is de,
The refractive index of the outside medium is n1,
When the refractive index of the light transmitting resin is n2, respectively.
tan ⁻¹ (de / (t111 + t211)) <sin ⁻¹ (n1 / n2)
It is desirable to satisfy the following conditional expression.

  According to a preferred aspect of the present invention, at least a part of the surface between the light emitting part of the light source and the light receiving part of the photodetector among the surfaces facing the scale of the light transmitting resin has a convex part. It is desirable that

According to the second aspect of the present invention, there is provided a sensor head composed of a package in which at least one light source and at least one photodetector are arranged side by side and integrated with a light transmitting resin, and a scale that is displaced relative to the sensor head. In an optical encoder configured to reflect and diffract light emitted from a light emitting part of a light source with a scale, receive the reflected and diffracted light with a light receiving part of a photodetector, and output a displacement signal from a sensor head,
Of the light emitted from an arbitrary point of the light emitting part of the light source, the light totally reflected at the interface between the light transmitting resin and the outside enters the outside as viewed from the light source side of the center of the light receiving part of the photodetector. As described above, the relationship between the distance between the light emitting portion of the light source and the light receiving portion of the photodetector, the thickness of the light transmitting resin, and the refractive index of the light transmitting resin is set.
At least a part of the surface between the light emitting part of the light source and the light receiving part of the photodetector among the surfaces facing the scale of the light transmitting resin has a convex part,
The surface of the convex portion, the surface of the light emitting portion of the light source, and the surface of the light receiving portion of the photodetector are substantially parallel among the surfaces facing the scale of the light transmitting resin,
The thickness from the surface of the light emitting portion of the light source to the surface facing the scale of the convex portion of the light transmitting resin is t12,
The thickness from the surface of the light receiving portion of the photodetector to the surface facing the scale of the convex portion of the light transmitting resin is t22,
The distance in the direction parallel to the surface of the light transmitting resin from an arbitrary point of the light emitting part of the light source to the center of the light receiving part of the photodetector is dc,
The refractive index of the outside medium is n1,
When the refractive index of the light transmitting resin is n2, respectively.
tan ⁻¹ (dc / (t12 + t22)) <sin ⁻¹ (n1 / n2)
An optical encoder characterized by satisfying the following conditional expression can be provided .

According to a third aspect of the present invention, there is provided a sensor head comprising a package in which at least one light source and at least one photodetector are arranged side by side and integrated with a light transmitting resin, and a scale that is displaced relative to the sensor head. In an optical encoder configured to reflect and diffract light emitted from a light emitting part of a light source with a scale, receive the reflected and diffracted light with a light receiving part of a photodetector, and output a displacement signal from a sensor head,
Of the light emitted from an arbitrary point of the light emitting part of the light source, the light totally reflected at the interface between the light transmitting resin and the outside enters the outside as viewed from the light source side of the center of the light receiving part of the photodetector. As described above, the relationship between the distance between the light emitting portion of the light source and the light receiving portion of the photodetector, the thickness of the light transmitting resin, and the refractive index of the light transmitting resin is set.
At least a part of the surface between the light emitting part of the light source and the light receiving part of the photodetector among the surfaces facing the scale of the light transmitting resin has a convex part,
The surface of the convex portion, the surface of the light emitting portion of the light source, and the surface of the light receiving portion of the photodetector are substantially parallel among the surfaces facing the scale of the light transmitting resin,
The thickness from the surface of the light emitting portion of the light source to the surface facing the scale of the convex portion of the light transmitting resin is t122,
The thickness from the surface of the light receiving portion of the photodetector to the surface facing the scale of the convex portion of the light transmitting resin is t222,
The longest distance among the distances in the direction parallel to the surface of the light transmitting resin from an arbitrary point of the light emitting part of the light source to the light receiving part of the photodetector is de,
The refractive index of the outside medium is n1,
When the refractive index of the light transmitting resin is n2, respectively.
tan ⁻¹ (de / (t122 + t222)) <sin ⁻¹ (n1 / n2)
An optical encoder characterized by satisfying the following conditional expression can be provided.

According to the fourth aspect of the present invention, at least one light source and at least one photodetector are composed of a sensor head made of a package integrated with a light transmitting resin, and a scale that is displaced relative to the sensor head. In the optical encoder that reflects and diffracts the light emitted from the light emitting part of the light source with a scale, receives the reflected and diffracted light with the light receiving part of the photodetector, and outputs a displacement signal from the sensor head,
At least a part of the surface between the light emitting part of the light source and the light receiving part of the photodetector among the surfaces facing the scale of the light transmitting resin has a concave part,
Of the surfaces facing the scale of the light transmitting resin, the surface of the concave portion, the surface of the light emitting portion of the light source, and the surface of the light receiving portion of the photodetector are substantially parallel,
The thickness from the surface of the light emitting part of the light source to the surface facing the scale of the concave part of the light transmitting resin is t13,
The thickness from the surface of the light receiving portion of the photodetector to the surface of the concave portion of the light transmitting resin with respect to the scale is t23,
When the shortest distance among the distances in the direction parallel to the surface of the light transmitting resin from an arbitrary point of the light emitting portion of the light source to the light receiving portion of the photodetector is ds ,
1.73 × (t13 + t23) <ds
An optical encoder characterized by satisfying the following conditional expression can be provided.

  The optical encoder according to the present invention is a so-called reflective optical encoder, and among the light emitted from an arbitrary point of the light emitting portion of the light source, the light totally reflected at the interface between the light-transmitting resin and the outside world, The light emitting part of the light source and the light receiving part of the photodetector are arranged so as to be incident on a part of the light receiving part of the photodetector or in a different area from the light receiving part, and light transmission It is characterized by satisfying at least one of the resin shape being formed and the optical property of the light transmitting resin being set. Thereby, the light totally reflected at the interface between the light transmitting resin and the outside is incident on a part of the light receiving part or a region different from the light receiving part. For this reason, it is possible to reduce the DC component of the signal due to the totally reflected light of the signal. As a result, it is possible to provide an optical encoder that prevents displacement signal saturation and has a large displacement signal amplitude with respect to the DC component. In the present invention, the sensor head can be constituted by, for example, a mold. As a result, the number of parts and the manufacturing process can be reduced, so that an inexpensive optical encoder can be provided.

  Embodiments of an optical encoder according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  FIG. 1 shows a schematic configuration of an optical encoder 100 according to Embodiment 1 of the present invention. The optical encoder 100 includes a sensor head 101 and a scale 110 disposed so as to face the sensor head 101. In the sensor head 101, a light source 104 having a light emitting portion 141 and a photodetector 103 having a light receiving portion 131 inside are separately provided on the wiring board 102. The light source 104 and the photodetector 103 are configured as a package in which an interface 151 with the outside world is integrated with a light-transmitting resin 105 having a flat shape. The scale 110 has a lattice pattern 111 that is displaced relative to the sensor head 101. The lattice pattern 111 is an optical pattern formed at a predetermined pitch with respect to the direction in which the scale 110 and the sensor head 101 move relative to each other.

  The scale 110 reflects and diffracts the light Ls emitted from the light emitting unit 141 of the light source 104 by the grating pattern 111. Here, as the light source 104, for example, a point light source such as an LED can be used. The light receiving unit 131 of the photodetector 103 receives the reflected and diffracted light Lsr. In other words, the photodetector 103 detects the movement of the self image formed on the light receiving unit 131 by the light reflected and diffracted by the grating pattern 111. The sensor head 101 outputs an analog or digital displacement signal as shown in FIGS. 16B and 16C.

  FIG. 3 shows an enlarged view of the light receiving element array of the light receiving unit 131 formed on the photodetector 103. The light receiving element array is configured by combining a plurality of, for example, four rectangular photodiodes PD1, PD2, PD3, and PD4.

  The photodiodes PD1, PD2, PD3, and PD4 are arranged in a comb-teeth shape with a shift of ¼ × p1. Then, electric signals from the respective photodiodes PD1, PD2, PD3, and PD4 are output from the four electrode pads A1, B1, A2, and B2.

  When the scale 110 moves relative to each other, pseudo sine wave signals whose phases are different from each other by a quarter period are obtained from the four electrode pads A1, B1, A2, and B2. Thereby, it is possible to detect the direction of displacement (discrimination of the moving direction). Furthermore, by performing output signal interpolation processing (displacement amount interpolation processing), the displacement amount can be detected with a resolution much finer than the pitch of the grid pattern 111 formed on the scale 110. . As described above, the optical encoder 100 is a so-called reflective optical encoder.

  Further, as shown in FIG. 1, the surface of the light emitting portion 141 of the light source 104, the surface of the light receiving portion 131 of the photodetector 103, and the interface 151 between the outside of the light transmitting resin 105 are configured to be parallel. ing.

here,
The refractive index of the light transmitting resin 105 of the sensor head 101 is n2,
The refractive index of the external medium is n1 (in general, since the medium is air, n1≈1),
The thickness from the surface (interface 151) facing the scale 110 of the light transmitting resin 105 to the surface of the light emitting portion 141 is t11,
The thickness from the surface (interface 151) to the surface of the light receiving unit 131 of the photodetector 103 is t21,
An interval (distance) in a direction parallel to the surface (interface 151) from an arbitrary point of the light emitting unit 141 of the light source 104 to the center of the light receiving unit 131 of the photodetector 103 is dc,
The light La emitted from an arbitrary point 141p of the light emitting part 141 of the light source 104 within the interval dc is reflected by the surface (interface 151) of the light transmitting resin 105 and is incident on the center 131a of the light receiving part 131 of the photodetector 103. The distance of the light Lb2 in the direction along the normal line 106 to the reflection point 107 on the surface (interface 151) of the light transmitting resin 105 is d11,
In the interval dc, the interval in the direction along the normal line 106 from the center 131a of the light receiving portion 131 of the photodetector 103 to the reflection point 107 on the surface (interface 151) of the light transmitting resin 151 is denoted as d21.

  Further, the light La emitted from the light emitting portion 141 of the light source 104 has an angle between the surface 151 of the light transmitting resin 105 and the normal line 106 of the interface 151 at θ2 at the interface 151 between the surface of the light transmitting resin 105 and the outside medium. At this time, the angle of the light Lb2 reflected at the interface 151 of the light transmitting resin 105 with respect to the normal line 106 of the interface 151 of the light transmitting resin 105 is θ2.

Accordingly, the relationship satisfies the following expression (4) geometrically.
tan θ2 = d11 / t11
= D21 / t21 (4)

Since dc = d11 + d21, the following expression is obtained from the equation (4).
dc = (t11 + t21) · tan θ2
θ2 = tan ⁻¹ (dc / (t11 + t21)) (5)

Here, the refractive index n2 of the light transmitting resin 105 is larger than air (n1≈1) (n2> n1). Therefore, as described above, the light La is totally reflected on the surface (interface 151) of the light transmitting resin 105 in the range of the angle θ2 that satisfies the expression (3). Therefore, the arrangement of the light receiving unit 131 of the photodetector 103 and the light emitting unit 141 of the light source 104 satisfying the following expression (6) and the thicknesses t11 and t21 of the light transmitting resin 105 are used. As a result, of the light La emitted from the light emitting part 141 of the light source 104, the light totally reflected by the surface (interface 151) of the light transmitting resin 105 is only received from the center of the light receiving part 131 on the side opposite to the light source 104. Is incident on. As a result, as shown in FIG. 2, it is possible to prevent the total reflected light from entering the region 150 (shaded portion) of the light receiving unit 131 on the light source 104 side. FIG. 2 is a plan view of the photodetector 103 and the light source 104. In all the plan views below, for the sake of convenience, the straight line passing through the reflection point 107 will be described with the reference numeral normal 106.
tan ⁻¹ (dc / (t11 + t21)) <sin ⁻¹ (n1 / n2) (6)

  The intensity of light emitted from the light source 104 generally decreases in inverse proportion to the square of the distance. For this reason, the intensity of light that is totally reflected at the surface (interface 151) of the light transmitting resin 105 and incident on the light receiving portion 131 is reflected by the lattice pattern 111 of the scale 110 and is incident on the light receiving portion 131 and contributes to the displacement signal. It is very large compared to the light that plays. Therefore, the above-described DC component can be reduced by preventing the total reflection light from entering from the surface (interface 151) of the light transmitting resin 105 to the region 150 of the light receiving unit 131 close to the light source 104 side.

As described above, in this embodiment, the light that is totally reflected at the interface 151 between the light transmitting resin 105 and the outside of the light emitted from the arbitrary point 141p of the light emitting unit 141 of the light source 104 is detected by the photodetector 103. At least one of the following (a), (b), and (c) is satisfied so as to be incident on a part of the light receiving unit 131 or in a region different from the light receiving unit 131 It is desirable.
(A) The light emitting part 141 of the light source 104 and the light receiving part 131 of the photodetector 103 are arranged. (B) The shape of the light transmitting resin 151 is formed. (C) The optical property of the light transmitting resin 151. Properties such as refractive index are set

  In this embodiment, the totally reflected light is incident on a part of the light receiving unit 131 of the photodetector 103 so that the light totally reflected at the interface 151 is incident on a part of the light receiving unit 131 of the photodetector 103. As described above, the light emitting unit 141 of the light source 104 and the light receiving unit 131 of the photodetector 103 are arranged, and the light transmitting resin 151 has a shape, for example, a thickness. Thereby, the DC component of the displacement signal can be reduced as described above.

  Next, the operation of the embodiment will be described. The arrangement of the light receiving unit 131 of the light detector 103 and the light emitting unit 141 of the light source 104 and the thicknesses t11 and t12 of the light transmitting resin 151 are set so as to satisfy Expression (6). Thereby, of the light La emitted from the light emitting part 141 of the light source 104, the light totally reflected by the surface (interface 151) of the light transmitting resin 105 is received by the light source 141 side from the center 131a of the light receiving part 131. It is configured to prevent the part 131 from entering the region 150. For this reason, the saturation of the signal can be prevented by reducing the DC component of the displacement signal. As a result, a displacement signal having a large amplitude with respect to the DC component can be obtained even in a signal processing circuit having a low operating voltage. Further, the sensor head configuration of the present embodiment is a configuration in which the light source 104 and the photodetector 103 on the wiring substrate 102 are covered with the same light transmitting resin 105 by a method such as molding. For this reason, since the number of parts and a manufacturing process are few, an optical encoder can be manufactured cheaply.

  In addition, naturally each deformation | transformation of an Example can be variously modified and changed. The number of light sources 104 and photodetectors 103 is not limited to one, and a large number of them may be arranged. The number of lattice patterns 111 of the scale 110 is not limited to one, and various types may be formed. In addition to the light receiving unit 131, the photodetector 103 may include a circuit that converts an analog signal into a digital signal, an interpolation / division circuit, a driver for the light source 104, and the like. Further, as a method of electrically connecting the photodetector 103 to the wiring substrate 102, in addition to the connection using a conductive wire, a backside wiring may be applied to the photodetector 103 and connected to the wiring substrate 102 by soldering or the like. Further, the method of forming the light transmissive resin 105 is not limited to molding, and a method such as potting may be used. After the light transmissive resin is collectively formed on the collective wiring board from which a large number of sensor heads can be obtained, A method of obtaining the sensor head 101 by cutting out the permeable resin at the same time may be used.

  An optical encoder 200 according to Embodiment 2 of the present invention will be described with reference to FIGS. The same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. The optical encoder 200 includes a sensor head 101 and a scale 110. The sensor head 101 is a light-transmitting resin 105 that has a light source 104 having a light emitting portion 141 on a wiring substrate 102 and a photodetector 103 having a light receiving portion 131 therein, and has a flat interface with the outside. It consists of an integrated package. The scale 110 has a lattice pattern 111 that is displaced relative to the sensor head 101.

  The light Ls emitted from the light emitting unit 141 of the light source 104 is reflected and diffracted by the scale 110, and the reflected and diffracted light Lsr is received by the light receiving unit 131 of the photodetector 103. The sensor head 101 is a reflective optical encoder that outputs an analog or digital displacement signal as shown in FIGS. 16B and 16C.

  The difference between the present embodiment and the first embodiment is that, of the light La, the light totally reflected on the surface (interface 151) of the light transmitting resin 105 is prevented from entering the entire surface of the light receiving unit 131. The arrangement of the light source 104 and the photodetector 103 and the thicknesses t111 and t211 of the light transmitting resin 105 are set. In other words, the light totally reflected by the interface 151 is configured to enter a region different from that of the light receiving unit 131.

  Of the distance from the arbitrary point 141p of the light emitting part 141 of the light source 104 to the light receiving part 131 of the photodetector 103, it is parallel to the surface (interface 151) to the light receiving part 131 farthest from the light emitting part 141. Let de be the interval in the direction.

  Further, the light La emitted from an arbitrary point 141p of the light emitting portion 141 of the light source 104 within the interval de is reflected by the surface (interface 151) of the light transmitting resin 105. The light Lb2 is incident on a position 131b farthest from the light emitting unit 141 of the light receiving unit 131 of the photodetector 103. Here, the distance in the direction along the normal line 106 from the arbitrary point 141p to the reflection point 107 on the surface (interface 151) of the light transmitting resin 105 is defined as d111.

  Further, in the interval de, the interval in the direction along the normal line 106 from the reflection point 107 to the position 131b farthest from the light emitting unit 141 of the light receiving unit 131 of the photodetector 103 is defined as d211.

The light La emitted from an arbitrary point 141p of the light emitting portion 141 of the light source 104 has an angle with the direction along the normal line 106 of the interface at the interface 151 between the surface of the light transmitting resin 105 and the outside air. Let θ2. At this time, the angle of the light Lb2 reflected from the surface of the light transmitting resin 105 and the direction along the normal line 106 of the surface (interface 151) of the light transmitting resin 105 is θ2. Therefore, the following relationship is geometrically obtained.
tan θ2 = d111 / t111
= D211 / t211 (7)

Further, since de = d111 + d211, the following expression is obtained from the expression (7).
de = (t111 + t211) · tan θ2
θ2 = tan ⁻¹ (de / (t111 + t211)) (8)

  Here, the refractive index n2 of the light transmitting resin 105 is larger than air (n1≈1) (n2> n1). Therefore, as described above, the light La is totally reflected on the surface (interface 151) of the light transmitting resin 105 in the range of θ2 that satisfies the expression (3).

Therefore, the arrangement of the light receiving unit 131 of the photodetector 103 and the light emitting unit 141 of the light source 104 satisfying the following expression (9) and the light transmitting resin thicknesses t111 and t211 are used. Thereby, it is possible to prevent the light La emitted from an arbitrary point 141p of the light emitting unit 141 of the light source 104 from being totally reflected by the surface (interface 151) of the light transmitting resin 105 and entering the light receiving unit 131. .
tan ⁻¹ (de / (t111 + t211)) <sin ⁻¹ (n1 / n2) (9)

  By adopting such a configuration, as described in the first embodiment, the DC component of the displacement signal is reduced to prevent signal saturation, and even a low voltage operation signal processing circuit has a displacement with a larger amplitude than the DC component. A signal is obtained.

  Further, in the present embodiment, the light La that is totally reflected by the surface (interface 151) of the light transmitting resin 105 in the light La is prevented from being incident on the entire surface of the light receiving unit 131. For this reason, fluctuations of the DC component can be prevented, and the S / N ratio of the displacement signal is improved. Therefore, it is possible to achieve high division using an analog signal multiplication circuit, and to obtain an optical encoder with high resolution and high accuracy.

  This embodiment has the same operation as that of the first embodiment, and the S / N ratio of the displacement signal is improved, so that a high resolution and high accuracy encoder can be obtained. Each configuration of the present embodiment can be variously modified and changed similarly to the first embodiment.

  An optical encoder 300 according to Embodiment 3 of the present invention will be described with reference to FIGS. The same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. As in the first embodiment, the optical encoder 300 includes a light source 104 having a light emitting portion 141 and a photodetector 103 having a light receiving portion 131 arranged separately on the wiring board 102, and a light transmitting resin 105. And a scale 110 having a lattice pattern that is displaced relative to the sensor head 101.

  The light Ls emitted from the light emitting unit 141 of the light source 104 is reflected and diffracted by the scale 110, and the reflected and diffracted light Lsr is received by the light receiving unit 131 of the photodetector 103. The sensor head 101 is a reflective optical encoder that outputs an analog or digital displacement signal as shown in FIGS. 16B and 16C.

  The difference between the present embodiment and the first embodiment is that the thickness of a part of the light transmitting resin 105 between the light emitting section 141 of the light source 104 and the light receiving section 131 of the photodetector 103 is increased (increased). It is the point which forms a shape part.

  For example, when the surface of the light transmitting resin 105 is flattened (that is, when there is no convex portion), the light La emitted from an arbitrary point 141p of the light emitting portion 141 of the light source 104 is reflected by the light transmitting resin 105. Consider a case where light is totally reflected (angle θcr or more) at the surface 155 (indicated by a dotted line in FIG. 8) to become light Lb2. In this case, the light source 104 and the photodetector 103 are arranged such that the light Lb2 enters the light receiving unit 131 of the photodetector 103.

In this embodiment, in such a case, the thickness of the light transmitting resin 105 is set so as to satisfy the formula (10) with respect to the resin thickness of the surface 152 of the light transmitting resin 105. As a result, it is possible to prevent the light La emitted from the light emitting portion 141 of the light source 104 from being totally reflected by the surface 152 of the light transmitting resin 105 from entering the region of the light receiving portion 131.
θ2 <sin ⁻¹ (n1 / n2) (10)

Therefore, as in the first embodiment, the arrangement of the light receiving unit 131 of the photodetector 103 and the light emitting unit 141 of the light source 104 satisfying the following expression (11) and the thicknesses t12 and t22 of the light transmitting resin 105 are used. As a result, the light La emitted from the light emitting portion 141 of the light source 104 is totally reflected by the surface 152 of the light transmitting resin 105, and then goes from the center 131 a of the light receiving portion 131 to the region 150 of the light receiving portion 131 that is substantially half on the light source 104 side. Can be prevented.
tan ⁻¹ (dc / (t12 + t22)) <sin ⁻¹ (n1 / n2) (11)

  The operation of the present embodiment has the same operation as that of the first embodiment, and the degree of freedom in designing the arrangement of the photodetector 103 and the light source 104 can be made larger than that of the first embodiment. Each configuration of the present embodiment can be variously modified and changed similarly to the first embodiment. Moreover, the cross-sectional shape of the convex portion is not limited to a rectangular shape. For example, the cross-sectional shape of the convex portion may be a trapezoidal shape or a shape in which the step portion has a curvature.

  An optical encoder 400 according to Embodiment 4 of the present invention will be described with reference to FIGS. The same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. In the optical encoder 400 shown in FIG. 8, the light source 104 having the light emitting portion 141 and the photodetector 103 having the light receiving portion 131 inside are separately arranged on the wiring board 102 and integrated with the light transmitting resin 105. The sensor head 101 is composed of a package and a scale 110 having a lattice pattern that is displaced relative to the sensor head 101.

  The light Ls emitted from the light emitting unit 141 of the light source 104 is reflected and diffracted by the scale 110, and the reflected and diffracted light Lsr is received by the light receiving unit 131 of the photodetector 103. The sensor head 101 is a reflective optical encoder that outputs an analog or digital displacement signal as shown in FIGS. 16B and 16C.

  The difference between the present embodiment and the third embodiment is that the light source 104 is configured to prevent the light La totally reflected by the surface 152 of the light transmitting resin 105 from entering the entire surface of the light receiving portion 131 in the light La. And the photodetector 103, and the thicknesses t122 and t222 of the light transmitting resin 105 are set. In other words, in the present embodiment, the light totally reflected by the surface 152 is configured to enter a region different from the light receiving unit 131.

For this reason, as described in the second and third embodiments, the arrangement of the light receiving unit 131 of the photodetector 103 and the light emitting unit 141 of the light source 104 that satisfy the following relational expression, and the thickness t122 of the light transmitting resin 105, t222. Thereby, the light La emitted from an arbitrary point 141p of the light emitting part 141 of the light source 104 can be prevented from entering the light receiving part 131 after being totally reflected by the surface (interface 151) of the light transmitting resin 105. .
tan ⁻¹ (de / (t122 + t222)) <sin ⁻¹ (n1 / n2) (12)

  The operation of this embodiment is the same as that of the second and third embodiments. Each configuration of the present embodiment can be variously modified and changed similarly to the first embodiment.

  An optical encoder 500 according to Embodiment 5 of the present invention will be described with reference to FIGS. The same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. As in the first embodiment, the optical encoder 500 includes a light source 104 having a light emitting portion 141 and a photodetector 103 having a light receiving portion 131 arranged separately on the wiring board 102 and is made of a light transmitting resin 105. The sensor head 101 includes an integrated package, and a scale 110 having a lattice pattern that is displaced relative to the sensor head 101.

  The light Ls emitted from the light emitting unit 141 of the light source 104 is reflected and diffracted by the scale 110, and the reflected and diffracted light Lsr is received by the light receiving unit 131 of the photodetector 103. The sensor head 101 is a reflective optical encoder that outputs an analog or digital displacement signal as shown in FIGS. 16B and 16C.

  This embodiment is different from the first embodiment in that a part of the light transmitting resin 105 between the light emitting portion 141 of the light source 104 and the light receiving portion 131 of the photodetector 103 is thinned to form a concave portion. It is a point.

  FIG. 12 shows the approximate light intensity in the radiation angle direction as a vector length when an optical member such as a lens is not used in a general light source, for example, an LED. Here, the light intensity in the direction of 90 degrees, that is, in the normal direction with respect to the exit surface of the light exit portion 141 is set to 1.0. The radiation angle at which the radiation intensity is about 50% of the half value is about 30 degrees. In general, light having a light intensity of half or less is light that is sufficiently weaker than light having a half value or more. For this reason, even if light having a light intensity of half or less is incident on the light receiving unit 131, it does not greatly contribute to the DC component.

When ds is the closest (small) distance from an arbitrary point 141p of the light emitting unit 141 of the light source 104 to the light receiving unit 131 of the photodetector 103,
ds = d13 + d23
It becomes.

Also,
tan 60 ° = t13 / d13
= From t23 / d23 1.73≈t13 / d13
≒ t23 / d23
It becomes.

For this reason, what is necessary is just to make it the structure which satisfy | fills Formula (13).
ds> 1.73 (t13 + t23) (13)

  The operation of the present embodiment is the same as that of the third embodiment. In this embodiment, the radiation angle is small, and the totally reflected light is incident on the light receiving unit 131. However, as described above, even when light having a small radiation angle and a light intensity equal to or less than half value is incident on the light receiving unit 131, it does not greatly contribute to the DC component. For this reason, the saturation of the displacement signal can be prevented by reducing the DC component. Each configuration of the present embodiment can be variously modified and changed similarly to the first embodiment.

  An optical encoder 600 according to Embodiment 6 of the present invention will be described with reference to FIGS. The same parts as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. In the optical encoder 600, the light detector 104 having the light receiving unit 131 inside on the wiring board 102 and the light source 104 having the optical member 108 having the slit pattern 181 on at least the light emitting unit 141 are arranged separately. The sensor head 101 is made of a package integrated with the light transmitting resin 105, and the scale 110 has a lattice pattern 111 that is displaced relative to the sensor head 101. The light Ls emitted from the light emitting unit 141 of the light source 104 is reflected and diffracted by the scale 110, and the reflected and diffracted light Lsr is received by the light receiving unit 131 of the photodetector 103. The sensor head 101 is a reflective optical encoder that outputs an analog or digital displacement signal as shown in FIGS. 16B and 16C.

  The difference between the present embodiment and the first embodiment is that the optical member 108 having the slit pattern 181 is disposed on the light emitting portion 141. If a glass material or the like having substantially the same refractive index as the light transmitting resin 105 is used for the optical member 108, refraction at the interface between the optical member 108 and the light transmitting resin 105 hardly occurs.

  Therefore, in the configuration of the present embodiment as well as the first embodiment, the arrangement of the light receiving unit 131 of the photodetector 103 and the light emitting unit 141 of the light source 141 that satisfy the relational expression (6) and the thickness of the light transmitting resin 105 are satisfied. Let t11 and t21. Thereby, the light La emitted from the light emitting portion 141 of the light source 104 is totally reflected at the interface 151 of the light transmitting resin 105, and the region 150 of the light receiving portion 131 that is substantially half from the center 131 a of the light receiving portion 131 to the light source 141 side. Can be prevented.

  In addition, the slit pattern 181 formed on the optical member 108 has a shape corresponding to the lattice pattern 111 of the scale 110, the interval between the scale 110 and the slit pattern 181 or the light receiving portion 131, etc., in order to obtain a good encoder signal. Is desirable.

  The operation of this embodiment is the same as that of the first embodiment. Further, in order to obtain a good encoder signal, it is determined by the slit pattern shape 181 formed in the optical member 108. For this reason, it does not depend on the shape of the light emitting part 141 of the light source 104. Accordingly, the options for the light source 104 are expanded.

  Each configuration of the present embodiment can be variously modified and changed similarly to the first embodiment. Moreover, it is good also as a structure like the convex part which has the surface 152 of Example 3 and Example 5, and the concave part which has the surface 153.

  More preferably, the optical member 108 has a configuration in which the optical member 108 is directly attached to the light source 104 or a configuration in which the light transmitting resin 105 is interposed between the light source 104 and the optical member 108. Further, the slit pattern 181 may be formed on either surface of the optical member 108 on the light source 104 side or on the opposite side of the light source 104. In addition, the optical member 108 may be a thin plate having a slit opening.

  More strictly, it is desirable to correct the left side of the expression (6) in the same way as the geometric method described in the first embodiment in consideration of the difference in refractive index between the optical member 108 and the light transmitting resin 105. .

  In each of the above embodiments, the light totally reflected at the interface between the light transmitting resin 105 and the outside is incident on a part of the light receiving unit 131 of the photodetector 103 or in a different region from the light receiving unit 131. A light transmitting resin 105 having an optical characteristic, for example, a refractive index n2, which is incident may be used. At this time, it is desirable to set the thickness of the light transmitting resin 105 and the distance between the light source 104 and the photodetector 103 by using the refractive index n2 as a variable parameter. As described above, the present invention can be variously modified without departing from the spirit of the present invention.

  As described above, the optical encoder according to the present invention is useful for an inexpensive reflective optical encoder.

1 is a diagram illustrating a schematic configuration of an optical encoder according to Embodiment 1. FIG. FIG. 3 is a plan view of a light source and a light detection unit according to the first embodiment. 3 is an enlarged plan view illustrating a configuration of a light receiving unit according to Embodiment 1. FIG. 6 is a diagram illustrating a schematic configuration of an optical encoder according to Embodiment 2. FIG. It is a top view of the light source and light detection part of Example 2. FIG. 10 is a diagram illustrating a schematic configuration of an optical encoder according to a third embodiment. It is a top view of the light source and light detection part of Example 3. FIG. 10 is a diagram illustrating a schematic configuration of an optical encoder according to a fourth embodiment. It is a top view of the light source and light detection part of Example 4. FIG. 10 is a diagram illustrating a schematic configuration of an optical encoder according to a fifth embodiment. It is a top view of the light source and light detection part of Example 5. It is a figure which shows the intensity | strength of the emitted light of the light source of Example 5. FIG. FIG. 10 is a diagram illustrating a schematic configuration of an optical encoder according to a sixth embodiment. It is a top view of the light source and light detection part of Example 6. It is a figure explaining Snell's law. (A) is a schematic configuration of the optical encoder, (b) is an analog signal, and (c) is a diagram showing a digital signal. (A) is a figure explaining a DC component, (b) is a figure explaining saturation of a displacement signal. (a), (b) is a figure which shows schematic structure of the optical encoder of a prior art.

Explanation of symbols

100, 200, 300, 400, 500, 600 Optical encoder 101 Sensor head 102 Wiring board 103 Photo detector 104 Light source 105 Light transmitting resin 106 Normal 107 Reflection point 110 Scale 111 Grid pattern 131 Light receiving part 131a Light receiving part center 131b Position of light receiving part 131c closest to light receiving part 141 Light emitting part 141p Arbitrary point 150 Region 151 Surface 155 Interface PD1, PD2, PD3, PD4 Photodiode t21, t11, t11, t12, t23, t13, t211 , T111 Thickness d11, d12, d22, d12, d23, d13, d211, d111 Distance n1 Refractive index of medium outside n2 Refractive index of light transmitting resin Ls, Lsr, La, Lb1, Lb2 Light 60 Light transmitting resin 70 Light source 75 Photodetector 80 Interface 90 Encoder 91 Scale 92 Sensor head 24 Light emitting element 26 Light receiving element 28 Reflecting mirror 30 Lead frame

Claims (8)

A sensor head comprising a package in which at least one light source and at least one photodetector are arranged side by side and integrated with a light-transmitting resin, and a scale that is displaced relative to the sensor head, from a light emitting portion of the light source In the optical encoder that reflects and diffracts the emitted light by the scale, receives the reflected and diffracted light by the light receiving unit of the photodetector, and outputs a displacement signal from the sensor head,
Of the light emitted from an arbitrary point of the light emitting part of the light source, the light totally reflected at the interface between the light transmitting resin and the outside enters the at least part of the light receiving part of the photodetector, and , the center of the light receiving portion of the photodetector to be incident to the outside when viewed from the light source side, spacing and the light transmitting resin and the light receiving portion of the photodetector and the light emitting portion of the light source An optical encoder, wherein a relationship between a thickness and a refractive index of the light transmitting resin is set.   The optical encoder according to claim 1, wherein a surface of the light transmitting resin facing the scale is substantially flat. The surface of the light transmitting resin facing the scale, the surface of the light emitting part of the light source, and the surface of the light receiving part of the photodetector are substantially parallel,
The thickness from the surface of the light emitting part of the light source to the surface of the light transmitting resin facing the scale is t11,
The thickness from the surface of the light receiving portion of the photodetector to the surface of the light transmitting resin facing the scale is t21,
A distance in a direction parallel to the surface of the light transmitting resin from an arbitrary point of the light emitting portion of the light source to the center of the light receiving portion of the photodetector, dc,
The refractive index of the outside medium is n1,
When the refractive index of the light transmitting resin is n2, respectively.
tan ⁻¹ (dc / (t11 + t21)) <sin ⁻¹ (n1 / n2)
The optical encoder according to claim 2, wherein the following conditional expression is satisfied. The surface of the light transmitting resin facing the scale, the surface of the light emitting part of the light source, and the surface of the light receiving part of the photodetector are substantially parallel,
The thickness from the surface of the light emitting portion of the light source to the surface of the light transmitting resin facing the scale is t111,
The thickness from the light receiving portion surface of the photodetector to the surface of the light transmitting resin facing the scale is t211;
The longest distance among the distances in the direction parallel to the surface of the light transmitting resin from an arbitrary point of the light emitting portion of the light source to the light receiving portion of the photodetector is de,
The refractive index of the outside medium is n1,
When the refractive index of the light transmitting resin is n2, respectively.
tan ⁻¹ (de / (t111 + t211)) <sin ⁻¹ (n1 / n2)
The optical encoder according to claim 2, wherein the following conditional expression is satisfied.   At least a part of the surface between the light emitting part of the light source and the light receiving part of the photodetector among the surfaces of the light transmitting resin facing the scale has a convex part. The optical encoder according to claim 1, wherein A sensor head comprising a package in which at least one light source and at least one photodetector are arranged side by side and integrated with a light-transmitting resin, and a scale that is displaced relative to the sensor head, from a light emitting portion of the light source In the optical encoder that reflects and diffracts the emitted light by the scale, receives the reflected and diffracted light by the light receiving unit of the photodetector, and outputs a displacement signal from the sensor head,
Of the light emitted from an arbitrary point of the light emitting part of the light source, the light totally reflected at the interface between the light transmitting resin and the outside is from the light source side than the center of the light receiving part of the photodetector. The relationship between the distance between the light emitting part of the light source and the light receiving part of the photodetector, the thickness of the light transmitting resin, and the refractive index of the light transmitting resin is set so as to be incident on the outside.
At least a part of the surface between the light emitting part of the light source and the light receiving part of the photodetector among the surfaces of the light transmitting resin facing the scale has a convex part,
The surface of the convex portion, the surface of the light emitting portion of the light source, and the surface of the light receiving portion of the photodetector are substantially parallel among the surfaces of the light transmitting resin facing the scale,
The thickness from the surface of the light emitting part of the light source to the surface of the convex part of the light transmitting resin facing the scale is t12,
The thickness from the surface of the light receiving portion of the photodetector to the surface of the convex portion of the light transmitting resin facing the scale is t22,
A distance in a direction parallel to the surface of the light transmitting resin from an arbitrary point of the light emitting portion of the light source to the center of the light receiving portion of the photodetector, dc,
The refractive index of the outside medium is n1,
When the refractive index of the light transmitting resin is n2, respectively.
tan ⁻¹ (dc / (t12 + t22)) <sin ⁻¹ (n1 / n2)
An optical encoder that satisfies the following conditional expression: A sensor head comprising a package in which at least one light source and at least one photodetector are arranged side by side and integrated with a light-transmitting resin, and a scale that is displaced relative to the sensor head, from a light emitting portion of the light source In the optical encoder that reflects and diffracts the emitted light by the scale, receives the reflected and diffracted light by the light receiving unit of the photodetector, and outputs a displacement signal from the sensor head,
Of the light emitted from an arbitrary point of the light emitting part of the light source, the light totally reflected at the interface between the light transmitting resin and the outside is from the light source side than the center of the light receiving part of the photodetector. The relationship between the distance between the light emitting part of the light source and the light receiving part of the photodetector, the thickness of the light transmitting resin, and the refractive index of the light transmitting resin is set so as to be incident on the outside.
At least a part of the surface between the light emitting part of the light source and the light receiving part of the photodetector among the surfaces of the light transmitting resin facing the scale has a convex part,
The surface of the convex portion, the surface of the light emitting portion of the light source, and the surface of the light receiving portion of the photodetector are substantially parallel among the surfaces of the light transmitting resin facing the scale,
The thickness from the surface of the light emitting part of the light source to the surface of the convex part of the light transmitting resin facing the scale is t122,
The thickness from the surface of the light receiving portion of the photodetector to the surface of the convex portion of the light transmitting resin facing the scale is t222,
The longest distance among the distances in the direction parallel to the surface of the light transmitting resin from an arbitrary point of the light emitting portion of the light source to the light receiving portion of the photodetector is de,
The refractive index of the outside medium is n1,
When the refractive index of the light transmitting resin is n2, respectively.
tan ⁻¹ (de / (t122 + t222)) <sin ⁻¹ (n1 / n2)
An optical encoder that satisfies the following conditional expression:   A sensor head composed of a package in which at least one light source and at least one photodetector are integrated with a light-transmitting resin, and a scale that is displaced relative to the sensor head, and is emitted from a light emitting portion of the light source. In the optical encoder that reflects and diffracts the light with the scale, receives the reflected and diffracted light with the light receiving unit of the photodetector, and outputs a displacement signal from the sensor head,
  At least a part of the surface between the light emitting part of the light source and the light receiving part of the photodetector among the surfaces of the light transmitting resin facing the scale has a concave part,
  The surface of the concave portion of the surface of the light transmitting resin facing the scale, the surface of the light emitting portion of the light source, and the surface of the light receiving portion of the photodetector are substantially parallel,
  The thickness from the surface of the light emitting portion of the light source to the surface of the concave portion of the light transmitting resin facing the scale is t13,
  The thickness from the surface of the light receiving portion of the photodetector to the surface of the concave portion of the light transmitting resin with respect to the scale is t23,
  When the shortest distance among the distances in a direction parallel to the surface of the light transmitting resin from an arbitrary point of the light emitting portion of the light source to the light receiving portion of the photodetector is ds,
  1.73 × (t13 + t23) <ds
An optical encoder that satisfies the following conditional expression:

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