JP2010243323A - Optical encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a miniature optical encoder that has a stable performance by suppressing deterioration of the performance due to deviations of an optical distance from a first lattice to a second lattice and an optical distance from the second lattice to a third lattice with respect to designed values, and is suitable for mass production. <P>SOLUTION: This triple-slit type optical encoder includes a signal suppression means that suppresses a deterioration of an amplitude level of a detected signal by increasing or decreasing at least one of values of an optical distance z1 from a position for limiting a projection width of emission light at a light emission section side to a lattice of a scale and an optical distance z2 from a lattice of a scale at a light reception section side to a lattice functional face of a light detection section. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical displacement sensor used for displacement detection such as an encoder.

  A common example of an optical encoder according to the prior art is a so-called triple slit method. This includes a light source such as an LED, a first grating disposed in the optical path of light from the light source, a second grating disposed on a scale that receives light from the first grating, and transmitted through the second grating, or And a third grating on which the reflected light is incident, and a photodetector disposed immediately after the third grating. Further, the constituent elements excluding the scale having the second lattice constitute a detection head.

  As a reflective triple slit method, there is one disclosed in Japanese Patent Laid-Open No. 2003-166856. As shown in FIG. 20, the transparent member on which the first grating is formed and the transparent member on which the third grating is formed are formed separately, and the heights of the first and third gratings are aligned to be within the detection head. The arrangement to be arranged is shown. In this configuration, the distance from the first grating to the second grating is set to be equal to the distance from the second grating to the third grating.

  The detection principle of the triple slit type encoder is as follows. The light emitted from the first grating is diffracted by the second grating, an enlarged image of the second grating is formed on the third grating, and the light transmitted through the third grating is detected by the photodetector. The magnified image of the second grating and the third grating are designed to have the same pitch. Then, the amount of displacement is detected by a change in light intensity detected by light detection according to the movement of the scale.

  In the triple slit type encoder, it is an important point to align the heights of the first and third gratings according to the set values. The reason is that the magnification of the image formed on the third grating changes just by slightly deviating from the set value, and the signal amplitude of the light that is transmitted through the third grating and detected by the photodetector decreases. It is because it ends.

  In the reflective triple slit method as disclosed in Japanese Patent Laid-Open No. 2003-166856, the second and third gratings included in the detection head are used in order to perform detection that is not easily affected by the distance between the scale and the detection head. The structure arrange | positioned on the same surface is proposed.

JP 2003-166856 A

  On the other hand, as the current state of the encoder, there is a demand for a small and thin object such as being incorporated in a gap between the joints of the robot. In the conventional encoder, the higher the accuracy, the larger the size of each member, such as using a can package type light source or light receiving element, and the size of the detection head is about 10 mm to 20 mm on a side.

  Substantial downsizing and thinning can be achieved by simply replacing the light source and light receiving element with a bare chip type or surface mount type. However, in the triple slit type encoder, the size and thickness of the slit members forming the first grating and the third grating greatly affect the size of the encoder. Therefore, it is necessary to reduce the size and space of the slit member.

  In a triple slit type encoder configured as shown in Japanese Patent Laid-Open No. 2003-166856 in which the first and third gratings are separated, if the step difference between the first and third gratings deviates from the design value, triple In the slit type encoder, the signal amplitude may be significantly reduced.

Further, even when a specific member having a small thickness unevenness is designed, when the lot is changed or the member is changed, there is a possibility that the amount of step difference between the first lattice and the third lattice changes greatly.
As for encoders having a configuration that is not a triple slit, many high-precision types have a grating corresponding to at least one of the first grating and the third grating on the detection head side. If there is no predetermined relationship between the height of the light source or the first grating on the emission side and the height of the light receiving unit or the third grating on the light receiving side, the detection signal level and the DC component amount included in the detection signal level are controlled as designed. Some things are difficult to control or control.

  The present invention has been made in view of the above, and performance degradation due to a deviation from the design value of the optical distance from the first grating to the second grating and the optical distance from the second grating to the third grating. An object of the present invention is to provide an optical encoder that has stable performance, is small, and is suitable for mass production.

In order to solve the above-described problems and achieve the object, according to the present invention, a detection head attached to either one of a stationary body and a movable body that move relatively,
A scale provided with a grating having an optical pattern with a predetermined pitch in the direction of relative movement, attached to the other side facing the detection head,
The detection head is
A light emitting unit that emits divergent light with a limited emission width in the direction of scale movement of the emitted light, and irradiates the scale with predetermined light; and a light detection unit that includes a grating functional surface and a light receiving unit,
An image of an image formed on the grating functional surface of the light detection unit by irradiating the scale from the emission surface having a limited emission width of the light emitting unit and reflecting the diffracted light by the grating provided on the scale. In the optical encoder in which the light detection unit arranged to detect movement is provided, and a periodic detection signal is output from the light detection unit according to the relative movement amount of the scale,
An optical distance z1 from a position that limits an emission width of diverging light on the light emitting unit side to the grating of the scale;
A signal for reducing deterioration in the amplitude level of the detection signal by increasing or decreasing at least one of the optical distance z2 from the grating of the scale on the light receiving unit side to the grating functional surface of the light detection unit It is possible to provide an optical encoder including a deterioration reducing means.

According to a preferred aspect of the present invention, the signal deterioration reducing means is a member or a space,
It is desirable to adjust the optical distance by changing either the thickness of the member or the space on the optical path, or the interval and the refractive index.

Also, according to a preferred aspect of the present invention, and according to a preferred aspect of the present invention, the signal degradation reducing means is a member or a space,
It is desirable to move at least one position of the emission surface on the light emitting unit side and the lattice function surface of the light detection unit by the signal degradation reducing unit.

  According to a preferred aspect of the present invention, it is desirable to provide a protective member that integrally covers the light emitting unit and the light detection unit.

  According to a preferred aspect of the present invention, it is desirable that the protective member is a light transmissive resin.

  Moreover, according to a preferred aspect of the present invention, it is desirable that the signal deterioration reducing means is formed by shaping the surface shape of the protective member on the scale side into a predetermined shape.

  Moreover, according to a preferred aspect of the present invention, it is desirable that the signal deterioration reducing means is a light transmitting member that is attached to the scale-side surface of the protective member.

  According to a preferred aspect of the present invention, it is desirable that the signal deterioration reducing means is disposed on the optical path inside the head rather than the surface of the protective member.

  According to a preferred aspect of the present invention, it is desirable that the signal degradation reducing means is disposed outside the optical path inside the head rather than the surface of the protection member.

  Further, according to a preferred aspect of the present invention, it is desirable that the signal degradation reducing means is a member or a space arranged so as to have at least one optical refractive index boundary surface on the optical path.

  Also, according to a preferred aspect of the present invention, it is desirable that the signal deterioration reducing means is a member mounted so as to be in contact with the light emitting unit or the surface of the photodetector on the scale side.

  Further, according to a preferred aspect of the present invention, the signal deterioration reducing means includes an optical distance from the light emitting surface side emitting surface to the scale grating, and the light detecting unit side scale grating to the light detecting unit. It is desirable to adjust only one of the optical distances to the grating functional surface.

  According to the present invention, stable performance is achieved by suppressing performance degradation due to deviations from the design values of the optical distance from the first grating to the second grating and the optical distance from the second grating to the third grating. In addition, an optical encoder that is small and suitable for mass production can be provided.

It is a figure which shows the isometric view structure of the optical encoder which concerns on the 1st Embodiment of this invention. It is a figure which shows the cross-sectional structure of the optical encoder which concerns on 1st Embodiment. It is a figure which shows the isometric view structure of the example which replaced the photodetector of the optical encoder which concerns on 1st Embodiment. It is a figure which shows the cross-sectional structure of the example which replaced the photodetector of the optical encoder which concerns on 1st Embodiment. It is a figure explaining the structure and connection of PD array. It is a figure explaining the example of a point light source. It is a figure explaining the example of 1 slit. It is a figure which shows the cross-sectional structure of the conventional optical encoder. It is another figure which shows the cross-sectional structure of the conventional optical encoder. It is a figure which shows the cross-sectional structure of the optical encoder which concerns on the modification 1 of 1st Embodiment. It is a figure which shows the cross-sectional structure of the optical encoder which concerns on the modification 2 of 1st Embodiment. It is another figure which shows the cross-sectional structure of the optical encoder which concerns on the modification 1 of 1st Embodiment. It is a figure which shows the isometric view structure of the optical encoder which concerns on the 2nd Embodiment of this invention. It is a figure which shows the cross-sectional structure of the optical encoder which concerns on the modification 1 of 2nd Embodiment. It is a figure which shows the cross-sectional structure of the optical encoder which concerns on the modification 2 of 2nd Embodiment. It is a figure which shows the cross-sectional structure of the optical encoder which concerns on the modification 3 of 2nd Embodiment. It is a figure which shows the cross-sectional structure of the optical encoder which concerns on the modification 4 of 2nd Embodiment. It is a figure which shows the isometric view structure of the optical encoder which concerns on the 3rd Embodiment of this invention. It is a figure which shows the cross-sectional structure of the optical encoder which concerns on 3rd Embodiment. It is a figure which shows the cross-sectional structure of the conventional optical encoder.

  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.

  First, the optical encoder according to the first embodiment will be described with reference to FIGS. 1, 2, and 3. Moreover, the conventional form which does not include an adjustment member and adjustment space is demonstrated using FIG. 8, FIG.

  FIG. 1 is a perspective view of the optical encoder of the present embodiment. FIG. 2 is a sectional view thereof. As shown in FIG. 1, an x, y, z orthogonal triaxial coordinate system is set.

  In FIG. 1, the optical encoder is roughly divided into a substrate 1, a bare LED 2 which is a bare chip, a light transmission substrate 3 having a first grating 31 having a pitch p1, a photodetector 4 having four light receiving portions, and a pitch p3. The light transmitting substrate 5 having the third grating 51, the light transmitting resin 6, and the scale 7 having the second grating 71 having the pitch p2 are configured.

  Substrate 1, bare LED 2 arranged on substrate 1, light transmitting substrate 3 arranged to protrude in the x direction and y direction on bare LED 2, photodetector 4 arranged on substrate 1, photodetector The light transmissive substrate 5 disposed on 4 is integrally configured as a detection head. The upper part of the detection head is embedded in a light transmitting resin 6 having a refractive index n.

  The first grating 31, the second grating 71, and the third grating 51 are arranged in parallel to each other in the direction of the x direction in the drawing. Regarding the upper surface of the light transmitting resin 6, at least light from the bare LED 2 that is a light source is reflected by the scale 7 and passes through when entering the photodetector 4, and the three gratings 31, 71, 51 is formed in parallel.

The scale 7 can be relatively displaced only in the x direction in a state where the second grating 71 is parallel to the first grating 31 and the third grating 51.
The substrate 1, the bare LED 2, the light transmission substrate 3, the photodetector 4, and the light transmission substrate 5 have a parallel plate shape. These thickness tolerances are about ± 20 μm or less. Then, as shown in FIG. 1 and FIG. The thickness unevenness of the adhesive used for bonding and fixing these members is also about ± 10 μm or less.

  Further, a step is formed in the center on the upper surface of the light transmitting resin 6. Except for this step, the shape is almost flat. As shown in FIG. 2, the step does not significantly affect the light emitted from the head to the scale 7 and the light incident from the scale 7 back to the head at the intermediate portion of the bare LED 2 and the photodetector 4. In the position.

  The size of the step when the enlargement magnification represented by (z1 + z2) / z1 in Expression 2 described later is adjusted to the original design value for the amount of deviation from the design value due to Δzd in Expression 4 described later. (Height) and which of the light source side and the light receiving side is higher is determined.

This step shape is applied when the absolute value of Δzd is large, and if there is no step shape, the signal detection level is lowered and a desired signal or S / N ratio cannot be obtained or there is a possibility of this. .
This level difference is realized by processing such as molding by deforming a mold mold by cutting / pressing the surface shape of a flat light-transmitting resin 6 as shown in FIG. 1, FIG. 2, FIG. 8, and FIG. Can do. A processing method other than those shown here, a means for improving workability by heating, etc. may be used.

  In the light transmissive substrate 3, the first grating 31 is patterned on almost the entire surface on one side of the light transmissive substrate 3, and the first grating 31 is disposed so as to be the LED side surface of the light transmissive substrate 3. The first grating 31 serves as a light emitting part in which a plurality of slits whose output width in the scale moving direction is narrowed are arranged.

  The effective width W1 of the first lattice 31 is the width of the portion of the opening that substantially contributes to the formation of the self-image pattern on the third lattice. Accordingly, the effective width W1 of the first lattice 31 does not necessarily match the width of the opening, and when the opening is large, W1 is smaller than the width of the opening. In this case, the effective width can be obtained theoretically or experimentally.

  In the light transmissive substrate 5, the third grating 51 is composed of four grating groups in such a manner that one surface of the light transmissive substrate 5 is substantially divided into four, and the effective width W3 in the scale moving direction of each grating group is the light transmissive substrate. 5 is about ½ of the width in the direction of scale movement. The third grating 51 is disposed so as to be a surface of the light transmission substrate 5 on the photodetector side.

  Regarding the electrical wiring, the LED 2 and the photodetector 4 are electrically connected to the substrate 1, and the bare LED 2 and the photodetector 4 can be operated. Electrodes are formed on the upper and lower surfaces of the bare LED 2. The electrode on the upper surface and the electrode on the substrate 1 are connected by a conductive wire 8. Further, the electrode on the lower surface and the electrode on the substrate 1 are connected by a conductive paste. There is also a conductive wire connection between the photodetector 4 and the substrate 1, but details are omitted here.

(Principle explanation)
Next, the measurement principle of the optical encoder of the present invention will be described. Hereinafter, the relationship between the change in the magnification of the image and the signal amplitude of the light that passes through the third grating and is detected by the photodetector will be described using equations.

  The optical distance between the first grating 31 and the second grating 71 is z1, the optical distance between the second grating 71 and the third grating 51 is z2, the pitch of the first grating is p1, the pitch of the second grating is p2, The pitch of the third grating is p3, and the wavelength of the light source is λ.

  In this case, it is known that an interference pattern having a period of the pitch p3i is formed on the third grating 51 when the following conditions are satisfied. The definition of “optical distance” used here is shown in Equation 6 and Equation 7.

The pitch p3i of the interference pattern is as follows.

If the pitch p3 of the third grating 51 matches the pitch p3i of the interference pattern, optimal signal detection can be performed.

p3 = p3i (Formula 3)

  An encoder often detects a plurality of phase difference signals. In this case, the third grating 51 may be provided for each individual phase difference signal or may be arranged in an interlaced manner. At this time, the pitch p3 indicates the pitch of the third grating 51 used for detecting one phase signal.

  By the way, when z1 and z2 are slightly deviated from the optimum values due to deviation of the mounting arrangement of the first grating 31 and the third grating 51 in the detection head, the enlargement magnification is changed according to Equation 2. As a result, the relationship of Equation 3 does not hold strictly, and the intensity of the interference pattern detected by the photodetector 4 changes accordingly.

As shown in the following equation, if the difference between the optical distance z1 from the first grating 31 to the second grating 71 and the optical distance z2 from the second grating to the third grating 51 is Δz,

Δz = z2−z1 = Δz0 + Δzd (Formula 4)
| Δzd | ≦ Δzt (Formula 5)
Where Δz0 is the difference based on the design,
Δzd is the actual deviation caused by variation,
Δzt is a tolerance, that is, a maximum allowable value.

In addition, all the distances described here are optical distances.
If the optical path is all in the atmosphere, the actual distance may be used as it is. In general, the detection head is often put in a package, and light may pass through glass or light-transmitting resin. In this case, the optical distance is the total of the space formed by the optical path or the actual length divided by the individual refractive index for each substance.

That is, the i (natural number) -th material between the first lattice 31 and the second lattice 71, or the refractive index ni of the space and the thickness ti,
When the refractive index nj and thickness tj of the j (natural number) -th material between the second grating 71 and the third grating 51 are set, the optical distance between the first grating 31 and the second grating 71 is Σti / ni, The optical distance between the second grating and the third grating is Σtj / nj.

Therefore, in Expression 4 and Expression 5, in order to express Δzd with an actual distance instead of an optical distance, the thickness between the first grating 31 and the second grating 71 is changed by a change in the height of the first grating 31. It is only necessary to multiply the result of Δzd obtained by Expression 4 or Expression 5 by n, where n is the refractive index of the changing member or space.
This is the end of the description of the principle.

Here, the thickness and refractive index of the substance or space interposed between the first grating 31 and the second grating 71 and between the second grating 71 and the third grating 51 will be described.
Between the first grating 31 and the second grating 71, the refractive index of the light transmitting substrate 3 is n1, the thickness is t1, the refractive index of the light transmitting resin 6 is n2, the thickness is t2, and the refraction of air between the head and the scale 7 is performed. The rate is n3 and the thickness is t3.

  In the second lattice 71 and the third lattice 51, the refractive index of the air between the head and the scale 7 is n3, the thickness is t3, the refractive index of the light transmission resin 6 is n2, the thickness is t5, and the refractive index of the light transmission substrate 5 The rate is n1 and the thickness is t4.

  Since the light transmissive substrate 3 and the light transmissive substrate 5 are made of a common material, the refractive index is about 1.5, the refractive index of the light transmissive resin 6 is about 1.5, and the refractive index of air is about 1. The refractive index of the light transmissive substrate 3, the light transmissive substrate 5, and the light transmissive resin is a refractive index of a member that is relatively easily available. However, other values may be used. There may be a difference in refractive index by using another material for the substrate 5.

In the above settings, z1 and z2 are expressed as follows.
z1 = t1 / n1 + t2 / n2 + t3 / n3
z2 = t4 / n1 + t5 / n2 + t3 / n3

  In this example, the design is such that z1 = z2. This is because when the gap between the head / scale changes and z1 and z2 change by the same value, the value of the magnification (z1 + z2) / z1 in Equation 3 does not change, which is advantageous for detection. At this time, p1 = p3, and the following relationship is established for the pitches of the respective lattices together with Expressions 2 and 3.

  p1 = p3 = 2 × p2

  The optical distances z1 and z2 between the respective gratings are obtained using Expressions 6 and 7. Of the components of Δz in Equation 4, the design value of Δz0 is 0 in this example, and only Δzd in the figure exists. Note that Δzd is not a geometric step between the first grating 31 and the third grating 51, but a difference between z1 and z2 that is an optical distance.

The third lattice 51 is composed of four lattice groups. Each grating group has a pitch p3, but the grating groups are arranged so that the phases are different by p3 / 4.
The photodetector 4 has four light receiving parts (not shown). Each light receiving portion is formed on a surface corresponding to each lattice group of the third lattice.

  Similar replacement is possible for the photodetector 4. For example, as shown in FIG. 3, a photodetector including a photodiode array 41 (hereinafter referred to as “PD array” as appropriate) in which a third grating and a light receiving unit are integrated may be used as a component.

  In the example shown in FIGS. 3 and 4, a parallel plate-shaped photodetector 4 having a photodiode array 41 (hereinafter referred to as a PD array) is used. The light receiving surfaces of the first grating 31, the second grating 71, and the PD array are arranged in parallel to each other in the x direction in the drawing.

  In the photodetector 4, the PD array 41 is formed on the upper surface of the photodetector 4 on the scale side so as to occupy a part of the area of the photodetector 4. As shown in FIG. 5, in the PD array 41, light receiving elements PD1, PD2, PD3, and PD4 having the same shape are arranged at a pitch p3 / 4. Then, by electrically connecting them every four, signals with four phases different in phase by p3 / 4 are generated.

  The pitch of each phase group is all p3, and the effective width W3 in the scale moving direction is equal to the length of the PD array 41. The PD array 41 is formed by integrating the photodetector and the third grating, and the function of the triple slit described in the “conventional technology” is established as it is. In calculating z2, the optical distance from the surface of the PD array 41 to the second grating 71 of the scale 7 may be calculated instead of the third grating.

Note that various modifications and replacements are possible for each component of the embodiment of the present invention.
An example of the bare LED 2 is shown as the light source. However, as long as a diffraction image can be formed, such as a surface emitting laser, a bare chip type, a mold type, or a can-sealed type may be used. Glass is generally used as the material of the light transmissive member 3 having the first grating 31, but a resin such as PET or polyimide may be used. In the third grating 51, an example in which the light receiving unit is individually used for four grating groups having different detection phases is shown, but a type using two groups or one group of grating groups may be used.

  As for the combination of the bare LED on the light source side and the first grating 31, the point light source 21 as shown in FIG. 6, the linear light source, or the first grating 31 with one slit as shown in FIG. 7 may be used. good. In this case, the point light source 21, the linear light source, or the width W1 of one slit 31 needs to be not more than a predetermined value. In this example, it is desirable that at least W1 ≦ p3 in order to make it possible to apply the formula used in the explanation of the principle.

  When the emission width of the emission part is reduced in the scale moving direction, the optical distance from the point light source 21 or the linear light source or the position of the emission part of one slit 31 to the lattice plane of the scale 7 is z1. .

  In the case of using a PD array, the example of FIG. 5 shows an example in which four phase groups having different detection phases are inserted in one place, but a configuration using two or four PD array groups may be used.

  The configuration of this embodiment mobile phone detects the relative movement amount, but it is also possible to add a reference position detection member, particularly a light source, a detection unit, an optical pattern, etc., on the detection head and the scale. is there.

  Furthermore, by arranging a plurality of the first to third lattices or a part thereof in this embodiment, the displacement in the same direction is detected by a plurality of detection systems, or the displacements in a plurality of orthogonal directions are simultaneously performed. It is also possible to adopt a configuration for detection. In the case of using a PD array, the first and second gratings and PD arrays in this example and the PD array, or a configuration for achieving a similar purpose by arranging a plurality of parts thereof can be used. .

Next, the operation of this embodiment will be described.
Light is emitted from the bare LED 2 that is a light source. This light passes through the first grating 31 formed on the light transmitting substrate 3 and is irradiated to the second diffraction grating 71 on the scale 7. Further, the light is reflected and diffracted by the second grating 71, and a diffraction image of the second grating is formed on the third grating 51 formed on the light transmission substrate 5. Similarly, when a PD array is used for the photodetector 4, a diffraction image of the second grating 71 is formed on the PD array 41 in the same manner.

  The diffraction image is an image obtained by magnifying the second grating 71 twice, and the light of the diffraction image that has passed through the third grating 51 is detected by the light receiving unit of the photodetector 4. When the scale 7 moves relative to the detection head in the x direction, the diffraction image moves on the third grating 51 in the x direction. For this reason, a periodic pseudo sine wave signal is obtained from the photodetector 4.

  The same applies when a point light source, a linear light source, or a first slit 31 with one slit is used as the light source. Four signals having a phase difference of 90 ° are obtained from the photodetector 4. If necessary, a difference is taken for each of two sets of signals having a phase difference of 180 °, and two signals having a phase difference of 90 ° can be obtained.

  When there is no step adjustment on the surface of the light transmissive resin 6, Δzd changes to change the optical distance z 1 from the first grating 31 to the second grating 71 and the distance from the second grating 71 to the third grating 51. The optical distance z2 is slightly deviated from the optimum value. As a result, the magnification of the self-image of the second grating 71 formed on the third grating 51 changes, and the intensity of the interference pattern detected by the photodetector changes.

  If the photodetector 4 is a PD array, the optical distance z1 from the first grating 31 to the second grating 71 and the optical distance z2 from the second grating 71 to the PD array are changed by changing Δzd. Slightly deviates from the optimum value. As a result, the magnification of the self-image of the second grating 71 formed on the PD array changes, and the intensity of the interference pattern detected by the photodetector changes.

Next, the operation of the signal adjustment unit will be described.
On the other hand, the magnification is substantially matched to the design value by adjusting the level difference on the surface of the light transmitting resin 6. As a result, an almost optimal signal can be detected and a good S / N ratio can be obtained.
Moreover, an effect is demonstrated. For encoders in which the signal detection level is lowered and a desired signal or SN ratio cannot be obtained without providing a step, almost optimum signal detection can be performed by adjusting the enlargement magnification by the step, and a good SN ratio can be obtained. This can reduce the incidence of defective products.

  In addition, it is possible to cancel the enlargement magnification shift caused by Δzd, so that the degree of freedom in design is improved, and a mounting machine with a loose tolerance of the member used, and therefore usually a low cost or a mounting machine with a loose mounting tolerance is adopted. It is also possible.

  In addition, it is possible to adjust the signal in a unit of quantity by providing a step so as to cancel the deviation of the enlargement magnification due to the average Δzd value caused by the variation of lots of parts used in mass production and the change of parts. Become.

In addition to the above-described effects, the following effects are obtained depending on the members used and the configuration.
Normally, the thickness tolerance of the bare chip component is about ± 20 μm at most, and the configuration is such that the mounting tolerance of Δzd can be kept small. Therefore, W1 and W3 can be increased, the amplitude of the encoder signal can be increased, and the SN ratio is improved.

  Further, since the first grating 31 and the third grating 51 are arranged below the light transmitting substrate 3 and the light transmitting substrate 5, the thickness tolerance of the light transmitting substrate 3 and the light transmitting substrate 5 is included in the mounting tolerance of Δzd. Does not affect Δzd. For this reason, the mounting tolerance of Δzd can be further reduced.

  The light transmitting substrate 3 is directly attached to the light emitting portion on the upper surface of the bare LED 2 that is a light source, and further, wiring for energization is performed on a portion where the light transmitting substrate 3 on the upper surface of the bare LED is not attached. The function and the function of applying current to the bare LED are realized in a compact form.

  By using bare chip components for the light source and the light receiving part, the mounting area and thickness can be suppressed. Further, by using the bare LED, the length of the light emitting part of the light emitting part can be reduced to about several tens of μm to 200 μm, and the area of the light transmitting substrate 3 disposed thereon can also be reduced. For this reason, it is advantageous in reducing the size and thickness.

The required number of the 1st grating | lattices 31 can be suppressed to the minimum by sticking the 1st grating | lattice 31 to the small light emission part of the bare LED2. As a result, the length of W1 can be reduced, and the mounting tolerance of Δzd can be increased, or even if the mounting tolerance of Δzd is the same, the reduction of the encoder signal amplitude can be reduced.
Further, improvement in reliability can be expected in terms of cracks and disconnection of wire wiring in resin sealing due to downsizing and thinning.
Furthermore, sealing with resin makes it less susceptible to atmospheric pressure and enables use under vacuum or high pressure.

  In this embodiment, bare LEDs are used, but molded LEDs can also be used. In this case, it is not necessary to perform wire wiring on the upper surface of the LED, and it becomes easy to mount the light transmission substrate 3 having the first lattice. Furthermore, since the mold LED is sealed, the versatility and reliability are higher than those of the bare LED. Therefore, there is an advantage that the encoder can be easily mounted.

(Modification 1 of the first embodiment)
Next, Modification 1 of the first embodiment of the present invention will be described.

(Constitution)
The shape of the light transmitting resin 6 in FIG. 4 is changed to provide an inclination as shown in FIG. It should be noted that the same action and effect can be expected even in a configuration in which the upper surface of FIG.

  The magnitude (height) of the inclination and the light source so that the magnification that is expressed by (z1 + z2) / z1 in Expression 2 is shifted from the design value by Δzd in Expression 4 to match the original design value. Which side is higher than the light receiving side is required.

  This slope shape is applied when the absolute value of Δzd is large, and if there is no step shape, the signal detection level is lowered and a desired signal or S / N ratio cannot be obtained or there is a possibility of such a situation. .

  This inclination can be realized by processing such as molding by deforming the mold shape by cutting / pressing the surface shape of the flat light transmitting resin 6 shown in FIG. 8 or FIG. A processing method other than those shown here, a means for improving workability by heating, etc. may be used.

(Function)
When the enlargement magnification is substantially matched with the design value, almost optimal signal detection can be performed, and a good SN ratio can be obtained.

(effect)
This modification has the same effects as those of the first embodiment described above.

(Modification 2 of the first embodiment)
Next, modification 2 of the first embodiment of the present invention will be described.
Instead of the step on the surface of the light transmitting resin 6 on the scale side in FIG. 4, a new light transmitting member 61 is provided as shown in FIG. 11 or FIG. It should be noted that the same action and effect can be expected even if the surface on the scale side of the light transmitting resin 6 in FIG. 4 is replaced with a shape having an inclination as shown in the light transmitting resin 6 in FIG.

  The thickness of the light transmitting member 61 and the light source side are adjusted so that the amount of enlargement magnification represented by (z1 + z2) / z1 in Equation 2 is shifted from the design value by Δzd in Equation 4 to the original design value. Which side of the light receiving side is provided is determined.

  The light transmitting member 61 is applied when the absolute value of Δzd is large, and if there is no stepped shape, the signal detection level is lowered and a desired signal or S / N ratio cannot be obtained or there is a possibility of that. To do.

  The light transmissive member 61 can be realized by mounting a thin film on the surface of a flat light transmissive resin 6 as shown in FIGS. 8 and 9 or by photolithography. Note that a mounting / forming method other than those shown here may be used.

  Further, in this example, one light transmitting member 61 is provided on either the light source side or the light receiving side. However, it is possible to adjust a desired enlargement magnification by using a plurality of members or simultaneously providing both members. As long as you do, the configuration does not matter.

(Function)
By providing the light transmitting member 61, at least one of z1 and z2 is adjusted. When the enlargement magnification is substantially matched with the design value, almost optimal signal detection can be performed, and a good SN ratio can be obtained.

(effect)
This modification has the same effect as the first embodiment.
Furthermore, since it is realizable by arrangement | positioning of the light transmissive member 61 which is another member on the surface, it also has the following effects.
If a thin film is applied, the operation is relatively easy. Further, it is relatively easy to remove or replace the member for readjustment or the like.
In addition, when forming a thin film pattern by a lithography technique, there is a possibility that a large number of encoders can be arranged and adjusted simultaneously.

(Second Embodiment)
Next, an optical encoder according to a second embodiment of the present invention will be described.
Instead of the steps on the surface of the light transmitting resin 6 in FIGS. 3 and 4, a light transmitting member 5 is provided inside the light transmitting resin 6 as shown in FIG. 13. Even if the light transmitting member 5 is provided inside the light transmitting resin 6 as shown in FIG. 13 in place of the step on the surface of the light transmitting resin 6 in FIGS.

  The scale direction of the light-transmitting member 5 (z in the figure) is set so that the amount of enlargement magnification represented by (z1 + z2) / z1 in Equation 2 is shifted from the design value by Δzd in Equation 4 to the original design value. Direction) thickness, refractive index, and arrangement of light source side or light receiving side.

The light transmitting member 5 is applied when the absolute value of Δzd is large, and if there is no stepped shape, the signal detection level is lowered and a desired signal or S / N ratio cannot be obtained. To do.
Moreover, although the light transmissive member is used in this example, it may be a space in which a gas including the atmosphere or a vacuum is arranged.

(Function)
By replacing a part of the light transmissive resin 6 with the light transmissive member 5 having a different refractive index, at least one of z1 and z2 is adjusted.
When the enlargement magnification is substantially matched with the design value, almost optimal signal detection can be performed, and a good SN ratio can be obtained.

(effect)
The present embodiment has the same effect as the first embodiment.

(Modification 1 of 2nd Embodiment)
Modification 1 of the second embodiment of the present invention will be described.
As shown in FIG. 14, the first grating 31 of the light transmitting member 3 in FIGS. 3 and 4 is disposed on the scale side. Even if the first grating 31 of the light transmitting member 3 in FIGS. 1 and 2 is disposed on the scale side, the same operation and effect can be expected.

  In addition, the thickness of the light transmitting member 3 in the scale direction (z direction in the drawing) is calculated by subtracting the amount of enlargement magnification represented by (z1 + z2) / z1 in Expression 2 from the design value by Δzd in Expression 4. It is decided to match the design value.

(Function)
By changing the thickness of the light transmitting member 3, z1 is adjusted.
When the enlargement magnification is substantially matched with the design value, almost optimal signal detection can be performed, and a good SN ratio can be obtained.

(effect)
This modification has the same effect as the first embodiment.

  Furthermore, according to this structure, the 1st grating | lattice 31 is the upper side which is a scale side. For this reason, when the thickness from the 1st grating | lattice 31 to the resin surface is constant, since the resin thickness is thick compared with the case where the 1st grating | lattice 31 is a lower side, it is based on the difference in the linear expansion coefficient of the light transmissive board | substrate 3 and resin. When the resin is hardened by lowering the temperature from a high temperature to a low temperature during production, the flatness of the surface is improved, and as a result, the optical characteristics are improved.

(Modification 2 of the second embodiment)
Next, Modification 2 of the second embodiment of the present invention will be described.
As shown in FIG. 15, the light transmitting member 3 in FIGS. 2 and 3 is replaced with a light shielding member 3 provided with a first grating. Even if the light transmitting member 3 in FIGS. 1 and 2 is replaced with the light shielding member 3 provided with the first grating, the same operation and effect can be expected.

  The thickness of the light-shielding member 3 in the scale direction (z direction in the figure) is the original design value obtained by changing the enlargement magnification represented by (z1 + z2) / z1 in Expression 2 from the design value by Δzd in Expression 4. It is decided to adjust to.

At least the surface of the light shielding member 3 has conductivity, and plays a role of electrically connecting the electrode of the bare LED light source and the gold wire 8.
In this modification, the light shielding member in which the first grating is formed is used. However, it is also possible to use a light transmitting member in which the first grating is formed with a pattern that does not allow light to pass through to the inside.

(Function)
By changing the thickness of the light shielding member 3, z1 is adjusted.
When the enlargement magnification is substantially matched with the design value, almost optimal signal detection can be performed, and a good SN ratio can be obtained.

(effect)
This modification has the same effect as the first embodiment.
Further, since the light shielding member 3 becomes a part of the electrical wiring, it is not necessary to provide a pad for bonding the gold wire 8 on the light source 2 in addition to the light shielding member 3. Therefore, the mounting becomes easy and the size can be reduced.

(Modification 3 of the second embodiment)
Next, Modification 3 of the second embodiment of the present invention will be described.
As shown in FIG. 16, the light transmission member 5 in FIGS. 3 and 4 is arranged so that the third grating 51 is located on the scale side.
The thickness of the light transmissive member 5 in the scale direction (z direction in the figure) is the original design value obtained by changing the enlargement magnification represented by (z1 + z2) / z1 in Expression 2 from the design value by Δzd in Expression 4. It is decided to adjust to.

(Function)
By changing the thickness of the light transmission member 5, z2 is adjusted.
When the enlargement magnification is substantially matched with the design value, almost optimal signal detection can be performed, and a good SN ratio can be obtained.

(effect)
This modification has the same effect as the first embodiment.
Further, according to this configuration, since the third lattice is on the upper side which is the scale side, the resin thickness is larger when the thickness from the third lattice to the resin surface is constant than when the third lattice is on the lower side. Becomes thicker. For this reason, due to the difference in linear expansion coefficient between the light transmitting substrate 5 and the resin, the flatness of the surface is improved when the resin is hardened by lowering the temperature from a high temperature to a low temperature during production, and as a result, the optical characteristics are improved.

(Modification 4 of the second embodiment)
Next, Modification 4 of the second embodiment of the present invention will be described.
As shown in FIG. 17, the light transmitting member 5 in FIGS. 3 and 4 is replaced with a light shielding member 5 provided with a third grating.
The thickness of the light-shielding member 5 in the scale direction (z direction in the figure) is the original design value obtained by changing the enlargement magnification represented by (z1 + z2) / z1 in Expression 2 from the design value by Δzd in Expression 4. It is decided to fit in.
In this modification, the light shielding member in which the third grating is formed is used. However, it is also possible to use a light transmitting member in which the first grating is formed with a pattern that does not allow light to pass through to the inside.

(Function)
By changing the thickness of the light shielding member 5, z2 is adjusted.
When the enlargement magnification is substantially matched with the design value, almost optimal signal detection can be performed, and a good SN ratio can be obtained.

(effect)
This modification has the same effect as the first embodiment.

(Third embodiment)
An optical encoder according to the third embodiment of the present invention will be described.
11, a spacer 22 is disposed between the light source 2 and the substrate 1 in FIGS. 3 and 4, and in FIG. 19, a spacer 42 is disposed between the photodetector 4 and the substrate 1 in FIGS. 1 and 2. Yes.

The thickness of the spacer 42 in the scale direction (z direction in the figure) is adjusted so that the enlargement magnification represented by (z1 + z2) / z1 in Expression 2 deviates from the design value by Δzd in Expression 4 to the original design value. To be included.
In the present embodiment, the spacer 42 is disposed on one of the light source side and the light receiving side, but may be disposed on both. Further, any shape may be used for the shape of the grating on the light source side or the light detection side. That is, there are no particular restrictions on the point light source, the first grating, the PD array, and the third grating.

(Function)
By changing the thickness of the spacer 42, at least one of z1 and z2 is adjusted. When the enlargement magnification is substantially matched with the design value, almost optimal signal detection can be performed, and a good SN ratio can be obtained.

(effect)
The present embodiment has the same effect as the first embodiment.
By using the spacers 42 in this way, the thicknesses of the bare LED 2, the light transmission substrate 3, and the photodetector 4 can be adjusted in the height adjustment of the first grating and the third grating (PD array). Specifically, it is effective when the heights of the first grating and the third grating (PD array) cannot be matched without a spacer because the thickness of each member is determined in advance.

  Further, there is an advantage that adjustment is possible by changing the thickness of the spacer when the thickness of the member is extremely varied or when the member is replaced with another material. Further, by using a spacer 42 having a small thickness tolerance, the influence on Δzd which is a difference between z1 and z2 can be suppressed as much as possible.

  As described above, the present invention is useful for an optical encoder that is small and suitable for mass production.

2 Bear LED
Reference Signs List 4 Photodetector 5 Light transmissive substrate 6 Light transmissive resin 7 Scale 31 First grating 71 Second grating 51 Third grating

Claims (12)

A detection head attached to either one of the fixed body and the moving body that move relative to each other;
A scale provided with a grating having an optical pattern with a predetermined pitch in the direction of relative movement, attached to the other side facing the detection head,
The detection head is
A light emitting unit that emits divergent light with a limited emission width in the direction of scale movement of the emitted light, and irradiates the scale with predetermined light; and a light detection unit that includes a grating functional surface and a light receiving unit,
An image of an image formed on the grating functional surface of the light detection unit by irradiating the scale from the emission surface having a limited emission width of the light emitting unit and reflecting the diffracted light by the grating provided on the scale. In the optical encoder in which the light detection unit arranged to detect movement is provided, and a periodic detection signal is output from the light detection unit according to the relative movement amount of the scale,
An optical distance z1 from a position that limits the emission width of the diverging light on the light emitting unit side to the grating of the scale;
A signal for reducing deterioration in the amplitude level of the detection signal by increasing or decreasing at least one of the optical distance z2 from the grating of the scale on the light receiving unit side to the grating functional surface of the light detection unit An optical encoder comprising a deterioration reducing means. The signal degradation reducing means is a member or space,
The optical encoder according to claim 1, wherein the optical distance is adjusted by changing either the thickness of the member or the space on the optical path of the space, or the interval and the refractive index. The signal degradation reducing means is a member or space,
2. The optical distance is adjusted by moving at least one position of the emission surface on the light emitting unit side and the grating functional surface of the light detection unit by the signal deterioration reducing unit. The optical encoder described in 1.   The optical encoder according to claim 1, further comprising a protective member that integrally covers the light emitting unit and the light detection unit.   The optical encoder according to claim 4, wherein the protective member is a light transmissive resin.   The optical encoder according to claim 4, wherein the signal deterioration reducing unit is formed by shaping a surface shape of the protective member on a scale side into a predetermined shape.   5. The optical encoder according to claim 4, wherein the signal deterioration reducing means is a light transmitting member that is attached to a scale-side surface of the protective member.   5. The optical encoder according to claim 4, wherein the signal deterioration reducing unit is arranged on an optical path inside the head with respect to a surface of the protection member.   5. The optical encoder according to claim 4, wherein the signal deterioration reducing unit is disposed outside the optical path inside the head with respect to the surface of the protective member.   2. The optical encoder according to claim 1, wherein the signal degradation reducing unit is a member or a space arranged to have at least one optical refractive index boundary surface on an optical path.   The optical encoder according to claim 10, wherein the signal deterioration reducing means is a member mounted on (to be in contact with) the light emitting unit or the scale side surface of the photodetector. The signal deterioration reducing means includes an optical distance from the light emitting unit side emission surface to the scale grating, and an optical distance from the light receiving unit side scale grating to the grating functional surface of the light detection unit; The optical encoder according to claim 1, wherein only one of the optical distances is adjusted.

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