JP5452533B2 - Optical encoder - Google Patents

Description

  The present invention relates to an optical encoder.

2. Description of the Related Art Conventionally, a scale having a grid-like scale, a light source that emits light to the scale, and a head that has a light receiving element that receives light reflected by the scale, and based on light received by the light receiving element An optical encoder that measures the position of the head relative to the scale is known (see, for example, Patent Documents 1 and 2).
The optical encoder described in Patent Document 1 includes a scale plate (scale), a reflective optical reader (head) having a light emitting diode (light source), an objective lens, and a light receiving unit (light receiving element). The reflective optical reader includes a half mirror disposed between the light emitting diode and the objective lens, and an optical path of light emitted from the light emitting diode and directed to the scale plate through the objective lens, and the scale plate Is separated from the optical path of the light that is reflected by the lens and travels toward the light receiving portion via the objective lens.

However, in the optical encoder described in Patent Document 1, the light receiving unit receives light via the half mirror, so that there is a problem that a sufficient amount of light cannot be secured. Further, when the light amount of light emitted from the light emitting diode is increased in order to ensure a sufficient amount of light, there is a problem that the power consumption of the light emitting diode is increased and consequently the life of the light emitting diode is shortened.
On the other hand, the photoelectric encoder (optical encoder) described in Patent Document 2 includes a scale, a light source, a lens, and a light receiving element. Further, the photoelectric encoder is arranged so that the scale, the lens, and the light receiving element are in a Scheinproof relationship, so that the light path emitted from the light source and directed to the scale and reflected by the scale The light path of the light traveling toward the light receiving element is separated, and a sufficient amount of light is secured in the light receiving element.

JP 2003-307440 A JP 2006-284564 A

However, the photoelectric encoder described in Patent Document 2 has a problem that the scale and the light receiving element cannot be arranged in parallel, which increases the size of the photoelectric encoder.
In the photoelectric encoder described in the fifth embodiment of Patent Document 2, the scale and the light receiving element are arranged in parallel by arranging four lenses between the scale and the light receiving element. However, this photoelectric encoder has a problem that the size of the photoelectric encoder increases because four lenses are disposed between the scale and the light receiving element.

  An object of the present invention is to provide an optical encoder that can secure a sufficient amount of light in a light receiving element and can be miniaturized.

  An optical encoder according to the present invention includes a scale having a grid-shaped scale, a light source that emits light to the scale, and a light receiving element that is disposed in parallel with the scale and receives light reflected by the scale. And an optical encoder that measures the position of the head relative to the scale based on light received by the light receiving element, the head transmitting light emitted from the light source to the scale. A scale-side lens that transmits light reflected by the scale to the light-receiving element, and the light source is disposed between the scale-side lens and the light-receiving element, and the light source And the scale-side lens is the focal length of the scale-side lens, and the optical axis of the light source is the front in the reading direction of the scale. Coincides with the optical axis of the scale-side lens in the orthogonal direction orthogonal to the reading direction of the scale, characterized in that spaced apart by a predetermined distance from the optical axis of the scale-side lens.

  According to such a configuration, the optical axis of the light source is separated from the optical axis of the scale side lens by a predetermined distance in an orthogonal direction (hereinafter referred to as an orthogonal direction of the scale) orthogonal to the scale reading direction. Of the light emitted from the light source, light on the light source side in the direction perpendicular to the scale is transmitted to the scale via the scale side lens on the light source side in the direction perpendicular to the scale. Then, this light is reflected by the scale, and is received by the light receiving element via the scale side lens opposite to the light source in the direction perpendicular to the scale. Therefore, according to the present invention, the optical path of light emitted from the light source and directed to the scale and the optical path of light reflected by the scale and directed to the light receiving element via the scale side lens are separated without using a half mirror. Therefore, a sufficient amount of light can be secured in the light receiving element.

The scale and the light receiving element are arranged in parallel, and one scale side lens is arranged between the scale and the light receiving element. And since a light source is arrange | positioned between a scale side lens and a light receiving element, an optical encoder can be reduced in size.
Furthermore, since the distance between the light source and the scale side lens is the focal length of the scale side lens, the optical encoder should constitute an object (scale) side telecentric optical system in the scale reading direction. And the depth of focus can be increased. Therefore, the allowable amount of the scale and the head interval can be increased.

  In the present invention, the predetermined distance is preferably ½ or more of the width of the light source in an orthogonal direction orthogonal to the reading direction of the scale.

Here, when the predetermined distance between the optical axis of the light source in the orthogonal direction of the scale and the optical axis of the scale-side lens is less than ½ of the width of the light source in the orthogonal direction of the scale, in the orthogonal direction of the scale, A part of the light source protrudes from the optical axis of the scale side lens and is not received by the light receiving element, so that the utilization efficiency of the light emitted from the light source is lowered.
On the other hand, according to the present invention, the predetermined distance between the optical axis of the light source in the direction orthogonal to the scale and the optical axis of the scale side lens is 1 of the width (numerical aperture) of the light source in the direction orthogonal to the scale. Since it is / 2 or more, the utilization efficiency of the light emitted from the light source can be improved.

  In the present invention, the head includes an aperture that is reflected by the scale and allows light passing through the scale side lens to pass therethrough, and a distance between the aperture and the scale side lens is equal to the distance of the scale side lens. The optical axis of the aperture and the optical axis of the light source are in a line-symmetric relationship with respect to the optical axis of the scale-side lens in a plane that is a focal length and is orthogonal to the reading direction of the scale. Is preferred.

Here, when the optical encoder of the present invention is configured only by designing the width and position of the light source, the performance of the optical system of the optical encoder may change due to the influence of the positional deviation of the light source. There is.
According to the present invention, the optical encoder includes an aperture that is reflected by the scale and allows light to pass through the lens on the scale side. Therefore, the width and position of the light source are designed by designing the width and position of the aperture. An optical system similar to the case can be configured. In addition, since the design and positioning of the aperture is easier than the design and positioning of the light source, it is possible to suppress a change in the performance of the optical system of the optical encoder.

In the present invention, the head includes a light receiving element side lens disposed between the aperture and the light receiving element, and a distance between the aperture and the light receiving element side lens is the light receiving element side. The focal length of the lens is preferably set, and the optical axis of the light receiving element side lens preferably coincides with the optical axis of the scale side lens.
According to such a configuration, the optical encoder can configure a double-sided telecentric optical system in the scale reading direction, and can increase the depth of focus. Therefore, the allowable amount of the interval between the light receiving element and the light receiving element side lens can be increased.

  In the present invention, the head includes a light receiving element side lens disposed between the aperture and the light receiving element, and a distance between the aperture and the light receiving element side lens is the light receiving element side. The optical axis of the light receiving element side lens coincides with the optical axis of the scale side lens in the scale reading direction, and the scale side in the orthogonal direction perpendicular to the scale reading direction. It is preferable that the lens is separated from the optical axis of the lens by a distance twice the predetermined distance.

According to such a configuration, the optical encoder can configure a double-sided telecentric optical system in the scale reading direction. Therefore, the tolerance of the interval between the light receiving element and the light receiving element side lens can be increased.
Further, in the orthogonal direction of the scale, the optical axes of the scale side lens and the light receiving element side lens are separated from each other by a predetermined distance from the optical axis of the aperture, so that the light passing through the aperture is separated from the scale side lens, And the position which has the same shape of the light receiving element side lens is transmitted. Therefore, the optical encoder can reduce the influence of lens aberration and can perform appropriate measurement.

  In the present invention, the head includes the two light sources, the two scale-side lenses, and the two apertures, and each light source and each scale side in a plane orthogonal to the scale reading direction. It is preferable that the optical axes of the lens and each aperture have a line-symmetric relationship with respect to the optical axis of the light receiving element side lens.

  According to such a configuration, the light reflected by the two scales can be received by one light receiving element. Therefore, for example, an optical encoder is used so that two scales, a scale for detecting the movement amount of the scale and the head, and a scale for detecting the origin of the scale and the head are received by one light receiving element. The number of components can be reduced as compared with the case where the optical encoder is configured to receive light with two light receiving elements.

In the present invention, the light source includes a light emitter that emits light, and a diffusion plate that is disposed downstream of the light path of the light emitted from the light emitter and diffuses the light emitted from the light emitter. preferable.
According to such a configuration, since the width of the light source can be replaced with the width of the diffusion plate, the design of the optical encoder can be facilitated.

In the present invention, the light source includes a light emitter that emits light, and a light emitter lens that is disposed downstream of the light path of the light emitted from the light emitter, the scale side lens, and the light emitter It is preferable to configure Kohler illumination with the lens.
According to such a configuration, unevenness of light emitted from the light source and directed to the scale via the scale side lens can be reduced, and appropriate measurement can be performed.

The schematic diagram which shows the optical encoder which concerns on 1st Embodiment of this invention. The schematic diagram which looked at the optical encoder in the said embodiment along the orthogonal direction of the scale. The schematic diagram which looked at the optical encoder which concerns on 2nd Embodiment of this invention along the reading direction of a scale. The schematic diagram which looked at the optical encoder in the said embodiment along the orthogonal direction of the scale. The schematic diagram which looked at the optical encoder which concerns on 3rd Embodiment of this invention along the reading direction of a scale. The schematic diagram which looked at the optical encoder in the said embodiment along the orthogonal direction of the scale. The schematic diagram which looked at the optical encoder which concerns on 4th Embodiment of this invention along the reading direction of a scale. The schematic diagram which looked at the optical encoder which concerns on 5th Embodiment of this invention along the reading direction of a scale. The schematic diagram which shows the light source of the optical encoder which concerns on 6th Embodiment of this invention. The schematic diagram which shows the light source of the optical encoder which concerns on 7th Embodiment of this invention.

[First Embodiment]
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing an optical encoder 1 according to the first embodiment of the present invention. In FIG. 1, the axis perpendicular to the paper surface is the X axis, the horizontal axis is the Y axis, and the vertical axis is the Z axis.
As shown in FIG. 1, the optical encoder 1 includes a scale 2 having a grid-like scale 21 that can be read along the X-axis direction, a light source 31 that emits light to the scale 2, and light emitted from the light source 31. And a head 3 having a light receiving element 33 that receives light reflected by the scale 2 through the scale side lens 32, and a scale side lens 32 that transmits the light to the scale 2. Based on the light received by the light receiving element 33, the position of the head 3 with respect to the scale 2 is measured. That is, the scale side lens 32 transmits light reflected by the scale 2 to the light receiving element 33.
The scale 2 is formed in a rectangular plate shape in which the X-axis direction is the longitudinal direction and the Y-axis direction is the short direction. FIG. 1 is a view of the optical encoder 1 as viewed along the reading direction of the scale 21.

FIG. 2 is a schematic view of the optical encoder 1 viewed along the orthogonal direction of the scale 21. The orthogonal direction of the scale 21 is a direction (Y-axis direction) orthogonal to the reading direction of the scale 21.
As shown in FIGS. 1 and 2, the light source 31 is disposed between the scale side lens 32 and the light receiving element 33, and the distance between the light source 31 and the scale side lens 32 is the scale side lens 32. The focal length fs.
The optical axis Lsrc of the light source 31 coincides with the optical axis Ls of the scale side lens 32 in the reading direction of the scale 21 (see FIG. 2), and in the orthogonal direction of the scale 21, a predetermined distance from the optical axis Ls of the scale side lens 32. They are separated by D (see FIG. 1). Here, the predetermined distance D is set to ½ or more of the width Wsrcy (numerical aperture) of the light source 31 in the orthogonal direction of the scale 21.

The optical axis Lsrc of the light source 31 is separated from the optical axis Ls of the scale-side lens 32 by a predetermined distance D in the direction orthogonal to the scale 21, so that the light emitted from the light source 31 is in the direction orthogonal to the scale 21. As shown in FIG. 1, the light on the light source 31 side is transmitted to the scale 2 via the scale side lens 32 on the light source 31 side in the direction orthogonal to the scale 21. Then, this light is reflected by the scale 2 and is received by the light receiving element 33 through the scale side lens 32 opposite to the light source 31 in the direction orthogonal to the scale 21.
1 and 2, the optical path of light received by the light receiving element 33 is indicated by a solid line, and the optical paths of other light are omitted. The same applies to the following drawings.

Further, since the distance between the light source 31 and the scale side lens 32 is the focal length fs of the scale side lens 32, the optical encoder 1 in the reading direction of the scale 21 as shown in FIG. The object (scale 2) side telecentric optical system can be constructed, and the depth of focus can be increased.
Specifically, the width of the light source 31 in the reading direction of the scale 21 is Wsrcx, the distance from the scale 21 to the scale side lens 32 is Ds (not shown), and the distance from the scale side lens 32 to the light receiving element 33. Is Dp (not shown), the numerical aperture NA of the scale side lens 32 can be expressed by the following equation (1).

  Further, when the wavelength of light emitted from the light source 31 is λ, the depth of focus DOF of the optical encoder 1 can be expressed by the following equation (2).

  Therefore, the depth of focus DOF can be increased as the width Wsrcx of the light source 31 is decreased.

According to this embodiment, there are the following effects.
(1) The optical encoder 1 is a half-mirror between an optical path of light emitted from the light source 31 and directed to the scale 2 and an optical path of light reflected by the scale 2 and directed to the light receiving element 33 via the scale side lens 32. Therefore, the light receiving element 33 can ensure a sufficient amount of light.
(2) The scale 2 and the light receiving element 33 are disposed in parallel, and one scale side lens 32 is disposed between the scale 2 and the light receiving element 33. And since the light source 31 is arrange | positioned between the scale side lens 32 and the light receiving element 33, the optical encoder 1 can be reduced in size.

(3) The optical encoder 1 can constitute an object (scale 2) side telecentric optical system in the reading direction of the scale 21 and can increase the depth of focus. Therefore, the allowable amount of the interval between the scale 2 and the head 3 can be increased.
(4) The predetermined distance D between the optical axis Lsrc of the light source 31 in the direction orthogonal to the scale 21 and the optical axis Ls of the scale side lens 32 is equal to or greater than ½ of the width Wsrcy of the light source 31 in the direction orthogonal to the scale 21. Therefore, the utilization efficiency of the light emitted from the light source 31 can be improved.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. In the following description, parts that have already been described are assigned the same reference numerals and description thereof is omitted.
FIG. 3 is a schematic view of the optical encoder 1 </ b> A according to the second embodiment of the present invention viewed along the reading direction of the scale 21. FIG. 4 is a schematic view of the optical encoder 1 </ b> A viewed along the orthogonal direction of the scale 21.
In the first embodiment, the optical encoder 1 includes the head 3 having the light source 31, the scale side lens 32, and the light receiving element 33. On the other hand, in this embodiment, the optical encoder 1A includes a head 3A having an aperture 34 in addition to the light source 31, the scale side lens 32, and the light receiving element 33, as shown in FIGS. It is different in point.

The aperture 34 is reflected by the scale 2 and allows light passing through the scale side lens 32 to pass through. The distance between the aperture 34 and the scale side lens 32 is the focal length fs of the scale side lens 32. Has been.
Further, in a plane (paper surface) orthogonal to the reading direction of the scale 21, the optical axis La of the aperture 34 and the optical axis Lsrc of the light source 31 are axisymmetric with respect to the optical axis Ls of the scale side lens 32. It is. That is, the optical axis La of the aperture 34 coincides with the optical axis Ls of the scale side lens 32 in the reading direction of the scale 21 (see FIG. 4), and from the optical axis Ls of the scale side lens 32 in the orthogonal direction of the scale 21. They are separated by a predetermined distance D (see FIG. 3).

  Here, the width Way of the aperture 34 in the orthogonal direction of the scale 21 (see FIG. 3) is expressed by the following equation (3) so as to allow the positioning error of the light source 31 in the orthogonal direction of the scale 21 by δ. Set.

  According to such setting, even if an error occurs in the positioning of the light source 31 in the orthogonal direction of the scale 21, the light emitted from the light source 31 is limited by the aperture 34 if the error is equal to or less than δ. Can do. Therefore, it is possible to suppress a change in the performance of the optical system of the optical encoder 1A due to the influence of the positional deviation of the light source 31.

In addition, since the distance between the aperture 34 and the scale side lens 32 is the focal length fs of the scale side lens 32, the optical encoder 1A in the reading direction of the scale 21 as shown in FIG. The object (scale 2) side telecentric optical system can be constructed, and the depth of focus can be increased.
Specifically, the width of the aperture 34 in the reading direction of the scale 21 is Wax, the distance from the scale 21 of the scale 2 to the scale side lens 32 is Ds (not shown), and the distance from the scale side lens 32 to the light receiving element 33. Is Dp (not shown), the numerical aperture NA of the scale side lens 32 can be expressed by the following formula (4).

  Further, when the wavelength of light emitted from the light source 31 is λ, the focal depth DOF of the optical encoder 1A can be expressed by the following equation (5).

  Therefore, the depth of focus DOF can be increased as the width Wax of the aperture 34 is reduced.

In this embodiment as well, the same operations and effects as those of the first embodiment can be achieved, and the following operations and effects can be achieved.
(5) Since the optical encoder 1A includes the aperture 34 that is reflected by the scale 2 and passes the light through the scale side lens 32, the width and position of the light source 31 can be designed by designing the width and position of the aperture 34. An optical system similar to the case of designing can be configured.
(6) Since the design and positioning of the aperture 34 are easier than the design and positioning of the light source 31, it is possible to suppress a change in the performance of the optical system of the optical encoder 1A.

[Third Embodiment]
FIG. 5 is a schematic view of the optical encoder 1 </ b> B according to the third embodiment of the present invention viewed along the reading direction of the scale 21. FIG. 6 is a schematic view of the optical encoder 1 </ b> B viewed along the orthogonal direction of the scale 21.
In the second embodiment, the optical encoder 1A includes the head 3A having the light source 31, the scale side lens 32, the light receiving element 33, and the aperture 34. On the other hand, in this embodiment, the optical encoder 1B includes a light receiving element side lens 35 in addition to the light source 31, the scale side lens 32, the light receiving element 33, and the aperture 34, as shown in FIGS. The difference is that the head 3B is provided.

The light receiving element side lens 35 is disposed between the aperture 34 and the light receiving element 33, and the distance between the aperture 34 and the light receiving element side lens 35 is the focal length fp of the light receiving element side lens 35. Yes.
Further, the optical axis Lp of the light receiving element side lens 35 coincides with the optical axis Ls of the scale side lens 32.

In this embodiment as well, the same actions and effects as those of the second embodiment can be obtained, and the following actions and effects can be obtained.
(7) The optical encoder 1B can constitute a double-sided telecentric optical system in the reading direction of the scale 21, and can increase the depth of focus. Therefore, the allowable amount of the interval between the light receiving element 33 and the light receiving element side lens 35 can be increased.

[Fourth Embodiment]
FIG. 7 is a schematic view of the optical encoder 1 </ b> C according to the fourth embodiment of the present invention viewed along the reading direction of the scale 21.
In the third embodiment, the optical encoder 1B includes the head 3B, and the optical axis Lp of the light receiving element side lens 35 of the head 3B coincides with the optical axis Ls of the scale side lens 32. In contrast, in this embodiment, the optical encoder 1C includes a head 3C as shown in FIG. 7, and the optical axis Lp of the light receiving element side lens 35 of the head 3C is a scale in the reading direction of the scale 21. The optical axis Ls coincides with the optical axis Ls of the side lens 32, and the scale 21 is different in that it is separated from the optical axis Ls of the scale side lens 32 by a distance twice the predetermined distance D.

In this embodiment as well, the same operations and effects as those of the third embodiment can be achieved, and the following operations and effects can be achieved.
(8) In the orthogonal direction of the scale 21, the optical axes Ls and Lp of the scale side lens 32 and the light receiving element side lens 35 are separated from the optical axis La of the aperture 34 by a predetermined distance D on both sides. The light passing through 34 is transmitted through positions having the same shape of the scale side lens 32 and the light receiving element side lens 35. Therefore, the optical encoder 1C can reduce the influence of lens aberration, and can perform appropriate measurement.

[Fifth Embodiment]
FIG. 8 is a schematic view of the optical encoder 1D according to the fifth embodiment of the present invention viewed along the reading direction of the scale 21. FIG.
In the fourth embodiment, the optical encoder 1 </ b> C includes the head 3 </ b> C, and the head 3 </ b> C includes the light source 31, the scale side lens 32, and the aperture 34. On the other hand, in this embodiment, as shown in FIG. 8, the optical encoder 1D includes a head 3D, and the head 3D includes a light source 31, a scale side lens 32, and two apertures 34 each. Is different. The two apertures 34 are formed as one member.

In the fourth embodiment, the optical encoder 1 </ b> C includes the scale 2 having the grid-shaped scale 21. On the other hand, this embodiment is different in that a scale 2D having two grid-like scales 21 is provided.
Furthermore, in the present embodiment, the optical axes Lsrc, Ls, and La of the light sources 31, the scale side lenses 32, and the apertures 34 in the plane (paper surface) orthogonal to the reading direction of the scale 21 are the light receiving element side lenses. This is a line-symmetrical relationship with respect to 35 optical axes Lp.

In this embodiment as well, the same operations and effects as those of the fourth embodiment can be achieved, and the following operations and effects can be achieved.
(9) Since the optical encoder 1D can receive the light reflected by the two scales 21 by the single light receiving element 33, the optical encoder 1D is configured to receive the light by the two light receiving elements. In comparison, the number of parts can be reduced.

[Sixth Embodiment]
FIG. 9 is a schematic diagram showing a light source 31E of an optical encoder 1E according to a sixth embodiment of the present invention.
In each of the embodiments, the optical encoders 1 to 1D include the light source 31. On the other hand, in this embodiment, as shown in FIG. 9, the optical encoder 1E includes a light source 31E, and the light source 31E emits light 311 and light emitted from the light emitter 311. The difference is that a diffusion plate 312 is provided in the latter stage of the optical path and diffuses the light emitted from the light emitter 311.
Although not shown, the distance between the scale side lens 32 side (the lower side in FIG. 9) of the diffusion plate 312 and the scale side lens 32 is the focal length fs of the scale side lens 32. Yes.

In this embodiment as well, the same actions and effects as those in the fifth embodiment can be obtained, and the following actions and effects can be obtained.
(10) Since the width of the light source 31E can be replaced with the width of the diffusion plate 312, the design of the optical encoder 1E can be facilitated.

[Seventh Embodiment]
FIG. 10 is a schematic diagram showing a light source 31F of an optical encoder 1F according to a seventh embodiment of the present invention.
In the first to fifth embodiments, the optical encoders 1 to 1D include the light source 31. On the other hand, in this embodiment, the optical encoder 1F includes a light source 31F, as shown in FIG. 10, and the light source 31F emits light and emits light from the light emitter 311. A light emitting lens 313 disposed in the latter stage of the optical path, and the scale side lens 32 and the light emitting lens 313 constitute Koehler illumination.

In this embodiment as well, the same operations and effects as those of the fifth embodiment can be achieved, and the following operations and effects can be achieved.
(11) Unevenness of light emitted from the light source 31F and directed to the scale 2 via the scale side lens 32 can be reduced, and appropriate measurement can be performed.

[Modification of Embodiment]
Note that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope in which the object of the present invention can be achieved are included in the present invention.
For example, in each of the above-described embodiments, the predetermined distance D is set to 1/2 or more of the width Wsrcy of the light sources 31, 31 </ b> E, and 31 </ b> F in the orthogonal direction of the scale 21, but may be less than this.

  The present invention can be suitably used for an optical encoder.

DESCRIPTION OF SYMBOLS 1-1F ... Optical encoder 2, 2D ... Scale 3-3D ... Head 31, 31E, 31F ... Light source 32 ... Scale side lens 33 ... Light receiving element 34 ... Aperture 35 ... Light receiving element side lens 311 ... Light emitter 312 ... Diffuser 313 ... Lens for luminous body

Claims (8)

A scale having a grid-like scale, a light source that emits light to the scale, and a head that is arranged in parallel with the scale and receives a light that is reflected by the scale. An optical encoder that measures the position of the head relative to the scale based on light received by an element,
The head is
A scale-side lens that transmits light emitted from the light source to the scale and transmits light reflected by the scale to the light receiving element;
The light source is disposed between the scale side lens and the light receiving element, and a distance between the light source and the scale side lens is a focal length of the scale side lens.
The optical axis of the light source coincides with the optical axis of the scale side lens in the reading direction of the scale, and is separated from the optical axis of the scale side lens by a predetermined distance in the orthogonal direction perpendicular to the reading direction of the scale. An optical encoder characterized by that. The optical encoder according to claim 1,
The optical encoder is characterized in that the predetermined distance is ½ or more of the width of the light source in an orthogonal direction orthogonal to a reading direction of the scale. The optical encoder according to claim 2, wherein
The head is
An aperture that is reflected by the scale and allows light to pass through the scale side lens;
The distance between the aperture and the scale side lens is the focal length of the scale side lens,
In an optical plane perpendicular to the scale reading direction, the optical axis of the aperture and the optical axis of the light source are in a line-symmetric relationship with respect to the optical axis of the scale-side lens. Type encoder. The optical encoder according to claim 3, wherein
The head is
A light receiving element side lens disposed between the aperture and the light receiving element;
The distance between the aperture and the light receiving element side lens is the focal length of the light receiving element side lens,
An optical encoder, wherein an optical axis of the light receiving element side lens coincides with an optical axis of the scale side lens. The optical encoder according to claim 3, wherein
The head is
A light receiving element side lens disposed between the aperture and the light receiving element;
The distance between the aperture and the light receiving element side lens is the focal length of the light receiving element side lens,
The optical axis of the light receiving element side lens coincides with the optical axis of the scale side lens in the reading direction of the scale, and in the orthogonal direction perpendicular to the reading direction of the scale, the optical axis of the scale side lens An optical encoder characterized by being separated by a distance twice as long as the distance. The optical encoder according to claim 5, wherein
The head is
Two light sources, two scale-side lenses, and two apertures,
In a plane perpendicular to the scale reading direction, the optical axes of the light sources, the scale-side lenses, and the apertures are in a line-symmetric relationship with respect to the optical axis of the light-receiving element-side lens. An optical encoder characterized by the following. The optical encoder according to any one of claims 1 to 6,
The light source is
A light emitter that emits light;
An optical encoder comprising: a diffusing plate that is disposed downstream of an optical path of light emitted from the light emitter and diffuses light emitted from the light emitter. The optical encoder according to any one of claims 1 to 6,
The light source is
A light emitter that emits light;
A light emitter lens disposed downstream of the light path of the light emitted from the light emitter,
An optical encoder, wherein the scale side lens and the light emitting lens constitute Koehler illumination.

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