JP2006284563A - Photoelectric encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain the patterns and shapes of images while achieving compactness and enlarging a field of view on a scale. <P>SOLUTION: In this photoelectric encoder having an optical system in which a lens array 46 is inserted between main scales 20 and light reception elements 34, images divided and reversed by the lens array 46 are electrically or optically once again reversed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a photoelectric encoder. In particular, the present invention relates to an improvement in a photoelectric encoder having a telecentric optical system in which a lens and an aperture are inserted between a main scale and a light receiving element.

  As described in Patent Document 1, as shown in FIG. 1, a lens 42 and an aperture 44 serving as a telecentric optical diaphragm are disposed between a main scale 20 and, for example, a light receiving element array 34 constituting the light receiving unit 30. A lens optical system (telecentric optical system) 40 is inserted to adjust the distances a and b between the lens 42 and the scale 21 of the main scale 20 and the light receiving elements 35 on the light receiving element array 34 as shown in FIG. Thus, a photoelectric encoder that can set the magnification is considered. In FIG. 1, 10 is a light source, and f is a focal length of the lens 42.

  In the photoelectric encoder using the telecentric optical system 40, an image on the main scale 20 is projected onto the light receiving element array 34 through the lens optical system (42, 44). Here, by arranging the aperture 44 at the focal position of the lens 42, even if the distance (gap) between the main scale 20 and the lens 42 varies, the positional relationship between the lens 42, the aperture 44, and the light receiving element array 34 varies. Otherwise, the magnification fluctuation of the image formed on the light receiving element array 34 can be suppressed. In particular, when the lens array 46 is used as the lens 42 as shown in FIG. 3 (optical path diagram) and FIG. Can do.

JP 2004-264295 A

  However, when a photoelectric encoder is configured with such a lens array 46, as shown in FIGS. 3 and 5, there is a problem that an image is divided and inverted for each lens optical system. It was.

  This problem becomes a big problem particularly in the absolute type that needs to reproduce not only the pattern of the image but also the accurate shape.

  The present invention has been made to solve the above-described conventional problems, and a first object thereof is to provide an incremental photoelectric encoder capable of maintaining an image pattern.

  A second object of the present invention is to provide a photoelectric encoder capable of maintaining not only the pattern of an image but also the shape thereof.

  According to the present invention, in the incremental photoelectric encoder having a lens array between the main scale and the light receiving element, the arrangement pitch of each lens is made to coincide with a natural number multiple of the period of the main scale. This is a solution to this problem.

  In the photoelectric encoder having a lens array between the main scale and the light receiving element, the connection of the output of the light receiving element array is switched, and the image divided and inverted by the lens array is electrically By re-inversion, the second problem is solved.

  In the photoelectric encoder having the first lens array between the main scale and the light receiving element, the second lens array having the same arrangement pitch of the lenses as the first lens array, Similarly, the second problem is solved by providing a third lens array for optically re-inverting the light emitted from the second lens array.

  The focal length of each lens of the third lens array is shorter than the focal length of each lens of the first and second lens arrays, and the total optical length is shortened.

  The present invention also provides a photoelectric encoder having a lens array between a main scale and a light receiving element, a second lens array having the same lens arrangement pitch as the first lens array, and an arrangement pitch of the first lens array. A plurality of small mirrors that are the same as each lens of one lens array are provided, and the second problem is solved by optically re-inverting the image divided and inverted by the first lens array by the small mirror. Is.

  In the photoelectric encoder having a lens array between the main scale and the light receiving element, the second lens array having the same lens arrangement pitch as the lens array and the second lens array are provided. And a half mirror for taking out the light that has passed through the first lens array and the second lens array twice in the direction of the light receiving element. And the second problem is solved by optically re-inverting the image divided and inverted by the lens array by the mirror.

  The lens array is a two-dimensional lens array, and two-dimensional measurement is possible.

  Further, by providing an aperture at the focal position of each lens array, light from the adjacent lens can be blocked.

  According to the present invention, it is possible to maintain the image pattern in the incremental photoelectric encoder by matching the arrangement pitch of each lens of the lens array with a natural number multiple of the period of the main scale.

  In addition, by reversing the image reversed by the lens array electrically or optically, the shape of the image can be maintained, and it can be used not only for the incremental type but also for the absolute type.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In the first embodiment of the present invention, as shown in FIG. 6, in an incremental type photoelectric encoder having a lens array 46, an arrangement pitch (referred to as a lens pitch) Pl of each lens constituting the lens array 46 is set as a main. This is the same as the natural number times the period Ps of the scale 20.

  In the present embodiment, as shown in FIG. 7, even if an image is divided and inverted for each lens, the pattern is guaranteed, so that there is no problem as long as it is used as an incremental type.

  Further, as in the modification shown in FIG. 8, the telecentric optical system 40 in which the aperture 44 is disposed at the focal position of each lens constituting the lens array 46 can be used.

  Next, a second embodiment of the present invention will be described in detail with reference to FIG. 9 (optical path diagram) and FIG. 10 (perspective view).

  In the present embodiment, the second lens array 48, which is the same as the lens array 46 (also referred to as the first lens array), is inserted in the reverse direction so that the focal point comes to the focal point of the first lens array. 50.

  In the present embodiment, since the lens arrays 46 and 48 are the same, the aberration generated in the first lens array 46 on the input side can be almost completely reversely corrected in the second lens array 48 on the output side. Even in the case of using a lens array that is inexpensive but has large aberrations, the aberration can be canceled almost completely and the signal detection efficiency can be greatly improved.

  Further, as in the modification shown in FIGS. 11 and 12, the optical system 50 may be a double-sided telecentric optical system 51 in which the aperture 44 is disposed at the focal position of each lens constituting the lens arrays 46 and 48. it can.

  Next, a third embodiment of the present invention will be described in detail with reference to FIG.

  In this embodiment, in an absolute type photoelectric encoder having a lens array 46, the connection of the output of the light receiving element array 34 is exchanged in units of pixels to electrically reinvert the image.

  Further, as in the modification shown in FIG. 14, the telecentric optical system 40 in which the aperture 44 is disposed at the focal position of each lens constituting the lens array 46 can be used.

  Next, a fourth embodiment of the present invention will be described in detail with reference to FIG.

  In this embodiment, in an absolute type photoelectric encoder having an optical system 50 composed of lens arrays 46 and 48, the output of the light receiving element array 34 is switched in units of pixels to electrically reinvert the image. It is a thing.

  According to the third and fourth embodiments, an absolute type can be realized without complicating the optical system.

  Further, as in the modification shown in FIG. 16, the optical system 50 can be a double-sided telecentric optical system 51 in which the apertures 44 are arranged at the focal positions of the individual lenses constituting the lens arrays 46 and 48.

  Next, a fifth embodiment of the present invention will be described in detail with reference to FIG.

  In the present embodiment, in an absolute type photoelectric encoder having an optical system 50 including lens arrays 46 and 48, the same third lens array 52 as the first and second lens arrays 46 and 48 is provided to the output of the optical system 50. And the image is optically re-inverted.

  Further, as in the modification shown in FIG. 18, the optical system 50 is a double-sided telecentric optical system 51 in which apertures 44 are arranged at the focal positions of the individual lenses constituting the lens arrays 46 and 48, and the lens array. The aperture 54 can be disposed at the focal position of each lens constituting the lens 52.

  Next, a sixth embodiment of the present invention will be described in detail with reference to FIG.

  This embodiment is an absolute type photoelectric encoder having an optical system 50 including lens arrays 46 and 48, and includes an optical system including a third lens array 52 and a fourth lens array 56 having the same configuration as the optical system 50. A system 60 is provided on its exit side to reinvert the image.

  In the present embodiment, since the same optical system is used on the entry side and the exit side, parts can be shared.

  Further, as in the modification shown in FIG. 20, the optical system 50 is a double-sided telecentric optical system 51 in which the apertures 44 are arranged at the focal positions of the individual lenses constituting the lens arrays 46 and 48, and the optical system 60. Alternatively, a double telecentric optical system 61 in which an aperture 54 is disposed at the focal position of the individual lenses constituting the lens arrays 52 and 56 may be used.

  Next, a seventh embodiment of the present invention will be described in detail with reference to FIG.

  In the present embodiment, the focal length f ′ of the third lens array 52 is set to be larger than the focal lengths f of the first and second lens arrays 46 and 48 in the same photoelectric encoder as that of the fifth embodiment shown in FIG. In other words, the optical total length is shortened, and the air gap between the main scale 20 and the entrance-side lens array 46 is secured, thereby enabling a reduction in size.

  That is, if the distance between the main scale 20 and the entrance lens array 46 (corresponding to an air gap) = the focal length f of the entrance lens array 46, the first to third lens arrays are the same as in the fifth embodiment. When configured with a lens, the optical total length L≈8f, whereas in the seventh embodiment, the optical total length L ′ = 4f + 4f ′ <8f, and the optical total length can be shortened.

  Next, an eighth embodiment of the present invention will be described in detail with reference to FIG.

  In this embodiment, in the same photoelectric encoder as that in the sixth embodiment shown in FIG. 20, the focal lengths f ′ of the third and fourth lens arrays 52 and 56 are set to the first and second lens arrays 46 and 48. Is shorter than the focal length f, and the total optical length is shortened, and an air gap between the main scale 20 and the entrance lens array 46 is secured, thereby enabling miniaturization.

  That is, when the distance between the main scale 20 and the entrance lens array 46 (corresponding to an air gap) = the focal length f of the entrance lens array 46, the first to fourth lens arrays are the same as in the sixth embodiment. When configured with a lens, the optical total length L≈8f, whereas in the eighth embodiment, the optical total length L ′ = 4f + 4f ′ <8f, and the optical total length can be shortened.

  Next, a ninth embodiment of the present invention will be described in detail with reference to FIG.

  In this embodiment, in an absolute type photoelectric encoder having an optical system 50 including lens arrays 46 and 48, a plurality of small mirrors 70 having the same arrangement pitch as the lenses of the lens arrays 46 and 48 are provided, and an image is obtained. Optically re-inverted.

  Further, as in the modification shown in FIG. 24, the optical system 50 can be a double-sided telecentric optical system 51 in which the apertures 44 are arranged at the focal positions of the individual lenses constituting the lens arrays 46 and 48.

  Next, a tenth embodiment of the present invention will be described in detail with reference to FIG.

  In this embodiment, in an absolute type photoelectric encoder having an optical system 50 composed of lens arrays 46 and 48, a mirror 80 for re-entering the light exiting the lens array 48 on the exit side into the optical system 50; The image is optically re-inverted by including a half mirror 82 for taking out light that has passed through the optical system 50 twice in the direction of the light receiving element array 34.

  Further, as in the modification shown in FIG. 26, the optical system 50 can be a double-sided telecentric optical system 51 in which the aperture 44 is disposed at the focal position of each lens constituting the lens arrays 46 and 48.

  The third to tenth embodiments can be applied not only to the absolute type but also to the incremental type.

  The present invention can be applied to both an index grating and a light receiving element that are separated, and a light receiving element array in which both are integrated. Furthermore, the present invention can be applied not only to a transmission type encoder but also to a reflection type encoder.

The perspective view which shows the principal part structure of the photoelectric encoder using a telecentric optical system Same top view Optical path diagram showing conventional problems Same perspective view Same top view FIG. 1 is an optical path diagram showing the main configuration of the first embodiment of the present invention. Diagram showing the principle of the present invention The figure which shows the modification of 1st Embodiment. Optical path diagram showing the configuration of the main part of the second embodiment of the present invention. Same perspective view The figure which shows the modification of 2nd Embodiment. Same perspective view Optical path diagram showing the configuration of the main part of the third embodiment of the present invention. The figure which shows the modification of 3rd Embodiment. Optical path diagram showing main components of the fourth embodiment of the present invention. The figure which shows the modification of 4th Embodiment. Optical path diagram showing main configuration of fifth embodiment of the present invention The figure which shows the modification of 5th Embodiment. Optical path diagram showing main configuration of sixth embodiment of the present invention. The figure which shows the modification of 6th Embodiment Optical path diagram showing main configuration of seventh embodiment of the present invention Optical path diagram showing main configuration of eighth embodiment of the present invention. Optical path diagram showing main components of the ninth embodiment of the present invention The figure which shows the modification of 9th Embodiment Optical path diagram showing essential configuration of the tenth embodiment of the present invention. The figure which shows the modification of 10th Embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Light source 20 ... Main scale 30 ... Light-receiving part 31 ... Light-receiving surface 34 ... Light-receiving element array 40 ... Telecentric optical system 44, 54 ... Aperture 46, 48, 52, 56 ... Lens array 50, 60 ... Optical system 51, 61 ... Telecentric optical system on both sides 70 ... Small mirror 80 ... Mirror 82 ... Half mirror

Claims (10)

In an incremental photoelectric encoder having an optical system in which a first lens array is inserted between a main scale and a light receiving element,
A photoelectric encoder characterized in that the arrangement pitch of each lens coincides with a natural number multiple of the period of the main scale. In a photoelectric encoder having an optical system in which a first lens array is inserted between a main scale and a light receiving element,
A second lens array in which the arrangement pitch of each lens is the same as the first lens array;
A third lens array for optically re-inverting the light exiting the second lens array;
A photoelectric encoder characterized by comprising:   The photoelectric encoder according to claim 2, wherein a fourth lens array is provided on the exit side of the third lens array.   The optical system configured by the first lens array and the second lens array and the optical system configured by the third lens array and the fourth lens array have the same configuration. 3. The photoelectric encoder according to 3.   5. The photoelectric system according to claim 2, wherein a focal length of each lens of the third lens array is smaller than a focal length of each lens of the first and second lens arrays. Encoder. In a photoelectric encoder having an optical system in which a first lens array is inserted between a main scale and a light receiving element,
A photoelectric encoder, wherein the output connection of the light receiving element array is switched to electrically reinvert the image divided and inverted by the first lens array. In a photoelectric encoder having an optical system in which a first lens array is inserted between a main scale and a light receiving element,
A second lens array having the same lens arrangement pitch as the first lens array;
A plurality of small mirrors having the same arrangement pitch as each lens of the lens array;
A photoelectric encoder, wherein an image divided and inverted by the first lens array is optically re-inverted by the small mirror. In a photoelectric encoder having an optical system in which a first lens array is inserted between a main scale and a light receiving element,
A second lens array having the same lens arrangement pitch as the first lens array;
A mirror for making light emitted from the second lens array re-enter the second lens array;
A half mirror for taking out light that has passed through the second lens array twice in the direction of the light receiving element;
A photoelectric encoder characterized in that an image divided and inverted by the first lens array is optically re-inverted by the mirror.   The photoelectric encoder according to claim 1, further comprising an aperture at a focal position of at least one of the lenses constituting the lens array.   The photoelectric encoder according to claim 1, wherein the lens array is a two-dimensional lens array.

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