JP2562479B2 - Reflective XY encoder - Google Patents

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type XY encoder, and more particularly, to a relative displacement between two members which are relatively movable in a two-dimensional direction and are suitable for use in detecting displacement of an XY table or the like. Reflective XY, capable of detecting quantity with a single encoder
It concerns encoders.

[Prior art]

Linear encoders and rotary encoders are known as devices for detecting relative displacement between two members that move relative to each other, but in any case, linear displacement or rotational displacement is only one-dimensionally measured. It has not been possible to detect the relative displacement between two members that move relative to each other in the dimension direction with a single encoder. Therefore, conventionally, a first linear encoder for detecting the displacement in the X direction is provided in the member in which the displacement in one direction between the two members, for example, the X direction, is provided. Direction, for example, a member in which a displacement in the Y direction is present, is provided with a second linear encoder for detecting the displacement in the Y direction, and the output of these two linear encoders causes a difference between the two members. It was necessary to detect the relative displacement. Therefore, two sets of encoders are required, which makes the configuration complicated and expensive. Also, the direction you want to measure the relative displacement, eg X
If there is no member in which the displacement in the Y-direction and the Y-direction is present, the X-direction and the Y-direction are determined by some mechanical method.
It is necessary to create directional displacements and configure these displacements to be measured by two encoders respectively. Furthermore, there is a problem in that a two-dimensional component of relative displacement cannot be directly extracted with a single encoder.

[Problems to be achieved by the invention]

The present invention has been made to solve the above-mentioned conventional problems, and an encoder having a single compact detector for the X-direction and Y-direction components of the relative displacement of two members that relatively move in a two-dimensional direction. It is an object of the present invention to provide a reflection type XY encoder that can be directly detected by the.

[Means for achieving the object]

The present invention relates to a reflection-type main scale, in which a reflection type XY encoder is attached to one member that relatively moves in a two-dimensional direction, and a main grid of a rectangular island pattern that is periodic in the two-dimensional direction is formed. And attached to the other member,
A striped pattern, which is arranged independently of each other in each of the two-dimensional directions at positions on the circumference of the circle approximately equidistant from the center, and which is periodic in each of the directions, is formed. A transmission type index scale having a plurality of sub-lattices,
An opening formed in the central portion of the index scale at a position substantially equidistant from the sub-lattice in each direction, and arranged in the vicinity of the opening, and uniform in almost all directions from the opening toward the main lattice. A point-like light source for irradiating various diffused light, the signal from the point-like light source passing through the opening to be radiated / reflected by the main grating of the main scale, and which is affected by the sub-lattice of the index scale. On the basis of the above, the at least two periodic detection outputs corresponding to the X-direction and Y-direction components of the relative displacement of the both members are generated to achieve the above object. Further, the pitches of the main lattice and the sub lattice are respectively set to X
The pitch is the same in the Y and Y directions. The point light source is a secondary point light source generated in the aperture by converging illumination light from a separate light source to the main grating.

[Action and effect]

In the present invention, a main lattice 12 that is periodic in the two-dimensional direction (X direction and Y direction) as shown in FIG. 1A is formed on one of the members that relatively moves in the two-dimensional direction. Mount the reflective main scale 10. On the other hand, in the other member, as shown in FIG. 1 (B), for example, a sub-lattice 22 corresponding to the main lattice 12 is formed which is periodic in the two-dimensional direction (X direction and Y direction). Install the model index scale 20. Therefore, the light reflected by the main scale 10 and transmitted through the index scale 20 is received by the light receiving element for each sub-lattice, so that the relative displacement in the X direction and the Y direction.
At least two periodic detection signals corresponding to the directional component can be generated. Therefore, it becomes possible to simultaneously detect the relative displacement between the two members that relatively move in the two-dimensional direction with a single encoder. Therefore, it is not necessary to provide a linear encoder for each direction, and a highly accurate and high resolution XY encoder can be realized in a small size. Furthermore, since it is a reflective type, it is easy to handle. Further, as shown in FIG. 1 (A), the main lattice 12 is
Since the island-shaped pattern is arranged in the two-dimensional direction and the sub-lattice 22 is a stripe pattern independently arranged in the X-direction and the Y-direction as shown in FIG. 1B, The sub-lattice can be easily formed, and a detection signal having a relatively high level can be generated. Further, a light receiving element similar to the conventional one can be used, and the configuration for generating the detection signal is also simple. Further, as shown in FIG. 1 (B), openings 24 are formed in the central portion of the index scale 20 at positions substantially equidistant from the sub-lattice in each direction, and are arranged in the vicinity of the openings 24. Since the illumination light to the main grating is made to pass from the point light source that radiates the diffused light uniformly in all directions, it is possible to obtain the uniform illumination light with a small configuration, and it is possible to perform highly accurate measurement. . Further, when the pitches of the main lattice 12 and the sub-lattice 22 are the same pitch in the X direction and the Y direction, respectively, as shown in FIGS. 1A and 1B, in the X direction and the Y direction, respectively. The resolution can be the same. If it is desired to detect with different resolution depending on the direction, it is possible to change the pitch depending on the direction. Further, the pitches of the main grating 12 and the sub grating 22 can be set to different values according to the type of the object (image) to be detected. Further, when the point light source is a secondary point light source generated by focusing the illumination light from a separate light source to the main grating to generate the secondary light source, the light source can be arranged easily.

【Example】

Hereinafter, embodiments of the present invention applied to an optical scale will be described in detail with reference to the drawings. In this embodiment, the illumination system includes a diffused light source 30 including a laser diode (LD) chip 34 stored in a storage container 32.
It is composed of The diffused light source 30 is a cylindrical distributed refractive index type LD chip 34 as a primary point light source and a condenser lens for converging divergent light from the LD chip 34 to generate a secondary point light source 41. A lens 40 (for example, Selfoc lens, trade name of Nippon Sheet Glass Co., Ltd.) is included, and the secondary point light source 41 is focused on the sub-lattice forming surface (chrome vapor deposition surface) 21 of the index scale 20. Has been The main scale 10 is constituted by, for example, a glass plate as shown in FIG. 1 (A) by enlarging the cross section taken along the line AA in FIG. 2, and its surface opposite to the diffused light source 30.
By depositing chrome on 14 and then leaving it in an island shape by etching, for example, the main grating 12 composed of the reflecting portion 12A and the transparent portion 12B is formed. Here, the main grating 12 is formed on the diffused light source 30 and the reflection-side surface 14 in order to downsize the detector by the thickness of the main scale 10. The size of the main grating 12 is formed such that the transparent portion 12B and the reflecting portion 12A have the same length and the same pitch P = 8 μm in both the X direction and the Y direction. In this way, when a square island is formed with the same pitch in the X and Y directions, the same resolution can be obtained in the X and Y directions. When the island is rectangular and the pitch of the sub-lattice is changed accordingly, different resolutions can be obtained in the X direction and the Y direction. The sub-lattice forming surface (chrome vapor deposition surface) 21 of the index scale 20 has the main lattice 12 and the main lattice 12 as shown in FIG. 1 (B) by enlarging the cross section taken along the line BB in FIG. There are four corresponding sub-lattices 22 in the X direction (22Ax, 22Bx, 22x, 22
x), 4 in Y direction (22Ay, 22By, 22y, 22y)
8 in total are formed. Each of the sub-lattices 22Ax, 22Bx, 22x, 22x has a striped pattern elongated in the Y direction so as to detect a displacement component in the X direction, and the phases are 0 at the same pitch.
It is divided into four sections corresponding to °, +90 °, +180 °, and -90 °. Also, the sub-lattice 22Ay, 22By, 22
Both y and 22y are striped patterns that are long in the X direction in order to detect the displacement component in the Y direction, and the phases correspond to 0 °, + 90 °, + 180 °, and -90 ° respectively in the same pitch. It is arranged in sections. The sub-lattice 22Ax, 22Bx, 22x, 22x, 22Ay, 22By,
The opening 24 through which the secondary point light source 41 is focused and passes is formed in the center of 22y. In the opening 24, the divergent light of the LD chip 34 is focused by the distributed index lens 40, and a secondary point light source 41 is formed. Each sub-lattice 22Ax, 22Bx, 22x, 22x, 22Ay, 22By,
22y, on the back side of 22y, the reflecting portion 12A of the main grating 12 is provided.
Eight light receiving elements 46Ax, 46Bx, 46x, 46x, 46Ay, 46By, which photoelectrically convert the light from the diffused light source 30 that has been reflected by, and has passed through any of the corresponding sub-gratings,
46y and 46y are provided. These light receiving elements 46
Ax, 46Bx, 46x, 46x, 46Ay, 46By, 46y, 46
y is provided on the light receiving substrate 48, and these are shown in FIG. 1 (B).
The positional relationship is as indicated by the broken line. The distributed index lens 40 is also inserted in the center of the light receiving substrate 48. The light receiving elements 46Ax, 46Bx, 46x, 46x, 46Ay, 46
As shown in FIG. 3, the signal generating circuit 50 for forming two-phase detection signals having 90 ° different phase differences in the X direction and the Y direction from the outputs of By, 46y, and 46y is provided with the light receiving element 46Ax.
Operational amplifier (op-amp) OP whose amplification factor is variable by the variable resistor VR1 for amplifying the output signal Ax of
1, an operational amplifier OP2 whose amplification factor is variable by a variable resistor VR2 for amplifying the output signal x of the light receiving element 46x, and a differential signal (x-Ax) of the outputs of the operational amplifiers OP2 and OP1. ) Is output as a first phase (Ax phase) signal in the X direction, and the amplification factor is made variable by a variable resistor VR3 for amplifying the output signal Bx of the light receiving element 46Bx. Operational amplifier OP4 and the light receiving element 46
variable resistor VR4 for amplifying the output signal x of x
The operational amplifier OP5 whose amplification factor is variable, and the differential signal (−Bx) of the outputs of the operational amplifiers OP5 and OP4,
An operational amplifier OP6 which outputs as a second phase (referred to as Bx phase) in the X direction having a phase difference of 90 ° from the Ax phase signal, and the light receiving element 46A.
An operational amplifier OP7 whose amplification factor is variable by a variable resistor VR5 for amplifying the output signal Ay of y, and a variable resistor for amplifying the output signal y of the light receiving element 46y.
The operational amplifier OP8 whose amplification factor is variable by VR6 and the differential signal (y-Ay) output from the operational amplifiers OP8 and OP7 are set to Y.
An operational amplifier OP9 which outputs as a first phase (Ay phase) signal in the direction, and an operational amplifier OP10 whose amplification factor is variable by a variable resistor VR7 for amplifying the output signal By of the light receiving element 46By. , The output signal y of the light receiving element 46y
And an operational amplifier OP11 whose amplification factor is variable by a variable resistor VR8, and the operational amplifiers OP11 and OP10.
Of the operational amplifier OP12 which outputs the differential signal (y-By) as the second phase (By phase) signal in the Y direction having a phase difference of 90 ° from the Ay phase signal. The operation of the embodiment will be described below. First, consider a case where the index scale 20 moves only in the X direction or only in the Y direction with respect to the main scale 10. For example, when the relative displacement does not occur in the Y direction but the relative displacement only in the X direction, only the Ax phase signal and the Bx phase signal change, and the Ay phase signal and the By phase signal do not change. Therefore, using the two-phase detection signals (Ax phase signal and Bx phase signal) whose phases are different from each other by 90 °, for example, the phase division is performed in the same manner as in the past, and the displacement amount in the X direction is detected with high accuracy. can do. Conversely, when the relative displacement does not occur in the X direction but only in the Y direction, the Ax phase signal and the Bx phase signal do not change, and
Only the phase signal and the By phase signal change. Therefore, using the two-phase detection signals (Ay-phase signal and By-phase signal) whose phases are different from each other by 90 degrees, for example, phase division is performed in the same manner as in the past, and the displacement amount in the Y direction is detected with high accuracy. can do. Note that, unlike the conventional example, the main lattice 12 formed on the main scale 10 has an island-shaped pattern, so the light reflection is halved compared to the conventional striped pattern, and The obtained signal is about half that of the conventional linear encoder, but it can be easily dealt with by increasing the amplification factor of the operational amplifier. Further, when the relative displacement is made in both the X direction and the Y direction, the Ax phase signal, the Bx phase signal, the Ay phase signal, and the By phase signal all change. At this time, a signal corresponding to the X-direction component of the relative displacement appears in the Ax phase signal and the Bx phase signal, and a component corresponding to the Y direction displacement appears in the Ay phase signal and the By phase signal. The direction displacement amount and the Y direction displacement amount can be detected independently. In this embodiment, the secondary point light source 41 is formed by using the distributed index lens 40 as the condenser lens, and the displacement in each direction is detected by applying the diffraction phenomenon of the semiconductor laser diode or the like. An almost ideal small point light source can be obtained, and the mounting tolerance is large. The principle of detecting the displacement in each direction and the method of forming the point light source are not limited to this, and the laser diode can be directly used as the point light source, or a tungsten lamp or a light emitting diode other than the laser diode can be used. . Further, the number of sub-lattices is not limited to eight, and when it is not necessary to perform phase division or the like, the number of sub-lattices can be two in each direction, for example, four in total. Furthermore, in this embodiment, since the secondary point light source 41 is formed by focusing on the small round opening 24 on the sub-grid formation surface 21, extra scattered light may be radiated to the main grid 12. It is possible to obtain a detection signal with a good S / N ratio. In addition,
The shape and size of the opening 24 for passing the illumination light beam is not limited to this. Further, in this embodiment, since the corresponding light receiving element is arranged immediately after the sub-lattice, the structure is simple and the size is small. The position of the light receiving element is not limited to this,
For example, by using an optical fiber or the like, it can be arranged at a position apart from the corresponding sub-grating. Further, in this embodiment, since the main scale 10 is made of glass and the main lattice 12 is formed on the outer surface thereof,
The detector can be further miniaturized by the thickness of the main scale 10. The configuration of the main scale is not limited to this, and may be, for example, a metal reflection type scale.

[Brief description of drawings]

FIG. 1 (A) is an enlarged cross-sectional view showing an example of the shape and arrangement of the main lattice on the main scale for explaining the principle of the present invention, and FIG. 1 (B) is also on the index scale. Second, an enlarged cross-sectional view showing an arrangement example of the sub-grating and the light receiving element,
FIG. 3 is a sectional view showing the construction of the embodiment of the reflection type XY encoder to which the present invention is applied, and FIG. 3 is a block diagram showing the construction of the signal generating circuit of the embodiment. 10 …… Main scale, 12 …… Main lattice, 14 …… Main lattice forming surface, 20 …… Index scale, 21 …… Sub lattice forming surface, 22, 22Ax, 22Bx, 22x, 22x, 22Ay, 22By, 22
y, 22y ... Sub lattice, 24 ... Aperture, 30 ... Diffuse light source, 46Ax, 46Bx, 46x, 46x, 46Ay, 46By, 46y, 46
y: light receiving element, 50: signal generation circuit.

Front page continuation (72) Hideki Oka Inventor Hideki Oka 165 Sakado, Takatsu-ku, Kawasaki City, Kanagawa Mitsutoyo R & D Headquarters (56) Reference JP-A-63-24128 (JP, A) JP-A-58-100703 (JP, A) JP-A-60-67822 (JP, A)

Claims (3)

(57) [Claims] 1. A reflection-type main scale that is folded on one member that relatively moves in a two-dimensional direction and that forms a main grid of a rectangular island pattern that is periodic in the two-dimensional direction, and another. It is attached to a member, is provided independently of each other in each of the two-dimensional directions at positions on the circumference of the circle that are substantially equidistant from the center, and is periodic in each of the directions. , A transmission type index scale having a plurality of striped sub-lattices formed therein, an opening formed in the central portion of the index scale at positions substantially equidistant from the sub-lattices in each direction, and A point light source that is disposed in the vicinity and irradiates diffused light that is uniform in almost all directions from the opening toward the main grating, and passes from the point light source through the opening to the main scale of the main scale. The index is illuminated and reflected by the grid. A reflection characterized in that it produces at least two periodic detection outputs corresponding to the X-direction and Y-direction components of the relative displacement of the two members, based on the signals involved by the sub-lattice of the X-scale. Type XY encoder. 2. The reflection type XY encoder according to claim 1, wherein the pitches of the main grating and the sub grating are the same pitch in the X direction and the Y direction, respectively. 3. The point light source according to claim 1, wherein the point light source is a secondary point light source generated in the aperture by converging the irradiation light from a separate light source to the main grating. Reflective
XY encoder.