JP3649363B2 - Optical position detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical position detector for detecting the relative position of two members from a change in photoelectric conversion signal caused by relative displacement between a main scale having an optical grating and an index scale having an optical grating corresponding thereto. About.
[0002]
[Prior art]
Conventionally, there are optical position detectors that detect the relative positions of two members using an optical grating, for example, having a configuration as shown in FIGS. No. 74414).
That is, 1 is a light source fixed to one of two members that can move relatively, and 2 is a second scale fixed together with the light source 1 to one member.
The second scale 2 includes displacement signal light source grids 4A and 4B and an origin signal light source slit 7. In addition, an origin signal index slit 8, displacement signal index gratings 5 </ b> A to 5 </ b> D having phases different from each other by 90 degrees, an origin signal light receiving element 9, and displacement signal light receiving elements 6 </ b> A to 6 </ b> D are provided.
Reference numeral 3 denotes a first scale fixed to the other of the two members. A main grid for displacement signal, which is installed in parallel to the second scale 2 via a gap and is composed of a periodic grating having a constant pitch. 10 and an origin signal pattern 11 are provided.
With such a configuration, the displacement signal light source gratings 4A and 4B, the displacement signal index gratings 5A to 5D, the displacement signal light receiving elements 6A to 6D, and the displacement signal main grating 10 form the displacement signal generating means. Origin signal generating means is formed by the signal light source slit 7, origin signal index slit 8, origin signal light receiving element 9, and origin signal pattern 11.
Reference numeral 120 denotes a displacement signal generation circuit for receiving position signals A and B in response to output signals from the displacement signal light receiving elements 6A to 6D. Reference numeral 130 denotes an origin signal generation circuit that receives an output signal from the origin signal light receiving element 9 and outputs an origin signal Z.
[0003]
Irradiation light from the light source 1 irradiates the displacement signal main lattice 10 and the origin signal pattern 11 through the displacement signal light source lattices 4A and 4B and the origin signal light source slit 7, respectively.
The light reflected by the displacement signal main grating 10 on the first scale 3 irradiates the displacement signal light receiving elements 6A to 6D through the displacement signal index gratings 5A to 5D, respectively, and generates the displacement signal shown in FIG. The signal is converted into a voltage signal corresponding to the amount of light by the amplifiers 12A to 12D of the circuit unit 120.
As shown in FIGS. 6A and 6B, this voltage signal is a sinusoidal periodic signal va, vb, va ′, vb each having a phase difference of 90 degrees with respect to the movement of the detection target member. 'Become. Further, the signal va and the signal va ′ are compared with each other by the comparator 12E, and the signal vb and the signal vb ′ are compared with each other by the comparator 12F. As shown in FIGS. , B.
The light reflected by the origin signal pattern 11 on the first scale 3 irradiates the origin signal light receiving element 9 through the origin signal index slit 8 on the second scale 2, and the amplifier of the origin signal generation circuit unit 130. In 131, a voltage signal corresponding to the amount of light is converted.
When the detection target member passes a predetermined position, a pulse-like signal vz is obtained at the predetermined position as shown in FIG. Further, it is compared with the reference signal vc by the comparator 132 and converted to a digitized origin signal Z as shown in FIG.
[0004]
[Problems to be solved by the invention]
However, in the above-described conventional technique, the displacement signal generated by the periodic grating having a constant pitch has a large signal amplitude even if the gap between the first scale and the second scale is wide, and the SN ratio is large. A high signal is obtained.
However, the origin signal requires a steep pulse signal at a predetermined position, and the conventional origin signal generation means reduces the width of the origin signal pattern 11 and obtains an origin signal index slit in order to obtain a steep pulse signal. Although the slit width of 8 is reduced, the level of the detection signal is lowered because the diffraction effect and the amount of light to the light receiving element are reduced.
Further, when the grating width is increased, there is a problem that the width of the pulse-like detection signal becomes wide, a steep pulse signal cannot be obtained, and an accurate origin signal cannot be obtained.
An object of the present invention is to provide an optical position detector capable of obtaining a steep pulsed origin signal even when a gap between scales is wide.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a light source, a displacement signal generating means for receiving a light from the light source and generating a periodic displacement signal with respect to a relative displacement of a detection target member that moves relatively, Comprising origin signal generating means for receiving the light from the light source and generating the origin signal of the detection target member ,
The displacement signal generating means includes a first scale fixed to one member that moves relative to the second scale, and a second scale fixed to the other member that moves relative to the first scale while facing a gap. A displacement signal main grating formed on the first scale and having a periodic grating with a constant pitch, and a line formed by limiting the irradiation light from the light source formed on the second scale. A displacement signal light source grating that forms a light source, a displacement signal index grating that further restricts light reflected by the displacement signal main grating, and irradiation light that is restricted by the displacement signal index grating are received and electrically received. A displacement signal light-receiving element for converting into a signal, and a displacement signal generation circuit for generating the displacement signal from the output of the displacement signal light-receiving element,
The origin signal generation means generates origin auxiliary signal generation means for generating a plurality of constant period origin auxiliary signals having a period longer than the displacement signal in the vicinity of the origin position of the detection target member and having different periods, and the displacement In an optical position detector comprising an origin signal generation circuit that generates the origin signal from a signal and the origin auxiliary signal , the origin auxiliary signal generation means has a grating pitch longer than the displacement signal main grating, In addition, origin signal main gratings having different pitches formed in at least two locations on the first scale, and a linear light source formed on the second scale, limiting the irradiation light from the light source. Origin signal light source gratings having different pitches formed in at least two places to be formed, and at least further limiting light reflected by the origin signal main grating The origin signal index gratings formed at different locations and the origin signal light receiving element that receives the irradiation light limited by the origin signal index grating and converts it into an electrical signal, The signal generation circuit includes an origin auxiliary signal generation circuit that generates an origin auxiliary synthesis signal by synthesizing at least two types of origin auxiliary signals having different periods generated by the origin auxiliary signal generation unit; the origin auxiliary synthesis signal; and An origin signal synthesizing circuit that synthesizes the displacement signal and generates an origin analog signal, and a comparator that generates a pulsed origin signal from the origin analog signal. The origin auxiliary signal is composed of signals having two types of cycles, 2 to 4 times and 4 to 7 times the displacement signal.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below with reference to embodiments shown in the drawings.
FIG. 1 is a perspective view showing an embodiment of the present invention.
In the figure, a light source 1, a second scale 2, a first scale 3, displacement signal light source gratings 4A and 4B, displacement signal index gratings 5A to 5D, a displacement signal main grating 10, and a displacement signal light receiving element 6A to 6A. The displacement signal generating means including 6D and the displacement signal generating circuit unit 12 is substantially the same as the configuration shown in the conventional example.
What is different from the conventional example is the configuration of the origin signal generating means and the origin signal generating circuit.
That is, 7A is a first origin signal light source grid provided on the second scale 2, 7B is a second origin signal light source grid, 8A is a first origin signal index grid, and 8B is a second origin signal grid. The index grating, 9A is a first origin signal light receiving element, and 9B is a second origin signal light receiving element.
11A is a first origin signal main grid provided on the first scale 3, and 11B is a second origin signal main grid provided on the first scale 3.
[0007]
FIG. 2 is a block diagram showing the origin signal generation circuit unit 13.
The origin signal generation circuit unit 13 includes an origin auxiliary signal generation circuit 13X, an origin signal synthesis circuit 13Y, and a comparator 13F.
The origin auxiliary signal generation circuit 13X outputs the origin auxiliary signals vz1 and vz2 from the outputs from the first origin signal light receiving element 9A and the second origin signal light receiving element 9B via the amplifiers 13A and 13B. As for the origin auxiliary signals vz1 and vz2, the calculator 13C outputs an origin auxiliary synthesized signal Vz which is a differential signal.
On the other hand, the origin signal synthesizing circuit 13Y generates a displacement signal Va as shown in FIG. 3A from the operational amplifier 13D that receives the signals va and va ′ output from the amplifiers 12A and 12B of the displacement signal generation circuit section 6. Further, it is added to the origin auxiliary composite signal Vz by the comparator 13E to output the origin analog signal Vza.
The origin analog signal Vza is compared with the DC level Vc by the comparator 13F, and a pulsed origin signal Z is output.
[0008]
The light passing from the light source 1 through the first origin signal light source grating 7A is reflected by the first origin signal main grating 11A, passes through the first origin signal index grating 8A, and passes through the first origin signal index grating 8A. Irradiate 9A.
At this time, the grating pitch, the number of gratings, and the phase of the first origin signal light source grating 7A, the first origin signal main grating 11A, and the first origin signal index grating 8A are as follows. From 9A, the origin auxiliary signal vz1 (FIG. 3B) having a period three times that of the displacement signal va obtained by the displacement signal generation circuit unit 6 is output, and with respect to the displacement of the detection target member, The signal amplitude is maximized at the origin position, and the signal is generated only near the origin.
On the other hand, the light passing from the light source 1 through the second origin signal light source grating 7B is reflected by the second origin signal main grating 11B, passes through the second origin signal index grating 8B, and passes through the second origin signal index grating 8B. The light receiving element 9B is irradiated.
At this time, the grating pitch, the number of gratings, and the phase of the first origin signal light source grating 7B, the first origin signal main grating 11B, and the first origin signal index grating 8B are the same as those of the second origin signal light receiving element. 9B outputs an origin auxiliary signal vz2 (FIG. 3C) having a period five times that of the displacement signal va, and the signal amplitude becomes maximum at the origin position relative to the displacement of the detection target member, and only near the origin. In this way, a signal is generated.
[0009]
With such a configuration, the light from the light source 1 is received by the first origin signal light receiving element 9A and the second origin signal light receiving element 9B, and two origin auxiliary signals vz1 and vz2 having different periods are obtained. As a differential signal, the origin auxiliary composite signal Vz as shown in FIG. 3D is obtained. Furthermore, by combining with the displacement signal Va having a short cycle, an origin analog signal Vza having a steep peak at the origin position as shown in FIG. 3E is obtained.
Therefore, even if the gap between the scales is wide, as shown in FIG. 3 (f), a narrow pulse-like origin signal Z is obtained, and an origin signal with high accuracy that can cope with high resolution is obtained.
In the above-described embodiment, the example in which the periods of the origin auxiliary signals vz1 and vz2 are formed to be 3 times and 5 times the displacement signal va has been described. However, the period of the origin assistance signal vz1 is 2 to 4 times the displacement signal va. The period of the auxiliary signal vz2 is in the signal range of 4 to 7 times the period of the displacement signal va, has a steep peak signal at the origin position, and the characteristics of this detector so that the signal level becomes small at other positions than the origin position. Select according to your needs.
Moreover, although the said Example demonstrated the example which applied this invention to the optical linear encoder, an optical rotary encoder is formed by forming a 1st scale in disk shape and a 2nd scale in a fan shape. It can also be applied.
[0010]
【The invention's effect】
As described above, according to the present invention, the origin auxiliary signal and displacement signal generated by a plurality of constant pitch periodic gratings are combined to obtain an origin signal having a steep peak at the origin position. Therefore, even if the gap between the scales is wide, there is an effect that it is possible to provide an optical position detector that can obtain a narrow pulse-like origin signal.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a displacement signal generation circuit unit and an origin signal generation circuit unit according to an embodiment of the present invention.
FIG. 3 is an explanatory diagram showing operation waveforms according to the embodiment of the present invention.
FIG. 4 is a perspective view showing a conventional example.
FIG. 5 is a block diagram illustrating a conventional displacement signal generation circuit and an origin signal generation circuit.
FIG. 6 is an explanatory diagram showing operation waveforms of a conventional example.
[Explanation of symbols]
1: Light source, 2: Second scale, 3: First scale, 4A, 4B: Displacement signal light source grating, 5A, 5B, 5C, 5D: Displacement signal index grating, 6A, 6B, 6C, 6D: Displacement signal light receiving element, 7A: first origin signal light source grating, 7B: second origin signal light source grating, 8A: first origin signal index grating, 8B: second origin signal index grating, 9A: first origin signal light receiving element, 9B: second origin signal light receiving element, 10: displacement signal main grid, 11A: first origin signal main grid, 11B: second origin signal main 12: Displacement signal generation circuit unit, 13: Origin signal generation circuit unit, 13X: Origin auxiliary signal generation circuit, 13Y: Origin signal synthesis circuit, 13F: Comparator

Claims (2)

A light source, a displacement signal generating means for generating a periodic displacement signal by receiving light from the light source with respect to a relative displacement of the relative detection target member; and the detection target member receiving light from the light source Origin signal generating means for generating the origin signal of
The displacement signal generating means includes a first scale fixed to one member that moves relative to the second scale, and a second scale fixed to the other member that moves relative to the first scale while facing a gap. A displacement signal main grating formed on the first scale and having a periodic grating with a constant pitch, and a line formed by limiting the irradiation light from the light source formed on the second scale. A displacement signal light source grating that forms a light source, a displacement signal index grating that further restricts light reflected by the displacement signal main grating, and irradiation light that is restricted by the displacement signal index grating are received and electrically received. A displacement signal light-receiving element for converting into a signal, and a displacement signal generation circuit for generating the displacement signal from the output of the displacement signal light-receiving element,
The origin signal generation means generates origin auxiliary signal generation means for generating a plurality of constant period origin auxiliary signals having a period longer than the displacement signal in the vicinity of the origin position of the detection target member and having different periods, and the displacement In an optical position detector comprising an origin signal generation circuit that generates the origin signal from a signal and the origin auxiliary signal ,
The origin auxiliary signal generating means has a grating pitch longer than that of the displacement signal main grating and is formed at least at two places on the first scale with origin grating main gratings having different pitches, 2 is formed on the scale of 2 and restricts the light emitted from the light source to form a linear light source, and is reflected on at least two origin signal light source gratings having different pitches and reflected on the origin signal main grating. Origin signal index gratings having different pitches formed in at least two places for further restricting the emitted light, and origin signal for receiving irradiation light restricted by the origin signal index gratings and converting them into electrical signals It consists of a light receiving element,
The origin signal generating circuit includes an origin auxiliary signal generating circuit for generating an origin auxiliary synthesized signal by synthesizing at least two types of origin auxiliary signals having different periods generated by the origin auxiliary signal generating means, and the origin auxiliary synthesized signal. An optical position detector comprising: an origin signal synthesizing circuit that generates an origin analog signal by synthesizing the displacement signal and the displacement signal; and a comparator that generates a pulsed origin signal from the origin analog signal . . The origin auxiliary signal is 2 to 4 times and 4-7 times two optical position detector according to claim 1, wherein comprising a periodic signal of the displacement signal.

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