JPH11101614A - Dimension measuring device using optical scale - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the structure of a measuring device and to make high- accuracy measurement by forming lattices at a multi-value intensity level having the intermediate light transmission intensity between white and black, and employing an optical scale setting the intensity distribution in the direction that the lattices are formed to asymmetrical distribution. SOLUTION: The light radiated from an illumination light source 30 and cast on an optical scale 10 via a collimation lens 31 passes the optical scale 10 or is reflected and received by a light receiver 32. For instance, the light passing the optical scale 10 has a wide spot, and the light passing many element lattices having the intermediate light transmission intensity between white and black, is mixed with it. A slit 320 having the width equal to or slightly wider than the width of the element lattices is fitted to the light receiving face of the light receiver 32, the transmission intensity from the optical scale 10 is detected through it, and a light intensity signal 33 is generated. The moving direction of a probe must be detected for size measurement, and a moving direction judgment section 34 detects the moving direction of the optical scale 10 based on the light intensity change of the light intensity signal 33.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dimension measuring apparatus using an optical scale on which a large number of gratings are formed.
The present invention relates to a configuration of a dimension measuring apparatus using an optical scale in which a grating having a multi-level intensity level is periodically formed.

[0002]

2. Description of the Related Art In a production line, there is a strong need to measure the size and shape of a workpiece with high accuracy (micron accuracy) on the spot, and a stylus-type dimension measuring device using an optical scale. Is often used. In this method, an optical scale (linear encoder) having a large number of grids with a black and white pattern is attached to a stylus and irradiated with light, and dimensions are measured from a change in light intensity that changes with movement of the stylus. Device. FIG. 5 shows a configuration example of a conventional optical scale type dimension measuring instrument. Light emitted from a light source 50 such as a white lamp or a light emitting diode is collimated by a collimator lens 51.
The optical scale 52 is illuminated via. The optical scale 52 has a structure in which a large number of gratings having a binary light transmission intensity of black and white are formed on a glass substrate. The width of the gap that becomes light (white) that transmits light is a / 2, and the width a is a reference scale for dimension measurement. Usually, one pitch length a of the grating is 10 to 20 μm. The optical scale 52 moves in the left-right direction with the movement of a stylus (not shown).

[0003] The slit 53 is composed of two slits of A phase and B phase, and is fixed and installed near the optical scale 52. The A-phase and B-phase slits are vertically separated, each having a width of a / 2, and being displaced by a / 4 in the horizontal direction. Optical scale 52
The light transmitted through the slit 53 is condensed by a condenser lens 54 and detected by a light receiver 55. The light receiver 55 is composed of two light receiving surfaces divided in the vertical direction, and separates and detects light transmitted through the A-phase slit and the B-phase slit, and performs photoelectric conversion. The two light intensity signals that have been photoelectrically converted are processed by the signal processing unit 56, and the movement distance of the stylus, that is, the dimension, is measured from the light intensity signals that have changed before and after the movement of the stylus.

FIG. 6 shows an example of a light intensity signal detected by a conventional method, and the operation of signal processing will be described. When the stylus is moving, signals 61 and 62 are detected. Signal 6
1 is a light intensity signal transmitted through the A-phase slit, and signal 62 is B
It is a light intensity signal transmitted through the phase slit. Since the grating pitch length a is small, the influence of diffraction appears, and the light intensity changes sinusoidally. The waveform in FIG. 6 shows a case where the phase of the B-phase signal 62 is ahead of the phase of the A-phase signal 61. The signal processing section 56 determines the relationship between the advance and the delay of the phase of the signal 61 and the signal 62, and determines the moving direction of the optical scale 52. For example, when the phase of the signal 62 is advanced with respect to the signal 61, it is determined that the optical scale 52 has moved to the left, and when the phase of the signal 62 is delayed,
It is determined that 2 has moved to the right.

The signal processing section 56 also performs a counter operation when the stylus is moving. When the stylus is moving, signals 61 and 62 are detected, and signal 61 or signal 6 is detected.
2 is converted into a rectangular wave, and the number of pulses is counted to detect the number of grid movements. Since one pulse of the rectangular wave is generated by one pitch of the grating, a moving distance that is an integral multiple of the length a of one grating pitch is detected. Further, the signal processing unit 56 also detects the stop position of the lattice when the stylus is stopped. At this time the pulse signal is not obtained, the two light intensity V ₁ and V ₂ having the strength of the constant DC level is detected. For example, the intensity corresponding to the position 63 is detected. Therefore, by comparing the two intensity levels V ₁ and V ₂ , it is determined which phase position of the sine wave the light intensity transmitted through the A-phase slit and the B-phase slit is, and interpolation is performed within one pitch of the grating. Then, the stop position of the grating is detected with a positional accuracy finer than the length a of one pitch.

[0006]

In the case of a conventional optical scale comprising a binary intensity grid, A is used for discriminating the moving direction.
Two slits of the phase and the B-phase are required, and the two slits are arranged at a distance of a / 4. For this reason, there is a manufacturing problem that the positional relationship between the two slits must be precisely formed with a precision of μm. Furthermore, A
When the light transmitted through the two slits of the phase and the B phase is detected by the light receiver, it is necessary to detect the light separately by the two light receiving elements. At this time, the position of the light receiving element and the slit must be accurately aligned in the vertical direction, and there is also a problem that it is difficult to align the two. Furthermore, when comparing and processing two light intensity signals detected by the light receiver to determine the moving direction of the optical scale, the circuit configuration for determining the advance or delay of the phase of the light intensity signal is complicated. There are also configuration issues.

The greatest factor in improving the dimension measurement accuracy is how to detect a moving distance smaller than the moving distance a of one pitch of the grating. That is, when determining the grid position when the stylus stops, it is important how to finely divide and detect one period of the grid. In the conventional measuring method, by comparing two light intensities V ₁ and V ₂ transmitted through two slits of A phase and B phase, a rough phase of a sine wave is detected and one period of the grating is divided and detected. Was. The division accuracy in this case was about １ ／ of the length a of one pitch of the grating. Therefore, when a = 20 μm, the dimension measurement accuracy is 3
There is a problem that the resolution is only on the order of μm and submicron resolution cannot be obtained. In order to increase the measurement resolution by a conventional measurement method, there is a method of preparing a large number of slits and comparing the intensity levels of light intensity signals transmitted through the slits. However, in this case, a photodetector having a large number of light receiving surfaces divided into many parts is required, and there is a problem that a signal processing circuit becomes complicated.

The above-mentioned problems are caused by the fact that the grating of the optical scale is composed of black and white binary intensities, and the intensity distribution in the direction in which the grating is formed is symmetric. The binary lattice has the advantage of the simplest structure, but the intensity is constant within the width a / 2 of each lattice, and position information inside the lattice cannot be obtained as it is. Further, since the intensity distribution is symmetric, it is necessary to detect two signals having different phases for detecting a moving direction. Furthermore,
In the binary grating, the light transmission intensity greatly changes between adjacent gratings, and since the length of one pitch is short, the influence of diffraction spread increases, and the light intensity changes in a shape in which a sine wave is distorted. Therefore, it is difficult to determine the phase between the two signals, and the accuracy of detecting the grating position is reduced. Therefore, in order to solve the above-mentioned problems, the present invention configures a grating with a multi-valued intensity level having an intermediate light transmission intensity between black and white, and asymmetrical intensity distribution in the direction in which the grating is formed. An object of the present invention is to realize a high-precision dimension measuring device having a simple configuration and adopting an optical scale.

[0009]

Means for Solving the Problems To solve the above problems, a dimension measuring apparatus according to the present invention has the following arrangement.
Illuminate the optical scale on which a grid of a certain shape is formed,
A dimension measuring device using an optical scale for measuring a dimension by detecting a change in light intensity caused by the movement of the optical scale, wherein n units of one element grid having a predetermined width and a predetermined light transmission intensity are used as a unit. Forming a grating from the element gratings, and providing the n element gratings with an optical scale in which a plurality of gratings having multi-valued intensity levels are formed with n different light transmission intensities. A light receiver for detecting the transmitted light intensity or the reflected light intensity of the light illuminating the scale is provided, a light intensity signal is output from the light receiver, and when the optical scale is moving, the light direction is determined by a moving direction determination unit. A direction in which the intensity of the intensity signal increases or decreases is detected to detect a moving direction of the optical scale, and a pulse of the light intensity signal generated by the movement of the optical scale in a grating movement counting unit. And detecting the maximum intensity and the minimum intensity of said light intensity signal, when the optical scale is stopped,
Before and after the movement of the optical scale, the position where the grating is stopped from the light intensity and the maximum intensity and the minimum intensity detected by the light receiver at the grating position detection unit is the position of the two adjacent element gratings. Movement distance information corresponding to the number of movements of the grid detected by the grid movement counting unit by the dimension calculation unit and the grid position are detected with a position detection accuracy smaller than the width of the element grid from the relationship of the intensity difference of the light transmission intensity. The dimensions are measured from the grid position information before and after the movement of the optical scale detected by the detection unit.

In the optical scale having the above-described structure, the light transmission intensity of the element grating is changed in steps at equal intervals in n steps, and the intensity distribution of one period of one grating formed by collecting n element gratings is obtained. The intensity distribution is triangular and asymmetric with respect to the direction in which the grating is formed. Further, with respect to the light receiver, the light receiver has a single light receiving surface, a slit having a width substantially equal to the width of each element grating forming the grid is attached to the light receiving surface, and the light transmitted through the slit is provided. The light intensity from the optical scale is detected, one light intensity signal is output, and the dimension is measured from the intensity of the light intensity signal.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention employs an optical scale on which a grating having a multivalued light transmission intensity distribution is formed, thereby simplifying the structure of the apparatus and improving the dimension measurement accuracy. A grating having a multi-valued light transmission intensity is a grating that includes not only binary intensity of black and white (light transmission intensity is 100% and 0%) but also various light transmission intensity in between. The grating according to the present invention has, as a basic unit, an element grating having a constant width and a constant light transmission intensity therein.
The n element gratings collectively form one grating, and the n element gratings have n different light transmission intensities. This grating is periodically formed to create an optical scale.

When one grating is formed, the light transmission intensity of the element grating is changed in n steps at regular intervals in a step-like manner. For example, the intensity is changed at regular intervals in steps of 20% between 0% and 100%. In this case, when the width of each element lattice is h, the width p of one period of the lattice is 6h.
Becomes For example, when h = 10 μm, p = 60 μm. At this time, the unit length serving as a reference for dimension measurement is the width h of the element grid. The intensity distribution linearly changes as an average value within one grid formed by collecting n element grids. At this time, the total width of the element grid in the direction in which the intensity increases and the total width of the element grid in the direction in which the intensity decreases are made different. That is, the configuration is such that the intensity distribution within one period of the grating is triangular, and the intensity distribution is asymmetric with respect to the direction in which the grating is formed. This asymmetry is an important requirement in signal processing of light intensity.

When the above-described grating having a multi-valued intensity distribution (hereinafter abbreviated as a multi-valued grating) moves with the movement of the stylus, the light illuminating the optical scale is transmitted or reflected. Is periodically changed in a triangular waveform. Therefore, there is a direction in which the light intensity increases from small to large and a direction in which the light intensity decreases from large to small. Since the intensity distribution width in the direction in which the light transmission intensity of the grating increases and in the direction in which the light intensity decreases is asymmetric, the periods of increase and decrease in the light intensity in each direction are different. Accordingly, the moving direction of the optical scale can be immediately determined only by detecting the direction of the light intensity change and the width of the change. At this time, since the above determination can be made only with a single light intensity signal, the light intensity may be detected by a light receiver having a single light receiving surface. Therefore, the two slits for determining the moving direction described in the related art become unnecessary, and it is not necessary to determine whether the phases of the two light intensity signals are advanced or delayed, and the moving direction can be determined with a simple circuit configuration.

When light is irradiated onto an optical scale composed of a multi-valued grating and transmitted light or reflected light is detected, a slit having a width substantially equal to the width h of each element grating constituting the grating is received. It is attached to the light receiving surface of the container and the light intensity is detected through the slit. The light receiver may be installed (fixed) at an arbitrary position in a region where the intensity of the irradiation light spot is high, and the degree of freedom of the installation position is high. The multi-valued grating has less influence of diffraction than the conventional binary grating (one pitch of the grating is long, and the intensity changes like a triangular wave), so that it changes discretely with the width of h due to the masking effect of the slit. The light intensity is converted to a linearly changing light intensity. For example,
When the center of the slit is located at the boundary between adjacent element gratings, the light intensity detected through the slit is the average of the two element intensities. Therefore, the light intensity signal detected by the light receiver while the grating is moving changes linearly into a triangular waveform.

One cycle of a triangular wave signal whose intensity changes linearly corresponds to the length p of one cycle of the grating. When the optical scale is moving, the number of movements N (integer) of the grating is counted from the number of movement pulses of the triangular wave signal, and a distance Np that is an integral multiple of the length p of one cycle is detected. The light intensity detected when the movement of the grating is stopped also changes linearly according to the position of the grating. Therefore, when the optical scale is stopped, the grid position is detected with a position accuracy smaller than the width h of the element grid from the detected light intensity value. At this time, based on the maximum intensity and the minimum intensity (intensity at the peak position) of the triangular wave signal detected while the lattice is moving, a difference between the reference and the element lattice is detected. The measurement resolution at this time is determined according to the resolution for detecting the light intensity. For example, if the light intensity is detected at 8 bits, it is possible to detect within one period of the grating by dividing it by 200. Therefore, even if the length of one pitch of the grating is 100 μm, the dimension can be measured with submicron accuracy.

[0016]

FIG. 1A shows an example of the configuration of an optical scale used in a dimension measuring apparatus according to the present invention. The optical scale 10 has a constant width h, a large number of element gratings 11 having a constant light transmission intensity gathered inside, and a grating having a constant intensity distribution composed of multi-valued intensity levels is periodically formed. It is. One lattice is composed of n element lattices, and the length of one pitch of the lattice is p = nh. The light transmission intensities of the element gratings constituting the grating are different from each other, and change at regular intervals in a step-like manner within one period of the grating. The illustrated grating has a black element grating 12 having a light transmission intensity of 0% and a light transmission intensity of 100%.
%, The light transmission intensity is 20%
In this example, p = 6h in a case where the number of steps changes in six steps as a whole. Within one pitch of the grating, the light transmission intensity is higher in the element grating on the right side, the intensity on the right side of 100% intensity is 0%, and there is a 100% intensity change between the gratings. Regarding the direction in which the intensity decreases with respect to the intensity change between the lattices,
A plurality of element gratings may be arranged such that the intensity decreases in several steps between the intensity of 100% and 0%. At this time, it is necessary that the width in the direction in which the strength increases and the width in the direction in which the strength decreases are different.

The waveform 14 in FIG. 1B represents the light transmission intensity of the grating shown in FIG.
It changes stepwise in 20% steps up to 00%, and its average intensity changes like a triangular wave. At this time, the light transmission intensity need not be in the range of 0 to 100%, but may be changed in any intermediate intensity range. When the width h of the element grating is 10 μm, the length of one pitch of the grating is 60 μm. In a conventional grating having a binary intensity, one pitch of the grating is 20 μm when the black grating width is 10 μm. The multi-valued grating of the present example has a longer grating pitch than the conventional binary grating, and the intensity during that period discretely changes in several steps. Therefore, the influence of diffraction is smaller than that of the conventional grating. Further, in the case of the conventional binary grating, the intensity distribution is symmetric in the direction in which the grating is formed. However, the multivalued grating of the present invention has an asymmetric intensity distribution, and has various advantages described later.

A method for creating a multi-value grid will be described. A photosensitive material is applied to a glass substrate of the optical scale 10 and is set on a pulse stage. The glass substrate is irradiated with light from a semiconductor laser, and the pulse stage is moved at a constant speed at a constant distance. The semiconductor laser can perform light intensity modulation such that the light intensity output by controlling the drive current can be varied. Therefore, when the semiconductor laser irradiates a light intensity corresponding to the light transmission intensity of each element grating from the semiconductor laser, the element grating is exposed according to the irradiation intensity and element gratings having different light transmission intensities are created.

FIG. 2 shows an example of a light intensity waveform detected when the optical scale 10 is illuminated. When the light intensity of transmitted light or reflected light is detected by the light receiver while the optical scale 10 is moving, a slit having a width equal to or slightly larger than h with respect to the width h of the element grating is formed in the light receiver. And the light intensity is detected through a slit. In this case, when the optical scale 10 moves, a triangular light intensity whose intensity changes linearly like a waveform 21 is detected. A waveform 22 indicated by a dotted line for comparison is the same as the waveform 14 in FIG.

If the slit attached to the photodetector has a positional relationship overlapping the respective element gratings (the center of the slit coincides with the center of the element grating), the light intensity corresponding to the light transmission intensity of the element grating is detected. You. If the slit is located over the two element gratings, the positional relationship between the two element gratings with respect to the slit and the light intensity corresponding to the light transmission intensity of the element grating are detected. For example, an intermediate light intensity between the two element gratings at the position 23 is obtained when the slit center is located at the boundary position between adjacent element gratings. As described above, the light intensity that changes discretely is converted into the light intensity that changes linearly into a triangular wave by the masking effect of the slit and the effect of the small influence of the diffraction spread.

FIG. 3 shows a configuration example of a dimension measuring apparatus according to the present invention. The illumination light source 30 is composed of a light emitting diode or the like, and
To illuminate. The optical scale 10 has a structure shown in FIG. 1A and is moved in the left-right direction in the figure according to the movement of the stylus, not shown in the figure. Although the light applied to the optical scale 10 is transmitted or reflected, this example shows an example of detecting the light transmitted through the optical scale 10. The light receiver 32 has a single light receiving surface and is installed near the optical scale 10. The light transmitted through the optical slit 10 is a spread spot, and the light transmitted through many element gratings is mixed. Therefore, for the width h of the element grid, it is equal to h,
Alternatively, a slit 320 having a width slightly larger than h is attached to the light receiving surface of the light receiver 32, the transmitted light intensity from the optical scale 10 is detected through the slit, and one light intensity signal 33 is emitted. Note that a lens for magnifying an image may be placed between the optical scale 10 and the light receiver 32. In this case, when the magnification of the image enlargement is m, a slit having a width of mh may be attached to the light receiving surface of the light receiver 32.

For the dimension measurement, it is necessary to detect in which direction the stylus is moving. The moving direction determination unit 34 detects which direction the optical scale 10 is moving, left or right, from the change in the light intensity of the light intensity signal 33. When the grid is moving, the waveform 21 changing in a triangular waveform shown in FIG. 2 is detected. When the optical scale 10 having the configuration shown in FIG. 1A moves to the right, the light intensity changes from large to small, and when moved to the left, the light intensity changes from small to large. Therefore, if the direction in which the light intensity changes when the optical scale 10 moves is detected, the optical scale 10
Can be detected. At this time, depending on the configuration of the multilevel grating, the width of the light intensity change may be detected together with the direction of the light intensity change.

According to this method, the moving direction can be detected by only one light intensity signal, and the determination can be made more easily than in the conventional method of detecting the phase advance / delay using two slits. Further, since it is only necessary to place the light receiver 32 in a region where the intensity of the irradiation spot is high, complicated adjustment is not required for installation. These advantages arise because the light transmission intensity of the grating has a linear and asymmetric intensity distribution.

When measuring dimensions, there are two modes: measurement when the stylus is moving, and measurement when the stylus is stopped. FIG. 4 shows a waveform example of a light intensity signal detected by the optical scale 10 as an aid for explaining the following dimension measurement method. The waveform 41 is a light intensity signal detected over the entire measurement, the light intensity Va at the point 42 is the intensity detected at the start of the measurement, and the light intensity Vb at the point 43 is the intensity detected at the end of the measurement. Is detected when is stopped. While the optical scale 10 is moving, a light intensity that changes in a triangular waveform is detected. At this time, since the moving speed is different, the cycle of the signal 41 is different. Waveform 4
Reference numeral 4 denotes a pulse signal obtained by a circuit that generates a pulse when the triangular wave signal intensity changes from the H level to the L level.
If the distance La between the point 42 and the first pulse 45, the distance Lb between the last pulse 46 and the point 43, and the moving distance Np based on the total number of pulses between the pulses 45 and 46 are known,
The movement distance of the grating, that is, the dimension, can be measured.

The grating movement counting section 35 shown in FIG. 3 detects the number N of movement pulses of the grating when the optical scale 10 is moving. In the example of FIG. 4, the number of pulses between the first pulse 45 and the last pulse 46 is detected. At this time, Np, which is a multiple of p in units of the length p of one pitch of the grating, is detected. The grid movement counting unit 35 outputs integer dimension information 350.

Next, the measurement operation when the optical scale 10 is stopped will be described. In order to measure the dimensions with high accuracy, it is necessary to divide one period of the grating and detect the stop position of the grating with a position detection accuracy smaller than the width h of the element grating. The grid position detector 36 detects a grid position at the start of measurement and a grid position at the time of stop after the optical scale 10 has moved. As apparent from the waveform 21 in FIG. 2, the light intensity detected by the light receiver is determined according to the position of the element grating immediately before the slit of the light receiver 32 and the light transmission intensity thereof. Therefore, by detecting the light intensity, it can be determined from which element grating the light is being detected. In the example of FIG. 4, which element grid intensity is determined from the light intensity Va at the point 42 and the light intensity Vb at the point 43, the distances La and Lb are obtained.

In order to detect the position of the element grating from the light intensity, it is necessary to detect the maximum and minimum intensities (peak intensities) of the waveform 41 in FIG. Therefore,
While the optical scale 10 is moving, the grid movement counting unit 35 detects the maximum and minimum intensity of the triangular wave signal in addition to counting the number of moving grids. Maximum strength Vm,
In the case of the minimum intensity Vn, the distance La = p × (Vm−V) between the stop position of the grating in FIG. 4 and the element grating having the maximum light transmission intensity.
a) / (Vm−Vn), the distance Lb = p × (Vb−Vn) / between the element grating having the minimum light transmission intensity and the stopping position of the grating
(Vm-Vn). As described above, the element grating position can be determined directly from the light intensity because the light intensity changes linearly within one period of the grating. p is the length of one pitch of the grating, and the dimensions La and Lb are the length p of one pitch of the grating.
It is a smaller value. In the detection of the distance La, the initial light intensity Va detected before the movement of the grating is analogized,
Alternatively, it is stored digitally, and the position is detected after the grid movement is stopped. The lattice position detector 36 outputs lattice position information 360 before the start of the movement and lattice position information 365 at the end of the movement of the lattice.

In detecting the grid position while the optical scale 10 is stopped, two positions correspond to the detected light intensity. The position in the direction in which the light transmission intensity of the element grating is increasing and the position in the direction in which the light intensity is decreasing need to be detected separately. Since it is difficult to distinguish between the two while the optical scale 10 is stopped, the position is distinguished from the light intensity information while the optical scale 10 is moving. Therefore, in addition to counting the number of pulses and detecting the maximum and minimum intensities as described above, the grating movement counting unit 35 also detects the direction in which the light intensity changes at certain time intervals (differential detection of the change). That is, the detection of the direction of increase or decrease in the light intensity immediately after the movement of the grating and immediately before the stop is detected, and the position of the element grating at the time of stopping the grating is distinguished and determined.

The dimension calculation unit 37 calculates the grid movement distance Np based on the signal 350 and the grid position information La before the grid movement based on the signal 360 and the grid position information Lb after the grid movement based on the signal 365 based on three types of position information. Calculate the dimensions of the measured object. This dimensional value is measured with a dimensional sensitivity equal to or less than the width of the element grating. If the light intensity is detected by an A / D converter having a resolution of 8 bits, one period of the grating can be detected by dividing it into 200 periods. Possible, the length of one pitch of the grating is 100μ
In the case of m, it can be measured with a resolution of 0.5 μm. Also, 1
With 0-bit A / D detection, measurement with a resolution of 0.1 μm is possible, and dimensions can be measured with higher precision than with a conventional binary grating.

The above description is an example in which a triangular wave signal can be obtained directly from the light intensity signal transmitted through the optical scale.
At this time, it is conceivable that the triangular wave signal is distorted due to various kinds of noise or the like. In this measurement, since the linearity of the triangular wave signal is important, the detected light intensity signal may be corrected by a circuit means such as a low frequency filter.

[0031]

As described above, the dimension measuring apparatus according to the present invention uses an optical scale on which a grating composed of multiple intensity levels is formed, and has an asymmetric intensity distribution in the direction in which the grating is formed. Due to the effects of the multi-valued intensity and the asymmetric intensity distribution, when the optical scale is moving, the light intensity that changes linearly is detected, and there is an asymmetric time change in the direction in which the light intensity increases and in the direction in which the light intensity decreases. The moving direction of the grating can be directly detected from the light intensity. Therefore, the light intensity from the optical scale can be detected by a light receiver having a single light receiving surface, and only one light intensity signal needs to be output. As a result, two slits for moving direction determination are unnecessary, and the circuit configuration is simpler than the conventional method of comparing the phases of two signals, and the moving direction can be determined with a simple configuration. In addition, there is little restriction on the positional relationship between the light receiver and the optical scale, and complicated position adjustment is not required.

In the detection of the light intensity during the movement of the optical scale and during the stop, a slit having a width substantially equal to the width of the element grating is attached to the light receiver, and the light intensity is detected through the slit. Therefore, the light intensity from each element grating can be independently detected, and particularly when the optical scale is stopped, the element grating position can be directly detected from the value of the light intensity by one signal. At this time, the positional relationship between the slit and two adjacent element gratings facing the slit can be detected with a position resolution smaller than the width of the element grating from the value of the light intensity changing in a triangular waveform. As a result, compared to the conventional detection of the phase of the sine wave intensity using two signals, the resolution of the grid position detection is higher, and the grid position can be detected, that is, the dimensions can be measured with high accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of an optical scale having a multi-value intensity grating used in a dimension measuring device according to the present invention.

FIG. 2 is a diagram showing an example of a light intensity signal detected using the optical scale of the present invention.

FIG. 3 is a system block diagram illustrating a configuration example of a dimension measuring device using an optical scale according to the present invention.

FIG. 4 is a diagram illustrating an example of a light intensity signal detected when the optical scale of the present invention moves.

FIG. 5 is a diagram showing a configuration example of a conventional dimension measuring device using an optical scale.

FIG. 6 is a diagram illustrating an example of a light intensity signal detected using a conventional optical scale.

[Explanation of symbols]

 Reference Signs List 10 optical scale 11 element grating 32 light receiver 34 moving direction judging unit 35 grating movement counting unit 36 grating position detecting unit 37 dimension calculating unit

Claims (3)

[Claims] 1. A dimensional measurement using an optical scale that illuminates an optical scale on which a grating of a predetermined shape is formed with light from a light source, detects a light intensity change caused by movement of the optical scale, and measures dimensions. An apparatus, wherein a plurality of gratings each including n element gratings are formed in units of one element grating having a predetermined light transmission intensity and a constant width, and the n
An optical scale in which the element gratings have n types of different light transmission intensities, a light receiver for detecting the transmitted light intensity or reflected light intensity of light illuminating the optical scale and outputting a light intensity signal, and the optical scale A moving direction determining unit for inputting a light intensity signal from the light receiver when the light is moving, detecting a direction in which the intensity of the light intensity signal increases or decreases, and detecting a moving direction of the optical scale; A grid movement counting unit for detecting the number of pulses of the light intensity signal generated by the movement of the scale and the maximum intensity and the minimum intensity of the light intensity signal, and before and after the movement of the optical scale when the optical scale is stopped. From the light intensity detected by the light receiver and the maximum intensity and the minimum intensity, the position at which the grating stops is the intensity of the light transmission intensity of the two adjacent element gratings. The grid position detection unit that detects with a position detection accuracy smaller than the width of the element grid from the relationship, the movement distance information corresponding to the number of grid movements detected by the grid movement count unit, and the grid position detection unit detects A dimension calculation unit that calculates a dimension value to be measured from the position information of the grating before and after the movement of the optical scale, and detects a light intensity change caused by the movement of the optical scale to measure the dimension. Dimension measuring device using optical scale. 2. The optical scale according to claim 1, wherein the light transmission intensity of the element grating is changed in steps of n steps at equal intervals, and one period of one grating formed by collecting n element gratings Characterized in that the intensity distribution is a triangular wave shape and the intensity distribution is asymmetric with respect to the direction in which the grating is formed. 3. The light receiver according to claim 1, wherein the light receiver has a single light receiving surface, and the light receiving surface has a slit having a width substantially equal to a width of each element grating forming the grating. Mounting, detecting a light intensity from the optical scale transmitted through the slit, outputting one light intensity signal, and measuring a size from the intensity of the light intensity signal; apparatus.