JPS6095316A - Displacement measuring method - Google Patents

Abstract

PURPOSE:To simplify measurement, and also to raise its accuracy by placing in parallel a substrate which has arranged an element to a position for dividing a part between gauge marks into (n) equal parts, and a moving plate which has arranged an element to a position for dividing a part between the gauge marks into (n)+ or -(m) equal parts by using a specified real number (m). CONSTITUTION:A part between gauge marks on a substrate 10 is divided into (n) equal parts by an optional integer (n) and an optical sensor 11 functioning as an element is arranged, and a part between gauge marks of the same distance of the part between said gauge marks on a moving plate 20 is divided into (n)+ or -(m) equal parts by using (m) which is a real number smaller enough than (n) except an integer, and a small hole functioning as an element is provided. Subsequently, uniform light is irradiated from the upper face side of the plate 20 and photodetected by the sensor 11 through a small hole 21, and a large variation in phase of a wave of an arrangement order successive variation of outputs of the sensor 11 is measured by fixing the plate 10 and moving minutely the plate 20.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a displacement measuring method suitable for measuring minute displacements.

(b) Prior Art Conventionally, various methods such as the Moiré fringe method and laser interferometry have been proposed and implemented as methods for measuring minute displacements such as stress strain.

By the way, the present inventor has proposed a new method for measuring minute displacements in Japanese Patent Application No. 163575/1983. In other words, the above-mentioned proposal is based on a board with elements A arranged at positions that divide the distance between the gauge points into n equal parts (n is an arbitrary integer), and a board on which the elements A are arranged at positions that divide the distance between the gauge points into n+m equal parts (m is an arbitrary integer). A movable plate on which elements B are arranged is placed in parallel to the position where elements A and B are arranged (an integer sufficiently smaller than n).

A displacement measuring method characterized by determining the phase of a wave of a sequential change in the arrangement order of the amount of information that occurs in element A or element B due to the action, and measuring the relative displacement between the substrate and the moving plate from the change in phase. It is.

As a result of subsequent intensive studies, we came to find more favorable conditions for implementing the invention, in addition to the condition rn+m equal division (m is an integer sufficiently smaller than n) j, which determines the arrangement position of element B on the moving plate. .

(C) Purpose The present invention is a novel displacement measuring method for measuring minute displacements as described above, which can be performed relatively easily.
Furthermore, it is an object of the present invention to provide a displacement measuring method that can measure minute displacements with high precision.

(D) Configuration The displacement measuring method according to the present invention includes a substrate on which elements A are arranged at positions dividing the distance between the gauge points into n equal parts (n is an arbitrary integer), and a distance between the gauge points having the same distance as between the gauge points. A movable plate with elements B arranged in positions that are divided into n±m equal parts (where m is an arbitrary real number sufficiently smaller than n to divide an integer) is placed in parallel, and the interaction between elements A and B causes the elements to It is characterized in that the phase of the wave of the sequential change in the arrangement order of the amount of information occurring in A or B is determined, and the relative displacement between the substrate and the moving plate is measured from the change in the phase.

(e) Embodiment FIG. 1 is a perspective view schematically showing an embodiment of the substrate and moving plate used in the displacement measuring method according to the present invention, and FIG. 2 is an operation waveform diagram of the embodiment shown in FIG. 1. It is.

In FIG. 1, 10 is a substrate on which, for example, 250 photosensors 11 as elements A are arranged at equal intervals between the gauge points of 25 fins, and 20 is a substrate with the same distance between the gauge points arranged by the optical sensors 11. For example, 250.3128 as element B between gauge points
This is a moving plate with nine small holes 21 arranged at equal intervals. The elements A and B are formed by a so-called photolithography method. Each photomask is created using the same original plate for photolithography. The photomask forming element B is created with a slightly smaller optical reduction ratio than the photomask forming element A. The number of elements B provided between the gauge points mentioned above, 250.31289, is not the result of optical reduction aimed at this value, but as a result of slight optical reduction, the number of elements B is 250.31289. It has become.

The substrate 10 is fixedly provided, while the movable plate 2o is attached to a movable body (not shown).

Then, when uniform light is irradiated from the upper surface side of the moving plate 20, each sensor 11 of the substrate tFiIO receives the light through the small hole 21 of the moving plate 20. As a result, the sequential change in the arrangement order of the optical sensors 11 arranged on the substrate 1o changes as shown by the black circles in FIG.

Next, move the moving plate 20 along the direction in which the small holes 21 are arranged.
When the substrate 1o is moved slightly, the amount of light received by the optical sensor 11 of the substrate 1o changes, and the wave becomes, for example, as shown by the white circle in FIG. That is, as is clear from the figure, the moving plate 20
A slight change in the output of the optical sensor 11 causes a large change in the phase of the wave of the sequential change in the arrangement order of the output of the optical sensor 11.

Furthermore, the phase of the wave of the sequential change in the arrangement order of the optical sensors 11 is
By statistically processing the output of each optical sensor 11 and determining its maximum likelihood position, the accuracy of displacement measurement can be further improved.

FIG. 3 is an explanatory diagram showing a method of determining the maximum likelihood position of the wave phase. That is, a pattern (for example, the waveform shown by a chain line in FIG. 3) that most likely shows a sequential change in the arrangement order of the optical sensors 11 is prepared in advance. Then, if the wave of the sequential change in the arrangement order of the optical sensors 11 whose phase is to be measured is adapted to the predetermined pattern, the wave shape between the optical sensors 11 and the correct wave shape can be specified. For example, even if the peak of a wave appears between optical sensor arrays i and i+l (i is an integer), the position where the peak appears can be determined by adapting the predetermined pattern indicated by the chain line. can be calculated with an accuracy of 1/1o or more of the optical sensor 11.

Furthermore, by statistically processing the output of the optical sensor 11 as described above, it is possible to find out that, for example, as shown in FIG. Since the normal value can be estimated even if it is larger than the normal value, errors in the calculated phase value based on mechanical errors can be reduced.

The displacement reading accuracy will be explained below using specific numerical examples.

The distance between gauges is 25, m = 0.31289, n = 250 optical sensors 11 on the substrate 10, 25 on the moving plate 20
When the small hole 21 of 0.31289 is provided, the wave phase movement is magnified 800 times since the magnification rate of the displacement of the moving plate 20 is expressed as (n 10 m)/m. Moreover, since the accurate position of the phase on the substrate 1o can be determined statistically from the outputs of the 250 optical sensors 11, 25 fl/
(250xlO) or higher accuracy. Therefore, the substrate 10
As can be seen from 5, the relative displacement of the movable plate 20 can be obtained with an accuracy of 0.0125 μm or more.

Moreover, according to the above-mentioned embodiment, even if there is an error in the pinch of the original plates forming the photomasks of elements A and B, the error is canceled out as long as the displacement is measured within one pitch of the array. . This is because elements A and B are formed from the same original plate by optical reduction, etc., and errors in the original plate appear on the photomask of the pixel element, causing the optical sensor 11
This is because the error does not affect the phase change of the output wave.

Moreover, if the coefficients of thermal expansion of the substrate 10 and the moving plate 20 are made equal, errors in measuring displacement due to temperature changes can be reduced, and therefore accuracy can be further improved.

Furthermore, sequential changes in the amount of information of elements such as optical sensors in the order of arrangement can be achieved by statistical processing of the information amount of each element and, for example, by using a regression line. Data processing can compensate for variations in sensitivity of each element.

In the embodiment, the elements A arranged on the substrate are optical sensors, and the elements B arranged on the movable plate are small holes, but the present invention is not limited to this. For example, forming electrodes as element A and element B,
It may be possible to measure the capacitance between these.

In addition, element A is a magnetic sensor such as a Hall element, and element B is a magnetic sensor such as a Hall element.
The same effects as those described in the embodiments can be obtained even if the polarity is N-pole or S-pole. As described above, the elements A and B used in the present invention may be a combination of elements that interact with each other, and therefore various modifications can be made.

In addition, in the example, the difference m between the number of optical sensors and small holes is 0.
．． 31289. However, the present invention is not limited thereto, and m can take any real number other than an integer. The magnification of displacement measurement can be changed depending on the value of m.

(f) Effects Since the present invention is constructed as described above, minute displacements of a moving body can be measured relatively easily and with high accuracy.

In addition, since m, which is the difference in the number of elements A and B provided between the gauge points, can take any real number, it is easy to form the elements, and the manufacturing cost of the device using this method is reduced.
It is something that can be done.

[Brief explanation of the drawing]

FIG. 1 is a perspective view schematically showing an embodiment of the substrate and moving plate used in the displacement measuring method according to the present invention, FIG. 2 is an operation waveform diagram of the embodiment shown in FIG. 1, and FIG. FIG. 3 is an explanatory diagram showing a method of determining the maximum likelihood position of the phase of a wave. DESCRIPTION OF SYMBOLS 10... Substrate, 11... Optical sensor, 20... Moving plate, 21... Small hole. Patent applicant Shimadzu Corporation Representative Patent attorney Takaharu Ohnishi Figure 3 i-3i-2i-1i i+1 i+2 i+3 i+4

Claims (4)

[Claims] (1) A board with elements A arranged at positions that divide the distance between the gauge points into n equal parts (n is an arbitrary integer), and divide the distance between the gauge points with the same distance as the distance between the gauge points into n + m equal parts (m is sufficiently smaller than n). A movable plate on which elements B are arranged at positions of arbitrary real numbers (excluding integers) is arranged in parallel, and the amount of information generated in elements A or B due to the interaction between elements A and B changes sequentially in the arrangement order. A displacement measuring method comprising: determining the phase of the wave, and measuring the relative displacement between the substrate and the moving plate based on the change in the phase. (2) The phase of the wave of the sequential change in the arrangement order of the amount of information is such that its maximum likelihood position can be determined by statistical processing of the amount of information of the element. Displacement measurement method described. (3) The displacement measuring method according to claim 1, wherein the element A is an optical sensor and the element B is a small hole. (4) The displacement measuring method according to claim 1, wherein the element A and the element B are formed using photomasks made from the same original plate for photolithography. .