JPS6236517A - Detecting system for two-dimensional digital displacement - Google Patents

Abstract

PURPOSE:To equalize errors in the directions X and Y and thereby to enable the removal of the errors by a method wherein a pattern on an optical mask disposed opposite to an image line sensor is formed of wedges each having a rectangular end and being arranged alternately in a straight line. CONSTITUTION:A pattern, which is formed on an optical mask 51, is formed of wedges 51a and 51b having each of end of an angle of 90 deg. and being combined with each other. These wedges 51a and 51b are paired with the respective ends directed inversely to each other and a number of pairs thereof are arranged in a straight line, while the straight line formed thereby is made parallel to an element arrangement line 2a of an image line sensor 2. A light form an illuminating device is applied onto the image line sensor 2 through each of the patterns 51a and 51b of the optical mask 51. Since output errors of the image line sensor 2 in the directions of X and Y become equal according to this constitution, the errors can be removed by a simple arithmetic means.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a two-dimensional digital displacement detection method using an image line sensor.

[Prior art]

Conventionally, in a two-dimensional digital displacement detection device using an image line sensor, as shown in FIGS. 4 and 5, a sawtooth pattern 1a formed from mutually orthogonal straight lines formed on an optical mask 1 is used. Projected onto the image line sensor 2, the displacement in the X direction is calculated from the change in the total width of the projected bright area (or dark area), and the displacement in the Y direction is calculated from the displacement of the entire bright area (or dark area) from the virtual reference line. Detected.

The reason for arranging a large number of patterns la in a sawtooth pattern is to average the amount of change for each pattern 1a and improve the resolution.

In addition, in FIG. 4, 2a is the image line sensor 2.
Further, in FIG. 5, reference numeral 3 denotes a light source for projecting the pattern 1a onto the element array line 2a of the image line sensor 2.

FIG. 6 is a diagram showing in detail the relationship between the sawtooth pattern 1a of the optical mask and the element array line 2a of the image line sensor 2 with respect to the displacement in the X and Y directions of the two-dimensional digital displacement detection device. In the figure, 31 is a virtual reference line, which is virtualized by a circuit that processes an output signal of an image line sensor (not shown).

The signal processing is performed using the virtual reference line 31 of the first four parts (or dark part) as a reference and the amount of change ΔAi of the width Ai and Bi = Ai,
-Ai.

ΔBi=Bi+−Bi.

...(1) is obtained, and from this, X = 1/2 nΣ(LI+1 to AAi+8Bi This is done by calculating the total number of patterns 1a).

Here, ΔAi, ΔB are directly expressed without going through the process of equation (1).
A method for obtaining i may be adopted.

[Problem that the invention seeks to solve]

However, when a sawtooth pattern is used as in the conventional example above, the output of the image line sensor, which discriminates between brightness and darkness, fluctuates due to changes in the temperature characteristics of the image line sensor, the amount of irradiated light, etc., resulting in errors in the final displacement detection signal. There was a drawback that caused

Errors due to such fluctuations are not shown in FIG.

Since the widths Ai and Bi are homeomorphic as β, the widths Ai,
It is noticeable in the X direction, where the change is obtained from the sum of Bi, and is almost not observed in the Y direction, where the displacement is obtained from the difference.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a two-dimensional digital displacement detection method that eliminates the error that occurs in the detection signal in the X direction as in the prior art.

[Failure to solve the problem]

In order to solve the above-mentioned problems, the present invention has a pattern formed on an optical mask by forming a pair of wedge shapes whose tips have an angle of 90 degrees and reversing the directions of the tips, and forming a pair of wedge-shaped patterns formed on an optical mask. The pattern was arranged in a shape such that the straight lines of the pattern were parallel to the element array line of the image line sensor, and were projected onto the image line sensor.

[Effect]

By configuring as described above, the error caused by changes in sensitivity due to various factors of the image line sensor is the same in both the X and Y directions, so it is possible to It becomes possible to cancel the error by a calculation means.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a diagram showing the basic configuration of a two-dimensional digital displacement detection device according to the present invention. The basic configuration of the two-dimensional digital displacement detection device is the same as that shown in FIGS. 4 and 5, but the optical mask 51 has wedge-shaped patterns 51a and 51b whose tips have an angle of 90 degrees as shown in the figure. The directions of the tips are reversed to form a pair of patterns, and a large number of pairs of patterns are arranged in a straight line to form a pattern. Note that the size of each pattern 51a, 51b and the interval between the patterns are appropriately manufactured so as to guarantee the maximum measured value.

FIG. 2 shows the above two-dimensional digital displacement detection device.
A pair of patterns 51a and 51 for displacement in the X and Y directions
FIG. 3 is a diagram showing the relationship between the element array line 2a of the image line sensor and the element array line 2a of the image line sensor. In the figure, 31a and 31b are the same as the virtual lines 31 in FIG. 6, and each pattern 51
a, 51b. In the signal processing, for the pattern 51a of the i-th pattern pair, ΔAi and ΔBi are obtained by processing similar to the above equation (1), and in the same way, for the pattern 51b, the virtual reference line 31b is obtained. Amount of change in the widths Ci and Di with reference to ΔC1=C4+−Ci.

ΔDi=Di+−Di.

...(3) get.

Furthermore, from the changes ΔAi, ΔBi, ΔCi, and ΔDi, Y = 1/4N Σ ((ΔAi−ΔBi)+(Δ
(to Ci-8Di) i=1 (4) (N is the logarithm of the arranged pattern).

Here, the changes ΔAt, ΔBi, ΔCi, and ΔDi may be directly counted without going through the process of equation (3) above.

Using such patterns 51a and 51b, X and Y
When detecting By performing a differential process on each calculation of X and Y, it becomes possible to cancel each other out.

According to the above embodiment, as shown in FIG. 1, the wedge-shaped pattern 51a has a tip having an angle of 90 degrees.

By using an arrangement of many pairs of patterns of 51b with the directions of their tips reversed, and performing calculations through the differential process shown in equation (4) above, various factors of the image line sensor can be determined. The error caused by the change in sensitivity is the same in both the X and Y directions and is extremely large.
It becomes possible to make it small.

〔Effect of the invention〕

As described above, according to the present invention, the pattern of the optical mask is formed by forming a pair of wedge-shaped tips having a 90-degree angle and reversing the directions of the tips, and arranging the pairs in a linear manner. Because of the shape, errors caused by changes in sensitivity due to various factors of the image line sensor are the same in both the X and Y directions, and can be made extremely flexible. Therefore, if the present invention is applied to various measuring instruments such as two-dimensional vibrometers and two-dimensional positioners that require a displacement detection function, extremely excellent effects will be exhibited.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the basic configuration of a two-dimensional digital displacement detection device according to the present invention, and FIG. 2 is a diagram showing a pair of patterns and image line sensor elements for displacement in the X and Y directions in the two-dimensional digital displacement detection device. Figure 3 shows the shift of the bright/dark detection boundary due to changes in the sensitivity of the image line sensor, etc. Figures 4 and 5 show the basic configuration of a conventional two-dimensional digital displacement detection device. 6 and 7 are diagrams showing the relationship between the sawtooth pattern of the optical mask, the image line sensor, and the two-element array line with respect to displacement in the X and Y directions of a conventional two-dimensional digital displacement detection device. . In the figure, 2... image line sensor, 51...
Optical mask, 51a, 51b...pattern.

Claims (1)

[Claims] A two-dimensional digital displacement detection device comprising an image line sensor, an optical mask, and illumination means for projecting a pattern formed on the optical mask onto the image line sensor. A pair of wedges whose tips have an angle of 90 degrees are made by reversing the directions of the tips, and many pairs are arranged in a straight line, and the straight line of the pattern is the element array line of the image line sensor. A two-dimensional digital displacement detection method characterized by detecting displacement in X and Y directions orthogonal to each other based on brightness and darkness projected onto an image line sensor arranged parallel to the image line sensor.