JPS60107518A - Optical scale - Google Patents

Abstract

PURPOSE:To improve precision by slanting photoelectric converting elements which are arrayed in a line corresponding to a scale grating or photodetection part slightly to its moving direction, and interpolating scale grating intervals in the moving direction with signals of photoelectric converting elements perpendicular to the intervals. CONSTITUTION:Numbers of scale gratings 5 made of opaque materials are arrayed on a glass substrate 4 at equal intervals perpendicularly to a moving direction shown by an arrow A in the moving direction. Further, a line sensor 6 is provided facing a projection lens and numbers of photoelectric converting elements S1-Sn are arrayed thereupon at a fine angle to the lengthwise direction of the unit scale gratings. Outputs of the respective elements S1-Sn are supplied to (n) counters of the 1st counter 7 and the output of the basic element S1 is added by a main counter 8. When a moving body starts moving, the position of the element outputted by the 1st counter 7 varies, and this variation is compared by a comparator 11 with the position signal of the 2nd counter 10 before the movement to decide on the direction and also output it.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical scale for measuring the moving distance of a moving body, the length of an object, an angle, etc. The present invention relates to an optical scale having a line sensor consisting of a large number of graduation gratings and a large number of photoelectric conversion elements arranged at an angle with respect to the gratings.

In conventional optical scales, the graduation grating is carved perpendicular to the direction of movement, and between the gratings, the signal from the light receiving section is divided into several sets and captured, and the signal strength of each phase is converted into an electrical signal that approximates a sine wave. However, this is electrically divided to detect the position between the grids. Therefore, the division accuracy is poor due to the S/N ratio relationship and waveform distortion from the sine wave, and
Satisfactory accuracy could not be obtained, such as inability to divide into micrometers or less.

Based on the above facts, it is an object of the present invention to provide an optical scale that can accurately detect the position between gratings. In accordance with this objective, the optical scale of the present invention tilts the photoelectric conversion elements arranged in a line, which correspond to the graduation grating or the light receiving part, at a small angle with respect to the moving direction, so that the interval between the graduation gratings in the moving direction can be changed to the photoelectric conversion elements in the direction perpendicular to the moving direction. This method is characterized by interpolation using conversion element signals.

The following will be explained with reference to the drawings. In FIG. 1, 1 is a light source, 2 is an illumination lens, 6 is a projection lens, and the illumination lens 2
A glass substrate 4 fixed to a moving body (not shown) is interposed between the projection lens 6 and the projection lens 6 . As shown in FIG. 2, for example, on the glass substrate 4, a large number of scale gratings 5 made of an opaque material are arranged at equal intervals along the direction of movement, perpendicular to the direction of movement indicated by arrow A. Furthermore, a line sensor 6 is provided opposite the projection lens.

The line sensor has a large number (for example, 1000) of photoelectric conversion elements S1...5n arranged at a slight angle (α) with respect to the longitudinal direction of a unit scale grating. The arrangement relationship between the scale grating and the line sensor is not limited to that shown in FIG. 2, but may be arranged such that the line sensor 6 is perpendicular to the moving direction and the scale grating 5 is inclined to the moving direction, as shown in FIG. . Then, as shown in FIG. 4, the lower end element S
, when facing the lower end of one of the gratings 5a, the upper end element S
n is arranged at a relative position such that it faces the upper end of the adjacent grid 5b.

As shown in FIG. 5, each element S1 of the line sensor 6...
...The output of Sn is given to each of the n counters provided in the first counter 7, and the output of the basic element S1 is given to the main counter 8 consisting of an anog down counter, and the output numbers are added up. It looks like this.

Each photoelectric conversion element outputs an output according to changes caused by light shielding by the scale grating 5, and the start signal ST is output from the line sensor 6.
, the first counter 7, the second counter 10, and the main counter 8, and when the clock pulse CL is given to the line sensor 6 and the first counter 7, the elements S1...Sn change the scale grating in synchronization with the clock pulse. Output according to the shading of. For example, in FIG. 2, if elements S2, S3, and S4 output, the first counter 7 counts the number of output signals of each, detects the central element S4, and sends the number to the second counter 1D. to be memorized.

Incidentally, when there is an output from both elements S1 and S as shown in FIG. 4, it is determined that there is a lattice on S.

Next, when the moving object starts moving, the position of the element output by the first counter 7 changes. When the scale grating 5 moves to the left in FIG. 2, the output of the element changes toward the upper side. This change is compared with the position signal from the second counter 1o before the movement in the comparator 11, and movement in the positive direction is determined and outputted. Of course, if it moves in the opposite direction, a negative direction signal will be output. The positive/negative discrimination signal of the comparator 11 is sent to the main counter 8, and the output numbers of the elements S and G are added in the positive or negative direction to calculate the number of elements passing through the scale grating 50. As a result, the distance according to the grid 5 due to the movement of the moving object is calculated. Furthermore, when the line sensor stops at a position where the scale grid intersects, the first counter 7 detects and outputs the output of the photoelectric conversion element S1 at that position, and provides it to the arithmetic circuit 12.

In the arithmetic circuit, when the distance of the element SI from the reference element S1 is L, L x sin α is calculated to calculate the length of the intermediate position. The total moving distance is calculated by adding the total number of reference elements S1 to the intermediate position length, and the signal is sent to the display device 16 to display the distance.

As is clear from the above, according to the present invention, the line sensor and the scale grating are relatively inclined, and the position between the gratings can be calculated accurately, and highly accurate position detection can be performed. Can be done.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a part of the apparatus according to the present invention, FIGS. 2 to 4 are views showing the arrangement relationship between a line sensor and a scale grating, and FIG. 5 is a block diagram of a position detection circuit. 1... Light source, 2... Lighting lens, 6
...projection lens, 4...glass substrate, 5.
...Graduation grid, 5a, 5b...Grid,
6... Line sensor, 7... First counter, 8... Main counter, 10... Second
Counter, 11... Comparator, 12... Arithmetic circuit, 13... Display device.

Claims (1)

[Claims] a line sensor comprising a large number of scale gratings arranged in a direction along and intersecting the moving direction of the moving body, and a large number of photoelectric conversion elements arranged on lines intersecting the scale gratings at an angle; A light source device that emits light to the line sensor through the scale grid, a circuit that counts the number of scale grids by counting the output of each photoelectric conversion element during movement, and a circuit that measures the intersection of the line sensor and the scale grid when stopped. An optical scale consisting of an arithmetic circuit that calculates position.