JPH03185312A - Linear scale - Google Patents

Abstract

PURPOSE:To enable execution of highly precise measurement, to facilitate preparation of a long scale and to reduce the cost thereof by using a one-dimensional light sensor as a reading means and by making the intervals of the marks narrower than the width of a visual field of the one-dimensional light sensor. CONSTITUTION:A movable plate 1 provided with a scale 3, a one-dimensional light sensor 2 for reading the scale 3, a device for moving the movable plate 1 and a signal processing device for determining the distance of movement of the movable plate 1 from an output of the one-dimensional light sensor 2 are equipped, and the one-dimensional sensor 2 is fixed on a stage. The scale 3 on the movable plate 1 is so provided that the intervals l of the marks 3 are smaller than the width L of the one-dimensional sensor 2. For this one- dimensional light sensor 2, a sensor having about 5,000 pixels and available on the market can be used. As the movable plate 1 moves rightward, for instance, the output of the one-dimensional sensor 2 varies from the pixel on the left side to that on the right side, and therefore the distance of movement of the moving plate 1 can be determined from this variation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a linear scale for measuring the linear movement distance of a movable member.

[Prior Art] Conventionally, this type of linear scale has a scale 1 provided at predetermined intervals on one of a movable member and a fixed member, for example, black and white stripes, a magnetic signal, etc., and an optical scale provided on the other. Or detected by a magnetic sensor.

The distance traveled is measured by counting the number of tick marks.

For example, when black and white stripes shown in FIG. 6(a) are used as graduations in a conventional linear scale.

The optical sensor outputs an output signal as shown in FIG. 6(b). The moving distance is determined from the number of rectangular pulses of this output signal.

In addition, in order to measure the moving distance with an accuracy less than the interval of the scale, multiple sensors are installed so that their output signals have a phase difference of H, and from the phase difference of the output signals, it is possible to measure the distance with an accuracy of less than the interval of 11 graduations. Measurements can be made.

[Problems to be Solved by the Invention] However, the measurement accuracy of conventional linear scales depends on the scale interval and its accuracy. That is.

Ag3 cannot be determined with high accuracy unless the scale intervals are narrow and the intervals are highly accurate and constant. For this reason,
The problem is that creating long scales is difficult and expensive.

[Means for determining the angle of 'll'XJ] The present invention includes:
11 movable member, a fixed member, and a moving means for moving the i+J movable member in a predetermined direction.

A linear scale for measuring the moving distance of the movable member, wherein one of the 01 movable member and the fixed member is provided with a scale portion having a plurality of scales at predetermined intervals, and the other is provided with a reading means for reading the scale, and the moving distance of the movable member is measured. A one-dimensional optical sensor is used as the reading means, and the interval between the scales is narrower than the width of the field of view of the one-dimensional optical sensor [Embodiment] The present invention will now be described in detail with reference to the drawings. explain.

FIG. 1 shows the configuration of a ml example. This embodiment consists of a movable plate l provided with a scale and a one-dimensional optical sensor 2 for reading the scale. a moving device (not shown) for moving the moving plate 1;
A signal processing bag wt (not shown) is provided for determining the moving distance of the moving plate 1 from the output of the one-dimensional optical sensor 2. Here, the one-dimensional optical sensor 2 is fixed to a stand (not shown).

The scale provided on the moving plate 1 (here, the scale includes a black and white striped pattern, a hole that transmits light, a light emitting part of the reflective material 1 that reflects light, a bar code, etc.) is as shown in FIG. CL>1> is provided such that the interval p between the scales 3 is smaller than the width of the one-dimensional optical sensor 2.

Figure 3 shows how to read the scale. The linear scale shown in Figure 3(a) is a transmission type linear scale, which primarily uses light from a light source that passes through a scale or a hole that transmits light provided on a moving plate made of a transparent material. It is detected by the original light sensor.

The linear scale shown in FIG. 3(b) is a reflective linear scale, in which a single plate is provided to reflect the light from the light source 4 on the movable plate 1, and the reflected light is detected.

The linear scale shown in FIG. 3(C) is a light-emitting type linear scale, in which a light-emitting member 5 is provided as a scale on the movable plate 1, and light from nine light-emitting portions 5 is detected.

Note that such one-dimensional photosensors are commercially available, each having 5,000 pixels and weighing approximately 1 g.

You can use it.

FIG. 4 shows the output of the one-dimensional optical sensor 2 of this embodiment. As the moving plate 1 moves to the right in the order of FIG. go. From this change, the moving distance of the moving plate 1 can be determined.

When a plurality of pixels detect a scale as shown in FIG. 4(b), by performing a predetermined calculation based on the magnitude of the output, measurement can be performed with an accuracy less than the pixel pitch.

Furthermore, if the so-called smoothing differential method is used in the above calculation, it is possible to perform measurements with higher precision.

A method known as the zero-crossing method is generally used as a signal processing method to find the peak position, but the smoothing differential method here refers to smoothing the output of a -dimensional sensor to obtain a differential coefficient. The peak position of the output signal is determined by approximating the points before and after the sign changes from positive to negative using a linear equation to find the point where the sign becomes 0.

That is, the differential coefficient f'(xt) of the output signal f(x,)
For example, see Reference A, 5aviLzky and
M.J.

p, Golay, ^nalyLical Cem1sL
ry, 3B(8), (1964) 1B27, 1.

f'(xt)--Σ J'' f (Xt+1
) w ”-1 , where W is a normalization constant.

According to the present invention, the differential coefficients f'(xm), f'(x,
When the sign changes from positive to negative in 1), by approximating this period with a linear equation, x-xk+ f'(xh) (Xi++ Xm) f' (X*) f' (X*-r
), and use this as the peak position.

FIG. 5 shows a second embodiment. The linear scale shown in FIG. 5 has an optical system lens 6 between the moving plate 1 and the one-dimensional optical sensor.
The scale provided on the movable plate 1 is enlarged and read.

As with the first embodiment, methods for reading the scale include transmission type, zero reflection type, and one emission type.

Since the present invention does not require fine scales, the scales themselves may be large, and R1 functionality is achieved by using coded patterns such as bar codes as scales. Moreover, a bar code or the like can be written between the scales.

With this,! 11, information such as not only the moving distance but also the position of the thin body of the moving plate can be obtained.

[Effects of the Invention] According to the present invention, a movable member, a fixed member, and a moving means for moving the movable member in a predetermined direction are H, and either the movable member or the fixed member is spaced at a predetermined interval. a scale part having a plurality of scales, and a reading means for reading the scales on the other side.

In the linear scale for measuring the moving distance of the movable member, a one-dimensional optical sensor is used as the reading means, and the interval between the scales is narrower than the width of the field of view of the one-dimensional optical sensor, so that a fine repeating pattern is formed. There is no need to fabricate it, making it easy and inexpensive to fabricate.

Further, by providing a signal processing means that performs signal processing using the smoothing differential method, it becomes possible to perform measurement with an accuracy equal to or less than the pixel pitch of a one-dimensional optical sensor.

Furthermore, measurement accuracy is improved by providing an optical lens between the movable member and the reading means.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a linear scale according to the first embodiment of the present invention, Fig. 2 is a diagram for explaining the relationship between the scale and a one-dimensional optical sensor, and Fig. 3 is a diagram of the first embodiment. (a) is a transmissive type, (b) is a reflective type, and (C) is an emissive type.
) is a diagram showing the relationship between the scale of the present invention and its detection signal,
FIG. 5 is a schematic diagram of the second embodiment of the present invention, and FIG. 6 is a diagram showing the relationship between the conventional scale and its detection signal, (a) is an enlarged view of the scale, and (b) is a diagram showing the relationship between time and FIG. 3 is a diagram showing the relationship with sensor output. 1... Moving plate, 2... One-dimensional optical sensor, 3... Scale. 4... Light source, 5... Light emitting member, 6... Optical system lens. Figure 1 Figure 3 Figure 4 Figure 5 (Movement direction 2 Figure 6 (b) Output signal of conventional sensor

Claims (1)

[Scope of Claims] 1. A movable member, a fixed member, and a moving means for moving the movable member in a predetermined direction, and either the movable member or the fixed member has a plurality of movable members arranged at predetermined intervals. In a linear scale that measures the moving distance of the movable member by providing a scale part having graduations on the other side and a reading means for reading the graduations, a one-dimensional optical sensor is used as the reading means, and the interval between the graduations is determined by the one-dimensional reading means. A linear scale characterized by being narrower than the width of the optical sensor's field of view. 2. The linear scale according to claim 1, further comprising signal processing means for processing the read signal output from the one-dimensional optical sensor using a smoothing differential method. 3. The linear scale according to claim 1, wherein an optical lens is provided between the scale section and the reading means, and the scale is enlarged for reading.