Absolute angle calculation apparatus

Abstract

The present invention provides a calculation circuit (11) calculating an absolute angular position based on a spatially modulated component in a photoelectrically-converted signal string. The calculation circuit (11) can not only shorten the angular operation time but also can accurately measure the absolute angular position. The calculation circuit (11) includes a photoelectrically-converted signal string storage (14) storing previous and current photoelectrically-converted signal strings obtained, for interpolating the absolute angular position, within a set time shorter than an absolute angle calculation time required to calculate the absolute angular position; a correlation detection circuit (15A) detecting a correlation between the previous and current photoelectrically-converted signal strings in the photoelectrically-converted signal string storage (14) and detecting a shift amount therebetween; and an interpolation calculation circuit (15B) interpolating an inter-pattern absolute angular position equivalent, value based on the shift amount obtained by the current measurement. The calculation circuit (11) calculates an interpolated angle based on the shift amount and the absolute angular position equivalent value, adds the calculated interpolated angle obtained at the current measurement to the absolute angular position obtained at the previous measurement to calculate a current absolute angular position.

Description

technical field [0001] The present invention relates to an absolute angle computing device that computes an absolute angular position relative to a reference angular position using, for example, a rotary encoder incorporated in a rotary laser device. Background technique [0002] In the past, as shown in FIG. 1, a device having the following structure is well known: a rotating prism (not shown) is rotated, for example, at a speed of 3 revolutions / second (180 revolutions / minute) with a measuring device such as a rotating laser device 1, and the fan-shaped beam BP It shoots at the target 2, then receives the reflected light BP' from the target 2, and detects the absolute angular position θ of the target 2 relative to the reference angular position Q of the rotating laser device 1. [0003] For example, at the detected absolute angular position θ, the rotating laser device 1 is used to irradiate the target 2 with laser light, and then the reflected light BP' from the target 2 i...

AI Technical Summary

Problems solved by technology

[0009] However, it usually takes about 100 milliseconds (ms) for this calculation circuit to calculate the absolute angular position θ

In view of this, the rotary encoder 3 rotates, for example, about 108 degrees during the period of 100 milliseconds. Therefore, if the measurement is performed at intervals of 100 milliseconds, there is the following problem: that is, the position of the target 2 with respect to the reference angular position Q cannot be obtained. Precise absolute angular position θ

[0010] In addition, when measuring two or more targets 2 at the same time, if there are two or more targets at angular positions less than 108 degrees, at least one of them cannot measure the absolute angular position

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