Optical type encoder

Abstract

The present invention provides an optical encoder comprising a light source, a first scale plate for converting light from the light source into a periodic light quantity distribution, and a light source for periodically spatially transforming the light from the first scale plate. The modulated second scale plate, the third scale plate with an opening through which the light from the second scale plate passes, and the photosensitive element for receiving the light from the third scale plate, measure the relative movement of the first and second scale plates The distance is characterized by having a lens that converts the light from the light source into approximately parallel light and an optical element array that condenses or diffuses the light in the above-mentioned periodic direction on the first scale plate to generate a periodic light quantity distribution.

Description

technical field [0001] The present invention relates to an optical encoder that optically detects the amount of relative movement between grid scales. Background technique [0002] As one type of optical encoder, an optical encoder using three grating scale plates is known. In this optical encoder, three scale plates are sequentially arranged along the light traveling direction, and the main surfaces of the scale plates are set to be parallel to each other, and the arrangement directions of the gratings provided on the scale plates are consistent. In addition, a light source with low spatial interference is installed in front of the first reticle. A photosensitive element that converts the light quantity into an electrical signal is installed behind the third scale plate. [0003] Non-Patent Document 1 discloses its operation. When the light source irradiates the first reticle, a secondary light source with low spatial coherence and a multi-slit-like light intensity distr...

AI Technical Summary

Problems solved by technology

[0017] In Patent Document 2, the characteristic is that a transparent phase grating is used in the first scale plate, and the light and dark patterns of a certain period are generated by the interference of diffracted light from each grating, and the light and dark pattern distribution based on the phase grating Due to the use of diffraction and interference phenomena, it greatly depends on the phase grating period, the shape of the phase grating, and the wavelength of the light source, and many items such as design margin, work accuracy, and parts management are restricted.

Also, as in Patent Document 1, since diffused light is irradiated on the first reticle, light cannot be efficiently incident on the photosensitive element.

Furthermore, due to the dispersion of the position of the diffuse light source and the radiation characteristics, the position, period, and deformation of the light and dark pattern of the first scale plate change, and the characteristics of the optical encoder may deteriorate.

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