Patent ID: 7289229

Claim:
An optical displacement-measuring instrument, comprising: a light source configured to provide a collimated light; a light diffuser arranged to diffuse said collimated light from said light source; a first optical grating arranged to diffract a diffused light from said light diffuser; a scale having a second optical grating arranged opposite to said first optical grating to diffract a diffracted light from said first optical grating; and a photoreceptor movable together with said light source, said light diffuser and said first optical grating relative to said scale and having a third optical grating arranged opposite to said second optical grating to receive a diffracted light from said second optical grating, wherein said first and second gratings have a gap of 1.0 mm or less therebetween, and said third and second optical gratings have a gap of 1.0 mm or less therebetween.