Patent ID: 7731330

Claim:
A position detecting device for detecting a position of an object, comprising: a light emitting portion that emits light; a light receiving portion that receives the light from the light emitting portion; a scale that is arranged between the light emitting portion and the light receiving portion, and includes a position detecting pattern and a smear detecting pattern; and a control portion which determines position from the position detecting pattern and determines smear from the smear detecting pattern, wherein the control portion does not determine position from the smear detecting pattern and the control portion does not determine smear from the position detecting pattern; wherein the position detecting pattern has a first light transmitting portion for transmitting the light from the light emitting portion and a first light interception portion for intercepting the light from the light emitting portion which are alternately arranged in a detection range of the object; and wherein the smear detecting pattern for detecting smear of the scale has a second light transmitting portion for transmitting the light from the light emitting portion and a second light interception portion for intercepting the light from the light emitting portion which are alternately arranged.