Patent ID: 7214931
Filing Date: 2007-05-08
Classification: G01D

Abstract:
1. An encoder for detecting the amount of movement of a movable object having a plurality of slits, the encoder comprising: a light emitting device for emitting light toward the object so that the emitted light is passable through the slits of the object, wherein the light emitting device is connected to ground; a detector for receiving the emitted light of the light emitting device that passes through the slits and for generating an ON signal when the amount of emitted light exceeds a threshold value; a current increasing circuit for increasing the amount of current flowing through the light emitting device when the detector generates the ON signal, wherein the detector includes a switching device, having a power supply terminal connected to a power supply and a ground terminal connected to ground, for connecting the power supply to ground when the amount of emitted light exceeds a threshold value; and the current increasing circuit includes a load connected between the power supply terminal of the switching device and a node between the light emitting device and ground, and a resistor connected between the node and ground, wherein the switching device connects the power supply to ground such that the current flowing through the light emitting device is the sum of the current flowing through the load and the current flowing through the resistor to increase the amount of current flowing through the light emitting device.