Encoder

• US 20050199791A1
• Filed: 03/09/2005
• Published: 09/15/2005
• Est. Priority Date: 03/12/2004
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Tokai RIKA Denki Seisakusho
• Original Assignee: Kabushiki Kaisha Tokai RIKA Denki Seisakusho
• Inventors: Ito, Shigeji, Futamura, Yasuhiko, Sengoku, Norimasa
• Granted Patent: US 7,214,931 B2
• Time in Patent Office: Days
• US Class Current: 250/231.13
• CPC Class Codes: G01D 5/3473 Circular or rotary encoders

Abstract

An encoder for stably detecting the amount of movement of an object. The encoder includes an LED for emitting light toward a rotor plate including slits. An optical sensor generates an ON signal when the amount of emitted light passing through the slits exceeds a threshold value. A current increasing circuit increases the amount of current flowing through the LED when the optical sensor generates an ON signal.

Claims

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;

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; and

a current increasing circuit for increasing the amount of current flowing through the light emitting device when the detector generates the ON signal.

2. The encoder according to claim 1, wherein the detector generates the ON signal when the amount of emitted light exceeds an ON threshold value and generates an OFF signal when the amount of emitted light decreases to an OFF threshold value that is lower than the ON threshold value.

3. The encoder according to claim 1, wherein the light emitting device includes a path connected to ground, and the current increasing circuit includes a load connected in parallel to the light emitting device when the detector generates the ON signal.

4. The encoder according to claim 3, wherein the load is a resistor.

5. The encoder according to claim 1, further comprising:

a resistor connected between the light emitting device and the ground, wherein the current increasing circuit includes a load connected in parallel to the resistor when the detector generates the ON signal.

6. The encoder according to claim 5, wherein the load is a resistor.

7. The encoder according to claim 1, wherein:

the light emitting device is connected to ground;

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.

8. The encoder according to claim 7, wherein the load is a resistor.

9. The encoder according to claim 7, further comprising:

a resistor connected between the node and ground.