Encoder device

• US 7,227,125 B2
• Filed: 03/30/2006
• Issued: 06/05/2007
• Est. Priority Date: 06/29/2005
• Status: Expired due to Fees

• Current Assignee: Mitsumi Electric Co., Ltd. (Minebea Mitsumi, Inc.)
• Original Assignee: Mitsumi Electric Co., Ltd. (Minebea Mitsumi, Inc.)
• Inventors: Waki, Naosumi, Tanaka, Junichiro, Sannomiya, Hideaki
• Primary Examiner(s): PYO, KEVIN K
• Application Number:
  US11/393,106
• Publication Number:
  US 20070001108A1
• Time in Patent Office: 432 Days
• Field of Search: 250/231.13, 250/231.14, 25023116-23118, 250/237.R, 250/214.R, 341/9, 341/13
• US Class Current: 250/231.13
• CPC Class Codes: G01D 2205/90 Two-dimensional encoders, i.e. having one or two codes extending in two directions
• CPC Class Codes: G01D 5/34746 Linear encoders
• CPC Class Codes: G01D 5/36 Forming the light into pulses

Abstract

An encoder device includes a first array that includes first through fourth photodiodes adjacent to each other in an X direction, each having a length of X1; a second array that includes fifth through eighth photodiodes adjacent to each other in the X direction, each having a length of X1, and is adjacent to the first array in a Y direction but displaced by X1/2 in the X direction relative to the first array; a slit member that includes light transmitting sections and light shielding section arranged alternately, each having a length 2×X1, and is movable in the X direction; and a logic circuit that generates first and second detection signals from output signals of the first through fourth photodiodes and output signals of the fifth through eighth photodiodes, respectively, a phase of the second detection signal being shifted by a ¼ period of the first detection signal relative to the first detection signal.

Claims

1. An encoder device comprising:

a first array that includes first through fourth photodiodes adjacent to each other in an X direction, each of the first through fourth photodiodes having a length of X1 in the X direction;

a second array that includes fifth through eighth photodiodes adjacent to each other in the X direction, and is adjacent to the first array in a Y direction perpendicular to the X direction but displaced by X1/2 in the X direction relative to the first array, each of the fifth through eighth photodiodes having a length of X1 in the X direction;

a slit member that includes light transmitting sections and light shielding sections alternately arranged, and is movable in the X direction, each of the light transmitting sections and the light shielding sections having a length of 2×

X1 in the X direction; and

a logic circuit that generates a first detection signal from output signals of the first through fourth photodiodes that have received lights passing through the light transmitting sections, and a second detection signal from output signals of the fifth through eighth photodiodes that have received the lights passing through the light transmitting sections, a phase of the second detection signal being shifted by a ¼

period of the first detection signal relative to the first detection signal.

2. The encoder device as claimed in claim 1,

wherein each of the first through eighth photodiodes has a width of Y1 in the Y direction;

and

each of the light transmitting sections and the light shielding sections has a width greater than 2×

Y1 in the Y direction.

3. The encoder device as claimed in claim 1, wherein the logic circuit includes

a first circuit that generates the first detection signal by performing an exclusive OR operation on a signal representing a result of a comparison between the output signal of the first photodiode and the output signal of the third photodiode and a signal representing a result of a comparison between the output signal of the second photodiode and the output signal of the fourth photodiode;

and

a second circuit that generates the second detection signal by performing an exclusive OR operation on a signal representing a result of a comparison between the output signal of the fifth photodiode and the output signal of the seventh photodiode and a signal representing a result of a comparison between the output signal of the sixth photodiode and the output signal of the eighth photodiode.

4. The encoder device as claimed in claim 1,

wherein a plurality of pairs of the first array and the second array are provided adjacent to each other in the X direction.

5. An encoder device comprising:

a photodiode group that includes n (n being an integer equal to or greater than

     3) photodiode arrays adjacent to each other in a Y direction, each of the photodiode arrays including four photodiodes adjacent to each other in an X direction, each of the photodiodes having a length of X1 in the X direction, wherein any two adjacent of the photodiode arrays are displaced by X1/n in the X direction relative to one another;

a slit member that includes light transmitting sections and light shielding sections alternately arranged, and is movable in the X direction, each of the light transmitting sections and the light shielding sections having a length of 2×

X1 in the X direction; and

a logic circuit that generates first through n th detection signals from output signals of the n photodiode arrays that have received lights passing through the transmitting sections, a phase shift between the detection signals of the any two adjacent photodiode arrays being a 1/(2×

n) period.