Absolute encoder based on an incremental encoder

• US 6,683,543 B1
• Filed: 01/30/2003
• Issued: 01/27/2004
• Est. Priority Date: 01/30/2003
• Status: Expired due to Fees

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Yeo, Chiau Woon
• Primary Examiner(s): Tokar, Michael
• Assistant Examiner(s): MAI, LAM T
• Application Number:
  US10/356,438
• Time in Patent Office: 362 Days
• Field of Search: 341/13, 341/11, 341/2, 250/231
• US Class Current: 341/13
• CPC Class Codes: G01D 5/2457 Incremental encoders having reference marks
• CPC Class Codes: H03M 1/308 with additional pattern means for determining the absolute position, e.g. reference marks

Abstract

An encoder that includes a sensing device that senses encoding marks on a sensing surface that also includes one or more reference marks. The sensing device generates first and second encoder signals when the encoding marks pass the sensing device. The encoding signals define the direction of motion and degree of movement of the sensing surface. A register stores the position of the encoding surface relative to the sensing device. A controller receives the first and second encoder signals and increments or decrements the digital register based on the received first and second encoder signals. The encoder also includes a reference mark detector that generates a first reference mark signal when the first reference mark passes the reference mark detector. The controller resets the digital value to a first reference value when the encoder receives the first reference mark signal.

Claims

1. An encoder comprising:

a sensing device that generates first and second encoder signals;

a sensing surface comprising a plurality of uniformly spaced encoding marks, said surface moving with respect to said sensing device such that said first and second encoder signals are generated when said encoding marks pass said sensing device, said second encoder signal leading or lagging said first encoder signal depending on the direction of said movement of said sensing surface with respect to said sensing device;

a reference mark detector for detecting said first reference mark and generating a first reference mark signal indicative of said detection;

a register for storing a digital value; and

a controller for receiving said first and second encoder signals and for incrementing or decrementing said digital register based on said received first and second encoder signals, wherein said controller resets said digital value to a first reference value when said encoder receives said first reference mark signal.

2. The encoder of claim 1 further comprising:

a non-volatile memory for storing a register value; and

a power detection circuit for determining if the potential on a power supply line is decreasing and increasing,

wherein said controller causes said digital value to be stored in said non-volatile memory when said power detection circuit determines that said potential is decreasing.

3. The encoder of claim 2 wherein said controller causes said stored register value to be loaded into said register when said power detection circuit determines that said potential is rising.

4. The encoder of claim 1 wherein said encoding surface further comprises a second encoding mark, wherein said reference detector generates a second reference mark signal when said second encoding mark is detected, and wherein said controller resets said digital value to a second reference value when said second reference mark signal is generated.

5. The encoder of claim 1 wherein said encoding surface comprises a disk connected to a shaft that rotates with respect to said sensing device when said shaft turns.

6. The encoder of claim 1 wherein said encoding surface comprises a strip that moves with respect to said sensing device when said surface moves parallel to a predetermined direction.