Optical encoder with comparator hysteresis changed with rotating speed and operating method thereof
AssigneePixart Imaging Inc.
InventorsChung-Min Thor, Kuan-Choong Shim
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Abstract
There is provided an optical encoder including a phase shifter circuit and a multiple hysteresis comparators. The phase shifter circuit receives four input signals, and outputs multiple phase shifted signals based on the four input signals. Each of the multiple hysteresis comparators uses a changeable operation hysteresis level to compare a couple of phase shifted signals among the multiple phase shifted signals, wherein the changeable operation hysteresis level is determined corresponding to a signal frequency of the four input signals.
Claims20
An optical encoder, comprising:
- an encoding medium;
- a phase shifter circuit, configured to receive a first input signal, a second input signal, a third input signal and a fourth input signal, and output multiple phase shifted signals based on the first input signal, the second input signal, the third input signal and the fourth input signal;
- a comparison circuit, comprising multiple hysteresis comparators each being configured to compare a couple of phase shifted signals among the multiple phase shifted signals using an operation hysteresis level;
- and
- a frequency detector, configured to select the operation hysteresis level of each of the multiple hysteresis comparators corresponding to predetermined multiple frequency ranges associated with a rotating speed of the encoding medium.
An optical encoder, comprising:
- an encoding medium;
- a phase shifter circuit, configured to receive a first input signal, a second input signal, a third input signal and a fourth input signal, and output multiple phase shifted signals based on the first input signal, the second input signal, the third input signal and the fourth input signal;
- a comparison circuit, comprising multiple hysteresis comparators each being configured to compare a couple of phase shifted signals among the multiple phase shifted signals using an operation hysteresis level;
- and
- a frequency detector, configured to change the operation hysteresis level of each of the multiple hysteresis comparators in a step manner when a rotating speed of the encoding medium is progressively decreasing or increasing.
An operating method of an optical encoder, the optical encoder comprising an encoding medium, multiple hysteresis comparators and a frequency detector, the operating method comprising:
- comparing, by each of the multiple hysteresis comparators, a couple of phase shifted signals among multiple phase shifted signals using an operation hysteresis group;
- detecting, by the frequency detector, a rotating speed of the encoding medium;
- and
- changing, by the frequency detector, the operation hysteresis group in a step manner when the rotating speed of the encoding medium is progressively decreasing or increasing.
Dependencies are inferred from the claim text.