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:
- multiple hysteresis comparators, each being configured to compare a couple of phase shifted signals among multiple phase shifted signals, which are generated based on a first input signal, a second input signal, a third input signal and a fourth input signal, using an operation hysteresis level;
- and
- a frequency detector, configured to detect an input signal frequency according to at least one of the first input signal, the second input signal, the third input signal and the fourth input signal, and select the operation hysteresis level of each of the multiple hysteresis comparators according to the detected input signal frequency.
An optical encoder, comprising:
- an encoding medium;
- multiple hysteresis comparators, each being configured to compare a couple of phase shifted signals among multiple phase shifted signals, which are generated based on a first input signal, a second input signal, a third input signal and a fourth input signal, 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 multiple predetermined frequency ranges associated with a rotating speed of the encoding medium.
An optical encoder, comprising:
- an encoding medium;
- multiple hysteresis comparators, each being configured to compare a couple of phase shifted signals among multiple phase shifted signals, which are generated based on a first input signal, a second input signal, a third input signal and a fourth input signal, 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.
Dependencies are inferred from the claim text.