Method and apparatus for controlling a stepper
AssigneeAdvanced Micro Devices, Inc.
InventorsAnthony John Toprac, Richard David Edwards, Curtis Warren Doss
Life of this patent
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Abstract
In one illustrative embodiment, a method is provided that comprises energizing a light source to provide light having a preselected intensity. A first photosensor, which is capable of delivering a first signal indicative of the intensity of the light source, is exposed to the light source. A second photosensor, which is also capable of delivering a second signal indicative of the intensity of the light source, is also exposed to the light source. Thereafter, the first and second signals are compared, and an error signal is delivered in response to detecting a significant difference between the first and second signals.
Claims13
An apparatus, comprising:
- means for energizing a light source to provide light having a preselected intensity;
- means for exposing a first photosensor to the light source, wherein the first photosensor is capable of delivering a first signal indicative of the intensity of the light source;
- means for exposing a second photosensor to the light source, wherein the second photosensor is capable of detecting the intensity of the light source;
- means for comparing the first and second signals;
- means for delivering an error signal in response to detecting a difference of a preselected magnitude between the first and second signals.
A stepper, comprising:
- a light source capable of providing light having a preselected intensity;
- a first photosensor capable of delivering a first signal indicative of the intensity of the light source;
- a second photosensor capable of delivering a second signal indicative of the intensity of the light source;
- and
- a controller adapted to compare the first and second signals, and deliver an error signal in response to detecting a difference of a preselected magnitude between the first and second signals.
An apparatus, comprising:
- means for energizing a first light source to provide light having a first preselected intensity;
- means for exposing a photosensor to the first light source, wherein the photosensor is capable of delivering a first signal indicative of the intensity of the first light source;
- means for controlling a duration that the first light source is energized based on the first signal;
- means for periodically energizing a second light source to provide light having a second preselected intensity;
- means for exposing the photosensor to the second light source, wherein the photosensor is capable of delivering a second signal indicative of the intensity of the second light source;
- means for comparing the second signal with a preselected setpoint;
- and
- means for delivering an error signal in response to detecting a difference of a preselected magnitude between the second signal and the preselected setpoint.
A stepper, comprising:
- a first light source capable of providing light having a first preselected intensity;
- a second light source capable of providing light having a second preselected intensity;
- a photosensor capable of delivering a first signal indicative of the intensity of the first light source and a second signal indicative of the intensity of the second light source;
- and
- a controller adapted to compare the second signal with a preselected setpoint, and deliver an error signal in response to detecting a difference of a preselected magnitude between the second signal and the preselected setpoint.
Dependencies are inferred from the claim text.