Movement sensor
AssigneeKoninklijke Philips Electronics N.V.
InventorMartin Dieter Liess
Life of this patent
Estimating the term…
Abstract
In an apparatus for handling sheet material or an optical input device, for example, which employs a relative movement sensor (108) utilizing the so-called “self-mixing” effect of a laser diode, a band pass filter (100) is provided for filtering the electric signal resulting from measurement of the electric signal to reduce or substantially eliminate the effects of both the low frequency carrier signal and the high frequency noise present in such a signal. As a result, the precision of the laser self-mixing translation measurements is significantly improved.
Claims14
A relative movement sensor for measuring movement of an object and said sensor relative to each other, the sensor comprising:
- at least one laser, having a laser cavity, for generating a measuring beam and illuminating an object therewith, wherein at least some of the measuring beam radiation reflected by said object re-enters said laser cavity;
- measuring means for measuring changes in operation of said laser cavity caused by interference of reflected measuring beam radiation re-entering said laser cavity and the optical wave in said laser cavity;
- means for providing a first electric signal representative of said changes;
- band pass filter means for filtering said first electric signal so as to at least reduce the contribution thereto by low and high frequency noise to produce a second electric signal representative of said changes for use in determining relative movement of said object and said sensor;
- and
- a motor configured to effect said relative movement, wherein a pass band of the band pass filter means is set and dynamically changed and controlled in accordance with a speed of said motor.
A method for measuring movement of an object and a sensor relative to each other, the sensor comprising at least one laser, having a laser cavity, for generating a measuring beam and illuminating an object therewith, wherein at least some of the measuring beam radiation reflected by said object re-enters said laser cavity, the method further comprising:
- measuring changes in operation of said laser cavity caused by interference of reflected measuring beam radiation re-entering said laser cavity and the optical wave in said laser cavity;
- providing a first electric signal representative of said changes;
- and
- filtering said first electric signal so as to at least reduce the contribution thereto by low and high frequency noise to produce a second electric signal representative of said changes for use in determining relative movement of said object and said sensor, wherein the relative movement is effectuated by a motor, and wherein the filtering is set and dynamically changed and controlled in accordance with a speed of said motor.
Dependencies are inferred from the claim text.