Pulse generator
A pulse generator which can be used for a printer, for example an ink jet printer, to provide adjustable pulses per unit displacement or speed has a linearly or rotatably displaceable first plate with a periodic pattern of different optical density or transmissivity or reflectivity juxtaposed with a second plate with another array of markings of different optical density transmissivity or reflectivity so that in an overlapping region a Moiré pattern or other interference pattern for beat pattern is provided. The latter is detected by an optical sensor which outputs electrical pulses. The two plates can be relatively displaced to change the pattern and hence the detected periodicity.
1. A pulse generator comprising:
a first plate having regions of optical characteristics that vary with a first periodicity (P 1 );
a second plate having regions of optical characteristics that vary with a second periodicity (P 2 ) juxtaposed with said first plate so that at least in a superimposition zone of the regions with said first and second periodicity, a region is formed with optical characteristics that vary with a third periodicity (P 3 ) that is a function of said first and second periodicities, said third periodicity being a Moiré pattern that is varied by a manual relative shifting of said first and second plates, the optical characteristics being selected from optical density, reflectivity, and transmissivity; and
an optical sensor positioned to detect the periodically different optical characteristics of said third periodicity and to generate an electric signal corresponding to the detected periodically different optical characteristics of said third periodicity.
2. The pulse generator defined in claim 1 wherein the first and second plates are so juxtaposed in said superimposition zone as to generate a Moiré pattern with at least one third periodicity detectable by said optical sensor.
3. The pulse generator defined in claim 1 wherein at least one of said plates is movable relative to the other plate and said optical sensor.
4. The pulse generator defined in claim 3 wherein said one of said plates is movable linearly with respect to said other plate and said optical sensor.
5. The pulse generator defined in claim 3 wherein said one of said plates is movable rotatably with respect to said other plate and said optical sensor.
6. The pulse generator defined in claim 1 wherein one of said plates is a linearly movable plate having regions of periodically different optical characteristics with a respective periodicity extending linearly and parallel to one another at a given spacing transverse to a direction of movement of said one of said plates.
7. The pulse generator defined in claim 1 wherein one of said plates is a rotatable plate having regions of periodically different optical characteristics with a respective periodicity extending linearly or curvilinearly and angularly equispaced about a center of rotation of said rotatable plate.
8. The pulse generator defined in claim 7 wherein said regions of periodically different optical characteristics of said rotatable plate are radial lines.
9. The pulse generator defined in claim 7 wherein said regions of periodically different optical characteristics of said rotatable plate are curved lines.
10. The pulse generator defined in claim 1 wherein said regions of periodically different optical characteristics are lines spaced apart upon a transparent support.
11. The pulse generator defined in claim 1 wherein the relative shifting is a change in an angle (α) between said plates.
12. The pulse generator defined in claim 1 , further comprising a micrometer screw operating on one of said plates to effect manual relative shifting of said plates.
13. The pulse generator defined in claim 1 , further comprising
an electric motor coupled to one of said plates to effect relative shifting of said plates.
14. The pulse generator defined in claim 1 wherein a plurality of said second plates and a plurality of optical sensors are juxtaposed with said first plate and at different angles therewith.