Method for rapid imaging of thermographic materials by extending exposure time in a single beam laser scanner

Abstract

The exposure time of high data rate single spot laser scanner can be extended by the use of Time Domain Integration (TDI) mode imaging to expose thermographic materials. Many thermographic materials, such as thermal printing plates, can not be properly exposed in single spot scanners such as internal drum scanners, due to the shortness of the exposure time of a single spot, but can be exposed by the extended exposure time of TDI scanning. The Scophony effect can also be used as a method of TDI.

What is claimed is:  
     
       1. A method for imaging on a thermographic material, the method comprising: 
       (a) providing a layer of thermographic material;  
       (b) scanning a beam along a line on a surface of the thermographic material in a first direction, the beam comprising images of a plurality of light sources, the images all lying on the line;  
       (c) providing data representing an exposure to be given to a spot lying on the line;  
       (d) modulating each of the light sources in response to the data in a manner synchronized with scanning the beam along the line such that:  
       (i) a first one of the light sources is modulated in response to the data during a dwell time when an image of the first one of the light sources is on the spot; and,  
       (ii) each subsequent one of the light sources is modulated in response to the data during dwell times when an image of each subsequent one of the light sources is on the spot.  
     
     
       2. The method of claim  1  wherein a scanning velocity of the beam along the line is such that the dwell times for each of the images is too short to damage the thermographic material in the vicinity of the spot. 
     
     
       3. The method of claim  2  wherein a scanning velocity of the beam along the line is such that the dwell times for each of the images is too short to fully expose the thermographic material in the vicinity of the spot. 
     
     
       4. The method of claim  2  wherein the layer of thermographic material is on an internal cylindrical surface and scanning a beam along a line on a surface of the thermographic material comprises deflecting the beam with a rotating beam deflector located on an axis of curvature of the cylindrical surface. 
     
     
       5. The method of claim  4  wherein a shift register has a bit corresponding to each of the light sources and the method comprises placing the data into the shift register and clocking the shift register to modulate the light sources in sequence. 
     
     
       6. The method of claim  5  wherein clocking the shift register comprises applying clock pulses generated in response to rotation of the beam deflector to the shift register. 
     
     
       7. The method of claim  4  wherein the light sources comprise a linear array of lasers. 
     
     
       8. The method of claim  7  wherein the lasers are not matched in intensity. 
     
     
       9. The method of claim  2  wherein a shift register has a bit corresponding to each of the light sources and the method comprises placing the data into the shift register and clocking the shift register to modulate the light sources in sequence. 
     
     
       10. The method of claim  9  wherein the light sources comprise a linear array of lasers. 
     
     
       11. The method of claim  10  wherein the light sources are not matched in intensity. 
     
     
       12. The method of claim  9  wherein the light sources each comprise a beam split from a single laser beam and a modulator. 
     
     
       13. The method of claim  12  wherein a profile of the single beam is non-uniform and the individual beams are unequal in intensity. 
     
     
       14. The method of claim  9  wherein the light sources comprise portions of a beam outgoing from an AOM and modulating one of the light sources comprises operating a RF modulator of the AOM in response to the data and allowing the resulting acoustic wave to propagate to a portion of the AOM corresponding to the one of the light sources. 
     
     
       15. The method of claim  2  wherein the light sources are not matched in intensity. 
     
     
       16. The method of claim  1  wherein the light sources comprise a linear array of lasers and wherein the lasers are not matched in intensity.