Compact flatbed page scanner

Abstract

A compact flatbed page scanner for facsimile transmission is described. The apparatus uses a linear charge coupled imaging device (CCID) for both light detection and electronic scanning across the width of the page. Compactness is achieved by folding the optical path from the scanned line to the CCID. A moving carriage below a horizontal glass plate supporting the document to be scanned carries: the linear CCID, a lens for focusing an image of one scanning line of the page onto the CCID, an assembly of bar mirrors for folding the path of the light beam from the scanning line to the lens, and tubular lamps for illuminating the scanning line. The motion of the carriage beneath the horizontal glass plate permits scanning an array of parallel lines, equally spaced over the length of the page. In the apparatus described, scanning a complete page may be performed from 4 seconds to several minutes, depending on the bandwidth available for transmission.

What is claimed is: 
     
       1. A compact flatbed scanner for facsimile scanning comprising: a. a housing;   b. a transparent plate mounted on the housing for supporting material to be copied, the transparent plate defining the approximate image plane of the material to be copied;   c. a moving scanning assembly supported within the housing beneath the transparent plate, the scanning assembly comprising: 1. at least one lamp for illuminating at least a portion of the image plane,   2. a linear charge coupled imaging device for detecting variations in intensity of light reflected from a scanning line on the image plane and having electrical contacts adapted to provide electronic scanning over the length of the scanning line, and   3. an optical system for focusing the light reflected from the scanning line onto the linear charge coupled imaging device, the optical system comprising a plurality of long, narrow mirrors for folding the optical path from the scanning line to the linear charge coupled imaging device;     d. means for mechanically displacing the scanning assembly relative to the image plane in a direction parallel to the image plane and perpendicular to the scanning line to permit scanning a succession of parallel lines from one end of the image plane to the other; and   e. electrical circuitry for sequentially reading out each scanning line detected by the linear charge coupled imaging device by forming an electrical signal representative of the variations in intensity of light reflected from the image plane along a succession of scanning lines.   
     
     
       2. A compact flatbed scanner for facsimile scanning comprising: a. a housing;   b. a transparent rigid plate fixedly mounted on the housing for supporting material to be copied the transparent plate defining the approximate image plane of the material to be copied;   c. a moving scanning assembly and slidably mounted within the housing beneath the transparent rigid plate, the scanning assembly comprising a casing supporting: 1. a fluorescent lamp excited by a DC power-supply for illuminating at least a portion of the material to be copied,   2. a linear charge coupled imaging device for detecting variations in intensity of illumination from a scanning line on the image plane and having electrical contacts adapted to provide side-to-side scanning over the length of the scanning line, the linear charge coupled imaging device comprising from 750 to 2500 storage elements,   3. an optical system for focusing the light reflected from the scanning line onto the linear charge coupled imaging device, the optical system comprising (a) a plurality of long, narrow mirrors of decreasing length for folding the optic path by a factor of at least two, from the image plane to the linear charge coupled imaging device and (b) a lens for forming an image of the scanning line, and   4. electrical circuitry for sequentially reading out each scanning line detected by the linear charge coupled imaging device by forming an electrical signal representative of the variations in intensity of the light reflected from the image plane along a succession of scanning lines, the electrical circuitry comprising: i. logic circuitry for sequential read out of the variations in intensity of light incident upon the linear charge coupled imaging device,   ii. interface circuitry between the logic circuitry and the linear charge coupled imaging device for forming signal levels compatible with the linear charge coupled imaging device and for biasing selected electrodes on the linear charge coupled imaging device, and   iii. amplifying circuitry for amplifying signals generated by the linear charge coupled imaging device and which provide an analog measure of the intensity of light incident upon the linear charge coupled imaging device; and       d. means for mechanically displacing the scanning assembly relative to the material to be copied in a direction parallel to the transparent rigid plate and perpendicular to the scanning line, to permit scanning a succession of equally spaced parallel scanning lines from one end of the image plane to the other. .Iadd. 3. A compact flatbed scanner for facsimile scanning comprising:   (a) a housing;   (b) a transparent plate mounted on the housing for supporting material to be copied, the transparent plate defining the approximate image plane of the material to be copied;   (c) a moving scanning assembly supported within the housing beneath the transparent plate, the scanning assembly comprising: (1) means for mounting at least one lamp for illuminating at least a portion of the image plane,   (2) a linear solid state imaging device for detecting variations in intensity of light reflected from a scanning line on the image plane and having electrical contacts adapted to provide electronic scanning over the length of the scanning line, and   (3) an optical system for focusing the light reflected from the scanning line onto the linear imaging device, the optical system comprising a plurality of long narrow mirrors for folding the optical path from the scanning line to the linear imaging device;   (d) means for mechanically displacing the scanning assembly relative to the image plane in a direction parallel to the image plane and perpendicular to the scanning line to permit scanning a succession of parallel lines from one end of the image plane to the other; and   (e) electrical circuitry for sequentially reading out each scanning line detected by the linear imaging device by forming an electrical signal representative of the variations in intensity of light reflected from the image plane along a succession of scanning lines..Iaddend..Iadd. 4. A scanner as in claim 3 wherein said solid state device comprises a silicon device having multiple light-sensitive elements disposed in a linear array..Iaddend.