SCANNER FOR SCANNING AN ORIGINAL DOCUMENT

Abstract: The invention relates to a mechanical system for guiding the optics (3) and a CCD-scanner section (2) in a scanner for scanning an original, the CCD-section (2) and the optics (3) being controlled in their movement by the same guide rail (4) operated by motors (5 and 7) through spindles (6 and 8). By mounting the spindle (8) and the motor (7) for the optics (3) on the CCD-scanner section (2) it has been made possible to change the reproduction ratio within a predetermined range without changing the lens whilst fully utilizing the optical resolution of the CCD-section.

Description: Scanner for scanning an original document. The invention relates to a scanner for optical scanning an original, more specifically a scanner by which it is possible to change the reproduction ratio of the original in connection with the scanning. Scanners of various types are known and a typic- al representative of such scanners is disclosed in EP patent No. 00366020, according to which the apparatus Includes a linear CCD-unit moved in the focussing plane of a fixed lens for scanning the image of the original generated in the focussing plane. Said scanner suffers, however, from the essen¬ tial drawback that the distance between the CCD-unit and the optical centre of the lens and between the ori¬ ginal and the centre is fixed. In this way, only one reproduction ratio can be achieved with a given lens because a change of the reproduction ratio implies either a change of the lens or use of a zoom-type lens. This implicates, however, that the scanner does not always function so that its optimum resolution is uti¬ lized. The purpose of the invention is to provide a scanner allowing for arbitrarily choosing reproduction ratios within a predetermined range without changing the lens and so that the scanner always functions, to utilize its optimum resolution. This purpose is fulfilled according to the invention by constructing the guide rails of the scanner as specified in the characterizing portion of claim 1. By means of this structure it is possible with one lens system to achieve a large range of reproduc- tion ratios while maintaining the resolution of the scanner. By structuring the mechanical system as speci¬ fied in the characterizing portion of claim 2 the move- ments of at least the second spindle becomes very short, thereby considerably reducing the time of adjustment. The invention will now be described in further detail with reference to the drawing showing a per¬ spective view of the scanner according to the inven¬ tion. The drawing illustrates the most important parts of the scanner comprising mainly an original table 1, a first movable section 2 and a second movable sec¬ tion 3. The movable section 2 is arranged to move perpendicular to the original table 1 and is guided in this movement by the guide rail 4 and driven in this movement by a motor 5 driving a spindle 6. Spindle 6 is in engagement with a nut secured on sec¬ tion 2. This nut is not illustrated in the drawing. Section 3 may likewise be moved in a direction perpendicular to original table 1 guided by guide rail 4 operated by a motor 7 mounted on section 2. Motor 7 operates a spindle 8 engaging a nut 9 mounted on section 3. Section 3 carries an objective 10 for focussing an image of an original 11, placed on the original table, on a CCD-unit 12 forming part of a CCD-module 13 mounted on section 2. This CCD-module will be described in further detail in the following. As it will appear from the above, sections 2 and 3 may be moved in a direction perpendicular to original table 1. This movement is controlled by a common guide rail 4 and the movements are propelled by motors 5 and 7. As a focussing on the CCD-unit of original 11 placed on original table 1 is always wanted, irrespective of the reproduction ratio, there must always be a predetermined relation between the distances between section 3 and original table 1 and section 3 and section 2. Advantage is taken of this acording to the invention by mounting on section 2 the means 7, 8, 9 for determining the distance between sections 2 and 3. This allows for designing motor 7 substantially smaller than motor 5 and thus also less expensive, and at the same time spindle 8 also becomes short, thereby complying with given demands for accuracy. As shown, the CCD-module 13 comprises a CCD- unit 12, a motor 14, a spindle 15 and guiding means 16. Motor 14 serves to displace CCD-unit 12 in the focussing plane of objective 10 by means of spindle 15, thereby allowing for scanning the image of original 11. The printed circuit board 17 on which the CCD- unit is mounted also carries circuits for preprocessing the signals from the CCD-unit. Motors 5, 7 and 14 are all so-called stepper motors and by the utilization of the generally known properties of such motors it is possible to position the individual sections in mutual relationship by counting the number of drive pulses fed to the motors. By controlling sections 2 and 3 by a common guide rail 4 which as shown may include two ver¬ tically positioned parallel H-profiles 18, 19 whose oppositely facing internal rails 20, 21 serve as guide rails for the first section, e.g. unit 3, while the external rails 22, 23 facing away from each other serve as guide rails for the second section, e.g. unit 2, it is achieved that the guiding members, e.g. the wheels 24, 25, for the respective sections 2, 3 can be placed approximately at the same level on guide rails 4, and it is further advantageous that the two sections track with each other if some small cur¬ vilinear or linearity irregularities occur in guide rails 4, thereby ensuring that objective 10 and CCD-unit 12 always occupy the same position in rela¬ tion to each other.

Claims: P A T E N T C L A I M S 1. A scanner for scanning an original and comprising an original table (1), a lens system (10) and a CCD-unit (12), said scanner being of the type in which the scanning is performed by moving the CCD-unit (12) in the focussing plane of the lens system (10), perpendicular to the longitudinal axis of the lens system, characterized in that the lens system (10) and the CCD-unit (12) in dependence on each other are moved along the longitudinal axis of the lens system (10) to obtain different reproduction ratios in such a manner that the light sensistive area of the CCD-unit (12) remains in the focussing plane of the lens system, irrespective of the chosen reproduction ratio. 2. A scanner as claimed in claim 1, charac¬ terized in that the displacement of the CCD-unit (12) along the longitudinal axis of the lens system (10) is controlled by a first spindle (6) stationary with respect to the original table, and that the displace- ment of the lens system (10) along the longitudinal axis of the lens system (10) is controlled by a second spindle (8) secured to the CCD-unit. 3. A scanner as claimed in claims 1 or 2, characterized in that the displacement of the CCD-unit (12) and the lens system (10) along the longitudinal axis of the lens system is controlled by a common guide rail (4). 4. A scanner as claimed in claim 2 or 3, charac¬ terized in that the first and the second spindles (6, 8) are operated by so-called stepper motors (5, 7). 5. A scanner as claimed in claim 3, charac¬ terized in that the common guide rail (4) comprises guide tracks for the CCD-unit (12) and the lens system (10), the guide members (24, 25) associated with the CCD-unit (12) and the lens system (6), respectively, being positioned substantially at the same level in the separate guide tracks (20-23).

Inventors: NIELSEN KAJ O, NIELSEN, KAJ, O.
Applicants: OCE HELIOPRINT AS, HELIOPRINT A/S
Application year: 1989
Main classification: H04N1
IPC codes: H04N1