GB2344013A

GB2344013A - Multiple-resolution scanner

Info

Publication number: GB2344013A
Application number: GB9825186A
Authority: GB
Inventors: Chou-Jiung Lin
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-11-17
Filing date: 1998-11-17
Publication date: 2000-05-24
Anticipated expiration: 2018-11-17
Also published as: GB9825186D0; GB2344013B

Abstract

A multiple-resolution scanner for scanning an object at one of several resolutions has several mirrors 41,42,43 for transmitting light from the scanned object along several distinct light paths. Several lenses 51,52,53,54, which are separately placed in the light paths generate images of the scanned object at the positions of different detectors 61,62,63,64. The detectors generate electrical signals which are fed into a control circuit, either separately or combined, for further processing.

Description

MULTIPLE-RESOLUTION SCANNER BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiple-resolution scanner, particularly to a multiple-resolution scanner which offers at least two resolutions that are switchable without any mechanical movement of lenses.

2. Description of Related Art Conventionally, text and image data of different types are read by scanners of different resolutions and with different scanning areas. For example, normal text is usually read from an area of 297 mm by 210 mm (A4 format) with a resolution of 300 dpi. For color photographs, 4 inches by 6 inches and 600 dpi are regularly used values for size and resolution. Slides and negative films require a resolution of 1200 dpi for satisfactory results, but typically only an area of 24 mm by 36 mm.

Conventional scanners, whether sheet feed scanners or flatbed scanners, aim at only one application for a certain image data type. Many scanners on the market are designed for A4 areas at a comparatively low resolution. For scanning photographs, scanners with a smaller scanned area and higher resolution are available. Scanning of slides is provided by scanners with a scanned area of 24 mm by 36 mm and an even higher resolution. Any user purchasing a scanner needs to consider the intended application and decide which type of scanner is most suitable. For different applications, several scanners are needed, which is not convenient.

For overcoming the deficiency of conventional scanners of only one application, scanners offering multiple resolutions have appeared on the market. For example, Taiwan patent no. 101266"Multiple Lens Switching System@ and Taiwan patent no. 127094"Multiple Lens Switching System for Scanner"disclose multiple resolution image reading systems, wherein, by switching between lenses of various focal lengths, the resolution is varied. The lenses are alternatively moved in front of a single CCD detector, so as to obtain different resolutions.

However, a conventional multiple resolution scanner requires, apart from a plurality of lenses, a mechanism for driving a mechanical movement of the lenses and positioning the lenses as well as enough space to allow the lenses to be switched back and forth.

Therefore a large volume is needed. Movable lenses are also subject to vibrations, leading to scans of reduced quality.

SUMMARY OF THE INVENTION The main object of the present invention is to provide a multiple-resolution scanner with reduced volume, so as to save space.

Another object of the present invention is to provide a multiple-resolution scanner which allows to switch resolutions without mechanically moving the lenses for a simplified structure and an improved quality of scans.

A further object of the present invention is to provide a multiple-resolution scanner which allows to switch between various data types.

The present invention can be more fully understood by reference to the following description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional side view of the scanner of the present invention in the first embodiment.

Fig. 2 (prior art) is a sectional side view of a conventional scanner.

Fig. 3 is a sectional top view of the scanner of the present invention in the first embodiment at the lowest resolution.

Fig. 4 is a sectional side view of the scanner of the present invention in the first embodiment at the lowest resolution, taken along the double-arrowed line in Fig. 3.

Fig. 5 is a sectional top view of the scanner of the present invention in the first embodiment at the second-lowest resolution.

Fig. 6 is a sectional side view of the scanner of the present invention in the first embodiment at the second-lowest resolution, taken along the double-arrowed line in Fig. 5.

Fig. 7 is a sectional top view of the scanner of the present invention in the first embodiment at the second-highest resolution.

Fig. 8 is a sectional side view of the scanner of the present invention in the first embodiment at the second-highest resolution, taken along the double-arrowed line in Fig. 7.

Fig. 9 is a sectional top view of the scanner of the present invention in the first embodiment at the highest resolution.

Fig. 10 is a sectional side view of the scanner of the present invention in the first embodiment at the highest resolution, taken along the double-arrowed line in Fig. 9.

Fig. 11 is a sectional top view of the scanner of the present invention in the second embodiment.

Fig. 12 is a sectional top view of the scanner of the present invention in the third embodiment at the lowest resolution.

Fig. 13 is a sectional side view of the scanner of the present invention in the third embodiment at the lowest resolution, taken along the double-arrowed line in Fig. 12.

Fig. 14 is a sectional side view of the scanner of the present invention in the fourth embodiment.

Fig. 15 is a sectional side view of the scanner of the present invention in the fifth embodiment.

Fig. 16 is a block diagram of the electric circuit of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a multiple-resolution scanner, particularly a multiple-resolution scanner which offers various resolutions for various types of image data, like text on an A4 format, color photographs and films.

As shown in Fig. 2, a conventional single-resolution scanner mainly comprises: a main body 10 with a top side; a carrier 20, mounted on the top side of the main body 10, for carrying a scanned object 21; a scanning device 30, which is movable within the main body 10 along the longitudinal axis and running parallel to the carrier 20; and a rail 11 for guiding the scanning device 30 along the longitudinal axis.

The carrier 20 has a transparent plate 22 and a cover 23 for covering the transparent plate 22 and holding the scanned object 21 thereon. The scanned object 21 is a text or image sheet. The scanning device 30 comprises a casing 31, a mirror group 40, a lens 57, a detector 67, a first optical output area 85, and a first light source 70.

The mirror group 40 consists of several different mirrors. Light 71 generated by the first light source 70 illuminates the scanned object 21, is reflected therefrom and subsequently reflected on the mirrors of the mirror group 40 towards the lens 57. The lens 57 generates through the first optical output area 85 an optical image of the scanned object 21 on the detector 67, where an electrical signal is generated according to the intensity distribution of the optical image.

Referring to Figs. 1 and 3-10, the present invention in the first embodiment offers various resolutions, a lowest, a second-lowest, a second-highest, and a highest resolution. In contrast to the conventional scanner described above, in the present invention in the first embodiment the scanning device 30 comprises a casing 31, a mirror group 40, a lens group 50, and a detector group 60. The first light source 70 is mounted on the casing 31.

The mirror group 40 consists of mirrors 41,42,43 and 44. The lens group 50 consists of lenses 51,52,53, 54 with different focal lengths. The detector group 60 consists of four detectors 61,62,63,64 which are located in the same transverse positions as the lenses 51,52,53,54 respectively Light 71 generated by the first light source 70 illuminates the scanned objects 21, is reflected therefrom and subsequently reflected on the mirrors 41, 42,43,44 of the mirror group 40, proceeding on various light paths. The lenses 51,52,53,54 of the lens group 50 have mutually different focal lengths to obtain the four different resolutions. Thus the lenses 51,52,53,54 of the lens qroup 50 require different light paths and optical distances to the scanned objected 21 to produce optical images thereof on the detectors 61,62,63,64 of the detector group 60. The mirrors 41,42,43,44 of the mirror group 40 provided for the various light paths. The lenses 51,52,53,54 of the lens group 50 are positioned in the various light paths and generate on various locations optical images of the scanned object 21 on the detectors 61,62, 63,64 of the detector group 60, from where electrical signals are generated.

Usually, scanned objects with a relatively large area, like text sheets and large images, need only relatively low resolutions, whereas scanned objects that require-relatively high resolutions, like photographs and films, are smaller. The lens 51 of the lens group 50 provides the lowest resolution and is located in a middle transverse position inside the casing 31. In this position, the lens 51 generates an image of an object in a symmetrical transverse position on the carrier 20, being able to cover fully the width of the carrier 20 and to create an image of a large scanned object 21. For the second-lowest, the second-highest and the highest resolution, the scanned object 21 is smaller, taking less than the full width of the carrier 20. The lenses 52,53,54 are designed to create images of smaller scanned objects 21 at the second-lowest, second-highest and highest resolutions and are mounted to the two sides of the lens 51, covering only partly the width of the carrier 20, which is sufficient.

Referring to Figs. 3 and 4, in the lowest resolution, light from the scanned object 21 passes through the mirrors 41,42,43,44, as indicated by dashed lines. The dashed lines in Fig. 3 show the width covered by all light rays that are reflected from the scanned object 21, proceed to the lens 51 and leave the lens 51 as a first optical output 81. The lens 51 generates an optical image of the scanned object 21 on the detector 61. In the lowest resolution, the first optical output area 85 is covered by light rays that have passed through the lens 51.

Referring to Figs. 5 and 6, in the second-lowest resolution, light from the scanned object 21 passes through the mirrors 41,42,43,44, proceeds to the lens 52 and leaves the lens 52 as a second optical output 82. The lens 52 generates an optical image of the scanned object 21 on the detector 62. In the second-lowest resolution, the first optical output area 85 is covered by light rays that have passed through the lens 52.

Referring to Figs. 7 and 8, in the second-highest resolution, light from the scanned object 21 passes through the mirrors 41,42,43,44, proceeds to the lens 53 and leaves the lens 53 as a third optical output 83. The lens 53 generates an optical image of the scanned object 21 on the detector 63. In the second-highest resolution, the second optical output area 86 is covered by light rays that have passed through the lens 53.

Referring to Figs. 9 and 10, in the highest resolution, light from the scanned object 21 passes through the mirrors 41,42,43,44, proceeds to the lens 54 and leaves the lens 54 as a fourth optical output 84. The lens 54 generates an optical image of the scanned object 21 on the detector 64. In the highest resolution, the second optical output area 86 is covered by light rays that have passed through the lens 54.

The detectors 61,62,63,64 of the detector group 60 are linear charge-coupled devices. Linear charge-coupled devices detect a light intensity distribution along a one-dimensional line at a time. To cover the full area of the scanned object 21 a driving system (not shown) moves the scanned object 21, like in a sheet feed type scanner, or the scanning device 30, like in a flatbed type scanner, in steps of a certain width. The width of these steps has to fit the resolutions used. For example, for a given resolution, say 1/300 dpi, the step width will be equal to the distance of neighboring pixels at that resolution, i. e., 1/300 inch. To simplify control of the driving system, the various resolutions are arranged at proportions of small integer numbers or as multiples of each other, like 400 dpi, 600 dpi, 1200 dpi and 2400 dpi, or, 300 dpi, 600 dpi, 1200 dpi and 2400 dpi. Accordingly, the lenses 51,52,53,54 of the present invention operate at resolutions of similar proportions.

The main characteristic of the present invention is the use of four detectors 61,62,63,64. The detectors 61, 62,63,64 are mounted at the same transverse positions as the lenses 51,52,53,54 respectively, receiving light coming along the optical outputs 81,82,83,84, respectively. So for each resolution a separate detector is employed.

Referring to Fig. 16, a multiplexer 90 controls the detectors 61,62,63,64, passing the electrical signals from at least one of the detectors 61,62,63, 64 to an image processing unit 91. The image processing unit 91 is connected to a host computer 92 for further processing, a user interface 93 for user control, and a drive system 94 for driving the scanning device 30 or the scanned object 21.

The multiplexer 90 is operated manually by direct user commands via the user interface 93 or automatically by software running on the host computer 92. Furthermore, the multiplexer 90 is usable as a direct switch for selecting the detectors 61,62,63, 64, as required.

Since the lenses 51,52,53,54 of the present invention generate optical images with different resolutions on the separate detectors 61,62,63,64, switching the different resolutions is accomplished by merely electrically controlling the detectors 61, s2, 63,64 using the multiplexer 90. No mechanical movement of the lenses 51,52,53,54 is required to switch the resolutions. No space and no mechanical driving system for moving the lens group 50 need to be provided, simplifying the scanning device 30 and reducing the size thereof. The lenses 51, 52,53,54 stay in fixed positions, ensuring a stable optical setup and high scanning quality.

Referring to Fig. 11, the multiple-resolution scanner of the present invention in a second embodiment has a lens group 50A with a lens 51A for a high resolution, placed in a middle transverse position with respect to the carrier 20, and lenses 52A, 53A with low resolutions placed on both transverse sides of the lens 51A. The lens 51A is used for scanning an object of relatively small width at the high resolution. The lenses 52A, 53A are used for scanning an object of relatively large width at the low resolution.

Furthermore, in the second embodiment of the present invention the lenses 52A and 53A are designable to have equal focal lengths for each scanning one half of the width of the carrier 20. Then the lenses 52A, 53A together cover the whole width of the carrier 20. The images scanned using the lenses 52A, 53A are registered in detectors 62A, 63A, the output signals of which are afterwards combined electronically to yield a single image.

Referring to Figs. 12 and 13, the multiple-resolution scanner of the present invention in a third embodiment has a mirror group 40B, consisting of mirrors 41B, 42B, 43B, a lens group 50B, consisting of lenses 51B, 52B, 53B, 54B with different focal lengths for various resolutions, and a detector group 60B, consisting of detectors 61B, 62B, 63B, 64B. Figs.

12 and 13 show the present invention in the third embodiment while reading the scanned object 21 at the lowest resolution. Light 71 generated by the first light source 70 illuminates the scanned object 21, is reflected therefrom onto the mirrors 41B, 42B, 43B of the mirror group 40B and subsequently on the lens 51B of the lens group 50B. The lens 51B generates an optical image of the scanned object 21 on the detector 61B. In the lowest resolution, a first active optical area 85B is covered by light rays that have passed through the lens 51B.

Referring to Fig. 14, the multiple-resolution scanner of the present invention in a fourth embodiment has a light generator 25, replacing the cover 23 of the first embodiment. Inside the light generator 25, a second light source 72 is mounted, which moves longitudinally along with the scanning device 30. The second light source 72 generates transmission light 73, which passes through a scanned transparent object 24 on the transparent plate 22 of the carrier 20. The light is then reflected by the mirror group 40, passes through the lens group 50 and is registered by the detector group 60 according to the transparency distribution on the scanned transparent object 24.

Referring to Fig. 15, the multiple-resolution scanner of the present invention in a fifth embodiment has a light generator 25 with a light box 74. The light box 74 is an extended light source, which is not movable. The light box 74 generates transmission light 75, which passes through the scanned transparent object 24 allowing to scan the scanned transparent object 24.

While the invention has been described with reference to preferred embodiments thereof, it is to be understood that modifications or variations may be easily made without departing from the spirit of this invention which is defined by the appended claims.

Claims

1. A multiple-resolution scanner for scanning a scanned object at one of several resolutions and electronically transmitting a digital image of said scanned object, said multiple-resolution scanner comprising: a mirror group having at least one mirror for reflecting light coming from said scanned object along several distinct light ; a lens group having several lenses, one of said lenses placed in each of said light paths, for generating images of said scanned object at several image ; a detector group having several detectors, one of said detectors placed at each of said image positions, said detectors generating electrical signals; and at least one optical output area; wherein each of said detectors corresponds to one and only one of said lenses, receiving light therefrom covering one of said at least one optical output area.

2. A multiple-resolution scanner according to claim 1, wherein said lenses generate images at different resolutions, with a high resolution lens located in a central position and generating an image with maximum resolution.

3. A multiple-resolution scanner according to claim 1, wherein said lenses generate images at different resolutions, with a low resolution lens located in a central position and generating an image with minimum resolution.

4. A multiple-resolution scanner according to claim 1, wherein said lenses generate images at different resolutions, which are related to each other like small integer numbers.

5. A multiple-resolution scanner according to claim 1, further comprising at least one first light source generating reflection light, which illuminates said scanned object and is reflected therefrom onto said mirror group according to a reflectivity distribution on said scanned object.

6. A multiple-resolution scanner according to claim 1, further comprising at least one first light source generating transmission light, which illuminates said scanned object and is transmitted therefrom onto said mirror group according to a transparency distribution on said scanned object.

7. A multiple-resolution scanner according to claim 1, further comprising a switching device passing said electrical signals of at least one of said detectors to an image processing unit for further processing.

8. A multiple-resolution scanner according to claim 7, wherein said electrical signals of at least two of said detectors are combined to signals of a single image.

9. A multiple-resolution scanner according to claim 7, wherein said switching device is a multiplex controller between said detector group and said signal processing unit.

10. A multiple-resolution scanner according to claim 9, wherein said multiplex controller is a control switch.

11. A multiple-resolution scanner according to claim 9, wherein said multiplex controller controls in a process.

12. A multiple-resolution scanner according to claim 7, wherein said switching device is controlled by a push-button.

13. A multiple-resolution scanner according to claim 1, wherein said mirror group, said lens group and said detector group are mounted in a scanning device, which is linearly movable along said scanned object.

14. A multiple-resolution scanner according to claim 13, wherein said lenses generate images at different resolutions, with a high resolution lens located in a central position and generating an image with maximum resolution.

15. A multiple-resolution scanner according to claim 13, wherein said lenses generate images at different resolutions, with a low resolution lens located in a central position and generating an image with minimum resolution.

16. A multiple-resolution scanner according to claim 13, wherein said lenses generate images at different resolutions, which are related to each other like small integer numbers.

17. A multiple-resolution scanner according to claim 13, further comprising at least one first light source generating reflection light, which illuminates said scanned object and is reflected therefrom onto said mirror group according to a reflectivity distribution on said scanned object.

18. A multiple-resolution scanner according to claim 13, further comprising at least one first light source generating transmission light, which illuminates said scanned object and is transmitted therefrom onto said mirror group according to a transparency distribution on said scanned object.

19. A multiple-resolution scanner according to claim 18, wherein said second light source moves along with said scanning device.

20. A multiple-resolution scanner according to claim 18, wherein said second light source is a light box.

21. A multiple-resolution scanner according to claim 13, further comprising a switching device passing said electrical signals of at least one of said detectors to an image processing unit for further processing.

22. A multiple-resolution scanner according to claim 21, wherein said electrical signals of at least two of said detectors are combined to signals of a single image.

23. A multiple-resolution scanner according to claim 21, wherein said switching device is a multiplex controller between said detector group and said signal processing unit.

24. A multiple-resolution scanner according to claim 23, wherein said multiplex controller is a control switch.

25. A multiple-resolution scanner according to claim 23, wherein said multiplex controller controls in a process.

26. A multiple-resolution scanner according to claim 21, wherein said switching device is controlled by a push-button.