GB2325532A

GB2325532A - Optical scanner

Info

Publication number: GB2325532A
Application number: GB9710382A
Authority: GB
Inventors: Henry Peng; Kevin Yang
Original assignee: Umax Data System Inc
Current assignee: Veutron Corp
Priority date: 1997-05-19
Filing date: 1997-05-20
Publication date: 1998-11-25
Also published as: AU685728B1; GB9710382D0

Abstract

An optical scanner with an auto-focus mechanism includes a lens moving member 30 for adjusting the position of the lens set 6 of the scanner; a CCD moving member 40 for adjusting the position of the CCD 7 of the scanner; and a control unit 50 for controlling the lens moving member and the CCD moving member. By scanning a reference object, 60 the control unit 50 analyzes the image data of the object and calculates optimized length of light path and best focus condition. By referring the result of the calculation, the control unit controls the lens moving means 30 and the CCD moving means 40 to move the lens set 6 and the CCD 7 respectively to an optimized position such that the optimized length of light path and best focus condition are achieved, and a high resolution image with satisfactory scanning quality is acquired.

Description

AUTO-FOCUS MECHANISM This invention relates to an auto-focus mechanism for an optical scanner, and more particularly to an auto-focus mechanism which can automatically adjust the positions of the lens set and CCD of the scanner so as to obtain a satisfactory scanning result.

Nowadays the office automation (OA) is becoming more and more popular in our society with such vastly-expanding information. In addition to the use of computer to deal with daily information, optical scanner is also considered as a powerful tool since it provides a fast and convenient way to input and manage data such like documents, drawings, photographs, and so on. It has become a trend to take the optical scanner as an inevitable associate equipment of computer.

Conventional optical scanner usually employs a set of lens units with different magnification ratios to fulfill the need for scanning original documents with different sizes. Referring to FIG. 1A, which illustrates an embodiment of such conventional optical scanner, a lens set 93 having two lens units 94, 95 (each with different magnification ratio) is switched to move along a direction perpendicular to the light path of scanner when different sized original documents are to be scanned. Depending on the size of the original document 92, a suitable lens unit 94 with appropriate magnification ratio is switched to locate at a focusing position so as to acquire an accurate image of the document 92 formed on a CCD 91.

Although the lens units 94, 95 are designed to have same length of total light path, however, it is still inevitable to have some error during the manufacturing or assembling processes of the lens set 93 as well as the lens units 95, 95. As a result, when the lens set 93 is switched to locate the other lens unit 95 at the focusing position (as shown in FIG. 1B), an unclear image of the document 92 will be obtained since the error causes a poor focusing condition of the scanner.

Conventional optical scanners usually tolerate such kind of error, which means, they do nothing about the poor scanning result. However, as the need of high resolution and quality of the optical scanner is rapidly progressing in recent years, consumers are no longer willing to suffer such a poor scanning quality especially when they are purchasing a high-end product of optical scanner with a resolution of 600*1200 dpi or above. Any error occurred in the focusing condition or the length of total light path of such a highresolution scanner will be not only crucial but also critical. Of course, this is possible to correct such kind of error by disassembling the scanner and readjusting the positions of the lens units 94, 95 as well as the CCD 91.

However, it is rather obvious that having the scanner being disassembled and readjusted is not only very difficult and laborious, but also requires professional technicians to do such kind of correction, and therefore leaves a room for further improvements.

In view of the aforesaid limitations of conventional optical scanners, it is therefore an object of the present invention to provide an auto-focus mechanism for an optical scanner. The auto-focus mechanism is capable of automatically moving the lens set and the COD of the scanner to appropriate locations so as to acquire desirable focus condition and length of the total light path of the scanner. High resolution and satisfactory quality of scanning result can thus be achieved.

It is another object of the present invention to provide an auto-focus mechanism for an optical scanner. The auto-focus mechanism includes: a lens moving member for adjusting the position of the lens set of the scanner; a COD moving member for adjusting the position of the COD of the scanner; and a control unit for controlling the lens moving member and the COD moving member. By scanning a reference object, the control unit analyzes the image data of the object and calculates optimized length of light path and best focus condition. By referring the result of the calculation, the control unit controls the lens moving means and the COD moving means to move the lens set and the COD respectively to an optimized position so as to fulfill the requirements of the optimized length of light path and the best focus condition.

Furthermore, the reference object mentioned above may be a focus adjusting standard chart located on a document window glass of the optical scanner in such a manner that when the optical scanner is under a standby condition, the focus adjusting standard chart is positioned at an appropriate scanning position such that the process of scanning the chart and calculating the optimized length of light path and focus condition can be rapidly proceeded before normal scanning process starts.

It is yet another object of the present invention to provide an auto-focus mechanism for an optical scanner. The auto-focus mechanism includes: a lens moving member for adjusting the position of the lens set of the scanner, a COD moving member for adjusting the position of the COD of the scanner, and a control unit for controlling the lens moving member and the COD moving member. The COD moving member includes: a drive member, a lead screw furnished along a direction parallel to the light path of the scanner, a transmission member connecting the drive member and the lead screw for transmitting the output of drive member to the lead screw, and a rack for supporting the CCD. The rack is mounted on the lead screw in such a manner that when the drive member drives the lead screw to rotate, the rack together with the CDD thereon can be moved along the direction parallel to the light path.

It is yet a further object of the present invention to provide an autofocus mechanism for an optical scanner. The auto-focus mechanism includes: a lens moving member for adjusting the position of the lens set of the scanner, a COD moving member for adjusting the position of the COD of the scanner, and a control unit for controlling the lens moving member and the COD moving member. The lens moving member comprises: a drive member, a lead screw furnished along a direction parallel to the light path of the scanner, a transmission member connecting the drive member and the lead screw for transmitting the output of the drive member to the lead screw, and a chassis for supporting the lens set. The chassis is mounted with the lead screw in such a manner that when the drive member drives the lead screw to rotate, the chassis together with the lens set can be moved along the direction parallel to the light path.

The foregoing features of the present invention may be more fully understood from the following detailed description, read in conjunction with the accompanying drawings, wherein: FIGs. 1A and 1B are schematic views illustrating two different image forming situations of a conventional optical scanner.

FIG. 2 is a perspective and partial exploded view of an optical scanner with an auto-focus mechanism in accordance with a preferred embodiment of the present invention.

FIG. 3 is a flow diagram illustrating the processes for adjusting the positions of the lens set and the OOD of the present invention.

Referring to FIG. 2, the optical scanner 1 in accordance with a preferred embodiment of the present invention comprises: an upper light source 3 and a lower light source 2 for emitting light, a document window glass 4 for carrying an object being scanned (not shown in figures), a reflection means 5, a lens set 6, a charge coupled device (CCD) 7 and a main body for carrying all aforesaid elements. The light emitted by the light sources 2 and 3 passes through (or is reflected by) the object on the document window glass 4, and then enters the reflection means 5. By the reflection and re-direction of the reflection means 5, the light passes through the lens set 6 and images on the COD 7, which substantially forms a light path from the object to the COD 7. The COD 7 then transforms the image into digital image data and transmits the image data to a remote computer (not shown in figures) for further processes. The lens set 6 includes a first lens unit 8 and a second lens unit 9, wherein each of the lens units 8 and 9 has a different magnification ratio. By employing a lens switching means 20 to switch the lens set 6 along a direction perpendicular to the light path, the lens units 8 and 9 can be either moved in or out of a focusing position along the light path so as to fulfill the need for scanning objects with different sizes and different resolution qualities.

The lens switching means 20 includes a lens support member 21 for supporting the lens units 8 and 9. Both sides of the lens support member 21 are movably furnished with a guide rod 22 respectively along a direction perpendicular to the light path such that the lens support member 21 and the lens units 8 and 9 thereon can be moved along the direction perpendicular to the light path, and thus perform the function of switching the lens units 8 and 9.

The auto-focus mechanism according to the present invention includes: a lens moving means 30 for adjusting a position of the lens set 6 along the light path, a COD moving means 40 for adjusting a position of the COD 7 along the light path, and a control unit 50 for analyzing an image data from the COD 7 and controlling the functions of the lens moving means 30 and the CCD moving means 40. The image data from the COD 7 can be obtained by scanning a reference object 60, which may be a focus adjusting standard chart, located on the document window glass 4. In addition, the location of the reference object 60 on the document window glass 4 is in such a manner that when the optical scanner 1 is under a standby condition, the reference object 60 is located right at an appropriate scanning position such that the processes of scanning the reference object 60 and analyzing its image data can be rapidly proceeded before normal scanning operation being started. By scanning the reference object 60, the control unit 50 calculates an optimized length of total light path and the best focus condition by analyzing the image data of the reference object 60. Basing on the result of the calculation, the control unit 50 controls the lens moving means 30 and the COD moving means 40 to move the lens set 6 and the COD 7 respectively to an optimized position such that the optimized length of light path and best focusing condition can be obtained, and the high resolution and satisfactory scanning quality can thus be achieved.

The lens moving means 30 includes: a first drive means 31 which is preferably a rotary motor, a first lead screw 33 furnished along a direction parallel to the light path, a first transmission means 32 connecting the first drive means 31 and the first lead screw 33 for transmitting the output of the first drive means 31 to the first lead screw 33, and a chassis 34 for supporting the lens set 6. The chassis 34 is movably mounted with the first lead screw 33 such that when the first drive means 31 drives the first lead screw 33 to rotate, the chassis 34 together with the lens set 6 thereon can be moved along a direction parallel to the light path. A first guide rod 35 and a second guide rod 36 are provided at two sides of the chassis 34 respectively along a direction parallel to the light path so as to provide better stability and balance when the chassis 34 is driven by the first drive means 31.

The COD moving means 40 includes: a second drive means 41 which is preferably a rotary motor, a second lead screw 43 furnished along a direction parallel to the light path, a second transmission means 42 connecting the second drive means 41 and the second lead screw 43 for transmitting the output of the second drive means 41 to the second lead screw 43, and a rack 44 for supporting the CCD 7. The rack 44 is movably mounted on the second lead screw 43 such that when the second drive means 41 drives the second lead screw 43 to rotate, the rack 44 together with the COD 7 thereon can be moved along the direction parallel to the light path.

Referring to FIG. 3, which is a flow diagram illustrating the processes for adjusting the positions of the lens set 6 and the COD 7. As shown in block 61, when a user turns on the optical scanner 1 or switches the lens set 6 to locate any one of the lens units 8 and 9 at a focusing position, the reference object 60 will also locate at a position for scanning since the optical scanner 1 is under a standby condition. Firstly, the optical scanner 1 pre-scans the reference object 60 rapidly (as shown in block 62) to obtain an image data which is transmitted to the control unit 50 for analyzing, 'as shown in block 63. If the control unit 50 determines the image data to be acceptable (i.e., with satisfactory resolution and quality), as shown in block 64, then the control unit 50 sends out a signal informing that the optical scanner 1 is ready for proceeding nonnal scanning operation (as shown in block 65). As shown in block 71, if the control unit 50 determines the image data to be unacceptable (e.g., not clear enough), then the control unit 50 will control the lens moving means 30 to move the lens set 6 for a small distance, as shown in block 72. The reference object 60 is then rapidly scanned once again, as shown in block 73, and the second image data of the reference object 60 is analyzed once again by the control unit 50. By comparing and analyzing these two image data, the control unit 50 can calculate the optimized length of total light path and focus condition for scanning, as shown in block 74. The control unit 50 then controls both the lens moving means 30 and the COD moving means 40 to adjust the lens set 6 and OCD 7 respectively to an appropriate position where the optimized length of total light path and focus condition are achieved, as shown in block 75. The control unit 50 then sends out a signal informing that the optical scanner 1 is now ready for proceeding normal scanning operation, as shown in block 65.

Therefore, a high resolution image with satisfactory scanning quality can be acquired.

Although certain specific embodiment of the present invention has been shown and described above, it is to be understood that many modification thereof are possible. For example, although the lens set 6 shown in FIG. 2 includes two lens units 8 and 9, however, it is rather obvious that any person with ordinary skill would easily apply more than two lens units or only one lens unit onto the lens set 6. In addition, the light sources 2 and 3 can also be easily replaced by using only one light source. The present invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

Claims

We claim:

1. An auto-focus mechanism for an optical scanner having a document window glass for carrying an object to be scanned, a lens set, a charge coupled device (CCD), and a light source for illuminating said object with a light beam defining a light path from said object to said CCD, whereby an image of said object is formed on the COD and is transformed into digital image data; said auto-focus mechanism comprising: a lens moving means for adjusting a position of the lens set along the light path; a COD moving means for adjusting a position of the COD along the light path; and a control unit for analyzing the image data from the COD and controlling said lens moving means and said COD moving means; wherein, by scanning a reference object, the control unit calculates optimized length of light path and best focus condition by analyzing the image data of the reference object such that, basing on the result of the calculation, said control unit controls the lens moving means and the COD moving means to move the lens set and the COD respectively to an optimized position so as to fulfill the requirements of the optimized length of light path and focus condition.

2. The auto-focus mechanism of claim 1, wherein said COD moving means comprises: a drive means; a lead screw furnished along a direction parallel to the light path; a transmission means connecting said drive means and said lead screw for transmitting the output of drive means to the lead screw; and a rack for supporting the CCD; said rack being movably mounted on said lead screw such that when the drive means drives the lead screw to rotate, the rack together with the COD thereon is moved along the direction parallel to the light path.

3. The auto-focus mechanism of claim 2, wherein said drive means is a motor.

4. The auto-focus mechanism of claim 1, wherein said lens moving means comprises: a drive means; a lead screw furnished along a direction parallel to the light path; a transmission means connecting said drive means and said lead screw for transmitting the output of the drive means to the lead screw; and a chassis for supporting the lens set; said chassis being movably mounted with said lead screw such that when the drive means drives the lead screw to rotate, the chassis together with the lens set is moved along the direction parallel to the light path.

5. The auto-focus mechanism of claim 4, wherein said drive means is a motor.

6. The auto-focus mechanism of claim 4 further comprising two guide rods provided at two sides of the chassis along a direction parallel to the light path so as to provide better stability and balance when the chassis is driven by the drive means.

7. The auto-focus mechanism of claim 1 further comprising a lens switching means having a lens support member for supporting the lens set; said lens set comprising a plurality of lens units fixedly mounted on said lens support member; both sides of the lens support member being movably furnished with a guide rod perpendicular to the light path such that the lens support member and the lens units thereon are movable along the guide rods to perform a function of switching the lens units.

8. The auto-focus mechanism of claim 1, wherein said lens set comprises one lens unit.

9. The auto-focus mechanism of claim 1, wherein said lens set comprises two lens units.

10. The auto-focus mechanism of claim 1, wherein said lens set comprises more than two lens units.

11. The auto-focus mechanism of claim 1, wherein said reference object is a focus adjusting standard chart located on said document window glass in such a manner that when the optical scanner is under a standby condition, said focus adjusting standard chart is positioned at an appropriate scanning position such that the process of scanning the chart and calculating the optimized length of light path and focus condition can be rapidly proceeded before normal scanning process starts.

12. An auto-focus mechanism for an optical scanner comprising a document window glass for carrying an object to be scanned, a lens set having a plurality of lens units, a charge coupled device (CCD), and a light source for illuminating said object with a light beam defining a light path from said object to said CCD, whereby an image of said object is formed on the COD and is transformed into digital image data; said auto-focus mechanism comprising: a lens switching means for switching said lens units along a direction perpendicular to the light path; a lens moving means for adjusting a position of the lens set along the light path; a COD moving means for adjusting a position of the COD along the light path; a focus adjusting standard chart furnished on said document window glass at an appropriate location such that said focus adjusting standard chart is right positioned at a scanning position when the optical scanner is under a standby condition; and a control unit for analyzing the image data from the COD and controlling said lens moving means and said COD moving means; when said lens switching means switches the lens units, the optical scanner automatically scans the focus adjusting standard chart obtaining an image data of said chart being transmitted to said control unit; the control unit then calculates optimized length of light path and best focus condition by analyzing the image data such that, basing on the result of the calculation, said control unit controls the lens moving means and the COD moving means to move the lens set and the COD respectively to an optimized position so as to fulfill the requirements of the optimized length of light path and focus condition.

13. The auto-focus mechanism of claim 12, wherein said COD moving means comprises: a drive means; a lead screw furnished along a direction parallel to the light path; a transmission means connecting said drive means and said lead screw for transmitting the output of drive means to the lead screw; and a rack for supporting the CCD; said rack being movably mounted on said lead screw such that when the drive means drives the lead screw to rotate, the rack together with the COD thereon is moved along the direction parallel to the light path.

14. The auto-focus mechanism of claim 12, wherein said lens moving means comprises: a drive means; a lead screw furnished along a direction parallel to the light path; a transmission means connecting said drive means and said lead screw for transmitting the output of the drive means to the lead screw; and a chassis for supporting the lens set; said chassis being movably mounted with said lead screw such that when the drive means drives the lead screw to rotate, the chassis together with the lens set is moved along the direction parallel to the light path.