DE102008046436A1 - Scanned image information dissolution raising method, involves moving line sensor in longitudinal direction of sensor row offset to position of line sensor during passage relative to object in scanning device - Google Patents

Abstract

The invention relates to a method for increasing the resolution of scanned image information by means of a line sensor (1), in which an object (3) to be scanned with a line sensor (1) moved relative to the object is detected by the line sensor (1) in each case successively and at a constant scanning speed (V) line by line images (4) of the object (3) detected. In such a method, the line sensor (1) detects in a first pass the images (4) of the object (3) in the scanning direction (7) transversely to the sensor line (8) of the line sensor (1) at a fraction of the usual scanning speed (V ) reduced scan speed (V '), wherein the first pass is followed by at least one further pass, wherein the line sensor (1) in the longitudinal direction (6) of the sensor line (8) offset from the position of the line sensor (1) at the first Dur7) moves becomes.

Description

The The invention relates to a method of increasing the resolution of scanned images Image information using a line sensor according to the preamble of claim 1 and a corresponding device according to the preamble of claim 15.

The Optical detection of objects and in particular of planar templates like books, Pictures, texts or the like is usually carried out by means of so-called. Scanners or scanner backs for cameras. One Such scanner has an imaging optics, on the an image of the object to be scanned on the image plane of the imaging optics projected and there by means of a digital image capture device is detected. As image capture device come arrangements of photosensitive elements, often in the form of so-called CCD elements used.

such CCD elements can be arranged two-dimensionally in a plane, then act they are so-called CCD arrays. Also be arranged linear Used line sensors in which the photosensitive elements be arranged side by side in only one row. Come too so-called trilinear line sensors are used, in which usually three on the colors red / green / blue Reactive photosensitive elements next to each other at a small distance each arranged in line form. Such line sensors have the advantage of being much less expensive than array sensors are and for many purposes, such as scanning stationary objects are sufficient.

The Scanning of objects is done with such line sensors usually by means of a relative movement between object and line sensor, where either the object or the line sensor or both be moved relative to each other. The relative movement takes place usually with a constant relative speed along a linear path such that by the relative speed and the readout speed of the line sensor possible gain square pixels of the object image. The scanning movement is usually executed transverse to the extension of the line sensor, whereby the line sensor in the course of the scan, the entire object image passes through successively.

The results in this approach achievable resolution of the object image primarily from the relative speed of the movement between object and line sensor as well as the readout speed of the line sensor. To increase the resolution the image of the object in the scanning direction and thus usually perpendicular to the longitudinal extent of the line sensor, it is known the speed of the relative movement across from the usual To reduce relative speed. This will be at either gradual or continuous execution of the relative movement a higher Number of pixel lines in the scanning scanning direction is reached, being the resolution with a bigger reduction The scan speed can be increased more and more. Due to the constant physical resolution of the line sensor in the longitudinal direction the sensor line is the resolution independent in this direction from the scan speed and thus not influenced. Therefore becomes at an increase in resolution as above achieved in Scanning direction the object image across the scanning direction by software method interpolated to increase in both directions resolution to reach. However, this has the disadvantage that through the interpolation Although the image of the object transversely to the scanning direction increases the resolution, the Overall, however, the object image is degraded.

task The present invention is therefore a method and a to propose appropriate device with which an increase in the resolution a scanned with a line sensor object image simple and inexpensive both can be achieved in the scanning direction as well as transversely to the scanning direction.

The solution the task of the invention arises in terms of the method of the characterizing Features of claim 1 and in terms of the device the characterizing features of claim 15 in cooperation with the characteristics of the associated Preamble. Further advantageous embodiments of the invention emerge from the dependent claims.

The invention is based on a method for increasing the resolution of scanned image information with the aid of a line sensor in which an object to be scanned with a line sensor moved relative to the object is detected by the line sensor successively and at a constant scan speed line by line images of the object detected. Such a method is further developed in that, in a first pass, the line sensor detects the images of the object in the scanning direction transversely to the sensor line of the line sensor at a scan speed reduced to a fraction of the usual scan speed and at least one further pass follows the first pass the line sensor is moved in the longitudinal direction of the sensor line offset from the position of the line sensor during the first pass relative to the object in the scanning direction. By reducing the scan speed on the first pass, the up achieved solution of the object image in the scanning direction, whereas moved by the offset of the line sensor for another pass or more passes, the object is moved again by the offset and thereby results in a physically determined further and shifted to the image of the first pass image of the object. If the offset between the path of the line sensor during the first pass and the further pass is a fraction of the distance between photosensitive elements arranged adjacent to one another in the sensor line of the line sensor, additional information about the image of the object is obtained. This additional information can be suitably combined with the data of the object image from the first pass in such a way that an increase in the resolution of the object image due to actual additional information also results in the direction of the sensor line of the line sensor. It is therefore possible with the method according to the invention to achieve a physical increase in the resolution of the object image without an increase in the physical, already severely limited resolution of the line sensor, which also substantially determines the price of the line sensor. For this purpose, either the object or the line sensor between successive passes in the direction of the sensor line of the line sensor to each other by a fraction of the fixed predetermined distance between adjacent in the sensor array of the line sensor arranged photosensitive elements and scanned the object again. These two or more scanned images of the object are then sorted by appropriate sorting and taking into account each set offset and thereby give an image of the object with increased resolution in both directions. By only a simple additional adjustment between object and line sensor in the direction of the sensor line of the line sensor, the object image obtained can be substantially and evenly improved.

From The advantage here is if the further pass or the other runs also be performed at this reduced scan speed. Thus, the points determined in the individual runs are of the object image offset by the offset side by side, if the repeat accuracy of the scanner is correspondingly high, and sorting the data of the object images of the individual passes especially easy. It is advantageous here, if the fraction the usual Scan speed is an integer fraction of the usual Scanning speed is. Such an integer ratio allows a simple prescription for the desired resolution increase, wherein about a halving of the scan speed doubling the resolution in the scan direction. This is especially true even if the further run or the further runs also with the integer fraction the usual Scanning speed performed become.

Farther it is advantageous if the offset of the line sensor in the direction the sensor line is an integer fraction of the distance between adjacent photosensitive elements of the sensor line. hereby is achieved that each photosensitive element of the sensor line indeed additional Information in the further pass takes in the image of the object from the first pass were missing. pictorially spoken take the photosensitive elements of the sensor line exactly the intermediate areas between the already recorded lines of the Object image on the first pass due to the limited physical resolution of the line sensor could not be detected. But that will be indeed new information for the improved image of the object won, which otherwise only one by an increase the physical resolution correspond to the achievable improvement of the line sensor. It is of course also possible that several passes of scanning under setting each time a new offset between line sensor and object are performed and thus several additional, each offset images of the object between the given imaging paths during the first pass of the line sensor be won. This would be the fractional factors of the distance between adjacent photosensitive Selected elements of the sensor line, that the distance between the recorded image information when first passage through appropriately arranged therebetween image information filled becomes.

From The advantage here is when the offset of the line sensor related on the distance between adjacent photosensitive elements of Sensor line in the direction of the sensor line in the ratio of the same integer Fraction as the fraction of the reduced scan speed relative to the usual Scanning speed is done. This will cause the resolution of the Object image in both imaging directions evenly increased and the obtained pixels remain substantially square.

After carrying out the at least two passes carried out as described above, the results of the first pass and the results of the further pass or further passes are advantageously offset against each other and sorted into an overall image of the object with increased resolution compared to the physical resolution of the line sensor. This can be simpler Algorithms and therefore be performed easily and quickly and inexpensively.

in this connection In a further embodiment, the increased resolution of the overall picture can be in the scan direction by the reciprocal of the fractional factor over the Scan at usual Scanning speed differ, with the increased resolution of the overall picture across to the scan direction is the reciprocal of the fractional factor concerning the Offset in the direction of the sensor line compared to scanning without offset different. This means, for example, at a fractional factor ½, that is one Reduce scan speed to half while setting an offset of half a distance between the adjacent ones Photosensitive elements of the sensor line that the resolution of the Overall image doubled in both imaging directions and the amount of data thus quadrupled.

From Another advantage is that the overall picture thus determined of the object by means of a sharpening filter can be improved. Due to the overlap of pixel information the correspondingly sorted image information of the photosensitive Elements of the sensor line from the various passes can a sharpening algorithm especially well rework the object image and thus the quality of the overall picture continue to increase.

Conceivable it is also that the first pass and / or the at least one further pass bidirectional, so no default the scanning device is required and therefore the scanning process especially be done quickly can. Therefor is only the sorting algorithm adapt, with which the sorting image information associated with each other to the overall picture.

Conceivable it is also that in addition to the movement of object and / or line sensor also the lens for imaging the object is moved to the line sensor. Then, however, the thereby changing magnification in the Calculation of the relative path between line sensor and object and taking into account the resulting scan speed become.

The The invention further relates to a device for increasing the resolution scanned image information, comprising an imaging optics and a Line sensor with which an object moved relative to the line sensor is detected by the line sensor successively and at a constant scan speed line by line images of the object. Such a device is thereby further formed that the device is a device for regulating the Scanning speed of the line sensor due to the relative movement between line sensor and object across the sensor line and a device for adjusting the line sensor relative to the object in the direction having the sensor line of the line sensor. By the additional and adjustable to the scan movement adjustment between line sensor and object in the direction of the sensor line, the inventive method especially easy and reliable accomplished become. Such an adjustment in the direction of the sensor line is easy to arrange on scanners and can possibly even existing Retrofitted scanning devices become. As this is usually just about adjustments in the Millimeter range, this can be done, for example, by appropriate Actuators such as stepper drives, piezo drives or the like realized become.

in this connection it is conceivable that the drive of the relative movement between the line sensor and object in the scanning direction continuously or stepwise. With that you can different drive concepts such as stepper motors and continuously working drives are used.

From It is advantageous if the adjustment of the line sensor relative to the object in the direction of the scanning line of the line sensor in at least one of the end positions of the scanning movement takes place. This must be during the actual scanning process no positioning or adjustment the line sensor and the adjustment can be clamped become.

Farther It is conceivable that the device has an electronic shutter by which the exposure time of the line sensor becomes smaller as the readout time of the line sensor. Since the readout time or the exposure time of the line sensor has an influence on the photosensitivity of the scanner, this can improve the scanning process.

In a first advantageous embodiment, the line sensor only monochrome photosensitive elements, so that the detected Object image is scanned in one color. It is also conceivable that the line sensor is a trilinear array of color-sensing Single lines has, preferably with each other staggered lines each red / green / blue sensitivity. This can also be done Objects are also scanned in color. If the offset of the red / green / blue-sensitive Elements known can also be an exact mapping of each Colors to the pixels of the object image done.

A particularly preferred embodiment of the device according to the invention for carrying out the method according to the invention shows the Drawing.

It demonstrate:

1 A schematically illustrated arrangement of the components of a device according to the invention when scanning at the usual scanning speed,

2 - A schematically illustrated arrangement of the device according to the invention 1 when scanning at half the scan speed T ₁ 'and offset Δx in the direction of the sensor line of the line sensor,

3 - Schematic and greatly enlarged arrangement of different scanned image information of the overall picture in the application of the method according to the invention.

In the 1 is a very schematic representation of an arrangement of the device according to the invention shown, from which also shows the flow of the inventive method. For scanning the object 3 Here, for example, a plane template such as a book or a photo, in a basically known manner by means of an imaging optics 2 via an imaging beam 9 an object image on a scanning device 5 projected. The imaging beam falls here on a line sensor 1 that is from a sensor line 8th consists of a juxtaposition of photosensitive elements such as CCD elements. The photosensitive elements are in the direction of the sensor line 8th arranged linearly and due to the resolution of the line sensor 1 each spaced apart.

Now either the object 3 against the scan direction 7 or the scanning device 5 in the scanning direction 7 or both are moved at a scanning speed V, image information is successively obtained 4 of the object on the line sensor 1 pro jected and read there one after the other in basically known manner. Thus arises during the relative movement of object 3 and scanning device 5 a line-by-line image of linear image information 4 , which can be combined into a two-dimensional overall picture.

Should the resolution of the overall picture in the scanning direction 7 can be increased, so the scan speed V can be reduced. This can be something like in the 2 represented by the scanning speed V 'is reduced to half the value of the usual scan speed V. The line-shaped image information 4 of the object lie in this case as in 2 clearly visible closer together, their distance has been halved. But this is in the scanning direction 7 twice as much image information 4 about the object 3 before when scanning at the usual scanning speed V.

Transverse to the scanning direction 7 the image information changes over the object 3 but not because of the photosensitive elements of the sensor line 8th keep their distance from each other regardless of the scan speed. Related to the 3 only stripes of image information result 10 at a distance x to each other, wherein the distance x due to the physical resolution of the line sensor 1 results and the distance of the photosensitive elements of the sensor line 8th equivalent. Between these strips of image information 10 there is no information about the object 3 in front.

Will now, however, after a like in 1 recognizable first pass when scanning the object 3 one or more further passes of the scan are carried out, and the line sensor in each case by a value Δx to its previous position in the longitudinal direction 6 the sensor line 8th moved, so can more stripes of image information 11 . 12 . 13 be obtained, the picture information 4 ' . 4 '' . 4 ''' include that between the strips of picture information 10 lie and an increase in image resolution also in the direction 6 the sensor line 8th Offer. Of course it is also possible to use the object 3 in segments, each segment being recorded at the higher resolution. This is particularly advantageous for large objects and / or special requirements for the resolution of the overall picture.

In the 2 The simplest case shown is that of the line sensor 1 in the direction 6 the sensor line 8th by half the distance between adjacent photosensitive elements of the sensor line 8th is moved to the first pass. This would be another strip 12 the picture information 4 '' let win, the middle between the stripes 10 the picture information 4 lies and thus, as this over the entire length of the sensor line 8th takes place, also a doubling of the resolution in direction 6 the sensor line 8th result. It is of course also conceivable, more stripes 11 . 13 the picture information 4 ' and 4 ''' in that the offset Δx of the line sensor 1 is chosen smaller. The fractional factor of the offset Δx with respect to the distance between adjacent photosensitive elements of the sensor line 8th should be between 0 and 1, as otherwise identical image information would be obtained and thus only redundant image information 4 Present, which would give no real increase in the resolution.

One can calculate the fractional factor of the offset Δx in the direction 6 the sensor line 8th particularly well set to such a fraction factor, the is also present by the ratio of commonly used scanning speed V to reduced scanning speed V '. With the same fractional factors, the resolution of the overall image changes uniformly in both directions, resulting in approximately square pixel information of the overall image.

Of course it is it also possible to select the fraction factor such that a partial overlap the scanned pixel of the overall picture.

1

line sensor

2

imaging optics

3

object

4

line by line image information

4 '

line by line image information

4 ''

line by line image information

4 '' '

line by line image information

5

scanning device

6

adjustment

7

scanning direction

8th

sensor line

9

imaging beam

10

strip the picture information

11

strip the picture information

12

strip the picture information

13

strip the picture information

Claims (20)

Method for increasing the resolution of scanned image information using a line sensor ( 1 ), where an object to be scanned ( 3 ) with a relative to the object moving line sensor ( 1 ) is detected by the line sensor ( 1 ) one after the other and at a constant scanning speed (V) line by line images ( 4 ) of the object ( 3 ), characterized in that the line sensor ( 1 ) in a first pass the images ( 4 ) of the object ( 3 ) in the scanning direction ( 7 ) across the sensor line ( 8th ) of the line sensor ( 1 ) is detected at a scanning speed (V ') which is reduced to a fraction of the usual scanning speed (V) and at least one further pass follows the first pass, in which case the line sensor ( 1 ) longitudinal ( 6 ) of the sensor line ( 8th ) offset to the position of the line sensor ( 1 ) on the first pass relative to the object ( 3 ) in the scanning direction ( 7 ) is moved. Method according to claim 1, characterized in that the further passage or the other runs also be performed at this reduced scan speed (V '). Method according to one the claims 1 or 2, characterized in that the fraction of the usual Scanning speed (V) is an integer fraction of the usual Scan speed (V) is. Method according to one the preceding claims, characterized in that the further pass or the other runs with the integer fraction of the usual scan speed (V) performed become. Method according to claim 4, characterized in that as an integer fraction with respect to Scan speed (V) half the usual scan speed (V) is used. Method according to one of the preceding claims, characterized in that the offset (Δx) of the line sensor ( 1 ) in the direction ( 6 ) of the sensor line ( 8th ) an integer fraction of the distance between adjacent photosensitive elements of the sensor line ( 8th ) is. Method according to Claim 6, characterized in that the offset (Δx) of the line sensor ( 1 ) relative to the distance between adjacent photosensitive elements of the sensor line ( 8th ) in the direction ( 6 ) of the sensor line ( 8th ) in the ratio of the same integer fraction as the fraction of the reduced scanning speed (V ') relative to the usual scanning speed (V). A method according to claim 7, characterized in that as an integer fraction with respect to the offset (Δx) half the distance between adjacent photosensitive elements of the sensor line ( 8th ) of the line sensor ( 1 ) is used. Method according to one of the preceding claims, characterized in that the results of the first pass and the results of the further pass or further passes are offset from one another to form an overall picture of the object ( 3 ) with increased resolution compared to the physical resolution of the line sensor ( 1 ). Method according to one of the preceding claims, characterized in that the increased resolution of the overall image in the scanning direction ( 7 ) differs by the reciprocal of the fractional factor over the scan at the usual scan speed (V). Method according to one of the preceding claims, characterized in that the increased resolution of the overall image transversely to the scanning direction ( 7 ) is the reciprocal of the fractional factor with respect to the offset (Δx) in the direction ( 6 ) of the sensor line ( 8th ) differs from scanning with no offset (Δx). Method according to one of the preceding claims, characterized in that the overall image of the object ( 3 ) is improved by means of a sharpening filter. Method according to one the preceding claims, characterized in that the first pass and / or the at least another pass is bidirectional. Method according to one of the preceding claims, characterized in that the objective ( 2 ) for imaging the object ( 3 ) on the line sensor ( 1 ) is moved. Device for increasing the resolution of scanned image information ( 4 ), comprising an imaging optics ( 2 ) and a line sensor ( 1 ), with which a relative to the line sensor ( 1 ) moving object ( 3 ) is detected by the line sensor ( 1 ) one after the other and at a constant scanning speed (V) line by line images ( 4 ) of the object ( 3 ), in particular for carrying out the method according to claim 1, characterized in that the device comprises a device for controlling the scanning speed (V) of the line sensor ( 1 ) due to the relative movement between the line sensor ( 1 ) and object ( 3 ) across the sensor line ( 8th ) and a device for adjusting the line sensor ( 1 ) relative to the object ( 3 ) in the direction of the sensor line ( 8th ) of the line sensor ( 1 ) having. Apparatus according to claim 15, characterized in that the drive of the relative movement between the line sensor ( 1 ) and object ( 3 ) in the scanning direction ( 7 ) takes place continuously or stepwise. Device according to one of claims 15 or 16, characterized in that the adjustment of the line sensor ( 1 ) relative to the object ( 3 ) in the direction of the sensor line ( 8th ) of the line sensor ( 1 ) takes place in at least one of the end positions of the scanning movement. Device according to one of claims 15 to 17, characterized in that the device comprises an electronic shutter, by which the exposure time of the line sensor ( 1 ) smaller than the readout time of the line sensor ( 1 ). Device according to one of claims 15 to 18, characterized in that the line sensor ( 1 ) has monochrome photosensitive elements. Device according to one of claims 15 to 18, characterized in that the line sensor ( 1 ) has a trilinear arrangement of color-sensing single lines, preferably mutually offset single lines each with red / green / blue sensitivity.