JPH04368063A - Image scanner - Google Patents

Abstract

PURPOSE:To read an original picture without lowering the efficiency of data processing and to apply shading correction as to a read picture by keeping the resolution of the original picture whose position is deviated in the main scanning direction of a line sensor. CONSTITUTION:The image scanner reads a frame picture I of a micro film 23 with a CCD line sensor 25 having plural line photoelectric conversion elements. The CCD line sensor 25 uses a carrier plate 28 and a motor 29 or the like to be moved in the main scanning direction X with respect to the frame picture I. When the frame picture I is deviated with respect to the micro film 23 in the direction X, the CCD line sensor 25 is moved to read the frame picture I. In this case, in order to implement the shading correction, the CCD line sensor 25 is moved in the direction to obtain the shading correction data at plural position in the main scanning direction in advance and the data is stored in an AE-RAM 54. When the frame picture I is read, the shading correction data is read from the AE-RAM 54 corresponding to the position in the main scanning direction and used for the correction.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image scanner, and more particularly to an image scanner that reads an image of a document using a line sensor.

0002

[Prior Art] As a conventional image scanner, FIG.
As shown in FIG. 1, there has been known a device that uses a one-dimensional CCD line sensor 11 to read original images (hereinafter referred to as including microfilm images). In this system, frame images on a microfilm 12 are projected via a projection optical system 13 onto a plurality of photoelectric conversion elements arranged in an imaging section of a CCD line sensor 11, and the imaging section performs photoelectric conversion and generates an image signal. It was outputting. These multiple (e.g. 5000
The photoelectric conversion element (for each pixel) outputs a value corresponding to the light intensity from the projected original image. The projection optical system 13 includes a light source 14, a condenser lens 15, a mirror 16, a condenser lens 17, and a projection lens 18.

In this image scanner, by moving the film carrier holding the microfilm 12, the CCD line sensor 1, which is fixed in position, can be moved.
1, the frame images were moved in the sub-scanning direction and the frame images were sequentially read.

However, in this image scanner, the position of the original image to be read is not always placed at a constant position. For example, when a frame image of a microfilm is read using the apparatus shown in FIG. 9, the position of this frame image may deviate from side to side with respect to the winding direction of the microfilm. If the position of the image to be read changes in the direction of the array of photoelectric conversion elements of the CCD line sensor 11 in this way, and you want to read the necessary image without causing image loss, take the following measures. There was a need.

For example, it is possible to increase the number of photoelectric conversion elements in the line sensor 11 so as to cover the entire reading area of the original image, or to use a variable magnification lens as the projection lens 18 in the projection optical system 13 to read the original image. It is conceivable to reduce the image and project it onto the line sensor 11.

[0006]

However, in the former case, it is not possible to cope with changes in the document size. For example, when the document size is small, the line sensor 11 is forced to detect unused data. There are many pixels, and signal processing for unused pixels is troublesome. On the other hand, in the latter case, the resolution of the original image has decreased.

[0007] Therefore, the present applicant has developed an image scanner that reads an original image by moving a line sensor composed of a certain number of photoelectric conversion elements also in the main scanning direction (or by moving the original image with respect to the line sensor). It was devised. However, even with such an image scanner, shading correction must be performed in order to faithfully reproduce frame images of a document. Even with such an image scanner, there are problems such as uneven illuminance of the projection optical system (optical unevenness caused by the light source, etc.), unevenness of output between each photoelectric conversion element of the line sensor (unevenness of output caused by the line sensor manufacturing process, etc.)
This is because such things are occurring. Furthermore, in this case, when the line sensor is moved in the main scanning direction, the required shading correction amount changes each time.

[0008]

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to solve the problem of reducing the resolution of an original image whose image position varies in the main scanning direction without increasing the number of photoelectric conversion elements of a line sensor. The object of the present invention is to provide an image scanner that can efficiently read images and perform appropriate shading correction.

[0009]

[Means for Solving the Problem] As shown in FIG. 1, an image scanner according to the invention as set forth in claim 1 has a line sensor 10 formed by arranging a plurality of photoelectric conversion elements in a line.
0, an image scanner that scans and reads a document image, and a projection optical system 200 that projects the document image onto the line sensor 100;
A holding means 300 that holds the projection optical system 200 and the line sensor 100 relatively movably in the main scanning direction.
and the line sensor 1 for the projection optical system 200.
A sampling means 400 that samples and stores shading correction data at a plurality of positions when 00 moves in the main scanning direction; The sampling means 40 according to the relative position
correction means 5 for performing shading correction based on shading correction data sampled by 0;
This is an image scanner equipped with 00.

0010

According to the image scanner according to the first aspect of the invention, the projection optical system 200 projects an original image onto the line sensor 100, and the line sensor 100 reads the original image. In this case, the image scanner scans the original image in the main scanning direction and the sub-scanning direction to read the original image. Then, by performing shading correction on this read original image,
Reproduce the original image faithfully. That is, in this image scanner, the projection optical system 2 is held by the holding means 300.
00 and the line sensor 100 are moved relatively in the main scanning direction, and the sampling means 400 samples and stores shading correction data caused by uneven illuminance at the plurality of positions and uneven output between each photoelectric conversion element. . When reading a document image, the correction means 500 corrects the read document image based on the shading correction data corresponding to the relative position in the main scanning direction between the projection optical system 200 and the line sensor 100. Shading correction is performed on the image signal. As a result, the line sensor can be relatively moved in the main scanning direction to read the document image, and appropriate shading correction can be performed on the image signal.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. 2 to 8 are for explaining an embodiment in which the image scanner according to the present invention is applied to a microfilm scanner.

FIG. 2 is a perspective view of a projection optical system of a microfilm scanner according to an embodiment, and FIG. 3 is a block diagram showing a CPU and its peripheral circuits of the microfilm scanner.

As shown in FIG. 2, the microfilm scanner projects frame images of a microfilm 23 stretched between a supply reel 21 and a take-up reel 22 onto a CCD line sensor 25 using a projection optical system 24. , this frame image is read by this CCD line sensor 25.

Specifically, the supply reel 21 and the take-up reel 22 are mounted on a roll film carrier (not shown) at a predetermined distance from each other. This supply reel 21 contains a plurality of frame images (also called micro images).
A microfilm 23 on which images are sequentially imprinted along its longitudinal direction is wound, and the microfilm 23 is wound onto a take-up reel 22 from this supply reel 21. These supply reel 21 and take-up reel 22 are driven by motors 61 and 62, respectively. And between these reels 21 and 22, the microfilm 23
By winding and rewinding, a frame image to be read is retrieved, and a desired frame image is placed at a reading position between a pair of upper glass 26 and lower glass 27 provided between both reels 21 and 22. It is something that makes it stop. This roll film carrier has a similar configuration to a film carrier generally used in microreader printers, etc., and is a well-known technology, so a detailed explanation of the frame image retrieval method and the like will be omitted.

The CCD line sensor 25 is installed directly above the pair of upper glass 26 and lower glass 27.
is provided hanging down and fixed to the lower surface of the rectangular carrier plate 28. This CCD line sensor 25 is configured by arranging a plurality of photoelectric conversion elements (for example, 5000 pixels) in a line. The arrangement direction (main scanning direction) of the photoelectric conversion elements is set perpendicular to the running direction (sub scanning direction) of the microfilm 23. Further, one end of this carrier plate 28 is connected to a CCD
Longitudinal direction of line sensor 25 (photoelectric conversion element arrangement direction)
The wire 30 is slidably supported by a slide rail 37 extending parallel to the wire 30, and the other end is connected to both ends of a wire 30 stretched between pulleys 38 and 39. This pulley 38 is connected to the drive shaft of a motor 29, and by driving this motor 29, the CCD line sensor 25 is moved together with the carrier plate 28 in a direction parallel to the main scanning direction (in the direction indicated by arrow X in the figure). ), move to the projected image and C
This is a configuration in which the relative position with respect to the CD line sensor 25 is adjusted. Note that the relative position between the projected image and the line sensor 25 can be adjusted by fixing the line sensor 25 and adjusting the projection lens 3.
5 or by moving the film carrier in the main scanning direction.

The projection optical system 24 that projects frame images onto the CCD line sensor 25 includes a lamp 31 as a light source, a condenser lens 32 that condenses the light from the lamp 31, and a condenser lens 32 that condenses the light from the lamp 31. a mirror 33 disposed directly below the upper glass 26 and lower glass 27 to guide light to the pair of upper glass 26 and lower glass 27; and a condenser lens 34 disposed above the mirror 33. , a zoom lens 35 serving as a projection lens is disposed directly above the upper glass 26 and the lower glass 27 and directly below the CCD line sensor 25.

Therefore, the light transmitted through the frame image positioned between the upper glass 26 and the lower glass 27 is
It reaches the projection lens 35, and by this projection lens 35
It will be projected onto the CD line sensor 25. The projection lens 35 is a zoom lens, and its projection magnification is changed by driving the motor 36.

FIG. 3 shows the system configuration of this microfilm scanner. As shown in this figure, C
Based on the clock signal from the clock generation circuit 41 (based on the shift pulse), the CD line sensor 25
The configuration is such that an analog signal generated by each photoelectric conversion element is output to an A/D conversion circuit 42. The digital signal output (image signal of 8-bit data) of this A/D conversion circuit 42 is input to the shading correction circuit 44, which collects shading correction data (data on optical unevenness and pixel unevenness), which will be described later. In this case, the output of the A/D conversion circuit 42 is input to the shading RAM 43 and stored once, and then sent to the AE-RAM 5 via the system bus.
This is the configuration that is transferred to 4. When reading a frame image, the shading correction data stored in the AE-RAM 54 is stored in the shading RAM 43, and the 8-bit data output (shading correction signal) of the shading RAM 43 is also input to the shading correction circuit 44. It is. Further, the 8-bit data output signal (image output after shading correction) of this shading correction circuit 44 is inputted to an image processing circuit 45 and subjected to predetermined image processing.
The 8-bit data of No. 5 is output as 1-bit data via an external I/F (interface) circuit 46.

[0019] Also, these shading RAM 43
, the shading correction circuit 44, the image processing circuit 45, and the external I/F circuit 46 are connected to the C through the system bus.
It is connected to PU51 etc. The CPU 51 connects to the system ROM 52 and system RAM 5 via this system bus.
3. Connected to the AE-RAM 54 above. moreover,
This CPU 51 connects this system bus to each of the CCD main scanning direction drive circuit 55, image scan drive circuit 56, lamp light amount control circuit 57, zoom lens drive circuit 58, supply reel drive circuit 63, and take-up reel drive circuit 64. are connected to each other through. That is, the CPU 51 performs preliminary scanning, main scanning, shading correction processing, and
It controls image processing, etc.

Note that the CCD main scanning direction drive circuit 55 outputs a drive signal to the motor 29 to drive the carrier plate 2.
8 in the main scanning direction. The image scan drive circuit 56 uses a motor 59 to move the roll film carrier in the sub-scanning direction. The lamp light amount control circuit 57 controls the amount of light output from the lamp 31. Further, the zoom lens drive circuit 58 outputs a drive signal to the motor 36 to drive the zoom lens 35 and change the projection magnification of the frame image. Further, the supply reel drive circuit 63 and the take-up reel drive circuit 64 output drive signals to the motors 61 and 62, respectively, to wind and unwind the microfilm 23.

In the microfilm scanner according to this embodiment, the following procedure is used to read frame images from the microfilm 23.

First, when the power of the apparatus is turned on, the microfilm 23 is not wound on the take-up reel 22, that is, the microfilm 23 is not present between the upper glass 26 and the lower glass 27. , collects optical unevenness data and pixel unevenness data for creating shading correction data. The optical unevenness data is mainly data on light intensity unevenness due to the characteristics of the projection optical system 24 and the zoom lens 35, and the pixel unevenness data is data on output unevenness between each photoelectric conversion element of the CCD line sensor 25. The method for collecting these data will be detailed later.

When the collection of optical unevenness data and pixel unevenness data is completed, a frame image search is performed by a well-known method, and the frame image to be read is set at the reading position between the upper glass 26 and the lower glass 27. Ru. after that,
The motor 29 is driven to set the CCD line sensor 25 at a predetermined position, and the roll film carrier is further moved in the sub-scanning direction to perform a preliminary scan. In this preliminary scan, the CCD line sensor 25 detects the position of the frame image in the main scanning direction.

Then, the CCD line sensor 25 is activated in accordance with the position of the frame image detected by this preliminary scan.
The optimum position in the main scanning direction is determined, and the motor 2
9 is driven. The optimal value for the position of the CCD line sensor 25 in this case is a position where the range in the main scanning direction of the image projected onto the CCD line sensor 25 matches the reading range of the CCD line sensor 25. Note that, hereinafter, an area in which an image can be read by moving the CCD line sensor 25 in the main scanning direction will be referred to as a readable area. That is, as long as the frame image is within this readable area, the frame image can be read at an appropriate position by moving the CCD line sensor 25.

After that, the roll film carrier is moved in the sub-scanning direction again and main scanning for image reading is performed, but at this time, the current C
Shading correction data corresponding to the position of the CD line sensor 25 is determined, and the image data read by the CCD line sensor 25 is subjected to shading correction based on this shading correction data.

FIGS. 4 and 5 show the CCD line sensor 25 during preliminary scanning and main scanning, respectively.
FIG. 2 is a schematic diagram showing a relative positional relationship in the main scanning direction with an image projected thereon and a projection magnification.

In the preliminary scan, the zoom lens 35 is set to a magnification for the preliminary scan that is smaller than the predetermined reading magnification during the main scan. By projecting a predetermined light from the lamp 31, as shown in FIG.
It is projected onto the photoelectric conversion element of the CD line sensor 25. This allows the position of the frame image I in the readable area of the microfilm 23 to be read. It should be noted that on the microfilm 23, a blip mark BM for retrieval is imprinted outside the frame of each frame image I.

In the main scan, the zoom lens 35 is driven by the motor 36 to set a predetermined reading magnification for the main scan, and the CCD line sensor 25 is moved in the main scanning direction. As shown in , by setting the projected image as a whole to be located within the width W (width of 5000 pixels) of the effective photoelectric conversion element of the CCD line sensor 25, the projected image for the CCD line sensor 25 is set. Optimize relative position. Note that the reading magnification for the main scan is the same as the projection magnification at the time of collecting the shading correction data (optical unevenness data and pixel unevenness data).

Next, with reference to the flowchart shown in FIG. 7, data for shading correction (optical unevenness data and pixel unevenness data) in the microfilm scanner is calculated.
This section explains sampling.

When the microfilm scanner is powered on, first, it is checked whether the microfilm 23 has been removed from the reading position (step S701).
. This is because the shading correction data is created in a state where the microfilm 23 is not present in the optical path from the lamp 31 to the CCD line sensor 25. If the supply reel 21 is not attached or if the microfilm 23 is removed from the reading position because the entire microfilm 23 is wound onto the supply reel 21, the process directly advances to step S703. When the microfilm 23 is present at the reading position, the supply reel driving motor 61 is driven to completely wind the microfilm 23 onto the supply reel 21 (S
702).

Next, with this film removed, the lamp 31 is turned on by the lamp light amount control circuit 57 (S
703). As a result, the lamp 3
One light beam is irradiated onto a plurality of photoelectric conversion elements of the CCD line sensor 25. At the same time, the zoom lens 35 is set so that the projection magnification of the image onto the CCD line sensor 25 has the same predetermined value as the magnification during the main scan described above.

[0032] Then, this CCD line sensor 25 is
The photoelectric conversion element at the tip (the first photoelectric conversion element located at the end in the arrangement direction) is moved so that it is located at the tip (A in FIG. 6) of the readable area (S704).

Then, data for one line of the CCD line sensor 25, that is, current generated in a plurality of photoelectric conversion elements by the projection light of the lamp 31, is extracted for 5000 pixels, and converted into a digital signal by the A/D conversion circuit 42. and stores it in the shading RAM 43 (S70
5). Furthermore, in this way the shading RAM 4
All of the data for one line (data for 5000 pixels) stored in AE-RAM 54 is transferred, saved, and stored in the AE-RAM 54 (S706). This shading correction data is obtained as data including data due to the above-mentioned optical unevenness and data due to pixel unevenness.

Next, it is determined whether the photoelectric conversion element at the rear end of the CCD line sensor 25 is located at the rear end of the readable area (B in FIG. 6) (S707). If the rear end photoelectric conversion element is not located at the rear end of the readable area, C
The CD line sensor 25 is moved by one step in the main scanning direction toward the rear end of the readable area (S708). This movement step can be, for example, a value that moves by one photoelectric conversion element, or may be configured by a value that moves by a plurality of photoelectric conversion elements. For example, by driving the motor 29 for a predetermined number of pulses, the film carrier 28
is moved a predetermined distance in the X direction. and,
Returning to step S705, data is read at this position, and data for one line (data for 5000 pixels) is read again.
is stored in the shading RAM 43, and further, the data is transferred to and stored in the AE-RAM 54 (S706
). These steps S705, S706, S707, S7
By repeating step 08, the CCD
The line sensor 25 is moved in the main scanning direction, and the shading correction data is stored in the AE-RAM 54 at each movement step.
Store in. That is, shading correction data is sampled at a plurality of different positions in the main scanning direction of the CCD line sensor 25.

Then, when the photoelectric conversion element at the rear end of the CCD line sensor 25 reaches the rear end of the readable area (S7
07), the collection of shading correction data for the entire readable area by the CCD line sensor 25 is completed, and the process advances to step S709. As a result, output data (shading correction data) for the entire readable area is obtained, for example, as shown in the graph of FIG. 6.

In step S709, the lamp 31 is turned off.
As F, the CCD line sensor 25 is moved to a predetermined home position (S710), and this routine ends. This home position is a position determined in advance so that the entire readable area is accurately projected onto the CCD line sensor 25 during preliminary scanning.

Next, shading correction of image data in the main scan will be explained with reference to the flowchart of FIG.

First, an image area to be read by the CCD line sensor 25 is determined in accordance with the position of the frame image detected by preliminary scanning (S801). In addition,
In this embodiment, the image area to be read by the CCD line sensor 25 is automatically determined by performing a preliminary scan, but the operator may manually input the image area to be read. . Then, by driving the motor 29, the CCD
The line sensor 25 is moved in accordance with this frame image position (S802). At this time, the zoom lens 35 is set so that the projection magnification becomes a predetermined value for main scanning.

Then, the shading correction data stored in the AE-RAM 54, that is, the shading correction data corresponding to the stop position of the CCD line sensor 25, is read out from the AE-RAM 54 and transferred to the shading RAM 43 (S803). Once the shading correction data at the position of the CCD line sensor 25 is obtained in this way, the main scan is performed.

That is, the lamp 31 is turned on (S80
4) Start the main scan (S805). The image data read by the CCD line sensor 25 during this main scan is transferred to the shading correction circuit 44, and the shading correction circuit 44 performs shading correction on the image data based on the shading correction data (S806). ).

When this main scan is completed, the lamp 31
is turned off (S807), and the scan system is reset (S808). For example, the scanning mechanism and CCD line sensor 25 are moved to the home position. As described above, even if the position of each frame image I is shifted in the main scanning direction, this position is detected and the read image data is processed using shading correction data corresponding to that position. Optimal shading correction can be performed for Note that the step width can be set based on the memory capacity of the AE-RAM 54. By increasing the movement step width, memory capacity can be saved.

[0042]

As described above, according to the present invention, since the line sensor and other optical systems are supported so as to be movable relative to each other in the main scanning direction of the line sensor, the image to be read can be moved in the main scanning direction. It is possible to always read images in the appropriate range even when the position of the image is not constant, and
Shading correction adapted to the reading range at that time can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the functional configuration of an image scanner according to the present invention.

FIG. 2 is a perspective view schematically showing a projection optical system of a microfilm scanner according to an embodiment of the present invention.

FIG. 3 is a block diagram showing the overall configuration of a microfilm scanner according to an embodiment of the present invention.

FIG. 4 is a schematic diagram showing the relative positional relationship and projection magnification in the main scanning direction between a CCD line sensor and an image projected thereon during preliminary scanning by a microfilm scanner according to an embodiment of the present invention; be.

FIG. 5 is a schematic diagram showing the relative positional relationship and projection magnification in the main scanning direction between a CCD line sensor and an image projected thereon during main scanning by a microfilm scanner according to an embodiment of the present invention; be.

FIG. 6 is a schematic diagram for explaining creation of shading correction data in a microfilm scanner according to an embodiment of the present invention.

FIG. 7 is a flowchart showing a CPU program for obtaining shading correction data in a microfilm scanner according to an embodiment of the present invention.

FIG. 8 is a flowchart showing a CPU program when performing shading correction in a main scan in a microfilm scanner according to an embodiment of the present invention.

FIG. 9 is a perspective view schematically showing a projection optical system of a conventional microfilm scanner.

[Explanation of symbols]

100 Line sensor 200 Projection optical system 300 Holding means 400 Sampling means 500 Correction means

Claims (1)

[Claims] 1. An image scanner that scans and reads an original image using a line sensor formed by arranging a plurality of photoelectric conversion elements in a line, the image scanner comprising:
a projection optical system for projecting the document image onto the line sensor; a holding means for holding the projection optical system and the line sensor so as to be relatively movable in the main scanning direction; a sampling means for sampling and storing shading correction data at multiple positions when the line sensor moves in the main scanning direction; and a relative position in the main scanning direction between the projection optical system and the line sensor when reading an original image; an image scanner, comprising: a correction means for performing shading correction based on the shading correction data sampled by the sampling means according to the above.