JP2004126284A - Image read unit and image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To read even light-transmitting documents in the optimum in-focus state in the same way as light-reflecting documents by using a CIS scanner using a rod lens array. <P>SOLUTION: An image reader is provided with first and second image read element arrays and first and second focal lenses corresponding to them respectively, and the focus positions of first and second focal lenses are made different. The second image read element array has a higher resolution, and the focal length of the second lens is made longer than that of the first lens. The second image read element array has a shorter read length. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides an image reading unit having an image reading element array in which a plurality of photoelectric conversion elements are linearly arranged, and a reflection original such as a printed matter and a transparent original such as a photographic film using the reading unit. The present invention relates to an image reading device having a reading function.
[0002]
[Prior art]
Conventionally, when a transparent original such as a photographic film is read by a flatbed type image reading device having an original platen glass, the transparent original is installed on the transparent original guide unit and set on the original platen glass, and the transparent original The method of irradiating with a surface light source unit from the top is the mainstream. In general, an image reading apparatus of this type is designed so that the position where the focus is most focused is the position of the upper surface of the platen glass 0 mm, that is, the position in contact with the platen glass. The reason is that it is assumed that the main document to be read is a reflection document. In the case of a transparent original, it is common that the original is set so as to be raised about 0.5 mm from the glass surface of the original table by a transparent original guide. The reason for floating is to prevent Newton rings or to pick up dirt when touching the glass surface.
[0003]
In the case of a lens of a reduction optical system using a CCD, this method has no practical problem even if the depth of field is deep and the distance between the platen glass and the transparent original is about 0.5 mm.
[0004]
[Problems to be solved by the invention]
However, in recent years, a reading unit of the same magnification optical system using a rod lens array has appeared for the purpose of miniaturization. Since the depth of field of the rod lens array is shallow, if the distance between the platen glass and the transparent original is about 0.5 mm, there is a problem that the focus is blurred.
[0005]
The present invention has been made in view of the above circumstances, and has as its object to provide an image reading apparatus capable of effectively and appropriately reading images of both a reflective original and a transparent original.
[0006]
[Means for Solving the Problems]
The image reading unit according to claim 1 of the present invention comprises a first image reading element array in which a plurality of photoelectric conversion elements are arranged in a line, and a plurality of photoelectric conversion elements in parallel with the first image reading element array. A second image reading element array in which elements are arranged in a line, a first lens that forms a first document image at a first focal position on the first row of image reading element arrays, A second lens that forms a second document image having a different conjugate length from the first lens and at a second focal position different from the first focal position on the image reading element array in the second row; And characterized in that:
[0007]
The image reading unit according to claim 3, wherein a first image reading element array in which a plurality of photoelectric conversion elements are arranged in a line, and a plurality of photoelectric conversion elements in parallel with the first image reading element array. Are arranged in a line, the second image reading element array having a higher resolution than the first image reading element array, and the first original image at the first focal position is read in the first column of image reading elements. A first lens that forms an image on the array, and a second lens that forms a second document image at a second focus position different from the first focus position on the image reading element array in the second row. And a lens.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of an image reading apparatus according to the present invention will be described with reference to the drawings.
[0009]
(1st Embodiment)
FIG. 1 is a view showing an image reading apparatus according to a first embodiment of the present invention. In FIG. 1, 1 is a reading unit, 2 is a stepping motor, 3 is a belt, 4 is a platen glass, and 5 is a control board. , 6 is a 35 mm photographic film, 7 is a white reference plate / document regulating plate, 8 is a flat cable, 9 is an external computer, 101 is a holder for mounting the reading unit 1, and 102 is a film guide (film holder) for storing the 35 mm photographic film 6. ), 103 is a light source unit for film, 104 is a cable for connecting 103 to the control board 5, and 105 is a document regulating plate.
[0010]
FIG. 2 is a block diagram illustrating a configuration of a processing circuit built in the control board 5. Hereinafter, the circuit operation of the present case will be described with reference to FIG.
[0011]
2, a reading unit 1 is a reading unit for reading an image on a photographic film 6 stored in a film guide 101 or a reflection original placed on the platen glass 4 shown in FIG. An LED 1201C, which is a light source for illuminating a document, is also integrated with the reading unit 1. While moving the reading unit 1 along the document surface of the document table 4, the LED control circuit 1201B switches the LEDs of each color for each line to light up, thereby reading the R, G, and B line sequential color images. It is possible.
[0012]
The LED 1201B itself emits white light, and an R, G, B (or C, M, Y, K) optical color filter is provided on the optical path of the LED from the LED 1201B to the document. May be provided, and a sequential color image of each color may be read in the same manner as described above.
[0013]
Reference numeral 1202 denotes an amplifier that amplifies the signal output from the CIS 1201, and reference numeral 1203 denotes an A / D converter that performs A / D conversion of the amplified output to obtain, for example, an 8-bit digital output. The shading RAM 1205 stores data for shading correction by reading a white shading plate in advance, and the shading correction circuit 1204 performs shading correction of the read image signal based on the data of the shading RAM 1205.
[0014]
The gamma conversion circuit 1206 is from the host computer. The gamma conversion of the image data read according to a preset gamma curve is performed. A buffer RAM 1208 is a RAM for temporarily storing image data in order to match an actual reading operation with a timing in communication with the host computer. A packing / buffer RAM control circuit 1207 is provided by the host computer in advance. After performing a packing process in accordance with the set image output mode (binary, 4-bit multi-value, 8-bit multi-value, 24-bit multi-value), a process of writing the data into the buffer RAM 1208 is performed. The image data is read from the RAM 1208 and output.
[0015]
The interface circuit 1209 receives a control signal and outputs an image signal with an external device 9 serving as a host device of the image reading apparatus according to the present embodiment, such as a personal computer. Reference numeral 1213 denotes, for example, a microcomputer-type CPU having a ROM 1213A storing a processing procedure and a working RAM 1213B, and controlling each unit according to the procedure stored in the ROM 1213A. Reference numeral 1212 denotes, for example, a crystal oscillator. Reference numeral 1211 denotes a timing signal generation circuit which divides the output of the oscillator 1212 in accordance with the setting of the CPU 1213 and generates various timing signals serving as operation references.
[0016]
FIG. 3 is a configuration diagram of the reading unit 1, wherein 10 is a red LED, 11 is a green LED, 12 is a blue LED, and 13 is a light guide. Also, 14 is a first photoelectric conversion element array, 15 is a first rod lens array, 201 is a second photoelectric conversion element array, 202 is a second rod lens array, and 16 is a first and a second rod lens array. It is a substrate on which a photoelectric conversion element array is mounted.
[0017]
On the substrate 16, the first photoelectric conversion element array 14 and the second photoelectric conversion element array 201 are arranged in parallel. In addition, the first rod lens array 15 is arranged so as to correspond to the first photoelectric conversion element array 14, and the second rod lens array 202 is arranged so as to correspond to the second photoelectric conversion element array 201. I have.
[0018]
FIG. 4 is a diagram for explaining the depth of field of the first rod lens array 15 and the second rod lens array 202.
[0019]
In FIG. 4A, Type A indicates a rod lens used in the first rod lens array 15 and Type B indicates a rod lens used in the second rod lens array 202. TC represents the distance (conjugate length) between the focal positions when Type A and Type B are viewed from the side. In this example, the conjugate length TC of Type A is 15.1 mm, and the conjugate length TC of Type B is 15.6 mm. The graph in FIG. 4B shows a change in the spatial frequency MTF when the focus position of Type A is away from the focus position by ΔL. Type B slightly changes slightly compared to Type A, but has almost the same characteristics.
[0020]
Here, the calculation formula of MTF is represented by the following formula (1).
MTF = (minimum white density−maximum black density) / (reference white density value−reference black density value) (1)
[0021]
In this embodiment, a document on which white and black lines drawn every 170 μm shown in FIG. 4C are drawn is placed at a position apart by ΔL and is calculated from the read image. The minimum white density value and the maximum black density value of the read image data and the density of the document are calculated as the reference white density and the reference black density.
[0022]
MTF is an index indicating the resolving power, but when ΔL increases, the image becomes blurred and the MTF value decreases. In the present embodiment, when the measurement is performed on a document on which a line of every 170 μm is drawn, if the MTF is 40% or more, it is within the practical range. As can be seen from the graph of FIG. 4B, the MTF peaks when ΔL = 0 mm and is about 82%, but when it is away from that position by about 0.25 mm, the MTF value becomes about 40% or less. .
[0023]
Next, an outline of the operation of the apparatus will be described.
[0024]
In FIG. 1, the stepping motor 2 is driven by the control board 5. This driving force is transmitted to the holder 101, that is, the reading unit 1 by the belt 3, and the reading unit 1 continuously moves along the platen glass 4 while reflecting the original or a film guide (or a film guide) placed on the platen glass 4. The transparent original (photographic film) 6 stored in the (film holder) 102 is scanned.
[0025]
Here, the photoelectric conversion element array and the rod lens array will be described. As shown in FIG. 2, the first photoelectric conversion element array 14 and the second photoelectric conversion element array 201 attached to the reading unit 1 are arranged so as to extend along the long axis direction of the reading unit 1. I have.
[0026]
In the case of the present embodiment, the first photoelectric conversion element array 14 is prepared for reading an A4 size reflection original. For this purpose, eight photoelectric conversion cells each having 645 elements are linearly arranged so that an A4 size document can be read at a density (resolution) equivalent to 600 DPI in the short direction (210 mm), and a total of 5160 pixels The photoelectric conversion elements are arranged on the substrate 16. This has a read image length (read width) of about 219 mm, and is suitable for reading while moving in parallel to the short direction of the A4 size.
[0027]
The first rod lens array 15 corresponding to the first photoelectric conversion element array 14 has an effective imaging range (imaging width) that is equal to the read image length (reading width) of the first photoelectric conversion element array 14. They are arranged so as to be approximately 219 mm.
[0028]
On the other hand, the second photoelectric conversion element array 201 is provided for reading a transparent original such as a 35 mm photographic film 6 at a high resolution and at a high speed. For this purpose, one photoelectric conversion cell having 2576 elements is provided so that it can be read at a density (resolution) equivalent to 2400 DPI. This is a read image length (read width) of about 27 mm, and since the size in the short direction of the 35 mm photographic film is about 24 mm, it is suitable for moving the 35 mm photographic film in parallel to the short direction and reading. ing. Further, since the read image length is short, the image transfer speed per line becomes faster and the cost can be reduced as compared with the case where the read image length is A4 size (210 mm) at 2400 DPI.
[0029]
The second rod lens array 202 corresponding to the second photoelectric conversion element array 201 has an effective imaging range (imaging width) that is equal to the read image length (reading width) of the second photoelectric conversion element array 201. They are arranged to be about the same 27 mm.
[0030]
First, a case of reading a reflection original will be described.
[0031]
FIG. 5 is a cross-sectional view of the apparatus when the reflection original 401 is read.
[0032]
Light emitted from the red LED 10, the green LED 11, and the blue LED 12 is guided by the light guide 13 in the major axis direction (longitudinal direction) of the reading unit 1 as shown in FIG. Irradiate. This light is reflected by the reflective original 401 placed on the upper surface of the original table glass 4, collected by the first rod lens array 15, and projected on the first photoelectric conversion element 14. As described above with reference to FIG. 4, the conjugate length (TC) of the first rod lens array 15 is 15.1 mm, and the upper surface of the platen glass 4 is 0 mm (the first focal position) and the photoelectric conversion element array 14. It is installed at a position where an optimum focus is formed on the upper side, and projects the image of the reflection original 401 onto the first photoelectric conversion element array 14 at the same magnification. Upon receiving the irradiation light of the LEDs 10, 11, and 12 reflected by the reflection original 401, electric charges are accumulated in the first photoelectric conversion element array 14, and the first photoelectric conversion element is read by a read start pulse (Hsync) in the next cycle. It is stored in a transfer unit in the array 14 and is output as an electric signal for each pixel by a pixel reading clock (Clock).
[0033]
Lighting of the red LED 10, the green LED 11, and the blue LED 12 is switched every reading start pulse (Hsync). As the reading unit 1 moves, the LEDs 10, 11, and 12 are sequentially turned on. Image signals separated and detected by the LEDs 10, 11, and 12 are sent from the control board 5 to the external computer 9 through the flat cable 8, and image processing is performed in the external computer 9.
[0034]
Next, a case where a 35 mm photographic film is read as a transparent original will be described.
[0035]
FIG. 6 is a configuration diagram of the film light source unit 103 and the film guide (film holder) 102 used when reading the 35 mm photographic film 6.
[0036]
The film light source unit 103 has therein a diffusion plate 17, a red LED 18 for a film, a green LED 19 for a film, and a blue LED 20 for a film. As the diffusion plate 17 of the present embodiment, for example, a surface light source described in JP-A-2001-34210 can be used. Light emitted from each LED is diffused by the diffusion plate 17, and uniform light is emitted from the lower surface of the diffusion plate in the figure. The diffusion plate 17 of this embodiment has a size of 50 mm × 25 mm, and can irradiate an effective image area for one frame of the 35 mm photographic film 6: about 36 mm × 24 mm.
[0037]
The 35 mm photographic film 6 is stored in the film guide 102. The film guide 102 is set on the platen glass 4 (not shown in FIG. 5). At this time, the 35 mm photographic film 6 reads the second photoelectric conversion element array 201 in the reading unit 1 effectively. It is installed to be within the range.
[0038]
FIG. 7 is a configuration diagram of the film guide 102. As shown in FIG. 7, a 35 mm photographic film 6 is set on a window frame 601 and fixed with a film clip 602. The thickness of the window frame is about 0.5 mm. As a result, when the 35 mm photographic film 6 is set on the platen glass 4, the 35 mm photographic film 6 is set at the second focal position on the platen glass 4 that is approximately 0.5 mm above the first focal position.
[0039]
FIG. 8 is a cross-sectional view of the apparatus when reading a 35 mm photographic film 6.
[0040]
Irradiation light from the film red LED 18, the film green LED 19, and the film blue LED 20, which is emitted from the film light source unit 103, passes through the 35 mm photographic film 6 at the second focal position, and the second rod lens array. The light is condensed by 202 and projected on the second photoelectric conversion element 201. As described above with reference to FIG. 4, the conjugate length (TC) of the second rod lens array 202 is 15.6 mm, the second focal position 0.5 mm away from the upper surface of the platen glass 4, and the photoelectric conversion. It is installed on the element array 201 at a position where an optimum focus is formed, and projects an image of the 35 mm photographic film 6 onto the second photoelectric conversion element array 201 at the same magnification. Upon receiving the light of the LEDs 18, 19, and 20 transmitted through the 35-mm photographic film 6, electric charges are accumulated in the second photoelectric conversion element array 201. Subsequent operations are the same as in the case of the reflection original described above. The output signal of the first photoelectric conversion element array used when reading a reflective original and the output signal of the second photoelectric conversion element array 201 used when reading a transparent original are both processed by the same processing circuit shown in FIG. It is processed.
[0041]
The 35 mm photographic film 6 is set so as to float about 0.5 mm from the platen glass 4. By using the second rod lens array 202, the focal position can be adjusted and the image is read with an appropriate resolution. be able to.
[0042]
As described above, according to the present embodiment, when reading a reflective original, an image reading element array having a resolution and a read image length suitable for the reflective original and a rod lens array having a focal length are used to read a transparent original. Sometimes, by using an image reading element array having a resolution and a read image length and a rod lens array having a focal length suitable for a transparent original, one image reading unit and an image reading apparatus using the same can be used as a reflection original. It is possible to read an image under optimum conditions for the original and the transparent original.
[0043]
Further, in reading a transparent original requiring a higher resolution than a reflective original, it is possible to minimize the length of a high-cost high-resolution reading element. As a result, the cost of the apparatus can be reduced and the reading speed can be improved as compared with the case where one long high-resolution reading element is used for both the reflection document and the transmission document.
[0044]
(Second embodiment)
FIG. 9 is a configuration diagram of the reading unit 1 according to the second embodiment. Although the basic configuration is the same as that of the first embodiment shown in FIG. 5, the second rod lens array 203 has the same conjugate length as that of the first rod lens array 15. different. Accordingly, instead of directly arranging the second photoelectric conversion element array 201 on the substrate 16 to which the first photoelectric conversion element array 14 is attached, a height adjustment member 204 having a thickness of about 0.5 mm is attached to the substrate 16. The second embodiment is different from the first embodiment in that the second photoelectric conversion element array 201 is mounted thereon. Other configurations are the same as those shown in FIG.
[0045]
FIG. 10 is a sectional view of the apparatus when reading the reflection original 401.
[0046]
Light emitted from the red LED 10, the green LED 11, and the blue LED 12 is guided by the light guide 13 in the long axis direction (longitudinal direction) of the reading unit 1 as shown in FIG. Irradiate. This light is reflected by the reflective original 401 placed on the upper surface of the original table glass 4, collected by the first rod lens array 15, and projected on the first photoelectric conversion element 14. The conjugate length (TC) of the first rod lens array 15 is 15.1 mm, and the first rod lens array 15 is set at a position where the upper surface of the platen glass 4 is 0 mm (first focal position) and the optimal focal point on the photoelectric conversion element array 14 Then, the image of the reflection document 401 is projected onto the first photoelectric conversion element array 14 at the same magnification.
Subsequent operations are the same as those in the first embodiment.
[0047]
FIG. 11 is a cross-sectional view of the apparatus when reading a 35 mm photographic film 6.
[0048]
Irradiation light from the film red LED 18, the film green LED 19, and the film blue LED 20, which is emitted from the film light source unit 103, passes through the 35 mm photographic film 6 at the second focal position, and the second rod lens array. The light is condensed by 202 and projected on the second photoelectric conversion element 201. The conjugate length (TC) of the second rod lens array 203 is 15.1 mm, which is the same as that of the first rod lens array 15, but the second focal position 0.5 mm away from the upper surface of the platen glass 4 and the photoelectric conversion. The second photoelectric conversion element array 201 is provided at a position shifted by about 0.5 mm from the first rod lens array 15 so as to focus on the element array 201 at an optimum focal point, and an image of the 35 mm photographic film 6 is made at the same magnification. Project on top. Upon receiving the light of the LEDs 18, 19, and 20 transmitted through the 35-mm photographic film 6, electric charges are accumulated in the second photoelectric conversion element array 201. Subsequent operations are the same as in the case of the reflection original described above.
[0049]
By using the second rod lens array 203, it is possible to read an image of the 35 mm photographic film 6 which is set up about 0.5 mm above the platen glass 4 with an appropriate resolution.
[0050]
【The invention's effect】
As described above, according to the present invention, it is possible to read an image under optimal conditions according to the document.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a basic configuration of an image reading apparatus according to a first embodiment of the present invention.
FIG. 2 is a configuration block diagram of a processing circuit of the image reading device according to the first embodiment of the present invention.
FIG. 3 is a configuration diagram of a reading unit of the image reading apparatus according to the first embodiment of the present invention.
FIG. 4 is a diagram illustrating characteristics of a rod lens of the reading unit according to the first embodiment of the present invention.
FIG. 5 is a cross-sectional view of a configuration when reading a reflection original according to the first embodiment of the present invention.
FIG. 6 is a configuration diagram of reading a 35 mm photographic film according to the first embodiment of the present invention.
FIG. 7 is a diagram illustrating a method of mounting a 35 mm photographic film on a film guide according to the first embodiment of the present invention.
FIG. 8 is a sectional view of a 35 mm photographic film reading configuration according to the first embodiment of the present invention.
FIG. 9 is a configuration diagram of a reading unit of an image reading device according to a second embodiment of the present invention.
FIG. 10 is a cross-sectional view of a configuration when reading a reflective original according to a second embodiment of the present invention.
FIG. 11 is a sectional view of a 35 mm photographic film reading configuration according to a second embodiment of the present invention.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 reading unit 2 stepping motor 3 belt 4 platen glass 5 control board 6 35 mm photographic film 7 white reference plate / document control plate 8 flat cable 9 external computer 10 red LED
11 Green LED
12 Blue LED
13 light guide 14 first photoelectric conversion element array 15 first rod lens array 16 substrate 17 diffusion plate 18 red LED for film
19 Green LED for film
20 Blue LED for film
101 Holder 102 Guide (film holder)
103 Film light source unit 104 Cable 105 Document regulating plate 201 Second photoelectric conversion element array 202 Second rod lens array 203 Second rod lens array 401 Reflected document

Claims (12)

A first image reading element array in which a plurality of photoelectric conversion elements are arranged in a line,
A second image reading element array in which a plurality of photoelectric conversion elements are arranged in a line in parallel with the first image reading element array;
A first lens that forms an image of a first document at a first focal position on the image reading element array in the first row;
A second original image having a conjugate length different from that of the first lens and located at a second focal position different from the first focal position on the image reading element array in the second row; Lens and
An image reading unit comprising: The image reading unit according to claim 1, wherein a conjugate length of the second lens is longer than a conjugate length of the first lens. A first image reading element array in which a plurality of photoelectric conversion elements are arranged in a line,
A plurality of photoelectric conversion elements arranged in a line in parallel with the first image reading element array, and a second image reading element array having a higher resolution than the first image reading element array;
A first lens that forms an image of a first document at a first focal position on the image reading element array in the first row;
A second lens that forms a second document image at a second focal position different from the first focal position on the image reading element array in the second row;
An image reading unit comprising: The image reading unit according to claim 1, wherein the second image reading element array has a higher resolution than the first image reading element array. The image reading unit according to any one of claims 1 to 4, wherein the second image reading element array has a shorter effective reading width than the first image reading element array. The image reading unit according to claim 5, wherein the second lens has a smaller effective image forming range than the first lens. The image reading unit according to claim 1, wherein the first and second image reading element arrays are provided on a same substrate. The image reading unit according to any one of claims 1 to 7, wherein the first and second lenses include a rod lens array. 9. The image reading unit according to claim 1, wherein the first document image is a reflection document image, and the second document image is a transmission document image. An image reading unit according to any one of claims 1 to 9, and a moving unit that relatively moves the image reading unit and the first document image or the second document image. An image reading apparatus, comprising: The document further has a document table on which the document is placed. The first document is directly placed on the document table, and the second document is stored in a predetermined holder at a predetermined position on the document table. The image reading device according to claim 10, wherein the image reading device is mounted. 12. The image according to claim 10, further comprising: a first illuminator for illuminating the first original image; and a second illuminator for illuminating the second original image. Reader.

Images