JPS63191466A - Image reader with increased photodetection cell width - Google Patents

Abstract

PURPOSE:To eliminate deterioration in the read quality of an image due to a deviation in alignment by supplying only an image on a read line to be read to a linear image sensor side and widening the photodetection range of the linear image sensor itself. CONSTITUTION:The subscanning-directional width (d) of a slit hole 14 is determined according to the subscanning-directional width Y of a preset read line RD. Namely, the width (d) of the slit hole 14 is so determined that only an image present in the read line RD is formed in the slit hole 14. The width DY in a direction (subscanning direction Y) perpendicular to the array direction of photodetection cells 16, on the other hand, is set larger than the luminous flux width DF in the subscanning direction Y of image forming luminous flux LG on a photodetection surface. Consequently, the read quality of an image is prevented from deteriorating owing to a deviation in the alignment of respective members.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image reading device that sequentially reads an image of an original image for each color component using a plurality of linear image sensors. This invention relates to technology for preventing the effects of misalignment.

(Prior Art and its Problems) In a color scanner for plate making, etc., it is necessary to read an image of an original in scanning line sequence for each color component. For this reason,
In such a system, light from the original image is separated into three color components: red (R color), blue (B color), and green (G color), and each is photoelectrically converted using a separate linear image sensor. An image reading device is used.

FIG. 15 is a layout diagram showing a conventional example of such an image reading device. The image reading device 2 includes an imaging lens system 3, and at each point in time, light from the reading line RD along the main scanning direction X of the original image 1 passes through the imaging lens system 3 to the image reading device 3. be taken into the body.

This light is separated into three directions by the first and second half mirrors 4a and 4b into three imaging light beams LR, LB, and LG.
becomes. These imaging light beams LR.

In the direction of movement of LB and LG, there are R, B, and G colors.
Filters 5R and 5B extract each color component.

5G is installed. Furthermore, each filter 5R.

Behind 5B and 5G is a linear image sensor 6R.

6B and 6G are provided respectively. The linear image sensors 6R, 6B, and 6G include a one-dimensional array of light-receiving cells, and a filter 5R.

The intensity of the R color component light, B color component light, and G color component light provided through 5B and 5G is read respectively.

Further, the image reading device 2 and the original image 1 move relative to each other at a speed V along the sub-scanning direction Y. For this reason, each linear image sensor 6R, 6B, 6G during a predetermined time Δt.
The band-shaped area ViS that receives light becomes one scanning line. Then, by repeating image reading for each scanning line as described above and continuing the relative movement between the original 1 and the image reading device 2, the entire image of the original 1 is sequentially read.

Incidentally, in such an image reading device 2, linear image sensors 6R, 6B, 6G and half mirrors 4a, 4.
When a deviation occurs in the alignment of each linear image sensor 6R, 6B.

A shift occurs in the position of each reading line read at 6G. This situation is schematically shown in FIG. 16, in which each linear image sensor 6R, 6B should originally read image information on the same reading line.

6G takes in image information from mutually different reading lines RR, RB, and RG. As a result, if the image information of the original image 1 read by each of the linear image sensors 6R, 6B, and 6G is combined to reproduce an image, there is a problem in that image quality deteriorates, such as color shift.

Such misalignment occurs when the device is assembled, but it also occurs after assembly due to expansion due to temperature changes and mechanical deformation during transfer. Therefore, it is difficult to solve this problem by carefully performing assembly and adjustment. Furthermore, since the reading position of the original image 1 itself is shifted, a faithfully reproduced image cannot be obtained even if signal processing such as color masking is performed.

Such problems typically appear in devices that require particularly high-precision image reading, such as color scanners for plate making, but they also occur in devices that read color images, such as color facsimiles and color copiers. This is a general problem.

(Object of the Invention) The present invention is intended to overcome the above-mentioned problems in the prior art, and aims to provide an image reading device in which image reading quality is not degraded due to misalignment of each member. .

(Means for Achieving the Object) In order to achieve the above-mentioned object, the present invention provides an image reading device that sequentially reads an image of an original for each color component using a plurality of linear image sensors in the (aJ main scanning direction). a light regulating member having a band-shaped light regulating window extending to (b
) a first imaging optical system that forms an image of the original image at the position of the light regulating member; and (c) a first imaging optical system that is inserted in an optical path from the light regulating member to the linear image sensor, a second imaging optical system that further forms images of the light flux passing through the window on the light receiving surfaces of the plurality of linear image sensors; (d)
The plurality of linear image sensors are provided as the plurality of linear image sensors that receive the imaging light flux from the second imaging optical system, and the width of the light receiving cell surface in the sub-scanning direction is defined as the width of the light-receiving cell surface in the sub-scanning direction of the imaging light flux on the light-receiving surface. A plurality of linear image sensors set to have a width larger than the luminous flux width are arranged.

However, the term "main scanning direction" in this specification does not refer only to a direction spatially parallel to the main scanning direction of an original image, but is a term indicating all directions corresponding to main scanning. Therefore, for example, even if the arrangement direction of the light receiving cells in the linear image sensor is not spatially parallel to the main scanning direction of the original image due to a mirror, etc., the arrangement direction of the light receiving cells can be adjusted. This is called the "main scanning direction" in a linear image sensor.

The same applies to the "sub-scanning direction", which refers to a direction perpendicular to the "main-scanning direction" in the broad sense described above.

(Example) A. Structure of Example FIG. 1A and FIG. 1B are a perspective layout view and a front layout view, respectively, of an example of the present invention.

The configuration of the image reading device 10 shown in these figures differs from the conventional device 2 shown in FIG. 15 in the following points.

First, in the apparatus 10 of the embodiment, three CODs from the original image 1 are
Linear image sensor 15R, 15B.

Slit 1 as a light regulating member in the optical path up to 15G
2 and a first imaging lens system 11 that forms an image of the original image 1 at the position of this slit 12. This slit 12 has a slit hole 1 as a band-shaped light regulating window.
4 is provided, and the width d of this slit hole 14 in the sub-scanning direction is determined according to the preset sub-scanning width ΔY of the reading line RD. That is, the width d of the slit hole 14 is determined so that only the image existing inside the reading line RD is formed inside the slit hole 14.

On the other hand, a second imaging lens system 13 is located behind the slit 12.
is provided. This second imaging lens system 13 focuses on the slit hole 14 of the image formed at the position of the slit 12.
Only the light flux passing through the linear image sensor 15R, 1
It is provided to re-image at the positions of the light receiving surfaces of 5B and 15G.

Therefore, linear image sensors 15R, 158, 1
Only the image existing inside the reading line RD is re-imaged on the 5G light receiving surface.

Half mirror 4a shown in FIG. 1A and FIG. 1B,
4b and filters 5R, 5B, and 5G are similar to those provided in the conventional device 2 of FIG. On the other hand, COD linear image sensors 15R, 15B
, 15G (the arrangement position is the same as that of conventional device 2) has a new light receiving structure. That is,
As shown as a partial diagram in FIG.
Although it includes a dimensional array, the size of the cell surface of this light receiving cell 16 is as follows.

First, as shown in FIG. 3(a), the width DX of the light receiving cell surface in the arrangement direction (main scanning direction X) of the light receiving cells 16 is the same as that of the conventional light receiving cell (FIG. 3(b)) It is. However, the width DY in the direction perpendicular to the arrangement direction (sub-scanning direction Y) is the width of the imaging light beam L on the light receiving surface.
It is set larger than the beam width DF of G in the sub-scanning direction Y. The extent to which the width DY of the cell surface is increased relative to the beam width DF is determined depending on the expected value of the degree of misalignment of each member, but in this example, the width DY of the light receiving cell surface is It is approximately several times the width DF.

Although not shown, in this image reading device 10, the linear image sensors 15R115B, 15G, etc. are arranged in the outer casing so that no light enters from any other than the slit hole 14.

B. Operation of the Embodiment Next, the operation of the embodiment having such a configuration will be explained, focusing on its characteristic parts.

(a) When there is no deviation in alignment If there is no deviation in the alignment of each member, the light LO from the image inside the reading line RD formed at the position of the slit hole 14 (FIG. 1A).

1B> is separated into each combined light beam LR, LB, and LG, and is irradiated near the center of the cell surface of each light-receiving cell 16, as shown in FIG. 3(a). However, other parts of the light-receiving cell surface are not illuminated with light. For this reason, linear image sensors 15R and 15B.

15G outputs an image reading signal (color separation signal) corresponding to the intensity of each color component of the image inside the reading line RD.

(b) When a misalignment occurs In this case, each of the imaging light beams LR, LB, and LG is shifted from the center of the light-receiving surface of the linear image sensors 15R, 15B, and 15G (for example, as shown in FIG. The image is formed at the position shown). However, since the width DY of the light-receiving cell 16 is set larger than the beam width DF, all of the imaging beams LR, LB, and LG are irradiated within the light-receivable range of the linear image sensors 15R, 15B, and 15G. An image reading signal similar to that shown in FIG. 3(a) is obtained.

Furthermore, even if the incident positions of the imaging light beams LR, LB, and LG are shifted in this way, the linear image sensor 15R,
It is important that the light detected by 15B and 15G is all light emitted from the image inside the reading IRD. In other words, a real image of the image inside the reading line RD is formed at the position of the slit hole 14 in FIG. The image is focused on the part. Therefore, the light transmitted to the rear of the slit 12 (to the right in FIG. 1B) is ii! inside the reading line RD. It is only the light from the real image of the ii image.

Therefore, unlike the conventional example shown in FIG. 15 and explained in FIG. Image light flux LR, LB, LG
are all lights obtained by separating the light 10 emitted from the same region (region inside the reading line RD). In other words, since the light LO emitted from the slit hole 14 contains only the image information inside the reading line RD, no matter what alignment is used to receive this light, light from other areas of the original image 1 will be received. That is not the case.

Through the above operations, each linear image sensor 15R,
Image reading signals reflecting the image information inside the same reading line RD are output from 15B and 15G. Therefore, even when the image of the original image 1 is reproduced by combining these signals, phenomena such as color shift do not occur.

Note that when changing the reading resolution in the sub-scanning direction, 1
It is sufficient to change the sub-scanning speed V while keeping the reading period Δt per pixel fixed. Then, the sub-scanning width (
(2) As Δt) changes, the size of the pixel also changes. In this case, since the light O passing through the slit hole 14 at each time point is the light from the image at the position of the reading line RD at that time point, even if the resolution is changed in this way, the scanning line S Image information from outside will not enter.

C1 Processing for misalignment in the main scanning direction By the way, in the above configuration, the influence of misalignment in the sub-scanning direction Y is prevented, but in the arrangement direction of the light receiving cells 16, that is, in the main scanning direction It is also desirable to take measures in case of misalignment.

Therefore, in this embodiment, the linear image sensor 15R
, 15B, and 15G, the influence of deviation in the main scanning direction is also prevented.

FIG. 5 is a block diagram showing an example of a signal processing circuit configured for such a purpose. In FIG. 5, image reading signals from linear image sensors 15R, 15B, and 15G are transmitted to analog delay circuits 2OR, 20B, and
are outputted to the color calculation circuit 21 via the respective ones. Of these, the color calculation circuit 21 combines the input signals at a predetermined ratio for each pixel and converts them into a set of color signals used for image recording and the like. In the illustrated example, each color signal of yellow Y, magenta M, cyan C, and black, which corresponds to the ink signal of a color scanner for plate making, is calculated and determined.

Further, the delay times 1R, 1B, and 16 in each of the delay circuits 2OR, 20B, and 20G correspond to the respective image sensors 15R, 15B when reading an image using a test chart or the like as the original image 1.

This is determined experimentally by calculating the amount of positional deviation in reading the 15G image reading signal. That is, when the image formation position shifts in the main scanning direction X as shown in FIG. 6, output shift times T and T2 of the image reading signal as shown in FIG. 7 occur in reading the test chart. However, t is the passage of time, and E, E, and E6 are each R color.

This is the image reading level for 8 B colors and G color. Therefore, according to the output deviation times T, T, 2, the delay times 1R, 1
B, 16, t = T + T, t = T2. tG=O12
Set it like B. Then, even if an image reading signal as shown in FIG. 8 is output from the linear image sensors 5R, 15B, and 15G during actual reading of an original image, it will be outputted as shown in FIG. 9 by passing through the delay circuits 2OR, 20B, and 20G. A consistent image reading signal is output to the color calculation circuit 21. This effectively prevents the influence of misalignment in the main scanning direction X.

FIG. 10 is a block diagram showing an example of a circuit that digitally performs such a delay. In this circuit, image reading signals from linear image sensors 15R, 15B, and 15G are digitized by an A/D converter 22, and then output to a digital color calculation circuit 24 via shift registers 23R, 23B, and 23G, respectively. . These signal transfers are performed using the timing control signal φ from the timing control circuit 25.
controlled by

In the case of this circuit, shift register 23R9238,
By making the number of 23G stages different from each other, a relative delay can be given to the output timing of the image reading signal for each color component. The delay time may be determined in the same manner as in the circuit shown in FIG. 5 described above.

Also, without using a delay circuit or shift register, the start of the COD read clock can be made earlier or later for each COD element according to the delay time.
A similar effect can be obtained.

Furthermore, although not shown, a substantial delay can be achieved by temporarily storing image reading signals for each color in a memory and using a different address for each color component to access when reading out the signals. good.

D. Effects of alignment deviations In this way, the effects of alignment deviations in both the main scanning direction and the sub-scanning direction can be prevented, but there are other types of alignment deviations, such as tilt deviations. . However, in the device configured according to the present invention, the influence of such tilt shift can be prevented. In other words, even if there is a tilt shift in the alignment,
The imaging light beam LG from the image on the reading line RD forms an image on the light receiving surface of the linear image sensor 15G (15R, 15B as well) in a positional relationship as shown in FIG. 11(a).

However, in FIG. 11(a), for the purpose of facilitating beating, a broken line 1, which corresponds to the pixel boundary when no misalignment has occurred, is virtually drawn in the image of the imaging light beam LG. It is. As shown in Figure 1 (J-), even if some tilt deviation occurs in the alignment, it has almost no effect on the correspondence between the pixels of the image read by the linear image sensor 15G.As a result, the problem of tilt deviation occurs. will also be effectively abolished.

On the other hand, in the conventional device as shown in FIG.
Not only the imaging light beam LG from the image on the reading line RD, but also the light L from the surrounding image as shown in FIG. 11(b).
W is imaged near the position where the linear image sensor 6G is arranged. For this reason, when a tilt shift occurs, the image information of the square area of the original image 1 is captured by the linear image sensor 6G, increasing the error in image reading. Therefore, the ability to prevent the influence of tilt deviation is one of the major features of the present invention.

E. Comparison with Reference Technique and Modification By the way, as a technique for preventing the influence of misalignment, a device as shown in FIG. 12 can also be considered. In this device, instead of the second imaging lens system 13 shown in FIG. 1A, an anisotropic lens system is used in which the first focal length in the main scanning direction A toroidal lens 30 is used as an optical system. and,
The 15th linear image sensor 6R, 6B, 6G
A sensor similar to the conventional one as shown in the figure is used, and these light receiving surfaces are arranged at an imaging position corresponding to the first focal length. Then, as shown in FIG.
The light flux passing through the linear image sensor 6G (6R,
The same goes for 6B. ), an image is formed in the main scanning direction X, whereas a light beam is deviated from the focal point in the sub-scanning direction Y. In other words, the 14th
When the image 11 as shown in Fig. 14 (a) is on the reading line RD of the original image 1, the image I2 that is blurred and enlarged in the sub-scanning direction Y as shown in Fig. 14 (b) is the light received by the linear image sensor 6G. It is formed near the surface 31. Therefore, even if the alignment of the linear image sensor 6G deviates along the sub-scanning direction Y, almost the same image will be given to the light receiving surface 31 of this linear image sensor 6G, thereby preventing the influence of the alignment deviation. be able to.

However, in the case of such a device, since the light is received with the light beam spread out along the sub-scanning direction Y, the intensity of the light received by the linear image sensor 6G is reduced to some extent.

Therefore, although such a device has superior properties to the conventional device, it can be seen that the device of the present invention is even more desirable.

Note that the present invention is not limited to the embodiments described above, and the following modifications are possible, for example.

(2) In the above embodiment, Surins 1 to 12 are used, but other light regulating members may be used as long as they have a band-shaped light regulating window corresponding to the reading line RD. An example of such a device is one in which a light blocking layer is provided on the surface of a transparent substrate, and a portion of the light blocking layer is removed in a band shape to form a light regulating window. Imaging light beams LR, LG.

The means for separating into 1B may also be a combination of prisms.

■This invention is applicable not only to plate-making scanners but also to image reading devices used in facsimiles, copying machines, and the like.

(Effects of the Invention) As explained above, according to the present invention, only the image on the reading line to be read is provided to the linear image sensor side, and the light receiving range of the linear image sensor itself is widened. Even if misalignment occurs, image information on the same reading line is captured by each linear image sensor. Therefore, it is possible to obtain an image reading device in which the image reading quality does not deteriorate due to misalignment.

[Brief explanation of the drawing]

1A and 1B are respectively a perspective layout view and a front layout view of an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between the light receiving surface of the linear image sensor and the imaging position, and FIG. is an explanatory diagram showing the configuration of the cell surface of the light-receiving cell in the example in comparison with a conventional example; FIG. 4 is an explanatory diagram of the light-receiving position when a misalignment occurs; FIGS. 5 and 10 are A diagram showing an example of a circuit that processes deviations in the main scanning direction. FIGS. 6 to 9 are explanatory diagrams of how to set the delay time. FIG. Figures 12 to 14 are illustrations of the reference technology, Figures 15 and 16, which are shown in comparison with the case.
The figure is an explanatory diagram of a conventional image reading device. 1...Original picture, 4a, 4b...Half mirror-1
5R, 5B, 5G... Filter, 10... Image reading device, 11... First imaging lens system, 12... Slit (light regulating member), 13... Second imaging Lens system, 14... Slit hole (light regulation window), 15R, 15B, 15G... Linear image sensor, 16... Light receiving cell, LR, LB, LG... Partial light flux, RD... Reading line, S...scanning line

Claims (2)

[Claims] (1) In an image reading device that sequentially reads an image of an original image for each color component in scanning line sequence using a plurality of linear image sensors, (a) a light regulating member having a band-shaped light regulating window extending in the main scanning direction; (b) a first imaging optical system that forms an image of the original image at the position of the light regulating member; (c) a first imaging optical system that is inserted in the optical path from the light regulating member to the linear image sensor, and the light regulating window; (d) a second imaging optical system that further forms an image of the passing light flux on the light receiving surface of the plurality of linear image sensors; and (d) a second imaging optical system that receives the imaging light flux from the second imaging optical system. A plurality of linear image sensors are arranged as linear image sensors, and the width of the light-receiving cell surface in the sub-scanning direction is set larger than the light beam width in the sub-scanning direction of the imaging light beam on the light-receiving surface. An image reading device featuring a large light-receiving cell width. (2) Delay means for relatively delaying the output timing of each of the image reading signals by the plurality of linear image sensors according to the amount of positional deviation in reading in the main scanning direction between the plurality of linear image sensors is provided. Furthermore, an image reading device in which the width of the light-receiving cell is increased according to claim 1.