JPH10308844A - Magnification image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the magnification image reader with a simple configuration by which image information is magnified and read with high accuracy without missing of information. SOLUTION: A reflected light of an original 2 lighted by a lighting system is formed by a reduction image forming lens 5, and a line sensor 6 that is configured by arranging at least two line sensors with a different pixel size in a subscanning direction applies photoelectric-conversion to an image of an original 2 formed by the reduction image forming lens 5. For example, the reduction/magnification is conducted by using an optical system having a line sensor 6-a for unmagnification reading and pluralities of line sensors (6-b, 6-c) whose pixel size is larger than that of the unmagnification line sensor. Thus, it is possible to read image information without thinning-out pixels even in the case of a smaller magnification resulting that a magnified image with high accuracy is obtained. Moreover, a variable range of a scanning speed in the subscanning speed is enough to be smaller than that of a conventional reader and the motor cost is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable-magnification image reading apparatus used for a scanner, a copying machine, a facsimile, and the like, and more particularly, to a variable-magnification image reading apparatus of an original reading optical system.

[0002]

2. Description of the Related Art Conventionally, a variable-magnification image reading apparatus is generally applied to an image reading apparatus such as a scanner, a copying machine, and a facsimile. As an optical system in these apparatuses, there is a reduction reading optical system for reducing and forming an image of reflected light of a document illuminated by an illumination system on a line sensor by an imaging lens.
In such an image reading apparatus, as a method of reading the image information by changing the magnification to an arbitrary magnification, a so-called optical scaling is performed in which the position of the imaging lens is changed to change the reduction ratio of the optical system to perform the magnification. Magnification and electric scaling that electrically changes the magnification using the output signal of the line sensor.

In a conventional image reading apparatus using a reduced reading optical system, as shown in FIG. 4, an original 2 is arranged on a contact glass 1 and an illumination optical system is arranged below the contact glass 1. The original is illuminated by a system (not shown). The illumination light of the document is reflected by the first mirror (3-a) of the first traveling body 3, and thereafter, the first mirror (4-a) and the second mirror (4-b) of the second traveling body 4 And is guided to the reduction imaging lens 5, and this reduction imaging lens 5
Thus, an image is formed on the line sensor 6. When reading the longitudinal direction (sub-scanning direction) of the document 2, the first traveling body 3
To the position 3 'at the speed of
Moves to the position 4 ′ at half the speed of the first traveling body 3 ＶV, and reads the entire original 2.

[0004] On the line sensor 6, n pixels of size P are arranged at the location of the symbol (6-a). The contraction ratio m of the optical system is uniquely determined by the following equation using the reading density D and the pixel size P.

M = D (dpi) × P / 25.4

The total number of pixels n is obtained from the reading density D and the reading width L of the document in the main scanning direction by the following equation.

N = Y × D / 25.4

For example, if the reading density is 400 dpi, the number of pixels of the line sensor is 7 μm, and the reading width of the original in the main scanning direction is 30
When it is 4.8 mm, the following is obtained.

M = 400 × 0.007 / 25.4 = 0.102 n = 304.8 × 400 / 25.4 = 4800 pixels

[0010] As described in the "image reading apparatus" of JP-A-4-15260 of the prior art 1, in general, when reading at an arbitrary magnification, the optical magnification is changed to change the contraction ratio of the optical system. Is capable of reading image information with high accuracy without loss of information.

[0011]

However, in the optical system as in the above-mentioned conventional example, one dot corresponding to the reading density on the original corresponds to one pixel of the line sensor to read the original information. In the case where the read document information is electrically reduced / magnified, the read pixels are shifted in the main scanning direction in accordance with the magnification to reduce the size.

FIG. 5 shows an example in which the magnification is set to 0.7. The read document information is displayed on the line sensor as 1
Up to the nth. This information is obtained by electrical correction.
The information of the reading width L is reduced to L × 0.7 times by overlapping by shifting three dots.

The magnification change in the sub-scanning direction is dealt with by increasing the speed of the traveling body to 1 / 0.7 times the original size. When the reduction ratio of the magnification is small as described above, the magnification can be changed by shifting each dot. However, when the reduction ratio is 0.5 or less, the main scanning direction is set to 2 as shown in FIG. Since scaling is performed by thinning out the third dot and shifting the third dot by one dot, loss of image information occurs. In addition, the speed in the sub-scanning direction must be twice or more as high as that at the time of equal magnification, and the load on the drive motor increases.

As is clear from Japanese Patent Application Laid-Open No. Hei 4-15260 of Conventional Example 1, complicated means for changing the magnification of the optical system is required, resulting in an increase in cost.

On the other hand, electric zooming is simpler in construction than optical zooming and can achieve low cost. However, when performing variable magnification, especially at the time of reduction of 0.5 times or less, pixels are thinned out and read, so that there is a defect that information is lost and high-precision reading cannot be performed.

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a variable-magnification image reading apparatus which has a simple structure, and which reads image information with high accuracy without loss of information.

[0017]

In order to achieve the above object, a variable-magnification image reading apparatus according to the present invention forms an illumination system for illuminating a document, and reduces and forms an image of reflected light of the document illuminated by the illumination system. An imaging lens and at least two different pixel sizes
It is characterized by having an image reading optical system consisting of a line sensor in which the individual lines are arranged in the sub-scanning direction and which photoelectrically converts the image of the original image formed by the imaging lens.

Further, the line sensor has a minimum pixel size at the time of the same-size reading as a reference, and has a smaller pixel size at other magnifications than that at the same-size reading as a reference.
It is better to configure it as an integral multiple of.

[0019]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a variable-magnification image reading apparatus according to an embodiment of the present invention;
1 to 3 show an embodiment of a variable-magnification image reading apparatus according to the present invention. The variable-magnification image reading apparatus according to the present embodiment shows an example in which three line sensors are provided.

In FIG. 1, a document 2 is arranged on a contact glass 1. The original 2 is illuminated by an illumination optical system (not shown) arranged below the contact glass 1. The illumination light of the document 2 is reflected by the first mirror (3-a) of the first traveling body 3, and thereafter, the first mirror (4-a) and the second mirror (4-b) of the second traveling body 4. And is guided to the reduction imaging lens 5, and is imaged on the line sensor 6 by the reduction imaging lens 5.

When reading the longitudinal direction (sub-scanning direction) of the original 2, the first traveling body 3 moves to the position 3 'at the speed V,
At the same time, the second traveling body 4 moves to the position 4 ′ at half the speed of the first traveling body 3 １ ／ V, and reads the entire document 2.

On the line sensor 6, pixels (6-a) for reading an image at the same magnification as in the prior art are arranged with a size P and a total of n pixels. In the present embodiment, the pixel (6-a) is interposed at the position in the sub-scanning direction, and the pixel (6-b) and the pixel (6-c) are arranged in the sub-scanning direction.

These pixels (6-a) and (6-a)
b), the pixel size and the total number of pixels of the pixel (6-c) are minimized at the pitch P of the pixel (6-a) at the same magnification, as shown in FIG. Is twice the pitch 2
P, the pixel (6-c) has a pitch 4P that is four times as large as an integer multiple of two. The total number of pixels is the maximum when n pixels (6-a) at the same magnification are n and the pixel (6-b) is ｎ times n / 2
And the number of pixels (6-c) is 1/4 times n / 4. The case where the magnification is changed at the same magnification and at a reduction ratio larger than 0.5 is the same as the above-mentioned conventional case.

At the time of magnification change of 0.5 times when information thinning is performed, as shown in FIG. 3, image information is read using a signal from the line sensor of the pixel (6-b). The pixel size of the pixel (6-b) is twice as large in both the main and sub directions as the pixel (6-a). For this reason,
In the main scanning direction, information of two dots is projected on one pixel of the line sensor. By using this information as one pixel, it is possible to read the original information at a magnification of 0.5.
At this time, since two lines are also projected on one pixel in the sub-scanning direction, reading at the same speed as in the case of the same magnification makes 0.
It is possible to read image information that has been magnified five times.

When using the line sensor of the pixel (6-b) to change the magnification from 0.5 to a smaller scale, the pixel is shifted in the main scanning direction and the traveling direction is changed in the sub scanning direction as in the conventional method. Speed up your body and zoom. And 0.25
If it is doubled and it becomes necessary to thin out the pixels again, the pixel (6
-Use the signal from c). The pixel (6-c) has twice the pixel size of both the main and sub-pixels of the line sensor of the pixel (6-b), and the pixel (6-a) is changed from the pixel (6-a) to the pixel (6-b). In the same manner, a zoomed image of 0.25 times can be obtained at the same speed as the sub-scanning speed.

In the above-described embodiment, reduction / magnification is performed using an optical system having a line sensor for reading at the same magnification and a plurality of line sensors having a larger pixel size than the line sensor for the same magnification. This makes it possible to read image information without thinning out the pixels even at a small scaling factor where pixels need to be thinned to perform zooming, and a highly accurate zoomed image can be obtained. can get. In addition, the variable range of the scanning speed in the sub-scanning direction can be reduced as compared with the related art, the load on the drive motor can be reduced, and the cost of the motor can be reduced.

In particular, by increasing the pixel size of the other line sensors to an integral multiple of 2 with respect to the unity magnification, the number of line sensors can be minimized. A device is obtained.

In this embodiment, the case where the number of line sensors is three has been described, but it goes without saying that any number of line sensors may be used as long as the number is two or more.

[0029]

As is clear from the above description, the variable-magnification image reading apparatus of the present invention reduces and forms the reflected light of the original illuminated by the illumination system so that at least two lines having different pixel sizes are formed. The image of the document arranged in the sub-scanning direction and formed by the image forming lens is photoelectrically converted. For example, reduction / magnification is performed using an optical system having a line sensor for reading at the same magnification and a plurality of line sensors having a pixel size larger than that of the line sensor for the same magnification. This makes it possible to read image information without thinning out pixels even at a small magnification, such as when it is necessary to reduce the magnification by thinning out the pixels. Is obtained. In addition, the variable range of the scanning speed in the sub-scanning direction can be reduced as compared with the related art,
The load on the drive motor can be reduced, and the cost of the motor can be reduced.

In particular, by setting the pixel size of the other line sensor to an integral multiple of 2 for the same magnification, the number of line sensors can be minimized, and a low-cost, simple-structured variable-magnification image reading apparatus can be used. A device is obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a configuration example of an optical system of an embodiment of a variable-magnification image reading apparatus according to the present invention.

FIG. 2 is a diagram for describing a configuration example of a line sensor.

FIG. 3 is a diagram for explaining a procedure for reading image information.

FIG. 4 is a conceptual diagram showing a configuration example of an optical system of a conventional variable-magnification image reading device.

FIG. 5 is a diagram for explaining a first example of a conventional image information reading procedure.

FIG. 6 is a diagram for explaining a second example of a conventional image information reading procedure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Contact glass 2 Original 3 First running body 3-a 1st mirror 4 2nd running body 4-a 2nd running body 4-b 2nd mirror 5 Reduction imaging lens 6 Line sensor

Claims (3)

[Claims] 1. An illumination system for illuminating a document, an imaging lens for reducing and imaging reflected light of the document illuminated by the illumination system, and at least two lines having different pixel sizes are arranged in the sub-scanning direction. A variable-magnification image reading apparatus, comprising: an image reading optical system including a line sensor that photoelectrically converts the image of the document formed by the imaging lens. 2. The variable-magnification image reading device according to claim 1, wherein the line sensor has a minimum pixel size at the time of the same-size reading as a reference. 3. The variable-magnification image reading device according to claim 2, wherein the line sensor is configured such that a pixel size at another magnification is an integral multiple of 2 with respect to the reference equal-magnification reading. .