JPH0537725A - Picture reader - Google Patents

Abstract

PURPOSE:To execute reading with small color deviation due to a vibration number caused by a reduction mechanism by setting an interval of three lines at the subscanning to be a value being a prescribed multiple of a frequency resulting from a period of speed fluctuation in the subscanning. CONSTITUTION:In the picture reader using a 3-line sensor, the vibration caused by the reduction mechanism used between a scanner motor 115 and a drive pulley 114 of a scanner driver linked to a drive pulley 114 linked with a 1st scanner 111 and a 2nd scanner 112 with a wire 113 is set to a twice the frequency resulting from one period of the speed fluctuation of the subscanning due to interval of three lines and in the vicinity thereof. Thus, the effect of the position deviation due to the periodic speed fluctuation of the scanner onto the picture read is reduced and the reading with small color deviation is attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus capable of reading a color original, and more specifically, at the same time, the R, G, and B line sensors in the sub-scanning direction detect different positions on the original. The present invention relates to an image reading device using a 3-line sensor for reading.

[0002]

2. Description of the Related Art As a conventional image reading apparatus capable of reading a color original, there are, for example, a dichroic prism type and a 1 × color CCD sensor type.

In the dichroic prism system, the same optical axis is split into three by a dichroic prism and each light is CC
As shown in FIG. 6, an original 602 placed on a contact glass 601 is converted into a white light source 6 by a photoelectric conversion method using D.
03, and the reflected light is reflected by the mirror 604 and the lens 6
Incident on the dichroic prism 606 via 05,
Blue is reflected by the first prism 606a and is photoelectrically converted by the CCD 607 as blue light, and red is reflected by the second prism 606b and is photoelectrically converted by CCD 608 as red light. Finally, blue light and red light are removed from the incident light. The third prism 606c serves as the green light and the CCD 6
Photoelectric conversion is performed in 09, and color separation of Red, Green, and Blue is performed. As a characteristic of this method, since the same optical axis is used, there is no angle dependency with respect to the document surface, which is advantageous for document lifting.

In the same-size color sensor system, the red, green, and blue photoelements of the same-size sensor are used.
7 is arranged by the method of simultaneously performing color separation and photoelectric conversion, as shown in FIG. 7A.
A white light source 703 irradiates a document 702 placed on the image forming apparatus 1 and the reflected light is imaged on a 1 × color sensor 705 via a 1 × image forming element 704. 1x color sensor 705
As shown in FIG. 7B, R, G, B, R, G, B
It has a dot-sequential structure such that each dot outputs a color component corresponding to each color. The feature of this method is that it can be miniaturized, and since the R, G, and B color shifts are fixed, it is possible to correct it, and high performance can be achieved.

However, the above-mentioned dichroic prism system has a disadvantage that it requires highly accurate prisms and highly accurate alignment adjustment of three sensors.
In addition, the 1x color CCD sensor system is a 1x color CC
There is a disadvantage that the D sensor is expensive and the sensor size is large.

Therefore, as a solution to this, for example, as shown in the "reading device" of Japanese Patent Laid-Open No. 2-174461, R, G, and
B line sensors read different positions on the document 3
A method using a line sensor has been proposed. It can be said that the method using the three-line sensor is advantageous in terms of easiness of adjustment and cost as compared with the dichroic prism method and the same-size color CCD sensor method.

[0007]

However, according to the method using the three-line sensor, the R, G, and B sensors store different information in the memory at the same time and synthesize the information of the same line. Since it is desired to perform color reading by doing so, there is a problem in that when the reading speed in the sub-scanning fluctuates, a positional deviation occurs and a color image cannot be read well. This misalignment is
When combining information on the same line, it appears as a color shift and affects a color image.

Factors that cause fluctuations in the reading speed during sub-scanning are periodic speed fluctuations (vibrations) due to the speed reduction mechanism (eg, gears and timing belts) between the drive pulley shaft and the scanner motor shaft. There is cogging due to a slot when the scanner motor rotates at a low speed (for example, when the scan speed is increased to a low speed).

In order to reduce the effect of cogging during low speed rotation, it is conceivable to increase the number of rotations of the scanner motor or increase the number of slots. There is a disadvantage that the motor rotation speed becomes too high at the time of reduction, and if the number of slots is increased, the motor becomes large and the cost becomes high.

The present invention has been made in view of the above, and it is possible to reduce the influence of positional deviation due to periodical speed fluctuation of the scanner on the reading of an image and to perform reading with a small color deviation. The first purpose.

Further, the present invention has been made in view of the above, and the cogging gives a positional deviation without increasing the motor rotation speed during reduction more than necessary and without increasing the size of the motor. A second object is to reduce the influence and enable reading with a small color shift.

[0012]

In order to achieve the first object of the present invention, the one-dimensional solid-state image pickup device array is made to correspond to the three primary colors, and three lines are arranged at predetermined intervals at right angles to the array direction. A monolithic light receiving element, an imaging optical system for forming an image of a subject on the light receiving element surface, a drive pulley for sub-scanning, a scanner motor, and a drive pulley and a scanner motor are connected. In the image reading apparatus including the speed reducing mechanism, the frequency generated by the speed reducing mechanism is set to a value that is twice or more the frequency that makes the interval of three lines during the sub scanning one cycle of the speed fluctuation of the sub scanning. The present invention provides the image reading device.

In order to achieve the above second object, the present invention is a monolithic structure in which one-dimensional solid-state image pickup device arrays are arranged in three lines corresponding to three primary colors and spaced at a predetermined interval at right angles to the array direction. A light receiving element, an imaging optical system for forming an image of a subject on the surface of the light receiving element, a drive pulley for sub-scanning, and a DC motor connected to the drive pulley through a direct connection or a speed reduction mechanism. In an image reading apparatus equipped with a scanner motor and a sub-scanning variable power unit, the frequency of one cycle of cogging generated by the slot of the scanner motor is defined as the interval of three lines during sub-scanning and the fluctuation of sub-scanning speed by one. It is an object of the present invention to provide an image reading device set to a value that is twice the frequency of a cycle or a value in the vicinity thereof.

[0014]

In the image reading apparatus of the present invention, the frequency generated by the deceleration mechanism is set to a value that is at least twice the frequency at which the interval of three lines during sub-scanning is one cycle of the speed fluctuation of sub-scanning. , Reduce the misalignment.

Further, in the image reading apparatus of the present invention, the frequency of one cycle of cogging generated by the slot of the scanner motor is twice the frequency of the interval of three lines during sub-scanning as one cycle of the speed variation of the sub-scanning. Or set to a value in the vicinity thereof to reduce the positional deviation.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the image reading apparatus of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a schematic view of an image reading apparatus using a 3-line sensor, and an original 102
A contact glass 101 on which a document is placed, an illumination lamp 103 for exposing a document 102, first mirrors 104 and a second mirror 10 for guiding reflected light from the document 102.
5, a third mirror 106, a lens 107, a 3-line sensor 108 that receives reflected light and photoelectrically converts it, and an analog signal from the 3-line sensor 108 is converted into a digital signal, and a scaling process is also performed. A / D change scaling processing 10
9 and a delay processing 110 for aligning three signals of R, G and B as information on the same line.

FIG. 2 shows the configuration of the 3-line sensor 108. As shown, the three-line sensor 108 includes three line sensors, a red reading sensor SR, a green reading sensor SG, and a blue reading sensor SB, which are arranged in parallel on a monolithic substrate. .. These pixels 1
The size of 08a is 7 μm × 7 μm (or 10 μm
X10 μm, 14 μm × 14 μm), and the line spacing a of the sensor is 1 of the size of the pixel 108a.
It is about 0 to 20 times (that is, about 0.1 to 0.2 mm).

Since there is a line interval between the three sensors as described above, the same position on the surface of the original 102 cannot be read at the same time. For example, when the scanner scans in the scanning direction of FIG. 1, the image formed by the lens 107 is in the scanning direction of FIG. 2 on the surface of the 3-line sensor 108.

Here, for example, at a certain time, the red reading sensor SR of the 3-line sensor 108 is in the position P ₁ , the green reading sensor SG is in the position P ₂ , and the blue reading sensor SB is in the position P _3. Suppose that the information of the position of is read, in order to obtain the three color information of R, G and B at the position of P ₁ , the scanner further scans and the sensor SG for green reading and the sensor SG for blue reading are read. Sensor SB
Reads the information of the position of P ₁ and performs delay processing 11
It suffices to combine information obtained by delaying these by 0.

FIG. 3 shows the configuration of the scanner driving device of the image reading device, which includes an illumination lamp 103 and a first mirror 104.
The first scan 111 on which is mounted and the second scanner 112 on which the second mirror 105 and the third mirror 106 are mounted are connected to the drive pulley 114 by the wire 113. The drive pulley 114 is rotated by the scanner motor 115.

From the scanner motor 115 to the drive pulley 11
4 may be directly connected from the scanner motor 115, but in many cases, for example, as shown in FIG.
A speed reduction mechanism as shown in (a) and (b) is used. In this embodiment, the speed reducing mechanism shown in FIG.
A large gear 114a attached to the drive pulley 114,
Small gear 115a attached to the scanner motor 115
The speed reduction mechanism is formed by meshing with and. FIG. 2B shows another example of the speed reducing mechanism. By connecting a large pulley 114b attached to the drive pulley 114 and a small pulley 115b attached to the scanner motor 115 by using a timing belt 117,
It forms a speed reduction mechanism. Reference numeral 116 represents an encoder.

In such a reduction mechanism, the gear 11
4a and gear 115a teeth mesh, and pulley 114b
The vibration of the pulley 115b and the timing belt 117 due to the meshing of the teeth causes the drive pulley 114 to rotate, which causes the scanners 111 and 112 to have periodic speed fluctuations due to the meshing of the teeth.

Further, at the time of enlargement (when the motor rotates at a low speed), the scanners 111, 1 are irrespective of the presence or absence of a reduction mechanism.
No. 12 causes periodic speed fluctuation due to the influence of motor cogging.

Next, the positional deviation (color deviation) caused by the periodic speed fluctuations of the scanners 111 and 112 will be described. Assuming that the speed v (t) of the first scanner 111 is represented by the formula 1,

[0025]

[Equation 1]

In the configuration of FIG. 1, the sensor SG reads the point X on the surface of the original 102 read by the sensor SR at the time T, and
T + Δt, and the reading time of the sensor SB is T + 2 × Δ
t. First scanner 11 moved to read point X
When the distances of 1 are X _R , X _G , and X _B , respectively, they can be expressed by the following equations (1) to (2).

[0027]

[Equation 2]

Therefore, the positional deviation (color deviation) when the X point is read is expressed by the equations (3) to (3).

[0029]

[Equation 3]

FIG. 5 shows the results obtained by the equations (3) to (3). Here, the frequency f ₀ at which | X _R −X _B | max becomes 0 is the frequency at which the interval of three lines on the document surface and one cycle of the speed fluctuation of the first scanner 111 match. f ₁ is 2 of f _0
2 times the frequency f ₂ is 3 times the frequency f ₀ . For example, the read density is 16 dot / mm, the interval of 3 lines is 24 lines, and the linear velocity of the first scanner 111 at the same magnification is 180 mm.
/ S, each frequency is obtained by the equation (4).

[0031]

[Equation 4]

Therefore, f ₀ is 120 Hz and f ₁ is 240
Hz and f ₂ are 360 Hz. For example, in FIG. 4A, the effective diameter of the drive pulley 114 is φ30, the large gear 114a is Z ₁ = 60, and the small gear 115a is Z ₂ =.
Assuming that the frequency is 10, the frequency generated by the tooth contact when the linear velocity is 180 mm / s is 11
It becomes 4.6 Hz, which is in the vicinity of f ₀ in FIG.

[0033]

[Equation 5]

Therefore, in order to keep the speed reduction ratio (Z ₁ : Z ₂ ) constant and the frequency of vibration caused by tooth contact to be in the vicinity of f ₁ , it is sufficient to set Z ₁ = 126 and Z ₂ = 21. The frequency at this time is 240.61 Hz, as shown in Equation 6.

[0035]

[Equation 6]

Further, for example, in FIG. 4A, if the effective diameter of the drive pulley 114 is φ30, the reduction ratio is 1/6, and the number of slots is 10, then cogging occurs when the linear velocity is 180 mm / s. The generated frequency is 114.6 Hz at the same magnification, as shown in Expression 7, which is close to f ₀ in FIG.

[0037]

[Equation 7]

Therefore, with the reduction ratio (1/6) kept constant,
The number of slots may be set to 21 in order to make the frequency fluctuation frequency due to cogging close to f ₁ . The frequency at this time is 240.6 Hz as shown in Equation 8.

[0039]

[Equation 8]

As described above, in the present embodiment, the positional deviation (color misregistration) in the sub-scanning direction caused by the periodic speed fluctuation of the scanner caused by the speed reduction mechanism connecting the drive pulley for the sub-scanning and the scanner motor. And a color image can be read well.

Further, at the time of magnifying reading, the positional deviation (color deviation) in the sub-scanning direction caused by the periodical speed fluctuation of scanning due to the cogging by the slot of the scanner motor can be reduced, and the color image can be read well. .. Further, it is possible to reduce the influence of the cogging on the positional deviation and to perform the reading with a small color misregistration without increasing the motor rotation speed at the time of reduction unnecessarily and without increasing the size of the motor.

[0042]

As described above, the image reading apparatus of the present invention is a monolithic one-dimensional solid-state imaging device array in which three lines are arranged corresponding to the three primary colors and arranged at a predetermined interval at right angles to the array direction. A light receiving element, an imaging optical system for forming an image of a subject on the surface of the light receiving element, a drive pulley for sub-scanning, a scanner motor, and a speed reduction mechanism connecting the drive pulley and the scanner motor. In the provided image reading apparatus, the frequency generated by the deceleration mechanism is set to the interval of 3 lines during the sub-scanning as 1 of the fluctuation in the sub-scanning speed.
Since the frequency is set to be twice the frequency or a value in the vicinity thereof, the influence of the positional deviation due to the periodical speed fluctuation of the scanner on the reading of the image can be reduced, and the reading with the small color deviation can be performed.

Further, the image reading apparatus of the present invention includes a monolithic light-receiving element in which a one-dimensional solid-state image pickup element array is arranged in three lines corresponding to three primary colors at predetermined intervals at right angles to the array direction, and a subject. Optical system for forming an image of the image on the light receiving element surface, a drive pulley for sub-scanning, a scanner motor that is a DC motor connected to the drive pulley through a direct connection or a speed reduction mechanism, In an image reading apparatus provided with a scanning variable power unit, a frequency of one cycle of cogging generated by a slot of a scanner motor is set to a frequency of two intervals of three lines during sub scanning as one cycle of speed variation of the sub scanning. Since the value is set to double or a value in the vicinity thereof, the cogging will not cause a positional shift without increasing the motor rotation speed during reduction more than necessary and without increasing the size of the motor. The effect was small, it is possible to perform a small read color shift.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic view of an image reading apparatus using a 3-line sensor of an embodiment.

FIG. 2 is an explanatory diagram showing a configuration of a three-line sensor according to an embodiment.

FIG. 3 is an explanatory diagram showing a configuration of a scanner driving device according to an embodiment.

FIG. 4A is an explanatory diagram showing a configuration of a reduction mechanism of the embodiment, and FIG. 4B is an explanatory diagram showing a configuration of another example of the reduction mechanism.

FIG. 5 is an explanatory diagram showing a relationship between a color misregistration amount on a document surface and a frequency of scanner speed fluctuation.

FIG. 6 is an explanatory diagram showing a configuration of a dichroic prism type image reading device.

FIG. 7 is an explanatory diagram showing a configuration of an image reading device of a 1 × color sensor system.

[Explanation of symbols]

108 3-line sensor 118a
Pixel 114 Drive pulley 114a
Gear 114b Pulley 115 Shana Motor 115a Gear 115b
Pulley 117 Timing belt SR Red reading sensor SG Green reading sensor SB Blue reading sensor

Claims (2)

[Claims] 1. A monolithic light-receiving element in which a one-dimensional solid-state image pickup element array is arranged in three lines corresponding to three primary colors and arranged at predetermined intervals at right angles to the array direction, and an image of a subject is formed on the light-receiving element surface. In an image reading apparatus including an image forming optical system for forming an image, a drive pulley for sub-scanning, a scanner motor, and a speed reduction mechanism connecting the drive pulley and the scanner motor, a vibration generated by the speed reduction mechanism. The image reading apparatus is characterized in that the number is set to a value that is twice or more a frequency that makes an interval of three lines during sub-scanning one cycle of a speed fluctuation of the sub-scanning or a value in the vicinity thereof. 2. A monolithic light-receiving element in which a one-dimensional solid-state image pickup element array is arranged in three lines corresponding to the three primary colors and arranged at a predetermined interval at right angles to the array direction, and an image of a subject is formed on the light-receiving element surface. An image forming optical system for forming an image, a drive pulley for sub-scanning, a scanner motor which is a DC motor connected to the drive pulley through a direct connection or a speed reduction mechanism, and a sub-scanning magnification changing unit. In the image reading apparatus, the frequency of one cycle of cogging generated by the slot of the scanner motor is set to 2 times the frequency of the interval of three lines during sub-scanning as one cycle of speed variation of the sub-scanning.
An image reading apparatus, wherein the value is set to twice or a value in the vicinity thereof.