JP3229343B2 - Document reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color original reading apparatus using a plurality of line sensors, for example, as a part of a digitally controlled color copier or a color facsimile transmitter, or as a single unit.

[0002]

2. Description of the Related Art Conventionally, there has been known an apparatus which uses a line sensor for reading a color original, moves a moving body in a direction perpendicular to the line sensor, and scans the entire original. For driving the moving body, a motor is used as an actuator, and power is transmitted by a gear or a timing pulley to drive a pulley around which a wire to which the moving body is attached is wound.

As the line sensor, three line sensors such as three CCDs corresponding to respective color filters of red (R), green (G) and blue (B) are used, and a color image reading system is configured as shown in FIG. You. The reading position on the document surface corresponding to the line sensor of each color filter is different, and in order to obtain color image data of the same line, perform correction to shift each color data by the difference. I have.
Now, assuming that the distance on the original surface between the first and second line sensors on the original surface with respect to the sub-scanning direction of the original reading device is L1, the first or second pixel in the sub-scanning direction is included in L1. The data acquired by the second line sensor is shifted, and the same operation is performed on the first and third lines to obtain color image data.

[0004]

However, if there is a processing error or the like in the reduction gear train or the timing pulley connected to the drive motor, the speed will fluctuate at the time of scanning the original. Or, vibration is generated, which affects the lens and the line sensor.

In such a case, the read position of each color component read by the document reading apparatus is shifted by several tens of μm, and data formed from these components reproduces an inaccurate color image. Would.

One of the image processing methods for processing the read color image is to recognize black characters and lines. There is a risk that what was a line may be mistakenly recognized as a different one.

[0007] As the resolution in the vertical direction with respect to the line sensor is improved, the inaccuracy of the color image data due to the unevenness of the scanning speed becomes more remarkable.
It is becoming a big problem.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a document in which the displacement of each line sensor does not occur even when speed unevenness occurs in a period in which gears and timing pulleys mesh. A reading device is provided.

[0009]

In the present invention in order to solve the above problems SUMMARY OF THE INVENTION, move along the mounting surface of the document to read the color image of originals using a plurality of line sensors
A moving body that moves, and the moving body is driven by a driving motor.
In the document reading apparatus to which a driving force is transmitted via the transmission path, the data read shift time based on the distance between the respective line sensors, substantially mating cycle gear or / and the timing pulley constituting the drive transmission path The number of teeth and the reduction ratio of the gear and / or the timing pulley are set so as to be an integral multiple.

[0010]

Generally, the frequency of the speed unevenness generated in the drive transmission path of the document reading apparatus is particularly generated in a period in which the gears and the timing pulley engage.

By the way, in the present invention having the above configuration,
Since the data reading shift time based on the distance between each line sensor of the plurality of line sensors is an integral multiple of the engagement period of the gears and timing pulleys of the drive transmission path, the color image data read by the plurality of line sensors is , Less susceptible to reading position shift,
Accurate color data can be obtained.

[0012]

An embodiment of the present invention will be described with reference to the drawings.
FIG. 2 is a schematic diagram of a color document reading apparatus to which the present invention is applied. In FIG. 2, reference numeral 1 denotes a document scanner motor, a timing belt 14, and a timing pulley 1 as a pulley thereof.
The drive transmission path D of the speed reduction system using the components 2 and 13 is configured.
The wire pulley 4 on the driving side, which is fixed by the shaft 11 and around which the wire 5 is wound, is driven. The moving body (A) 2 is directly attached to the wire 5, and the moving body (B) 3 is attached to a pulley of a moving pulley type. One end of the wire 5 wound on the pulley is spring-connected via a pulley 15. 16 fixed. Then, the moving body (A) 2 and the moving body (B) 3
Is moved while maintaining the relation of the movement amount of 2: 1. Therefore, the lamp 9, the original 19 on the original table 6, the mirror
0, in the optical path through the lens 7,
The distance of the three lines B to the line sensor 8 is kept constant.

The details of the first embodiment of the present invention having the above configuration will be described with reference to FIG. FIG. 1A shows the relationship between the positional shift amount Δx generated when the apparatus reads a document and time. Here, the positional deviation amount indicates an amount of deviation from a normal position where scanning is performed at a constant speed due to speed fluctuation of the moving body during scanning. t1 and t2 indicate the data read shift time between RG and RB, respectively. △ x1 and △ x2 indicate deviations of the reading positions of the RG and RB line sensors, respectively.

Here, the distance between the R and G line sensors on the document surface is L1, the distance between R and B is L2, and the scanning speed V is:
The number of teeth of the timing pulley is Z1 (drive side), Z2 (driven side), and the number of revolutions per second of the timing pulleys 12 and 13 is 1
And r2, respectively .

[0015]

(Equation 1) Here, t1 becomes Equation 2 and t2 becomes Equation 3.

[0016]

(Equation 2)

[0017]

(Equation 3) As specific examples, L1 = 1 mm, L2 = 2 mm, V = 100 mm / se
Assuming that c, if Equation 5 is determined to satisfy Equation 5, the deviation of the reading position between the line sensors is significantly smaller than the case shown in FIG. 1B in which the present invention is not implemented.

[0018]

(Equation 4)

[0019]

(Equation 5) FIG. 4 shows a second embodiment of the present invention, in which reduction gears 17 and 18 and a timing belt 14 are used in the transmission path from the original scanner motor 1 to the driving side wire pulley 4. The other configuration is the same as that of the first embodiment, and is similar to FIGS.

The distance between the line sensors on the original
L1 between RB, L2 between RB, scanning speed V, number of teeth of gear 17 is Z1, number of revolutions per second is r1, driving pulley 1
If the number of teeth of 2 is Z3 and the number of revolutions per second is r3, then Equation 6 is satisfied
By setting the number of teeth of the gear and the timing pulley and the reduction ratio as described above , the reading position deviation between the line sensors, which was 40 μm at the maximum, can be suppressed to 10 μm or less.

[0021]

(Equation 6) In the first and second embodiments, the reduction optical system has been described. However, an optical system of the same magnification may be used, and if a plurality of line sensors are used, RGB3 is used as in the above-described second embodiment.
The present invention is not limited to a line sensor.

[0022]

As described above, in a color original reading apparatus using a plurality of line sensors, each having a different color filter attached thereto, a data reading shift time based on the distance between the line sensors. However, by setting the number of gears and timing pulley teeth and the reduction ratio so that it is an integral multiple of the gear transmission timing gear and timing pulley engagement period, speed unevenness occurs at the gear and timing pulley engagement period. However, the displacement of each line sensor is the same, and a phenomenon that the data reading position changes between the line sensors can be avoided.

[Brief description of the drawings]

FIG. 1A is a graph of experimental data showing a relationship between a reading interval and a position shift when the present invention is implemented, and FIG.
FIG. 5 is a graph of experimental data showing a relationship between a reading interval and a position shift when the present invention is not performed.

FIG. 2 is a schematic configuration diagram of a document reading apparatus according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram showing an optical path of the device.

FIG. 4 is a schematic configuration diagram of a document reading apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

 8 Line sensor D Drive transmission path 12, 13 Timing pulley 17, 18 Gear

Continuation of front page (56) References JP-A-4-315363 (JP, A) JP-A-3-27665 (JP, A) JP-A-1-12670 (JP, A) JP-A-63-76567 (JP) JP-A-62-144466 (JP, A) JP-A-59-178865 (JP, A) JP-A-58-186254 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB (Name) H04N 1/04-1/207

Claims (1)

(57) [Claims] Color originals using 1. A plurality of line sensors
A transfer that moves along the document loading surface to read an image
A moving body, wherein the moving body has a drive transmission path from a drive motor;
In the document reading apparatus to which a driving force is transmitted through the data read shift time based on the distance between the line sensors, approximately an integral multiple of the meshing cycle gear or / and the timing pulley constituting the drive transmission path A document reading apparatus, wherein the number of teeth and the speed reduction ratio of the gear and / or the timing pulley are set so that