JP2004135214A - Scanner apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure a sampling interval as long as possible within the limited space by solving a problem that the interval of sampling positions is short in the first half and becomes longer later since a read timing is a fixed time interval in the case of reading before a mobile optical system is sufficiently accelerated when performing sampling of shading correction in a conventional scanner apparatus, and that a resulting value becomes considerably lower than right white shading data when there is dust or flaw over two sampling positions at a read position of the first half on a shading correction plate. <P>SOLUTION: By changing the interval of sampling timings in accordance with the moving speed of the mobile optical system, sampling is performed in a distance of the approximately equal interval, and the dust or flaw is not spread over two samplings so much. As a result, even when the dust or the flaw is read, the value approximate to the accurate white shading data is obtained. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Industrial applications]
The present invention relates to a scanner device in an image forming apparatus such as a digital copying machine and a multifunction peripheral, and particularly when sampling and reading for shading correction, dust (dirt), dirt, and flaws are found at a reading position of a shading correction plate. The present invention relates to a scanner device that can perform appropriate sampling even when there is an error.
[Prior art]
[0002]
An image reading apparatus provided in a digital copying machine or the like includes an image reading sensor that reads reflected light from a document when a document is scanned by a light source, and is configured to generate an image signal according to an output signal from the image reading sensor. ing. Generally, the image reading sensor is configured by arranging a plurality of CCD linear image sensors or the like in which a large number of CCD elements are arranged one-dimensionally on a line, and an output signal from each CCD element is A / A. The data is input to the image processing unit via the D converter.
[0003]
By the way, in this type of image reading apparatus, since a variation in characteristics such as light receiving sensitivity and dark voltage of each CCD element, or a variation in light emission amount of a light source, a substantial variation in sensitivity occurs between the CCD elements, Shading correction is generally performed to correct this.
[0004]
The procedure is as follows. First, a digital signal (output signal from each CCD element; hereinafter, referred to as black shading data) obtained by driving the image reading sensor in a dark state in advance and a reference white (shading correction plate) using an exposure lamp having a predetermined light emission amount. While irradiating light, the lamp and the mirror are moved in the sub-scanning direction while sampling a predetermined number of times (for example, 5 times) at fixed time intervals. An output signal from the CCD element; hereinafter, referred to as white shading data) is stored in a black shading memory and a white shading memory, respectively, corresponding to each CCD element. Here, when creating the white shading data, the reference white reading position is changed and sampling is performed a plurality of times and the average is adopted when there is dust (dirt), dirt, flaws, etc. on the shading correction plate. This is for absorbing the noise.
[0005]
Next, the level difference between the white shading data (upper limit level) and the black shading data (lower limit level) for each CCD element is obtained and its maximum value is selected, and this maximum level difference is determined by the level difference obtained for each CCD element. Is set as a shading correction coefficient for each CCD element and stored. Then, at the time of actual scanning of the original, the variation in sensitivity is smoothed by multiplying the output signal of each CCD element by the above-mentioned shading correction coefficient, and an image signal corresponding to the corrected signal is created.
[0006]
When the variation of the black shading data for each CCD is sufficiently small, the shading correction may be performed by taking in only the white shading data.
[0007]
[Problems to be solved by the invention]
As described above, while irradiating light to the reference white (shading correction plate) with the exposure lamp having the predetermined light emission amount, the moving optical unit including the lamp and the mirror is moved in the sub-scanning direction and at a predetermined time interval. When sampling the number of times (for example, five times), if the moving optical unit moves at a constant speed, sampling is performed at equal distance intervals. However, since the shading correction plate is provided at a position other than the document reading position and is read during acceleration immediately after the moving optical unit starts moving, the interval of the initial distance of reading is short, and the interval of the distance is short as it is later. Becomes longer. FIG. 4 shows this state.
[0008]
FIG. 4A shows that a moving optical unit including a lamp and a mirror performs sampling while accelerating. FIG. 4B shows the reading position of the shading correction plate 7 of one CCD element, and the distance between the reading positions is longer in the second half where acceleration is performed than in the first half where the speed is slow. At this time, as shown in the figure, if there is dust or scratches on the shading correction plate 7, since the distance between the reading position at S1 and the reading position at S2 is short, large dust or scratches are present. In such a case, dust or scratches may be read across the reading position at S1 and the reading position at S2. As a result, as shown in FIG. 4 (C), the reading voltage of the CCD element was such that the reading voltage at S1 and S2 was low, and the reading voltage at S3 to S5 was a value obtained by reading a normal white board. Since the average value of the read voltages in S1 to S5 is smaller than the normal value, the shading correction of the CCD element is not correctly performed. In order to solve such a problem, the reading distance may be set to be sufficiently long. However, in that case, the shading correction plate 7 needs to have a long distance in the sub-scanning direction, resulting in waste. It is also conceivable to keep the moving speed constant by taking a sufficient run, but it requires extra space for the run and sampling time. An object of the present invention is to solve such a problem and to increase the sampling interval as much as possible in a limited space.
[0009]
[Means to solve the problem]
In order to solve the above problem, a first invention of the present application discloses a first reading method for reading a document placed on a contact glass by moving a moving optical unit including a lamp and a plurality of mirrors in a sub-scanning direction. In a scanner device having a second reading method in which the moving optical unit is stopped at a predetermined sheet-through document reading position and a document is fed by a document feeder to read the document, the moving optical unit is moved in the sub-scanning direction. A driving unit for performing driving for moving, a shading correction plate provided at a position other than the original reading position by the above two methods, and a moving optical unit while moving the moving optical unit when performing sampling reading for shading correction. Reads the shading correction plate at substantially the same interval in the main scanning direction Using scanner apparatus characterized by having a sampling clock signal generating means for generating a sampling clock signal for.
[0010]
The second invention of the present application uses the scanner device according to the first invention, wherein the sampling clock signal generating means generates a sampling clock signal based on a clock signal for driving the driving means.
[0011]
A third invention of this application uses the scanner device according to the first invention, wherein the sampling clock signal generating means generates a sampling clock signal based on an encoder signal from the driving means.
[0012]
[Action]
According to the first aspect of the present invention, the distance between the sampling positions can be made substantially the same by providing a sampling clock with a long interval in the first half of the sampling and a sampling clock with a short interval in the second half.
[0013]
According to the second invention of this application, if the sampling clock is used by dividing the driving clock applied to the motor for driving the moving optical unit, the distance between the sampling positions can be made exactly the same.
[0014]
In the third invention of the present application, the sampling clock is used by dividing a signal for reading and feeding back the rotation, such as an encoder from a motor for driving the moving optical unit, and so on. Can be the same distance.
[0015]
【Example】
A scanner device employing the present invention will be described with reference to the schematic diagram of FIG. In FIG. 1, a scanner device 1 includes a document tray 2, a document discharge tray 3, a document transport path 4, a platen glass 5, a sheet-through reading contact glass 6, a shading correction plate 7, a movable optical unit 8, and an optical unit (CCD unit). 9 and the like.
[0016]
When reading a document, in the case of a single document, the document placed on the platen glass 5 is moved by the moving optical unit 8 in the sub-scanning direction while the light reflected by the lamp is reflected by a plurality of mirrors. The light is guided to the optical unit 9 for reading. In the case of sheet-through reading, the moving optical unit 8 is stopped at the sheet-through document reading position (below the sheet-through reading contact glass 6), and the documents stacked on the document tray 2 are sequentially transferred one by one to the document transport path 4. While the document is being conveyed, the document is read at the sheet through document reading position.
[0017]
FIG. 2 is a block diagram around the optical unit 9 of the scanner device employing the present invention and the movable optical unit. The case of the first invention will be described with reference to FIG. Here, the scanner control unit 10 is a sampling clock generating unit, which reads the shading correction plate 7 a plurality of times and generates a timing signal (sampling clock CLK2 in the figure) when sampling is performed. This signal is a signal having an interval at first and gradually decreasing the interval, and the distance in the sub-scanning direction at each sampling position can be made substantially the same. At this time, data prepared in advance may be used based on how the motor is accelerated.
[0018]
The case of the first invention will be described with reference to FIG. If the motor that drives the moving optical system 8 is a stepping motor, the frequency of the clock signal is gradually increased until a predetermined rotation is performed so as to prevent loss of synchronism. When used as a signal of the read timing of each CCD element at the time of correction, the intervals between the read positions can be accurately made the same. At this time, an initial clock (motor drive clock CLK1 in the figure) is supplied from the scanner control unit 10 to the motor driver 83, and a timing signal (sampling clock CLK3 in the figure) for performing sampling generated based on this signal is supplied to the CCD driver. Give to 91. Here, the signal is given from the scanner control unit 10 to the motor driver 83 and the CCD driver 91, but a sampling clock may be given from the motor driver 83 to the CCD driver 91.
[0019]
The case of the third invention will be described with reference to FIG. Since a feedback signal (FG; frequency transmission signal) from an encoder for driving the moving optical system 8 from the encoder almost accurately represents the number of rotations of the motor, the CCD element for shading correction by dividing this signal is used. When used as a signal of the read timing, the intervals between the read positions can be accurately set to the same distance. At this time, the scanner controller 10 receives the FG from the motor via the motor driver, and supplies the CCD driver 91 with a timing signal (sampling clock CLK4 in the drawing) for performing sampling generated based on the FG. Further, as a modification, a configuration in which FG is provided from the motor driver 83 to the CCD driver 91 may be employed.
[0020]
The situation when shading correction is performed using the first to third aspects of the present invention will be described with reference to FIG. FIG. 3A shows a state where the moving optical unit 8 composed of a lamp and a mirror performs sampling while accelerating. The horizontal axis represents time, and the vertical axis represents moving speed. Here, the sampling timing is gradually advanced with the acceleration of the moving optical unit 8. As a result, as shown in FIG. 3B, the distance between the timings of the reading position of the shading correction plate 7 becomes substantially the same. Here, similarly to the related art, the shading correction plate 7 is read with dust or scratches. Here, since the distance between S1 and S2 is longer than that in the related art, it is less likely that dust or scratches are relatively read between S1 and S2. As a result, as shown in FIG. 3C, the reading voltage of the CCD element is low only in S1 and is a value obtained by reading a normal white board in S4 to S5, and the average value of S1 to S5 is a normal value. Although the value is smaller than that, the result is relatively easily absorbed, and the shading correction is correctly performed.
[0021]
As described above, for each CCD element, the average value of the data obtained by reading the shading correction plate 7 is stored in the memory as white shading data. Here, averaging is performed five times, but more than two times, more accurate data can be obtained. Although the average value of five times is used, an abnormal value may be determined and discarded.
[0022]
【The invention's effect】
According to the first aspect of the present invention, by providing a sampling clock with a long interval in the first half of the sampling and a sampling clock with a short interval in the second half, the distance between the sampling positions can be made substantially the same.
[0023]
According to the second aspect of the present invention, if the sampling clock is used by dividing the driving clock applied to the motor for driving the movable optical unit, the distance between the sampling positions can be made exactly the same. .
[0024]
According to the third aspect of the present invention, since the sampling clock is used by dividing a signal for reading the rotation and feeding back the rotation, such as an encoder from a motor for driving the moving optical unit, the sampling clock is accurately used. The distance between the positions can be the same [Brief description of the drawings]
FIG. 1 is a schematic diagram of a scanner device employing the present invention.
FIG. 2 is a block diagram for explaining driving of a moving optical system of a scanner device employing the present invention and control of reading of a CCD.
FIGS. 3A and 3B are diagrams for explaining (A) a reading timing, (B) a reading position, and (C) a reading result when performing shading correction in a scanner device employing the present invention.
FIG. 4 is a diagram for explaining (A) a reading timing, (B) a reading position, and (C) a reading result when performing shading correction in a scanner device employing a conventional technique.
[Explanation of symbols]
1: Scanner device 2: Document tray 3: Discharge tray 4: Document transport path 5: Platen glass 6: Sheet-through reading contact glass 7: Shading correction plate 8: Moving optical system 9: Optical unit

Claims (3)

A first reading method for reading a document placed on a contact glass by moving a moving optical unit including a lamp and a plurality of mirrors in a sub-scanning direction, and stopping the moving optical unit at a predetermined sheet-through document reading position. In a scanner device having a second reading method in which a document is fed by a document feeder and the document is read,
A driving unit for driving the moving optical unit to move in the sub-scanning direction, a shading correction plate provided at a position other than the document reading position by the above two methods, and when performing sampling reading for shading correction, A scanning clock signal generating means for generating a sampling clock signal for reading the shading correction plate at substantially equal intervals in the main scanning direction while moving the moving optical unit. 2. The scanner device according to claim 1, wherein the sampling clock signal generating unit generates a sampling clock signal based on a clock signal for driving the driving unit. 2. The scanner device according to claim 1, wherein the sampling clock signal generating unit generates a sampling clock signal based on an encoder signal from the driving unit.

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