JPH07184013A - Image reading method - Google Patents

Abstract

PURPOSE:To surely prevent the occurrence of color irregularity due to the variance in characteristic of a light source or the like by providing the step where it is discriminated whether the difference between white reference data stored before and that stored at present is within an allowable range or not and reading the white reference value after stabilization of the light source. CONSTITUTION:When a read start button is depressed, a fluorescent lamp 56 of a light source unit 55 for reflection is temporarily extinguished, and black data is read after a prescribed time and is stored as black reference data in a memory. Next, the fluorescent lamp 56 is lit, and the first read of white data is performed after a prescribed time, and this data is stored as white reference data in the memory. White reference data is read and stored repeatedly at intervals of the prescribed time in this manner, and it is discriminated whether difference data between data stored before and data stored at present is within the allowable range or not at each time of this read and storage. If it is within the allowable range, it is judged that the light source is stabilized, and data stored at present is taken as white reference data to execute the next step.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading method for reading and storing black reference data and white reference data for shading correction prior to reading an original.

[0002]

2. Description of the Related Art FIG. 4 is an external perspective view showing an example of a conventional image reading apparatus (for both a reflective original and a transparent original capable of reading both a reflective original and a transparent original).
A main body part having a main part as shown in FIG. 5 is housed therein. In FIG. 4, 2 is a document pressing cover,
Cover body 2A, transmitted light source unit storage 2B, and hem 2
It is made up of a unitary body in which C and C are sequentially arranged and has a size that covers the entire upper surface of the casing 1. The transmissive light source unit storage section 2B of the document holding cover 2 is a semi-cylindrical body with both ends closed, and defines a transmissive light source unit storage space 2E inside, and a boundary section with the cover body 2A and a boundary section with the skirt section 2C. Is the hinge part 2D, and the transmission light source unit storage part 2B
Can be bent upward to a certain angle with respect to the skirt portion 2C, and the cover body 2A can be bent upward to a certain angle with respect to the transmissive light source unit storage portion 2B. Reference numeral 3 is a document table frame portion formed on the upper surface of the casing 1, and 4 is a transparent glass table which is a document table.

In FIG. 5, A is a transparent original, 5 is a diffusion plate, 20 is a transmissive light source unit, and 40 is a reading unit. The reading unit 40 has a frame 47, and a line CCD color sensor 48 is provided on the lower surface of the frame 47.
A plate-shaped sensor holder 49 on which is mounted is attached by a screw 50, and a control board 53 is supported below the sensor holder 49 via spacers 51 by screws 50 and 52. The frame 47 has a sensor holder 49 on its front side.
A raised portion 47A defining a space between the raised portion 47A and a cylindrical portion 47B that opens at the lower end and extends upward.
The converging rod lens array 54 is attached to the cylindrical portion 47B. The CCD sensor (line sensor) 48 is arranged directly below the converging rod lens array 54. Reference numeral 55 denotes a light source unit for reflection, which has a fluorescent lamp 56, is located behind the cylindrical portion 47B of the frame 47, and is supported by the carriage 43. Reference numeral 57 denotes a guide roll provided on the opposite side of the slide shaft 31 of the carriage 43, and engages with the back surface of the glass table 5 to roll. Reference numeral 100 is a control device of the image reading device.

The reading unit 40 is reciprocally driven by a driving mechanism (not shown) with the slide shaft 31 as a guide. When reading in the transmissive mode, the transmissive light source unit 20 is used.
Are integrally connected to the reading unit 40. After completing this preparation, the transparent original A is placed on the glass table 4 and the diffusion plate 5
On the original A, press a reading start button (not shown) to supply illumination power to the transmissive light source unit 20,
The drive mechanism (not shown) is driven. As a result, the reading unit 40 moves from a home position (not shown) in the arrow direction. Since the transmissive light source unit 20 is connected to the reading unit 40, the reading unit 40
Move together with.

The fluorescent lamp 22 of the transmissive light source unit 20 passes through the transparent original A and the glass table 4 as shown by the broken line in the figure, and this transmitted light passes through the converging rod lens 54 and is formed on the CCD sensor 48. Image.

When reading in the reflection mode, the transmission light source unit 20 and the reading unit 40 are uncoupled, a reflection document (not shown) is placed on the glass table 4, and a document holding cover (not shown) is used as a reflection document instead of the diffusion plate 5. Cover
Press the scanning start button.

FIG. 6 shows the flow of the shading correction data reading operation after the reading start button is pressed.

[0008]

When the reading start button is pressed, the CPU in the control device 100 causes the CPU in FIG.
As shown in FIG.
Is temporarily turned off (step 1), a predetermined time T1 has elapsed (step 2), the black reference value (black original) is read, and the read black reference value is stored in the memory as black reference data. (Step 3). Then fluorescent light 5
6 is lit for a predetermined time T2 (steps 4 and 5), and after the lapse of the predetermined time T2, the white reference value (white original) is read and stored in the memory (step 6).

After the steps 1 to 6 are finished, the reading of the original is started. At the time of reading the original, shading (color shading) is corrected using the black reference value and the white reference value.

By the way, it takes time for the fluorescent lamp to stabilize its light quantity, and it stabilizes after changing the light quantity as shown in FIG. 7 (1) shows an unstable state immediately after lighting the fluorescent lamp, FIG. 7 (2) shows an unstable state after lighting the fluorescent lamp, and FIG. 7 (3) shows a stable state of the fluorescent lamp. Each of the white reference values shown in FIG. 7 changes as time passes and changes as shown in (4) of FIG. 7.

When the shading correction is performed on the image data of the original (the original of the same color on the whole surface) read after the light quantity of the fluorescent lamp becomes stable by using the reference value read when the light quantity of the fluorescent lamp is unstable, It becomes like (5) of FIG.

In order to improve the image reading quality, it is sufficient to read the white reference value after the light quantity of the fluorescent lamp is stabilized, but it takes time until the light quantity of the fluorescent lamp becomes stable. In order to shorten the length, for example, as shown in FIG.
A heater H is provided on the fluorescent lamp 56 as shown in FIG.

However, since the time until the light quantity stabilizes varies depending on each fluorescent lamp, there is a problem that the color unevenness of the image cannot be prevented only by providing the heater.

The present invention has been made in order to solve this problem. The white reference value is always read after the light source is stable, and the occurrence of color unevenness due to variations in the characteristics of the light source or the like. An object of the present invention is to provide an image reading method that can be surely prevented.

[0015]

In order to achieve the above object, the present invention provides an image reading method according to claim 1, which reads and stores black reference data and white reference data for shading correction prior to reading an original. Then, in the image reading method including the step of reading and storing the white reference data after turning on the reading light source and waiting for a predetermined period of time required for stabilization of the light source, after performing the steps, The step of reading and storing the white reference data is repeated every predetermined time, and each time, the step of determining whether the difference data between the previously stored data and the data stored this time is within the allowable range, If it is within the range, it is determined that the light source is stable, and the data stored this time is used as the white reference data. And configured to perform the following steps.

According to a second aspect of the present invention, the next step is executed with the most recently stored data as white reference data, provided that the previous difference data and the current difference data are both within the allowable range.

[0017]

According to the present invention, the step of reading and storing the white reference data is repeated every predetermined time, and each time it is determined whether or not the difference data between the previously stored data and the currently stored data is within the allowable range. , If it is within the allowable range, it is determined that the light source is stable, the data stored this time is used as the white reference data, and the next step is executed. Therefore, by setting the allowable range appropriately, The white reference data can always be obtained with the light source stable.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an operation flow chart showing an embodiment of the present invention. In the present embodiment, when the reading start button is pressed, the control device 100 executes this operation flow.

When the reading start button is pressed, if the fluorescent lamp 56 of the reflection light source unit 55 is on, the fluorescent lamp 56 is once turned off and waits for a predetermined time T1 to pass (step 2). Then, the black data is read and the read black data is stored in the memory as black reference data (step 3). In the next step 4, the fluorescent lamp 56 is turned on (step 4). When the predetermined time T3 (which can be shorter than T2) elapses (step 5), the white data is read for the first time, and the read white data is stored in the memory as the white reference data D1 ( Step 6). After that, when the predetermined time T3 has elapsed (step 9), the second reading of the white data is performed, and the read white data is stored in the memory as the white reference data D2 (step 10). Further, after the elapse of the predetermined time T3 (step 7), the white data is read for the third time, and the read white data is stored in the memory as the white reference data D3 (repeat steps 5 to 6). . The difference data D1 to D2 and D2 to D3 of the three white reference data stored in the memory are taken, and it is determined whether or not the difference data is within the preset allowable range. If both difference data are less than a predetermined value, the third white reference data D
With 3 as the true white reference data, reading of the original is started and shading correction is performed on the read data.

If the difference data D1 to D2 are not within the above allowable range, the white reference data D4 is read for the fourth time, and if the difference data D3 to D4 are within the preset allowable range, the fourth time is read. With the white reference data D4 as true white reference data, reading of the original is started, and shading correction is performed on the read data.

That is, in the present embodiment, as shown in FIG. 2, the sampling is repeated at regular intervals, and the next step is performed only when the previous difference data and the current difference data are continuously within the preset allowable range. The reading of the original document is started, and the white reference data is read and stored in the memory repeatedly until the difference data of the previous time and the difference data of this time are continuously within the preset allowable range.

In the present embodiment, the condition that the difference data is within the previously set allowable range twice consecutively is that the difference data for one time is within the above allowable range. This is because, for example, it is judged as OK even in the unstable region as shown in FIG. Of course, the condition may be that the difference data is within the preset allowable range three times in a row.

[0024]

As described above, according to the present invention, the step of reading and storing the white reference data is repeated every predetermined time, and each time the difference data between the previously stored data and the currently stored data is within the allowable range. If it is within the allowable range, it is determined that the light source is stable, and the data stored this time is used as the white reference data,
By executing the next step, by setting the above allowable range appropriately, you can always obtain white reference data with the light source stable, and without changing the hardware, just change the software a little. It is possible to reliably prevent the occurrence of color unevenness due to variations in the characteristics of the light source and the like.

[Brief description of drawings]

FIG. 1 is an operation flow chart showing an embodiment of the present invention.

FIG. 2 is a time chart for explaining the above embodiment.

FIG. 3 is a time chart for explaining the features of the above embodiment.

FIG. 4 is a perspective view showing the outer appearance of an image reading apparatus embodying the present invention.

FIG. 5 is a diagram showing a main part of the image reading apparatus.

FIG. 6 is a flowchart of a conventional shading correction data reading operation.

FIG. 7 is a diagram for explaining a problem of a fluorescent lamp as a reading light source.

FIG. 8 is a diagram showing an example of a light source in the image reading apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casing 2 Original pressing cover 5 Original table 20 Transmissive light source unit 21 Fluorescent lamp 48 CCD sensor 54 Convergent rod lens array 55 Reflective light source unit 56 Fluorescent lamp

Claims (2)

[Claims] 1. An image reading method for reading and storing black reference data and white reference data for shading correction prior to reading an original, which is set in advance for stabilizing the light source after turning on the reading light source. In an image reading method having a step of reading and storing the white reference data after a lapse of a certain period of time, after performing the above steps, the step of reading and storing the white reference data is repeated every predetermined time, each time the previous time. There is a step to determine whether the difference data between the stored data and the data stored this time is within the allowable range. If it is within the allowable range, it is determined that the light source is stable, An image reading method, wherein the stored data is used as the white reference data and the following step is executed. 2. The next step is executed with the latest stored data as white reference data, provided that both the previous difference data and the current difference data are within the allowable range. 1. The image reading method described in 1.