JPS61224781A - Shading correcting control system - Google Patents

Abstract

PURPOSE:To calculate the correct white level over the whole area by storing an image signal corresponding to the brightness of the light source which changes following the passing of the time, and correcting the level to slice the image signal based upon the stored image. CONSTITUTION:A fluorescent lamp 1 lights up, brightness is increased gradually and the characteristic, in which this is large, exists at the peripheral part of the tube ball. By the light radiated from such a fluorescent lamp 1, an original 2 is irradiated, the reflected light is image-picked up on the photodetecting surface of a CCD 4 by a lens 3 and the analog image signal can be obtained. An image signal is converted to the digital image signal by an A/D converter 5, supplied to a slice circuit 6, and the prescribed scanning line is stored into a memory 7. The image signal supplied to the slice circuit 6 is converted and sent to a binary image signal, for example, with the half value of said white level signal as a slice level, by using the white level signal calculated by a shading correcting calculating means 11, and therefore, the correct white level can be obtained over the whole area of the fluorescent lamp.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention uses a shading correction control method, in particular, illuminates an original using a light source such as a fluorescent lamp, and uses COD or the like to image the light reflected from the original. When converting to a signal, the level at which the image signal is sliced is corrected in response to the brightness of the light source that fluctuates over the course of 9 hours, so that a good image signal can be obtained. The present invention relates to a shading correction control method.

[Problems to be solved by conventional technology and invention] Conventionally,
Illuminate the original using a light source such as a fluorescent light.

COD (ch.
An analog image signal was obtained by forming an image on the photocathode of a large coupled device. Then, the analog image signal is converted into a digital image signal using an A/D converter with 8-bit resolution, for example, and then binarized at a predetermined level to produce a so-called image signal. I was getting . At this time 9
For example, when a fluorescent lamp is used as a light source, it takes 3 to 10 minutes for the fluorescent lamp to emit light of stable brightness, and if you try to obtain a high-quality image signal using the COD immediately after the lamp is turned on, It is necessary to determine the slice level while detecting the brightness of the fluorescent light (for example, blood-level brightness or white level) and perform the binarization described above. As a method of determining the slice level, there is a method of constantly detecting the maximum brightness (white level) of the image signal before binarization photoelectrically converted by the COD and determining the slice level at that point in time. In this method, for example, because the amount of information in the image signal sent from a scanner equipped with a CCD is enormous or the sending speed is too fast, it is necessary to temporarily stop sending out the image signal from the scanner. In this case, it is not always possible to detect a white level signal in the temporarily stopped image signal, so the white level cannot be detected and an appropriate slice level cannot be determined for all dots. There was a problem. Also,
In order to detect the brightness of the fluorescent lamp, there are methods that use specific bits in the image signal as monitor bits or arrange new detection elements, but these methods particularly detect the light around the fluorescent lamp. Since the brightness rise characteristics of the dots and the brightness rise characteristics of the central part are different, it is necessary to accurately detect the brightness corresponding to each position and determine the appropriate slice level for all dots. However, there was a problem in that a high-quality image signal could not be obtained.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention illuminates an original using a light source such as a fluorescent lamp, and converts the light reflected from the original into C.
When converting into an image signal using OD or the like, an image signal corresponding to the brightness of the light source that changes over the course of one hour is stored.

By predicting fluctuations in the brightness of the light source while the scan is stopped based on the stored image signals and performing correction control, it is possible to achieve good results over the entire area, such as the peripheral area and the central area of the fluorescent lamp. The white level can be detected. Therefore, the shading correction control method of the present invention is configured to read image data by correcting the level of an image signal obtained by photoelectrically converting the light from the irradiated document. A photoelectric converter that photoelectrically converts light from an original, an A/D converter that converts the signal photoelectrically converted by the photoelectric converter into a digital signal, and a white image signal that is converted into a digital signal by the A/D converter. A white level holding memory that holds the level, and a first white level holding memory that sequentially saves the white level held in the white level holding memory.
and a second data holding means; measuring the elapsed time from saving the white level to the first data holding means until saving the white level to the second data holding means; After saving the white level to the data holding means,
A measuring means for measuring the elapsed time until starting reading again, and starting the reading again based on the white level stored in the first and second data holding means and the elapsed time measured by the measuring means. and shading correction calculation means for calculating a value at which the white level changes within the elapsed time until the white level changes, and the image data is read by correcting the level of the image signal using the white level calculated by the shading correction calculation means. It is characterized by being configured to perform the following.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a configuration diagram of one embodiment of the present invention, FIG. 2 is an operation explanatory diagram explaining the operation of the configuration of one embodiment of the present invention illustrated in FIG. 1, and FIG. 3 is an embodiment of the present invention illustrated in FIG. 1. A flowchart illustrating the operation of an example configuration is shown.

In the figure, 1 is a fluorescent lamp, 2 is a document, 3 is a lens, and 4 is a CCD.
, 5 is an A/D converter, 6 is a slice circuit, 7 is a memory, 8 is a register A, 9 is a register B, 10 is a measurement means, and 11 is a shading correction calculation means.

In FIG. 1, a fluorescent lamp 1 in FIG. 2 is a light source for irradiating a document 2, and has a property that the brightness gradually increases after being turned on until a stable state is reached. Furthermore,
The fluorescent lamp 1 has a characteristic that the rate of increase in brightness during lighting is generally large at the periphery of the bulb and small at the center of the bulb due to preheating by the filament during lighting.

The document 2 is irradiated with light emitted from the fluorescent lamp l having the characteristics described above. Then, the light reflected from the original 2 is imaged by the lens 3 on the light receiving surface of the C0D 4,
By inputting a control signal for reading to the CCD 4, an analog image signal can be obtained. The analog image signal is converted into, for example, an 8-bit digital image signal by an A/D converter 5, and is supplied to a slice circuit 6, and a predetermined scan line is stored in a memory 7. The image signal supplied to the slice circuit 6 is converted into an illustrated white level signal (
For example, half the value of the white level signal is set as the slice level, and the image signal is converted into a binary image signal and sent out. Figures 2 and 3 below
Using the diagram, register A (8), register B (
9) The operations of the measuring means 1O and the shading correction calculating means 11 will be explained in detail.

Figure 2 (A) shows that the document 2 in Figure 1 is at the scanning start position (
Time “1.” from A) to scan stop position (B)
is scanned, and the relevant stop position (B) is scanned.
The scan is temporarily stopped for a time “t,” and then the stop position! Time “t” from (B) to end position (C),
” indicates its status as being scanned by spending.

On the other hand, FIG. 2 (b) shows a brightness characteristic curve.

The horizontal axis is the so-called C in the direction perpendicular to the moving direction of the document 2.
Indicates the direction scanned by CD4.

The vertical axis indicates the magnitude of the image signal output from C0D4. Also, the brightness characteristic curve (A) in Figure 1.

(B+) and (B2) are at the scan start position (A) in Figure 2 (A) and at the scan stop position (B).
Immediately after reaching , and scan stop position (B)
Each represents the scan immediately before starting the scan again after a time "t2" after reaching .

Furthermore, the characteristic curve described using a single dotted line is the characteristic curve (A
) are shown in similar form.

To explain in detail, the characteristic curve (A') in Fig. 2 (b) is the second
Figure (A) Scan start position in the figure (A) (time “t=Q”)
) shows the envelope of the white level of the image signal output from the A/D converter 5 in FIG. In this way, the characteristic curve (A) is the envelope of the white level of the image signal.
shows a characteristic that it is high at the center and gradually decreases toward the periphery of 9.

The characteristic curve (Bl) in FIG. 2(B) shows the A/D converter 5 in FIG. This shows the envelope of the white level of the image signal output from the . The characteristic curve (B,) after the elapse of time "t" with respect to the characteristic curve (A) explained above is as follows.

Not only does the white level increase monotonically, but the increase in white level in the peripheral part of the characteristic curve (B1) is "AL", while the increase in white level in the central part is "A". ``The increase in the periphery is larger than the increase in the center. this is.

Immediately after the fluorescent lamp 1 was turned on, the main cause was that the surrounding area was rapidly heated by the heat from the filament that was preheated when the fluorescent lamp 9 was turned on. Therefore, in the present invention, for example, the characteristic curve (A) of the image signal at time "t=Q" is stored in thruster A in FIG. 1, and the characteristic curve (B1) of the image signal after 9 hours "1=1." ) is stored in thruster B in FIG. Then, the characteristic curve (B2) of the image signal after the stop time t2 has elapsed is calculated using the following formula at each dot position.

B, -A B 2= B, +-x t, ...
Tl) The calculation according to equation (11) is executed by the shading correction calculation means 11 in FIG. 1, and the resulting characteristic curve (Bz) is shown in (B2) in FIG. As shown in Figure 2 (A), the stop position in Figure 2 (B)
Even if the movement of the document is temporarily stopped during the time "t2", it is possible to accurately calculate the white level of the image signal after the elapse of the time "t2".

The calculated white level signal of the image signal is supplied to the slice circuit 6 in FIG. be converted into Also. Second
The reference curves shown using dotted lines in the figure (B) are similar to the characteristic curve (A), that is, characteristic curves expressed by proportionally changing only the magnitude of the image signal. As will become clear from comparison with the reference curve, according to the present invention, even if scanning of the document 2 is temporarily stopped, the image signal that changes during the stopped time, for example, the white By calculating the level for each dot using equation (1), the white level is accurately calculated and the image signal is binarized, resulting in a high-quality two-dimensional image.
A valued image signal can be obtained.

Next, the operation of the configuration shown in FIG. 1 will be explained using the flowchart shown in FIG. 3.

In FIG. 3, ■ indicates a state in which the white level is recorded.

This means that the white level of the image signal is stored in the memory 7 in FIG.

In the figure, ■ indicates a state in which the MPU saves the white level signal. This means that the white level signal stored in the memory 7 in FIG. 1, for example, the white level signal corresponding to the characteristic curve (A) in FIG. 2 (b), is saved in the register A (8). do.

■ in the figure indicates a state in which reading is performed. this is.

FIG. 2(A) means that the image signal is read during the time "tl" in the figure.

In the figure, ■ indicates a state in which the MPU saves the white level signal. This is done in the same manner as (■) in Fig. 1. The white level signal stored in the memory 7 in Fig. 1, for example, the white level signal corresponding to the characteristic curve (B,) in Fig. 2 (b) is transferred to the register B ( 9
) means to take shelter.

■ in the figure indicates a state in which reading is stopped. This is the second
Figure (A) means that the feeding of the original 2 is temporarily stopped for a time "t2" at the stop position (B) in the figure to stop reading.

In the figure, ■ indicates a state in which white level correction is performed and restoration is performed. This means that the characteristic curve (B2) in FIG. 2 representing the white level of the image signal after the elapse of time "11" is calculated using equation (1) as described above.

■ in the figure indicates a state in which reading of the image signal is started again using the white level calculated in ■ in the figure.

Through the above procedure, even if scanning is temporarily stopped, the white level fluctuation during the stopping time can be accurately calculated using equation (1), so that good binarization is always achieved. It becomes possible to obtain an image signal.

〔Effect of the invention〕

As explained above, according to the present invention, an original is irradiated using a light source such as a fluorescent lamp, and the light reflected from the original is used for C'C
When converting to an image signal using D or the like, an image signal corresponding to the brightness of the light source that changes over the course of 9 hours is stored, and scanning is stopped based on the stored image signal. Since the brightness of the light source is controlled to compensate for fluctuations in brightness between the two, the white level is accurately calculated over the entire area such as the periphery and center of the fluorescent light, resulting in a high-quality binary image signal. can be obtained.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of one embodiment of the present invention, FIG. 2 is an operation explanatory diagram explaining the operation of the configuration of one embodiment of the present invention illustrated in FIG. 1, and FIG. 3 is an embodiment of the present invention illustrated in FIG. 1. A flowchart illustrating the operation of an example configuration is shown. In the figure, 1 is a fluorescent lamp, 2 is a document, 3 is a lens, and 4 is a CCD.
, 5 is an A/D converter, 6 is a slice circuit, 7 is a memory, 8 is a register A, 9 is a register B, 10 is a measurement means, and 11 is a shading correction calculation means. Patent applicant: Usatsuk Electronic Industry Co., Ltd. Representative patent attorney: Hiroshi Mori (2 others) Figure 3

Claims (1)

[Claims] In a shading correction control method configured to read image data by correcting the level of an image signal obtained by photoelectrically converting the light from the irradiated original, a photoelectric converter that photoelectrically converts the light from the irradiated original. and,
an A/D converter that converts the photoelectrically converted signal by the photoelectric converter into a digital signal; and a white level holding memory that holds the white level of the image signal converted to the digital signal by the A/D converter. first and second data holding means for sequentially saving the white level held in the white level holding memory; and after saving the white level in the first data holding memory, the second data holding means measuring means for measuring the elapsed time until the white level is saved in the second data holding means, and measuring the elapsed time until starting reading again after the white level is saved in the second data holding means; Shading correction that calculates a value at which the white level changes within the elapsed time until the reading starts again based on the white level stored in the second data holding means and the elapsed time measured by the measuring means. 1. A shading correction control method, comprising: a calculation means, and configured to read image data by correcting the level of an image signal using the white level calculated by the shading correction calculation means.