JP2002325178A - Noncontact image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a noncontact image reader that can automatically be adapted to an environment after illuminance change and use a stable gamma correction value at all times without the need for an artificial change work for the gamma correction value even on the occurrence of a large illuminance change when reading an image under the illumination in an installed environment. SOLUTION: The noncontact image reader reads an image of an object 11 placed on a read stand 10 having a black color part, reads a level of the black part of the read base 10 around the object 11, calculates a black level reference value based on the read level of the black part, and applies gamma correction to the image by using the calculated black level reference. Thus, the image reader can read the image with an optimum gamma correction value of a CCD adapted to the illumination environment at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
Non-contact type image reading device, such as a stand type, in which an image pickup unit using a CD sensor does not contact an object, particularly, it is possible to always read an image with an optimal γ correction value of a CCD sensor suitable for an illumination environment. The present invention relates to a non-contact image reading device.

[0002]

2. Description of the Related Art In an image reading apparatus employing a CCD sensor as an image pickup device, if an image read by the CCD sensor is displayed on a display device as it is, the screen may be too dark or a sufficient contrast may not be obtained. Inconvenience occurs. Therefore, the characteristics of the CCD element are sampled in advance and CC
A correction value (γ correction value) for matching the sensitivity characteristic of the D sensor to the human visual sensitivity characteristic is obtained and set as a fixed value specific to the device in hardware or software,
Using this correction value, the sensitivity characteristic of the CCD sensor is corrected to match the human visual sensitivity characteristic. Such a correction is called a γ correction, and is well known as a method of correcting the brightness of an image when reading, displaying, or printing an image.

[0003]

However, a non-contact type (for example, a stand type) in which the imaging unit and the subject are separated from each other
When general illumination such as ceiling illumination is used to illuminate a subject as in the image reading apparatus described above, a large change in illuminance causes inconvenience in γ correction using a fixed γ correction value. In particular, when the illuminance is increased (brighter), black characters and backgrounds are determined to be brighter (closer to white) with respect to the reference value,
There is a problem that it becomes whitish black.

For example, as described in Japanese Patent Application Laid-Open No. Hei 7-322080, there is a method of resetting the reference value of γ correction using a reference document every time the illuminance changes. The extra work of resetting the γ correction value using the manuscript is necessary, and the cost associated with the work increases,
Furthermore, since the image reading device cannot be used during the resetting work, there is a problem that the work progress of the user is hindered and the work efficiency is reduced.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to read an image with illumination of an installation environment (for example, ceiling illumination) in a non-contact image reading apparatus employing a CCD sensor as an image sensor. In such a case, even when a large change in illuminance occurs, it is possible to automatically adapt to the environment after the change in illuminance and to always use a stable γ correction value without requiring an artificial change of the γ correction value. An object of the present invention is to provide a contact-type image reading device.

[0006]

According to the present invention, there is provided a non-contact type image reading apparatus for reading an image of a subject placed on a reading table having a black portion. The level value of the black portion of the reading table is read, a black level reference value is calculated based on the read level value of the black portion, and γ correction is performed using the calculated black level reference value. This makes it possible to always read an image with the optimal CCD gamma correction value suitable for the lighting environment.

[0007]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram showing an outline of a non-contact type image reading apparatus according to the present invention. In the figure, 10 is a reading table, 11 is a subject, 12 is an imaging unit, 13 is a line, 14
Denotes a computer, 15 denotes a display device, 16 denotes a display image, 17 denotes a keyboard, and 18 denotes a mouse.

FIG. 2 is a diagram showing a flow of generating a corrected image by performing gamma correction on the image output read by the imaging unit and outputting the corrected image to a display device. In the figure, reference numeral 121 denotes a CCD sensor built in the imaging unit 12, 141 denotes a dedicated board 141 and 1411 built in the computer 14, a dedicated board 1
An image processing unit (comprising a CPU or the like) mounted on 41, 1412 is also mounted on the dedicated board 141,
5 shows a γ correction data memory for storing γ correction values.

First, a procedure for storing an optimum γ correction value for outputting a good image in the γ correction data memory 1412 (setting a γ correction value) will be described. FIG. 3 is a flowchart illustrating a procedure for storing the γ correction value in the γ correction data memory 1412. Hereinafter, description will be made according to the flowchart of FIG.

First, the CCD sensor 12 in the image pickup unit 12
In step S101, a black level value is read from the glossy black reading table 10 (step S101). Next, a black level reference value is obtained by the image processing unit 1411 in the dedicated board 14 based on the black level value read from the reading table 10, and a γ curve is calculated from the black level reference value (step S102). FIG. 4 is a diagram illustrating an example of a γ curve (a correction curve that associates an input value with an output value by γ correction) calculated using the black level reference value 20 obtained by the image processing unit 1411. Finally, the calculated γ curve (γ curve in FIG. 4) is stored in the γ correction data memory 1412 (step S10).
3).

Next, the image read from the subject 11 is referred to as γ
A procedure for correcting the data and displaying the corrected data on the display device will be described. FIG. 5 is a flowchart for explaining a procedure for correcting an image read from the subject 11 using the γ correction value stored in the γ correction data memory 1412 and displaying the corrected image on the display device. Hereinafter, description will be given according to the flowchart of FIG.

The subject 11 placed on the reading table 10 is read by the CCD sensor 121 built in the imaging section 12 (step S201). The image of the subject 11 read by the CCD sensor 121 is corrected by the image processing unit 1411 using the γ curve (γ correction value) stored in the γ correction data memory 1412 (step S202). The gamma-corrected image is displayed and output on the screen of the display device 15 as the gamma-corrected image 16 (step S203).

FIG. 6 shows the flow of the processing from step S101 to step S103 in FIG. 3 and the processing from step S201 to step S203 in FIG. 5 by using the reading table 10, subject 11, CCD sensor shown in FIG. FIG. 12 is a diagram showing the image processing unit 121, image processing unit 1411, and γ correction data memory 1412 in association with the device configuration.

Each of the processes in the flowcharts shown in FIGS. 3 and 5 is converted into a program code in advance and stored in the memory of the computer (personal computer 14) so that menu selection or button operation on the display screen can be performed. Γ even when a large change in illuminance occurs
It is possible to automatically adapt to the environment after the change in the illuminance and to always use a stable γ correction value without requiring an artificial change operation of the correction value.

Normally, when the present image processing apparatus is used in a stable illumination environment without fluctuation, even if the γ correction value is set in the γ correction data memory 1412 in advance, the subject 1
If the adjustment of the image correction is performed before the reading of 1, the device can be used without any trouble. However, when a large change in illuminance, particularly when the illuminance increases (brightens), the entire subject 11 becomes bright,
If the γ correction value is fixed, a bright portion (particularly black) is determined to be a color (color close to white) higher than the black level reference value, and an image appears to be raised. There is also a method of adjusting the shutter speed of the camera to suppress brightness, but this method darkens the entire image.

In such a case, by resetting the γ-correction value of the γ-correction data memory 1412 using the glossy black reading table 10, it is possible to suppress the floating of the image and obtain a good image. It becomes possible. The resetting of the γ correction value may be performed in the same manner as the flowchart of the procedure for storing the γ correction value in the γ correction data memory shown in FIG.
By performing the γ correction using the γ correction value reset as described above, it is possible to output a good read image even when a large change in illuminance occurs when the subject 11 is read.

FIG. 7 is a view showing another embodiment of the reading table. If only the black reading table 10 having no gloss is used, there is a problem that, when the black level reading area is dirty, the reference value of the γ correction due to the stain varies or fluctuates. Even in such a case, as shown in FIG.
Are distributed and the black level reading in step S101 in FIG. 3 is performed using the plurality of black level reading areas 101, thereby performing the γ correction while suppressing the fluctuation of the reference value due to the contamination of the reading table. As a result, a good read image can be output.

The reading of the plurality of black level value reading areas 101 of the reading table is performed by reading an image of the entire reading table, and a predetermined plurality of black level value reading areas are determined from the entire image of the reading table. It can be done by cutting out.

When obtaining the γ correction value, the average of all the black level value reading areas may be used. Alternatively, the maximum and minimum values may be used without using the black level value reading area 101 provided on the reading table 100. By using only the remaining black level value reading area excluding the black level value reading area indicating the amount of received light, the specific black level value reading area becomes extremely dirty or whitish with a large amount of reflected light adheres. In this case, it is possible to suppress a change in the reference value (black level reference value) of the γ correction and obtain a good read image.

[0020]

As described above in detail, according to the present invention, when reading an image under the illumination of the installation environment, it is necessary to manually change the γ correction value even when a large change in illuminance occurs. Therefore, it is possible to realize a non-contact image reading apparatus that automatically adapts to the environment after the change in illuminance and can always use a stable γ correction value.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a non-contact type image reading apparatus according to the present invention.

FIG. 2 is a diagram illustrating a flow of generating a corrected image by performing gamma correction on an image output read by an imaging unit and outputting the corrected image to a display device.

FIG. 3 is a flowchart illustrating a procedure for storing a γ correction value in a γ correction data memory.

FIG. 4 is a diagram illustrating an example of a γ curve calculated using a black level obtained by an image processing unit.

FIG. 5 is a flowchart illustrating a procedure for correcting an image read from a subject using a γ correction value stored in a γ correction data memory and displaying the corrected image on a display device.

6 is a diagram showing the flow of processing in FIG. 3 and processing in FIG. 5 in association with the device configuration shown in FIG. 2;

FIG. 7 is a diagram showing another embodiment of the reading table.

[Description of Signs] 10, 100: reading table, 11: subject, 12: imaging unit, 121: CCD sensor, 13: line, 14: computer (personal computer), 141: dedicated board, 1411: image processing unit, 1412: γ correction data memory, 15: display device, 16: display image, 17: keyboard, 18: mouse, 20: black level reference value, 101: black level value reading area.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 1/19 H04N 1/10 5/243 1/40 101B F-term (Reference) 2H110 CB45 CD07 CE02 5B057 AA11 BA11 BA24 CA08 CB08 CC03 CE11 CH01 CH11 DA08 DA16 5C022 AB19 AC42 CA07 5C072 AA01 BA05 BA13 EA05 LA12 RA06 UA11 UA17 5C077 LL19 LL20 MM20 NN02 PP15 PP45 PQ12 PQ22 SS01 SS06

Claims (3)

[Claims] 1. A non-contact type image reading apparatus for reading an image of a subject placed on a reading table having a black portion, comprising: reading means for reading a level value of a black portion of the reading table around the subject; Black level reference value calculation means for calculating a black level reference value based on the level value of the black portion,
And a gamma correction unit for performing gamma correction using the calculated black level reference value. 2. The non-contact type image reading device according to claim 1, wherein the reading unit is a unit that reads a level value of a black portion from a plurality of areas of the reading table, and a reading position from the reading table or the reading position. A non-contact type image reading apparatus wherein fluctuations of the reference value due to a state of a reading position are suppressed. 3. The non-contact image reading device according to claim 1, wherein each function of said reading means, said black level reference value calculating means, and said γ correcting means is executed by a program. Non-contact type image reading device.