JPH06105158A - Image input device - Google Patents

Abstract

PURPOSE:To obtain image data with high quality by detecting a luminous quantity emitted to a body to be read and changing a threshold level to an optimum value in response to a change quantity of a detected optical quantity. CONSTITUTION:A threshold level control section 19 converts a luminous quantity detection signal obtained by applying photoelectric conversion to a reflected light in a white face and a black face of reference white/black level sections 14a, 14b into data of full white level/full black level and compares the data with a reference value stored in advance. As a result, when a full white/full black level fetched by a luminous quantity sensor 13 is not coincident with a reference value, a correction quantity in response to the difference is commanded to a processor 15 via a correction control signal. The processor 15 corrects a threshold level of a binarization section 17 according to a correction control signal from the control section 19. When a program-search of an object 10 to be read is finished, the object to be read 10 is moved and an image signal for each line is inputted from the image sensor 12 to the processor 15, and an image signal is inputted to a binarization section 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image input device capable of taking in an image of an object to be read such as an original or a drawing, and more particularly to comparing an image signal of the object to be read using a threshold value. Image input device.

[0002]

2. Description of the Related Art Conventionally, an object to be read is moved relative to an image sensor to capture an image of an object, or an object to be read is fixed and an image sensor or its auxiliary device (reflecting mirror) is moved to obtain an image. It is known to read.

FIG. 4 shows an example of the configuration of an image input device of the type in which the object to be read is moved. Reference numeral 1 shown in the figure is an object to be read, and is assumed to move in the direction of the arrow shown. A light source 2 such as a fluorescent lamp is arranged so as to face the object 1 to be read, and an image sensor 3 is provided at a position where the reflected light of the object 1 to be read illuminated by the light source 2 can be detected. . Further, reference white / black portions 4a and 4b colored in white / black are provided at a position facing the image sensor 3 on the conveyance path of the object to be read 1. The image sensor 3 and the processor 5 are connected, and the output of the image sensor 3 is input to the processor 5.

In this image input device, the built-in self-diagnosis function is activated in the processor 5 immediately after the device is started up. By this self-diagnosis function, the reflected light of the reference white / black portions 4a and 4b is taken into the processor 5 via the image sensor 3, and the data of white level and black level corresponding to the light quantity of the light source 2 is stored. Then, the optimum threshold value for determining the presence / absence of an image on the object to be read is obtained based on the white level data and the black level data. The self-diagnosis function is stopped within a few tens of seconds after the start-up, and thereafter, the threshold value set at the start-up is fixed.

Next, the object to be read 1 is conveyed, the object to be read 1 is scanned by the image sensor 3, and the image signal of the object to be read 1 is input to the processor 5. The processor 5 compares the signal level of the image signal input from the image sensor 3 with a threshold value and converts the image signal into a white / black binarized image signal.

By the way, the light source 2 exhibits a change in the amount of light as shown in FIG. 5 until the amount of light generated elapses for a predetermined time from the start of lighting. For example, in the case of a fluorescent lamp, it takes several tens of minutes from the start of lighting until the light amount stabilizes.

However, in the above-described conventional image input device, an optimum threshold value is set for the light amount at time t1 when several tens of seconds have elapsed from the start of lighting, so that the light source 2 of the light source 2 is further elapsed. If the amount of light changes, the threshold value becomes improper. As a result, there is a possibility that an excessive amount of light will occur and the image quality will be significantly degraded.

Therefore, conventionally, the threshold value of the processor 5 can be manually set from the adjusting section 6 after the light quantity of the light source 2 is stabilized.

Further, a general light source has a tendency that the amount of light decreases as the usage period increases. Even with respect to such a decrease in the amount of light, the operator has to manually set the threshold value of the processor 5 from the adjusting unit 6 as necessary.

[0010]

As described above, the conventional image input device cannot use the device until the light source becomes stable, and the threshold value is manually corrected for the change in the light amount of the light source. There is a problem that it is necessary and complicated operation is required, and it is difficult to always set the optimum threshold value.

The present invention has been made in view of the above circumstances, and can be used immediately after the power is turned on without waiting for the light amount of the light source to stabilize, and the optimum threshold value that follows the light amount change of the light source. It is an object of the present invention to provide an image input device in which values can be easily set and high quality image data can be obtained.

[0012]

In order to achieve the above object, an image input device of the present invention illuminates an object to be read with a predetermined amount of light, and converts light transmitted or reflected by the object to be read into an image signal. Then, in a device for generating an image signal by comparing the signal level of the image signal with a threshold value, a light amount detecting means for detecting the light amount applied to the object to be read, and the light amount detected by the light amount detecting means. And a threshold value control means for changing the threshold value to an optimum value in accordance with the change amount.

[0013]

In the image input device of the present invention, the amount of light emitted to the object to be read is detected by the light amount detecting means, and the light amount detected by this light amount detecting means is input to the threshold value controlling means. Then, the threshold value for generating the image signal in comparison with the signal level of the image signal is set to the optimum threshold value by the threshold value control means according to the light quantity change amount of the light source detected by the light quantity detection means. Can be changed.

Therefore, it is possible to always change to a threshold value capable of converting an image signal into an optimum image signal in response to a short-term change in light amount when the power is turned on, or a long-term decrease in light amount.

[0015]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 shows a schematic structure of an image input device according to an embodiment of the present invention. The present embodiment is an image input device of a type in which an image described on an object to be read such as a document or a drawing is read by conveying the object to be read.

The image input apparatus of this embodiment is provided with a transport mechanism (not shown) for transporting the object 10 to be read in the direction of the arrow in the figure. A light source 11 is arranged so as to illuminate the object to be read 10 conveyed by the carrying mechanism at a predetermined position, and an image is formed at a position where the reflected light from the object to be read 10 illuminated by the light source 11 is efficiently incident. Sensor 12
Also, a light amount sensor 13 is provided. Reference white / black portions 14a and 14b colored in white and black, which serve as a reference when setting a threshold value, are provided near the illumination position of the object to be read 10 and below the surface on which the object to be read is conveyed.

The image sensor 12 is, for example, a CCD.
It is composed of a line sensor and converts the image of the object to be read 10 into an image signal line by line at a predetermined cycle and outputs the image signal. The light amount sensor 13 is composed of, for example, a pair of photodiodes, and is connected from the light source 11 to the reference white / black portion
The light amount irradiated to a and 14b is detected, and the light amount detection signal is output.

The image signal output from the image sensor 12 is input to the processor 15. The processor 15 is based on an A / D converter 16 for converting a signal level of an image signal input from the image sensor 12 into a bit signal having a high bit number, and an output of the A / D converter based on a threshold value described later. It is provided with a binarizing unit 17 for binarizing, and a self-diagnosis unit 18 which is activated for several tens of seconds when the power is turned on and sets a threshold value in the binarizing unit 17.

On the other hand, the light amount detection signal output from the light amount sensor 13 is given to a threshold value control section 19 as a threshold value control means. The threshold value control unit 19 compares the reference value of the all white level / all black level predetermined by the physical characteristics of the image sensor 12 with the threshold value determined from the light amount detection signal, and causes the binarization unit 17 to perform the comparison. It has a threshold optimization function that corrects the set threshold.

The threshold used in the threshold controller 19 is data of all white level / all black level. This threshold value is treated as an all-white level / all-black level based on the light amount detection signal obtained by capturing the reflected light from the white and black surfaces of the reference white / black portions 14a and 14b.

Further, the threshold value of the binarization unit 17 is constructed so that it can be manually adjusted also from the keyboard 20 connected to the processor 15.

Next, the operation of this embodiment configured as described above will be described with reference to FIG.

First, when the power is turned on, the light source 11 is driven to illuminate the reference white / black portions 14a and 14b. The reflected light from the white and black surfaces of the reference white / black portions 14a and 14b is captured by the image sensor 12 and converted into an image signal, and the image signal is input to the self-diagnosis unit 18 of the processor 15. The self-diagnosis unit 18 finds an optimum threshold value and sets it in the binarization unit 17. This self-diagnosis section 1
The operation of No. 8 is stopped in about tens of seconds after the power is turned on.

Next, the light amount detection signal of the light amount sensor 13 is taken into the threshold value control unit 19 each time the work for finding the object to be read 10 is set to the reference position of the apparatus. Note that the reference white / black portions 14a and 14b are not covered by the object to be read 10 when the object to be read 10 is set at the reference position.

In the threshold control unit 19, the reference white / black portion 1
The light amount detection signals obtained by photoelectrically converting the reflected lights of the white and black surfaces of 4a and 14b are converted into all white level / all black level data and compared with a reference value stored in advance.

As a result of the comparison, if the all-white level / all-black level fetched from the light quantity sensor 13 does not match the reference value, a correction amount corresponding to the difference is instructed to the processor 15 via the correction control signal. To do. The processor 15 corrects the threshold value of the binarization unit 17 according to the correction control signal from the threshold value control unit 19.

When the head of the object to be read 10 is finished, the object to be read 10 is moved by a transport mechanism (not shown), and an image signal for each line is input from the image sensor 12 to the processor 15. A / D of processor 15
The image signal converted into high-bit-number bit data by the converter 16 is input to the binarization unit 17.

The binarization unit 17 binarizes the signal level of the input image signal based on the threshold value set as described above and outputs it as an image signal.

The threshold value correction process as described above is carried out each time the object to be read 10 is moved to the beginning, and an optimum threshold value is always set in accordance with the actual light amount.

As described above, according to this embodiment, the light amount sensor 13 for capturing the reflected light of the white and black surfaces of the reference white / black portions 14a and 14b is provided, and the reference white / black is used when the image of the object to be read 10 is input. Since all white level / all black level data for the current light quantity is fetched from the reflected light of the black portions 14a and 14b and the threshold value is corrected by comparing with the reference value stored in advance, short-term or long-term It is possible to always set an optimum threshold value with respect to a change in the amount of light, eliminate erroneous recognition of the presence or absence of data, and obtain high-quality image data.

Further, since the optimum threshold value is automatically set, the burden on the operator can be reduced. Furthermore, the image input operation can be started immediately after the power is turned on without waiting for the light source to stabilize.

In the above embodiment, the threshold value correction is performed every time the object to be read 10 is moved to the beginning, but the change in the light amount is constantly monitored so that the light amount of the light source 11 is equal to or more than a certain value. If there is a change, the threshold value may be sequentially corrected.

FIG. 3 shows a row chart for performing such an operation. In this flowchart, in order to prevent the threshold value correction process from being frequently performed when the light amount of the light source changes little by little in a short time, when the light amount of the light source changes within a predetermined time,
It is determined whether or not a document is set, and the threshold value is corrected only when the document is set.

Further, although the threshold value is used for binarizing the image signal in the above embodiment, the present invention can be applied to the case where the threshold value is used for other purposes. Further, the image signal to be generated is not limited to the binarized data.

The present invention is not limited to the above embodiments, but various modifications can be made without departing from the gist of the present invention.

[0037]

As described above in detail, according to the present invention, it is possible to use the light source immediately after the power is turned on without waiting for the light amount of the light source to stabilize, and to set the optimum threshold value following the change of the light amount of the light source. An image input device capable of easily setting and obtaining high quality image data can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an image input device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a threshold value correcting operation in the image input device shown in FIG.

FIG. 3 is a flowchart showing another threshold value correcting operation in the image input device shown in FIG.

FIG. 4 is a block diagram of a conventional image input device.

FIG. 5 is a diagram showing a change in light amount of a light source used in the image input device.

[Explanation of symbols]

10 ... Object to be read, 11 ... Light source, 12 ... Image sensor,
13 ... Light intensity sensor, 14a, 14b ... Reference white / black portion, 1
5 ... Processor, 17 ... Binarization unit, 18 ... Self-diagnosis unit,
19 ... Threshold control unit.

Claims (1)

[Claims] 1. An object to be read is illuminated with a predetermined amount of light, and light transmitted or reflected by the object to be read is converted into an image signal,
In an image input device for generating an image signal by comparing the signal level of the image signal with a threshold value, a light amount detecting means for detecting the light amount applied to the object to be read, and a light amount detected by the light amount detecting means. An image input device, comprising: a threshold value control means for changing the threshold value to an optimum value in accordance with the change amount of