JPH06164845A - Picture reader - Google Patents

Abstract

PURPOSE:To obtain picture data with high gradation over the entire density without changing a copy lamp voltage. CONSTITUTION:The reader is provided with a CCD 42 to read an original picture, an amplifier 307 amplifying an output from the CCD 42, and a CPU 30 selecting an amplification factor of the amplifier 307, and original picture data obtained by reading an original picture twice or over while the amplification factor is varied are synthesized to obtain original picture data with high gradation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus using a photoelectric conversion element (CCD) used in a digital scanner unit, a digital copying machine, a facsimile and the like.

[0002]

2. Description of the Related Art An image reading device for reading a document and converting it into image data is used in a digital copying machine or a facsimile. This image reading device has a photoelectric conversion means C for reading an image and converting it into an electric signal.
CD has been adopted.

By the way, in these image reading apparatuses, poor gradation property in a high density portion due to the characteristics of CCD has been a problem, and measures have conventionally been taken to overcome this problem. For example, in a digital copying machine, the gradation of a high density portion is improved by changing the light quantity of a copy lamp.

FIG. 6 shows the CCD output with respect to the original density when the copy lamp voltage (VCL) is low (FIG. 6A) and high (FIG. 6B). When the copy lamp voltage is low, the output change ΔV1 of the CCD output with respect to the document density change in the dark portion is small. On the other hand, when VCL is high, the output change .DELTA.V1 'is large and the density gradation of this portion is good. However, there is too much reflected light in the light part,
Since the CCD output is saturated, the image data read both when the VCL is low and when the VCL is high are combined at the time of printing to obtain a high gradation copy for the entire density region.

[0005]

The above-mentioned conventional technique requires a low copy ramp voltage for reading the entire density area and a high copy ramp voltage for reading the dark density area. Therefore, the copy lamp voltage is required. Had to make a big change. If the lamp is higher or lower than the rating, the life will be shortened.
Such a large change in the voltage of the copy lamp is extremely disadvantageous. Further, the circuit for controlling the copy lamp voltage becomes complicated and the wattage of the lamp also becomes large.

Therefore, the present invention is to provide an image reading apparatus capable of obtaining high gradation image data in the entire density range without largely changing the copy lamp voltage.

[0007]

In the present invention, the above object is to provide a photoelectric conversion means for reading an original image,
Amplifying means for amplifying the output from the photoelectric converting means, means for obtaining document image data from the output of the amplifying means, amplification rate switching means for switching the amplification rate of the amplifying means, and twice for changing the amplification rate. This is achieved by an image reading apparatus including a synthesizing unit that synthesizes document image data obtained by reading the above-described document image to form one document image data.

[0008]

According to the above construction, first, the first original image is read with a relatively low amplification factor. The output from the photoelectric conversion means is amplified by the amplification means, and the first original image data is obtained from this. Next, the amplification factor switching unit increases the amplification factor of the amplification unit and the second original image reading is performed. The output from the photoelectric conversion means is amplified by the amplification means, and the second original image data is acquired from this. When the first and second original image data are obtained, the two original images are combined to form one original image data.

[0009]

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

FIG. 2 is a diagram showing the configuration of a digital copying machine to which the image reading apparatus of the present invention is applied. The digital copying machine 30 of this embodiment includes a scanner unit 31, a laser printer unit 32, a multi-stage paper feeding unit 33, and a sorter 34.
Is provided. The scanner unit 31 is an embodiment of the image reading apparatus of the present invention.

The scanner unit 31 includes a document placing table 35 made of transparent glass and a double-sided automatic document feeder (RDF) 36.
And a scanner unit 40.

The multi-stage paper feeding unit 33 includes the first cassette 5
It has the 1st, 2nd cassette 52, the 3rd cassette 53, and the 5th cassette 55 which can be added by selection.

In the multi-stage sheet feeding unit 33, the sheets are fed out one by one from the sheets stored in the cassettes of the respective stages and are conveyed to the laser printer section 32.

The RDF 36 sets a plurality of originals at one time, automatically feeds the originals one by one to the scanner unit 40, and one side or both sides of the original is scanned by the scanner unit 40 according to the operator's selection. It is configured to be read by.

The scanner unit 40 includes a lamp reflector assembly 41 for exposing a document, a plurality of reflecting mirrors 43 for guiding a reflected light image from the document to a photoelectric conversion element (CCD) 42, and a reflected light image from the document on the CCD 42. It includes a lens 44 for imaging.

When scanning a document placed on the document table 35, the scanner section 31 is configured to read the document image while the scanner unit 40 moves along the lower surface of the document table 35. When the RDF 36 is used, the document image is read while the document is being conveyed while the scanner unit 40 is stopped at a predetermined position below the RDF 36.

The image data obtained by reading the original image with the scanner unit 40 is sent to the image processing unit and subjected to various processing, and then temporarily stored in the memory of the image processing unit and stored in the memory according to the output instruction. The image data in the image is supplied to the laser printer unit 32 to form an image on a sheet.

The laser printer section 32 includes a manual document tray 45, a laser writing unit 46, and an electrophotographic process section 47 for forming an image.

The laser writing unit 46 is a semiconductor laser that emits a laser beam according to the image data from the above-mentioned memory, a polygon mirror that deflects the laser beam at a constant angular velocity, and a laser beam that is deflected at a constant angular velocity is an electrophotographic process section. It has an f-θ lens and the like for correcting so as to deflect at a constant velocity on the photosensitive drum 48 of 47.

The electrophotographic process section 47 comprises a charging device, a developing device, a transfer device, a peeling device, a cleaning device, a static eliminator and a fixing device 49, which are arranged around the photosensitive drum 48 in a known manner. .

A conveying path 50 is provided on the downstream side of the fixing device 49 in the conveying direction of the sheet on which an image is to be formed. The conveying path 50 is connected to the conveying path 51 leading to the sorter 34 and the multi-stage sheet feeding unit 33. It branches into a communication path 58 which is in communication.

The conveying path 58 is branched in the multi-stage sheet feeding unit 33, and the reversing conveying path 50 is formed as a conveying path after branching.
b and a double-sided / composite transport path 50b are provided.

The reverse conveyance path 50b is a conveyance path for reversing the front and back sides of a sheet in a double-sided copy mode for copying both sides of a document. The double-sided / composite conveyance path 50b conveys a sheet from the reverse conveyance path 50b to the image forming position of the photosensitive drum in the double-sided copy mode, or a composite copy in which an image of a different original or an image of different color toner is formed on one side of the sheet. In the single-sided composite copy mode for carrying out the above, it is a conveyance path for conveying the sheet to the image forming position of the photosensitive drum 48 without inverting it.

The multi-stage paper feeding unit 33 includes a common conveyance path 56, and the common conveyance path 56 includes the first cassette 51 and the second cassette 51.
The sheets from the cassette 52 and the third cassette 53 are carried out toward the electrophotographic process section 47.

The common conveying path 56 is the electrophotographic process section 47.
On the way to, it merges with the transport path 59 from the fifth cassette 55 and leads to the transport path 60.

The conveying path 60 merges with the conveying path 61 from the double-sided / composite conveying path 50b and the manual document tray 45 at the confluence point 62 to form an image between the photosensitive drum 48 of the electrostatic photography process section 47 and the transfer device. The confluence point 62 of these three conveyance paths is provided at a position close to the image forming position.

Therefore, in the laser writing unit 46 and the electrophotographic process section 47, the image data read from the above-mentioned memory is the laser writing unit 46.
The toner image formed as an electrostatic latent image on the surface of the photosensitive drum 48 by scanning the laser configuration by the toner is visualized with toner, and the toner image is statically formed on the surface of the sheet conveyed from the multi-stage sheet feeding unit 33. It is electrotransferred and fixed. The sheet on which the image is formed in this manner is sent from the fixing device 49 to the sorter 34 via the transport paths 50 and 57, or is transported to the reverse transport path 50b via the transport paths 50 and 58.

FIG. 3 is a circuit block diagram of the scanner unit according to the present invention. An exposure lamp 301 is provided in the scanner unit so as to be close to the document. Exposure lamp 301
Is supplied with a copy lamp voltage from a power supply 306. A CCD 42 is provided close to the document so as to receive the reflected light from the document. The CCD 42 converts the received light into a voltage according to its intensity and outputs it. CCD4
The output Vccd from 2 is an amplifier 30 to amplify this voltage.
It is entered in 7. The output VG from the amplifier 307 is an analog / digital converter (hereinafter referred to as an A / D converter).
The output that has been input to 302 and converted into a digital value is input to a white / black correction circuit 303 for performing white / black correction. The corrected image signal is input to the memory 304 as original image data and stored therein. The central processing unit (CPU) 305 controls the amplification factor,
And an amplifier 3 for synthesizing a plurality of original image data.
07 and the memory 304.

The operation of the above configuration will be described below with reference to the flow chart shown in FIG. The following operation is pre-programmed in the CPU 305 and is performed under the control of the CPU 305.

First, a document is scanned with a low amplification factor (step S1). The document is read while the scanner unit 40 moves. At this time, the reflected light from the exposure lamp 301 enters the CCD 42, and the output Vcc according to the amount of received light is output.
D occurs. The VCCD is amplified by the amplifier 307, and the output VG is converted into the digital value D1 by the A / D converter 302. The digital value D1 is the white / black correction circuit 30 of the next stage.
As is well known, the white / black correction circuit corrects the CCD output variation such as uneven light distribution to obtain a quantitative value. The output D2 is temporarily stored in the memory 304. The CPU 305 controls the amplification factor G of the amplifier during the first scan to be low.

When an A / D converter 302 having a resolution of 8 bits is used for a grayscale original as shown in FIG. 4A, the image data as shown in FIG. D2 is obtained, grayscale number 1
The CPU 305 controls all of the densities by controlling the amplification factor G so that the range from white to black of 6 is within the dynamic range of the A / D converter 302.

However, as described above, there is little change in the dark density, and the gray scale number 4,
Regarding the densities of 5 and 6, the range of change is extremely small and the gradation is deteriorated.

Then, the CPU 305 takes out the image data D2 once stored in the memory 304, and if the density below a certain threshold value, here, the threshold value is set between 3 and 4 of the gray scale, All the gray scales 4, 5 and 6 are replaced with the same FFH as white and are stored again in the memory as the first image data (step S
2). The image data at that time is as shown in FIG.

Next, in step S3, the CPU 305 raises the amplification factor G of the amplifier and performs the original reading operation again. Image data D for each density at that time is shown in FIG.
The relationship of 2 is shown. The amplification factor G is set so that a density slightly higher than the threshold value falls within the dynamic range of the A / D converter 302.

The image data D2 is the same as that at the first time.
The data is stored in the memory (however, the memory area is changed). Next, in step S4, the CPU 305 reads this data as a bright data value (in this case, the value of gray scale 3) and the darkest density than the read threshold value. The difference Δα3 from the data value of (in this case, the value of gray scale 6),
Then, based on the value, the value DM of each concentration is obtained using the equation (1).

DM = α3− (Δαn / Δα3) × α3 (1) where α3 is the density value of the gray scale 3 in the first scan, and the density difference of Δαn from the gray scale 3 of each pixel. Is.

After calculating the above, the process proceeds to step S4,
The CPU 305 sets all density values brighter than the threshold value to F
It is replaced with FH (white) and the second image data is stored in the memory again. FIG. 4 (e) shows the image data.

Finally, in step S5, the CPU synthesizes the two image data and outputs it to the next stage. FIG. 4F shows the resulting image data D3, and high-gradation image data is obtained.

The circuit configuration and calculation method of the present embodiment is one example for obtaining high-gradation image data, and the method is not limited to this, and the present invention uses CC for a plurality of scans.
The feature is that the amplification factor G of the D output is changed to improve the gradation performance of dark density.

An example of realizing control of the amplification factor G by the CPU will be described with reference to FIG.

In this example, the non-inverting amplifier circuit of the operational amplifier 501 is used as the amplifier. The output Vccd from the CCD is input to the non-inverting input of the operational amplifier 501, and its inverting input is grounded via the resistor R1. The output of the operational amplifier 501 is input to the inverting input via the resistor R2 and the resistor R2 and the resistor R3 in parallel. An analog switch 5 is placed on both ends of the resistor R2.
02 and 503 are inserted, and analog switches 504 and 505 are inserted at both ends of the resistor R3. The control signal V1 from the CPU 305 is input to the analog switches 502 and 503.
A control signal V2 from the CPU 305 is input to the CPUs 4, 505. CPU305 turns on the analog switch
By turning OFF, the constants that determine the amplification factor G are selected.

When the control signal V1 is set to the H level, the analog switches 502 and 503 are turned on and the resistor R2 is connected to the circuit. The amplification factor G1 at this time is G1 = R1 + R2 / R1.
Becomes

Next, when V2 is set to H level, the analog switches 504 and 505 are turned on, the resistor R3 is connected to the circuit, and the amplification factor G2 becomes G2 = R1 + R3 / R1.

Here, the resistors R1, R2, and R3 have an amplification factor G1 so that the range from white to black is within the dynamic range of the A / D converter 302, and the dynamic range is a little brighter than the threshold value. Amplification factor G
Selected to be 2.

As described above, the CPU 305 controls the amplifier 3
The amplification factor G of 07 is controlled.

[0046]

As described above in detail, according to the present invention, the amplification factor G of the CCD output is changed by a plurality of scans,
By combining the obtained multiple original image data,
Since one sheet of high-gradation original image data is obtained, the copy lamp voltage only needs to be a low copy lamp voltage for reading the entire density area, and the wattage of the lamp is also low as compared with the prior art. Furthermore, since the copy lamp voltage does not need to be changed significantly, the control circuit can be simplified, and since the rated voltage does not change significantly, the life of the lamp is improved.

[Brief description of drawings]

FIG. 1 is a flowchart showing an operation flow of an embodiment of an image reading apparatus according to the present invention.

FIG. 2 is a diagram showing a configuration of a digital copying machine to which the image reading apparatus of the present invention is applied.

FIG. 3 is a circuit block diagram showing a circuit configuration of an embodiment of an image reading apparatus according to the present invention.

FIG. 4 is a diagram showing image data at each stage of the operation of the image reading apparatus shown in FIG.

5 is a circuit diagram showing a circuit configuration of an example of an amplifier circuit used in the image reading apparatus shown in FIG.

FIG. 6 is a diagram showing the relationship between document density and CCD output with two different copy lamp voltages.

[Explanation of symbols]

 42 CCD 301 Exposure Lamp 302 Analog-to-Digital Converter 303 White / Black Correction Circuit 304 Memory 305 CPU 306 Power Supply 307 Amplifier 501 Op-Amp 502 to 505 Analog Switch

Claims (1)

[Claims] 1. A photoelectric conversion means for reading an original image, and an amplification means for amplifying an output from the photoelectric conversion means,
A unit for obtaining original image data from the output of the amplifying unit, an amplification factor switching unit for switching the amplification factor of the amplifying unit, and an original image data obtained by reading the original image two or more times with different amplification factors. An image reading apparatus comprising a synthesizing unit for synthesizing to form one document image data.