JPS63200677A - Picture reader - Google Patents

Abstract

PURPOSE:To facilitate picture adjustment even without a special tool by providing an adjusting means adjusting an amplification factor or a shift quantity of a means amplifying or shifting the level of the output of a light receiving means. CONSTITUTION:An analog picture signal obtained from a CCD 103 is eliminated for noise component by a sample-and-hold circuit 201, a black level signal is detected for each line by a DC clamp circuit 202 to always keep the black level constant. Then the signal is amplified to a signal proper for the A/D conversion by an amplifier 203 and the digital picture signal subject to A/D conversion is used as full white or black level and the result is outputted to an offset correction circuit 205, dark voltage correction is applied, sent to a shading correction circuit 206 to correct the sensitivity to a white level and the result is fed to a gamma correction circuit 207. The gamma correction circuit 207 converts the picture signal inputted while being stored with a density conversion data by using the conversion data as a RAM, and the buffer memory 208 fetches a picture signal from the gamma correction circuit 207 and gives an output to a picture recording section 209.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image reading device that photoelectrically reads an original image.

[Conventional technology]

Conventionally, in an image reading device, a light receiving element (COD, etc.)
Amplify and level convert the analog output signal from A.
/D conversion has been performed to obtain a multivalued digital signal representing the original image. In other words, it is necessary to adjust the offset and gain of the amplifier to bring the analog output signal to the appropriate level for A/D conversion, and this adjustment is performed by observing the output waveform with a measuring instrument such as an oscilloscope. was.

[Problem to be solved by the invention] However, in the conventional adjustment method described above, adjustment cannot be performed without an expensive and large measuring instrument such as an oscilloscope.
Therefore, it has the disadvantage that it can only be adjusted in places where there is equipment, such as factories, and cannot be adjusted in places where there is no equipment, such as markets.

[Means for solving problems]

The present invention has been made in view of the above points, and it is an object of the present invention to provide an image reading device that allows image adjustment to be easily performed without the need for special tools.

〔Example〕

The present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram of an image reading device to which the present invention is applied, in which 101 is a document table, 102 is a document holder, and 103 is an image reading device consisting of a plurality (several tens) of light receiving elements arranged in a line. CCD, 104 is a fluorescent lamp for illuminating the original, 105
107 is a mirror, and 108 is an imaging lens. By moving the fluorescent lamp 104 and the mirror 105 in the Y direction, the document is sub-scanned in the Y direction, and the document image is sequentially focused on the CCD 103 which performs electrical main scanning in the direction perpendicular to the Y direction. It has become.

As a result, the original image placed on the original platen 101 is
It photoelectrically reads and scans each line.

111 is a sensor that detects the position of the fluorescent lamp 104 and the mirror 105;
05 detects that there is a position.

FIG. 2 is a circuit block diagram relating to image signal processing of the image reading device shown in FIG.

The analog image signal obtained by reading the original image with the CCD 103 has its noise component removed by the sample hold 201, and only the signal component is extracted.

Further, the DC clamp circuit 202 reproduces the black level. That is, since the output of the CCD 103 can only be output relative to the black level, the DC clamp circuit 202 detects the black level signal for each line and keeps the black level constant (for example, O). . The signal 266 indicates the period during which the COD black level signal is output.

Next, the analog image signal is sent to the A/D by the amplifier 203.
It is amplified to a signal suitable for being converted. According to this example, the EF8308 (manufactured by Thomson) is used as the A/D converter, and the analog input of 0 to 2V is input from 00 to F.
Convert to FH digital signal.

Therefore, in this case, the white level output of CCDIO3 is 0.
Since it is 3V, I made a 6.6x amplifier. Although not shown, there is a circuit that constantly adjusts the light intensity of the fluorescent lamp 104 so that the output of the COD is white and 0.3V.

Next, the A/D converted digital image signal is a pure white “O
Image signal line 255 as “OH” true black “F F H”
is output to the offset correction circuit 205. The image signal input to the offset correction circuit 205 (details will be described separately) is subjected to dark voltage correction, and then sent to the shading correction circuit 20.
6, and the sensitivity to the white level is corrected.

The sensitivity-corrected image signal is sent to the γ correction circuit 207. The γ correction circuit 207 is a RAM that stores density conversion data and converts the input image signal using the conversion data and outputs it. It is now possible to write.

The buffer memory 208 is provided to match the speed of the image signal to the recording unit when capturing the image signal from the γ correction circuit 207 and outputting it to the image recording unit (printer) 209. ing.

The main scanning address CCD drive signal generation circuit 211
A lock is generated as necessary to drive D103, and an address for the - line is also generated. Using this address, each circuit can know which position is the current main scanning position.

The CPU 212 performs input display control of the operation unit 213 and generates signals for controlling each unit.

FIG. 4 shows details of the image signal processing system from the CCD 103 to the A/D converter 204.

CCD103' (for example, Toshiba TCD106C),
Two systems of outputs 200a, an odd output corresponding to an odd numbered pixel of a plurality of light receiving elements and an even numbered output corresponding to an even numbered pixel.

There is 200b, S/H2O1, DC clamp 202.
Amplifier 281. Offset volume 280. Gain volume 282. There are two sets of A/D converters 204, a and b, which are the same for even-numbered systems and for odd-numbered systems.

The image signals digitized by the A/D converters 204a and 204b are sequentially selected by the selector 283 to be divided into l systems and sent to the offset processing section 205.

In this configuration, where the CCD 103 has multiple output systems and each output is processed by a separate processing system, for example,
Due to the level difference between the even and odd outputs of the CD or the difference in characteristics between the even and odd output processing systems, a difference in level occurs between them, and the outputs are assigned to the l system by the selector 283. Variations may occur. Therefore, the offset volume 280 and gain volume 282 of the amplifiers 281a and 281b are adjusted to correct it.

FIG. 3 shows the configuration of the offset correction circuit section 205. In addition, 301.302.30'4.306 is D
This type of flip-flop (F/F) is used to match the timing of data, and can be removed if the circuit speed is slow.

This will be explained along the flowcharts of FIGS. 3 and 7.

When the copy key 807 is pressed from the operation unit shown in FIG. 6, which will be described later, the CPU 212 checks whether the optical system is at the home position (step 601), and if not, returns the optical system 104. Return 105 to the home position. Then, the CPU 21 determines whether offset correction killing is set.
2 is searched (step 6o2).

This allows a service person or the like to issue a switching instruction for testing through the operation unit 213 before starting the copy operation.

If offset correction killing has not been performed, CPU2
12 instructs to write data into the offset RAM 311 (step 603). This means that the image signal reaches the signal line 351 from the signal line 255, and the selector 308
and the selector 308 is switched to A so as to be applied to the RAM 311 through the buffer 30, and the RAM 31
The selector 312 at address 1 is also switched to A.

As a result, one line of dark image data is stored in the RAM 31.
Written to 1.

At this time, the reason why the fluorescent light is not turned on at the home position is
This is to eliminate the influence of external light and reproduce a pure black state.

Next, the CPU 212 sets a constant offset value in the flip-flop 307 (step 604). This involves latching data into the D-type flip-flop 307 via the data bus 261 of the CPU 212 and adding a constant value as an offset. The purpose of this circuit is
It is used to change the density reproducibility of black level. For example, the black level can be adjusted according to the density of the document, such as making a density of 2.0 or more solid black, or making a density of 1.2 or more solid black. Also, another effect is that
If the circuit constant changes due to temperature and the document density changes, the amount of change is also corrected.

Then, the output of the output control buffer 309 is set to high impedance, and data is read from the offset RAM 311. As described above, the preparation operation for offset correction is completed, and then the preparation processing for shading correction is performed, and reading of the original image is started (steps 606 and 607).

In this state, an image signal representing the original image input from the signal line 255 passes through the D flip-flops 301 and 302, and is input to the adder 303 via the signal line 352. On the other hand, the dark output data is read out from the RAM 311, inverted by the inverter 313, and output from the signal line 3.
56 to the adder 303.

For example, in this embodiment, an 8-bit signal is generated as an image signal, and black is FFI (and white is OOH).
It has been D. Here, when the n-th pixel data in the dark period stored in the RAM 311 has a value of F3H, the adder 303 is given OCR which is inverted data of F3H from the signal line 356.

At the same time, the image signal line 352 shows a black state (F3) (
.

OOH is given in white state. Therefore, adder 303
As a result, the input image signal is FFH for black and O for white.
It is converted into data called CR and sent to the D flip-flop 304 via the signal line 353, and further passed through the signal line 354 and input to the adder 305.

The function of the adder 305 is to add the value set in the flip-flop 307 as described above to the output data of the adder 303. In other words, the image signal is sent from the previous stage as pure black FFH and pure white OCH, but the actual original is
It is not completely black, but has a certain density. Therefore, when using a certain original, if HOH is black on the original,
OFH is added according to instructions from the CPU 212.

Therefore, the black of the original becomes FFH, and a black density corresponding to the original can be obtained. However, adders 305 and 303 will never exceed FFH no matter what addition they perform, and
When exceeding FH, the configuration is such that everything becomes FFH.

As described above, black level offset is performed for each pixel on the read output of the original image.

By the way, in order for the black level offset adjustment described above to work well, the black level adjustment must be within an appropriate range. In other words, if the black level is FFH higher than before the correction, correction is impossible. Furthermore, if the value is extremely smaller than FFH, the dynamic range will be small, the quantization error will be large, and the image quality will deteriorate.

Therefore, the black level before correction is approximately FOH to FE.
It is desirable to adjust to the H range.

The offset adjustment procedure will be explained below with reference to the flowchart in FIG. 5, the operation section in FIG. 6, and the block diagram in FIG. 3.

FIG. 6 is a diagram of the operation unit provided on the top surface of the first illustrated image reading device, and 801 is a key for determining the magnification of the copying machine in the main scanning direction X and the sub-scanning direction Y, and 80
A display 2 numerically displays the magnification in the main scanning direction and the sub-scanning direction. 803 is a copy number display; 804 is a display that displays the density selected by the density key 805; 805 is a numeric keypad for inputting the number of copies, etc.;
07 is a copy key for starting copying.

When the service engineer enters the offset adjustment mode, he inputs the code number using the numeric keypad 806. CPU 212 decodes the code and enters adjustment mode. If it is not confirmed that the optical system is at the home position, the optical system is returned to the home position (steps 701 and 702). Next, the illumination is turned off (step 703), the image selector 308 is set to A, and the address selector 312 is also set to A (step 704). With this operation, black level data from the CCD 103 can be written into the RAM 311. Note that at this time, the CCD 103 is repeatedly performing reading operations, so that the read output of the CCD 103 is sequentially written to the RAM 311.

Next, set selectors 308 and 312 to B (step 7
06) Through this operation, the RAM 311 becomes accessible to the CPU 212.

The CPU 212 calculates the average value Ve of even pixels and the average value VO of odd pixels from the data written in the RAM 311 (steps 707 and 708), and displays them on the display 802 for displaying the aforementioned magnification ratio (step 707, 708). 7
09,710).

Repeat the above steps until the adjustment mode end key (for example, stop key) is pressed. By doing so, CCD10
3 repeats the reading operation, so the black levels for the 103 even and odd pixels of the CCD in each reading scan are displayed in real time.

The service person can adjust the volume 280 while reading the value displayed in real time, and set the black level output of the CCD 103 to the above-mentioned optimum offset value.

Furthermore, if the gains of the amplifiers 281a and 281b are not adjusted to appropriate values, quantization errors will increase, leading to deterioration in image quality. Therefore, after adjusting the offset, the service person enters a code using the numeric keypad 806 to enter the gain adjustment mode.

In this case, if it is determined in step 720 that gain adjustment has been selected, the illumination is turned on, and the display is repeated in accordance with steps 704 to 710 described above. The serviceman corrects the gains of the amplifiers 281a and 281b by adjusting the volume 282 while looking at the display.

In the embodiment described above, the average value for each system is displayed, but the display is not limited to the average value, and necessary data such as peak values may be displayed.

Further, although a magnification display is used as the display means, the same effect can be obtained with any other display capable of displaying information such as displaying the number of sheets.

In addition to entering the adjustment mode by inputting a code using the numeric keypad, a dedicated mode switch may be provided to select the adjustment mode.

Further, when obtaining the black level, the configuration may be such that the illumination is turned on and the CCD 103 reads the reference member for the black level.

〔effect〕

As described above, according to the present invention, it is possible to monitor image reading signals without providing a measuring device such as an oscilloscope, and thereby a good reading output can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the image reading device, Fig. 2 is a circuit block diagram related to image signal processing, Fig. 3 is a block diagram of the offset correction circuit, Fig. 4 is a detailed diagram of the image signal processing section, and Fig. 5 6 is a flowchart showing the control procedure in the adjustment mode, FIG. 6 is an external view of the operation unit, and FIG. 7 is a flowchart showing the image reading procedure, 103 is a COD, 203 is an amplifier, and 204 is an A/D converter. , 205 is an offset correction circuit, and 212 is a CIJJ.

Claims (3)

[Claims] (1) A device that forms an image on a light receiving means and converts it into an electrical signal, including a first means for amplifying or level shifting the output of the light receiving means, and A/D converting the output from the first means. It has a second means, a storage means for storing the digitized signal, and a display means for displaying a numerical value based on the stored signal, and further adjusts the amplification factor or shift amount of the first means. An image reading device comprising: an adjusting means. (2) The image reading device according to claim (1), wherein the light receiving means has a plurality of output systems, and has a first means for each output system. (3) The image reading device according to claim (2), wherein the display means displays numerical values for each of the outputs of a plurality of systems.