CN1155710A - Controlling circuit for image reading - Google Patents

Abstract

An image reading control circuit is aimed at that the white balance compensation and black level compensation of image reader can be individually regulated as well without any association. It is composed of at least one addition/substraction circuit of the first current for clamping black signal level to "0" level and at least one addition/subtraction circuit of the second current for processing phase difference of black signal level. When reading image, each signal is generated from the above mentioned circuits and inputted to A/D converter to control the white balance compensation.

Description

Controlling circuit for image reading

The invention relates to controlling circuit for image reading, especially about being applicable to the controlling circuit for image reading of the image information that reads colored original.In the past on controlling circuit for image reading, be to utilize indivedual imaging apparatuss the reflected light of light source irradiation to the original copy, transmitted light light-to-current inversion in addition, again with after the A/D converter digitizing, be used as digital image data and read.Therefore, on traditional controlling circuit for image reading, in order to consider the input dynamic range of A/D converter, and use the method that the white level of color signal and black level are lumped together, but, therefore there is a mutual relationship between white level (level) and the black level (level), if promptly change white balance revisal yield value, the situation that also can cause black level and then to change.

For example open clear 62-115963 Japanese patent gazette the dynamic range that comes out with out relevant controlling loop adjustment A/D converter is arranged the spy, it is made the genealogy of law and will earlier the leading portion of white balance revisal part read back to the strangulation loop before the black level input a/d converter, but practice result produced the loop configuration maximization and for by analogy fixing, can't change the problem of doing trim process arbitrarily.And, owing to black level must be read back, in case the gain of change white balance revisal promptly can produce the also related affected problem of black level.

In view of this, the objective of the invention is to make white balance revisal and black level revisal not have mutual relationship and provide a kind of, and can feel free to do the controlling circuit for image reading of adjustment in order to solve aforesaid problems of the prior art.

Controlling circuit for image reading of the present invention, tie up in provide one at light source irradiation in scanned transmitted light, or the black level signal of the color signal that reflected light produced is when being fixed on certain level (strangulation), white balance in the aforementioned color signal of revisal, and aforementioned by the signal after the revisal white balance, see through the controlling circuit for image reading of A/D converter with image data output, this controlling circuit for image reading comprises:

Being used for the aforementioned black level signal of strangulation and calculating the loop at the 1st electric current plus-minus of 0 current potential, is to use the outside of white balance gains to adjust the gain that signal (SW) is controlled white balance changeably; Being used for the black level signal potential difference and handling, promptly done the 2nd electric current plus-minus calculation loop that the direct current potential difference is handled to aforementioned by the black level signal after the strangulation, is to utilize the outside signal (Sb) of adjusting of black level, controls the numerical value that aforementioned black level signal potential difference is handled gained changeably;

Aforementioned controlling circuit for image reading mainly is to sum up each signal that the 1st electric current plus-minus is calculated the 2nd electric current plus-minus calculation loop of loop, the processing of black level signal potential difference, make its input a/d converter, and suitably control the revisal of aforesaid white balance, particularly R-2R ladder network resistance comes combine digital control, and adjusts signal, the outside signal of adjusting of black level by the digital control outside of successfully controlling aforementioned white balance gains.

So just, can make white balance revisal, black level adjustment, black level reference value subtract calculation, concentrating on circuit entirely adds and subtracts on the input point of an amplifier calculating the loop, between white balance and the black level revisal also because of no mutual relationship, but and independent variation, even also might needn't consider black level, and the white balance revisal is changed arbitrarily.Then as previously mentioned, characteristic of the present invention can be carried out good D/A conversion promptly because of the control of R-2R ladder network resistance, and is multiple because of numerically controlled result, effectively utilized the dynamic range of A/D converter.

Below with reference to embodiment and more specifically describe the present invention with reference to the accompanying drawings.

Brief Description Of Drawings:

Fig. 1 is the module pie graph of the image scanner that is suitable for of the present invention;

Fig. 2 is the block scheme according to controlling circuit for image reading of the present invention;

Fig. 3 is the output signal of the position that arrow A indicated of Fig. 2;

Fig. 4 is the output signal of the position that arrow B indicated of Fig. 2;

Fig. 1 is the module figure that the demonstration image scanner summary that the present invention was suitable for constitutes.This image scanner is provided with the original copy platform 2 on square frame 1; The scanister 3 that is constituted with lamp 4, eyeglass 5 by reflection original copy platform 2 times; See through lamp 6 on the original copy platform 2; The movable lens group 7 relative with eyeglass 5 wherein still comprises pair of lenses 7a, and 7b reflexes to and described laterly is subjected to pixel spare so that its direction parallel with original copy platform 2 penetrates and the eyeglass 5 of scanister 3 will expose to the light of scanister 3.The eyeglass 7b of movable lens group 7 accepts the image from scanister 3, and the components of photo-electric conversion on the other side 9 are made of CCD, are located at the lens group 8 between the eyeglass 7b and the components of photo-electric conversion 9, the function of the line density of the tool conversion components of photo-electric conversion 9.

See through scanister 3, movable lens group 7, lens group 8 and, export image process unit 10 to from original copy platform 2, promptly output to the outside after the wherethrough reason again by the image that the components of photo-electric conversion 9 receive.Wherein, the control of scanister 3, movable lens group 7, lens group 8 and image process unit 10 is all reached by controller 11.

The voltage of the signal of video signal of the components of photo-electric conversion 9 outputs changes by changing with light quantity, after this signal of video signal exports image process unit 10 to, is handled via controlling circuit for image reading shown in Figure 2, promptly outputs to the external treatment device as image data.Via the signal of video signal of being exported after the components of photo-electric conversion 9 conversions, pixel (pixels) quantity required with constituting signal of video signal is identical, and,, be illustrated at one of them treatment scheme hereinafter with reference to Fig. 2 because of each Signal Processing process is all identical.

As shown in Figure 2, from the color signal of components of photo-electric conversion output at the 1st section amplifier 12 after buffered, i.e. input can be carried out the CDS loop 13 of correlated double sampling (correlateddoublesa-mpling), CDS loop 13 processes at the image level of signal of video signal, imports the black level strangulation loop 14 of the 2nd section amplifier again and does the strangulation processing.And via the processing in black level strangulation loop 14, to earth potential, the signal of gained is presented at Fig. 3 to the signal level of shading light part (opticalback) after the operational processes according to this with strangulation.As shown in Figure 3, the signal of arrow A indication place among Fig. 2 is to handle the output that the back is produced by 2500 picture elements via aforementioned process, and this signal system exports with the negative direction below the 0V.

Aforesaid negative direction output signal, then import the R-2R loop 15 that is constituted by a R-2R ladder network resistance, in order to carry out the function of tool white balance revisal, the signal of 15 outputs then is transfused to anti-phase amplifying return circuit 16 as negative input end from the 1st R-2R loop.And the positive input terminal of anti-phase amplifying return circuit 16 is grounded processing, then delivers to A/D converter 17 as for the output signal of anti-phase amplifying return circuit 16 and handles.

Negative input end of foregoing anti-phase amplifying return circuit 16 is imported and is added the reference voltage of using reference voltage source 19 from the 9V signal after the 2nd R-2R loop 18 produces output signal.Wherein the 2nd R-2R loop 18 is that R-2R ladder network resistance by tool black level correcting function is constituted, its voltage then by+2V with reference voltage source 20 supplies ,+9V potentiometer signal with reference voltage source 19 then be near the A/D input dynamic range (10V～+ the black level signal direct current potential difference disposal route of 10V) lowest order.With aforementioned output signal after handle in the 2nd R-2R loop 18, add according to the outside signal Sb of adjustment of the black level of 8 bits so that export variable voltage signal, be mixed in reference voltage with+9V signal again, just black level can be adjusted in the dynamic range of-10V ± 1V.In addition, the variation adjustment of signal amplitude decay then can be reached by the outside signal Sw that adjusts of the white balance of 8 bits of transporting to the 1st R-2R loop 15.

As for the lead-out terminal of anti-phase amplifying return circuit 16 and the end points between the negative output terminal, then see through resistance R x and+the 9V potentiometer signal continuing with reference voltage source 19, at present embodiment, resistance R x is set at 91k Ω, voltage Ry is set at 3k Ω ,+9V signal with 19 of reference voltages should produce+9 * Ry/Rx+output of the potential difference of 0.3V.

As shown in Figure 4, the output signal of the indicated counter-rotating amplifying return circuit 16 of arrow B in Fig. 2, system utilizes the signal amplitude gain of the white balance revisal in the 1st R-2R loop 15, can't be subjected in its processing procedure the 2nd R-2R loop 18 or+influence that 9V adds, and can change the white balance compensating value arbitrarily.The output form of aforementioned output signal is as shown in Fig. 4.And according to the present invention, in case must change white steadily compensating value because of the change of factors such as reading conditions the time, need only change the input of transporting to first R-2R loop 15 to adjust signal Sw and get final product, and need not do the adjustment of black level.Accurate this, can change arbitrarily under the situation of black level, white balance also can not change because of the generation of no mutual relationship thereupon.Control by the numerical data of 8 bits as for the 1st the R-2R loop 15 that CPU controlled and the adjustment data in the 2nd R-2R loop 18.

After signal of video signal is handled via aforementioned process, the white balance revisal will cooperate A/D converter 17 to do the adjustment of input dynamic range, and it is set in dynamic range in the scope that can effectively use, and with the form output image signal of numerical data.And the data of A/D conversion gained will be feedback to the digitial controller in the 1st R-2R loop 15 and the 2nd R-2R loop 18 after CPU makes a decision.

As preceding announcement, if utilize the present invention, then will can adjust for changing arbitrarily because of no mutual relationship between white balance revisal and black level revisal, it can make black level continue to maintain earth potential, and only any variation is done in the gain of white balance revisal, or be under the situation that does not influence the white balance revisal, to change black level arbitrarily.In addition, the present invention still can utilize the digital control dynamic range of using A/D converter effectively, particularly because utilize the control of R-2R ladder network resistance, can successfully carry out the A/D conversion, control is easy, the loop is simple constructs to implement very good image data processing capacity and reach.Therefore, the present invention one has value new invention on the industry.

For this reason, the various modifications that those skilled in the art have done according to the present invention, the protection domain of neither disengaging claim of the present invention.

Claims (3)

1, a kind of controlling circuit for image reading, transmitted light by original copy after at light source irradiation or catoptrical color signal black level are in addition in the strangulation, white balance in the color signal of revisal scanning back, and, see through A/D converter and export with image data with the color signal of gained after the revisal; This control loop contains: being used for the aforementioned black level signal of strangulation and calculating the loop at least one the 1st electric current plus-minus of 0 current potential, is to use the outside of white balance gains to adjust the gain of the variable control white balance of signal;

Being used for the black level signal potential difference handles, promptly done at least one the 2nd electric current plus-minus calculation loop that the direct current potential difference is handled by the black level signal after the strangulation to aforementioned, system utilizes the outside signal of adjusting of black level, controls the numerical value of black level signal gained after the direct current potential difference is handled changeably;

It is characterized in that when described control loop reads at the control image, calculate the loop via the 1st electric current plus-minus, the 2nd electric current that the black level signal potential difference is handled is added and subtracted each signal of calculating the loop and producing, makes its input a/d converter, with the revisal of control white balance.

2, controlling circuit for image reading as claimed in claim 1 is characterized in that, reaches the outside of control white balance gains with digital control and adjusts signal and the outside signal of adjusting of black level.

3, controlling circuit for image reading as claimed in claim 2 is characterized in that, uses R-2R ladder network resistance to be used for digital control.

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