JPS60206369A - Picture signal correcting system - Google Patents

Abstract

PURPOSE:To correct electrically the long-term variation of a shading waveform and also the short-term light quantity variation of a light source by executing a shading correction by inputting a picture signal and the output of a storage device to an arithmetic ROM, and subsequently, executing a level correction by inputting an output picture signal from this arithmetic ROM and an output signal of a reference level detecting circuit to this arithmetic ROM again. CONSTITUTION:Immediately before inserting an original 1, a white level is read by a photoelectric converting element 4 through a lens 2 from a back roller (not shown in the figure), and stored as a shading waveform in a RAM7 through an A/D converter 6. A picture signal is inputted to an arithmetic ROM14 through the A/D converter 6, a selector 8, and a latch 10; and a shading correction is executed. Also, it is applied to a reference level detecting circuit 15 through a latch 12, and a calculation is executed, the white level of the original is corrected and it is outputted to the outside.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an image signal correction method when an image signal is obtained from a photoelectric converter in a facsimile or the like.

[Technical background of the invention]

Conventionally, in facsimiles and the like, reflected light from a document is focused by a lens and imaged on the light receiving surface of a photoelectric conversion element, and an image signal is obtained from this photoelectric conversion element. The level of the image signal at the center of the document is higher than the level at the periphery, causing so-called shading distortion.

For this reason, conventionally, as shown in FIG.
By inserting a plate called a shading plate 3 between the photoelectric conversion element 4 and limiting the transmitted light f in the central part, the photoelectric conversion element 4
Correction was made so that the amount of light on the light receiving surface of the sensor was uniform.

Note that 5 is a light source that illuminates the original 1.

[Problems with background technology]

However, in such a conventional image signal correction method, it is necessary to adjust the shading plate 3 for each machine in order to correct deviations in the characteristics of the lens 2 and deviations in the light intensity distribution of the light source 5. Fine bit-by-bit correction of image signals is not possible. Further, the glaze has the disadvantage that it cannot follow long-term changes in the shading waveform due to deterioration of the light source 5 or the like.

Furthermore, immediately after the light source 50 is ignited, there is a large change in the amount of light due to a change in the temperature of the light source 5, so the amount of light reflected from the original 1 changes while the original 1 is being read, so it is necessary to deal with such changes in the amount of light. It was also necessary to provide correction means.

[Purpose of the invention]

The present invention has been made in view of the above points, and provides an image signal correction method that can electrically correct not only shading waveform correction, but also long-term changes in shading waveforms and short-term changes in light intensity of a light source. The purpose is to

[Summary of the invention]

Therefore, the present invention includes a memory (RAM or ROM) that stores the shading waveform of the image signal, a reference level detection circuit that detects and stores the reference level in the image signal, and a correction calculation ft0M. The signal and the output of the memory are input to the calculation ROM, shading correction is performed, and the following (
The above object has been achieved by a correction method in which level correction is performed by inputting the output image signal from the arithmetic ROM and the output signal of the reference level detection circuit back into the arithmetic ROM.

[Embodiments of the invention]

FIG. 2 is a block diagram showing an embodiment of the image signal correction circuit applied to the present invention, in which 6 is an A/D converter, 7 is a RAM for storing shading waveforms, 8
and 9 is a selector, lO.

Reference numerals 11, 128 and 13 are flip-flop latches, 14 is an arithmetic ROM, 15 is a reference level detection circuit that detects and stores the reference level of the image signal, and 16 is a counter.

In the above configuration, first, just before inserting the original 1 (3), the white level is removed from the back roller (not shown) via the lens 2 by the photoelectric conversion element 4, and then transferred to the RAM 7 via the M/D converter 6. , and store it as a shading waveform.

This shading waveform is shown as the curve in FIG. 3(a). In addition, in the arithmetic ROM 14, the upper 6 bits of the address are set as M and the lower 6 bits are set as M/B.
The calculation result of X32 is committed. Next, the original 1 is inserted, and an image signal shown by the curve P in FIG. 3 (IL) is obtained from the photoelectric conversion element 4. Operation ROM14 via
is input. In addition, the shading waveform t hail output signal successively outputted from the RAM 7 is sent to the 1 selector 9 and the latch 1.
1 to the calculation ROM 14,
In this step, a calculation of (image signal)/(RAM output signal)×32 is performed. Through this calculation, shading correction is performed, and the first output of the calculation ROM 14 becomes uniform with shading distortion removed, as shown in FIG. 3 (1'). This calculation (4) The first output of ROM14 is selector 8, latch 1
It is again input to the calculation ROM 14 via 0t'. Further, the first output of the calculation ROM 14 is applied to the reference level detection circuit 15 via the latch 12, and the output from the reference level detection circuit 15 is outputted from the calculation ROM 14 as shown in FIG. The output signal that sets the reference level of the first output of
is input to the arithmetic ROM 14, and in the arithmetic ROM 14 (
Calculation 6 of the first output of the calculation ROM 14)/(output of the reference level detection circuit 15)×32 is performed. As a result of this second calculation, as shown in FIG.
The signal is obtained from the OM 14 and output to the outside via the latch 131.

FIG. 4 shows a timing chart 1 for the operation of the circuit shown in FIG. 2. FIG. 4(a) shows the output image signal of the MU/D converter 6, and FIG. 4(0) shows the operation of latch to, 11's operation Y:%, FIG. 4(d) shows the address of operation ROM 14, and FIG. 4(-) shows operation RO.
The outputs of M14 are shown respectively.

Selectors 8 and 9 divide the length of one pixel into two, and select the first half by tBY. Note that A and B indicate the case of shading correction, and AIB indicates the case of level correction.
After being delayed by one pixel by latches 10 and 11, A and B become the latter half addresses of the calculation ROMI 4. The calculation result A of M/BX32 is obtained from the calculation ROM 14 by the first calculation.
' is output. When the output A' of the arithmetic ROM 14 is input, the reference level detection circuit 15 stores the maximum A' within a predetermined range as the reference level B'. B' corresponds to the white level of the original, and changes in B' correspond to short-term changes in the amount of light from the light source.

When the selectors 8 and 9 select M' and B', the latches 10 and 11 delay the data by one pixel, and then the operation ROM 1
This will be the first half address of 4. Performed by the second operation,
3! The ROM 14 outputs the calculation result C of A'/B'X32, and this O is outputted to the outside via the latch 13 as a corrected image signal.

In this case, the latch 12 selects A of the output of the arithmetic ROM 14.
'Y, the latch 13 is a of the output of the calculation ROM 14
y are worth keeping.

As is clear from the above explanation, in the image signal correction method according to the present invention, since the calculation ROM 14'l is used twice, a single operation ROM 14 is used to perform shading correction, light intensity change of the light source, and The white level of the original can be corrected.

〔Effect of the invention〕

According to the image signal correction method according to the present invention, since the shading plate 3 is not required, the shading plate 3 is provided for each machine.
This method not only eliminates the drawback of the conventional image signal correction method that requires adjustment of
Fine bit-by-bit correction becomes possible. In addition, even if there is a long-term change in light intensity due to deterioration of the light source 5, the shading waveform Y [takes] K changes every time a document is inserted.
It is possible to correct long-term shading waveform changes. Furthermore, there is an advantage that short-term changes in the amount of light (7) and the white level of the document can be corrected using a single calculation ROM 14.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the conventional shading correction method, Figure 2
The figure is a block diagram of an image signal correction circuit applied to the present invention.
Figures 3 (a) to (d) are waveform diagrams of each part, Figure 4 (a)
) to (e) are timing charts. l... Original, 2... Lens, 3... Shading board, 4... Photoelectric conversion element, 5... Light source, 6...
RAM/D converter, 7...RAM, 8.9...Selector, 10,11゜12.13...Latch, 14...
・Arithmetic ROM, l 5...Reference level detection circuit, 1
6...Counter (8)

Claims (1)

[Claims] A memory device that stores the shading waveform of the image signal output from the photoelectric conversion element, a reference level detection circuit that detects and stores the reference level of the input image signal, and performance J! R.O.
M, and the image signal output from the photoelectric conversion element and the output signal successively output from the memory are stored in the arithmetic ROM.
, performs the operation JT, obtains the first output signal that has been subjected to shading correction from the calculation ROM, and then obtains the first output signal ? applying the signal to the reference level detection circuit to obtain a reference level detection signal of the first output signal, and inputting the detection signal and the first output signal to the calculation ROM to perform calculation. Accordingly, the operation R
An image signal correction method characterized in that a second output signal subjected to shading correction and level correction is obtained from an OM.