JPS61220562A - Picture input device - Google Patents

Abstract

PURPOSE:To obtain a stable and accurate gradation reproducibility and to attain processings responding to the varied density ranges of the input pictures by re-converting the digital signal to one with values in linear relation with the density after A/D converting the input picture signal. CONSTITUTION:The N-bit digital signal which is the output from an input conversion part 5, is supplied to a RAM 6 as an address signal. In respective addresses of the RAM 6, M-bit digital data (where M is intiger of N>M) that direct the values calculated based on desired equations against the density of picture are stored in advance. The said data are respectively outputted using the said address signal inputted, and supplied to a picture processor 7. Meanwhile, a CPU 9, in accordance with the program stored in a memory 10 and the data (specific data in linear relation) inputted from a keyboard 11, stores the said M-bit digital data in the address of the RAM 6 specified by the output from an address generating circuit 8.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) This invention relates to GEL and an image input device, in particular,
The present invention relates to an image input device that converts an optically read image of an object into a digital signal and outputs the digital signal to an image processing device.

(Prior art and its problems) In the image input device used as the input section of any image processing device, such as a facsimile or plate-making screen, photomultiplier tubes, photodiodes, CCI') 'J', etc. It is customary to read images photoelectrically using a photoelectric conversion element. However, as is well known, the intensity of light that enters the photoelectric conversion element from the input image is determined by the fA of the image.
'), the level b of the analog electrical signal that is the output of the photoelectric conversion element is an exponential function of the concentration, and the signal is not proportional to the hot stone in the image. 1. For this reason, in the past, in order to facilitate processing within the image processing device and increase the so-called reproduction f1, the analog 1 output signal of the L light distribution electric conversion element was sent to the analog output amplifier 4f. J, logarithmic transformation was performed, and the value of the original image was set to 1 to obtain an output signal having a linear relationship.

A circuit using such an analog amplifier has a ratio of
3- It is relatively simple, and when using, for example, an operational amplifier (so-called OG amplifier) that performs the logarithmic conversion, there is an advantage that it can be constructed using one operational amplifier and a diode.

However, when these analog operational amplifiers are constructed using semiconductor IC circuits, they are not suitable for high-speed processing due to poor frequency response, and the characteristics of the operational amplifiers are affected by concentration drift 1~ etc. There is a problem in that accurate reproduction of gradation is difficult due to instability. In general, circuits using analog elements are complicated to adjust,
(b) Productivity is also low.

In addition, in such devices, conversion is performed with the same characteristics regardless of whether the m degree range (a degree range) of the input image is wide or narrow, so images with narrow density ranges cannot be processed without image processing. Another drawback is that a clear image cannot be obtained unless some processing is performed on the device side.

(Objective of the Invention) The present invention is intended to overcome the above-mentioned problems, and provides an image input device that has stable and high gradation reproducibility, is capable of high-speed processing, and has high productivity. The primary purpose is to

A second object of the present invention is to provide an image input device that can perform input processing depending on the width or narrowness of the density range of an image to be input.

(Means for Solving the Problems) In order to achieve the above-mentioned objects, the image input device according to the present invention has an analog electrical signal obtained by photoelectrically converting light from an image of an object. The A/D conversion means converts the digital signal into a digital signal from 1 to 1 (N is an integer), and converts the digital signal to 1 to 1 (N is an integer) of the image in question. A digital data conversion means for converting into a digital signal [M-pips indicating a value that shows a desired linear relationship with respect to] (M is an integer such that N>M) and outputting the signal to an image processing device; A conversion characteristic that inputs linear relationship specifying data for specifying the desired linear relationship among preset variable linear relationships, and provides the digital data conversion means with a conversion characteristic that corresponds to the desired linear relationship. sex.

(-).

After Δ/D conversion of the analog signal corresponding to the input image, a digital signal that indicates a value that shows a linear relationship with the density is used for the purpose of compensating for nonlinear effects on electrical manufacturing. The linear relationship is not a fixed one, but is obtained by appropriately specifying a variable linear relationship.

However, in this invention, the term "linear relationship" includes a relationship expressed by a linear equation regarding concentration.

(Example) Configuration of an image input device that is an example of the present invention 11
As shown in the figure. In the figure, an original image 1, which is an input object on which an image with a right gradation is recorded, is irradiated with reading light from a reflective light source 2a or a transmitted light source 2b, and reflected or transmitted light from the original image 1 is irradiated with reading light from a reflective light source 2a or a transmitted light source 2b. enters the photoelectric conversion element 3 of this device via an appropriate well-known optical system. This 1aff
The input of the image 1 is performed sequentially along the scanning direction by a well-known scanning circuit (not shown) for each minute pixel of the original image 1.

The image data optically created in this way is 1-
After being converted into a J:C alley log electric signal by the light distribution electric conversion element 3, it is passed through an appropriate amplifier or an intervening device.
The signal is then converted into an N-bit digital signal (N is an integer) in the next stage A/D converter 4.

For convenience of explanation later, the combination of these photoelectric conversion elements 3 and A/T converters 4 will be referred to as an "input conversion section 5."

The N-bit digital signal outputted from this manual converter 5 becomes an address signal for the RAM 6 in the next stage.

Each address of this RAM 6 contains, as will be explained in detail later,
M-bit digital data (M is N>
M (an integer) is stored in advance. and,
An M-bit digital number 8 corresponding to the above-mentioned M-bit digital data is output from the address indicated by the manually entered address signal (N pin 1-digital signal), and this signal becomes the output of this image input device. It is given to the image processing device 7.

On the other hand, the CPU 9 operates according to the data input from the keyboard 11 (linear relationship specifying data) and the data input from the keyboard 11. signal to M-pi] - Deduce and obtain the data that is the basis of conversion to a digital signal (the details will be described later), and send - to the address of RAM 6 specified by J: in the output of address generation circuit 8. This function has the function of pre-storing the data to be instructed by the M-bit digital signal.

First, the input conversion characteristics of the input converter 5 will be explained with reference to FIG. 2. The graph shown in FIG. 2 shows the input image in the first quadrant ■. It shows the relationship between the output of the photoelectric converter 3 and the output of the photoelectric converter 3. As mentioned above, the analog output of this photoelectric conversion element 3 is an exponential function of concentration, but the conversion characteristics of the photoelectric conversion element 3 and the output of this photoelectric conversion element 3 can be measured using an analog linear amplifier (not shown). This exponential function can be expressed by the following equation (1) by also incorporating the gain when amplifying with .

10...(1) 1, -I. o-10 However, the read density is set to be within the range of O≦D≦Do by setting the maximum value of the density reproduction range to D, and lDO is set to D=O [with the value of D]. be. This functional form is indicated by 01 in the figure.

On the other hand, the second quadrant (■) in FIG. 2 shows the output l of the photoelectric conversion element 3.
The relationship between D and the output SN of the A/I) converter 4, that is, the input/output characteristics of the A/1] converter 1 is shown. Among these, the output SN is obtained as an N-bit digital signal as described above. Since the well-known A/D converter 4 has an approximately linear conversion characteristic, its characteristic is directly KA j! It can be expressed in 1. The functional form of this straight line 11 is, ■I,=IDo(?l, that is, I
) = O) at s.

−〇, and ■I = 1 −10'O (that is, D=Do)
It can be obtained from the condition that S -8No at O, and the result is the following (
2) Equation becomes.

SNOID 5N ”” (1O-DO (1-Otsu),,
-(2) is obtained. From this equation (3), the digital signal 51bJ: is non-linear with respect to the density.

Here, suppose that the output of this input converter 5 is processed as is! l'! Let us consider the case where the output is output to the neck attachment 7. Then, as shown in FIG. 3, the N-bit digital signal SN
When the quantization error in is △SN, the density error corresponding to this quantization error ΔSN is a relatively small error 〇o1 in the low density region, but a considerably large error ΔDo2 in the high density region. Put it away. Therefore, −
Data length of N-bit digital signal (i.e. N)
If it is made small, the reproducibility of one-degree gradation in the high-density region will deteriorate, making it impossible to faithfully reproduce delicate gradation changes. On the other hand, if you want to improve gradation reproduction ('l) in a high-density area, you can increase the value of N mentioned above, but if you increase the data length and
It is unrealistic to perform the subsequent image processing in :, considering the fact that the equipment becomes expensive in proportion to the number of bits. If the output of the input conversion section 5 shown in FIG. 2 is directly output to the image processing device 7, the balance between gradation reproducibility and cost becomes difficult.

Therefore, in the present invention, the input conversion unit 5'C'' performs processing with a relatively large data length to ensure gradation reproducibility, and the subsequent image processing device 7 performs processing with a relatively large data length. In addition, digital data is converted so that processing can be performed without losing the reproducibility described above.In other words, R
M-pitch 1 to 5 instructs the N-bit digital signal input to AM6 to have a linear relationship with density.
It is converted into a digital signal QiN>M). The idea of this conversion itself has already been proposed by the inventor of this invention and a patent application was filed on the same date, but in the invention shown here, the idea of this conversion is further advanced, and the basic idea of this conversion is 1 to the value S14 that the digital signal should indicate is varied, and one of them is specified and used as appropriate. -44r In other words, instead of giving such a fixed linear relationship, it is possible to perform conversion with a desired linear relationship.

Therefore, in order to clarify the significance of this variability, below we will discuss the problems that arise when the linear relationship is fixed.
An explanation will be given by taking as an example a case where a linear relationship as shown by 12 is adopted in the fourth quadrant of FIG. To that end, first of all, j!
We will derive a conversion formula to realize the linear relationship of 2. In order to realize these 12 linear relationships, the value SH to be output when the N-bit digital signal is input to the RAM 6 has the following relationship with the density (4). If the data is J: Yes.

5H-8l,.・(1) ・・
・(4) However, Si. is the maximum value of SH corresponding to D-Do.

The input SN of RAM6 is given by equation (3), and the output S
The fact that H should be obtained by equation (4) means that based on the conversion relationship of the following equation (j) obtained by eliminating D from equations (3) and (4), This means that it is sufficient if the t-transformation is achieved.

S = '-'-100(-Ikkaku-1)...(
5) HvO';Ha-8NtX-+o) This functional relationship is shown by C2 in the third quadrant (■) of FIG. I wish I could configure RAM 6 so that whenever SN is input, SH calculated by equation (5) above is output. In other words, the values of S, which have been set in advance based on formula (5), are stored in the addresses (N bits) corresponding to all the values that can be acquired in SN, respectively. Then, using the data content of the input SN as address information, the S8 stored at the address is read out and output. This is one aspect of the so-called look-up table method.

In this way, as shown in FIG. 4, the quantization error ΔSM■ in the M-bit digital signal S is the same depth error ΔD in each region of the density aD. Even if a relatively small 'JM is adopted,
The gradation reproduction ↑ll in the high-density area is ensured.1 This conversion is the density transition of the image to be input, that is, the difference between the highlight 1 part and the side 17 part of the original. If the range is not shown as [) ≦D≦Dmax in Fig. 2 and is relatively wide, the data range of M-bit digital data SH corresponding to this 11I 1 degree range 5IIli in Fig. 2
(Eight) . As shown in ≦SH≦5IIlax, it is a wide range, so there is no problem. However, the density range of the image is +
[i) In the figure, D≦D≦DIIlax indicates that the data range of the digital data SH is S
-≦SH≦”ll1aX, and 1) It is difficult to use only a part of the data SN that covers a wide data range of In O≦SH≦SHo. Therefore, for example, if digital data is used for 8 pixels 1, the gradation of the original image will be expressed by only a part of the number of gradations of C (28 = 256), and it will be linear again. - Even if conversion using Arple is performed, it will not be possible to reproduce a clear 4T reproduced image because the gradation will be distorted.

Therefore, for an image with a narrow density range of 1n, such as D, ≦[)≦U')max, this m degree range is the range of the M-bit digital data S14, as shown by 13 in Fig. 2. It is desirable to use a linear relationship that corresponds to a large portion of 4. However, 1. i! If the conversion data based on the linear relationship described in 3 is fixedly stored in the RAM 6, it would be impossible to use original images with a wide range of electrical production.

Therefore, in this invention, the linear relationship is set to n1 variables, and one of them is configured to be specified as appropriate.

Therefore, in this embodiment, the linear relationship shown in 13 above is expressed as the endpoints (1'), S ), (Dmax
max, S ・) is considered as nJ variant. And ml
n mln The data related to these end points are input from [Linear relationship identification data 1 - C1 from the gear board 11 in FIG.
, U) Take in each value of SN corresponding to lIllo, and based on this, pass through these two end points =
15 = The conversion data based on the functional form of the straight line is converted into CPtJ
Calculate with 9. The formula for providing this conversion data can be obtained as follows.

First, the above equations (1) to (3) obtained based on the function forms C and 11 in FIG. 2 hold true as they are.

The equation corresponding to equation (4) is a square rod equation of a straight line passing through the above two end points, and is the following equation (6).

(S-8・)・(D-1')111. ,)
Hmln maX = (S -8,), (D-DIll, o) - (6
)+11aX m1n By eliminating D from equations (3) and (6), the following equation (7) is obtained.

...(7) However, △D-1')n+ax'min
...(8) ΔS=S −S,
...(9) maX l1lln Δ(SD) -8, D -8D ・mln
1IlaX maX mln...(
10). The functional form expressed by equation (7) is shown at C3C in FIG. Therefore, the variable conversion relationship according to equation (7) is expressed as D, ,D,Sm1o.

By specifying the values of n1ln n1aX and S, J can be specified by specifying a specific max and converting accordingly. According to this method, the amount of change in S with respect to a constant change in depth 1η is always constant, so that it is possible to prevent gradations from changing.

61 In this case, 0≦D≦D4, and D
〈[)≦l) The problem is 11aX conversion where there is one in the range o. Regarding this, see al. in FIG. 6, for example.

Conversion to limit 1 as shown in a, or J as shown in b and b2
: U/i Booth 1 It's okay to convert your hair to ().

There are 43 in some parts of Hirai I, and the al is for letterpress, and the bl is for letterpress.
are respectively suitable as printing characteristics for offlets.

Next, based on the above knowledge, the operation of the embodiment shown in FIG. 1 will be explained to the extent that it does not overlap with the above explanation. first,
D, , D , Sm, oJJ and Sman
Using max max as a parameter, calculate the above equation (7) with IQ?
A program for reading is stored in the memory 10.

Then, the operator determines the density range of the original image 1 to be input and the data range of the data S8 to be output corresponding to the range using the above D.
maX. Enter the value of J: and Smax from the keyboard 11. The CPU 9 stores these data and the memory 10.
Based on the programs installed in 1 to 1, the formula (7) is specifically specified, and all possible values of SN, X, X2, etc. are determined. . . . Expression (7) is calculated for . When this calculation result is obtained, CP LJ 9 is RA
A write signal is applied to the read/write selection signal input pin R/W of M6, and through the address generation circuit 8,
An N-bit address signal corresponding to each value of the N-bit digital data SN is generated and applied to the address section of the RAM 6. Then, to the address above (
7) Store Si4, which is the calculation result according to the formula, in each of the M pins I~. An example of this storage relationship is shown in Figure 5, where the functional form of the right side of equation (7) above is f' (SN
), then M-pi digital data f(x), 1 "(
X2)... are all squared.

When this writing is completed, the CPU 9 sends a read signal to the RAM 6. When the original image 1 is input and input is started, the N-bit digital signal after A/r)e conversion is given to the address section of RAM 6, and the M-bit digital data corresponding to that value is stored in memory 6. is output from. When this processing for each scanning direction is completed, the image processing for one original image is completed. The next time you want to read an original image with a different density range, input the above values, I), S-, and 5II18x again at point A, and
n maX mlnSimilar calculations, storage, and reading are performed accordingly.
.

To give an example of the accuracy in this embodiment, we can trace N=12 pitches to 1M-8 pitches to D. -2,
7, and the linear relationship specific data U, l) min −
0,2,D-0,8,5IIl,. = O (converted to the output halftone area ratio in the case of manufacturing ma× plate width 1ν) is 0%
), S max = 255 (100%), this image can be expressed with 230 gradations at a halftone area ratio of 5% to 95%. This is a significant increase in the number of gradations compared to 57 gradations when β2 in FIG. 2 is fixedly adopted as a linear relationship. Therefore, it can be seen that in addition to the performance improvement achieved by performing conversion based on a linear relationship, the effects of making this linear relationship variable and performing conversion in consideration of the range of the density distribution of the original image are enhanced.

Further, by employing the look-up table method described above, it is possible to increase the speed, and since digital processing is used, productivity and stability are high.

Next, other aspects of the invention will be described. First, in the above embodiment, it is assumed that the output characteristic with respect to the concentration of the input conversion section 5 is a function form that can be accepted by equation (3), but if the linearity of the photoelectric conversion element is poor, this function form is unchanged. There may be cases where it is not possible to adopt. In such a case, the function form representing the output characteristics of the input converter 5 is
Obtain the functional form of knee 1, which is an inverse function of this function F(D), using N-F(D) as a decoy. Then, the relationship D=F (SN) is obtained. Therefore, the input/output relationship in the digital data conversion means is defined as S −k F (2 for sN>+...
(12) (where k and 2 are constants determined by the linear relationship specific data), these formulas% formula%
(13) Therefore, transformation by a variable linear relationship is achieved according to the linear relationship specification data.

Next, in cases such as general facsimile machines, where ease of operation is required but the gradation reproducibility of the reproduced image is not very high, the present invention can be applied as follows. can be realized. [In other words, limit the density range of the original image to be input to several types, derive linear relationships for each density range, and convert each of these linear relationships. Data is computed in advance and the computed results are stored separately in multiple memory locations or in different areas of large-capacity memory. In this case, a simple selection switch etc. is used as the "conversion characteristic specifying means", and depending on the selection of this selection switch, U, N
The memory inputting the bit digital signal is switched and selected, and the M-bit digital data stored in the selected memory is output.3 In this case, the variable range of the linear relationship is the same as the above several types. It turns out that. [Variability 1] is a term that also includes such discrete variability.

In addition, the conversion formula shown in equation (5) above only causes a problem when it is used fixedly, and is one of the variable linear relationships in this invention. There is no problem in including the transformation based on this formula (5) as a form. In fact, in the above equation (7),
When overriding as DIIllo-O9DIIlax-Do, (7
) is easily confirmed to be equation (5), and it can be seen that equation (7) also includes equation (5). Furthermore, regardless of the meaning of the subscripts "min" and "max" with f=J in the symbol, data such as 1]l11ax<D may be used. In this case, +111n is an example of -C.For example, DIIlax-0, [)lI
llo-D. In other words, the equation (7) becomes the 16th order equation (14) corresponding to the 41 linear relationship as shown by f14 in FIG.

When this relationship is specified, within this image input device,
I decided to move the negative/positive conversion to line b.

The present invention, which has the above-mentioned characteristics, can be used as any human-powered device, such as facsimiles, plate-making scanners, and television image processing. After manually inputting the above M-pitch 1 digital signal, the gradation level fl can be changed using an arbitrary look-up table.
There is υpossible C.

(Effects of the Invention) As explained above, according to the present invention, since the read image data is converted into a digital signal that indicates the value that increases the density by 1 and has a linear relationship, Key l■
In addition, it is possible to obtain an image processing device that is capable of 8-speed processing and has improved productivity. Furthermore, since this device allows input to be made in accordance with the nature of the image to be input, it has the advantage of being able to obtain a clear image regardless of the image's dark/white range.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.
Figures 2 and 6 are J graphs showing characteristic examples of the device in Figure 1, Figure 3 is a graph showing the characteristics of the comparative example, Figure 4 is a graph showing the characteristics of the reference example, and Figure 5 is a graph showing the characteristics of the comparative example. FIG. 7 is a graph showing the data storage contents of the memory used in the device of FIG. 1, and FIG. 7 is a graph showing the characteristic v1 of a modified example. 1... Original picture, 3... Photoelectric conversion element, 4...
・A/D converter, 5... input horn conversion section, 6... RA
M, 7... Image processing device 8... Address generation circuit, 9... CPU, IO... Memory, 11.
··keyboard

Claims (3)

[Claims] (1) An image input device for photoelectrically reading and inputting an image of an object and outputting a signal representing the image to an image processing device, the image inputting device photoelectrically reading the image and inputting the image to an image processing device. photoelectric conversion means for converting the analog signal into an analog signal; analog/digital conversion means for converting the analog signal into an N-bit digital signal; and converting the N-bit digital signal into a desired linear relationship with respect to the density of the image. digital data converting means for converting a value into an M-bit digital signal indicating a value and outputting the M-bit digital signal to the image processing device; a conversion characteristic specifying means for inputting linear relationship specifying data for specifying the desired linear relationship and giving the digital data converting means a conversion characteristic according to the desired linear relationship, where the N and M are N An image input device that is an integer that satisfies >M. (2) The linear relationship specification data includes two density values D_m_i_n and D_m_a_x that indicate the end points of the density range of the image.
and two values S_m_i_n, S_m_a_x that indicate the end points of the range of values to be indicated by the M-bit digital signal.
and the digital data conversion means includes the D_m_i
_n, D_m_a_x, S_m_i_n and S_m_
The following formula (a) determined by a_x: S_M=1/ΔD[Δ(SD) +ΔSlog{S_N_0/S_N_0−S_N(1−
10^-^D^0)}...(a) where D is the density of the image, D_0 is the maximum reproduced density, and S_N is the N-bit digital signal. S_M is a value to be instructed by the M-bit digital signal corresponding to the S_N, S_N_0 is the S_N corresponding to the D_0, and ΔD
=D_m_a_x−D_m_i_n, and ΔS=S_
m_a_x−S_m_i_n, and Δ(SD)=S_
m_i_nD_m_a_x-S_m_a_xD_m_i
_n. The image input device according to claim 1. (3) The conversion characteristic specifying means includes a calculation means for inputting data representing each of D_m_i_n, D_m_a_x, S_m_i_n, and S_m_a_x and performing calculations based on equation (a), and the digital data conversion means includes: Based on the output of
3. The image input device according to claim 2, further comprising storage means for reading S_M from an address corresponding to the value of S_N indicated by the bit digital signal and outputting it as an M-bit digital signal.