JPH05145760A - Image reader - Google Patents

Abstract

PURPOSE:To obtain a copy whose gradation characteristic is satisfactory even from any film of negative/positive by selecting an optimal gamma curve, and also, varying the quantity of light of alight source. CONSTITUTION:An enlarged projection image of a microfilm exposed by a light source 9 is subjected to image scan, fetched as a serial image signal in an analog value from an image sensor 1 by line synchronization, and inputted to an A/D converter 3 through an amplifier 2. Simultaneously, an offset voltage is also adjusted. Subsequently, the signal is made to an 8-bit digital signal, and is inputted to a gamma a correcting circuit 4 constituted of several pieces of RROMs. In this PROM, a gamma characteristic curve is stored by data measured in advance, and selected in accordance with base density by an SEL signal from a control part 11. Also, simultaneously, light quantity data EN/EP of light source light quantity control is also stored, read out and inputted to a light source driving part 10. A signal of an edge emphasizing circuit 5 is subjected to pseudo halftone processing and simple binarization processing by a halftone processing circuit 6 and a binarizing circuit 8, and the gradation characteristic is improved.

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 for performing digital image processing, and more particularly to an image exposed by a light source.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital scanner for reading digital images by a D image sensor or the like, or an image reading device for reading images such as characters and photographs in a digital copying machine.

[0002]

2. Description of the Related Art An image such as a character or a picture written on a book, a document or the like, or an image such as a character or a drawing recorded on a microfilm or the like is read by using a CCD image sensor to display the image. Processings such as obtaining an image signal, recording an image on the basis of the image signal, and transmitting the image signal are performed.

For example, an apparatus for reading an image on a microfilm photoelectrically converts the projection light from the film by a CCD, an image sensor or the like, reads the image, performs electrical image processing, and the like, and then, LBP (laser beam printer).
It is known as a so-called digital reader printer that obtains a copy by sending a digital signal to the printer.

FIG. 14 shows a block diagram of an image reading apparatus used in such a reader printer.

Image pickup unit 21 using an image pickup device such as a CCD
For example, the reflected light from the original placed on the original table,
Alternatively, it is photoelectrically converted while scanning the projection light of the microfilm, and is further multivalued quantized by the A / D converter 22. The multi-value quantized data is corrected by the following γ correction unit 29 to correct the difference between the photoelectric conversion characteristic of the image pickup device such as the CCD in the image pickup unit 21 and the human gradation visual recognition characteristic. This situation is shown in Figure 1.
5, FIG. 16 and FIG.

FIG. 15 shows an example of the photoelectric conversion characteristics of the image pickup device, and the horizontal axis is a density scale linear to the gradation visual recognition characteristics of humans. As described above, since the photoelectric conversion characteristics of the image pickup device are generally different from the gradation visual recognition characteristics of humans,
By using the γ correction table as shown in FIG. 6, the correction (γ correction) is performed so that the output D ′ becomes linear to the gradation visual recognition characteristic of human as shown in FIG.

As shown in FIG. 14, the γ-corrected signal is converted into 1/0 binary data capable of reproducing a gradation image by the next gradation processing unit 25 using a dither method or the like. It is converted and becomes the output of the reading device.

By the way, there are both negative and positive films as microfilms, and they are used properly according to their use. Therefore, in an analog reader printer that directly projects a film image on a photoconductor, there is a device that incorporates two types of image forming processes so that both negative and positive images can be copied.

[0009]

An analog printer having two types of negative / positive image forming processes as described above is provided with two types of developing devices because toners having different polarities are required. It has a switching mechanism, has a circuit or mechanism for switching the polarity of high voltage output such as a transfer charger, has two types of high voltage power sources due to the difference in the load characteristics of these high voltages, and switches the blank exposure to create a margin. There is a drawback that the circuit mechanism becomes complicated. However, by setting the high-voltage output so that the optimum γ characteristic (exposure amount-density characteristic) can be obtained for both negative and positive films, an image with good gradation can be obtained in any case.

On the other hand, in a digital reader printer, a positive copy can be obtained from either negative or positive film by basically inverting and outputting a digital signal. No complicated circuit mechanism is required.

However, an image with good gradation cannot be obtained only by inverting the digital signal in this way. One of the reasons is that the γ characteristic of the film is not linear but nonlinear, and the curves near A and B in FIG. 9 are not symmetrical. Therefore, when a positive original is projected on the film, the portion A is the line drawing portion B, and when the negative original is photographed on the film, the portion B is the line drawing portion A and the background portion. Therefore, the gradation is different in the negative film positive film.

In the conventional digital image processing technique, γ correction is generally performed by amplifying an output signal of a light receiving element for digitally reading an original image, converting the amplified signal into a digital signal, and converting the digitally converted original. It is performed on the image signal. The data conversion characteristic for converting the signal data has a one-to-one correspondence with the data characteristic input to the reading sensor so as to correct the difference between the photoelectric conversion characteristic and the human visual perception characteristic.
A data table is used that has a linear scale or a non-linear scale instead of the output characteristics of the above.

In particular, in the case of the microfilm, the γ characteristic of the film itself is non-linear as described above, the negative film and the positive film are present, and the original image (original image at the time of photographing) Change the print density level depending on the lens resolving power of the camera at the time of image capture, the degree of out-of-focus, the type of film (silver salt, diazo, vencular, etc.), the film developing solution, the developing conditions, etc. There is a need.

By the way, the reason why it becomes necessary to change the density level in the case of obtaining a print using such a microfilm as a medium will be described with reference to FIGS.
Will be explained.

First, FIG. 18 shows the relationship between the negative film transmission density and the negative film transmission density. The horizontal axis plots the original reflection density and the vertical axis plots the film transmission density.

Here, the reflection density of a white background portion of a general document has a reflection density of about 0.06 to 0.07, and the reflection density corresponding to a black character portion is about 1.2, and a thin thin line. The reflection density of the portion corresponding to the character portion is approximately 0.
It is generally accepted that it has a reflection density of about 3 to 0.4 and a reflection density of about 0.6 to 0.7, which is equivalent to that of a general pencil document. Therefore, when forming a microfilm based on such an original, a desired film can be obtained by developing the density to be developed in the film development processing step to an appropriate density (that is, showing the transmission density of the finished background portion). ..

Curves A, B, and C are those obtained by developing the density of the background to be developed in the film development processing step into, for example, three types when forming a microfilm. The curve A is for the case where the transmission density of the background is finished to about D = 0.6. When each original density is formed into a film, each original density shows a transmission density curve as shown by the curve A.

The portion corresponding to the white background portion (0.06) of the original is the background density (0.68) on the microfilm, and the portion corresponding to the black background portion (1.10) of the original is the character portion on the microfilm. At a transmission density equivalent to (0.09)
Therefore, the relationship with each document density is as shown by the curve A.

Similarly, the B curve represents the background transmission density D = 1.
The part corresponding to the white background (0.06) of the document is the background density (1.0) on the microfilm, and the part corresponding to the black background (1.10) of the document when finished to about 0. Is (0.10) as the transmission density corresponding to the character portion on the microfilm, and the relationship with each document density is as shown by the curve B.

Similarly, the C curve shows the transmission density of the background as D = 1.
The portion corresponding to the white background portion (0.06) of the document is the background density (1.5) on the microfilm, and the portion corresponding to the black background portion (1.10) of the document when finished to about 4 Is (0.12) as the transmission density corresponding to the character portion on the microfilm, and the relationship with each document density is as shown by the curve C.

The density relationship between the original and the microfilm will be described with reference to FIG.

FIG. 19 is an explanatory diagram for verification based on the above description. As shown in the two quadrants in the figure, the second quadrant shows a view similar to FIG. 18, the first quadrant shows the film transmission density on the horizontal axis, and the horizontal axis shows image density data (film image FIG. 3 is a diagram showing image data which is digitally read by a light receiving element and converted into digital data, and shows a relative relationship of each. In the second quadrant, two types of background density of the film (density of D = 0.6 and density of D = 1.4) are typically shown.

The curve I shown in the first quadrant shows the image data of the film original as the image density of the film original with the light quantity for projecting the film original being constant (the lighting voltage for projecting the film is made constant without depending on the background density of the film). Is plotted according to. Curve II is an increase in the amount of light projected on the film.

When the film with D = 0.6 is explained here, the reflection density of the document in the portion corresponding to the thin thin line character portion is about 0.3 as described above.
This shows a transmission density of about 0.3 on the film, and this transmission density of 0.3 is about 80 as a density data value.
The data value of H is shown. When a film with D = 1.4 is used, similarly, a document density of about 0.3 is a transmission density of about 0.8 on the film, and a data value of about 15H is shown as density data.

As can be seen from this figure, for the film with D = 0.6, the density data value when faithfully reproducing the reproducibility of the fine line is defined as, for example, 80H, so that the final print image is obtained. When obtained, the reproducibility of fine lines is good.

However, in the case of D = 1.4 film, when attempting to reproduce the original density of 0.3, the reproducibility of the fine line cannot be satisfied because the density data value is low.

Therefore, in order to eliminate the above-mentioned inconvenience, when the background density is high, D = 1 by increasing the light quantity for projecting the film as shown by the curve II in the first quadrant. A density data value of 80H can be obtained even in the film of 0.4. That is, it goes without saying that the light amount level may be lowered in the low-density film and the light amount level may be increased in the high-density film. If the light amount is changed at the same time, the density data of the background portion of the film (background fog when printed) also changes, and it is necessary to remove this fog. That is, FIG.
In the film of D = 0.6 in the second quadrant of the above, when the film density is 0.68, it becomes the point where it intersects with the curve I of the first quadrant. When the density is 1.4, it is a point intersecting with the curve II in the first quadrant, so this level also needs to be changed.

Although the above description has been made with respect to the negative film, the same tendency is also given to the positive film. Also, with regard to copy originals handled by a copying machine, various kinds of originals similar to the range of densities handled by microfilm (colored paper, newspaper originals, thin pencil written characters, and thin pencil written characters with a dark background) are used. It is necessary to change the print density level according to the purpose or preference of the user rather than the existence.

[0029]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is an object of the present invention to satisfactorily read an original image at a desired density.

Another object of the present invention is to satisfactorily read a film image such as microfilm.

Another object of the present invention is to satisfactorily read both positive and negative images.

That is, according to the present invention, a light source for exposing a document image, a reading unit for photoelectrically reading the document image exposed by the light source, and a conversion for converting the density characteristic of the image data output from the reading unit. The present invention provides an image reading apparatus having a unit and a setting unit that sets the conversion characteristic of the density characteristic by the conversion unit and the light amount of the light source in association with each other. The present invention also provides an image reading apparatus having an instruction unit for instructing and a control unit for controlling the light amount of the light source and the conversion characteristic of the conversion unit according to the instruction of the image density by the instruction unit. An image having an instruction means for instructing whether the image is a positive image or a negative image, and a control means for controlling the light amount of the light source and the conversion characteristic of the conversion means in accordance with the instruction by the instruction means. There is provided a reading device.

[0033]

EXAMPLE 1 FIG. 1 is a block diagram when the present invention is applied to a reader printer. In FIG.
Reference numeral 1 is an image sensor for reading a magnified projection image of a microfilm, 2 is an amplifier for image width of the analog image signal output from the image sensor 1, and 3 is connected to the amplifier 2 to convert the analog signal into a digital signal. A / D converter for the purpose, 4 is a γ correction circuit for converting the input data based on a certain fixed γ conversion curve, and 5 is an edge emphasis circuit which is a digital filter for converting the input signal into an edge emphasis waveform. , 6 is a pseudo-halftone processing circuit (for example, using an error diffusion method) for performing a pseudo-halftone process on an input signal, and 7 is whether or not to perform a halftone process.
A selector 8 selected by a SEL signal is a binarization circuit for converting multi-valued data into binary data in order to send the data to a binary printer (for example, a laser beam printer LBP).

Further, 9 is a light source such as a halogen lamp for exposing the microfilm, and 10 is light quantity data EN.
/ EP is a light source drive unit that controls the light amount by controlling the amount of electricity supplied to the light source 9 according to / EP. 11 is a control unit, 1
Reference numeral 2 denotes a keyboard, and the control unit 11 outputs various data to the γ correction circuit 4, the edge emphasizing circuit 5, and the selector 7 according to the reading conditions of the film by the keyboard 12.

In the above structure, the enlarged projection image of the microfilm exposed by the light source 9 is image-scanned by the scanning optical system (not shown) and is taken out from the image sensor 1 by line synchronization as an analog value as a serial image signal. This signal is amplified by the amplifier 2 to an appropriate range as an input signal to the A / D converter 3. At this time, the offset voltage is also adjusted.

The signal input to the A / D converter 3 is converted into an 8-bit digital signal from 0 to 255, and γ
It is input to the correction circuit 4. The γ correction circuit 4 can be composed of one or several PROMs (27256, etc.) as shown in FIG. 2, for example. An input signal from the A / D converter 3 is input to A0 to A7 as an address bus, and an output signal is taken out from 00 to 07 as a data bus.

FIG. 8 shows the relationship between the output data value and the input data value of the PROM. In FIG. 8, A shows a γ conversion curve used in the case of a negative film in the character mode, and B shows a γ conversion curve used in the case of a positive film in the character mode.

In FIG. 8, the inclinations of A and B can be changed by setting γ0 and γFF as will be described later, which makes the conversion characteristic of the output data value with respect to the input data value variable. There is.

The PROM further stores light quantity data EN / EP for controlling the light quantity of the light source, and the read light quantity data EN / EP is stored in the light source drive section 10.
Entered in.

Further, A8 is used as a SEL signal as a selection signal of the γ conversion curve. This SEL signal is sent by the operator to the density dial (
It is configured so that it can be operated thinly. Also,
A9 is used as a negative / positive signal for switching the γ curve depending on whether the negative film is a positive film.

A10 is a line image (hereinafter, character mode)
And as a signal for switching the γ conversion curve as a photographic image (hereinafter, photograph mode) switching signal.

Waveforms as shown in FIGS. 3 and 4 are stored in the PROM of the γ correction circuit 4 based on the data measured in advance. FIG. 3 is a .gamma. Characteristic curve in the case of a negative film in the character mode, which is selected by the SEL signal so that the base density of the film can correspond to the range of 0.6 to 1.4. Further, FIG. 4 shows a γ characteristic curve in the case of a positive film in the character mode, which can also correspond to the base density of the film and is selected by the SEL signal.

FIG. 5 is a block diagram of the keyboard 12 operated by the operator. In the figure, the print button 51 and the print density selection button 52 (the dark and light buttons are selected to select the LEDs shown above the print button 51 and the print density selection button 52). The display at that time is displayed on the index 53), and the number of sheets setting key button 5
4 (+ /-/ C: clear), film selection button 55
(NP / PP / AUTO), character / photograph selection button 56 (text mode / photograph mode), sharpness selection button 57 (moved to the soft side becomes soft, and moved to the sharp side becomes hard). The layout is shown and is selected according to the operator's preference.

By the way, the digital signal output from the γ correction circuit 4 in FIG. 1 is input to the edge enhancement circuit 5 and is digitally filtered by the Labrian convolution (3 × 3) mask shown in FIG. The degree of edge enhancement can be changed by the Labrian convolution mask coefficient, and the SHAR corresponding to the sharpness selected by the sharpness selection button 57 of the keyboard 12 can be changed.
The edge enhancement degree is determined by the P data α. Further, when the convolution mask is used, the pattern is not necessarily a 3 × 3 pattern, and may be, for example, a 5 × 5 mask pattern.
Further, these mask coefficients are not limited to those shown in FIG. 6, and may be configured as shown in FIG. 7 from the viewpoint of enhancing edge enhancement in the oblique direction, for example.

Further, in the above-mentioned embodiment, the edge emphasis degree can be changed, but it goes without saying that the edge emphasis degree may be a fixed value.

Although it is possible to increase the edge emphasis degree by providing a plurality of stages of the edge emphasis circuit, the same effect can be obtained by multiplying the mask coefficient by a plurality of times.

Generally, in the case of a positive film, dust, dust, scratches, and the like have a density close to that of the line drawing portion, so if the edge emphasis degree is increased, the image becomes considerably conspicuous and becomes a dirty image. On the other hand, in the case of a negative film, the density is close to the background part (background), and therefore it is useless to enhance the edge emphasis. Therefore, it is better to change the edge emphasis degree depending on whether the film is a negative film or a positive film, and the SHARP data α differs depending on whether the film is a negative film or a positive film.

Further, the sharpness of the film varies depending on the lens resolution of the camera at the time of photographing the original (the original before photographing), the degree of out-of-focus, the type of film, the developing solution of the film, the developing conditions, etc. It is necessary to change the edge emphasis degree depending on the purpose of the person, and the edge emphasis degree is made variable by the sharp data from the control unit 11 based on the value of the sharpness selection button 57 on the keyboard 12 of the apparatus.

The signal edge-enhanced by the edge emphasizing circuit 5 is input to the halftone processing circuit 6 and the binarization circuit 8 and is subjected to pseudo-halftone processing or simple binarization processing. The halftone processing circuit 6 uses, for example, an error diffusion method (ED method), which compares a certain target pixel with a certain threshold value and diffuses the generated error to the density of the next plurality of pixels. And is one of the typical pseudo halftone processing. The binarization circuit 8 is a circuit that compares an input 8-bit signal with REF data and converts it into a binary value of 1 or 0. Whether the signal passed through the halftone processing circuit 6 or the signal passed through the binarization circuit 8 is used depends on the character / photograph selection button 5 on the keyboard 12.
Selection is made by the selector 7 according to the operation of 5. The selector 7 is switched by the ASEL signal from the control unit 11.

The image subjected to the halftone processing has a good gradation, and in particular, it has a remarkable effect in the case of a photographic image. Also,
It is possible not only to photograph pictures but also to make line drawings with different densities of characters such as light and shade. However, the pseudo-halftone processing in a binary printer (depending on whether a dot is hit or not depending on a 1-bit input signal of 0 or 1 has a uniform density of 1 dot itself) has a blur effect. However, the sharpness is slightly deteriorated. Therefore, it is better not to intentionally perform the pseudo halftone processing in the case of a film image composed of only line drawings. Therefore, it is possible to select whether to perform halftone processing or binarize without performing halftone processing.

These selections can be made by the user using the character / photograph selection button 56 on the keyboard.

Further, the edge emphasis degree in the photo mode is made higher by making the Laplacian convolution mask coefficient different from the coefficient in the character mode and making it about 1/2 of that in the character mode. Further, the edge emphasis degree is determined by the SHARP data α. Further, if more gradation is required, the sharpness selection button 57 of the keyboard 12 is used to move it to the software side so that it can be decided according to the operator's preference.

Next, as the data value (measurement data stored in advance in the PROM) set in the γ correction circuit 4 in FIG. 1, the following data is used based on the result of our study. Hereinafter, the details will be described.

First, the meanings of γ0 (named gamma zero) and γFF (named gamma FF) in the gamma characteristic curves of FIGS. 3 and 4 and the gamma conversion curve of FIG. 8 will be described. In FIG. 8, the horizontal axis represents the input data value and the vertical axis represents the output data value, which is a hexadecimal HEX value, and γ0 is the data in the negative film (for example, the base density is 1.
0 is the data generated when a certain amount of light is applied to the film). Particularly, in the case of a negative film as shown in FIG. 9, A is the background portion and B is the line drawing portion, so that the line drawing portion is faithfully reproduced. It shows the point where the noise level of the background part can be reproduced and cut, and this is called the rising point.

By connecting the rising point γ0 and the FF level with a straight line A and making the level of γ0 variable,
The γ conversion characteristic is changed so that an appropriate image can be obtained according to the type and density of various films.

Similarly, in the case of a positive film, A is a line drawing portion and B is a background portion as shown in FIG. 9, and therefore γFF is a rising point in the case of a positive film in FIG. Rising point γ
By connecting the FF level and the 00 level and making the γFF level variable, the same effect as the negative can be obtained. Further details will be described with reference to FIG.

In FIG. 10, (A) shows the appearance frequency (n) (referred to as a density histogram) with respect to the image density data in the negative film and in the positive film. When the density histogram was created, the density data was used as light intensity data, and the histogram was obtained by changing the density of the film with the same light intensity and the same original.

In the figure, in the case of a negative film, the transmission density of the background portion is a state where the solid line is D = 1.4 and the wavy line is D = 0.6. In the case of a positive film, the transmission density of the character information part is the state where the solid line is D = 1.4 and the wavy line is D = 0.6.

In FIGS. 10 (A) and 10 (B), the higher part of the mountain represents the background part and the lower part of the mountain represents the character part, and the point close to the inflection point of the background part and the character part. Is a point of γ0 in the case of a negative film, and a γFF point in the case of a positive film.

Next, how to obtain an appropriate image will be described with reference to FIG. (A) shows the case of a negative film and (B) the case of a positive film, and the horizontal axis shows the light quantity E [LUX].
The vertical axis is the rising point, and as described with reference to FIG. 8, γ0 [HEX] for negative and γFF for positive.
Indicates [HEX]. By the way, as a test chart for evaluation, TYPE typed characters, pencil writing characters, gradation reproduction step frames (having solid black to halftone density), and character types such as thin lines and bold characters are mixed. Images obtained by shooting the image information of the film are used, and as for the film density, both negative film and positive film are formed into images having base densities of D = 0.6, D = 1.0 and D = 1.4. It was evaluated.

In FIG. 11A, D = 0.6 and D =
Appropriate images of 1.0 and D = 1.4 film are shown by straight lines. Each of these proper rising points γ0 when the light quantity E is changed is obtained. That is, by satisfying the relationship between the light amount and the rising point γ0, it is possible to express the reproducibility and halftone reproduction of characters without fogging. Further, among the respective straight lines, the point having the optimum image in which the image output to the printer is faithful according to the respective densities and the gradation recognition characteristics of human beings can be sufficiently satisfied is determined. This point is shown in Figure 11.
It is the point where it intersects with the curve shown by the broken line in (A), and D =
With a film of 0.6, γ0 = 70HEX, with D = 1.0, γ0 = 48HEX, and with D = 1.4, γ0 = 20HEX.
The DATA value becomes as follows, and by satisfying this relationship, the best appropriate image corresponding to each density can be obtained.

Similarly, in the case of the positive image, the proper images of the film of D = 0.6, D = 1.0, and D = 1.4 are indicated by straight lines in FIG. 11B. Then, when the light amount E is changed, each appropriate rising point γFF is obtained. Further, an appropriate point is a point intersecting with a curve shown by a broken line in FIG. 11B. ΓFF = 60HEX for a film of D = 0.6, γ0 = 70H for D = 1.0.
DAT such as γ0 = 90HEX for EX and D = 1.4
The value becomes A, and by satisfying this relationship, the best proper image corresponding to each density can be obtained. The above has been a description of how to obtain an appropriate image of a negative film and a positive film.

Then, based on the above experimental results, an example of the structure for determining an appropriate gamma curve shown in FIGS. 3 and 4 will be described.

FIG. 3 is a gamma characteristic curve in the case of a negative film. In the figure, the horizontal axis is the density level, which corresponds to the print density selection button 52 of FIG. 5, and the black triangle mark side which is the variable dial of image density is In the direction of increasing the density, the white triangle mark side is the direction of decreasing the density. The left vertical axis is the light intensity E
Shows the light amount E from the darkest to the lightest density level.
Changes so as to decrease (curve A), and the right vertical axis shows the rising point γ0, and γ0 changes so as to increase from the darker to the lighter concentration level (curve B).
The light amount E and the rising point γ0 are simultaneously set according to the density level.

FIG. 4 shows gamma correction in the case of a positive film. In the figure, the horizontal axis represents the density level, which corresponds to the print density selection button 52 in FIG. 5, and the black triangle mark side, which is a variable dial of image density, represents the density. In the direction of increasing the density, the white triangle mark side is the direction of decreasing the density. The left vertical axis indicates the light amount E, and the light amount E is changed so as to increase from the darker density level to the lighter density level (curve A), and the right vertical axis indicates the rising point γFF from the darker density level. ΓFF changes so as to decrease toward the thinner side (curve B), and the light amount E and the rising point γFF are simultaneously set according to the density level.

Table 1 shows the gamma correction table data of FIGS. 3 and 4, and the F value in the table is
The image density is set by the print density selection button 52 shown in FIG. 5, where F1 is the side for increasing the image density, and F3
3 is the side that reduces the image density.

EN and EP represent light quantity data for the negative film and the positive film, respectively, and are hexadecimal HEX displays. The EN data has a large light quantity on the F1 side and F33.
The side has a table that changes logarithmically with the change of the F value so that the light amount decreases, and the EP data shows that the logarithm is changed with the change of the F value such that the light amount is small on the F1 side and the light amount is large on the F33 side. Has a table that changes dynamically. Further, γ0 is a gamma correction table in the negative mode, and F1
From F3 to F33, the data value is changed logarithmically from the smaller one to the larger one, and γFF is the gamma correction table in the positive mode, and the data value is larger from F1 to F33. It is a gamma correction data value table which changes logarithmically from to a smaller one. The light amounts EN and EP and the rising points γ0 and γFF are previously input as data to the PROM of FIG.

As described above, in the PROM of the γ correction circuit 4,
A look-up table that corresponds to each of the negative film and the positive film and is referred to by the image density corresponding to the density selection from the keyboard 12 is stored, and the rising point γ0 / γF obtained from this look-up table is stored.
The γ conversion characteristic and the light amount of the light source are set by F and the light amount data EN / EP.

As a result, it is possible to obtain a proper image having a desired image density.

[0070]

[Table 1]

(Embodiment 2) Next, based on the above experimental results, an appropriate density correction process which is more convenient for the user will be described with respect to the second embodiment.

FIG. 12 shows a gamma correction curve in the second embodiment which is an improvement of the gamma correction curve of the negative film in the first embodiment. In the first embodiment, the density level is variable. The width was set to a wide range by adopting a non-linear curve in order to cover all the films (density, type, etc.), but in the second embodiment, the film density is 0.8 to 1. 2 can be printed faithfully and the ease of density adjustment is taken into consideration.

In other words, generally, the camera photographing technology / film developing technology for finishing the finished density of the base portion when it is formed into a film from 0.8 to 1.2 is solid, and the commercial value as a laboratory work is particularly high. The reality is that it is built as a high-quality business. As a result, when outputting a magnified image of the film to a reader printer, the operability of density adjustment during printing and the image reproducibility become problems.

That is, although the density dial is operated according to the user's preference, all films (density,
When the image is output, it is important that the image output is free from fogging on the paper base and that the density level of the image density is stably maintained.
When 2 is changed by 1 STEP (darker or lighter), a sudden change in density (such as sudden increase of fog or sudden thinning) does not occur.

In FIG. 12, the inflection point of the alternate long and short dash line A and the solid line B indicates the film density. It corresponds to 8 to 1.2, the inflection point on the dark side of the density level is on the 1.2 side, and the other is on the 0.8 side. The area from 1 to 2 is intended to cover a film having a film density of 1.2 or more, and the area from 1 is intended to cover a film having a film density of 0.8 or less.

In other words, although the density dial is operated according to the user's preference, all films (density, density,
Even if the type) is used, it is important that the image output is free from fogging on the paper base and that the level of image density is stably maintained, and the density dial is changed by 1 STEP ( This is to prevent a sudden change in density (such as sudden increase in fog or sudden decrease in thickness) when the density is increased or decreased. If you need to make fine adjustments according to your preference, set the density dial to 1
It is designed so that a sufficient measure can be taken by moving it in steps.

(Embodiment 3) FIG. 13 shows a gamma correction curve in the third embodiment which is an improvement of the gamma correction curve of the negative film in the first embodiment.
In the embodiment described above, the variable width of the density level has a wide range corresponding to the adoption of a non-linear curve in order to cover all films (density, type, etc.), but in the third embodiment, Is intended to correspond to a film in which the finish of the film density is deviated to a very high contrast side or a low contrast side.

That is, generally, the camera photographing technology / film developing technology for finishing the finished density of the base portion when it is formed into a film from 0.8 to 1.2 is solid, and the commercial value as a laboratory work is particularly high. Although it is currently established as a high-quality business, microfilm is used for a long time, exposed for a long time due to handling of storage method, etc. By the method of obtaining the above, etc., it tends to be deteriorated (generally, the transmission density tends to be lower) than the original transmission density. Therefore, even in such a case, it is necessary to take a configuration that can be adapted to the user, and when outputting a magnified image of the film to the reader printer, the operability of density adjustment during printing and the image reproducibility become problems.

According to FIG. 13, is the film density of 1.
Corresponding to 0 to 1.2, the area of ~ covers the film density of 1.2 or more to about 1.4, the ~ area covers 1.4 or more of the film density, and the ~ area covers the film density. The area of 0.8 to 1.0 and the area of ~ correspond to the film density of 0.6 to 0.8. This makes it possible to faithfully print the film density of 0.6 to 1.4 and to adjust the density. This is to consider ease.

That is, although the density dial is operated according to the user's preference, all films (density, density,
Even when using the type), it is important for image output that there is no fog on the base of the paper and that the density level of the image density is maintained stable, and the density dial 1S
This is to prevent sudden changes in density (such as sudden increase in fog or sudden decrease in thickness) when TEP changes (dark or light), and it is necessary to make fine adjustments according to the user's preference. For example, by moving the concentration dial one step, a sufficient response can be taken.

This embodiment is to obtain a gamma correction curve which is more faithful to the taste of the user. As mentioned above, dark films have high gradation for thin films,
It is designed to be highly reproducible.

In the above embodiment, as shown in FIG. 1, image processing is performed via the gamma correction circuit 4 between the edge enhancement circuit 5 and the A / D converter 3, but the edge level is emphasized more faithfully. For the purpose of improving the sharpness of the image, a configuration may be adopted in which a γ correction circuit is inserted after the edge enhancement.

Although the error diffusion method is used as the pseudo halftone processing method, the present invention does not limit the method, and any method can be used as long as it is a means for producing gradation.

[0084]

As described above, in the digital reader / printer, the negative / positive film is selected by selecting the optimum γ curve and changing the light amount of the light source accordingly.
A copy with good gradation can be easily obtained from any of the positive films. Furthermore, by distinguishing characters from photographs and obtaining images corresponding to the respective γ characteristics, it is possible to obtain a printed image with high gradation even if the photographic microfilm has a very high gamma.

[Brief description of drawings]

FIG. 1 is a block diagram of an image processing unit according to the present invention.

FIG. 2 is a diagram showing an example of a γ correction circuit.

FIG. 3 is a diagram showing an example of a γ correction curve.

FIG. 4 is a diagram showing an example of a γ correction curve.

FIG. 5 is a configuration diagram of a keyboard.

FIG. 6 is a diagram showing an example of an edge emphasis coefficient.

FIG. 7 is a diagram showing another example of the edge emphasis coefficient.

FIG. 8 is a diagram showing a relationship between input data values and output data values.

FIG. 9 is a diagram showing an example of γ characteristics of a film.

FIG. 10 is a diagram showing an example of a density histogram.

FIG. 11 is a diagram showing a relationship between light amount and output.

FIG. 12 is a diagram showing another example of a γ correction curve.

FIG. 13 is a diagram showing still another example of the γ correction curve.

FIG. 14 is a block diagram of a general image processing unit.

FIG. 15 is a diagram showing the relationship between document density and output.

FIG. 16 is a diagram showing a γ conversion operation.

FIG. 17 is a diagram showing the relationship between document density and γ-corrected data.

FIG. 18 is a diagram showing a relationship between document density and film density.

FIG. 19 is a diagram showing a relationship between document density and film density.

[Explanation of symbols]

 1 image sensor 2 amplifier 3 A / D converter 4 γ correction circuit 5 edge enhancement circuit

Claims (5)

[Claims] 1. A light source for exposing an original image, a reading unit for photoelectrically reading the original image exposed by the light source, a conversion unit for converting the density characteristic of the image data output from the reading unit, An image reading apparatus comprising: a setting unit that sets the conversion characteristic of the density characteristic by the conversion unit and the light amount of the light source in association with each other. 2. The image reading apparatus according to claim 1, wherein the reading unit reads an image recorded on a film. 3. The image reading apparatus according to claim 1, wherein the setting unit sets the light amount of the light source and the conversion characteristic of the conversion unit according to a desired reproduced image density instructed. 4. The display device further comprises an instruction device for instructing a desired reproduced image density, and the setting device sets the light amount of the light source and the conversion characteristic of the conversion device in accordance with the image density instruction by the instruction device. The image reading device according to claim 1. 5. An instruction means for instructing whether an original image is a positive image or a negative image is provided, and the setting means sets the light amount of the light source and the conversion characteristic of the conversion means in accordance with an instruction from the instruction means. The image reading apparatus according to claim 1.