JPH03160877A - Picture reader - Google Patents

Abstract

PURPOSE:To easily obtain an output picture with excellent gradation even from any of films by selecting an optimum data correction characteristic depending on kinds of the negative and positive films. CONSTITUTION:A serial picture signal extracted from an image sensor 1 is amplified by an amplifier, converted into a digital signal at an A/D converter 3 and inputted to a gamma correction circuit 4. The circuit 4 as shown in figure consists of a PROM and an input signal is inputted to input ports A0-A7 as address buses and an output signal is extracted from output ports 00-07 through a data bus. Ports A8, A9 are used as input ports for selection signals of a gamma curve as SELO,SELI signals. Moreover, a port A10 is used as an input port for signal selecting the gamma curve depending on a negative film or a positive film as an N/P (negative/positive) signal. In this case, a waveform data as shown in waveform diagram is stored in the PROM 4 as an experiment data measured in advance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image reading device that performs digital image processing, and particularly to an image reading device that processes a film original such as a microfilm using a CCD.
The present invention relates to an image reading device used in a digital microscanner or a digital microprinter that performs digital image processing by reading an image using an image sensor such as a charge-coupled device (charge-coupled device).

[Prior Art] Conventionally, reader printers for microfilm have been used to illuminate microfilm images with illumination lamps.
The projected light is magnified by a projection lens to a desired magnification, slit-exposed onto a photoreceptor such as a photoreceptor drum, and the image on the photoreceptor is electrophotographically copied by performing steps such as toner development and transfer. A so-called analog type soda printer is available. Also, recently, instead of exposing the above-mentioned projection light onto a photoreceptor through a slit, the projection light is read by an image sensor such as a CCD.
A so-called digital type reader printer has also been developed, which obtains a copy by sending a digital signal to a printer such as an LBP (laser beam printer) after performing signal processing such as image processing.

By the way, there are two types of microfilm, negative film and positive film, and they are used depending on their purpose. Therefore, in analog reader printers, both negative and positive copies are made (boji copy).
2f as possible! There was a device that incorporated a similar image forming process.

[Problems to be Solved by the Invention] In conventional analog reader printers that have two types of image forming processes, negative and positive, for example, two types of developing devices are required because toners of different polarities are required. However, because of the differences in the load characteristics of these high voltages, the high voltage power supply has a mechanism to switch between these developing devices, a circuit or mechanism to switch the polarity of the high voltage output of the transfer charger, etc. Although it has the disadvantage that the circuit and mechanism become complicated due to the need to prepare blanks and change the blank exposure to create margins, it provides the optimal γ characteristics (exposure-density characteristics) for both negative and positive films. By setting the high voltage output value in this way, a copied image with good gradation can be obtained in any case.

In contrast, conventional digital reader printers basically only output negative/inverted digital signals.
Since a physical copy (a copy image of a physical image) can be obtained from either film, there is no need for complex circuits and mechanisms unlike analog reader printers.

However, it is not possible to obtain a copy image with good gradation simply by inverting the digital signal in this way. One of the main reasons for this is that the gamma characteristic of the film is not linear but nonlinear, and the curves near points A and B in the gamma characteristic curve of the film in Figure 9 are symmetrical. By not being. Therefore, when a positive original is photographed on film, part A becomes the line drawing part and part B becomes the background part, but conversely, when a negative original is taken on film, part B becomes the line drawing part. , since the part A becomes the background part, the gradation is different between the negative film and the positive film.

In view of the above points, an object of the present invention is to select an optimal γ correction curve suitable for each film, such as a negative film or a positive film, even in a digital reader printer. It is also possible to provide an image reading device that can easily obtain an output image with good gradation like an analog type reader printer.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an imaging means that converts a formed document image into an electrical signal, and a digital conversion device that amplifies the electrical signal and converts it into a digital signal. means, identification signal generating means for generating an identification signal indicating whether the document image is a negative image or a positive image, and a data correction characteristic selected from a plurality of data correction characteristics according to the identification signal. The present invention is characterized by comprising a data correction means for correcting the data of the digital signal using the data.

Further, as one form of the present invention, the data correction means includes:
It is characterized in that it is comprised of a memory element in which conversion data related to the plurality of data correction characteristics are stored in advance, and that the data correction processing is performed by performing a table lookup on the memory element.

[Function] The present invention selects the optimum data correction characteristic (γ curve) depending on the type of film, whether negative film or positive film, in an image reading device used in a digital reader printer or the like. As a result, an output image with good gradation can be easily obtained from either negative film or positive film.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

■Basic configuration FIG. 1 shows the basic configuration of an embodiment of the present invention. In the tree diagram, A is an imaging means that converts a formed original image into an electrical signal. B is a digital conversion means that amplifies the electric signal and converts it into a digital signal. Reference numeral C denotes an identification signal generating means for generating an identification signal indicating whether the original image is a negative image or a positive image. D is a data correction means for correcting data of the digital signal using data of a data correction characteristic selected from among a plurality of data correction characteristics in accordance with the identification signal.

As an example, the data correction means D includes a memory element in which conversion data related to the plurality of data correction characteristics are stored in advance, and performs the data correction process by performing a table lookup on this memory element.

(1) First Embodiment FIG. 2 shows an example of the main circuit configuration of a film reader printer embodying the present invention. In the tree diagram, 1 is an image sensor (
For example, a contact image sensor), 2 is an image sensor 1
An amplifier 3 is connected to the amplifier 2 to amplify the output signal of the image sensor, and an A/D is connected to the amplifier 2 and converts the analog signal output from the amplifier into a digital signal.
(analog/digital) converter. 4 is A/D
a γ correction circuit that converts input data from the converter 3 based on a certain fixed curve (γ curve);
An edge emphasis circuit 5 is a digital filter that converts the input signal from the γ correction circuit 4 into a signal with an edge emphasis waveform. 6 is a halftone processing circuit (for example, a signal processing circuit using an error diffusion method) that performs pseudo-halftone processing on the input signal from the edge emphasis circuit 5; 7 is an ASEL signal (automatic selection signal) that indicates whether or not to perform halftone processing; ) to send data to a binary printer (e.g., laser beam printer [LBP]).
This is a binarization circuit for converting multi-value data from the edge emphasis circuit 5 into binary data. The output signal of the binarization circuit 8 is input to the selector 7.

In the above configuration, an enlarged projected image of the microfilm is scanned by a scanning optical system (not shown), and is extracted as a serial image signal from the image sensor 1 as an analog value using a line periodic signal. The serial image signal is amplified by the amplifier 2 to an appropriate range as an A/D converter input signal, and offset voltage adjustment is also performed at the same time. Next, the signal input to the A/D converter 3 is converted into an 8-bit digital signal from 0 to 255, and then input to the γ correction circuit 4 .

The γ correction circuit 4 is, for example, a FROM as shown in FIG.
(Programmable ROM).

In FIG. 3, input signals are input to input ports AO to A7 as address buses, and output signals are taken out from output ports 00 to 07 as data paths. Also, 88, A9
is SELO. SEL1 {Used as a manual boat for the selection signal of the γ curve. Also, AID is N/P
The (negative/positive) signal is used as a manual boat for switching the γ curve depending on whether the film is a negative film or a positive film.

At this time, the FROM 4 in FIG. 3 stores waveform data as shown in FIGS. 4 and 5 based on experimental data measured in advance. FIG. 4 shows a γ curve for a normal film, which is selected from three types of curves (P, P., PC) by the SELO and SELI signals depending on the density, contrast, gradation, etc. of the film.

Also, Figure 5 shows the γ curve for negative film,
Also, SE is selected from three types of curves (N, , Nb, Nc) depending on the density, contrast, gradation, etc. of the film.
Selected by LO and SELI signals. For example, N. The curve for D (film density a) is used for film with an appropriate density of 0.8 to 1.2, and the curve for N is used for film with an appropriate density of 0-06 to 0.
．． A curve of 8 is used for low contrast films, and a curve of N, on o-1.2Ll is used for high contrast films. The same applies to Bojifilm.

The digital signal output from the γ correction circuit 4 is input to the edge emphasis circuit 5, and digitally filtered using a Labrasian 3×3 convolution mask as shown in FIG. The degree of edge emphasis at this time can be changed by the coefficient α to the Labrasian convolution mask,
The degree of edge emphasis is determined by SHARP data (sharpness data).

In general, in the case of a positive film, dust, dirt, or scratches have a density close to that of line drawings, so if the degree of edge emphasis is increased, they become quite noticeable, resulting in a clean image. On the other hand, in the case of negative film, the dust and the like have a density close to that of the background area, so even if the degree of edge enhancement is increased, it is not noticeable.

Therefore, it is better to change the strength of the edge emphasis depending on whether it is a negative film or a positive film.
IARP data values vary depending on whether the film is a negative film or a positive film. In addition, the resolution of the camera lens when shooting the film manuscript (original U4 before shooting),
Film sharpness (
It is necessary to change the degree of edge enhancement depending on the type of film original or the user's intended use. The degree of edge emphasis can be varied based on the value. The signal edge emphasized by the edge emphasis circuit 5 is sent to the halftone processing circuit 6.
and undergoes pseudo-halftone processing. This processing uses, for example, the error diffusion method (ED7). As is well known, this method compares a certain pixel of interest with a certain threshold,
This is a method of diffusing the generated error (the difference value between the density of the pixel of interest and the threshold value) to the density of the next plurality of pixels, and is one of the typical pseudo halftone processes.

Further, a binarization circuit 8 connected to the output terminal of the edge emphasis circuit 5 in parallel with the halftone processing circuit 6 compares the input 8-bit signal with REF data (reference data), and compares the input 8-bit signal with REF data (reference data).
This is a circuit that converts it into a binary value of 0. The selector 7 selects whether to use the signal passed through the halftone processing circuit 6 or the signal passed through the binarization circuit 8. Selector 7 is A
It is switched by the SEL signal.

As is generally known, images that have undergone halftone processing have good gradation, and are particularly effective in photographic images. In addition, not only photographic drawings but also line drawings can use halftone processing to create different densities in characters with shading. However, when a binary printer decides whether to print a dot or not based on a 1-bit manual signal of O or 1, and the density of each dot itself is uniform, pseudo-halftone processing is similar to a blurring effect. Therefore, sharpness is slightly degraded. For this reason, in the case of a film image consisting only of line drawings, it is better not to perform pseudo-halftone processing.

For this reason, the selector 7 can select whether to perform halftone processing or to perform binarization without halftone processing using the ^SEL signal. This selection processing instruction can be selectively selected by the user using function keys (not shown) on the keyboard 10.

■Other Embodiments In the first embodiment of the present invention described above, the γ correction circuit 4 is
Although the configuration is made of PROM, a rewritable FROM such as E2FROM may be used, or SRAM or the like may be used and data can be loaded from another PROM using CPtl or the like. In particular, since a high-speed reading system requires a high-speed memory, it is effective to use an SRAM or the like for the γ correction circuit 4.

Further, the γ correction data is not a particularly defined characteristic curve, and may be used also for logarithmic conversion, offset adjustment, etc., for example.

Further, in the first embodiment, a contact type image sensor is used as the image sensor, but a non-contact type CCD or the like may be used, or an area sensor may be used instead of a line sensor.

Furthermore, although the edge emphasis circuit and halftone processing circuit shown in the first embodiment described above are not particularly necessary conditions for the present invention, when a binary printer is used, some kind of halftone processing is required.

FIG. 7 shows the configuration of another embodiment of the present invention in which the printer is a multi-value printer (that is, a printer that determines the density of one dot based on an input signal of multi-bit data). Although there is no particular halftone processing circuit in this embodiment, in the case of a multilevel printer, the multilevel data itself can be expressed in halftones, so even the output data of the γ correction circuit 4 as it is can produce a tone with good reproducibility. This is because you can obtain tonality. Although the edge emphasis circuit 5 in this case is not particularly required in accordance with the gist of the present invention, as in the above-described first embodiment, this circuit 5
This allows the user to vary the sharpness.

Furthermore, the present invention can be applied to the case where a read image is reproduced and displayed on a display using a CRT, liquid crystal, etc. instead of a printer.

In addition, the generation of the N/P signal given to the γ correction circuit 4 in the first embodiment is selected by the user using a setting key.
Any self-initiated N/P discrimination using a film detection sensor (not shown) is possible, and the generation method is not limited.

In addition, in the case of N/P image area separation of an image, where some parts are negative images and others are positive images, as shown in Figure 8, the N/P signal can be converted to the image signal in real time. By doing so, it becomes possible to respond.

Furthermore, the present invention is not limited to monochrome (black and white) images, but can also be applied to color image reading devices. However, in this case, a circuit as shown in FIG. 2 is required for each color of R (red), G (green), and B (blue).

In addition, in the first embodiment, a binary printer was used as the printer, but this printer may be a laser beam printer (LBP), a thermal transfer printer, an inkjet printer, etc., but is not particularly limited; There may be cases where it is necessary to connect to the image reading device via memory or interface. [Effects of the Invention] As explained above, according to the present invention, in an image reading device used in a digital league printer, etc., optimal data can be obtained depending on the type of film, whether it is a negative film or a positive film. Correction characteristics (
γ curve), so negative film,
Output images with good gradation can be easily obtained from any of the standard films.

Furthermore, by inverting the γ curve itself in advance, there is also an advantage that there is no need to invert the image signal depending on the negative or positive film.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the basic configuration of an embodiment of the present invention, Figure 2 is a block diagram showing the circuit configuration of an embodiment of the present invention, and Figure 3 is a detailed example of the γ correction circuit in Figure 2. Block diagram; Figure 4 is a characteristic diagram showing an example of the γ curve of manual data and output data for positive film in the γ correction circuit in Figure 3; Figure 5 is for negative film in the γ correction circuit in Figure 3. A characteristic diagram showing an example of the γ curve of human input data and output data, FIG. 6 is an explanatory diagram showing an example of the convolution mask and mask coefficient used in the edge enhancement circuit of FIG. 2, and FIG. FIG. 8 is a block diagram showing the circuit configuration of the embodiment; FIG. 8 is an explanatory diagram showing processing details in still another embodiment of the present invention; FIG. 9 is a characteristic diagram showing the γ characteristics of the film. DESCRIPTION OF SYMBOLS 1... Image sensor, 2... Amplifier, 3... A/D converter, 4... γ correction circuit, 5... Edge emphasis circuit, 6... Halftone processing circuit, 7...・Selector, 8...Binarization circuit. Fig. l (A11-A14, d [connected to GND) Fig. 3 Fig. 4 Fig. 5 Fig. 7

Claims (1)

[Scope of Claims] 1) Imaging means for converting a formed original image into an electric signal; Digital conversion means for amplifying the electric signal and converting it into a digital signal; and whether the original image is a negative image. , an identification signal generating means for generating an identification signal indicating whether the image is a positive image; and data correction of the digital signal using data of a data correction characteristic selected from among a plurality of data correction characteristics according to the identification signal. An image reading device comprising: a data correction means; 2) The data correction means comprises a memory element in which conversion data related to the plurality of data correction characteristics are stored in advance, and performs the data correction process by performing a table lookup on the memory element. The image reading device according to item 1.