JP2685565B2 - Image reading device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image reading apparatus for reading a color photographic original through a color separation filter in a copying apparatus, an image reading apparatus for plate making, and the like. An image reading method in which an electric signal related to image information is obtained by a photoelectric conversion element via a color separation filter to perform arithmetic processing, and image signal correction data corresponding to each color separation filter is created and stored in advance, and specified. When using the color separation filter of the above, by calling the image signal correction data corresponding to the color separation filter and processing the signal, the density fluctuation caused by the color separation filter and the photoelectric conversion element at the time of reading a color photographic document is suppressed. The present invention relates to an image reading device adapted to obtain an image signal.

BACKGROUND OF THE INVENTION For example, in the fields of printing and plate making, an image scanning recording / reproducing system for electrically processing image information carried on an original to create a film original plate for the purpose of streamlining work processes, improving image quality, etc. Is widely used.

This image scanning recording / reproducing system is basically composed of an image reading device and an image reproducing device. That is, in the image reading device, the image information of the original document which is sub-scanned and conveyed in one direction in the image reading unit is converted by the optical sensor into an electric signal which is main-scanned in a direction substantially orthogonal to the sub-scanning direction. Next, the image information photoelectrically converted by the image reading device is subjected to arithmetic processing such as gradation correction and edge enhancement according to plate making conditions, and then converted into an optical signal such as a laser beam in the image reproducing device to be converted into a film. Recording / reproduction is performed on an image record carrier made of a photosensitive material such as. The image recording carrier is developed by a predetermined developing device, and is used as a film original for printing or the like.

By the way, when a document is main-scanned and the image information is read in the image reading apparatus, a CCD in which a large number of photoelectric conversion units are arranged in a line along the main-scanning direction is used as an optical sensor.
(Charge coupled device) is adopted. Here, there is a method in which, when a color photographic original or the like is read and image processing is performed, the light is polarized by a condenser lens through a color separation filter and imaged on a CCD to obtain an electric signal related to image information. At this time, if a document of uniform density is read in the main scanning direction,
In reality, an electric signal related to faithful image information cannot be obtained. The factors are considered to be based on the following items.

Dispersion of illuminance of the light source that composes the original illumination system Cosine law of lens Dispersion of sensitivity of light receiving element (CCD) Transmittance of color separation filter In addition, these and other items are superimposed, and as a result, electrical signals related to image signals And mixed as a variation signal (hereinafter referred to as shading).

A conventional technique for correcting this type of shading is shown in FIG. That is, FIG. 1 is a block diagram of the image correction processing circuit 10 for explaining the principle of calculating the correction coefficient for the read image data, and the image correction processing circuit 10 introduces an electric signal related to the image signal. Multiplying D / A
It includes a converter 12, an A / D converter 14, a CPU 16, and a correction data memory 18.

To explain the operation of the image correction processing circuit 10, first,
A document of uniform density is read to obtain correction data. Specifically, an electric signal related to an image signal input to a light receiving element such as a CCD, that is, an analog electric signal including shading.
Input E _a to the multiplication type D / A converter 12. And the A
It is introduced into the CPU 16 via the / D converter 14, where it is arithmetically processed to obtain a correction coefficient according to the analog electric signal E _a relating to the image signal, and stored in the correction data memory 18 as digital data E _d . Next, when the actual image is read and reproduced, the digital data E _d read from the correction data memory 18 is fed back to the multiplication type D / A converter 12 to perform a desired shading correction.

Here, the operation of the multiplication D / A converter 12 will be described. That is, the operation is input signal × digital data × coefficient → output electric signal. The coefficient is a value determined by the circuit constant and the characteristics of the element used. That is, the output signal from the multiplication D / A converter 12 has a value proportional to the product of the analog electric signal E _a having shading related to the image signal and the digital data E _d calculated by the CPU 16.

The CPU 16 arithmetically processes the reciprocal of the analog electric signal E _a related to the image signal, and the image signal correction data D _r (see FIG. 2) related to the reciprocal is used as digital data E _d for the analog electric signal E related to the image signal. _The shading correction is achieved by supplying the multiplication type D / A converter 12 together with _a .

However, when the color separation filters for color originals are switched, it is not possible to perform correction even if the previous correction data is used because the transmittance differs depending on the color separation filters. In other words, changing the color separation filter changes the transmittance of light from the original, so when scanning an original of uniform density, CC
A constant light intensity is not obtained on D, and density fluctuation occurs in the reproduced output image. Therefore, every time the color separation filters are switched, it is necessary to read a manuscript having a uniform density and create correction data, which requires time for correction calculation, which makes it difficult to suppress production cost and production cost. Inconvenience is exposed.

[Object of the Invention] The present invention has been made in order to overcome the above inconveniences, and corresponds to each color separation filter in advance in an image reading method applied to a copying apparatus, an image reading apparatus for plate making, or the like. When creating and storing image signal correction data and using a specific color separation filter, the color separation filter for reading a color photo original by calling the image signal correction data corresponding to the color separation filter and processing the signal. Another object of the present invention is to provide an image reading apparatus capable of obtaining an image signal in which the density fluctuation caused by the photoelectric conversion element is suppressed.

[Means for Achieving the Object] In order to achieve the above object, the present invention illuminates a document with a light source and forms reflected light or transmitted light according to image information recorded on the document in an image forming optical system. In an image reading apparatus for image-forming and projecting on a photoelectric conversion element composed of a plurality of pixels via, and reading the image information by a signal output from the photoelectric conversion element, in an optical path between the photoelectric conversion element and the document. A plurality of color separation filters having different color separation characteristics configured to move forward and backward, and reflected light or transmitted light from an original having a uniform density are received by the photoelectric conversion element via the desired color separation filter. A plurality of storage means for creating and storing image signal correction data corresponding to the color separation filter for each pixel forming the photoelectric conversion element, and selecting a desired color separation filter. A photoelectric conversion unit for switching to the storage unit that stores the image signal correction data according to the selected color separation filter when the document image is actually read by inserting the optical signal into the optical path. The output signal for each pixel of the device is individually corrected by the image signal correction data read from the storage means switched by the switching means, and then is output to the image processing circuit.

[Embodiment] Next, a preferred embodiment of the image reading apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 shows a block diagram of an image signal correction processing circuit 20 for implementing the image reading apparatus according to the present embodiment. The image signal correction processing circuit 20 is a multiplication type D / A converter 22 for calculating image reading data and image signal correction data which are analog electric signals related to the image signal, and an A / D converter 24,
CP that calculates the reciprocal of the image reading data for a uniform-density original
A U26, selectors 28 and 30, and a correction data memory 32 that stores image signal correction data for each color separation filter. Further, an analog electric signal related to the image signal is introduced from the image reading unit 40 described later to the multiplication type D / A converter 22 which constitutes the image signal correction processing circuit 20.

The image reading section 40 includes a document table 42, a light source 44, a color separation filter 46, a condenser lens 48, and a light receiving element 50. The color separation filter 46 includes a driving unit 46a. The drive unit 46a
Outputs a selection signal of the color separation filter 46 to the CPU 26. The color separation filter 46 is composed of a plurality of color separation filters. A desired color separation filter is driven by an operation means and a drive mechanism (not shown) of the drive section 46a so that the desired color separation filter is arranged on the optical path. The light receiving element 50 is composed of a CCD.

In the image reading unit 40 having such a configuration, first, the color document S is placed on the document table 42, and the light illuminating the color document S from the light source 44 is reflected to pass through the color separation filter 46 and the condenser lens. The analog electric signal E ₁ related to the image signal is obtained by being condensed by 48 and being focused on the light receiving element 50. The multiplication D / A converter 22 receives the analog electric signal E ₁ and outputs it to the A / D converter 24.

Then, the analog electric signal E ₁ is converted into a digital signal and transmitted from the A / D converter 24 to the CPU 26.
At this time, a signal relating to selection of a specific color separation filter is introduced to the CPU 26 from the driving unit 46a of the plurality of color separation filters 46. Then, a signal for switching the selectors 28, 30 based on the color separation filter selection signal is sent from the CPU 26, and the correction data stored in the correction data memory 32 via the selector 30 is sent to the multiplication D / A converter 22. It is captured.

As will be described later, the correction data memory 32 stores in advance the number of color separation filters and the shading correction data corresponding to each color separation filter.

The image signal correction processing circuit for carrying out the image reading apparatus according to the present invention is basically constructed as described above. Next, referring to FIG. 3 based on the procedure shown in FIG. The operation of the image signal correction processing circuit 20 will be described below.

First, light of each color separation filter relating to an image signal from a document (preferably a white document) having a constant density is incident on the light receiving element 50, shading correction data is created based on this output signal, and stored in the correction data memory 32. Yes (STP1). That is, the image signal of the white original is input to each multiplication type D / A converter 22 for each color separation filter, and in the multiplication type D / A converter 22, the analog electric signal (E ₁ ) × digital data (D) × coefficient = Output signal (E ₀ ) is processed and A /
It is introduced into the CPU 26 via the D converter 24. At this time, a selection signal of a specific color separation filter is introduced from the drive unit 46a of the color separation filter 46 to the CPU 26, the selectors 28 and 30 are switched based on this selection signal, and a predetermined memory of the correction data memory 32 is selected. Connected to. And the CPU2
In step 6, the reciprocal number of the digital signal from the A / D converter 24 is calculated, and the reciprocal number of this digital signal is stored in a predetermined memory of the correction data memory 32 as the image signal correction data D _r of the specific color separation filter.

FIGS. 5A and 5B are graphs showing the relationship between the input data from the white original in the specific color separation filter and the reciprocal of the data as the image signal correction data. In this way, the image signal correction data D _r for each color separation filter is stored in the correction data memory 32.

Next, a process of actually image-processing the color original S will be described.

First, the color document S is placed on the document table 42 of the image reading section 40.
Is placed. Then, the operator inputs a signal for selecting a color separation filter by an operation means (not shown), and thereby the driving unit 46a of the color separation filter 46 connected to the operation means.
A color separation filter selection signal is introduced into. Next, based on this color separation filter selection signal, the color separation filter related to the color separation filter selection signal is switched and driven by a drive mechanism (not shown) so as to match the optical path of the image reading section 40 (ST.
P2). At this time, a color separation filter selection signal is input to the CPU 26 from the driving unit 46a. Next, the light source 44 is turned on to expose the color original S, and the reflected light from the color original S is passed through the selected color separation filter to the condensing lens 48.
The light is incident and condensed on and is image-projected on a light receiving element 50 composed of a CCD. Then, the received light 50 is converted into an analog electric signal E ₁ related to the image signal and input to the multiplication type D / A converter 22 of the image signal correction processing circuit 20.

By the way, as described above, the CPU 26 includes the image reading unit 40.
Since the color separation filter selection signal is input from the driving unit 46a of the color separation filter 46 in, the selectors 28 and 30 are switched based on this color separation filter selection signal,
It is connected to a predetermined memory in the correction data memory 32 (STP3). Thereby, it is possible to call the image signal correction data D _r depending on the particular color separation filter Multiplying with analog electric signals E ₁ according to the image signal correction data to the image signals having the shading as a digital signal D D / It is supplied to the A converter 22. Then, in the multiplication type D / A converter 22, an analog electric signal (E ₁ ) ×
Digital data (D) × coefficient = output signal E _{0 is} calculated to derive a signal with shading corrected as an output electric signal (STP4). And the A / D converter 24
Is converted into a digital signal by and output to an image processing circuit that performs gradation correction, edge enhancement, and the like.

As described above, in this embodiment, the process of image processing of a normal color original has been described. However, for example, pseudo color such as a two-color printed matter, that is, color separation of a color original is performed to create a plate for each color, and these are superimposed. Of course, it can be applied to a duotone technique such as printing.

[Effects of the Invention] As described above, according to the present invention, the reflected light or the transmitted light corresponding to the image information recorded on the document is transferred to the photoelectric conversion element through the predetermined number of color separation filters and the imaging optical system. In an image reading apparatus that image-projects onto the image reading device and reads the image information by a signal applied from the photoelectric conversion element, image signal correction data corresponding to the predetermined number of color separation filters is created in advance and stored in a storage unit. . Then, when a specific color separation filter is selected from the plurality of color separation filters and an original image is actually read, the image signal correction data corresponding to the selected color separation filter is read from the storage unit and the The output signal of the photoelectric conversion element is controlled to perform a predetermined calculation. For this reason, image processing is performed using shading data that is image signal correction data that is suitable for each color separation filter in order to suppress density variation due to the difference in transmittance of each color separation filter. Only by switching and selecting the memory, it is not necessary to obtain the correction data every time the color separation filters are switched. In addition, the time required for the correction calculation is suppressed, an image signal that is not affected by shading is obtained, and productivity is significantly improved. Therefore, it is possible to suppress the production cost.

The present invention has been described above with reference to the preferred embodiments, but the present invention is not limited to these embodiments, and various improvements and design changes can be made without departing from the gist of the present invention. Of course.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram for explaining a method of creating image signal correction data according to the prior art, and FIG. 2 is an input data and an image corresponding thereto in the method of creating image signal correction data shown in FIG. FIG. 3 is a block diagram showing the relationship of signal correction data, FIG. 3 is a block diagram of an image signal correction processing circuit for carrying out the image reading apparatus according to the present invention, and FIG. 4 is an explanation of the operation of the block diagram shown in FIG. FIG. 5 is a graph showing input data and image signal correction data in the image signal correction processing circuit shown in FIG. 20 …… Image signal correction processing circuit 22 …… Multiplying D / A converter 24 …… A / D converter, 26 …… CPU 28, 30 …… Selector, 32 …… Correction data memory 46 …… Color separation filter

Claims (1)

(57) [Claims] 1. A light source illuminates a document, and at the same time, reflected light or transmitted light corresponding to image information recorded on the document is image-projected onto a photoelectric conversion element composed of a plurality of pixels via an image-forming optical system, In an image reading device that reads the image information by a signal output from the photoelectric conversion element, a plurality of color separations having different color separation characteristics configured to be movable back and forth with respect to an optical path between the photoelectric conversion element and the document. The photoelectric conversion element receives the reflected light or the transmitted light from the original having a uniform density through the desired color separation filter, so that the image signal correction data corresponding to the color separation filter is received by the photoelectric conversion element. A plurality of storage means that are created and stored for each of the pixels that make up the above, and when the desired color separation filter is selected and inserted into the optical path to actually read the original image, Switching means for switching to the storage means for storing the image signal correction data according to the color separation filter that has been stored, and the storage device that has switched the output signal for each pixel of the photoelectric conversion element by the switching means. After individually correcting by the image signal correction data read from the means,
An image reading device which is derived to an image processing circuit.