JPS59216372A - Picture information reader - Google Patents

Abstract

PURPOSE:To attain a sufficient outline emphasizing effect with a simple device by utilizing MTF reduction of the output signal of a solid-state image pickup device using near infrared rays to obtain an optical blurred image. CONSTITUTION:The image of an original 1 is focused on a solid-state image pickup device 4 through a photographic lens 2 and a filter disc 3. This disc 3 is an incident light separating means and has a multilayered film, which cuts near infrared rays and permits visible rays to transmit through, arranged in a part (a) and has a multilayered film having the reverse characteristic arranged in a part (b). The disc 3 is rotated to obtain an unsharp signal in the part (b). A photo interrupter 9 is arranged across the outside edge part of the disc 3, and it is synchronized with pulses of an oscillator 5 by a gate controller 10. A main signal of the output of an A/D converter 7 and the unsharp signal are stored in memories A11 and B12 respectively by a multiplexer 8, and an unsharp mask signal is obtained by subtracting circuit 13. This signal is inputted together with the main signal to an adding circuit 14 to output an outline-emphasized signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image information reading device that improves sharpness by emphasizing the outline of an image using a blur mask method.

(Prior Art) Image information reading devices in digital copying machines, facsimile machines, etc. scan a document with a solid-state image sensor such as a CCD5MO8, photoelectrically convert the image information, convert it into an electrical signal, and output it. In order to improve the sharpness of the image, a method has been adopted in which the electrical signal is processed by a peaking method to enhance the outline of the image. however,
With such a method, contour enhancement only in the main scanning direction cannot be obtained.

In addition, the blur mask method, which uses an optically blurred image to enhance contours, has the advantage of being able to perform two-dimensional, fine-grained, and simple image processing. For example, JP-A-56-32
A device disclosed in Japanese Patent No. 869 is known.

However, in the disclosed apparatus, a frosted glass diffuser plate or a liquid crystal plate is used as a means for obtaining an optically blurred image for enhancing the outline of an image, so it is difficult to obtain an effective blurred image. It is necessary to increase the diffusivity of light, and as a result, the illuminance on the surface of the photographing element that receives the blurred image decreases, making it impossible to obtain a sufficient contour enhancement effect.

Furthermore, in the device disclosed in Japanese Patent Application Laid-Open No. 56-32870, one optical image is divided into two by a half mirror, each of the two optical images is read by two image sensors, and a difference is created in the optical path length. Since the blurred image is read by one of the image sensors, there is a problem in that the magnification is different between the blurred image and the in-focus main image. Further, in order to correct this magnification, when a correction lens is disposed in the optical path for obtaining a blurred image, there is a problem in that it is difficult to downsize and simplify the apparatus.

(Objective of the Invention) The present invention was made to solve the above-mentioned problems, and it is possible to obtain a blurred image by using a solid-state image sensor such as a CCD by image exposure using near-infrared light. MT of output signal
F (Modulation TransferFu
The purpose of this invention is to obtain a sufficient effect of enhancing the contours of an image with a simple device by utilizing the lowering of the contour of the image. Therefore, the edge enhancement effect of the present invention is particularly effective for improving the sharpness of black original images that provide good exposure contrast in the near-infrared light region, and for selectively improving the sharpness of black parts of multicolor images. be.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of the present invention. 1 is a document, which moves in the direction of the arrow. The reflected light from the original 1 passes through a photographic lens 2 and a multilayer filter disk 3, and forms an image on a solid-state image sensor 4 such as a COD, thereby forming original read image data.

The formed image data is sequentially transferred row by row in synchronization with a clock pulse from an oscillator 5 (see FIG. 4, which will be described later), amplified by an amplifier 6, and then converted into, for example, 8-bit data by an A/D converter 7. into a digital image signal.

FIG. 2 is a plan view of the filter disk 3, and FIG. 3 is a relative sensitivity characteristic diagram of light wavelength versus transmittance and light wavelength versus COD. The filter disk 3 is a means for separating incident light and is made of a transparent glass circle, and in part a, a multilayer film that cuts near-infrared light and transmits visible light and has a spectral transmittance shown by curve A in FIG. In part b of the plate 3, multilayer films that transmit near-infrared light and cut visible light, each having a spectral transmittance shown by curve B in FIG. 3, are alternately arranged by vapor deposition. The wavelength at the intersection of both curves A and B is approximately 700 nm. Moreover, part C in FIG. 3 shows a blacked out part.

The filter disk 3 is rotated just in front of the image sensor 4, and the light image transmitted through the section a of the filter 3 causes the output signal of the image sensor 4 to become the main image signal of the in-focus image. Further, the output signal of the image sensor 4 obtained by imaging the light that has passed through the section b of the firJ filter 3 becomes an unsharp signal of a blurred image.

A photointerrupter 9 is disposed so as to straddle the outer edge of the filter disc 3, and detects the difference between the 0 part (blacked part) and the space part of the disc 3, and uses the detection signal to The gate controller 10 is used to synchronize with the clock pulse, the multiplexer 8 switches the output of the A/D converter 7, and the page memory A11 or unsharp memory stores the main image signal for one page of document information. The signal is stored in the page memory B12.

FIG. 4 shows the timing of switching between the memory A11 and the memory B12 of the multiplexer 8 with respect to the clock pulse signal.

In this case, by appropriately selecting the sharp cut wavelength of the spectral transmission envelope MA and B of each vapor deposited film a and b part 3 of the filter disk 3 (approximately near 00 nm in this example), an unsharp signal can be obtained. Characteristics can be adjusted.

The main signal and unsharp signal once stored in the memory A11 and the memory B12 are taken out according to the signal generated from the read clock generator 15 by the print signal 16 issued by the print command when writing an image, and are taken out by the subtraction circuit. 13, the difference (main signal - unsharp signal) is output, and this becomes an unsharp mask signal. On the other hand, the main image signal from the memory A11 and the unsharp mask signal from the subtraction circuit 13 are input to the addition circuit 14, and an edge-enhanced signal is output. This signal is supplied to an output device such as a laser beam printer through a data selector, a dither pattern comparison circuit, and a parallel-to-serial conversion circuit, so that an image with enhanced contours is output.

Next, the reason why an unsharp signal is obtained by image exposure using near-infrared light as described above will be explained.

FIG. 5 shows a characteristic diagram of resolution versus MTF for each wavelength of the CCD. The MTF decreases when the wavelength is 700 nm or more, but this is because as the optical wavelength becomes longer, the absorption coefficient of the COD silicon substrate decreases, and most of the light is absorbed deep outside the depletion layer, resulting in signal charges. This is because the lateral diffusion effect of charges becomes large.

As shown in the C curve in Figure 3, the spectral sensitivity of the CCD is sufficient up to about 900 nm, and when a halogen lamp is used for document illumination, the spectral energy of the halogen lamp is on the long wavelength side. Since it is abundant, it can be used effectively up to a practical sensitivity of about 1000 nm. However, in the present invention, in order to make the magnification the same or the same between image exposures of visible light and near-infrared light, it is necessary to reduce the chromatic aberration of the photographing lens between the two image exposures. In order to reduce this chromatic aberration, it becomes difficult to design if the dominant wavelength of near-infrared light exceeds 900 nm, so long wavelength light exceeding 900 nm is cut in front of the photographic lens, and light with a wavelength of 900 nm or less is removed. It is desirable to provide a filter that transmits the

(Other Embodiments) FIG. 6 is a block diagram showing another embodiment of the present invention,
Components that are the same (equivalent) to those in FIG. 1 are indicated by the same reference numerals, and redundant explanation will be omitted. The guichroic mirror 3a is a means for separating incident light beams, and this mirror 3a transmits near-infrared light as shown in the transmittance curve in the light wavelength vs. reflectance and transmittance characteristic diagram in FIG. It also has visible light reflection characteristics shown in reflectance curve E in the same figure. The original 1 moves in the direction of the arrow, and the reflected light from the original 1 passes through the photographic lens 2 and is split into visible light and near-infrared light by the guichroic mirror 3a, and the visible light component is transmitted to the image sensor. CCD4
image to form in-focus document read image data. This image data, which becomes the main image signal, is sequentially transferred line by line in synchronization with the clock pulse from the oscillator 5.
After being amplified by the amplifier 6, the A/D converter 7
For example, it is converted into an 8-bit digital image signal.

On the other hand, the near-infrared light component transmitted by the guichroic mirror 3a is transmitted to the image sensor CCD4, which is the same as the image sensor 4.
A is imaged to form original read image data that becomes a blurred image. The image data that becomes this unsharp signal is
- The signal is sequentially transferred row by row in synchronization with the clock pulse from the oscillator 5, amplified by the amplifier 6a, and then converted into, for example, an 8-bit digital image signal by the A/D converter 7a. Further, the readout timing of the image pickup elements CCD4 and 4a is also synchronized with the clock pulse from the oscillator 5. The main image signal and unsharp signal output from the A/D converters 7 and 7a are input to a subtraction circuit 13, and the difference thereof is output, which becomes an unsharp mask signal. On the other hand, the main image signal from the A/D converter 7 and the unsharp mask signal from the subtraction circuit 13 are input to an addition circuit 14, which outputs an edge-enhanced signal.

(Effects of the Invention) As explained above, the present invention has a wavelength of abbreviation: (600~
Since the configuration is configured such that the outputs of the image sensor are obtained as a main image signal and an unsharp mask signal from visible light and near-infrared light, which are separated by a separation means with the border of 800) nm as a boundary, so that A particularly sufficient edge enhancement effect can be obtained for black original images, which can obtain good light contrast. In order to obtain a corresponding black image signal, since colored inks other than black on the original generally have a high reflectance of near-infrared light, it is necessary to appropriately select the spectral characteristics of the filter or dichroic mirror described above. , selectively outline the black part of the multicolor image'7
j? It is possible to selectively improve the sharpness and sharpness of black characters or lines in multicolor originals, further enhancing the effect of blackboard printing, allowing for high-level edge enhancement using a simple device. The present invention has the great effect of not increasing the size or complexity of the device as in the prior art.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a plan view of the filter disk, and Fig. 3 is the relative sensitivity of the optical wavelength versus transmittance and optical wavelength versus COD of the same filter. FIG. 4 is an oscillator clock pulse versus multiplex switching timing diagram, FIG. 5 is a resolution versus MTF characteristic diagram for each wavelength of COD, and FIG. 6 is a diagram of another embodiment of the present invention. The block diagram, FIG. 7, is a characteristic diagram of reflectance and transmittance versus light wavelength of the dichroic mirror. １・・・・・・・・・・・・・・・Manuscript 2・・・・・・・・・
・・・・・・・・・Photography lens 3・・・・・・・・・
・・・・・・Filter disc a, b・・・・・・Multilayer film

Claims (3)

[Claims] (1) An imaging means and a separation means for dividing light incident on the imaging means into near-infrared light and visible light other than the near-infrared light are provided, and the divided visible light and near-infrared light are separated. Accordingly,
An image information reading device characterized in that a main image signal of an in-focus image and an unsharp signal of a blurred image are obtained from the imaging means. (2) The image information reading device according to claim 1, wherein the separating means is two filters that individually transmit only the visible light and the near-infrared light. (3) The image information reading device according to claim 1, wherein the separation means is one dichroic mirror that reflects and transmits only the visible light and the near-infrared light.