JPH0494257A - Picture reader - Google Patents

Abstract

PURPOSE:To input a picture without losing picture information of an original by eliminating the effect of a reflected light from other area of the original invaded in an optical path reaching a photoelectric conversion element from a read picture element being a cause to level fluctuation of a read picture. CONSTITUTION:An illumination light from a light source 2 lights an area including a read picture element, a reflected light, from a picture element is formed on a charge coupled device(CCD) sensor 4 through a lens array 3 to obtain a picture output including the effect of a stray light. Then a shield film 7 is used to shut a reflected light from the read picture element and to obtain an output. On the other hand, only the read picture element is not shielded in the main scanning direction, but only a slight width toward the subscanning direction exists and almost all stray lights are detected. The output is decreased by one line from the usual read output to obtain an output from which the effect of stray light is eliminated. Thus, the reading with high accuracy without being effected with a reflectance of other area of the original is implemented.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an image reading device, and more particularly to an image reading device that can capture image information with high precision.

2. Description of the Related Art A photoelectric conversion element such as a CCD sensor is used to read an input i-striped image in a copying machine, facsimile, image file device, etc. These photoelectric conversion elements have a one-line configuration and are equipped with enough cells to read II with a resolution of several to several tens of water.The reading of the 0 image is done by electrical scanning (main scanning) in the line direction; This is performed by moving the entire photoelectric conversion element in the vertical direction (sub-scanning).

As an example of such an image reading device, for example, Japanese Patent Laid-Open No. 6
It is described in Japanese Patent No. 2-235872.

In the above-mentioned image reading device, there are factors that cause fluctuations in the reading level when reading a document.
There is a phenomenon in which the actual brightness (reflectance) of a certain point is influenced by the brightness of its surroundings. This is because the illumination for reading the document is applied to an area having a certain area including the point to be read, and the diffused reflected light from the surrounding document surface becomes a secondary light source. The light from this secondary light source gets mixed into the optical path from the normal reading point to the sensor, and is sensed by the sensor as a level change. For this reason, a pale black area within an entirely white area is read brighter than it actually is. For example, black text on a white background is affected by the white background, and the black becomes lighter or the edges become duller, making it difficult to read as a clear black text, or a certain size area transitions from white to black (black to white). Even when the image is scanned, the edges are blurred without being sharp, resulting in a read image that lacks fine image information.

Purpose The present invention was made in view of the above-mentioned circumstances.
The influence of reflected light from other areas of the JM manuscript that gets mixed into the optical path from the read pixel to the photoelectric conversion element, which causes level fluctuations in the read image, can be reduced by blocking the reflected light from only that pixel on the output of the photoelectric conversion element. The purpose of this invention is to provide an image reading device that can input an image without damaging the image information of a document.

In order to achieve the above object, the present invention provides (1) an image reading device that uses a photoelectric conversion element to obtain an electric signal according to the density of the original as an image signal, which is located almost close to a pixel of the original to be read; and a subtraction means for inputting the output of the photoelectric conversion element obtained by setting the brightness of the pixel seen from the photoelectric conversion element to approximately zero to a negative input, inputting the output of the photoelectric conversion element of the pixel obtained without substantially using a shielding means to the positive input of the subtraction means, and using the output of the subtraction means as an image signal output; or (2) An image reading device that obtains an electric signal according to the density of a document as an image signal using a photoelectric conversion element includes a shielding means provided substantially close to a pixel of a document to be read and blocking light reflected from the pixel, and a first photoelectric conversion device. a subtraction means for inputting the output of the first photoelectric conversion element, which is obtained by setting the brightness of the pixel seen from the element to approximately zero, into a negative input; the output of the second photoelectric conversion element is input to the positive input of the subtraction means, and the output of the subtraction means is used as an image signal output. be. Hereinafter, the present invention will be explained based on examples.

The above purpose is to obtain the sensor output by blocking the reflected light from the normally read pixels in a certain way, to obtain only the components detected by the sensor by the secondary light source, and to store this in the memory. This can be achieved by subtracting from the readout output (which is the output of the normal pixel information plus the influence of the secondary light source).

If we consider a state in which information from a certain pixel is being read, if we block the optical path from that pixel to the sensor as close to the pixel as possible, so that the entire sensor becomes completely black, the sensor's The output should be zero. However, in reality, a certain way of appearance occurs depending on the brightness around the pixel. This can be considered to be because almost all of the diffusely reflected light from the surrounding document surface wraps around the sensor input through some route and is sensed (this light is hereinafter referred to as stray light). Therefore, in order to detect the influence of a secondary light source on a read pixel, it is sufficient to intercept only the reflected light from that pixel near the pixel and observe the sensor output. The normal reading output is affected by the secondary light source, so if you subtract the above output from this output, you get
Document information that is not affected by secondary light sources can be obtained.

FIGS. 1(a) and 1(b) are configuration diagrams for explaining an embodiment of an image reading device according to the present invention, and in the figures, 1 indicates a document (
2 is the light source, 3 is the lens array, 4 is C
CD (charge coupled device)
: charge-coupled device) sensor, 5 is a carriage, 6 is a transparent film, 7 is a light shield surface (linear in the main scanning direction) with the width of a pixel, and the other parts are transparent films (hereinafter referred to as shield films).
It is. Figure 1(a) shows the normal reading state (with the influence of stray light), with the horizontal direction being sub-scanning,
The direction perpendicular to the plane of the paper is the main scan, and the carriage 5 carries a light source 2, a lens array 3, a CCD sensor 4. It moves together with the transparent film 6 and the shield film 7. Illumination light from a light source 2 illuminates a region including read pixels, and the reflected light from the pixels passes through a lens array 3 and forms an image on a CCD sensor 4 . As a result, an image output including the influence of stray light can be obtained as shown in FIG. 10(b). As shown in FIG. 10(b), the influence of stray light appears several times in the main scanning direction. FIG. 1(b) shows a state in which only the influence of stray light is detected. That is, the shield film 7 instead of the transparent film 6
is used to block the reflected light from the reading pixels to obtain output. The shield width of the shield film 7 is set to be the same as the pixel width in the sub-scanning direction. Moreover, it has a linear shape in the main scanning direction. Although it does not mean that only the pixels to be read are shielded in the main scanning direction, there is a small amount of ff1i in the sub-scanning direction.
(approximately 63 μm at 400 dpi), and Fig. 10 (
As shown in c), almost all stray light can be detected. By storing one line of this output in a storage means to be described later and subtracting it from the normal reading output described above, an output from which the influence of stray light has been removed is obtained as shown in FIG. 10(a). be able to.

FIGS. 2(a) and 2(b) are diagrams showing other embodiments of the image reading device according to the present invention. In the figures, 8 indicates an area corresponding to one row of pixels in two states: transparent and shielded. Other parts of the switchable membrane (hereinafter referred to as switching membrane) that have the same functions as in FIG. 1 are given the same reference numerals as in FIG. 1.

The switching film 8 uses liquid crystal, for example. This is also possible by using a polarizing plate. This switching is shown in Figure 2 (b
), it is performed linearly at once in the main scanning direction. As a result, stray light is detected in the shielded state, its output is stored in the storage means, normal reading is performed in the transparent state, and the stray light component stored in the storage means is subtracted from this output to detect the stray light. It is possible to obtain one line of image output from which the influence of light has been removed. In this embodiment, since the switching film 8 has no movable parts, it is possible to perform shielding with high precision, and thereby the stray light component corresponding to the pixel can be detected with high precision.

FIG. 3 is a diagram showing another embodiment of the image reading device according to the present invention, in which 11 is a light source, 12 is a lens array, 13a, 1
3b is a CCD sensor (there are two photosensitive sections (pixel rows)).

), 14 is a carriage, 15 has a shield portion only in an area corresponding to one row of pixels, and the other portions are transparent films. In this embodiment, one pixel column 13a performs normal reading, and the other pixel column 13b detects stray light at the same time. Correspondingly, the membrane 15
A transparent portion and a shield portion are provided.

These eliminate the need to independently set the time for detecting stray light, which saves reading time.Since the zero pixel rows 13a and 13b are separated by several lines, the output component of stray light It is also necessary to prepare the same number of lines for the storage means and delay the stray light components corresponding to the same reading position to subtract from the normal reading output.

FIGS. 4(a) and 4(b) are diagrams showing other embodiments of the image reading device according to the present invention. FIG. 4(a) shows a normal image reading state, and FIG. 4(b) shows stray light. Indicates the state to be detected.

In the figure, 16 is a light source, 17 is an imaging lens, 18 is a CCD sensor, 19 is a transparent film, and 20 is a shield film. The difference from the embodiment shown in FIG. 1 is that an imaging lens 17 is used in place of the lens array 3, and the original image is reduced and formed on the CCD sensor 18. In this embodiment as well, the influence of stray light can be removed similarly to the embodiment shown in FIG.

5(a) and 5(b) are diagrams showing other embodiments of the image reading device according to the present invention, in which reference numeral 21 denotes a switching membrane, and other parts having the same functions as in FIG. 4 have the same references as in FIG. 4. It is numbered. The difference from the embodiment shown in FIG. 2 is that an imaging lens 17 is used in place of the lens array 3, and the original image is reduced and formed on the CCD sensor 18. The switching film 21, like the film 8, switches between transmission and shielding states, thereby making it possible to eliminate the influence of stray light in the same manner as in the embodiment shown in FIG.

FIG. 6 is a diagram showing another embodiment of the image reading device according to the present invention, in which 24 is a light source, 25 is an imaging lens, and 26a
, 26b is a CCD sensor (having two photosensitive sections (pixel columns)), and 27 is a film similar to the film 15. The difference from the embodiment shown in FIG. 3 is that an imaging lens 25 is used instead of the lens array 3 to reduce the original image and form it on the CCD sensor 26. Other parts are similar to the embodiment shown in FIG.

FIG. 7 is a diagram showing another embodiment of the image reading device according to the present invention, in which 28 is a light source, 29 is an imaging lens, and 30
A to 30F are CCD sensors (with 6 photosensitive parts (pixel columns)), 31 has a shield part only in the area corresponding to every third pixel column, and the other part is a transparent film. be. The difference from the embodiment shown in FIG. 6 is that the CCD sensor 30 is a color sensor. For example, pixel rows 30a, 3
One pixel row 30c with 0b as a sensor for reading the R component.

30d is a sensor that reads the G component, pixel rows 30e,
30f is a sensor that reads the B component.

As a result, a normal image output and a stray light component can be obtained for each color component, and by finding the difference between these for each color, color image information from which the influence of stray light has been removed can be obtained.

8(a) and 8(b) are diagrams showing other embodiments of the image reading device according to the present invention, in which 32 is a light source, 33 is an imaging lens, and 34a to 34c are CCD sensors (3 35 is a transparent film, and 36 is a shield film having three rows of shield portions corresponding to the three pixel rows 34a to 30C. FIG. 8(a) shows a normal image reading state, and FIG. 8(b) shows a state in which stray light is detected. The difference from the embodiment shown in FIG. 4 is that a color CCD sensor 34 is used instead of the CCD sensor 18, making it compatible with a color image reading device. Along with this, 1
Instead of the shield film 20 having a row of shield parts, a shield film 36 having three rows of shield parts is used6.For example, the pixel row 34a is used for reading the R component,
b is used for reading the G component, pixel row 34c is used for reading the B component, and the stray light component is stored in the storage means.

By subtracting the stray light component read from the storage means from the normal image reading output, color image information from which the influence of stray light has been removed can be obtained.

9(a) and 9(b) are views showing other embodiments of the image reading device according to the present invention. In FIG. 9, 37 is a light source, 38 is an imaging lens, and 39a to 39c are similar to the CCD sensor 34. The color CCD sensor 40 is a switching film that can be switched between transmission and shielding in three row areas corresponding to the three pixel rows 39a to 39c, and the other portions are transparent. The difference from the embodiment shown in FIG. 5 is that a color CCD sensor 39 is used instead of the CCD sensor 18, making it compatible with a color image reading device.

FIG. 11 is a diagram showing an embodiment of a signal processing circuit used in an image reading device according to the present invention, and in the figure, 43 is a CCD.
44 is an analog signal processing circuit, 45 is an A/D conversion circuit, 46 is a switching circuit, 47 is a memory for storing stray light components, and 48 is a subtraction circuit. First, stray light is detected. The analog signal processing circuit 44 is required to transfer the output of the CCD sensor 43 and remove the lock component.
Perform predetermined analog processing such as sample hold with A/
The signal is guided to a D conversion circuit 45 and converted into a digital signal. This output is set to the switching position opposite to that shown in the figure, and the analog signal processing circuit 44. A/
The signal is led to a subtraction circuit 48 via a D conversion circuit 45 with a switching circuit 46 at the switching position shown. A subtraction circuit 48 subtracts the output read from the stray optical memory 47. As a result, the image reading component with the influence of stray light removed is 1
You can get line minutes. Similarly, for the next line, the stray light component is stored and subtracted from the normal image reading component, and the process is repeated for each line. This signal processing is shown in Figures 1, 2, 4, 5, and 8 (for each color).
It can be applied to the embodiment shown in FIG. 9 (for each color).

FIG. 12 is a diagram showing another embodiment of the signal processing circuit used in the image reading device according to the present invention, in which 49 is a CC
D sensor, 50.51 is an analog signal processing circuit, 52.
53 is an A/D conversion circuit, 54 is a memory for storing stray light components, and 55 is a subtraction circuit. In this embodiment, the stray light component is subjected to signal processing through a path of an analog signal processing circuit 50 and an A/D conversion circuit 52, and its output is stored in a stray light memory 54. Also, the analog signal processing circuit 5
1. The normal image reading component is signal-processed in the path of the A/D conversion circuit 53, and its output is guided to the subtraction circuit 55. The subtraction circuit 55 extracts the stray light component corresponding to the line currently being read from the stray light memory 54. is read out and subtracted from the output of the A/D conversion circuit 53. This makes it possible to obtain an image reading method that eliminates the influence of stray light. This signal processing can read out the stray light component and the normal image reading component at the same time as shown in Figure 3.
It can be applied to the embodiments shown in FIGS. 6 and 7 (for each color).

Effects As is clear from the above explanation, according to the present invention, the influence of reflected light from other areas of the document that gets mixed into the optical path from the reading pixel to the photoelectric conversion element, which causes level fluctuations in the read image, can be reduced. By blocking the reflected light from only the pixels, the output of the photoelectric conversion element can be obtained. By subtracting this output from the photoelectric conversion output obtained by reading using the normal method, the reflectance of other areas of the document can be adjusted. Highly accurate image reading is possible without being affected.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram for explaining one embodiment of an image reading device according to the present invention, FIGS. 2 to 9 are diagrams showing other embodiments of the image reading device according to the present invention, and FIG. is the first
FIG. 11 is a diagram showing an example of the signal processing circuit used in the image reading device according to the present invention, and FIG. 12 is a diagram showing the image output in the embodiment shown in the figure. FIG. 3 is a diagram showing another example of the signal processing circuit used. 1... Original, 2... Light source, 3... Lens array,
4... CCD sensor, 5... Carriage, 6...
Transparent film, 7... Shield film. Figure 1 (a) (b) Figure 2 (a) (b)!

Claims (1)

[Scope of Claims] 1. In an image reading device that uses a photoelectric conversion element to obtain an electrical signal according to the density of a document as an image signal, a shielding device is provided substantially close to a pixel of the document to be read and blocks light reflected from the pixel. and a subtraction means for inputting the output of the photoelectric conversion element obtained by setting the brightness of the pixel expected from the photoelectric conversion element to approximately zero to a negative input, and the pixel is obtained substantially without using the shielding means. An image reading device characterized in that the output of the photoelectric conversion element is input to the positive input of the subtraction means, and the output of the subtraction means is used as an image signal output. 2. In an image reading device that obtains an electric signal according to the density of a document as an image signal using a photoelectric conversion element, a first shielding means is provided substantially close to a pixel of the document to be read and blocks reflected light from the pixel; subtraction means for inputting the output of the first photoelectric conversion element, which is obtained by setting the brightness of the pixel seen from the photoelectric conversion element to approximately zero, into a negative input; and photoelectric conversion of the pixel without substantially using the shielding means. The second to get the output
1. An image reading device comprising: a photoelectric conversion element; the output of the second photoelectric conversion element is input to the positive input of the subtraction means; and the output of the subtraction means is used as an image signal output.