JPH0582107B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image processing device, and more particularly to a device that reads image light from a document using an image sensor and converts it into electricity.

FIG. 1 is a schematic diagram illustrating a conventional image processing device. 1 is a document that moves according to the reading speed of the image sensor. Light from the original passes through lens 2 and passes through dichroic filters 3 and 4.
The color-separated lights are projected onto image sensors 5, 6, and 7 and converted into electrical signals.

It is desirable for the projection magnification to be as large as possible, but due to limitations on the size of the image sensor, it is usually used at around 1/5 to 1/20, and if detailed reproduction is desired, it is 1/5 to 1/10. Used within the range of In this case, the allowable amount of color misalignment when reproducing the original is about 0.2 mm, and if it exceeds that, color misalignment will be visible to the naked eye, which is undesirable. When the magnification is 1/10, the color shift allowed by the image sensor is about 20 μm.

It is extremely difficult to adjust the arrangement of each image sensor within such permissible accuracy, and it has been impossible for the image processing apparatus to cause color misalignment due to installation errors of each image sensor.

The present invention has been made in view of the above points, and relates to a document reading device that prevents misalignment in reading a document during image processing.

In order to achieve the above object, the present invention includes a document table;
The document has an image sensor in which a plurality of photoelectric conversion elements are arranged in a line to illuminate the document placed on the document table and convert the image light obtained into an electrical signal, and the document image is read by the image sensor. The reading device includes a reading reference portion provided on the document table and readable by the image sensor, and when the image sensor reads a document image placed in a fixed positional relationship with the reading reference portion, the reading reference portion is provided with a reading reference portion. The present invention is characterized in that a reference signal from the corresponding image sensor is determined, and based on this reference signal, the processing timing of the document signal outputted from the image sensor in the direction in which the photoelectric conversion elements are arranged is determined. Incidentally, from the manuscript of the present invention, image light refers to not only a combination of color-separated light images having different wavelengths, but also such color-separated light images,
This also means the case of a combination with a light image that has not been color separated.

The details of the present invention will be explained below using specific examples.

FIG. 2 shows the document surface of the image processing apparatus of the present invention. For convenience, the following explanation will be given in the case where the projection magnification is 1/10 and the size per 1 bit of the image sensor is 15 μm. In FIG. 2, when the 8 document placement table surface is viewed from the back, a reference line 9 that serves as a document reading reference is drawn along the scan direction of the document at the end adjacent to the transparent surface on which the document is placed. It is. In this example, the reference lines each have a line width of 0.1
mm, and three lines are drawn with a center-to-center distance of 0.225 mm.

FIG. 3 shows a partial cross section of the surface of the original document mounting table. Reference numeral 11 denotes a transparent glass constituting the document placement surface 8, on which the document 10 is placed. Reference numeral 12 denotes a plate on which a reference line 9 is printed, and is fixed onto the transparent glass using a pressing member 13 so as to maintain a fixed positional relationship with the transparent glass 11. This pressing member 13 is 12
It also serves as a reference when placing the manuscript 10.

FIG. 4 shows the relationship between an optical image and an electrical signal when projected onto each image sensor using a projection system similar to that shown in FIG. 1. A shows a corresponding image 9' and a figure 10' of the original when the reference line 9 and the original 10 are projected onto the image sensor. X is a direction axis perpendicular to the original scanning direction (arrow) in FIG. b is an image sensor equipped with a plurality of photoelectric conversion elements arranged in a line, and each small window corresponds to 1 bit. For convenience of explanation, numbers 1 to 14 are assigned as addresses for each bit. The image sensor used is a MOS type image sensor or a CCD. c is the output when the image a is projected onto the image sensor. The left line 9 ₁ ' of the reference line 9' corresponds to the 2nd bit of the image sensor, so the 2nd bit is output dark. On the other hand, the middle line 9 ₂ ' corresponds to the 3rd and 4th bits, so intermediate values are input to each. Line 9 ₃ ' on the right side appears in the 5th bit, so it is output darkly. The same applies to the original figure 10'. This is binarized using a certain threshold and is d
It is. Looking at the reference line of this signal
01101 is projected with a 1/2 bit shift,
The output will be 11011. From the way this signal is output, it can be determined which of the three reference lines is being read by the image sensor, either at both ends or in the middle.

When the lines 9 ₁ ′ and 9 ₃ ′ at both ends are being read by the photoelectric conversion elements 2 and 5 in the image sensor, the processing of the original signal is set to start, for example, at the 4th bit from the reference line signal. When the middle line 9 ₂ ' is being read with such settings, processing of the original signal starts at the 5th bit of the reference line signal. If the start timing of document signal processing is set while determining the reference line signal in this way, the reading position error can be kept within 1 bit. This means that it is possible to know the timing to process the original signal without color shift simply by determining how the image sensor is installed, reading out the reference line signal, and determining which line the signal belongs to. That is, each image sensor can be synchronized using the reference line signal. Further, if the relative relationship between the document and the reference line on the document placement surface is constant, the document can be read without waste. Therefore, no matter how many image sensors there are, each can be mounted at a position that receives the original optical image and the reference optical signal, and therefore, their mounting does not require much precision. Then, as in the above example, the positional relationship of those images can be kept within an error of 1 bit. Therefore, in this device
Since it is possible to keep the color shift within 0.15 mm, it is extremely good for practical use.

In the above example, three mark-containing members were installed on the document placement surface as members that emit reference optical signals.
To explain this, an independent illumination source may be provided without using the illumination light of the document placement surface. Moreover, instead of a mark member having a reflective part, a partially transparent part may be provided and a light source may be placed on the back side.

In the above-described specific example, the signal detected first by the image sensor among the input optical signals of each mark was used as the reference line. By the way, if there is a possibility of misreading due to dust on the document surface other than the mark member, it is necessary to use three or more reference lines in order to make the reading system recognize the reference line signal as the reference line, or It is also effective to widen the range and improve the accuracy of discrimination.

As described above in detail in the specific examples, the present invention is capable of processing the read signal from the image sensor without causing reading misalignment with respect to the original even if there is a mounting error in the image sensor. Therefore, when a color image is formed using the signals obtained by the image processing device, it is possible to form a good image without causing color misregistration.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram illustrating the configuration of an image processing apparatus according to the present invention, FIG. 2 is an explanatory diagram of a document placement surface of the processing device according to the present invention, and FIG. 3 is a portion of the document placement surface shown in the second figure. The cross-sectional view and FIG. 4 are schematic diagrams illustrating photoelectric conversion of image sensor input of the device of the present invention. In the figure, 1, 0: original, 2: lens, 3, 4: dichroic mirror, 5, 6, 7: image sensor, 8: original mounting table, 9: reference line (mark member).

Claims (1)

[Claims] 1. An image sensor comprising a document table and a plurality of photoelectric conversion elements arranged in a line that illuminates the document placed on the document table and converts image light obtained into an electrical signal. and a document reading device that reads a document image using the image sensor, the document reading device having a reading reference section provided on the document table and readable by the image sensor, the reading reference section being placed in a fixed positional relationship with the reading reference section by the image sensor. When reading a document image, a reference signal from the image sensor corresponding to the reading reference section is determined,
A document reading device characterized in that a processing timing of a document signal in the photoelectric conversion element array direction outputted from the image sensor is determined based on this reference signal. 2. The document reading device according to claim 1, wherein there are a plurality of image sensors, each of which reads a plurality of color component image lights from the document for each color.