JPS6282876A - Picture reader - Google Patents

Abstract

PURPOSE:To read out precisely images even if the length between reading elements is changed by changing a picture element position for processing picture element data in an overlap part as an effective picture element data in accordance with the expansion/contraction of a base which is operated from a detected temperature. CONSTITUTION:When the temperature 20 deg.C of the base is detected by a thermis tor 19, the temperature information is inputted to a CPU 21 and a correcting table in a RAM 26 is referred. As the result, the generation of expansion corre sponding to 9 picture elements is decided by a CPU 21 and a position for processing the picture element data as effective picture element data is changed. Namely, the 9 picture elements are divided into 4 picture elements and 5 picture elements and the processing position is changed so that data up to No.4979 becomes an effective picture element data to reading picture element data in the CCD 7 and succeeding data from the element No.21 becomes an effective reading picture element data in the CCD 8. The position changing data are selected from the correction table under control by the CPU 21 and applied to shfit memories 24, 25 and the position is changed by setting up the initial and final addresses at the time of reading.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an image reading device such as a digital copying machine that reads an original image as digital information using a reading element such as a COD.

2. Description of the Related Art In general, digital image reading apparatuses that expose original images to slits and read them with an image reading element such as a CCD are capable of performing various image editing processes compared to analog copying machines and the like.

In this case, in order to obtain an image comparable to an analog system image in a digital image reading device, it is necessary to increase the pixel density. Also, the original image size is A
1. In the case of a large size drawing such as an AO size drawing, the number of pixels is large, and a single COD is insufficient in the number of pixels. That is.

The maximum number of pixels of COD currently available is 5o00 elements, and assuming a pixel density of 16 PIXEI-/w+,
Limited to original images of approximately 300 nn+width. Therefore, for example, an AO size original image with a width of 841 m has a pixel density of 16
When reading with PIXEL/mm, the required number of pixels is 841x16=18456pxxEt, so 3
It is necessary to use several CODs. Here, the COD light receiving element pitch is 7μ, and the document reading pixel density is 16 PIX.
Assuming EL/mm, the projection magnification m of the original image on the COD is m = b / a, where the distance between the original and the lens is a, and the distance between the lens and the CCD is b, and specifically, approximately 1/ It becomes 8.926.

Now, as shown in FIG. 5, A with a width f10=841+nm
The image of O size document 1 (pixel count 13456) is 3 C0D2 with 5000 elements at pitch α = 280ml -
In order to read the data by arranging them in a row, it is necessary to arrange three CCDs 2 with an overlap dimension ΔQ of 130 pxxEL as shown in the figure, so as not to cause image loss between the joints of the CCDs 2. These overlapping pixels are processed as a series of non-overlapping image signals by deleting the number of image signal data read out from each CCD 2.

In addition, in FIG. 5, 3 is a lens, 4 is a board for mounting the CCD 2, 5 is a lamp for exposing the original 1 to slit light, and 6
is the side plate.

Here, if the substrate 4 is a general structural steel plate, its thermal expansion coefficient is about 11XIO-'', and the temperature change of the device is 20
℃, the mounting pitch of CCD2 is Q1=280
na4t280X20X11X10-'=0.062m
This results in a dimensional change of m.

This length corresponds to approximately nine light receiving elements of the CCD 2. Also, when converted to the dimensions on original 1, it is 0.062X8.9
This corresponds to 26=0.553m. Such temperature changes include not only changes in room temperature but also temperature increases caused by power sources, lamps, etc. inside the device. In any case, the number of overlapping elements may be determined on a case-by-case basis depending on the temperature conditions used, but this is not preferred from the viewpoint of operability. Therefore, the amount of overlap is fixed based on the standard temperature.

However, when image processing is performed using such a fixed amount of overlap, for example, the CCD 2 must be installed at a pitch of 0.
06211III If it is expanded or contracted, it will be 0.0 on original 1.
Image information for the seam portion of 553 mm will be missing. Furthermore, if the pitch is reduced during installation, duplicate image information will be generated at the joint. Therefore, the measures against temperature changes are insufficient, and accurate image reading cannot be performed, making it unusable.

In this respect, the substrate 4 has a low coefficient of thermal expansion, for example, INV.
Even if an AR thermal expansion coefficient of 1.2×10'' is used, the accuracy is insufficient and the cost is also disadvantageous.

As a dimension correction method based on temperature, a temperature correction structure for the pendulum length of a pendulum clock is known, but this method is used for COD that requires precision.
There is no example of the installation of this method being applied to a structure.

In any case, practically the pixel pitch of CCD2 is 17
It is desirable to suppress the error to 2 or less.

Further, it is also necessary to integrate the CCD 2 and the lens 3 and attach them to the substrate 4 so that the relative positional relationship between them is kept constant.

Purpose The present invention has been made in view of the above points, and the present invention has been made in such a way that even if the mounting distance of a plurality of reading elements changes due to temperature changes, there is no loss or duplication of read data at the joint portion of each reading element. An object of the present invention is to obtain an image reading device that can perform reading processing.

Structure In order to achieve the above object, the present invention arranges a plurality of reading elements for digitally reading images on a substrate in a straight line, provides an overlapping part for the pixels read by each reading element, and In an image reading device in which the read pixel data up to each set position of the read pixel data is treated as valid pixel data and seam processing between each reading element is performed, a temperature detector is installed on the substrate to detect the temperature of this substrate. The invention is characterized by comprising a calculation control means for calculating the expansion and contraction of the substrate from the detected temperature of the substrate and changing the pixel position at which the read pixel data in the overlapped area is processed as valid pixel data in accordance with the expansion and contraction. It is something to do.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. Basically, the structure is the same as that shown in FIG. 5, but to simplify the explanation, two CCDs 7.8 are arranged on the substrate 9 in a straight line as shown in FIG. Consider the case where it is placed. 10 is a document, and 11 is an imaging lens.

The reading area of the document 10 based on these C0D7.8 has an overlapping portion 12 having a length ΔΩ. Here, in this example, the number of elements is 5000.
0D7.8 is used, and when the temperature of the substrate 9 is 0° C., the number of overlapping pixels between the CCD 7 and the CCD 8 is 50 as shown in FIG. 2(a). That is, the element Nα of CG, D7 is 49.50 to 500
0 and the elements 1 to 50 of the CCD 8 overlap.

In this embodiment, a thermistor 13 is provided on the substrate 9 as a temperature detector for detecting the temperature of the substrate 9. As shown in FIG. 3, this thermistor 13 forms a bridge circuit 14 with three resistors, and the output thereof is applied to an A/D converter 16 via an OP amplifier 15 to detect the temperature. ing. Here, the temperature ('C) - output voltage Vo (V) characteristic of the thermistor 13 of this embodiment is shown in the table below. It is set to produce a digital output of 50 to 0 corresponding to a temperature of 100°C.

Furthermore, an amplifier 17.1 is connected to the output side of the C0D7.8.
A/D converters 19 and 20 are connected via 8, and the read image information is converted into a digital signal. These A
The outputs from the /D converters 19 and 20 are compared with a predetermined value given by the CPU 21 (single threshold data for character information, dither data for pictures, photo manuscripts, etc.) by comparators 22 and 23, respectively. The signals are binarized, sent to shift memories 24 and 25, and output from these shift memories 24 and 25.

Here, the CPU 2]- serves as an arithmetic control means, and is connected to a ROM 26 and a RAM 27. The substrate 9 to which the CCD 7.8 is attached expands and contracts depending on the temperature, and the distance between the CCDs 7.8 varies, and a correction table corresponding to the temperature data is provided on the ROM 26. As shown in FIG. 4, this correction table is created from a graph of the temperature rise of the substrate 9 and the number of shifted pixels in the overlap portion 12 of C0D7.8.

In such a configuration, first, when the temperature of the substrate 9 is 0° C., the state of the overlap portion 12 of C0D 7.8 becomes an overlap state of 50 pixels as shown in FIG. 2(a). In this state, the pixel data read by the CCD 7 up to element Na4975 is considered valid pixel data, and the pixel data read by the CCD 8 is determined by the element Nα.
26 and above are considered valid pixel data and C0D7.8
The setting is such that seam processing is performed without missing or overlapping between the read pixel data.

For example, consider a case where the thermistor 13 detects that the temperature of the substrate 9 is 20°C.

This temperature information of the board 9 is taken into the CPU 21, and the RO
Refer to the correction table on M26. In other words, according to FIG. 4, it can be seen that at a temperature of 20° C., a shift of 9 pixels occurs. Figure 2(b) shows the CCD7 element Nα4960~50oO (71CC) shifted by 9 pixels in this way.
D8(7) shows a state at 20°C in which the elements Nα1 to Nα41 overlap. The CPU 21 determines that such an extension of 9 pixels has occurred, and changes the position to be processed as valid pixel data. That is, in this state, as in the case of 0° C., the pixel data read by the CCD 7 up to element N114975 is treated as valid pixel data, and the pixel data read by the CCD 8 from element Nα26 onward is processed as valid pixel data. Nine pixels will be missing between the two. However, in this embodiment, since the CPU 21 determines that an elongation of 9 pixels has occurred, the 9 pixels are divided into 4 pixels and 5 pixels (if the number is even,
), the read pixel data of the CCD 7 is divided into two parts by the element Nα49.
The data up to 79 is treated as valid pixel data, and the position where the pixel data read by the CCD 8 is processed as valid pixel data is changed so that the data after element Nα21 is treated as valid pixel data. Such position change data is CP
This is done by selecting from the correction table in the ROM 26 under the control of U 21 and applying it to the shift memory 24.25 to set the first and last addresses for reading.

In this way, the position where the overlap portion 12 of the pixel data read by the CCD 7.8 is processed as valid pixel data is changed according to the temperature of the substrate 9.
Even if a positional change occurs in the read pixel data, accurate reading processing can be performed without missing or duplicating read data at the joint between the CCDs 7 and 8 by processing on the read pixel data side.

Effects The present invention includes a temperature detector that detects the temperature of the substrate to which the reading element is attached as described above.

Since we have provided a calculation control means that calculates the expansion and contraction from this substrate temperature and changes the pixel position to be processed as valid pixel data in the overlapped part of the reading element, even if the length changes between the reading elements due to temperature change, It is possible to perform accurate image reading processing without missing or duplicating read data at the joint portion of the reading elements.

[Brief explanation of drawings]

FIG. 1 is a schematic side view showing the basic configuration of an embodiment of the present invention, FIGS. 2(a) and (b) are explanatory diagrams showing an enlarged overlap part, FIG. 3 is a block diagram, and FIG. 4 5 is a temperature rise vs. deviation pixel number characteristic diagram, and FIG. 5 is a schematic side view showing a conventional example. 7.8...CCD (reading element), 9゛...substrate,
12... Overlamp part, 13... Thermistor (
Temperature detector), 21...CPU (arithmetic control means) Applicant: Ricoh Co., Ltd. --←Da Akebono Seiwa

Claims (1)

[Claims] A plurality of reading elements that digitally read images are arranged in a straight line on a substrate, the pixels read by each reading element have an overlapping part, and the read pixel data of this overlap part is sent to each set position. In an image reading device that performs seam processing between each reading element using read pixel data as valid pixel data,
A temperature detector is provided on the substrate to detect the temperature of this substrate, and the expansion and contraction of this substrate is calculated from the detected temperature of the substrate, and the read pixel data in the overlapped portion is set as valid pixel data according to the expansion and contraction. An image reading device characterized by comprising an arithmetic control means for changing the position of a pixel to be processed.