JPH0783420B2 - Image reader - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image reading apparatus for reading image information of an original of a digital type copying apparatus, for example.

[Problems with Technical Background of the Invention] In recent years, in copying machines, image reduction / enlargement, shift,
Attention has been paid to a digital type copying apparatus which can easily perform various image editing functions such as area designation and insertion.

In such a digital type copying apparatus, image information on an original is read by an image reading apparatus by optical means, an electric signal output from the image reading apparatus is converted into a digital signal, and the signal is stored in a memory. The copying unit performs a copying operation based on the signal.

In general, the image reading apparatus described above includes a light source that irradiates a document with light, an optical system for forming an image of reflected light from the document,
CCD that receives light that has passed through this optical system and converts it into an electrical signal
And a storage type photoelectric conversion element array such as a MOS type, and scanning while irradiating the original with light from a light source, the reflected light is incident on the photoelectric conversion element array through an optical system, and an electrical signal is generated. It is done by converting to.

By the way, the optical system of such an image reading apparatus has a pair of a reduction optical system that focuses reflected light on a photoelectric conversion element array to form an image and a pair of optical systems that forms reflected light on the photoelectric conversion element array at an equal magnification. There is one type of optical system.

An image reading apparatus having a one-to-one optical system may have a shorter optical path length than an image reading apparatus having a reduction optical system,
This makes it possible to reduce the thickness and weight of the entire device.

Further, the photoelectric conversion element array of the image reading apparatus having the one-to-one optical system has a one-to-one light receiving area with respect to the original, and has a wider light receiving area than the photoelectric conversion element array of the apparatus reading apparatus having the reduction optical system. be able to. For example, assuming that the amount of reflected light is the same, the photoelectric conversion element example of the image reading apparatus having the one-to-one optical system can obtain a larger output signal than the photoelectric conversion element example of the image reading apparatus having the reduction optical system. You can That is, by using an image reading device having a one-to-one optical system, the light amount from the light source required to obtain the same output signal can be reduced, and as a result, a light source such as an LED that has a relatively small light amount can be reduced. Can be used.

Furthermore, in the above-mentioned one-to-one optical system, by using the rod lens array, it is possible to easily obtain a uniform and high-resolution image reading capability of about 16 lines / mm.

Generally, in a digital type copying apparatus, an image reading apparatus having such a one-to-one optical system is moved in one direction under a transparent document table 1 provided in the copying apparatus, as shown in FIG. Supported as possible. In the image reading apparatus A, LED light sources 2a and 2b for irradiating the original with light are arranged along the inner side of a base 3 having a length substantially the same as the original table 1 in a direction orthogonal to the moving direction of the image reading apparatus A. Are arranged.
A one-to-one optical system 4 for imaging reflected light from the original is arranged along the base 3 between the LED light sources 2a and 2b. In addition, a photoelectric conversion element array 5 that receives light that has passed through the optical system 4 and converts it into an electric signal is similarly arranged along the base 3. Further, below the photoelectric conversion element array 5, a signal processing circuit board 6 for driving the photoelectric conversion element array 5 and inputting an electric signal from the photoelectric conversion element array 5 to convert it into a digital signal is similarly formed. It is arranged along the table 3. The photoelectric conversion element array 5 and the signal processing circuit board 6 are electrically connected via the lead frame 7. Further, an input / output connector 8 for connecting to the outside is attached to one end of the signal processing circuit board 6.

Then, the original is placed on the original table 1, and the original is irradiated with light by the LED light sources 2a and 2b, and the reflected light of the irradiated light is incident on the photoelectric conversion element array 5 through the optical system 4. The photoelectric conversion element array 5 converts the electric signal into an electric signal according to the brightness of the reflected light, and the electric signal is input to the signal processing circuit board 6 via the lead frame 7. Further, the signal processing circuit board 6 is used to set the predetermined signal level to 2
It is converted into a digitized signal and output to the outside through the input / output connector 8. On the other hand, in the photoelectric conversion element array 5, a voltage is applied from an external power source to the signal processing circuit board 6 through the input / output connector 8, whereby the signal run-in of the signal processing circuit board 6 operates, and the operation signal Is driven by being input to the light beam conversion element array 5 via the lead frame 7.

By the way, when the image reading apparatus A has the one-to-one optical system 4 as described above, the photoelectric conversion element array 5 has to be designed according to the size of the document table 1, and therefore the length is very long. Further, the signal processing circuit board 6 arranged under the photoelectric conversion element array 5 is also substantially the same vertically long.

Further, the image reading apparatus A needs to drive the photoelectric conversion element array 5 by a high-speed digital signal called a so-called video band.

Further, a digital signal for driving the photoelectric conversion element array 5 and an analog signal output from the photoelectric conversion element array 5 are mixed on the signal processing circuit board 6.

Furthermore, it is necessary to use a voltage of MOS level (around + 12V) as a digital voltage for driving the photoelectric conversion element array 5.

Due to these circumstances, the electric signal output from the photoelectric conversion element array 5 is induced noise generated on the signal processing circuit board 6 due to the parasitic capacitance between the signal lines, ripple generated between the power supply line and the ground line, and high frequency. There is a problem that the S / N ratio is lowered on the signal processing circuit board 6 due to the influence of power source noise such as noise.

[Object of the Invention] The present invention has been made in view of such circumstances, and the signal line of the drive circuit is not affected by noise,
An object of the present invention is to provide an image reading device capable of preventing deterioration of N ratio.

[Summary of the Invention] That is, an image reading apparatus of the present invention includes a light source that irradiates a document with light, an optical system for forming an image of reflected light from the document, and a light that has passed through this optical system. In an image reading device including a photoelectric conversion element array for converting into an electric signal and a drive circuit for driving the photoelectric conversion element array, the drive circuit is configured such that a signal line, a power supply line and a ground line are formed in different layers. The signal line of the drive circuit is not affected by noise and is prevented from deteriorating the S / N ratio by using the multilayer wiring board.

Embodiments of the Invention Hereinafter, details of embodiments of the present invention will be described with reference to the drawings.

Since the image reading apparatus of the present invention is almost the same as the image reading apparatus A described in FIG. 3 of the conventional example, it will be described with reference to FIG.

As shown in the figure, LED light sources 2a and 2b are arranged on a base 3, and a one-to-one optical system 4 is arranged between these LED light sources 2a and 2b. Further, a photoelectric conversion element array 5 is arranged under the one-to-one optical system 4, a signal processing circuit board 6 is arranged under the optical conversion element array 5, and these photoelectric conversion element arrays 5 are arranged via a lead frame 7. And the signal processing circuit board 6 are electrically connected. An input / output connector 8 for connecting to the outside is arranged at a predetermined position of the signal processing circuit board 6.

Then, place the original (not shown) on the original table 1 and the LED light source 2
By irradiating with a and 2b and forming an image of the reflected light on the photoelectric conversion element array 5 through the one-to-one optical system 4, this light is converted into an electric signal and this electric signal is passed through the lead frame 7. Is input to the signal processing circuit board 6, converted into a binarized signal, and output to the outside via the input / output connector 8.

The points described above are the same as those described in the conventional example, but the difference of this embodiment from the conventional example is that the signal processing circuit board 6 described above is changed as follows.

FIG. 1 is a partially enlarged side view of the periphery of the signal processing circuit 6'in this embodiment.

In the figure, 5 is a photoelectric conversion element array, 6'is a signal processing circuit board, 7 is a lead frame, and 8 is an input / output connector.

The signal processing circuit board 6'in this embodiment is formed of a glass epoxy multi-layer board and is composed of four layers. A vertical wiring line of the signal line is formed on the first layer, a feeding line is formed on the second layer, a ground line is formed on the third layer, and a horizontal wiring line of the signal line is formed on the fourth layer. Are formed.

Note that these different lines are electrically connected via through holes.

The signal lines of the first layer and the fourth layer are supplied with power and driven by the power feeding line of the second layer and the ground line of the third layer, which are connected to the input terminals of the input / output connector 8. The drive signal is input to the photoelectric conversion element array 5 via the lead frame 7 and driven.

On the other hand, the electric signal from the photoelectric conversion element array 5 is input to the signal lines of the first layer and the fourth layer via the lead frame 7, is converted into a digital signal by this signal line, and is output from the input / output connector 8. Is output to the outside via.

By forming the signal line, the power supply line, and the ground line on different layers of the multilayer wiring board as described above, the occurrence of inductive noise between the signal lines is reduced due to the parasitic capacitance between the signal line and the ground line. The generation of power supply noise is greatly reduced by the coupling due to the parasitic capacitance between the power supply line and the ground line.

Since the above-described noise does not occur in the signal line, the electric signal output from the photoelectric conversion element array 5 and the electric signal output from the input / output connector 8 via the signal processing circuit board 6 '. The S / N ratio with the output signal at that time almost disappears.

In order to confirm such an effect, an output signal when the signal processing circuit board 6 of the conventional example is used and an output signal when the signal processing circuit board 6'of this embodiment is used are shown in FIG. It shows in (B).

FIG. 2 (A) shows an output signal when the signal processing circuit board 6 of the conventional example is used, and the influence of the induced noise on the signal line generated by the parasitic capacitance between the signal line and the ground line is shown in FIG. The high-frequency noise shown in FIG. 3 and the influence caused by the power supply noise generated by the coupling due to the parasitic capacitance between the power supply line and the ground line appear as the ripple shown in FIG. On the other hand, the second
The high-frequency noise and the ripple are not generated in the output signal when the signal processing circuit board 6'of the present embodiment shown in FIG.

Although the lead frame 7 is used to connect the photoelectric conversion element array 5 and the signal processing circuit board 6'in the above-described embodiment, the present invention is not limited to this, and the connection may be made using a flexible board, for example. It is also possible to connect directly with a bonding wire, and these may be directly connected with the photoelectric conversion element array 5 and the signal processing circuit board 6 ', for example, formed on the same board.

Further, the photoelectric conversion element array 5 may use a thin film made of a photoconductive material, and may further use a multi-chip IC sensor.

[Effects of the Invention] As described above, according to the image reading apparatus of the present invention, the drive circuit is formed by the multilayer wiring board and is divided into the signal line, the power supply line, and the ground line, and these lines are also multilayer wiring. By being formed on different layers of the substrate, the signal line of the drive circuit is not affected by noise, and deterioration of the S / N ratio of the drive circuit can be prevented.

[Brief description of drawings]

FIG. 1 is a partially enlarged side view of an image reading apparatus according to an embodiment of the present invention, FIGS. 2A and 2B are graphs for explaining the effect of this embodiment, and FIG. 3 is a conventional example. FIG. 3 is a vertical sectional front view of the image reading apparatus of this embodiment. A ... Image reading device 1 ... Original plate 2a, 2b ... LED light source 3 ... Base 4 ... One-to-one optical system 5 ... Photoelectric conversion element array 6, 6 '... Signal processing circuit board 7 ...... Lead frame 8 …… Input / output connector

Claims (2)

[Claims] 1. A light source for irradiating an original with light, an optical system for forming an image of reflected light from the light source, and a photoelectric conversion element array for receiving light passing through the optical system and converting the light into an electric signal. And an image reading apparatus including a drive circuit for driving the photoelectric conversion element array, wherein the drive circuit includes a multilayer wiring board in which a signal line, a power supply line, and a ground line are formed in different layers. Characteristic image reading device. 2. The image reading apparatus according to claim 1, wherein the optical system has a magnification of 1: 1.