JP3066658B2 - Image reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus for converting optical image information into an electric signal, and more particularly to a multi-chip type line sensor in which photoelectric conversion elements are linearly integrated.

[0002]

2. Description of the Related Art Conventionally, an image reading apparatus as shown in FIG. 2 is known. The signal from the photoelectric conversion element 1 _n is output to the common signal line via the switching element 2 _n . The plurality of switching elements 2 _n are sequentially scanned by the scanning circuit 3, the output signals are impedance-converted by the impedance conversion circuit 8, and are output in time series from the image signal output terminal 33. As a device that realizes this, there is a device in which the image reading device is downsized using a CCD as a scanning circuit as shown in FIG.

[0003]

However, in the conventional line sensor, as shown in FIG. 3, even when the image reading device 47 is small, the reflected light of the original 45 illuminated by the light is reflected on the line sensor by using the lens 46 even when the image reading device 47 is small. In order to form an image and convert the image signal into an image signal, a distance is required from the document to the line sensor, and electronic equipment such as a facsimile cannot be miniaturized. Reference numeral 48 denotes a substrate, and reference numeral 49 denotes a common image signal output terminal. Also,
As shown in FIG. 4, a method of using a selfoc lens as an image forming optical system of 1: 1 and arranging an image reading apparatus with a wide original to reduce the size of an electronic device is also used. However, in this method, as shown in FIG. 4, a plurality of image reading devices 47 are arranged on a substrate 48 and an image signal output terminal 49 is commonly connected to obtain an image signal in time series. As shown in FIG. 5, since all impedance conversion circuits provided in each chip are output to the same terminal, there is a disadvantage that the obtained image signal is distorted. Further, the image reading device 47 on the substrate 48
It is conceivable to provide image signal output terminals of
External signal processing becomes complicated. 39 is a select signal input terminal, and 40 is an image signal input terminal. An object of the present invention is to provide a time-series image signal without distortion even if a plurality of image reading devices are arranged in order to solve such a conventional disadvantage.

[0004]

According to the present invention, there is provided an image reading apparatus comprising an output control circuit which operates by inputting a scanning input signal, a scanning output signal, and a clock pulse. The impedance conversion circuit and the switching element are controlled by a control signal output from the output control circuit, so that even if a plurality of image reading apparatuses are arranged, an image signal without distortion can be obtained in time series.

[0005]

In the image reading apparatus constructed as described above,
Even if a plurality of image signals are arranged on the same substrate and the image signal output terminals are connected in common, the device that outputs image signals is limited by the output control circuit. Obtainable. Further, low current consumption can be realized by controlling the impedance conversion circuit by the output control signal.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.
I do. FIG. 1 is a block diagram and a diagram of an image reading apparatus according to the present invention.
1, the photoelectric conversion element 1 _nSwitch signal from
Element 2_nIs connected to the common signal line 34. Duplicate
Several switching elements 2_nAre sequentially determined by the scanning circuit 3.
The next scan is performed. Scan circuit 3 receives clock pulse CK
The scanning input signal SI is input, so that a plurality of scans are performed.
Switching element 2₁… 2_nScan so that
Generate a pulse. Last-stage switching element 2_nTo
After driving, the scanning output signal forming circuit 5
Output signal SO is output. Multi-chip line cell
When a plurality of sensors are arranged, the scanning output signal SO
It becomes the next scanning input signal SI of the line sensor. Signal S
I, signal SO and clock pulse CK
The path 7 outputs the select signal SEL, and the signal of the common signal line is output.
Impedance conversion circuit that converts the signal to impedance
8. A switch to read the impedance-converted signal to the outside
The switching element 9 is driven. This image reading device
FIG. 6 shows the timing chart. The scanning circuit 3 is a clock
Operates on the falling edge of the pulse CK and switches i-th
Element 2_i(I = 1 to n) indicates that the signal SI is input to the scanning circuit.
Is driven at the low level of the ith signal CK,
i-th photoelectric conversion element 1_iImage signal is read out
It is.

FIG. 7 shows an embodiment of the output control circuit 7.
In FIG. 7, the circuit is constituted by a NOR circuit, but may be constituted by a NAND circuit. Also, without inputting the CK signal,
It is also possible to configure an output control circuit. FIG. 8 shows an embodiment of the impedance conversion circuit 8. When the select signal SEL is at the low level, the transistor 41 operates and the signal input to the input terminal 40 is impedance-converted and output from the output terminal 42. When the select signal SEL is at a high level, the transistor 41 does not operate, the output terminal 42 is in a high impedance state,
The output terminal is insulated from the input terminal 40. Also,
Since the transistor 41 does not operate, no current is consumed.

The switching element 9 shown in FIG. 9 is also driven by the select signal SEL. Select signal is Lo
At the w level, it is conductive, and at the high level, it is non-conductive. These operations are performed by setting the switching element 9 to N
It may be a MOS transistor. Thus, the impedance conversion circuit 8 and the switching element 9
Operates only when the select signal SEL shown in FIG. 6 is High. Therefore, even if a plurality of image reading apparatuses according to the present invention are arranged, the number of output image signals is limited to one. Also, the impedance conversion circuit, except during operation,
Since no current is consumed, current consumption is low. Although a configuration not using an impedance conversion circuit is possible, the present invention is also effective in such a case.

In FIG. 1, the switching element is NMOS for convenience.
However, a CMOS configuration may be used. Further, for convenience, the scanning circuit performs the falling operation of CK, but the scanning circuit may perform the rising operation, and at that time, other circuits can be changed accordingly.

[0010]

The present invention provides an output control circuit using a scanning input signal, a scanning output signal, and a clock pulse.
By controlling the image signal output period, even if a plurality of image reading devices are arranged on the same substrate, the image signal output terminals can be made common, so that signal processing is easy and an image driven with low current consumption can be obtained. There is the effect of providing a reader.

[Brief description of the drawings]

FIG. 1 is a block diagram of an image reading apparatus according to the present invention.

FIG. 2 is a block diagram of a conventional image reading device.

FIG. 3 is a perspective view of an embodiment of a document reading system using a conventional image reading apparatus.

FIG. 4 is a perspective view of another embodiment of the conventional document reading system.

FIG. 5 is a circuit diagram showing a circuit connected to a common signal line of the system of FIG. 4;

FIG. 6 is a timing chart of the image reading apparatus of the present invention.

FIG. 7 is a circuit diagram showing one embodiment of an output control circuit 7;

FIG. 8 is a circuit diagram showing one embodiment of the impedance conversion circuit 8;

FIG. 9 is a circuit diagram showing one embodiment of a switching element 9;

[Explanation of symbols]

Reference Signs List 1 ₁ to 1 _n photoelectric conversion element 2 ₁ to 2 _n switching element A 3 scanning circuit 4 scanning input signal forming circuit 5 scanning output signal forming circuit 6 scanning clock pulse forming circuit 7 output control circuit 8 impedance conversion circuit 9 switching Element B 30 Scanning input signal input terminal 31 Scanning clock pulse input terminal 32 Scanning output signal output terminal 33 Image signal output terminal 34 Common signal line 35 Control output signal input terminal 36 Control clock pulse input terminal 37 Control input Signal input terminal 38 Select signal output terminal 39 Select signal input terminal 40 Image signal input terminal 41 Transistor 42 Impedance conversion circuit output terminal 43 Switching element input terminal 44 Switching element output terminal 45 Document 46 Lens 47 Conventional image reader 48 Substrate 49 Passing the image signal output terminal 50 SELFOC lens

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukito Kawahara 6-31-1, Kameido, Koto-ku, Tokyo Seiko Electronic Industries Co., Ltd. (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 1 / 028

Claims (2)

(57) [Claims] 1. A large number of photoelectric conversion elements integrated on a straight line, a first switching element connected to each of the photoelectric conversion elements for reading a signal from the photoelectric conversion element, and a first switching element. A scanning circuit for sequentially driving the elements, a scanning input signal forming circuit for driving the scanning circuit, a scanning output signal forming circuit, and scanning of the scanning input signal, the scanning output signal, and the scanning circuit An output control circuit controlled by a clock signal forming circuit for use, a second switching element controlled by a select signal of the output control circuit, and an impedance conversion circuit. One terminal is connected to the photoelectric conversion element,
The other terminals are all common and are connected to the input terminal of the impedance conversion circuit, the output terminal of the impedance conversion circuit is connected to one terminal of the second switching element, and the other terminal of the second switching element terminal has become the image signal output terminal to the outside, the second switching together with the select signal of the output control circuit is operating power to only the b <br/> impedance conversion circuit period of the activating supplied By conducting the element,
An image reading apparatus, wherein the impedance conversion circuit operates only during a period in which the select signal is active, and an output signal thereof is guided to the image output terminal. 2. The image reading apparatus according to claim 1, wherein a plurality of said image reading apparatuses are arranged on the same substrate, and image signal output terminals of said plurality of image reading apparatuses are electrically common.