Semiconductor device manufacturing: process – Making device or circuit responsive to nonelectrical signal – Responsive to electromagnetic radiation
Reexamination Certificate
2000-10-17
2002-10-22
Talbott, David L. (Department: 2827)
Semiconductor device manufacturing: process
Making device or circuit responsive to nonelectrical signal
Responsive to electromagnetic radiation
C438S059000, C438S068000, C438S070000, C438S075000, C348S229100, C348S230100, C348S241000, C348S272000, C348S294000, C358S463000, C250S208100
Reexamination Certificate
active
06468827
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an image sensor chip, and to a manufacturing method and image sensor therefor.
BACKGROUND ART
FIG. 11
shows the general structure of a conventional image sensor
10
used in image-scanning devices or in the image read units of fax machines.
A plurality of image sensor chips
13
are secured within an area whose length corresponds to the read width on a substrate
12
disposed on the bottom surface of a case
11
made of a resin or the like. A transparent glass cover
14
is placed on the top surface of the case
11
, and a rod lens array
15
for converging a contrast image, which is aligned with a read line L marked on the glass cover
14
, as an erect image of the same size on the image sensor chip array is disposed between the read line L and the image sensor chips
13
. A plurality of LEDs
16
, which serve as light sources for illuminating a document D through the back surface of the glass cover
14
, are mounted on the a substrate
17
inside the case
11
.
For example, a 1728-bit photoreceptor must be provided to obtain such an image sensor in order to read an A
4
document at 8 pixels per millimeter, and
18
image sensor chips
13
should be mounted on the substrate
12
in order to provide, for example, a single image sensor chip with a 96-bit photoreceptor. Here, the length of a single image sensor chip
13
is about 12 mm.
An image sensor chip
13
is fabricated by integrating a plurality of phototransistors that correspond to the photoreceptors, analog switches connected in series with each of the phototransistors, shift registers for sequentially selecting and switching on the analog switches in accordance with clock pulses, and the like. The output side of each of the analog switches is brought out to the output terminal of the chip.
An electric current corresponding to the amount of light received during a read cycle flows through each phototransistor. When such an image sensor chip is selected, the analog switches are sequentially switched on, for example, during the fall cycles of clock pulses, with the result that microcurrent analog data corresponding to the amount of light received by each phototransistor are serially outputted to the output terminal of the chip. The output terminal of the chip is connected to a load resistor on the substrate, and the potential difference at a terminal of this load resistor is amplified by an amplification circuit mounted on the substrate.
Thus, such conventional image sensors and image sensor chips mounted thereon operate on the principle that the output microcurrent from the image sensor chips flows through the load on the substrate, and the potential at the ends of this load is amplified by an amplification circuit.
A first drawback, therefore, is that the analog data signals outputted from such image sensor chips are microsignals in the form of a high-impedance output, which, basically, facilitates noise pickup and thus impairs the read performance of the image sensor. In particular, clock pulse signals of several hundred kilohertz for use in data shifting are inputted to the substrate
12
on which the image sensor chips
13
are mounted, and these clock pulse signals are thus ultimately superposed as alternating-current components on the analog data signals (as shown in FIG.
12
), adversely affecting the output characteristics.
Methods commonly undertaken in order to minimize the effect of such noise involve surrounding the analog data wiring on the substrate with grounded wiring, and placing the clock signal wiring on the back side of the substrate in a position removed as far as possible from the sensor chips.
The result is that products provided with wiring patterns on both the front and back surfaces can solely be used for the substrate
12
(as is also shown in FIG.
11
). This complicates the procedures involved in fabricating such products and in mounting components on them, involves forming irregularities for the components on the back surface of the substrate
12
, detracts from the aesthetic appeal of the image sensor, requires more space in the width direction for installing such an image sensor, and makes it more difficult to design compact equipment containing such image sensors.
Another drawback is that the ICs, capacitors, and resistors constituting the amplification circuit; the varistors for adjusting the gain of the amplification circuit; and a plurality of other electronic components must be mounted on the substrate separately from the image sensor chips, complicating the steps involved in the manufacture of the image sensor substrate. Specifically, the various electronic component themselves are expensive, equipment is needed for mounting these electronic components on the substrate, and the varistors must be individually adjusted while the output of the amplification circuit is measured in order to adjust the gain of the amplification circuit in accordance with the specification requirements of the customer.
DISCLOSURE OF THE INVENTION
In view of the above, it is an object of the present invention to provide an image sensor chip for use in constructing a contact-type image sensor such that the substrate on which these components are mounted can be fabricated very easily, and to provide a smaller and thinner image sensor in which the substrate does not require noise prevention and in which a substrate wired on only one side can be used.
According to a first aspect of the present invention, there is provided an image sensor chip manufactured by integrating a prescribed number of photoelectric conversion elements as photoreceptors, analog switches connected in series to the corresponding photoelectric conversion elements, and a switch circuit for sequentially switching on the analog switches in accordance with clock signals; wherein this image sensor chip is characterized by further comprising
output load components jointly connected in series to sets composed of the photoelectric conversion elements and their respective analog switches; and an amplification circuit for amplifying the potential of the output load components on the side of the photoelectric conversion elements.
According to a preferred embodiment, the image sensor chip comprises a power terminal, a ground terminal, a clock signal input terminal, an analog signal output terminal, photoelectric conversion elements arranged in a row at regular intervals and connected at one end to the power terminal, analog switches connected to the respective output terminals of the photoelectric conversion elements, a switch circuit for sequentially switching on the analog switches in accordance with clock signals, and output load components jointly interposed between the ground terminal and the output terminals of the analog switches, wherein the chip is configured such that the output of the amplification circuit is outputted to the analog signal output terminal.
According to a preferred embodiment, the output load is a load resistor.
According to another preferred embodiment, the output load is a load capacitor.
According to yet another preferred embodiment, the output load consists of a load resistor and a load capacitor connected in parallel to each other.
In the preferred embodiment, the gain-adjusting resistor of the amplification circuit is also fabricated in integral form, and the gain-adjusting resistor comprises a plurality of resistors connected in series and cut table bypass wirings provided to all or some of the plurality of resistors.
Yet another feature of the preferred embodiment is that the amplification circuit is an operational amplifier; that the gain-adjusting resistor comprises a resistor group interposed between the inverting input and the output of the operational amplifier, and a resistor group interposed between the ground and the inverting input of the operational amplifier; and that each resistor group comprises a plurality of resistors connected in series and cut table bypass wirings provided to all or some of these resistors.
Thus, the image sensor chip pertaining to th
Fujimoto Hisayoshi
Masaoka Hiroaki
Merchant & Gould P.C.
Talbott David L.
Zarneke David A.
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