Image sensing integrated circuit device

Details Image sensing integrated circuit device Image sensing integrated circuit device

1997-12-11

2001-07-24

Garber, Wendy R. (Department: 2612)

Television

Camera, system and detail

Solid-state image sensor

C348S308000, C348S310000, C250S208100, C358S482000

Reexamination Certificate

active

06266089

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sensor IC (integrated circuit) device and an image sensor incorporating such a sensor IC device for use in facsimile machines, image scanners, and others for image reading purposes.
2. Description of the Prior Art
A conventional sensor IC device and a contact image sensor (hereafter also referred to as a CIS) incorporating it will be described with reference to
FIGS. 2 and 3
. As shown in
FIG. 2
, a conventional CIS is composed of a plurality of sensor IC devices
21
. Each sensor IC device
21
includes an array of, for example, 96 light-sensing elements
23
such as phototransistors. Each light-sensing element
23
corresponds to one pixel.
By the side of each sensor IC device
21
, an LED (light-emitting diode)
20
is provided that illuminates with light a paper sheet or other having an image to be read formed on it. Thus, the light-sensing elements
23
output electric signals in accordance with the light reflected from the paper sheet or other. The sensor IC device
21
successively outputs the signal from one light-sensing element
23
after another. Since the signal outputted from the sensor IC device
21
is feeble, it is then amplified by an amplifier
22
that is provided separately from the sensor IC devices
21
. This operation is repeated to read the entire image on the paper sheet or other.
On the other hand, as shown in
FIG. 3
, in another type of conventional CIS, each sensor IC device
24
incorporates an amplifier circuit
25
. Accordingly, the sensor IC device
24
outputs the signal from each light-sensing element
23
after amplifying the signal with its own amplifier circuit
25
, and thus the signal outputted from the sensor IC device
24
is used intact as the output of the CIS. Note that, in
FIG. 3
, such components as are found also in
FIG. 2
are identified with the same reference numerals, and overlapping explanations will not be repeated.
However, the CIS shown in
FIG. 2
requires an amplifier
22
as a separate component. Quite inconveniently, this requires not only extra space to mount the amplifier, but also extra wiring for it, and thus leads to reduced reliability and to increased cost. On the other hand, the CIS shown in
FIG. 3
suffers from variation in “dark output voltage” (that is, the voltage that the CIS outputs when it receives no reflected light), because the offset voltage of the amplifier circuit
25
incorporated in each sensor IC device
24
varies slightly from one sensor IC device to another. Quite inconveniently, making the dark output voltage constant requires extra measures, such as trimming, that are difficult to realize.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a sensor IC device and an image sensor incorporating it that require fewer separate components and thus are more reliable and require less cost for the purchase and maintenance of their components and that are free from variation in dark output voltage between individual sensor IC devices.
To achieve the above object, a sensor IC device according to the present invention is provided with: a sensor circuit having a plurality of light-sensing elements for outputting the outputs of the light-sensing elements one after another; an amplifier circuit provided separately from the sensor circuit; a first output terminal for directing the output of the sensor circuit out of the sensor IC device; an input terminal for directing an external signal to the amplifier circuit; and a second output terminal for directing the output of the amplifier circuit out of the sensor IC device.
On the other hand, an image sensor according to the present invention includes a plurality of sensor IC devices as described above, and, in this image sensor, the first output terminal of each of the sensor IC devices is connected to the input terminal of a particular one of the sensor IC devices so that the output of every light-sensing element is amplified by the amplifier circuit provided in that particular one of the sensor IC devices.


REFERENCES:
patent: 4845567 (1989-07-01), Yamaguchi
patent: 5027226 (1991-06-01), Nagata
patent: 5408113 (1995-04-01), Kanno
patent: 5784178 (1998-07-01), Tsai
patent: 6025935 (2000-02-01), Tseng

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