Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
1999-07-29
2003-11-04
Smith, Zandra V. (Department: 2877)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C250S214100, C348S302000
Reexamination Certificate
active
06642494
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photoelectric conversion apparatus, a production method thereof, and an information processing apparatus having the photoelectric conversion apparatus and, more particularly, to a photoelectric conversion apparatus used in an image input unit of digital X-ray detectors and X-ray image pickup apparatus for medical use, office equipment such as digital copiers, electronic blackboards, facsimile machines, and so on, and information processing apparatus, a production method of the photoelectric conversion apparatus, and an information processing apparatus having the photoelectric conversion apparatus.
2. Related Background Art
The mainstream of the existing X-ray image pickup apparatus used for medical diagnosis is of the so-called film method in which a human body is exposed to X-rays, X-rays transmitted by the human body are made incident to a fluorescent material for converting X-rays to visible light, and a film is exposed to fluorescence emitted from the fluorescent material.
There are, however, strong desires for increase of diagnosis efficiency and for medical equipment with higher accuracy in hospitals, not only in Japan about to go into aging society, but also in the world. Under such circumstances, the conventional X-ray image pickup apparatus of the film method requires long time because of the development step of film in the way before a doctor obtains an X-ray image of a patient, and there are some cases necessitating rephotography, where the patient moved during the X-ray photography or where exposure was not correct. These are the cause of impeding increase of efficiency of medical treatment in the hospitals and would be great hindrance to movement toward new medical society in the future.
In recent years, the demand for “digitization of X-ray image information” is increasing in the medical field. Accomplishment of the digitization will permit the doctor to capture the X-ray image information of the patient at the optimal angle in real time and also permit the X-ray image information obtained to be recorded and managed by use of a medium such as a magnetooptical disk or the like. It will also becomes possible to send the X-ray image information of patient to any hospital in the world within short time by making use of facsimile or other communication method or the like.
In order to meet the demand for the “digitization of X-ray image information,” the X-ray image pickup apparatus using CCD solid state image sensing elements or amorphous silicon photoelectric conversion elements in place of the film has been proposed in recent years.
FIG. 1
is an equivalent circuit diagram to show an example of an equivalent circuit of a two-dimensional photoelectric conversion apparatus.
FIG. 1
shows the two-dimensional photoelectric conversion apparatus of 3×3 for simplicity of description, but the photoelectric conversion apparatus in practice is composed of much more bits, though depending upon the purpose of the apparatus.
Light incident to photoelectric conversion elements S
1
-
1
to S
3
-
3
is subjected to photoelectric conversion in a photoelectric conversion layer and the light information is stored in the form of a charge of a photoelectrically converted signal in a capacitor between electrodes of each photoelectric conversion element. These photoelectric conversion signals are converted to parallel voltage outputs through transfer switches T
1
-
1
to T
3
-
3
and matrix signal wires M
1
to M
3
. Further, they are converted to serial signals by a reading switch circuit unit to be extracted to the outside.
In the structural example of the photoelectric conversion apparatus of
FIG. 1
, the photoelectric conversion elements having the total pixel number of 9 bits are divided into three rows, each row including three bits. The above-stated operations are carried out successively in every unit of these rows.
FIG. 2
is a timing chart to show the operation of the conventional photoelectric conversion apparatus illustrated in FIG.
1
.
Information of light incident to the photoelectric conversion elements S
1
-
1
to S
1
-
3
in the first row is subjected to photoelectric conversion into signal charges and the signal charges are stored as respective interelectrode capacitances in the photoelectric conversion elements S
1
-
1
to S
1
-
3
. After a lapse of a fixed storage time, a shift register SR
1
gives the gate driving wire G
1
a first voltage pulse for transfer during a period of time T
1
to switch the transferring switching elements T
1
-
1
to T
1
-
3
on. This causes the signal charges stored in the respective electrode capacitors (S
1
-
1
to S
1
-
3
) in the photoelectric conversion elements to be transferred through the matrix signal wires M
1
to M
3
to load capacitors C
1
to C
3
, whereupon potentials V
1
to V
3
of the respective load capacitors are increased each by amount equal to the charge of each signal (transfer operation).
Subsequent to it, another shift register SR
2
successively gives voltage pulses to gate driving wires N
1
to N
3
to successively switch corresponding reading switches U
1
to U
3
on, whereby the signals in the first row, which have been transferred to the load capacitors C
1
to C
3
, are converted into serial signals. After impedance conversion by an operational amplifier, the signals of the three pixels are outputted to the outside of the photoelectric conversion apparatus in a period of time T
3
(reading operation).
After that, a reset voltage pulse is applied to CRES for time T
2
to switch reset switches RES
1
to RES
3
on and reset the load capacitors C
1
to C
3
, thereby getting ready for the reading operation of the next row (reset operation).
After that, data of all the pixels is outputted by successively driving the gate driving wires G
2
, G
3
.
FIG. 3
is a schematic, sectional, structural diagram to show an example of an X-ray detecting apparatus for medical use constructed using the two-dimensional photoelectric conversion apparatus illustrated in FIG.
1
. X-rays emitted from X-ray source
1501
are radiated to human body
1502
(affected part of a patient), and transmitted X-rays carrying information corresponding to internal information of lung part, bone part, or lesion travel toward a grid plate
1503
. The grid plate
1503
is placed for the purpose of preventing X-rays scattered inside the human body from irradiating a fluorescent member
1504
and the photoelectric conversion apparatus
1506
and is made of a material
1507
absorbing X-rays like lead and a material
1508
transmitting X-rays like aluminum. The X-rays passing through the grid irradiate a wavelength conversion element, which is the X-ray-to-visible light converting fluorescent member
1504
in this example, to be converted to the visible light there in the sensitive wavelength region of the photoelectric conversion elements
1509
. In this way the fluorescence from the X-ray-to-visible light converting fluorescent member is photoelectrically converted by the photoelectric conversion apparatus
1506
. Numeral
1509
designates the photoelectric conversion elements,
1510
the switching elements, and
1511
a protective film for protecting the photoelectric conversion elements and the switching elements. Numeral
1512
denotes an insulating substrate on which the photoelectric conversion elements and the switching elements are placed.
FIG. 4A
is a schematic, top plan view to show an example of the photoelectric conversion circuit unit wherein the photoelectric conversion elements and switching elements are made of amorphous silicon semiconductor thin films, and
FIG. 4B
is a schematic, sectional, structural diagram to show a cross section along
4
B—
4
B in FIG.
4
A. The photoelectric conversion elements
301
and the switching elements
302
(amorphous silicon TFTs, which will be referred to simply as TFTs) are formed on a common substrate
303
, the lower electrodes of the photoelectric conversion elements are made of a first metal thin f
Fitzpatrick ,Cella, Harper & Scinto
Smith Zandra V.
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