Imaging apparatus

Details Imaging apparatus Imaging apparatus

2002-06-25

2004-07-20

Pyo, Kevin (Department: 2878)

Radiant energy

Photocells; circuits and apparatus

Photocell controlled circuit

C250S214100, C250S370090

Reexamination Certificate

active

06765187

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to imaging apparatus such as light detecting apparatus, radiation detecting apparatus, etc. used in medical diagnostic imaging apparatus, nondestructive inspection apparatus, analyzing apparatus using radiation, and so on.
2. Related Background Art
FIG. 8
shows an example of an equivalent circuit diagram of an imaging apparatus applied to the radiation detecting apparatus, and
FIG. 9
a plan view thereof. In
FIGS. 8 and 9
, P
11
to P
44
designate photoelectric conversion elements, and T
11
to T
44
TFTs. The photoelectric conversion elements are connected to common bias lines Vs
1
to Vs
4
, and a constant bias is applied to them. A gate electrode of each TFT is connected to a common gate line Vg
1
to Vg
4
. Each gate line is connected to a gate drive device and on/off of the TFTs is controlled by drive pulses from the gate drive device. A source or drain electrode of each TFT is connected to a common signal line Sig
1
to Sig
4
and the signal lines Sig
1
to Sig
4
are connected to a read device.
X-rays irradiated toward an object are attenuated and transmitted by the object, the transmitted X-rays are converted into visible light in a phosphor layer, and this visible light enters the photoelectric conversion elements to generate charges in the respective photoelectric conversion elements. The charges are transferred through the TFTs into the signal lines by gate drive pulses applied by the gate drive device to be read by the read device. Thereafter, the charges generated in the photoelectric conversion elements are removed by the common bias lines Vs
1
to Vs
4
.
A typical example of the conventional radiation detecting apparatus of this type is a radiation detecting device in which the foregoing phosphor layer is bonded to the imaging apparatus of MIS-TFT structure comprised of MIS photoelectric conversion elements and switching TFTs.
FIG. 10
shows an example of a schematic sectional view of the device. Numeral
10
denotes a photoelectric conversion element and
20
a TFT. Numeral
11
designates a lower electrode of the photoelectric conversion element;
12
insulating layers;
15
a bias line for applying a bias to the photoelectric conversion element
10
;
16
a photoelectric conversion layer of the photoelectric conversion element
10
and a semiconductor layer of the TFT
20
;
17
a wire formed on the semiconductor layer
16
and electrode layers for establishment of ohmic contact of the semiconductor layer
16
;
21
a gate electrode of the TFT
20
;
22
source and drain electrodes of the TFT
20
;
30
a phosphor layer for conversion of incoming radiation into visible light;
31
an adhesive layer for adhesion of the phosphor layer
30
;
32
a mounting protective layer; and
36
a moisture-resistant protective layer. The radiation is incident from above in
FIG. 10
to be converted into visible light by the phosphor, and the visible light enters the MIS photoelectric conversion element to be converted into a charge to be stored.
In the radiation imaging apparatus of this structure, there were increasing demands for achievement of higher sensitivity for the purpose of reducing radiation doses and other purposes, while the incoming visible light was reflected by the protective films and others, so as to cause optical losses, posing a significant issue in the achievement of higher sensitivity. Particularly, in the case where there are provided a plurality of protective films having their respective separate functions, the foregoing issue can be serious in particular.
An object of the present invention is, therefore, to provide imaging apparatus and radiation detecting apparatus with high sensitivity on the basis of improvement in a configuration of protective films and others on the photoelectric conversion element to reduce the reflection caused by the films above the photoelectric conversion layer, in order to guide the light emission from the phosphor into the photoelectric conversion element efficiently.
In order to achieve the above object, an imaging apparatus according to the present invention is an imaging apparatus comprising a photoelectric conversion layer for converting incident light into charge, on an insulating substrate, an electrode layer formed on the photoelectric conversion layer, and a protective layer formed on the electrode layer, wherein relations of n
a
−n
b
≦1.5 and n
b
−n
c
≦1.5 are met where n
a
is a refractive index of the photoelectric conversion layer, n
b
a refractive index of the electrode layer, and n
c
a refractive index of the protective layer.
Another imaging apparatus according to the present invention is an imaging apparatus comprising a photoelectric conversion layer for converting incident light into charge, on an insulating substrate, an electrode layer formed on the photoelectric conversion layer, and a plurality of protective layers formed on the electrode layer, wherein relations of n
a
−n
b
≦1.5 and n
b
−n
c1
≦1.5 and n
c1
−n
c2
≦1.5, . . . , and n
ci
−n
ci+1
≦1.5 are met where n
a
is a refractive index of the photoelectric conversion layer, n
b
a refractive index of the electrode layer, and n
c1
, n
c2
, . . . , n
ci
, and n
ci+1
(i=1, 2, 3 . . . ) are refractive indices of the protective layers in order from the side adjacent to the electrode layer.
The details will be described in the embodiments of the invention.


REFERENCES:
patent: 5965872 (1999-10-01), Endo et al.
patent: 6100682 (2000-08-01), Schroeder
patent: 6271662 (2001-08-01), Schroeder
patent: 6291989 (2001-09-01), Schroeder
patent: 6489618 (2002-12-01), Morishita
patent: 6670595 (2003-12-01), Sasaki et al.
Allegro Microsystems, Inc., ATS660LSB,True Zero-Speed, Hall-Effect Adaptive Gear-ToothSensor, Worcester, Massachusetts, Copyright 2002, 16 pages.

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