JPS6237963A - Pyroelectric type infrared image pick up device - Google Patents

Abstract

PURPOSE:To read the positive and negative signals of a pyro-sensor by a simple structure, by projecting light on an accumulating diode of a scanning part, and generating initial bias charge in the accumulating diode. CONSTITUTION:An infrared image 10 is inputted to a pyro-film 21 through a Cr electrode 20. The film 21 generates signal charges in both positive and negative polarities in correspondence with the operation of an optical chopper, which opens and closes the image 10. The potential changes due to the signals charges modulate the bias charge of an accumulating diode 23 through a polysilicon electrode 22. At this time, visible light is continuously projected on a pyro-CCD 15 through a reflecting plate 14-1. Therefore, the bias charge is generated in the diode 23. The charge is written in a CCD transfer means through a writing gate 24 after a specified accumulating time. The charge is vertically transferred and thereafter horizontally transferred. Then the charge is taken out as an image signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improvement in the signal readout method of a pyroelectric infrared imaging device using a solid-state scanning circuit.

Conventional technology Figure 10 is an equivalent circuit of a unit pixel to explain the conventional signal readout method (signal current injection method) of a pyroelectric C0D (pyro-C0D) in which a pyroelectric sensor is stacked on a COD scanning circuit. and a conceptual diagram of the driving potential.

Positive and negative charges are generated in the pyroelectric sensor according to the opening and closing of the optical chopper. Si-COD operates to read out only one of the charges. Therefore, in the conventional example, C
Half of the maximum transferable charge amount of the OD was used as a bias charge, and was electrically injected in synchronization with the opening and closing of the optical chopper.

In FIG. 10, positive and negative signal charges 1, 11 and 112 generated in the pyroelectric sensor (pyro sensor) 1o6 are transferred to the readout gate GR1 (1o3) according to the opening and closing of the optical chopper.
COD scanning units GT1 (104) and GT2 (10
5) K is transferred. At this time, the input diode section 101 is reset to the recent level 109 in synchronization with the opening and closing of the optical chopper, and then the bias charge 110 is reset.
is electrically injected, signal charges 111 and 112 of both positive and negative polarities of the pyro sensor are accumulated in the input diode section 101, and after a certain accumulation time, 1. Then, the COD scanning unit 102 reads the data. This is, for example, Earl Futon et al. Inflation Art
Physics (R+Watton.

etal, Infrared Phys) vol.
22. PP, 259-2751982.

Problems to be Solved by the Invention When attempting to electrically inject initial bias charges as in the conventional example, an input mechanism for bias charge injection (
For example, a new diode cut-off method must be added. As a result, the following problems occurred.

(1) The cell size of a unit pixel becomes large.

(2) The structure becomes complicated.

(3) Driving becomes complicated.

For this reason, with the extension technology of the conventional electrical injection method, the number of pixels (40
0HX500■) would not only increase the chip size, but would also be extremely difficult to drive.

The present invention has been made in view of these points, and an object of the present invention is to provide a novel structure for improving the signal readout method of a focal 5-beze type infrared imaging device.

Means for Solving the Problems The present invention solves the above problems by directing light (mainly light in the visible range or below) from the sensor surface or the back surface of the semiconductor substrate.
The storage diode of the scanning section is irradiated continuously or in synchronization with the opening and closing of the optical chopper for infrared light, and the signal readout operation is linked to this operation.

Function The present invention uses the above-described configuration to generate an initial bias charge in the storage diode using visible light, thereby increasing the positive and negative charges of the pyro sensor.
Enables reading of negative signal charges.

Embodiment An embodiment of the present invention will be described with reference to FIGS. 1, 2, and 3. Figure 1 is a schematic diagram of an imaging system that generates bias charges by irradiating visible light onto a Si (silicon)-COD storage diode used as a scanning circuit in a two-dimensional pyroelectric infrared imaging device. This is what is shown. Here, 1° is an infrared image, 11 is an infrared lens made of Ge, and 12 is a belt-shaped optical chopper that synchronizes with the vertical scanning of the TV screen and always maintains parallel to the horizontal scanning direction of the screen. Moving.

12-1 is an opening of a belt-shaped optical chopper; 12-2
is the belt feed hole. The infrared image 1o opened and closed by the optical chopper 12 forms an image on the pyro CCD 15.

On the other hand, the visible light 13 that generates bias charges is continuously irradiated onto the pyro C0D 15 via the reflection plate 14-1.

FIG. 2 is a schematic cross-sectional structural diagram of a unit pixel of a πoCCD. Here, the infrared image 10 enters a pyrofilm 21 such as a PVDF polymer film via a Cr electrode 2o. The pyrofilm 21 generates positive and negative signal charges in response to the opening and closing of the optical chopper 12, and potential fluctuations due to these signal charges are caused by the poly-8T (polysilicon) electrode 2.
2 to modulate the bias charge of the storage diode 23.

After a certain accumulation time, 7/・- through the readout gate 24
7 The signal is read into the COD transfer stage 25, vertically transferred, and then horizontally transferred and taken out to the outside as an image signal. Cr electrode 20. Pyrofilm 21, Poly
Both the −8t electrode 22 sufficiently transmit visible light 13 of a certain intensity or more, so it is possible to generate bias charges in the storage diode 23 by the effect of a Si pn junction photodiode. Other components include an St substrate 26, a gate oxide film 27, a field oxide film 28, and
9 is a channel stop, 3o is a transfer electrode formed of Poly-8t and also serves as a readout gate electrode, 31 is C
A light shield plate made of All, Mo, etc. that blocks infrared light 1o and visible light 13 from entering the OD transfer stage;
32 is an interlayer insulating film formed of a CV D S 102 film or the like.

Here, the operation of the present invention will be briefly explained using FIG. The optical chopper 12 opens in synchronization with the vertical scanning of the TV.
Figure d), then turn the pyrofilm 2
1 cannot read negative signal charges to the COD transfer stage unless there is bias charge in the positive and negative diodes 23.

Therefore, by irradiating continuous visible light (Figure b) and injecting a bias charge into the storage diode 23, in synchronization with the scanning pulse in Figure C, the charge in the storage diode 23 changes as shown in Figure e. The positive signal charge is taken out in the form of q(N+n) and the negative signal charge is taken out in the form of q(N-n).

Here, qN is the amount of bias charge, and qn is the amount of output charge of the pyro sensor.

As another embodiment of the present invention, a case where visible light is intermittently irradiated will be described with reference to FIGS. 4 and 5.

Hereinafter, in order to facilitate the explanation, the same components will be designated by the same numbers.

FIG. 4 schematically shows the imaging system of the present invention. Here, the visible light reflector 14-2 is attached to the closed portion of the optical chopper 12, and moves with the feeding of the belt. By optimizing the incident angle of the visible light 13, nine pages of pyro CcI) are irradiated in a moving manner in accordance with the movement of the visible light 13. Therefore, even if visible light is continuously irradiated, pi-bccD can be irradiated intermittently.

Next, the operation of this embodiment in which visible light is intermittently irradiated will be briefly described using FIG. Here, visible light is irradiated in synchronization with the opening and closing of the optical chopper 12, and only immediately after the opening and closing of the optical chopper 12 (Fig. b).・Therefore, the charge on the storage diode fluctuates as shown in Figure e. That is, when the optical chopper is open, positive signal charges qn are read out without bias charges.

When the optical chopper is closed, first a bias charge qN is generated by irradiation with visible light, and after a certain accumulation time, the negative signal charge qn is extracted to the outside in the form of q(N-n). . The same effect can also be obtained by intermittently blinking the visible light source itself.

As another embodiment of the present invention, a case in which visible light is irradiated from the back side of a semiconductor substrate side plate will be described with reference to FIGS. 6, 7, and 8. Hereinafter, for ease of explanation, the same components are given the same numbers.

FIG. 6 on page 10 schematically shows an imaging system in which visible light 13 is continuously irradiated from the back surface of the substrate of the pyro CCD 15. Here, the visible light 13 is the pyro CCD 15
is irradiated from the back surface of the substrate to generate bias charges in the storage diode 23.

FIG. 7 schematically shows an imaging system in which the visible light 13 is intermittently irradiated from the back surface of the substrate of the pyro-CCD 15. Here, the light chopper 12-1 for the infrared image 10 also serves as a light chopper for the visible light 13 on the back side of the pyro CCD 16. Therefore, even though continuous light is irradiated, the pyro CCD
15 allows for intermittent irradiation on the back side.

The same effect can also be obtained by intermittently blinking the visible light source itself.

FIG. 8 is a schematic cross-sectional structural diagram of a unit pixel, showing the element structure when visible light is irradiated from the back surface of the substrate of the pyro-COD. Here, the visible light 13 is irradiated from the back side of the substrate 26, enters the pn junction photodiode of the storage diode 11-7-23 through the opening 41 directly under the storage diode 2<3, and generates a bias charge. do. The parts other than the storage diode 23 are still covered with a light shield plate 40 made of Ae or the like to prevent visible light 13 from entering.

As another embodiment of the present invention, the visible light 13 is transmitted to a pyro CCD.
An element structure for efficiently irradiating the storage diode from the surface will be explained with reference to FIG. Hereinafter, for ease of explanation, the same components are given the same numbers. FIG. 9 is a schematic cross-sectional view of a unit pixel showing the device structure of an embodiment of the present invention. Here, the base electrode 6Q serving as the lower electrode of the pyrofilm 21 includes a storage diode 23.
An opening 51 is formed directly above the base electrode 6o, and the base electrode 6o is connected to the storage diode 23 via a through hole 52 of Po1y-8i. The base electrode 5o is made of Al,
It is made of metal such as Mo and is opaque to infrared light and visible light. The infrared image 1o shows the polarized charges in the pyrofilm 21, the base electrode 50, and Poly-S.
It is transmitted to the storage diode 23 via the t-through hole 52. The visible light 13 passes through the Poly-8i through hole 52 from the opening 51 formed on the base electrode 50, enters the storage diode 23, and generates a bias charge by photoelectric conversion at the ppn junction.

Effects of the Invention In the present invention, first, it is possible to form a bias light irradiation system synchronized with the opening and closing of the optical chopper using only a simple mechanical system. Then, in the storage diode on the St substrate,
It is possible to inject bias charges using bias light, and thereby it is possible to efficiently read out the positive and negative signal charges generated by the pyro and sensor to the outside. It's a size.
By adjusting the amount of bias light, the amount of bias charge can be injected to half of the maximum transfer charge amount of the COD in the case of continuous light, or at the maximum transfer amount of charge in the case of intermittent light, to each pyrosensor. The D-range of the signal charge can be maximized.

As a result of the above, the optical bias type pyroelectric infrared imaging device according to the present invention has the following features.

Page 13 (1) Simple element structure (no Easy to drive the element) This allows for a compact cell size, allowing for a large number of pixels in two-dimensional area sensors, which was impossible with conventional complex and large-scale configurations. In addition, the deterioration of S/N caused by the need for a conventional complicated input mechanism was significantly improved by adopting a simple drive system. Although the explanation was given here using COD as the base scanning circuit, similar effects can be obtained using MOS.
.

It can also be obtained using other solid state scanning circuits such as CPD.

[Brief explanation of the drawing]

Fig. 1a is a block diagram of an imaging system using a pyroelectric image sensor according to an embodiment of the present invention, Fig. 1 is a front view of an infrared shutter used in the system, and Fig. 2 is a unit of the image sensor. FIG. 3 is a cross-sectional view showing the schematic structure of a pixel; FIG. Figures a-e are 14-dimensional diagrams, Figures 6 and 7 are block diagrams of an imaging system in still other embodiments of the present invention, and Figures 8 and 9 are schematic structures of unit pixels. 10A is a circuit diagram showing an equivalent circuit of a unit pixel, and FIG. 10A is a conceptual diagram showing the operational potential of the same unit pixel. 12... Light beam, 13... Visible light, 14-1... Visible light reflector, 14-2...
...Visible light reflector, 15...Pyro CCD (
pyroelectric infrared image sensor), 2o...Cr1fL2
1...Pyrofilm, 22...Po
1y-8i electrode, 23...Storage diode, 4
0... Light shield plate, 41... Opening, 50... Base electrode, 51... Opening, 52... Po1y- 8i through hole. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 4
Figure 5

Claims (5)

[Claims] (1) A semiconductor substrate has a diode region of a conductivity type opposite to that of the semiconductor substrate, a scanning line for scanning signal charges accumulated in the diode region, and a pyroelectric infrared ray on an electrode connected to the diode region. A photoresist film is formed, and the photoresist film generates positive and negative signal charges according to the opening and closing of the optical chopper, which are generated by irradiation with infrared light by irradiating the diode with bias light from above the semiconductor substrate. A pyroelectric infrared imaging device characterized in that signal charges of both polarities of the photoresist film are read out to the scanning line. (2) The pyroelectric infrared imaging device according to claim 1, wherein the bias light is adiabatically irradiated in synchronization with opening and closing of the optical chopper. (3) The pyroelectric infrared imaging device according to claim 1, wherein the bias light is irradiated from the back surface of the semiconductor substrate. (4) A pyroelectric infrared imaging device according to claim 1, wherein the electrode is made of metal and a portion above the diode is opened to bias light. (5) forming an optical chopper in the shape of a belt, fixing a bias light reflection plate to the element side of the closed part of the belt-shaped chopper;
irradiating the bias light onto the reflector from the element side;
3. The pyroelectric infrared imaging device according to claim 2, wherein the reflected light of the bias light is irradiated intermittently as the belt-like chopper moves.