JPH0159745B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an infrared detection device, and particularly to a multi-element infrared detection device suitable for tracking a target.

2. Description of the Related Art As an infrared detection device mounted on a flying object that performs target search and tracking using infrared rays, one having a photoelectric conversion unit in which four or more infrared detection elements are arranged in a cross shape is already well known. FIG. 1 shows an example of such a photoelectric conversion section. In this figure, numerals 1, 2, 3, and 4 are infrared detection elements that are electrically independent from each other, and are arranged and fixed in a cross shape on a support plate 5 made of an insulator to form a multi-element type detector. . An image of the target is projected onto this detector. Note that illustration of the imaging optical system is omitted.

However, the use of a detector such as that shown in FIG. 1 has the disadvantage of providing only coarse information regarding the direction of the target. The reason for this is that when the target image is on the surface of one infrared sensing element and never on the surface of other elements, for example, even if it is at position a in the figure, it will be at position b. This is because the same signal is obtained from the infrared detecting element 1 in both cases, and in this case, the direction of the target cannot be distinguished.

In addition to this, the multi-element detector of FIG. 1 has the disadvantage of being unduly noisy. The basic reason for this is that each element has a large area, and the thermal noise of an infrared sensing element is approximately proportional to the square root of the area. The large area of the sensor is unavoidably disadvantageous in terms of signal-to-noise.

The present invention has been made in view of the above-mentioned points, and has a photoelectric conversion section that combines a multi-element infrared detector in which fan-shaped infrared detection elements are arranged on the circumference and a charge transfer element. It is an object of the present invention to provide a novel infrared detection device that determines the direction of a target based on the temporal position of a signal indicating the target in an output signal.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows the structure of an embodiment of the infrared detection device according to the present invention, where D is a multi-element infrared detector (hereinafter simply referred to as a detector), and S is the detector D.
This is a shift register using a charge transfer element, which receives the output of a signal, converts it into a time-series signal, and outputs it. Detector D includes a large number of fan-shaped infrared detection elements (hereinafter abbreviated as detection elements) 101, 102, 10.
It has a structure in which 3, . . . 112 are arranged. In this embodiment, the sensing element is a photovoltaic type whose constituent material is indium antimonide (InSb). Each element is an n-type region formed on a common p-type substrate. Note that 5 is a support plate for the detection element. The charge transfer device (CTD) used as the shift register is a two-phase drive type whose substrate material is silicon Si. of the CTD20,
Input diodes 301, 30 are connected between the transfer electrodes 201, 202, 203, ... 224 and the detector D.
2,303,...,312, input gate electrode 21,
A temporary storage electrode 22 and a transfer gate electrode 23 are provided on the same Si substrate surface.
The number of diodes in the input diode group matches the number of sensing elements, and the number of sensing elements 101, 1
02, 103, ... are input diodes 30, respectively.
It is directly connected to 1,302,303,... The photocurrents of each individual sensing element in detector D therefore all flow simultaneously into each input diode. This current flows under the temporary storage electrode 22 through the input gate electrode 21 and is stored as a charge, and when the transfer gate electrode 23 opens (can pass through), it simultaneously flows into each bit of the CTD 20, and the current flows into each bit of the CTD 20.
It is transferred within the channel of CTD 20 in the direction of arrow A. The operation of this embodiment will be explained in more detail later in connection with the target direction detection mechanism, but only the configuration of the output circuit of the CTD 20 will be described here.

On the output side of the CTD 20, an output gate electrode 24,
A charge detection diffusion layer 25, a reset electrode 26, and a drain region 27 for charge disposal are provided, and a terminal _P5 taken out from the charge detection diffusion layer 25 is an output terminal for a detection signal. P ₁ to _{P 3} are input gate electrode 21 and temporary storage electrode 2, respectively.
2. Voltage supply terminals P ₄ and P ₆ for the transfer gate electrode 23 are output gate electrodes 24, respectively.
and a voltage supply terminal for the reset electrode 26.

Next, the operation of detecting the presence or absence of a target and its direction in the embodiment shown in FIG. 2 will be explained.

Each detection element 101, 102, 1 in FIG.
03,... and the input diode 301 of CTD20,
Connection with 302, 303,... and CTD20
As is clear from the charge transfer direction (arrow A),
From output terminal _P5 , detection elements 101, 102, 1
The signals generated at 03, . . . 112 appear in the same temporal order as the above code order. For convenience of understanding, let us assume that the image of the target applied onto the surface of the detector D is a minute light spot, and that this image, that is, the light spot, is now on the detection element 101 as shown at 28. , the charges of all elements are simultaneously
After completing the transfer within the CTD20 channel,
The charges generated by the target imaging light in the infrared sensing element 101 enter the charge detection diffusion layer 25 with the first transfer pulse, and the image charges are transferred to the output terminal.
It is taken out as an output signal from _P5 . On the other hand, the transferred signal charge passes under the reset electrode 26, enters the drain electrode 27, and is discarded to the outside from the terminal _P7 . If the target image is on the detection element 102 as shown in 29, the time at which the signal from the image appears at the output terminal _P5 is delayed compared to the case described above, and the time difference in both cases is equal to the repetition period of the transfer pulse train ( It is easy to understand that it is equal to (hereinafter referred to as T).

As can be seen from the above explanation, when the target image is on the detection elements 102, 103, 104,...
The times at which the signals appear at the output terminal _P5 are delayed by T, 2T, 3T, . Therefore, from the time when the output signal appears, it is known which sensing element the image of the target is on, and therefore the direction of the target can be determined with an error within the range of the apex angle of one sensing element.

FIG. 3 is a graph showing the relationship between the position of the target image and the time at which the signal appears. For convenience, the waveform of the signal is assumed to be a pulse having a constant width and wave height. Pulses 31a, 31b, and 31c have target images detected by infrared detection elements 101 and 10, respectively.
3,107, and pulse 31b is 2T and pulse 3 is lower than pulse 31a.
1c is also 6T behind. In this way, it is possible to know on which sensing element the target image is located from the time relationship of the signals.

The detector in Figure 2 is shown as having 12 sensing elements for convenience, but by reducing the apex angle of each sensing element and correspondingly increasing the number of elements, the measurement error in the direction of the target can be reduced. can be done. Note that the CTD 20 may be made of the same semiconductor material as the sensing element.

In the above discussion, we assumed the light spot of the target image for convenience, but if the target image has a certain area, it can be expressed in a polar coordinate system whose pole is the center of the circumference where the detection elements are arranged You can also know the radius of the image position. This point will be explained next using FIG. 4.

For convenience of understanding, FIG. 4A shows the sensing element group 1.
01 to 112 are simplified and slightly reduced,
Figure B shows the signal waveform.

In FIG. 4A, four circles 41 to 44 represent four different positions of the target image, each of which has a certain size, and the center of the image 41 is the arrangement of the sensing element group. It almost coincides with the center of the circle shown above, and the others are separated from the center of the circle in the order of the numbers. Figure B shows the signal waveform, waveform 51
54 correspond to the image positions 41 to 44 in FIG. 5A, respectively. The signal waveform 51 is almost direct current,
Similarly, 52 is a pulse with a wide width and a low peak value, which is also narrower and has a higher peak than waveform 53, and finally 54 is a waveform with the narrowest width and higher peak value. However, the waveform in this figure is after smoothing the output signal of the CTD 20. As is clear from the above, from the peak value and half-width of the signal waveform, the distance between the image of the target object applied onto the sensing element surface and the center of the disc-shaped infrared detector, in other words, the distance between the center of the disc-shaped infrared detector With the center of the device as the pole, it is possible to know the radius vector of the position of the image of the target object in polar coordinates defined on the sensing element surface.

In addition, if the target object cannot be regarded as a point light source, it can be determined whether the radius vector is changing in the direction of increasing or decreasing, and if the target object is far away and can be regarded as a point light source, If the infrared detector is placed at a position slightly shifted from the focal point, the size of the projected target object will show a constant size corresponding to the focal shift, so the half-width of the waveform of the smoothed time-series signal output is Since there is a one-to-one relationship with the absolute value of the radius vector, the radius vector can be known.

Therefore, the polar coordinates of the image of the target object can be determined from this vector radius and the declination angle in the polar coordinates of the position of the image of the target object, which can be determined from the temporal position of the peak signal waveform (time until the signal waveform appears). You can know the two-dimensional position above.

As is clear from the above description, the infrared detector of the present invention is completely solid-state, and by narrowing the width of the detection element, the accuracy of measuring the target direction can be made sufficiently high. It has various advantages such as a sufficient signal-to-noise ratio even when the target image is minute, and high-speed scanning is possible because it relies on electronic scanning using a CTD instead of mechanical scanning. Because of this, it is highly effective for use in photoelectric conversion sections of search and tracking systems that utilize infrared rays.

[Brief explanation of drawings]

Figure 1 is a top view of the main parts of a conventional infrared detection device.
FIG. 2 is a simplified top view of the infrared detection device according to the present invention, FIG. 3 is a diagram showing the output signal waveform when the target is a point light source in the embodiment shown in the previous figure, and FIG.
Similarly, B is a diagram for explaining the relationship between the output signal waveform and the image position when the target image has a certain size. 1-4: Infrared sensing element, 5: Support plate, D: Infrared detector, S: CTD, 101-112: Fan-shaped sensing element, 201-224: Transfer electrode, 301
~312: input diode, 21: input gate electrode, 22: temporary storage electrode, 23: transfer gate electrode, 24: output gate electrode, 25: charge detection diffusion layer, 26: reset electrode, 27: drain region.

Claims (1)

[Scope of Claims] 1. An infrared detection device configured to receive infrared rays from a target object using a plurality of detection elements in order to search and track a target object, wherein each of the detection elements has a fan-shaped shape. , comprising infrared sensing elements and charge transfer elements that are electrically independent from each other and arranged on the same circumference with the fan-shaped tips facing one point, and the electrical signals outputted by each of the infrared sensing elements. are input to different transfer stages of the charge transfer element at the same time, and the charges corresponding to these inputs are transferred to the output terminal of the charge transfer element and from the output terminal correspond to the array of each of the infrared detection elements. An infrared detection device characterized in that the signal is output as a series signal, and the output signal waveform is used to detect the direction and radius of the target object in polar coordinates.