JPS6035014B2 - infrared detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an infrared detection device, and an object of the present invention is to provide a device that can optically modulate the amount of received infrared light with a simple circuit.

An infrared detection device using the pyroelectric effect utilizes the fact that an element whose temperature is increased by input infrared energy generates a charge specific to the material.

A subsidiary feature is that when using this element, when detecting the amount of charge generated by the element, the current i is i = K (
Since there is a relationship between the coefficient of the sea bream and the constant temperature change over time, increasing the current value will increase the skin temperature. It needed to be modulated.

Specifically, a chopper that chops incoming infrared light by opening and closing the window of the element with a mechanical blade was essential.

The circuit using this chopper requires the device to be large and expensive, and because it looks at the difference signal between the temperature of the object and the temperature of the chopper blade, even if the object is at the same temperature depending on the temperature of the blade. If the signal changes and correction is required, and if the difference between the target temperature and the chopper temperature is the same, the signal will have the same amplitude even if the chopper temperature is 1 degree higher or 1 degree lower than the target temperature. , it is necessary to perform synchronous detection to discriminate between these, which has many drawbacks such as an increase in the number of parts and a complicated circuit.

The present invention provides an infrared detection device that does not require a chopper in order to solve these problems, and one embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an infrared detection element, and a series connection circuit including a capacitor 2 and a modulation signal generator 3 is connected to both ends of the element.

The intersection of the infrared detection element 1 and the capacitor 2 is an FET (
A resistor 5 is connected between the output terminal of this FET 4 and the ground. 6 is an output terminal.

The modulation signal generator 3 generates a voltage modulated by a predetermined frequency signal, and charges the infrared detection element with charge via the capacitor 2 at regular intervals.

Since this charge is equivalent to a resistor Rs and a capacitor Cs connected in parallel as shown in FIG. 2, it is discharged through the resistor Rs and through the input impedance of the transistor 4 in FIG. Since the amount of charge Q and the capacitance Cs of the infrared detecting element 1 have the relationship Vs=Q/Cs with the voltage Vs across them, a voltage proportional to this charging/discharging charge is generated.
When infrared light is incident there, a generated charge amount ΔQ corresponding to the energy of the incident light is generated. Therefore, VS' = VS + △V)
=Q There is a voltage change △V that causes damage.

By knowing this voltage change ΔV, the amount of infrared light incident is measured.

If the modulated electrical signal is applied by dividing the voltage using a resistor or a capacitor, the voltage across the element 1 can generate a voltage proportional to the charge of the element 1.

In addition, since pyroelectric infrared detection elements are generally made of a transparent material, they exhibit a large resistance value of about IMO or more, and signal processing is facilitated by impedance conversion using a transistor or the like. .

As described above, according to the present invention, in the infrared detection device, a modulated voltage is applied to the infrared detection device element, so a mechanical chopper is not required, and the device can be made smaller and cheaper. This has the effect of eliminating the need for correction work, and resulting in a simple circuit with a small number of parts.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an infrared detection device according to an embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram. 1... Infrared detection element, 2... Capacitor, 3... Modulation signal generator, 4... Transistor, 5... Resistor. Figure 1 Figure 2

Claims (1)

[Claims] 1. A device comprising: an element that receives infrared rays and generates a charge according to the amount of received light; and means for applying a modulated voltage to the element to optically modulate the amount of received light. Infrared detection device. 2. The infrared detection device according to claim 1, characterized in that a transistor for reducing impedance is connected to the output end of the element.