JPH042929A - Infrared detector - Google Patents

Abstract

PURPOSE:To correct a measuring value properly by providing a detecting means for detecting the sensitivity of an infrared detector on the basis of both the detecting output of infrared rays radiated from a chopper and the infrared detector and, the temperatures of the chopper and infrared detector. CONSTITUTION:An infrared ray reflected from a surface 1 to be measured enters an infrared detector 5 through a polygon mirror 2, a condenser lens 3 and a chopper 4. A photosensor 6 detects the rotating position of the chopper 4. A clamp pulse is generated at 7 based on a signal indicating the reference position, and the detecting signal level of the detector 5 is clamped at a predetermined potential by 8. Moreover, the detecting signal of a predetermined detecting device is sample-held by 9 on the basis of the reference position signal and A/D converted at 10. The temperatures of the detector 5 and chopper 4 which are held constant by a cooling device 16 are measured respectively by temperature sensors 17, 18. The temperature at a predetermined position of the surface to be measured is calculated on the basis of each detecting value at a CPU 11. When the output of the detector 5 is sent sequentially to a multiplexer 13, an A/D converter 14 and an image memory 15, the temperature and image are displayed at a display part 12.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to temperature calculation means for an infrared detection device.

(Prior art) An infrared detector detects infrared rays from an object to obtain temperature information of the object, but the detection sensitivity of the infrared detector decreases over time, and the measurement circuit element When the characteristics of the temperature change, the calculated temperature value also changes. Therefore, it is necessary to correct changes in temperature values due to decreases in detection sensitivity and the like. Since the infrared detection device detects the difference from the reference temperature, in order to correct the sensitivity, two reference heat sources are provided, and the difference between the detection output of the infrared rays emitted from the two reference heat sources and the above two standards are used. A temperature conversion formula or conversion table for the detection output must be created according to the temperature difference between the heat sources, and the detection output from the object to be measured must be converted into a correct temperature value using the conversion formula or conversion table. However, in the past, there was no idea of providing another reference heat source in order to perform sensitivity correction, and only one reference heat source was provided for calculating the temperature.

(Problems to be Solved by the Invention) An object of the present invention is to provide an infrared detection device that can constantly detect intense infrared light even if the sensitivity of the detector is reduced.

(Means for solving the problem) In an infrared detection device, a lens that condenses infrared rays emitted from an object to be measured, an infrared detector that detects the energy of the condensed infrared rays, and an infrared detector that is kept constant at all times. a temperature control device that maintains the temperature at a temperature of and a means for inserting a mirror into the optical path so that the infrared rays are incident on the infrared detector, and the detection output of the infrared rays emitted from the chopper, the detection output of the infrared rays emitted from the infrared detector, the temperature of the chopper, and the temperature of the infrared detector are detected. Based on this, a means for detecting the sensitivity of the infrared detector was provided.

(Function) According to the present invention, the ambient temperature of the device is the same as the temperature of the chopper blades, and by measuring the ambient temperature, the chopper temperature can be constantly grasped. In addition, by holding the detector in a constant temperature device to keep the detector at a constant temperature different from the ambient temperature, and using the chopper and detector as two reference heat sources, changes in detector sensitivity can be accommodated. It became possible to correct the measured value to an appropriate value.

(Example) FIG. 1 shows an example of the present invention. In Figure 1, 1
2 is a polygon mirror, which has a plurality of reflective surfaces (temporarily 8 surfaces) with different inclination angles on the side surface, and is driven to rotate at a predetermined speed by a motor (not shown). is two-dimensionally scanned, and the infrared rays from the surface to be measured are reflected toward the condenser lens 3. The condenser lens 3 condenses the measurement light reflected by the polygon mirror 2 onto the detection surface of the infrared detector 5 . The infrared detector 5 has a plurality of detection elements arranged in a line, and each detection element receives reflected light from the polycon mirror. The apparatus of this embodiment obtains an image showing the distribution of infrared intensity using the outputs of the plurality of detection elements, and also calculates the temperature at a predetermined position of the measurement target based on the output of a predetermined detection element among these detection elements. is calculated. Reference numeral 4 denotes a chopper, which has eight blades as shown in FIG. A mirror 4B is provided on the surface facing the detector 5, and the surfaces of the other blades facing the detector 5 are blackened. These blades are arranged so as to face the boundaries of each reflective surface of the polygon mirror 2, and are arranged so that they face the slits between the blades or each reflective surface of the polygon mirror 2, and are integrated with the polygon mirror 2. It's rotating. The measurement light reflected by each reflective surface of the polygon mirror 2 is sent to the chopper 4.
In Fig. 6, a,
C is a period in which part of the infrared light path is blocked by the blade of the chopper 4; one is a period in which the infrared light path is completely unblocked by the blade of the chopper 4; d;
is the period during which the infrared light path is completely blocked by the blade of the chopper 4. e is a period during which infrared rays from the detector 5 are reflected and detected by the mirror blade portion 4B of the chopper 4 toward the detector.

The photosensor 6 detects the rotational position of the chopper 4, and a signal as shown in FIG. 3A is obtained. Based on the signal 4A from the notch 4A indicating the reference position of the chopper 4, the period d during which the infrared light path is completely blocked by the blades other than 4B of the chopper 4 is calculated, and the clamp pulse generation circuit 7 generates a clamp pulse during that period. is generated, and the clamp circuit 8 sets the detection signal level from the detector 5 to a predetermined potential (
2V). That is, in the period d, the black blade of the chopper is facing the detector 5, so during this period the detector responds to the temperature of the chopper 4, which is room temperature, which is changed by the signal voltage 2. It stipulates that.

Further, the timing C for detecting the infrared rays from the detector 5 itself reflected by the mirror blade portion 4B of the chopper 4 is calculated by CP IJ ], ] based on the reference position signal 4A, and the CPU 1. 1 or sample hold (S/H
) A pulse is sent to the sample-and-hold circuit 9, and the sample-and-hold circuit enters the period e.1) The detection signal of a predetermined detection element is sampled and held. Further, the timing B for detecting infrared rays from the above-mentioned predetermined detection element or a predetermined position of the measurement target is determined by CP tJ 1 based on the reference position signal 4A.
1 is calculated, and at that timing, the CPU 11 sends a sample bold (S/H) pulse to the sample bold circuit 9, and samples the output of the detection element 5a at that time. Then, the outputs sent to the sample hole 1 are A/D converted by the A/D converter 10, and then sent to the CPU II.
is input. In addition, the detector 5 is cooled by a cooling device 16.
The temperature is maintained at a constant low temperature, and that temperature is detected by temperature sensor 1.
7 is detected and input to the CPU 11.

Further, the temperature of the chopper 4 is detected by a temperature sensor 18 that detects the ambient temperature within the device, and is input to the CPU Ull. The CPU II calculates the temperature at a predetermined position of the measurement target based on the detected value obtained in this way.

On the other hand, the outputs of the plurality of detection elements of the detector 5 are clamped to a predetermined potential, are switched by the multiplexer 13, are sequentially A/1) converted, and are stored in the image memory 15.

The display unit 12 displays the temperature calculated by the CPU and the image stored in the image memory 15.

Next, the above temperature calculation method will be explained. The infrared energy from a predetermined position of the measurement target is E (Tt), and the infrared energy from the black chopper is E (1"ch). Also, when scanning the predetermined position of the measurement target, that is, the above timing B, The output of the predetermined detection element at timing B is Vl, the output of the predetermined detection element for period d, that is, the black chopper is V2, and the difference (Vl-
Let E be the energy for V2), E (T t
> −E+E (Tch)−...Ill. Here, since the temperature Tch of the chopper 4 is obtained by the temperature sensor 18, E(Tch) can be obtained from that value using Blank's formula, and since E is calculated from the outputs Vl and V2 of the detection element, E(Tt,) is obtained. Then, by converting this energy value E(Tt) into a temperature Tt, the temperature at the predetermined position can be obtained. Note that when performing this conversion, a table showing the relationship between energy and temperature is stored in advance, and the calculated energy value E
The temperature corresponding to (Tt) may be read out.

A correction method when the sensitivity of the detector 5 decreases will be explained. The detection value of the predetermined detection element during the period e is V3, the detection value of the temperature sensor 17 is Td, the detection value of the temperature sensor 18 is Tch, the sensitivity of the detection element when there is no decrease in sensitivity,
Letting K(Td) be the product of the coefficient for converting energy into voltage, V2-V3 - [IE (Tch) -E (
′r”d) ]xK(Td＞・・・・・・・・・・・・・
(2) holds true.

If the correction coefficient when the sensitivity decreases is a, then aV2-
aV3 [E (Tch) −E (Td)]
K (Td) Therefore, a-[E (Tch)-E (Td)] K (Td)
(V2-V3)・・・・・・・・・・・・・・・・・・
(3) becomes. In addition, [E (Tch)−E (Td)
] xK(1'd) is [E (Tch) - E (Td>] K (Td) for the combination of Tch and Td
is measured in advance without low sensitivity and stored in a table, and read out using the obtained 'I'ch and Td.Then, using the correction coefficient a, the output of the detection element is adjusted. Try to correct it.

In this embodiment, only the output of the detection element for determining the temperature is corrected, or the output of the detection element for obtaining the image showing the distribution of infrared intensity may also be corrected.

Alternatively, correction may be performed for all of the plurality of detection elements. In this case, another embodiment will be described.

Since the above K (Td) is a function specific to the detection element, for each element, the temperature Td of the detection element and K (T
A table showing the relationship d) is provided. On the other hand, [E (T
ch)-E (Td〉] is not related to the detection element, so the chopper temperature Tch, the detection element temperature Td and [
E (Tch) - E (Td)] may be provided in common. And [E (
Tch > −E (1”d)] IK(Td)
obtains K(Td> from the table corresponding to the detection element, and obtains [E (Tch )−E(T
d > ]. Then, for each element, Tcb, Td and [E (Tc h )
-E (Compared with the case where a table indicating the relationship Td>IK(Td) is provided, memory can be saved.

In addition, the sensitivity reduction is detected for only one specific detection element (for example, the detection element for temperature calculation in this embodiment), and the detection outputs of all detection elements are corrected based on the amount of sensitivity reduction. You can do it like this.

Furthermore, in this embodiment, the infrared detector is configured with a plurality of detection elements or with one detection element, and the image and temperature are obtained based on the output of this one detection element. Good too. In this case, if the sensitivity is corrected for one detection element, accurate values for both the image and the temperature can be obtained.

In the above embodiment, a mirror is provided on a part of the blade portion of the chopper 4, but FIG. 4 shows an example in which all the blade portions of the chopper 4 are painted black and a mirror is provided separately. The mirror is arranged at a position A, B, or C in the figure, and is inserted into the optical axis by a drive device (not shown) when measuring and correcting the sensitivity of the detector. Similar to the embodiment shown in FIG. 1, the detection signal that measures the temperature of the detector 5 itself reflected by the mirror is sampled by the sample hold circuit 9 using S'/H pulses that correspond to the drive timing of the drive device. will be held.

When inserting a mirror at position A or B, if the shape of the mirror is a concave surface centered on the light receiving element position of the detector 5, then
Infrared rays other than the detector 5 no longer enter the detector 5, and the influence of radiation from the surroundings can be removed.

When inserting the mirror in position C, the inside of the lens cap that is attached to the infrared incident window that receives infrared rays from the object to be measured (4-) may be misaligned with the mirror. In this case, the correction coefficient a is updated by putting a lens cap on if necessary.

In the above embodiment, the measured value is corrected in response to the decrease in sensitivity of the detector, but when the sensitivity falls below a certain value, that is, when the amount of decrease in sensitivity becomes unacceptable, Appropriate indicating means, e.g. warning lamps, fences
The user may be alerted by text display or the like.

(Effects of the Invention) According to the present invention, it has become possible to constantly measure the detection sensitivity and correct the measured value to an appropriate measured value using two reference heat sources, further improving the measurement accuracy of the device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a partial block diagram.

Claims (1)

[Claims] A lens that focuses infrared rays emitted from the object to be measured,
An infrared detector that detects the energy of concentrated infrared rays, a constant temperature device that keeps the infrared detector at a constant temperature, and a chopper that interrupts the infrared rays emitted from the object to be measured from entering the detector. and means for measuring the temperature of the chopper, and means for inserting a mirror in the optical path that reflects the infrared rays emitted from the infrared detector and makes them enter the infrared detector, and the detection output of the infrared rays emitted from the chopper. An infrared detection device comprising means for detecting the sensitivity of the infrared detector based on the detection output of infrared rays emitted from the infrared detector, the temperature of the chopper, and the temperature of the infrared detector.