JPS6037415B2 - infrared detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an infrared detection device that is used in a food heater or the like to control the temperature of food.

In particular, it concerns how to devise an optical system so that as much infrared energy as possible from a distant hot object enters the sensor. One way to effectively make light energy from a distant point enter a sensor is to use a lens system to condense the light. Lenses, such as telescopes, are used for visible light (0.4~0.
8rm wavelength). However, in infrared systems, the incident wavelength is long, ranging from a few peaks to 20 nm, and the lens absorbs light energy, so the lens must be made of an expensive material such as silicon or germanium, which absorbs little light energy. There was a problem. On the other hand, condensing means using a reflecting mirror is also effective in the infrared system.

This is because there are many materials with high infrared reflectivity, such as aluminum and tin, and almost perfect reflection can be achieved by finely finishing the surface. The present invention is a combination of an infrared sensor and a reflecting mirror.

FIG. 1 shows a conventional example of an infrared detection device installed in a food heater.

In the figure, 1 is a heating chamber, 2 is a food calendar, 3 is a food product, 4 is a food product, 5 is a wall of the heating chamber, and 6 is a motor for rotating the food food calendar table. 7 is the main body cover, 8 is the leg, and 9 is the chopper blade lo that has a cutout part for intermittent infrared rays.
configured to rotate.

11 is a means for detecting the presence or absence of a notch in the chopper blade 10.

12 is a reflector for bending the infrared optical axis; 13 is a hood for limiting the side temperature field; 14 is a parabolic mirror for condensing light;
5 is an infrared detection element that converts incident infrared energy into an electrical signal; 16 is a window provided in the heating chamber wall 5 for transmitting infrared rays.

The arrows are for schematically showing the state of light incident on the infrared detection element from the food. Next, the sensor S in the infrared detection element
Figures 2 to 4 show how to think about the energy that enters the light.
To explain using a diagram, in Figure 2, the object ○bj
The energy wi' that enters the sensor S through the field-limiting window W from the field is '.Ar, where the distance to the object is defined as evening.

4′ zero.

2Sinad8 Wi 2 Teiyu 2 Here, A is the proportionality constant 00 = skin 1 (character) becomes.

However, this incident light energy wi' needs to be modified due to the directivity of the infrared detection element.

The element directivity will be explained below. Figure 3A shows an infrared detection element. In the figure, S is the sensor, C is the element case,
A is an open window with a hole provided in a part of the case and sealed with an infrared transparent material such as germanium. L is a lead wire for taking out electric signals from the element. A phenomenon in which there is a difference in the electronic signal output of sensor S when light enters the central axis of the element (8 = 0) and when light enters at a certain angle (a = 8,) even if the incident light energy is equal for both. The element is said to have directivity.

Figure 3 shows an example of a characteristic in which the sensitivity is maximum at 8:0 and the sensitivity is half when 0 = raw, and the cosine changes as the value of 0 changes.

In this case, the relationship between sensitivity SE and angle a is SE(8)=S
maxcos(1.338). Smax is 8=0
This is the sensitivity when . Considering this kind of directionality,
The incident light energy wi to the sensor can be calculated by correcting the sensor directivity characteristic to the formula wi, and in the case of Fig. 2, Wi=K'
30Sin8・COS(1.338)d8 Here, K is the proportionality constant 80'mimicking n-・(character).

In Fig. 2, if r = 1, evening; 40, the input ineru becomes wiU = 3 x 10-3 x K.

Figure 4 shows an example of a parabolic reflector that focuses parallel rays onto a focal point.The intersection of the reflecting mirror and the central axis is called the origin ○ of the parabolic mirror, and the focused point is called f. . Next, FIG. 5 shows an example of a combination configuration of the parabolic mirror shown in FIG. 1 and the infrared detection element. The features of this configuration are the side overflow object ○bj, the focal point f of the mirror, and the sensor S.
, Sekihole window A, and mirror origin ○ are arranged on the central optical axis in this order. This kind of configuration is often used in visible light telescopes and is very effective when the field of view can be made large. However, as in the embodiment shown in FIG. 1, if the diameter of the barrier hole 16 formed in the heating chamber wall 5 cannot be made very large, the infrared detection element 15 blocks light from entering the parabolic mirror 14, so it is not necessarily optimal. No, no.

When looking into a concave field of view (for example, 2 object lines) as shown in Fig. 5 with the parabolic mirror 14 at the focal point distance f=2
The incident light energy is Wil=K′; Sin8・CO
S (1-338) da to 81 = ne n-1 (house.

>in .

Calculate by inserting 2=tan-・(vessel) wi,=1
．． We get 36×10-1×K.

In FIG. 2, the input energy wi is when the field of view is 2 meters wide and the distance between the sensor S and the object ○bj is 40 meters.

wi. =3.0×10−3×K, which is about 49 tones compared to the above wi. On the other hand, when the actual measured values were obtained for the case of FIG. 2 and the case of FIG. 5, wi, was wi.

A 5M sound was obtained, which closely approximated the above calculated value, and it was found that the above calculation formula was correct. The present invention has been made based on the above concept, and embodiments of the present invention will be described below with reference to FIGS. 6 and 7.

14a is an objective mirror, and 15a is an infrared detection element, which are arranged in the following order: a side-warming object (object) ○, an aperture window A, a sensor S, the focal point f of the objective mirror, and the origin ○ of the mirror. .

With such a configuration, infrared incident light energy can effectively enter the sensor even if the field of view diameter is small.

Focusing distance f = 0.4 When looking into the visibility = 12 side as shown in Fig. 6 with the objective mirror 14a of the fence, the sensor input energy
One is Wne=K' declaration Sin8-C.

Sku1-338) 83=ne n → (bag) 84=ne n on d8
By adding i (cloud), w;2 >15×10-1×K
becomes.

In Fig. 5, the input energy equivalent to or more than that when viewing the field of view diameter ◇ = 2 enemies can be input with a field of view concave = 12 skin. As described above, according to the present invention, sufficient input energy enters the sensor even if the field of view is small, so when the sensor is applied to a food heater or the like, the hole in the wall may be small.

Furthermore, assembly is also easier than when an infrared detection element is provided in the infrared light entrance path of the optical system.

In the above description, the mirror is all parabolic, but the parabolic mirror may have a shape approximating a curve or a straight line.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a food heater equipped with a conventional infrared detection device, Figure 2 is an explanatory diagram when no lens or reflector is interposed between the object and the sensor, and Figure 3 A. The mouth is infrared rays. A cross-sectional view of the detection element and a characteristic diagram for explaining the directivity of the element, Fig. 4 is an explanatory diagram of a general parabolic mirror, Fig. 5 is a configuration diagram of a conventional infrared detection device, and Fig. 6 is a diagram illustrating the directivity of the element. FIG. 7 is an enlarged view of the parabolic mirror and infrared detecting element shown in FIG. 5. FIG. ○Ke...Target, A...Aperture window of element, S...Sensor, f...Convergent point of objective mirror, 0... ...Origin of objective mirror, 14a...
- Parabolic mirror, 15a... Infrared detection element. 1st
Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. In a combination of an infrared sensing element having an aperture window that transmits infrared rays and a parabolic mirror that condenses infrared rays, the infrared sensing element is placed on the central axis of the parabolic mirror, and the aperture window is It is configured to be located at a position further away from the convergence point of the parabolic mirror when viewed from the origin of the parabolic mirror, and the object whose temperature is to be measured, the aperture window, the sensor, and the origin of the parabolic mirror are arranged in the following order: An infrared detection device characterized in that it is configured to be located at.