JPS63208804A - Wavelength selective condenser - Google Patents

Abstract

PURPOSE:To detect light with specific wavelength in a specific direction with high sensitivity by providing a hologram which has the function of a convex lens or concave mirror and a pinhole formed in an optical path of light transmit ted or reflected by the hologram. CONSTITUTION:This condenser has the hologram 1 which has the function of the convex lens or concave mirror and the pinhole 3a formed in the optical path of light transmitted or reflected by the hologram. A shield plate 3 is at a distance (l) from a hologram lens 1 and the position of its focus is coincident with the part of the pinhole 3a. The light with the specific wavelength in light in a direction A which is the specific direction where diffraction is caused is focused at the distance (l) and almost all of the light passes through the pinhole 3a and exits. The remaining wavelength light even when traveling straight in the hologram lens 1 or diffracted is converged on a position distance from the position of the pinhole 3a, so it can not pass through the shield plate 3. Only the specific-wavelength light exits in a direction B, so a photosensor 7 is provided at the position to accurately select and measure the specific wavelength in the specific direction by a photodetector for specific wavelength.

Description

Detailed Description of the Invention Purpose of the Invention [Industrial Field of Application] The present invention provides a wavelength-selective light condensing device which has high selective light condensing properties and is particularly useful for an infrared sensor that distinguishes infrared rays by wavelength and can easily detect them. Concerning vessels.

[Prior Art] Conventionally, there is an infrared sensor in which a lens made of optical glass or quartz glass is attached as a condenser to an element that detects infrared rays or the like. For example, sensors for automobiles that detect people and obstacles.

[Problems to be Solved by the Invention] These lenses have low transmittance for infrared rays, etc., and cannot be expected to increase the amount of light, so their sensitivity as a sensor is also low compared to the amount of light. Furthermore, if it is desired to focus a specific wavelength, a wavelength selection filter is required, which is expensive.

Structure of the Invention Therefore, the present invention aims to provide a condenser with good transmittance and a simple structure, and employs the following structure.

[Means for Solving the Problems] The gist of the present invention is to provide: a hologram having the function of a convex lens or a concave mirror; a pinhole provided in an optical path passing through or retracting the hologram; A wavelength-selective concentrator comprising:

[The effect cohologram produces a diffraction effect at a predetermined angle for a designed specific wavelength, but when the wavelength is different, the diffraction angle is different, which is so-called chromatic aberration. The chromatic aberration caused by the diffraction effect of a hologram is about 10 times larger than that of a normal lens that uses refraction.

Therefore, by placing a pinhole at a position where a specific wavelength converges, it is possible to almost completely block out light of other wavelengths and selectively collect and extract light of a specific wavelength.

Next, the present invention will be explained in detail. The present invention is not limited to these, but includes various embodiments without departing from the gist thereof.

[Embodiment] FIG. 1 shows a perspective view of an embodiment of the present invention. The wavelength selective condenser of this embodiment has a configuration in which a shielding plate 3 is provided in parallel to a phase type hologram lens 1. The hologram lens 1 is made by laminating a glass plate 1a with a thickness of several hundred um and a gelatin film 1b with a thickness of several μm.The gelatin film 1b has a structure in which light of a specific wavelength that passes through the gelatin film 1b is separated by a distance Q due to a diffraction phenomenon. The interference fringes 5 are designed to converge to approximately one point. This may be done by dividing a laser beam from the same light source into two optical paths and exposing the gelatin film 1b, or by calculating and drawing an interference pattern by computer calculation. When drawing directly, it may be drawn directly on the glass plate la, and the gelatin 111b may be omitted.

The shielding plate 3 is located at a distance Q from the hologram lens 1, and the convergence point, that is, the position of the focal point coincides with the pinhole 3a portion of the shielding plate 3.

With such a configuration, light of a specific wavelength among the light from the input direction, which is a specific direction in which diffraction occurs, is focused at a distance Q from the hologram lens 1, and the pinhole 3a of the shielding plate 3 exists at that position. Therefore, almost the entire amount passes through the pinhole 3a and exits in the B direction. Even if light of other wavelengths passes straight through the hologram lens 1 or is diffracted, it does not pass through the shielding plate 3 because it converges at a position far away from the position of the pinhole 3a.

Therefore, only the specific wavelength light passes through in the direction B, so if the optical sensor 7 is installed at that position as shown in FIG.
As a specific wavelength photodetector, it is possible to accurately select and measure a specific wavelength from a specific direction.

Further, since the glass plate 1a and the gelatin can be extremely thin, detection can be performed with high sensitivity using a small amount of light.

Next, FIG. 3 shows an application example of the above photodetector. In this example, a body temperature detection sensor 13 is used to control the louver 11 of the air conditioner E/C.
The case where it is used as This body temperature detection sensor 13 is
In the cylinder 13a, the hologram lens 1, the shielding plate 3, and the optical sensor 7 are arranged in the order from the opening it (13b),
External light, here infrared rays, is detected through the opening 13b.

- The hologram lens 1 is designed and arranged so that the infrared rays emitted from the human body are focused on the pinhole of the shielding plate 3 by diffraction. Therefore, the optical sensor 7 detects infrared rays emitted by the human body. That is, human body M
This means that it is possible to detect the direction in which . As shown in FIG. 4, even if there is an animal C such as a cat, the wavelength is different, so the body temperature detection sensor 13 can sufficiently detect the difference.

Returning to FIG. 3, the body temperature detection sensor 13 is oscillated by a certain angular width by driving the motor 17 by the motor control circuit 15. The angle is detected by the encoder 19 and input manually to the louver control circuit 21. The louver control circuit 21 also manually receives the infrared detection results from the body temperature detection sensor 13. This louver control circuit 21 is
The position where the infrared rays are strongest is determined from the two data, and it is assumed that there is a person in that position.
A control signal is output to the louver drive circuit 23 to direct the louver in that direction.

In this way, air with controlled temperature and humidity is effectively supplied to humans. If there are multiple people, the measured intensity peak of the infrared rays will be 'IN I&', but in this case, the louver 11 may be directed equally to each peak point.

Figure 5 shows another example of application. This example is applied to a car and is used to track a car in front.

As shown in the figure, if an exhaust pipe detection sensor 33 similar to the one described above is installed in front of the vehicle 31 to detect infrared rays of a wavelength generated in the exhaust gas temperature range, it is possible to detect heat-generating substances such as burning cigarettes discarded on the roadway. The exhaust pipe 39 of the vehicle 37 in front can be captured without detecting the vehicle 35, and more reliable tracking becomes possible.

As mentioned above, the wavelength-selective light collector of this example has a simple structure, high transmittance, and can collect light of a specific wavelength from a specific direction with high precision, making it extremely useful for use in optical sensors. It can be measured with high accuracy and sensitivity, and can be used in various devices to perform accurate control.

In this respect, especially when used to detect infrared rays, absorption by optical glass or quartz glass is reduced because the lens is thin, resulting in high accuracy.

Further, unlike lenses that utilize normal refraction, hologram lenses have an order of magnitude greater chromatic aberration, making them easier to use as spatial filters. In other words, it is sufficient to align the pinholes with an accuracy that is one order of magnitude lower, making it easier to position or change the position of the pinhole portion, and increasing the accuracy. In this way, the position of the pinhole can be easily changed, and the hologram lens can be easily changed to a desired wavelength, so 5. The wavelength to be detected can be easily changed.

Furthermore, the hologram lens itself has high directivity, making it easy to identify the object to be measured and positioning the object with high precision. At the same time, the wavelength range to be diffracted is determined, so even if the target is white light or natural light, only a specific wavelength range is selected from among them, eliminating the need for color filters, saving resources and lowering costs.

Note that by making the shielding plate in which the pinhole is formed movable along the optical axis, it is possible to change the measurement wavelength within the diffraction wavelength range.

Further, although the embodiment uses a transmission type hologram lens, a reflection type hologram such as a concave mirror may be used. In that case, there will be a shielding plate on the incident side.

Effects of the Invention The wavelength selective condenser of the present invention includes a hologram having the function of a convex lens or a concave mirror, and a pinhole provided in an optical path that is transmitted or reflected by the hologram. Light of a specific wavelength can be detected with high sensitivity. Moreover, a condenser with any focal point can be easily created by simply setting the interference fringes of the hologram and adjusting the position of the pinhole.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the wavelength selective condenser of the present invention, Fig. 2 is an explanatory diagram of its function as a photodetector, and Fig. 3 is a photodetector used as a louver adjustment means of an air conditioner. Figure 4 is a graph showing the difference in wavelength and intensity of infrared rays from an object, and Figure 5 is an illustration of the case where a photodetector is used as an exhaust pipe detection sensor for vehicle tracking. . 1... Hologram lens 3... Shielding plate 3a... Pinhole 7... Optical sensor

Claims (1)

[Scope of Claims] 1. A wavelength-selective condenser comprising: a hologram having the function of a convex lens or a concave mirror; and a pinhole provided in an optical path that is transmitted or reflected by the hologram. 2. A wavelength-selective condenser according to claim 1, wherein the hologram is designed for infrared light. 3. The wavelength-selective condenser according to claim 1 or 2, wherein the pinhole is arranged at the focal point of the wavelength light diffracted by the hologram.