JP3327372B2 - Micro bolometer element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micro bolometer element which is an infrared sensor operating at room temperature, and more particularly to a small and highly sensitive micro bolometer element.

[0002]

2. Description of the Related Art A bolometer converts a change in physical properties due to the energy of an infrared electromagnetic wave into heat, and detects the change in temperature as a change in resistance.

[0003] By miniaturizing such a conventional bolometer, it is possible to achieve low heat capacity and low heat conductance.

[0004] However, since the light receiving area of the bolometer itself is micronized, the amount of infrared light incident on the bolometer also decreases, causing a problem that the sensitivity is reduced.

FIG. 5 is a configuration diagram showing an example of a conventional bolometer element which has solved such a problem. In FIG. 5, 1 is a substrate, 2 is a bolometer, 3 is a condenser lens, 100
Is incident light.

[0006] The incident light 100 is condensed by the condenser lens 3 and is incident on the bolometer 2 formed on the substrate 1. As a result, since a large amount of light is incident on the bolometer 2, a decrease in sensitivity can be prevented.

[0007]

However, in the conventional example shown in FIG. 5, a micrometered bolometer 2 shown in FIG. 5B using a condenser lens 3 having an outer diameter shown in FIG. Must be focused on a very small area.

That is, it is necessary to make the positional accuracy between the bolometer 2 and the condenser lens 3 strict. In addition, there is a problem that assembly parts for assembling with high precision are required.

Further, there is a problem that the use of the condenser lens 3 requires a space corresponding to the focal length of the condenser lens 3 and increases the volume of the bolometer element. Therefore, an object of the present invention is to realize a micro bolometer element which is easy to manufacture, has high sensitivity and is small in size.

[0010]

According to the present invention, there is provided a micro-bolometer element for converting a change in physical properties due to the energy of infrared electromagnetic waves into heat and detecting the change in temperature as a change in resistance. in, a plurality of micro prisms spatial propagation light is incident light
It is coupled to the propagating light in the planar optical waveguide, and
A light collecting means for condensing light in each of the constant areas and a bolometer arranged in the specific area are provided, and the light collecting means and the bolometer are integrated into a microstructure.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration sectional view and a configuration plan view showing an embodiment of a micro bolometer element according to the present invention.

In FIG. 1, reference numeral 100 designates the same reference numeral as in FIG. 5, 1a is a substrate, 2a is a bolometer, 4 is a plane optical waveguide, 5 is a micro prism, 101a, 101
b, 101c and 101d are propagation lights. 4 and 5 constitute the light condensing means 50.

A planar optical waveguide 4 is formed on a disk-shaped substrate 1, and a bolometer 2a is disposed at the center thereof. A plurality of circumferential micro-waveguides are placed on the planar optical waveguide 4.
The prism 5 is formed so as to be concentric with the bolometer 2a as a center.

The operation of the embodiment shown in FIG. 1 will be described with reference to FIG. FIG. 2 is an explanatory diagram for explaining the propagation of the incident light 100 paying attention to one micro prism 5.
In FIG. 2, 1a, 4, 5, 100 and 101a are the same as those in FIG.
The same reference numerals are used as in FIG.

The incident light 100 is incident from the direction perpendicular to the substrate 1a, and is incident on a region indicated by "a" in FIG.
Directly enter the bolometer 2a. On the other hand, the other incident light 100 enters the plurality of micro prisms 5.

For example, in FIG. 2, the refractive index of the planar optical waveguide 4 is "nf", and the refractive index of the micro prism 5 is "nf".
p ”, the incident angle of the incident light 100 on the micro prism 5 is“ α ”, and the refraction angle on the incident surface is“ β ”.
The incident light 100 propagates in the micro prism 5 with a propagation constant “βp”.

The propagation constant “βp” is βp = np · k · sin (α−β) (1) where k = 2π / λ (λ is a wavelength). It is expressed as

On the other hand, the propagation constant “β” in the planar optical waveguide 4
f ”is represented by βf = k · nf · cos θ (2) where the propagation mode in the plane action wave path 4 is“ θ ”.

Under the condition that equations (1) and (2) are equal, βp = βf = np · k · sin (α−β) = k · nf · cos θ (3) Is phase-matched with the planar optical waveguide 4 and distributed-coupled to form a propagating light 10.
The bolometer 2a propagates through the planar optical waveguide 4 as 1a.
To reach.

Therefore, when the condition of the expression (3) is satisfied, the wavelengths incident on the plurality of micro prisms 5 "
The incident light 100 of λ ″ is the propagating lights 101a to 101 in FIG.
The light propagates to the center of the concentric circle as shown by d and the like.

That is, all the incident light 100 incident on the substrate 1a is condensed on the bolometer 2a, which is the center of the concentric circle, so that infrared light can be detected with high sensitivity. In addition, the bolometer 2a and a plurality of micro
Since the prisms 5 are integrally formed, they do not need to be aligned with each other, and can be small in volume.

As a result, by integrally forming the bolometer 2a and the condensing means 50 on the substrate 1a, a micro bolometer element which is easy to manufacture, has high sensitivity and is small, can be realized.

FIG. 3 is a partial sectional view showing a second embodiment of the micro bolometer element according to the present invention. In FIG. 3, 1a, 4, 100 and 101a have the same reference numerals as in FIG. 1, and 5a and 5b are micro prisms.

The basic configuration of the embodiment shown in FIG. 3 is the same as that of FIG. 1, except for the micro prism 5a shown in FIG.
The point shown in FIG.

The micro prism 5 indicated by "b" in FIG.
The incident light 100 that has entered the end face of “a” reaches the bolometer 2 a (not shown) as described above.

On the other hand, the incident light 100 incident on the end face of the micro-prism 5a shown by "a" in FIG. 3 is reflected on the end face and incident on the micro-prism 5b shown by "c" in FIG. The light propagates through the micro prism 5b and the planar optical waveguide 4 to reach the bolometer 2a (not shown).

FIG. 4 is a sectional view and a plan view showing a third embodiment of the micro bolometer element according to the present invention.

In FIG. 4, reference numeral 100 denotes the same reference numeral as in FIG. 1, 1b denotes a rectangular substrate, 2b denotes a linear bolometer, 4a denotes a planar optical waveguide, 5c denotes a micro prism,
101e is propagation light. 4a and 5c constitute the light condensing means 51.

A planar optical waveguide 4a is formed on a rectangular substrate 1b.
And a plurality of linear micro prisms 5c are formed on the planar optical waveguide 4a so as to be arranged in parallel. Further, a bolometer 2b is arranged at one end of the planar optical waveguide 4a in the longitudinal direction.

The light collecting method of the embodiment shown in FIG. 4 is almost the same as that of the embodiment shown in FIG. 1 except that the propagating light 101e is not converged at one point but propagates in the longitudinal direction of the substrate 1b. Thus, the point is that the light is uniformly collected on the linear bolometer 2b.

With such a configuration, it is possible to apply not only to a circular bolometer but also to a linear bolometer.

In the above description, the light collecting means 50
Alternatively, a micro prism is illustrated as the component 51, but a grating coupling method, a taper coupling method, or the like may be used as a coupling method between the planar optical waveguide and the spatially propagating light.

[0033]

As is apparent from the above description,
According to the present invention, the following effects can be obtained. By integrally forming the bolometer and the condensing means on the substrate, a micro-bolometer element which is easy to manufacture, has high sensitivity and is small, can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration sectional view and a configuration plan view showing one embodiment of a micro bolometer element according to the present invention.

FIG. 2 is an explanatory diagram illustrating propagation of incident light focusing on a micro prism.

FIG. 3 shows a second example of the micro bolometer element according to the present invention.
It is a fragmentary sectional view which shows an Example.

FIG. 4 shows a third example of the micro bolometer element according to the present invention.
1 is a configuration sectional view and a configuration plan view showing an embodiment of FIG.

FIG. 5 is a configuration diagram illustrating an example of a conventional bolometer element.

[Explanation of symbols]

1, 1a, 1b Substrate 2, 2a, 2b Bolometer 3 Condensing lens 4, 4a Planar optical waveguide 5, 5a, 5b, 5c Micro prism 50, 51 Condensing means 100 Incident light 101a, 101b, 101c, 101d, 101e
Propagating light

──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01J 5/00-5/62 G01J 1/00-1/60 G11B 7/09-7/22

Claims (1)

(57) [Claims] 1. A micro bolometer element for converting a change in physical properties due to the energy of an infrared electromagnetic wave into heat and detecting the change in temperature as a change in resistance .
Is coupled to the propagating light in the planar optical waveguide.
And a bolometer disposed in the specific area, wherein the light condensing means and the bolometer are integrated into a micrometer.