JPH06221919A - Branching/condensing element for multielement pyroelectric detector - Google Patents

Abstract

PURPOSE:To provide a branching/condensing element for multielement pyroelectric detector in which infrared rays from analytic cells can be branched and condensed uniformly by each light receiving electrode through a simple structure. CONSTITUTION:The braching/condensing element comprises a pair of Fresnel lenses 2, 3 wherein one Fresnel lens is constituted of a Fresnel cylindrical lens split into P sections so that the parallel light component of infrared light passed through a rectangular plane part 2a having a groove M forms P (natural number) focal points whereas the other Fresnel lens is constituted of a Fresnel cylindrical lens split into Q sections so that the parallel light component of the infrared rays passed through a rectangular plane part 3a having a groove (m) forms Q (natural number including P) focal points with the grooves M and (m) intersecting perpendicularly each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a branching / focusing element of a multi-element type pyroelectric detector, for example, a multi-component non-dispersive infrared analyzer (hereinafter referred to as N Dispersive Infrared Analyzer).
When making parallel light components of infrared light that have undergone characteristic absorption according to the type and concentration of the gas to be measured in the analysis cell of DIR) enter the respective light receiving parts of the multi-element pyroelectric detector,
The present invention relates to a branching / focusing element that is arranged between an analysis cell and a pyroelectric detector and that branches infrared light from the analysis cell and efficiently collects it on each light receiving section.

[0002]

2. Description of the Related Art In each light receiving portion of an NDIR multi-element type pyroelectric detector, for example, HC, C are used as a three-component gas.
In order to receive the three gas species of O and CO ₂ , a total of four light receiving sections including one light receiving section for the reference output gas (comparative gas) are required. In order to reduce the size of the device and simplify the structure, it is effective to integrate the four light receiving parts into one detector. At this time, since four light receiving electrodes are formed on one pyroelectric member in the detector, there is an advantage that variations in various characteristics such as sensitivity and temperature coefficient thereof can be reduced.

On the other hand, it is necessary to consider the crosstalk between the light-receiving electrodes when the number of elements is increased. For this reason,
In order to branch and condense each light receiving electrode, a plurality of slits or a so-called four-division Fresnel lens that forms four focal positions after passing infrared light has been proposed.

In the former case, a plurality of slits are laminated in parallel with the light-receiving electrode surface so as to branch and guide the infrared light from the analysis cell to each light-receiving electrode surface, so that the height in the infrared-light incident direction is increased. A branch / guide passage is formed in each direction to reach each light receiving electrode surface. Also, the latter is usually a single S
Using an i-plane substrate, four Fresnel lenses each having a plurality of concentric circular grooves are formed on the plane to form a four-division Fresnel lens that forms four focal points.

[0005]

However, the former one has a complicated structure in which branch / guide passages are formed by stacking slits on the light-receiving electrode surface, and a certain area occupied by the slits is required. Moreover, since a plurality of slits are used, there is a risk that time will be spent in the assembly process.
Furthermore, since the branching / guide passage has a narrow shape from the entrance to above the light receiving electrode surface of the exit, among the parallel light components of the infrared light incident on the entrance from the analysis cell,
Part of the light may be reflected by the slit near the exit, and eventually only the remaining infrared light may be received by the light-receiving electrode surface, and there may be variations in the stacking form of the slits. .

Further, in the latter case, the groove of the Fresnel lens is S
Although the i-plane substrate is processed into concentric circles by etching, isotropic etching, which is disadvantageous in terms of processing accuracy, must be used for this type of processing, rather than anisotropic etching, which is advantageous. It is difficult to get high. Further, it is generally difficult to form concentric circular grooves by machining, and in forming the grooves, a lot of man-hours are required in the case of machining, which may result in unsuitable for mass production.

In short, it is difficult for these branching / focusing elements to uniformly branch / focus the infrared light from the analysis cell on each light-receiving electrode surface.

The present invention has been made in view of such circumstances.
It is an object of the present invention to provide a branching / focusing element of a multi-element type pyroelectric detector which has a simple structure and can uniformly branch / focus infrared light from an analysis cell on each light receiving electrode.

[0009]

According to the present invention, a parallel light component of infrared light from an analysis cell, which has received characteristic absorption according to the type and concentration of a gas to be measured in the analysis cell, is branched to form a multi-element device. In the branching / focusing element for focusing on each light receiving part of the Pyroelectric detector, the infrared rays are composed of a pair of Fresnel lenses, and one of the pair of Fresnel lenses passes through a rectangular flat part having a groove. The parallel light component of the light is composed of Fresnel cylindrical lenses that are P-divided so as to form P (P is a natural number) focal positions, and the other is parallel to the infrared light that has passed through the rectangular plane portion having the groove. The light component is Q (Q is P
A natural number including the number of), and is configured by a Fresnel cylindrical lens that is Q-divided to form focal points.
Furthermore, the branching of the multi-element pyroelectric detector in which each Fresnel lens is arranged so that the grooves of the rectangular flat surface are orthogonal to each other
It is a light collecting element.

The branching / focusing element according to the present invention is a multi-element device that branches parallel light components of infrared light from the analysis cell that have undergone characteristic absorption according to the type and concentration of the gas to be measured in the analysis cell. To collect light on each light receiving portion of the type pyroelectric detector. For example, as shown in FIGS. 3 and 4, an analysis cell,
It is used by being arranged between an optical filter provided in front of the multi-element type pyroelectric detector. The location of the branching / focusing element may be anywhere between the analysis cell and the multi-element pyroelectric detector. The point is that it may be at a position where the parallel light component of infrared light from the analysis cell is incident.

In use, it is preferable that the grooves of the rectangular plane portions forming the P-divided Fresnel cylindrical lens and the Q-divided Fresnel cylindrical lens are arranged so as to be orthogonal to each other.
It is preferable that the rectangular flat surface portion be linearly grooved in one direction as shown in FIGS. 5, 6, or 8 and 9.

As a most preferable form of the branching / focusing element of the present invention, a pair of Fresnel lenses are formed on two rectangular flat portions, and P is formed on the first rectangular flat portion.
A split Fresnel cylindrical lens is formed,
In addition, a Q-divided Fresnel cylindrical lens is formed on the second rectangular plane portion.
In use, these two Fresnel cylindrical lenses are attached so that their grooves are orthogonal to each other. For example, as shown in FIG. 1, FIG. 2, FIG. 5, and FIG. 6, two Fresnel cylindrical lenses (vertical lens 2 in which a linear groove is formed in a rectangular plane portion and the linear groove is arranged in the vertical direction when used) Then, the horizontal lenses 3) having linear grooves arranged in the horizontal direction are made orthogonal to each other and are bonded by a known direct bonding method or anodic bonding method.

Further, as another mode of the branching / focusing element of the present invention, a pair of Fresnel lenses are formed on one rectangular flat surface portion, and P is divided on both surfaces of the rectangular flat surface portion. Examples thereof include a Fresnel cylindrical lens and a Q-divided Fresnel cylindrical lens. At this time, linear grooves are formed on both surfaces so as to be orthogonal to each other. The manufacturing method is shown in Figure 1.
6 to 19 are shown.

At this time, the grooves are processed by using anisotropic etching which is advantageous for this kind of processing.

The branching / focusing element of the present invention as described above is arranged on the optical axis of infrared light so that the Fresnel lenses are arranged such that the grooves of the rectangular plane portions are orthogonal to each other to perform branching / focusing. be able to. The form of this branching / focusing is shown in FIGS.
It is based on the principle shown in. In FIG. 8 and FIG. 9, for example, two two-sided Fresnel cylindrical lenses 2 and 3 each having a rectangular flat surface grooved linearly in one direction are prepared (see FIGS. 1 and 2). Similarly, grooves M and m are linearly processed, and each can function as a two-divided Fresnel cylindrical lens. That is, both of the two-sided Fresnel cylindrical lenses 2 and 3 function so that after the infrared light passes, the focal point is located on the straight lines T and t parallel to the linearly formed grooves M and m. Moreover, at the time of setting, the parallel light components of the infrared light that have passed through the vertical lens and the horizontal lens are focused on the same plane as f ₁ , f ₂ , f ₃ , f ₄ as shown in FIG.
It is possible to tie In this way, by combining the two Fresnel cylindrical lenses 2 and 3 at an angle of 90 °, the parallel light component of the infrared light from the analysis cell is uniformly split into 4 (= 2 × 2). Can collect light. In addition, as shown in FIG.
The same can be done with a single branching / focusing element having a split Fresnel cylindrical lens and a split Fresnel cylindrical lens.

[0016]

According to the above construction, the P-divided Fresnel cylindrical lens and the Q-divided Fresnel cylindrical lens are arranged so that the grooves of the rectangular plane portions thereof are orthogonal to each other. The parallel light component of infrared light from the analysis cell, which has received characteristic absorption according to the type and concentration of gas, is uniformly branched and condensed without being biased to a specific light receiving electrode formed on the multi-element pyroelectric detector. Therefore, crosstalk between the light receiving electrodes can be reduced with a simple structure.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited thereby. 1 to 7 show a first embodiment of the present invention. First, in FIGS. 1 to 4, the branching / focusing element S of the multi-element pyroelectric detector is
Multi-element pyroelectric detection is performed by branching the parallel light component of infrared light from the analysis cell 1 that has received characteristic absorption depending on the type and concentration of the gas to be measured including the three gas types CO and CO _2. The light is focused on each of the light receiving portions of the container 7, and is composed of a pair of Fresnel lenses 2 and 3 each of which is composed of a rectangular flat surface portion linearly grooved in one direction.

Further, a pair of Fresnel lenses 2 and 3 are respectively formed on the two rectangular flat surface portions 2a and 3a, and the first rectangular flat surface portion 2a having the groove M as the Fresnel lens 2 is divided into two Fresnel cylindrical. The lens 2 is formed, and as the Fresnel lens 3, the Fresnel cylindrical lens 3 divided into two is also formed in the second rectangular flat surface portion 3a having the groove m. In use, these two Fresnel cylindrical lenses 2 and 3 are bonded so that the grooves M and m are orthogonal to each other. The intervals between the grooves are different for each groove. For example, as shown in FIG. 5 and FIG.
The sparse parts 4, 5 and the dense parts 6, 7, 8 are formed on the top. The sparse and dense portion is set in advance so that the focal position is on a straight line (desired light receiving portion) parallel to the linearly formed groove after passing infrared light.

Two Fresnel cylindrical lenses 2,
3 is used, the Fresnel cylindrical lens 2 is used as a vertical lens and the linear groove M is arranged in the vertical direction so that the grooves M, m are orthogonal to each other, and the Fresnel cylindrical lens 3 is used as a horizontal lens, and the linear lens is used in the horizontal direction. Grooves are arranged and bonded by a known direct bonding method or anodic bonding method.

Below, the Fresnel cylindrical lens 2,
The manufacturing method of No. 3 will be described. First, FIG. 11 and FIG.
As shown in FIG. 5, the n-type Si substrate 10 is patterned along the crystal axis using the (1 0 0) plane. At this time, selective exposure is performed using a known photomask 11 designed to have a desired groove pitch. Then, the unexposed portion is removed to leave the groove pattern 12 (see FIG. 13).
Next, the groove M (or m) is processed by using anisotropic etching. As a result, the sparse portions 4, 5 and the dense portions 6, 7, 8 having the desired groove pitch with good processing accuracy can be formed (see FIG. 14). At this time, as shown in FIG. 7, a plurality of lens chips 12, 12, ... Are formed on the Si substrate 10 in a lattice shape. However, because anisotropic etching is used, the variation between the lens chips 12, 12 is caused. Can be made smaller. Then, as shown in FIG. 15, Si having sparse portions 4, 5 and dense portions 6, 7, 8 is formed to reduce surface reflection.
The antireflection coating films 13 and 13 may be formed on both surfaces of the substrate 10.

After that, two Si substrates 10 each having a linear groove formed on one surface thereof are bonded together. After the bonding, the lens chips 12, 12, ...
1 and 2 respectively.
It is possible to obtain the branching / focusing element S in which the grooves M and m of the Fresnel cylindrical lenses 2 and 3 as shown in FIG.

Since this embodiment has the above-mentioned structure, in FIGS. 3 and 4, the infrared light generated from the light source 4 passes through the analysis cell 1 and is absorbed by the characteristic according to the type and concentration of the gas to be measured. After receiving the light, the optical chopper 5 and the optical filter 6
Through each of the multi-element type pyroelectric detectors 7.

Two-part Fresnel cylindrical lenses 2 and 3 are arranged between the analysis cell 1 and the optical filter 6 in order to efficiently collect light on each light receiving portion. The two-divided Fresnel cylindrical lenses 2 and 3 each have a function of converging in two linear shapes, and these lenses 2 and 3 are 90
By arranging them on the optical axis of infrared light in a rotated form, a branching / focusing element S having four focal points can be obtained.
Therefore, the parallel light component of the infrared light from the analysis cell 1 can be uniformly branched and condensed without being biased to a specific light receiving electrode formed in the multi-element type pyroelectric detector 7, and crosstalk between the light receiving electrodes can be easily performed. It can be reduced with a simple structure.

In FIG. 4, the optical filter 6 and the pyroelectric element of the multi-element type pyroelectric detector 7 are fixed on a supporting substrate 24 placed on the metal stem 21, and these are arranged in a detector window. It is sealed with a metal cap 23 having a material 22.

As described above, in this embodiment, the groove of the Fresnel lens is formed by processing the Si flat substrate by etching, but since anisotropic etching, which is advantageous for this type of processing, is used, the processing accuracy is disadvantageous. The aspect ratio can be made higher than that of the conventional concentric groove processing using isotropic etching, and the groove processed shape can be improved.

FIG. 19 shows a branch / collection of the second embodiment of the present invention in which a Fresnel cylindrical lens divided into two and a Fresnel cylindrical lens divided into two are formed on both surfaces of one rectangular flat surface portion 20a, respectively. The optical element S is shown. The manufacturing method will be described below with reference to FIGS. First, the n-type Si substrate 10 as shown in FIG. 16 is subjected to double-sided patterning along the crystal axis using the (100) plane (see FIG. 17). At this time, selective exposure of both surfaces is performed using a known photomask 11 designed to have a desired groove pitch. Then, the unexposed portions on both sides are removed to leave the groove forming pattern 12 on both sides (see FIG. 18). Next, the grooves M and m are processed by using anisotropic etching. As a result, the sparse portions 4, 5 and the dense portions 6, 7, which have a desired groove pitch with good processing accuracy,
8 can be formed (see FIG. 19).

As described above, the photomasks 11 are arranged on both surfaces of the Si substrate 10 so that the grooves M and m are orthogonal to each other, and anisotropic etching is performed after the selective exposure. Has the same effect as. At this time, if the double-sided mask aligner is used, the Si substrate processing steps can be completed at one time, and the positioning error of the grooves M, m can be reduced as compared with the step of separately processing the both surfaces.

[0028]

As described above, according to the present invention, the P-divided Fresnel cylindrical lens and the Q-divided Fresnel cylindrical lens are arranged such that the grooves of the rectangular plane portions thereof are orthogonal to each other.
The parallel light component of infrared light from the analysis cell, which has received characteristic absorption according to the type and concentration of the gas to be measured in the analysis cell, is uniform without being biased by the specific light receiving electrode formed on the multi-element pyroelectric detector. There is an effect that the light can be branched and condensed into two and the crosstalk between the light receiving electrodes can be reduced with a simple structure. Since the Fresnel groove is processed by anisotropic etching, for example, when patterning along the crystal axis using the (1 0 0) plane of the Si substrate, the (1 1 1) plane serves as an etch stop. , It is easier to obtain the processing accuracy of each groove than using isotropic etching. Further, since the Fresnel lens is used, there is an advantage that a compact and short-focusing branching / focusing element can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a configuration in the above embodiment.

FIG. 3 is an explanatory diagram of the overall configuration of the above embodiment.

FIG. 4 is an explanatory diagram of a main part configuration in the embodiment.

FIG. 5 is an explanatory diagram of a partial configuration in the above embodiment.

FIG. 6 is an explanatory diagram of a partial configuration of the above embodiment.

FIG. 7 is an explanatory diagram of a main part configuration in the embodiment.

FIG. 8 is an explanatory diagram for explaining the principle of the above embodiment.

FIG. 9 is an explanatory diagram for explaining the principle of the above embodiment.

FIG. 10 is an explanatory diagram for explaining the principle of the above embodiment.

FIG. 11 is a diagram showing a first step of a manufacturing process in the above-mentioned embodiment.

FIG. 12 is a diagram showing a second step of the manufacturing process.

FIG. 13 is a diagram showing a third step of the manufacturing process.

FIG. 14 is a diagram showing a fourth step of the manufacturing process.

FIG. 15 is a diagram showing a fifth step of the manufacturing process.

FIG. 16 is a diagram showing a first step of a manufacturing process in the second embodiment of the present invention.

FIG. 17 is a diagram showing a second step of the manufacturing process in the second embodiment.

FIG. 18 is a diagram illustrative of the same as the third step of the manufacturing process in the second embodiment.

FIG. 19 is also a diagram showing a fourth step of the manufacturing process in the second embodiment.

[Explanation of symbols]

1 ... Analysis cell, 2, 3 ... Pair of Fresnel lens, 2a,
3a ... Rectangular plane portion, 7 ... Multi-element type pyroelectric detector, M, m ...
groove.

Claims (2)

[Claims] 1. A parallel light component of infrared light from the analysis cell, which has received characteristic absorption in accordance with the type and concentration of the gas to be measured in the analysis cell, is branched to separate each of the multi-element pyroelectric detectors. In the branching / focusing element for focusing on the light receiving section, the parallel light component of the infrared light which is composed of a pair of Fresnel lenses, one of the pair of Fresnel lenses having passed through the rectangular plane portion having the groove is P ( P is a natural number and is composed of Fresnel cylindrical lenses divided into P so as to form focal positions, and the parallel light component of infrared light that has passed through the rectangular plane portion having the groove on the other side is Q (Q is P Is a multi-element type in which each Fresnel lens is arranged so that the grooves of the rectangular plane portions are orthogonal to each other. Pyroelectric detector Branching / condensing element. 2. A pair of Fresnel lenses are respectively formed on two rectangular flat portions, a P-divided Fresnel cylindrical lens is formed on the first rectangular flat portion, and a second rectangular flat portion is formed. The multi-element pyroelectric detector branching / focusing device according to claim 1, wherein a Q-divided Fresnel cylindrical lens is formed, and further, these two Fresnel cylindrical lenses are bonded so that grooves are orthogonal to each other. element.