JP2008304384A - Infrared detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an infrared light detector capable of reducing the manufacturing cost and reducing the size and the freedom in designing the detection range.
A prism 4 that refracts infrared light from a plurality of detection ranges so as to be incident on an infrared light detection unit 1 through a condenser lens 3 is provided. The prism 4 has three types of refracting surfaces 41a to 41c having different directions corresponding to one of the three detection ranges. Compared with the case where the condensing lens 3 is provided for each detection range, the manufacturing cost can be reduced and the size can be reduced, and the degree of freedom in designing the detection range is higher than when a diffraction grating is used.
[Selection] Figure 1

Description

  The present invention relates to an infrared light detector.

  Conventionally, an infrared light detection unit that outputs an electrical signal corresponding to the amount of incident infrared light and a condenser lens that collects infrared light from a predetermined detection range on the infrared light detection unit are provided. Infrared light detectors are provided, and are used for lighting control, automatic door opening / closing control, security devices, etc., mainly for human detection. In this type of infrared light detector, a plurality of detection ranges may be provided (for example, see Patent Document 1).

  Here, as a method of providing a plurality of detection ranges, for example, a condensing lens may be provided for each detection range, and infrared light from different detection ranges may be condensed on the infrared light detection unit by different condensing lenses. It is done. However, if a plurality of condensing lenses are provided, the number of parts increases and the manufacturing cost increases.

  Therefore, it is conceivable to integrally form a plurality of condensing lenses, but this is difficult to realize except for a synthetic resin molded product. However, the synthetic resin has a low refractive index. For example, in the case of polyethylene, the refractive index is 1.53. Therefore, when the condenser lens is formed of a synthetic resin as described above, the condenser lens becomes large and the amount of attenuation of infrared light in the condenser lens also increases.

Therefore, as shown in FIG. 16, a diffraction grating 5 is arranged in front of the condenser lens 3 in the optical system, and infrared light from each detection range is detected by the diffraction grating 5 through the condenser lens 3. It has been proposed to diffract the light so as to enter the portion 1 (see, for example, Patent Document 2).
JP 11-248540 A JP-A-10-214546

  However, when the diffraction grating 5 is used, the detection range that can actually be used is the direction orthogonal to the diffraction grating 5, that is, the direction in which the 0th-order diffracted light in the diffraction grating 5 is incident on the condenser lens (upward in FIG. 16). ) And the two directions (upper left and upper right in FIG. 16) in which the first-order diffracted light in the diffraction grating 5 is incident on the condenser lens, respectively. In other words, the direction is limited to a total of three directions: a direction corresponding to the zeroth-order diffracted light and a two-direction corresponding to the first-order diffracted light, which are directions deviated from each other by the same angle. For example, when the detection ranges are provided in three directions on the same plane, the angles θ1 and θ2 formed by the directions of the detection ranges at both ends cannot be made different from the directions of the center detection range. The degree of freedom in designing the detection range was low.

  The present invention has been made in view of the above-mentioned reasons, and an object thereof is to provide an infrared light detector capable of reducing the manufacturing cost and reducing the size and the design freedom of the detection range. It is in.

  The invention of claim 1 is an infrared light detector for detecting infrared light from a plurality of detection ranges, respectively, and an infrared light detector for outputting an electrical signal corresponding to the amount of incident infrared light And a housing having a window part for allowing infrared light to enter and housing the infrared light detection part, and collecting infrared light held in the housing and incident from the window part of the housing on the infrared light detection part And a prism held in the housing so as to close the window. Each prism has a plurality of types of refracting surfaces, each of which has a different orientation and corresponds to one of the detection ranges. When the infrared light from the light enters or exits from the refracting surface corresponding to the detection range, the infrared light enters the infrared light detection unit through the condenser lens.

  According to this invention, compared with the case where a condensing lens is provided for every detection range, manufacturing cost can be reduced and the size can be reduced. In addition, the degree of freedom in designing the detection range is higher than in the case where a diffraction grating is used to cause infrared light from each detection range to enter the condenser lens.

  The invention of claim 2 is characterized in that, in the invention of claim 1, the prism is made of polyethylene.

  According to this invention, the manufacturing cost is reduced as compared with the case of using glass or silicon as the material of the prism.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, a plurality of refractive surfaces are provided for each detection range.

  According to the present invention, the prism size is increased in the optical axis direction of the condensing lens in order to secure the solid angle of the refracting surface with respect to the condensing lens, compared to the case where one refracting surface is provided for each detection range. Since there is no need, the attenuation of infrared light in the prism can be reduced and the size can be reduced.

  According to a fourth aspect of the present invention, in any of the first to third aspects of the present invention, the refracting surface is an exit surface from which infrared light is emitted by being directed toward the condensing lens side. The incident surface on which the infrared light from the detection range that is directed is incident is a flat surface.

  According to the present invention, the appearance is improved as compared with the case where irregularities are formed using the incident surface as the refractive surface. Further, even when dirt is attached to the incident surface, the removal is easy.

  According to a fifth aspect of the present invention, in the first or second aspect of the present invention, the refracting surface is an incident surface that is directed to the opposite side of the condensing lens and receives infrared light from the detection range. .

  According to the present invention, the detection range can also be configured in a direction orthogonal to the optical axis of the condenser lens.

  A sixth aspect of the invention is characterized in that, in any of the first to fifth aspects of the invention, the refractive surface includes a surface substantially perpendicular to the optical axis of the condenser lens.

  According to the present invention, the detection range is also configured in the direction along the optical axis of the condenser lens.

  The invention of claim 7 is the invention according to any one of claims 1 to 6, wherein the infrared light detection unit includes a plurality of light receiving units on which infrared light from different positions in the detection range is incident, and is adjacent to each other. The direction of the output of the infrared light detection unit differs depending on which of the light receiving units to which the infrared light is incident.

  According to this invention, when an infrared source such as a human body moves from a position corresponding to a certain light receiving unit to a position corresponding to another light receiving unit adjacent to the light receiving unit within the detection range, the infrared light detecting unit Therefore, the movement of the infrared light source within the detection range can be detected based on the output of the infrared light detection unit.

  The invention of claim 8 is the invention of claim 7, wherein each refracting surface is parallel to one imaginary straight line orthogonal to the optical axis of the condensing lens, and the light receiving part is the imaginary straight line and the condensing lens. It is characterized by being arranged in a straight line in the direction intersecting with the optical axis.

  The invention of claim 9 is the invention of claim 7, wherein each refracting surface is parallel to one imaginary straight line orthogonal to the optical axis of the condensing lens, and the light receiving part is in a direction parallel to the imaginary straight line. It is characterized by being arranged in a straight line.

  According to a tenth aspect of the present invention, in the invention according to any one of the first to ninth aspects, the prism is provided with a light-shielding portion having a lower infrared light transmittance than other portions.

  Providing a light-shielding portion at a portion of the prism where infrared light is not intended to pass can suppress malfunctions in which infrared light from outside the detection range is detected.

  The invention of claim 11 is characterized in that, in the invention of claim 10, a part of the surface of the prism is roughened as a light shielding portion.

  According to a twelfth aspect of the present invention, in the invention of the tenth aspect, the prism is provided with a light-shielding layer as a light-shielding portion made of a material having a higher absorptance for infrared light than other parts of the prism. And

  The invention of claim 13 is the invention according to any one of claims 1 to 12, wherein the condenser lens is a convex lens made of a semiconductor and corresponds to the optical axis of the condenser lens on one surface of a flat semiconductor wafer. A step of forming an electrode having a circular opening centered on the position to be formed, a step of forming a porous portion on the other surface side of the semiconductor wafer by an anodic oxidation method using the electrode, and removing the porous portion It is manufactured by the manufacturing method provided with the process to perform.

  The invention of claim 14 is the invention according to any one of claims 1 to 13, wherein the prism is made of a material having lower thermal conductivity than the housing, and has a cylindrical shape surrounding the housing when viewed from the optical axis direction of the condenser lens. It has an enclosing portion and a main body portion provided with a refracting surface and closing one end of the enclosing portion.

  According to this invention, the change in the temperature of the light receiving element accompanying the change in the ambient temperature can be suppressed by the prism.

  According to the first aspect of the present invention, infrared light from a plurality of detection ranges is incident on a common condensing lens by a prism, so that the manufacturing cost is reduced as compared with the case where a condensing lens is provided for each detection range. And miniaturization is possible. In addition, the degree of freedom in designing the detection range is higher than in the case where a diffraction grating is used to cause infrared light from each detection range to enter the condenser lens.

  According to the invention of claim 2, since the prism is made of polyethylene, the manufacturing cost is reduced as compared with the case of using glass or silicon as the material of the prism.

  According to the invention of claim 3, since a plurality of refracting surfaces are provided for each detection range, the solid angle of the refracting surface with respect to the condensing lens as compared with the case where one refracting surface is provided for each detection range. Since it is not necessary to increase the size of the prism in the direction of the optical axis of the condenser lens in order to ensure the above, it is possible to reduce the attenuation of infrared light and reduce the size of the prism.

  According to the invention of claim 4, since the exit surface is a refracting surface and the incident surface is a flat surface in the prism, the appearance is improved as compared with the case where the projection surface is formed with the incident surface serving as the outer surface as the refracting surface. The Further, when dirt is attached to the incident surface of the prism, the removal is easy.

  According to the fifth aspect of the present invention, since the refracting surface is the incident surface, the detection range can be configured in the direction orthogonal to the optical axis of the condenser lens.

  According to the sixth aspect of the present invention, the detection range is configured in the optical axis direction of the condensing lens by including a surface substantially perpendicular to the optical axis of the condensing lens in the refracting surface.

  According to the invention of claim 7, when an infrared source such as a human body moves from a position corresponding to a certain light receiving unit to a position corresponding to another light receiving unit adjacent to the light receiving unit within the detection range, Since the direction of the output of the light detection unit changes, it is possible to detect the movement of the infrared light source within the detection range based on the output of the infrared light detection unit.

  According to the tenth aspect of the present invention, by providing a light-shielding portion at a portion of the prism where infrared light is not intended to pass, it is possible to suppress malfunctions in which infrared light from outside the detection range is detected. be able to.

  According to invention of Claim 14, the change of the temperature of the light receiving element accompanying the change of ambient temperature can be suppressed by a prism.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  In the present embodiment, as shown in FIG. 2, an infrared light detection unit 1 including a light receiving element that outputs an electrical signal corresponding to the amount of incident infrared light, and a window unit 20 for allowing infrared light to enter. And a condensing lens 3 that condenses the infrared light that is held in the housing 2 and is incident from the window 20 of the housing 2 on the infrared light detection unit 1. Is provided. As the light receiving element used in the infrared light detection unit 1, for example, a thermopile, a bolometer, or a pyroelectric element can be used. Hereinafter, the vertical direction in FIG. 2 is referred to as the front-rear direction, the horizontal direction is referred to as FIG. 2, and the direction orthogonal to the paper surface of FIG.

  The housing 2 is made of metal and has a flat stem 21 with a flat front and rear, and a bottomed cylindrical shape made of metal with an open rear surface. A window portion 20 is provided through the bottom surface (front surface), and the stem 21 closes the rear surface. And a cap 22 mechanically coupled to the stem 21 by, for example, an adhesive. The condensing lens 3 is a convex lens having a spherical surface on one side, and the spherical surface is directed forward, the optical axis direction is the front-rear direction, and the window portion 20 is closed. It is fixed to the cap 22. The stem 21 is made of, for example, a conductive material such as metal, and a plurality of terminals 23 for drawing out the output of the infrared light detection unit 1 are held in a form penetrating in the front-rear direction. An insulating layer (not shown) such as a synthetic resin is provided between the inner surface of the through hole through which the terminal 23 is inserted in the stem 21 and each terminal 23. Further, the housing 2 is a processing circuit (not shown) that is interposed between the infrared light detection unit 1 and the terminal 23 and performs predetermined signal processing such as amplification and noise removal on the output of the infrared light detection unit 1. Is stored.

  Furthermore, the present embodiment includes a prism 4 made of polyethylene and refracting infrared light from three detection ranges so as to be incident on the infrared light detection unit 1 through the condenser lens 3. The prism 4 is made of polyethylene, and has a main body portion 41 that is flat on the front and rear sides of the housing 2 and a cylindrical shape that protrudes rearward from the peripheral edge of the main body portion 41. The cap 22 of the housing 2 is viewed from the front. And a surrounding portion 42 fixed to the housing 2 with an adhesive, for example. Here, although the output of the infrared light detection unit 1 is generally affected by temperature, in the present embodiment, the prism 4 surrounding the housing 2 serves as a heat insulating material, so that the infrared light accompanying fluctuations in ambient temperature. Variations in the temperature of the light detection unit 1 are suppressed. As the material of the prism 4, silicon or germanium can be used as long as it is a transparent material. However, it is desirable to use a synthetic resin from the viewpoint of ease of manufacture and the above-described heat insulation effect. It is desirable to use polyethylene having a relatively high transmittance.

  Hereinafter, the configuration in which the prism 4 refracts infrared light will be described in detail. The front surface of the main body 41 of the prism 4 is a plane orthogonal to the front-rear direction, which is the optical axis direction of the condenser lens 1, and the rear surface of the main body 41 is parallel to the vertical direction and corresponds to different detection ranges. It is comprised by the refracting surfaces 41a-41c which are the planes of three directions to do. As shown in FIG. 1, the refracting surfaces 41 a to 41 c are configured to emit infrared light that is substantially parallel to the front surface of the main body 41 and is incident on the infrared light detection unit 1 from the front detection range. 1 refracting surface 41a, a second refracting surface 41b that emits infrared light from a detection range obliquely left frontward (left obliquely upward in FIG. 1) in an incident direction to the infrared light detection unit 1, and right obliquely A third refracting surface 41c that emits infrared light from a detection range in front (diagonally upward to the right in FIG. 1) in a direction to enter the infrared light detection unit 1 is configured. Here, in the present embodiment, the first refracting surface 41a is adjacent to the left side of the first refracting surface 41a and the third refracting surface 41c is adjacent to the right side of the first refracting surface 41a. The refracting surface 41a is positioned behind the second refracting surface 41b and the third refracting surface 41c, but the arrangement of the second refracting surface 41b and the third refracting surface 41c is reversed. Thus, the first refracting surface 41a may be positioned in front of the second refracting surface 41b and the third refracting surface 41c. However, the arrangement of the present embodiment has an advantage that infrared light from the left and right detection ranges is likely to enter the second refracting surface 41b and the third refracting surface 41c.

  A plurality of each of the refractive surfaces 41a to 41c are provided in the order of the second refractive surface 41b, the first refractive surface 41a, and the third refractive surface 41c in this order from the left. Thereby, compared with the case where only one refracting surface 41a to 41c is provided, the front and rear dimensions of the main body 41 of the prism 4 are reduced while ensuring the solid angle of the refracting surfaces 41a to 41c with respect to the condenser lens 3. In addition, the overall size of the infrared light detector can be reduced, and the attenuation of infrared light in the prism 4 can be reduced. Here, the width dimension of each refracting surface 41a to 41c in the cross section parallel to the direction in which the detection ranges are arranged is the number of wavelengths (about 10 μm) of infrared light to be detected so that the contribution of diffraction does not increase. It is necessary to make it more than double.

  According to the above configuration, the manufacturing cost can be reduced as compared with the case where a condensing lens is provided for each detection range in order to provide a plurality of detection ranges. Further, since the angle formed by the directions of the detection ranges can be arbitrarily changed by appropriately changing the directions of the refracting surfaces 41a to 41c, the infrared light from each detection range can be changed as in the conventional example of FIG. As compared with the case where the diffraction grating 5 is used to make each of the light incident on the condenser lens 3, the degree of freedom in designing the detection range is high.

  Furthermore, the surface on which the irregularities are formed by the refracting surfaces 41 a to 41 c is the rear surface of the prism 4, and the front surface of the prism 4 is a flat surface. In addition, it is easy to remove dirt adhering to the front surface of the prism 4.

  Instead of arranging each refracting surface 41a to 41c in a straight line as a flat surface, for example, a truncated pyramid-shaped recess whose inner peripheral surface and bottom surface are refracting surfaces is formed on the rear surface of the main body 41 of the prism 4 as a lattice. In this case, the detection ranges are also formed on both the upper and lower sides of the central detection range. However, as in the present embodiment, planar refracting surfaces 41a to 41c that are parallel to a common straight line (straight line parallel to the vertical direction) are arranged in a straight line in a direction perpendicular to the straight line (left and right direction). With the structure, there is an advantage that manufacture and polishing of a mold for molding can be easily performed by linear operations in the vertical direction along the straight lines.

  Further, instead of using three detection ranges as described above, only two detection ranges and refractive surfaces 41a may be provided as shown in FIG. In the example of FIG. 3, the refraction corresponding to the detection range on the right diagonal front is between the left end of the refraction surface 41 a corresponding to the detection range on the front and the right end of the refraction surface 41 b corresponding to the detection range on the left front. Instead of the surface 41c, a connecting surface 41d substantially perpendicular to the front surface of the prism 4 is provided, and the detection range is only forward and diagonally left front. When the prism 4 is manufactured by molding a synthetic resin, it is difficult to make the connecting surface 41d completely perpendicular to the front surface of the prism 4, and therefore the angle formed by the connecting surface 41d and the front surface of the prism 4 is 80 °. It will be about. Furthermore, in order to suppress malfunction caused by infrared light being emitted from the connecting surface 41d, which is a portion where infrared light is not intended to pass, the connecting surface 41d has a refractive index 41a that transmits infrared light. , 41b, etc. It is desirable to provide a light-shielding part (not shown) that is lower than other parts. As a method for providing the light shielding portion, a method of roughening the connection surface 41d by roughening a corresponding portion in the molding die for prism 4 or polishing the prism 4 after molding, A method of providing a light-shielding layer made of a material having a relatively high infrared light absorption rate such as an acrylic resin by double molding or coating is conceivable.

  As a method of setting two detection ranges, the first refracting surface 41a is omitted, and the rear surface of the main body portion 41 of the prism 4 is formed into a triangular triangular cross section by the second refracting surface 41b and the third refracting surface 41c. There is also a method. On the other hand, if refracting surfaces having different directions are added as appropriate, the detection range can be increased to four or more.

  Alternatively, as shown in FIG. 4, the infrared light detection unit 1 is arranged in the left-right direction, which is the direction in which the refracting surfaces 41 a to 41 c are arranged, and receives three light beams that receive infrared light from different parts of the detection ranges. You may comprise with the light receiving elements 1a-1c as a part. That is, in each detection range, from the left, the range in which infrared light is detected by the right light receiving element 1a, the range in which infrared light is detected by the center light receiving element 1b, and the infrared light by the left light receiving element 1b. The range in which is detected is arranged in order. In FIG. 4, only one refracting surface 41 a to 41 c is drawn for simplicity, and the positional relationship between the refracting surfaces 41 a to 41 c is also different from that in FIG. 1. If the said structure is employ | adopted, operation | movement of infrared light sources, such as a human body, within a detection range can be detected by monitoring the output of each light receiving element 1a-1c separately.

  Further, as shown in FIGS. 5, 9, and 12, the infrared light detection unit 1 is configured so that the output directions when the infrared light is incident between the adjacent light receiving elements 1 p and 1 m are opposite to each other. A plurality of light receiving elements 1p and 1m may be connected in series.

  In the example of FIG. 5, four light receiving elements 1p and 1m each having a square light receiving surface are arranged in two rows and two columns, and the direction in which the light receiving elements 1p and 1m are arranged is the direction in which the refractive surfaces 41a to 41c are arranged. It is inclined 45 ° with respect to it. Further, the two upper and lower light receiving elements 1p are connected so that the direction of the output when infrared light is incident is positive, and the two left and right light receiving elements 1m are respectively connected when infrared light is incident. It is connected so that the output direction of is negative. Accordingly, as shown in FIG. 6, in each of the detection ranges Za to Zc, each corresponds to a range Zp corresponding to the light receiving element 1p in which the output direction is positive and a light receiving element 1m in which the output direction is negative. The range Zm is mixed. Accordingly, as shown by an arrow A1 in FIG. 6, when a person M as an infrared light source crosses the three detection ranges Za to Zc from the left to the right, as shown in FIG. 7, one detection range Za The output of the infrared light detection unit 1 fluctuates even during movement within ~ Zc. Instead of selecting the angles formed by the refracting surfaces 41a to 41c so that the detection ranges Za to Zc do not overlap as shown in FIG. 5, in the detection ranges Za to Zc adjacent to each other as shown in FIG. By setting the ranges Zm corresponding to the left and right light receiving elements 1m to overlap each other, the interval in which the output of the infrared light detection unit 1 remains negative between the adjacent detection ranges Za to Zc is shortened. Also good.

  In the example of FIG. 9, a plurality (four in the figure) of light receiving elements 1p and 1m each having a rectangular light receiving surface that is vertically long are arranged in the left-right direction, which is the direction in which the refracting surfaces 41a to 41c are arranged. ing. Further, the orientations of the refracting surfaces 41a to 41c are selected so that the three detection ranges Za to Zc are adjacent to each other. In this configuration, as shown in FIG. 10, the range Zp corresponding to the light receiving element 1 p whose output direction is positive and the range Zm corresponding to the light receiving element 1 m whose output direction is negative alternately Lined up. Therefore, as shown by the arrow A2 in FIG. 10, when the person M as the infrared light source crosses the three detection ranges Za to Zc from the left to the right, the infrared light detection unit 1 as shown in FIG. Output fluctuates finely. In the above example, since the direction in which the light receiving elements 1p and 1m are aligned and the direction in which the detection ranges Za to Zc are aligned with each other, the section in which the operation of the person M is detected can be long. If the number of the light receiving elements 1p and 1m is not four but an even number, the range Zp corresponding to the light receiving element 1p in which the direction of the output is positive without providing an overlap between the detection ranges Za to Zc, and the output The range Zm corresponding to the light receiving element 1m having a negative direction can be arranged alternately.

  In the example of FIG. 12, a plurality (two in the figure) of light receiving elements 1p and 1m each having a long rectangular light receiving surface on the left and right are vertically aligned in a direction orthogonal to the direction in which the refracting surfaces 41a to 41c are arranged. They are arranged side by side. This configuration is a direction perpendicular to the direction in which the light receiving elements 1p and 1m are arranged, that is, the direction in which the detection ranges Za to Zc are arranged as shown by an arrow A3 in FIG. 13 (the vertical direction in the above description, the horizontal direction in FIG. ) Is suitable for detecting a human body M that crosses the detection range Za to Zc. That is, compared with the case of FIG. 9, since the area where the movement of the person M is detected becomes shorter instead of being wide, it can be used for detection of the passage of the person M in a wide passage, for example, for a crime prevention use. .

  Further, instead of providing the refracting surfaces 41a to 41c on the rear surface as described above to serve as the infrared light exit surface, as shown in FIG. 14, refracting surfaces 41e to 41g are provided on the front surface to serve as the infrared light incident surface. Also good. In the example of FIG. 14, the left refracting surface 41 e that causes infrared light from the left to enter the infrared light detection unit 1, and the right refracting surface that causes infrared light from the right to enter the infrared light detection unit 1. 41f are provided one by one. The left refracting surface 41e and the right refracting surface 41f constitute a convex portion having a triangular cross section on the front surface of the main body portion 41 of the prism 4, and the left and right sides of the convex portion are respectively perpendicular to the front-rear direction. Thus, a front refracting surface 41g for allowing the infrared light from the front to enter the infrared light detection unit 1 is formed. If this configuration is adopted, the left refracting surface 41e and the right refracting surface 41f project infrared light from the left and right directions substantially orthogonal to the optical axis of the condensing lens 3 forward from the other portions of the prism 4. The light can be refracted and reflected to enter the infrared light detection unit 1. For example, in the case where the prism 4 is made of polyethylene having a refractive index of 1.53, in order to emit infrared light incident from the left and right directions backward, the front refractive surface is provided for each of the left refractive surface 41e and the right refractive surface 41f. The angle formed with the plane including 41 g may be 52.1 °.

  Hereinafter, with reference to FIGS. 15A to 15E, an example of a method for manufacturing the condenser lens 3 from the semiconductor wafer 30 made of p-type silicon is shown in FIGS. 15A to 15E in the vertical direction. This will be explained as a standard. Actually, a plurality of condensing lenses 3 are formed from one semiconductor wafer 30, but only the range corresponding to one condensing lens 3 is shown in FIGS. 15 (a) to 15 (e). Yes.

  First, a metal film 31 made of, for example, aluminum is formed on the lower surface of the semiconductor wafer 30 shown in FIG. 15A by a known method such as sputtering or vapor deposition, as shown in FIG. 15B. Thereafter, heat treatment of the metal film 31 is performed, for example, in a nitrogen gas and hydrogen gas atmosphere so that the contact between the metal film 31 and the semiconductor wafer 30 is ohmic contact.

  Next, as shown in FIG. 15C, an electrode 32 is formed by providing a circular opening 33 in the metal film 31 centering on the position to be the optical axis of the condenser lens 3. Well-known photolithography and etching can be used to form the opening 33.

  Next, anodic oxidation using the electrode 32 as an anode is performed. That is, when an electric current is passed between the electrode 32 as the anode and a cathode (not shown) disposed on the upper surface side of the semiconductor wafer 30 in the electrolytic solution, as shown in FIG. A porous portion 34 is formed on the upper surface side of the semiconductor wafer 30. As the electrolytic solution, for example, a 1: 1 mixed solution of 55 wt% aqueous hydrogen fluoride and ethanol can be used. Here, the vertical dimension (thickness dimension) of the porous portion 34 is the smallest at the position farthest from the electrode 32, that is, the upper side of the center of the opening 33, and increases as the distance from the center increases. That is, if the porous portion 34 is removed as shown in FIG. 15E, the upper surface of the semiconductor wafer 30 becomes a convex curved surface (spherical surface), and the optical axis direction of this convex curved surface shape is the vertical direction. .

  After the porous portion 34 is removed, the condensing lens 3 can be obtained by separating a predetermined range around the apex of the convex curved surface (the upper side of the opening 33) by dicing. The remaining electrode 32 can be used to block infrared light that has passed through a portion of the condenser lens 3 that is not spherical.

  As a material for the semiconductor wafer 30, other semiconductor materials such as germanium can be used instead of silicon. Further, an n-type semiconductor wafer 30 may be used instead of the p-type. In this case, it is necessary to irradiate light on the upper surface of the semiconductor wafer 30 during anodization.

It is explanatory drawing which shows the main optical paths in embodiment of this invention. It is sectional drawing which shows the same as the above. It is explanatory drawing which shows the main optical paths in another form same as the above. It is explanatory drawing which shows the main optical paths in another form same as the above. It is explanatory drawing which shows the structure of the principal part of another form same as the above. It is explanatory drawing which shows the operation | movement of the form of FIG. It is explanatory drawing which shows the operation | movement of the form of FIG. It is explanatory drawing which shows operation | movement of another form same as the above. It is explanatory drawing which shows the structure of the principal part of another form same as the above. It is explanatory drawing which shows the operation | movement of the form of FIG. It is explanatory drawing which shows the operation | movement of the form of FIG. It is explanatory drawing which shows the structure of the principal part of another form same as the above. It is explanatory drawing which shows the operation | movement of the form of FIG. It is explanatory drawing which shows the main optical paths in another form same as the above. The example of the manufacturing method of a condensing lens is shown, (a)-(e) is sectional drawing which shows a different process, respectively. It is explanatory drawing which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Infrared light detection part 1a-1c, 1p, 1m Photosensitive element 2 Housing 3 Condensing lens 4 Prism 20 Window part 41 Main-body part 41a-41c, 41e-41g Refractive surface 42 Enclosing part

Claims (14)

An infrared light detector for detecting infrared light from a plurality of detection ranges,
An infrared light detection unit that outputs an electrical signal corresponding to the amount of incident infrared light, a housing that has a window for allowing infrared light to enter, and that contains the infrared light detection unit, and is held by the housing A condensing lens for condensing infrared light incident from the window portion of the housing on the infrared light detection portion, and a prism held in the housing so as to close the window portion,
Each prism has a plurality of types of refracting surfaces that have different orientations and correspond to one of the detection ranges, and infrared light from each detection range is incident or emitted from a refracting surface corresponding to the detection range, respectively. And an infrared light detector that is incident on the infrared light detector through a condenser lens.   The infrared light detector according to claim 1, wherein the prism is made of polyethylene.   3. The infrared light detector according to claim 1, wherein a plurality of refractive surfaces are provided for each detection range.   The refracting surface is the exit surface that emits infrared light that is directed toward the condenser lens, and the incident surface that is directed toward the opposite side of the condenser lens and receives infrared light from the detection range in the prism is flat. The infrared light detector according to claim 1, wherein the infrared light detector is provided.   3. The infrared light detector according to claim 1, wherein the refracting surface is an incident surface that is directed to the opposite side of the condenser lens and receives infrared light from the detection range.   The infrared light detector according to claim 1, wherein the refractive surface includes a surface substantially perpendicular to the optical axis of the condenser lens. The infrared light detection unit includes a plurality of light receiving units on which infrared light from different positions in the detection range is incident,
The infrared light according to any one of claims 1 to 6, wherein the direction of the output of the infrared light detection unit is different depending on which of the light receiving units adjacent to each other is incident with the infrared light. Detector. Each refractive surface is parallel to one imaginary straight line orthogonal to the optical axis of the condenser lens,
8. The infrared light detector according to claim 7, wherein the light receiving portions are arranged in a straight line in a direction intersecting with the virtual straight line and the optical axis of the condenser lens. Each refractive surface is parallel to one imaginary straight line orthogonal to the optical axis of the condenser lens,
8. The infrared light detector according to claim 7, wherein the light receiving portions are arranged in a straight line in a direction parallel to the virtual straight line.   The infrared light detector according to any one of claims 1 to 9, wherein the prism is provided with a light shielding portion having a transmittance of infrared light lower than that of other portions.   The infrared light detector according to claim 10, wherein a part of the surface of the prism is roughened as a light shielding portion.   The infrared light detector according to claim 10, wherein the prism is provided with a light-shielding layer as a light-shielding portion made of a material having a higher absorption factor for infrared light than other parts of the prism. The condenser lens is a convex lens made of a semiconductor,
A step of forming an electrode having a circular opening centered on a position corresponding to the optical axis of the condensing lens on one surface of a flat semiconductor wafer; and the other of the semiconductor wafer by an anodic oxidation method using the electrode It is manufactured by the manufacturing method provided with the process of forming a porous part in the surface side of this, and the process of removing a porous part, It is any one of Claims 1-12 characterized by the above-mentioned. Infrared light detector.   The prism is made of a material having a lower thermal conductivity than the housing, and includes a cylindrical enclosing portion that surrounds the housing when viewed from the optical axis direction of the condenser lens, and a main body portion that is provided with a refractive surface and closes one end of the enclosing portion. The infrared photodetector according to claim 1, wherein the infrared photodetector is provided.

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