JP2006064519A - Photodetector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photodetector capable of maintaining high reliability even when used over the long-term. <P>SOLUTION: This detector 1 as a photodetector for detecting the monitoring domain state is equipped with a casing 2; a light receiving window 3 provided on one side of the casing 2; and detection elements 4-6 arranged inside the light receiving window 3, for detecting light entering through the light receiving window 3. The light receiving window 3 is fixed inside the casing 2, and the outside surface of the casing 2 and the outside surface of the light receiving window 3 are adjusted to be approximately flush with each other. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photodetector, and more particularly, to a photodetector that takes in external light through a light receiving window provided on one side of a housing.

Conventionally, a flame detector for detecting a fire occurring in a monitoring area has been used. In this flame detector, the fire is detected by detecting light (infrared rays) emitted from the fire with a detection element. In such a flame detector, in order to prevent the detection of light emitted from a light source other than a fire and to give a false alarm, a CO ₂ resonance radiation band (resonant radiation from carbon dioxide gas) generated during flammable combustion. Infrared light in a specific wavelength band including a central wavelength band of 4.5 μm as the apex) is detected, and the relative detection level of this specific wavelength band and the detection level of other wavelength bands detected simultaneously The presence of a fire was judged based on the ratio. For example, in addition to the CO ₂ resonance radiation band, a method for detecting one other wavelength band is called a two-wavelength type, and a method for detecting the other two wavelength bands is called a three-wavelength type.

  FIG. 8 is a longitudinal sectional view in the vicinity of the detection element of such a conventional three-wavelength flame detector. As shown in FIG. 8, the conventional three-wavelength sensor 100 is configured by housing three detection elements 102 to 104 inside a housing 101. Here, an opening 105 is formed in the housing 101, and a light receiving window 106 is disposed inside the opening 105. The light receiving window 106 is formed in a substantially flat plate shape from a translucent member such as glass, and is sandwiched between the casing 101 and a fixed plate 108 fixed to the casing 101 with screws 107. Thus, it was fixed to the housing 101. In such a configuration, external light is incident on the inside of the housing 101 through the light receiving window 106 and further incident on the detection elements 102 to 104, whereby flame detection using the detection elements 102 to 104 is performed. It was. In addition, a rubber packing 109 is provided between the housing 101 and the light receiving window 106 in order to prevent foreign matter such as water and dust from entering the inside of the housing 101 from between them (for example, Patent Document 1 and Patent Document 2).

  Moreover, the structure which made the outer surface of such a housing | casing and the outer surface of the light-receiving window substantially flush with each other has been proposed. Specifically, an opening having a size that can substantially accommodate the light receiving window is provided in the housing, and a step portion for fixing the light receiving window is provided inside the opening. Then, the inner side surface of the light receiving window and the outer side surface of the stepped portion are fixed by adhesion in a state where the light receiving window is substantially accommodated in the opening (for example, see Patent Document 3).

Japanese Patent Laid-Open No. 9-184753 JP-A-9-293184 Design Registration No. 1212388

  However, in the conventional sensor 100 as shown in FIG. 8, the light receiving window 106 is simply formed in a flat plate shape and provided inside the housing 101. The outer surface of the light receiving window 106 is not flush with the outer surface, and a step 110 is formed between the outer surfaces. Accordingly, foreign matter such as water and dust accumulates on the step 110, and the outer surface of the light receiving window 106 is soiled due to the accumulation of foreign matter, and the wiping residue is left on the step 110 when the outer surface is wiped during cleaning. There is a possibility that it may adversely affect the light receiving state and appearance.

  Further, in the sensor in which the outer surface of the housing and the outer surface of the light receiving window are substantially flush with each other as described above, the inner surface of the light receiving window and the outer surface of the step portion are fixed by bonding. Therefore, when the sensor is installed outdoors where sunlight directly or indirectly hits, there is a possibility that deterioration of the adhesive, packing, etc. may proceed quickly. Could fall, and the sensor function could be impaired.

  The present invention has been made in view of the above points, and can reduce contamination on the outer surface of the light receiving window and can maintain high reliability even when used for a long period of time. The purpose is to provide.

  In order to solve the above-described problems and achieve the object, the photodetector according to claim 1 is disposed inside a housing, a light receiving window provided on one side of the housing, and the light receiving window. A detection element that detects light incident through the light receiving window, and the light receiving window is fixed to the inside of the housing, and an outer surface of the housing and an outer surface of the light receiving window are provided. These are characterized by being substantially flush with each other.

  Further, the photodetector according to claim 2 is the photodetector according to claim 1, wherein the housing has an opening for inserting the light receiving window, and the light receiving window is A base that is fixed to the casing inside the casing, and a wall that protrudes from the base toward the opening and is fitted into the opening, and reaches the outer surface of the casing. And a projecting portion having the above.

  According to a third aspect of the present invention, in the photodetector according to the second aspect, the base portion and the protruding portion are formed in a substantially flat plate shape, and the base portion and the protruding portion are bonded to each other. Thus, the light receiving window is configured.

  According to a fourth aspect of the present invention, in the photodetector according to the second aspect of the present invention, a second opening is formed in the base portion, and the protrusion is extended from the second opening. It arrange | positions so that it may reach to the said outer surface of the said housing | casing, It was comprised to the said base part in the connection surface with a said 2nd opening part, It is comprised.

  Moreover, the photodetector of Claim 5 is the photodetector as described in any one of Claims 1-4. Between these housing | casings and the said light-receiving windows, these housing | casings, a light-receiving window, A protective means for preventing foreign matter from entering the interior of the photodetector from between the two is provided.

  According to the photodetector of the present invention, the outer surface of the housing and the outer surface of the light receiving window are substantially flush with each other, so there is almost no step between the outer surfaces. Accordingly, dust and dirt are less likely to accumulate on the outer surfaces of these light receiving windows, and even if the outer surface of the light receiving window is wiped for cleaning, the remaining wiping is reduced. Dirt and the like can be effectively reduced, and high reliability can be maintained even during long-term use. Furthermore, since the light receiving window is fixed inside the housing, when the light detector is mounted with the light receiving window facing downward, the light receiving window is removed from the housing for some reason. In this case, the light receiving window can be prevented from falling, and the functionality of the photodetector can be maintained.

  According to the photodetector of the present invention, the light receiving window protrudes from the base portion toward the opening side from the base portion and is fitted into the opening portion, and reaches the outer surface of the housing. Since it has the protrusion part which has thickness, there exists an effect that a protrusion part can be inserted and inserted into an opening part and a flush structure can be comprised only by fixing a base to a housing | casing.

  Further, according to the photodetector according to the present invention, the light receiving window is formed in a substantially flat plate shape with the base portion and the protruding portion, and the light receiving window is configured by adhering the base portion and the protruding portion to each other. The base and the protrusion may be simply formed in a substantially flat plate shape, and even when a high-hardness member such as sapphire glass is used for the base and / or the protrusion, the light receiving window can be easily formed.

  Further, according to the photodetector of the present invention, the projecting portion is disposed so as to reach the outer surface of the housing from the second opening, and is fixed to the base at the connection surface with the second opening. Therefore, since the external light passes through only the protruding portion and does not pass through the base portion or the adhesive layer and enters the detection element, it is further ensured that the external light is absorbed or attenuated by a portion other than the protruding portion. The detection sensitivity can be maintained or improved.

  Further, according to the photodetector according to the present invention, since the protective means is provided between the housing and the light receiving window, the protective means prevents foreign matter from entering between the housing and the base. Therefore, there is an effect that the reliability of the photodetector can be more effectively performed over a long period of time.

  Embodiments of a photodetector according to the present invention will be described below in detail with reference to the accompanying drawings. First, [I] the basic concept of the present invention will be described, then [II] an embodiment of the present invention will be described, and [III] Finally, a modification to the embodiment of the present invention will be described.

[I] Basic concept of the present invention First, the basic concept of the present invention will be described. The present invention relates to a photodetector for detecting various states in a monitoring area. Here, although the specific monitoring area | region and monitoring objective of a photodetector are arbitrary, the following embodiment demonstrates the flame detector which is installed outdoors etc. and monitors the presence or absence of misfire or a fire. Although the flame detection principle of the flame detector is arbitrary, for example, a wavelength method for detecting the amount of light in a wavelength band including the CO ₂ resonance radiation band can be adopted.

  Under such a premise, the photodetector according to the present invention is characterized in that the outer surface of the housing and the outer surface of the light receiving window for receiving external light are substantially flush with each other. It is said. Accordingly, it is possible to prevent foreign matters from accumulating between these outer surfaces.

  Here, in order to achieve such a configuration, it may be necessary to process the shape of the light receiving window more complicatedly than in the past. However, when sapphire glass having high hardness is used as the material of the light receiving window, it is complicated. It is also possible that difficult processing is difficult. Therefore, in the present invention, one of the features is a structure for achieving the flushing of the outer surface of the housing and the outer surface of the light receiving window with simple processing.

[II] Embodiments of the Present Invention Next, embodiments of a sensor as a photodetector according to the present invention will be described. However, the present invention is not limited by these embodiments.

[Embodiment 1]
First, the first embodiment will be described. In the sensor according to the first embodiment, (1) the outer surface of the housing and the outer surface of the light receiving window are substantially flush with each other, and (2) the housing receives light. The light receiving window has a base portion fixed to the housing inside the housing, and projects from the base portion toward the opening side to be inserted into the opening portion. A protrusion having a thickness that reaches the outer surface of the housing, and (3) the base and the protrusion are each formed in a substantially flat plate shape, and the base and the protrusion are bonded to each other. And (4) protective means for preventing foreign matter from entering between the housing and the base and entering the sensor from between the housing and the base. The main feature is that it is provided.

(Outline of sensor)
First, an outline of the sensor according to the present embodiment will be described. FIG. 1 is a block diagram illustrating the configuration of a sensor in terms of functional concept. As shown in FIG. 1, the sensor 1 includes a housing 2, a light receiving window 3, detection elements 4 to 6, a storage unit 7, and a determination unit 8.

  Among these, the light receiving window 3 is provided on one side surface of the housing 2, is formed of a translucent member, and transmits light in the monitoring region to enter the inside of the housing 2. Although the specific content of this translucent member is arbitrary, it can comprise using sapphire glass with a low infrared absorptivity, for example.

The detection elements 4 to 6 are elements that detect the light amount of light in a specific wavelength band. For example, the detection element 4 is an element that detects the light amount of light in the CO ₂ resonance radiation band and the detection elements 5 and 6. A so-called three-wavelength sensor 1 can be configured as an element that detects the amount of light in a band different from the CO ₂ resonance radiation band. The specific configurations of the detection elements 4 to 6 are arbitrary, but as the detection elements 4 to 6, for example, a pyroelectric element that outputs a voltage according to a change in the amount of received light can be used. Moreover, in addition to the detection elements 4-6, you may provide the arbitrary means for selectively detecting only the light of a specific wavelength band, for example, an optical filter.

  In FIG. 1, a storage unit 7 is a storage unit that stores a threshold value used to determine whether or not there is a fire. Media can be used. The determination unit 8 determines the presence or absence of a fire based on the amount of light detected by the detection elements 4 to 6 and the threshold value stored in the storage unit 7, and if it is determined that there is a fire, This is a control means for performing a notification output for indicating the fact to a predetermined external device. Although the specific configuration of the determination unit 8 is arbitrary, for example, it can be configured as a CPU (Central Processing Unit) that calls, analyzes, and executes a program stored in a predetermined storage medium.

In the sensor 1 configured as described above, the fire detection can be performed as follows. That is, light (external light) from the monitoring area of the sensor 1 enters the inside of the housing 2 through the light receiving window 3. Of this light, only the light including the CO ₂ resonance radiation band passes through an optical filter (not shown) and enters the detection element 4, and the light quantity of this light is detected by the detection element 4. The detection element 4 outputs a signal corresponding to the change in the amount of received light to the determination unit 8. Of the light incident on the inside of the housing 2, light in a band other than the CO ₂ resonance radiation band passes through an optical filter (not shown) and enters the detection elements 5 and 6, respectively. Detected by elements 5 and 6. The detection elements 5 and 6 output a signal corresponding to the change in the amount of received light to the determination unit 8. Then, the determination unit 8 determines whether the amount of light output from the detection elements 4 to 6 exceeds the threshold stored in the storage unit 7. When the threshold value is exceeded, it is determined whether the difference between the output signals from the detection elements 4 to 6 exceeds the threshold value stored in the storage unit 7. It is determined that it has occurred, and a warning is output.

(Reciprocal relationship between the housing 2 and the light receiving window 3)
Next, the mutual relationship between the housing 2 and the light receiving window 3 will be described. 2 is a longitudinal sectional view in the vicinity of the detection element, FIG. 3 is an enlarged view of a main part of FIG. 2, and FIG. 4 is an exploded perspective view of FIG. 2 (detection elements 4 to 6 are omitted). As shown in FIGS. 2 to 4, an opening 20 for fitting the light receiving window 3 is formed in the housing 2. The opening 20 is formed, for example, in a substantially circular shape or a square shape in plan view, and can be formed by die cutting or the like when the casing 2 is injection molded.

  On the other hand, the light receiving window 3 includes a base 30 and a protrusion 31 that are substantially integrated. Among these, the base 30 is formed in a substantially flat plate shape wider than the opening 20, and is fixed to the inside of the housing 2 via a fixing plate 33 described later. On the other hand, the protruding portion 31 protrudes from the surface on the opening 20 side of the base portion 30 toward the opening 20 and is fitted into the opening 20, and is a substantially circular or rectangular plane corresponding to the opening 20. It is formed into a shape. Although the formation method of these base 30 and the protrusion part 31 is arbitrary, for example, it can form by cutting a sapphire glass etc., or it can form by mold-molding arbitrary transparent resins. Here, the base 30 is sandwiched between a pair of fixing plates 33 attached to the housing 2 via screws 32 and the housing 2, whereby the light receiving window 3 is detachable from the housing 2. It is fixed to.

  Here, as shown in FIG. 3, the base 30 is fixed at a position that is substantially close to the inside of the housing 2, and the protruding portion 31 has a wall thickness (with the housing 2 and the housing 2). Therefore, the outer surface 34 of the light receiving window 3 (the outer surface of the protrusion 31) and the outer surface 21 of the housing 2 are substantially flush with each other. That is, the outer surface 34 of the light receiving window 3 and the outer surface 21 of the housing 2 are arranged at substantially the same position in the inner and outer directions of the sensor 1, and form a continuous plane in which both are connected to each other. Yes. Therefore, there is almost no step between the outer side surface 34 of the light receiving window 3 and the outer side surface 21 of the housing 2, and it is difficult for dust and dirt to accumulate between the outer side surfaces 34 and 21. .

(Protective measures)
2 to 4, a protective rubber 40 is disposed between the base 30 of the light receiving window 3 and the housing 2. The protective rubber 40 is for preventing foreign matter from entering the inside of the sensor 1 from between the housing 2 and the base 30 and corresponds to protective means in the claims. The protective rubber 40 is formed so as to surround the entire circumference of the protruding portion 31. For example, when the protruding portion 31 is formed in a substantially plane shape, the protective rubber 40 is also formed in a substantially ring-shaped, protruding shape. When the portion 31 is formed in a substantially planar shape, the protective rubber 40 is also formed in a generally planar annular shape. Further, the thickness of the protective rubber 40 is slightly larger than the distance between the casing 2 and the base 30 and is elastically deformed by being sandwiched between the casing 2 and the base 30. The gaps between the casing 2 and the base 30 are substantially closed. Accordingly, water or the like that has entered from between the housing 2 and the base 30 is sealed by the protective rubber 40 and is prevented from entering the inside of the sensor 1. In addition, as long as such a function can be achieved, the material of the protective rubber 40 is arbitrary, but for example, a synthetic resin can be used.

  As described above, according to the sensor 1 according to the present embodiment, the outer side surface 34 of the light receiving window 3 and the outer side surface 21 of the housing 2 are substantially flush with each other. Since there is no step, it is difficult for dust and dirt to accumulate between the outer surfaces 34 and 21. In addition, the protective rubber 40 sandwiched between the casing 2 and the base 30 substantially closes the gap between the casing 2 and the base 30, so that the gap between the casing 2 and the base 30 can be reduced. Intruded water or the like is sealed with the protective rubber 40 and is prevented from entering the inside of the sensor 1.

[Embodiment 2]
Next, a sensor according to Embodiment 2 will be described. The light receiving window of the first embodiment is configured to include a base portion and a protruding portion substantially integrally. On the other hand, the light receiving window according to the present embodiment is different from the first embodiment in that the light receiving window is formed by separately forming the base portion and the protruding portion and then bonding and fixing each other. More specifically, in the present embodiment, the base portion and the protruding portion are each formed in a substantially flat plate shape, and the base portion and the protruding portion are bonded to each other to constitute a light receiving window. Note that structures and methods that are not particularly described are the same as those in the first embodiment described above, and the same components are described with the same reference numerals.

  FIG. 5 is a longitudinal sectional view of the light receiving window of the sensor according to the second embodiment. As shown in FIG. 5, the base 51 and the protrusion 52 of the light receiving window 50 are each formed in a flat plate shape, and the base 51 and the protrusion 52 are respectively the same as the base 30 of the first embodiment. The protrusion 31 has substantially the same thickness as the thickness of the protrusion 31. The base 51 and the protrusion 52 are bonded via an adhesive layer 53, and as a whole, a light receiving window 50 having substantially the same shape as the light receiving window 3 of the first embodiment is formed. Specific materials for the base 51, the protrusion 52, and the adhesive layer 53 are arbitrary. For example, the base 51 and the protrusion 52 are each formed of sapphire glass, and these are bonded to the adhesive layer 53 with an ultraviolet curable adhesive. Processing (UV bonding) can be performed. The advantages of such a configuration are as follows. That is, when a high-hardness sapphire glass is used as the material of the light receiving window 50, it is difficult to integrally form the shapes such as the base portion 30 and the protruding portion 31 of the first embodiment by cutting or the like. Therefore, as in the present embodiment, when the base portion 51 and the protruding portion 52 are formed in a flat plate shape and bonded to each other, the sapphire glass is simply formed in a flat plate shape, and is cut into a complicated shape. Therefore, the light receiving window 50 can be easily manufactured.

  The advantage of using sapphire glass is that it has high hardness and is not easily damaged, and is suitable for being placed in a portion exposed to the outside of the sensor. Therefore, it is preferable to use sapphire glass for at least the projecting portion 52, but for the base portion 51, another member having a light projecting property, for example, a transparent plastic may be used. Thus, by reducing the usage rate of sapphire glass, the material cost can be reduced, and the formation of the base 51 is further facilitated, so that the manufacturing cost of the light receiving window 50 can be reduced.

  Here, when the adhesive layer 53 is formed as described above, external light enters the detection elements 4 to 6 (not shown in FIG. 5) after passing through the adhesive layer 53. At this time, regarding the influence of the adhesive layer 53 on the detection of external light, the inventor of the present application conducted a confirmation experiment as follows. First, a single sapphire glass plate and a composite sapphire glass plate having substantially the same thickness as the single sapphire glass plate and having two sapphire glasses bonded through an adhesive layer are prepared. . Then, the same light was transmitted through the single sapphire glass plate and the composite sapphire glass plate, and the intensity of each wavelength was measured. As a result, the intensity of each wavelength was the same. Therefore, it was found that there is no influence on the wavelength transmission characteristics by the adhesive layer (absorption of the intrinsic wavelength by the adhesive layer). For this reason, even when the adhesive layer 53 is provided as in the present embodiment, the detection sensitivity can be maintained as in the prior art. In the present invention, an adhesive layer that does not absorb light in the detection wavelength band is selected as the adhesive layer 53. However, the material of the adhesive layer 53 and / or the thickness of the adhesive layer 53 is adjusted as appropriate to obtain a specific wavelength. The adhesive layer 53 may function so as to absorb light in the band.

  As described above, according to the sensor according to the second embodiment, in addition to the same operations and effects as those of the first embodiment, the sapphire glass of the light receiving window 50 may be simply formed in a flat plate shape, and the shape is complicated. Since it is not necessary to perform cutting or the like, the light receiving window 50 can be easily manufactured. Further, by using a member other than sapphire glass for the base 51, the material cost can be reduced and the formation of the base 51 can be further facilitated, so that the manufacturing cost of the light receiving window 50 can be reduced.

[Embodiment 3]
Next, a sensor according to Embodiment 3 will be described. The present embodiment is common to the second embodiment in that the base and the protrusion are formed separately and then bonded and fixed to each other, but the shapes of the base and the protrusion are different. Note that structures and methods that are not particularly described are the same as those in the first embodiment described above, and the same components are described with the same reference numerals.

  FIG. 6 is a longitudinal sectional view of the light receiving window of the sensor according to the third embodiment, and FIG. 7 is a plan view of FIG. As shown in FIGS. 6 and 7, the base 61 and the protrusion 62 of the light receiving window 60 are each generally formed in a flat plate shape. Here, a second opening 63 having a shape substantially corresponding to the planar shape of the protrusion 62 is formed in the base 61, and the protrusion 62 is fitted into the second opening 63. The base 61 has substantially the same thickness as the base 30 of the first embodiment. On the other hand, the protruding portion 62 protrudes from the second opening 63 to the outer surface 21 of the housing 2 (the housing 2 and the outer surface 21 are not shown in FIGS. 6 and 7). It is formed thicker than the portion 31. An adhesive layer 64 is formed on substantially the entire circumference of the portion of the protrusion 62 that is inserted into the second opening 63, and the base 61 and the protrusion 62 are connected via the adhesive layer 64. By being bonded together, a light receiving window 60 having substantially the same shape as the light receiving window 3 of the first embodiment is formed as a whole. The advantages of such a configuration are as follows. That is, even when sapphire glass is used for the protruding portion 62, the sapphire glass of the protruding portion 62 may be simply formed in a flat plate shape as in the second embodiment, and it is not necessary to cut into a complicated shape. The manufacture of the light receiving window 60 is facilitated. Further, there is no adhesive layer on the path through which the external light is transmitted, and the external light is transmitted only through the single projecting portion 62 to the detection elements 4 to 6 (not shown in FIGS. 6 and 7). Since it enters, it can prevent more reliably that external light is absorbed or attenuate | damped by parts other than the protrusion part 62, and can improve a detection sensitivity.

  As described above, according to the sensor according to the present embodiment, the external light is transmitted through only the single projecting portion 62 and is incident on the detection elements 4 to 6, so that the external light is absorbed by portions other than the projecting portion 62. Can be prevented more reliably and the detection sensitivity can be improved.

[III] Modifications to Embodiments While the first to third embodiments of the present invention have been described above, the specific configuration and method of the present invention are the technical ideas of each invention described in the claims. Within the range of, it can be arbitrarily modified and improved. Hereinafter, such a modification will be described.

(About problems to be solved and effects of the invention)
First, the problems to be solved by the invention and the effects of the invention are not limited to the above-described contents, and the present invention solves the problems not described above or has the effects not described above. There are also cases where only some of the described problems are solved or only some of the described effects are achieved. For example, even when dust or dust accumulation on the outer surface 21 of the housing 2 cannot be completely prevented, the effects of the present application are exhibited as long as the adverse effects due to such accumulation can be reduced as compared with the conventional case.

(About sensor)
In the above-described embodiment, the case where the present invention is applied to the sensor 1 (fire detector, fire alarm) that detects only the fire has been described, but the present invention is not limited to this, For example, the present invention can be applied to a fire gas leak detector that detects a fire or gas. Or you may apply this invention to photodetectors, such as a hot-wire type human body detector which detects an intruder, a meteorological observation apparatus for dense fog warnings, etc., and other optical measuring instruments.

(Reception window)
The outer surface 21 of the housing 2 and the outer surface 34 of the light receiving window 3 do not have to be completely flush with each other, and at least a level difference smaller than the level difference between the housing and the light receiving window in the conventional photodetector. It is a concept that includes the case where there is. In the second embodiment, the light receiving window 50 is configured to be stacked in a three-layer shape including the base 51, the adhesive layer 53, and the protruding portion 52. However, the light receiving window 50 may be multilayered into four or more layers. Further, the shape, position, and number of the light receiving windows 3, 50, 60 are not limited to those shown in the embodiment. Further, the structure for fixing the light receiving windows 3, 50, 60 to the housing 2 can be arbitrarily changed.

  As described above, the photodetector according to the present invention is useful for reducing the accumulation of dust and dirt on the outer surface of the housing in the photodetector for detecting the occurrence of fire in the monitoring region. It is suitable for increasing the reliability of a photodetector that is used outdoors over a period of time.

It is a block diagram which illustrates functionally the structure of the sensor which concerns on Embodiment 1 of this invention. It is a longitudinal cross-sectional view of the vicinity of a detection element. It is a principal part enlarged view of FIG. FIG. 3 is an exploded perspective view of FIG. 2. 6 is a longitudinal sectional view of a light receiving window of a sensor according to Embodiment 2. FIG. 6 is a longitudinal sectional view of a light receiving window of a sensor according to Embodiment 3. FIG. FIG. 7 is a plan view of FIG. 6. It is a longitudinal cross-sectional view of the detection element vicinity of the conventional 3 wavelength type sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor 2 Case 3, 50, 60 Light reception window 4-6 Detection element 7 Memory | storage part 8 Judgment part 20 Opening part 21, 34 Outer surface 30, 51, 61 Base 31, 52, 62 Projection part 32 Screw 33 Fixing plate 40 Protective rubber 53, 64 Adhesive layer 63 Second opening

Claims (5)

A housing,
A light receiving window provided on one side of the housing;
A detection element that is disposed inside the light receiving window and detects light incident through the light receiving window;
The light receiving window is fixed inside the housing,
The outer surface of the housing and the outer surface of the light receiving window are substantially flush with each other;
A photodetector characterized by. The housing has an opening for inserting the light receiving window,
The light receiving window is a base fixed to the casing inside the casing, and projects from the base toward the opening to be fitted into the opening. A protrusion having a wall thickness that reaches the outer surface;
The photodetector according to claim 1. The light receiving window is configured by forming the base and the protrusion in a substantially flat plate shape, and bonding the base and the protrusion to each other.
The photodetector according to claim 2. Forming a second opening in the base;
The projecting portion is disposed so as to reach the outer side surface of the housing from the second opening portion, and fixed to the base portion at a connection surface with the second opening portion,
The photodetector according to claim 2. Provided protective means between the housing and the light receiving window to prevent intrusion of foreign matter into the photodetector from between the housing and the light receiving window,
The photodetector according to any one of claims 1 to 4.

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