Patent Publication Number: US-6911648-B2

Title: Sensor assembly

Description:
RELATED APPLICATION 
   This application is a divisional of application Ser. No. 09/667,395 filed Sep. 20, 2000 now U.S. Pat. No. 6,518,565. The disclosure in the aforementioned application Ser. No. 09/667,395 is hereby incorporated herein in its entirety by this reference thereto. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to a sensor assembly which may be utilized to detect objects at a location spaced from the sensor assembly. 
   A known sensor assembly has a light source or emitter from which light is transmitted to an object spaced from the sensor assembly. The light is reflected from the object back through a second lens to a detector. 
   Users of known sensor assemblies have tried to gain access to the interior of the sensor assemblies by engaging wrenching flats on electrical connectors for the sensor assemblies. This can result in unauthorized tampering with the sensor assemblies in a manner which is detrimental to the operation of the sensor assemblies. 
   The lenses in a sensor assembly should be easy to accurately position in the sensor assembly. In addition, the lenses in a sensor assembly should not become loose during use of the sensor assembly. It is also important to have the light source and light detector accurately positioned relative to each other and to the lenses. 
   From a commercial standpoint, it is necessary to minimize the cost of a sensor assembly. It is also desirable to make the sensor assembly compact so that it can be easily positioned in many different environments. There should be minimal reflection of light from components of a sensor assembly. The lenses in a sensor assembly should be protected from the environment in which the sensor assembly is utilized so that the operating qualities of the sensor assembly do not deteriorate with the passage of time. 
   SUMMARY OF THE INVENTION 
   The present invention relates to a new and improved sensor assembly. The sensor assembly includes a light source and a lens which directs light from the light source to a remote object. Light reflected from the remote object is transmitted through another lens to a light detector. 
   The lenses may advantageously be mounted on a lens carrier. The lens carrier is disposed in a housing. The lenses are advantageously connected with the lens carrier by a plurality of releasable connectors. The connectors may be disposed in engagement with the rim portions of the lenses and press the lenses into recesses formed in the lens carrier. The connectors may be of the snap-in type. 
   The sensor assembly may advantageously include a connector assembly which connects the sensor assembly with an electrical conductor. This tamper resistant electrical connector assembly may include a body portion and a flange portion. The flange portion may be movable to engage a recess in the sensor housing and retain the electrical connector assembly against movement along a central axis of body portion of the connector assembly. In order to resist unauthorized access to the interior of the sensor assembly, a retainer may engage the flange portion of the electrical connector assembly and hold the flange portion against movement out of engagement with the recess. 
   The light source and/or the light detector may be movable relative to a circuit board to adjust the distance at which light from the light source is reflected from an object back to the detector. The circuit board may be connected with the lens carrier. A black coating may advantageously be provided on a side of the circuit board facing toward the lenses. 
   The sensor assembly may include one or more of a plurality of features of the present invention. It should be understood that although the features may advantageously be used in combination with each other, the features may also be used separately. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other features of the invention will become more apparent upon a consideration of the following description taken in connection with the accompanying drawings wherein: 
       FIG. 1  is an elevational view of a sensor assembly constructed in accordance with the present invention; 
       FIG. 2  is an exploded view illustrating components of the sensor assembly of  FIG. 1 ; 
       FIG. 3  is an enlarged side elevational view of a lens carrier which holds lenses in the sensor assembly of  FIG. 1 ; 
       FIG. 4  is a sectional view, taken generally along the line  4 — 4  of  FIG. 1 , further illustrating the construction of the sensor assembly; 
       FIG. 5  is a sectional view, taken generally along the line  5 — 5  of FIG.  3  and illustrating the manner in which a lenses are releasably connected with the lens carrier; 
       FIG. 6  is a sectional view, taken generally along the line  6 — 6  of  FIG. 3 , further illustrating the relationship of a lens to the lens carrier; 
       FIG. 7  is an enlarged plan view of one of the lenses in the sensor assembly of  FIG. 1 ; 
       FIG. 8  is an enlarged fragmentary sectional view depicting the manner in which a releasable connector engages a rim of the lens of  FIG. 7  to hold the lens against movement relative to the lens carrier of  FIGS. 3 and 5 ; 
       FIG. 9  is an enlarged fragmentary sectional view, further illustrating the relationship of the rim of the lens of  FIG. 7  to the lens carrier of  FIGS. 3 and 6 ; 
       FIG. 10  is an exploded schematic pictorial illustration depicting the manner in which an electrical connector assembly is positioned relative to an opening in a bottom wall of the housing of the sensor assembly of  FIG. 1 ; 
       FIG. 11  is a schematic illustration depicting the electrical connector assembly in a release position relative to the bottom wall of the sensor housing; 
       FIG. 12  is a schematic illustration, generally similar to  FIGS. 10 and 11 , illustrating the relationship of the electrical connector assembly to the bottom wall of the sensor housing after the electrical connector assembly has been rotated to a secured position and prior to closing of a cover of the sensor housing; 
       FIG. 13  is a fragmentary schematic illustration, generally similar to  FIGS. 11-12 , illustrating the closed cover and a retainer which engages the electrical connector assembly to hold the electrical connector assembly in the secured position; 
       FIG. 14  is a fragmentary schematic illustration depicting the manner in which a detector is mounted on a daughter board or carriage for movement relative to a mother or main circuit board in the sensor assembly of  FIG. 1 ; 
       FIG. 15  is a top plan view, taken generally along the line  15 — 15  of  FIG. 14 , illustrating the manner in which the carriage is retained in a desired position; 
       FIG. 16  is a fragmentary schematic illustration, generally similar to  FIG. 14 , illustrating the relationship of a second embodiment of the movable daughter board or carriage relative to the mother or main circuit board in the sensor assembly of  FIG. 1 ; 
       FIG. 17  is a plan view, taken generally along the line  17 — 17  of  FIG. 16 , further illustrating the relationship of the movable daughter board to the mother board; and 
       FIG. 18  (on sheet  7  of the drawings) is an enlarged fragmentary schematic illustration depicting the manner in which a black coating overlies one side of the circuit board. 
   

   DESCRIPTION OF SPECIFIC PREFERRED EMBODIMENTS OF THE INVENTION 
   General Description 
   A sensor assembly  20 , constructed in accordance with the present invention, is illustrated in  FIGS. 1 and 2 . The sensor assembly  20  includes a housing  22 . The housing  22  includes a flat, generally rectangular, front wall  24  and a flat, generally rectangular, rear wall  26  which extends parallel to the front wall  24 . A pair of rectangular parallel side walls  28  and  30  extend between the front wall  24  and rear wall  26 . Parallel rectangular upper and lower end walls  32  and  34  extend between the side walls  28  and  30 . 
   A cylindrical, externally threaded, mounting section  36  extends from the lower end wall  34 . It is contemplated that the mounting section  36  will be inserted through a circular opening in a base or support member. The mounting section  36  may be connected with the base or support member by an internally threaded member or nut. 
   In the illustrated embodiment of the invention, the housing  22  has a generally rectangular configuration. However, it is contemplated that the housing  22  could have a different configuration if desired. For example, the housing could have a cylindrical configuration. 
   The front wall  24 , side walls  28  and  30 , end walls  32  and  34 , and the mounting section  36  are integrally formed as one piece. In the illustrated embodiment of the invention, the housing  22  is molded of a polymeric material. The front wall  24 , side walls  28  and  30 , end walls  32  and  34 , and mounting section  36  are integrally molded as one piece. The rear wall  26  is molded separately from the remainder of the housing  22  and forms a cover for the housing. 
   In the illustrated embodiment of the sensor assembly  20 , the sensor assembly includes three lenses  40 ,  42  and  44  (FIGS.  2  and  4 ). The center lens  42  is associated with a light source or emitter  48  ( FIG. 4 ) mounted on a rectangular circuit board  50  ( FIGS. 2 and 4 ) disposed within the sensor housing  22 . Upper and lower light detectors  54  and  56  ( FIG. 4 ) are disposed in the housing  22  in association with upper and lower lenses  40  and  44 . 
   The illustrated embodiment of the sensor assembly  20  includes a pair of light detectors  54  and  56  associated with a pair of lenses  40  and  44 . However, a greater or lesser number of light detectors could be provided in association with a greater or lesser number of lenses. In addition, a plurality of light sources and associated lenses could be provided. For example, a single light source  48  and lens  42  could be provided in association with a single light detector  54  and lens  40 . Alternatively, a plurality of light sources and associated lenses could be provided in association with a plurality of light detectors and lenses. 
   The light source  48  is electrically energized to provide radiation which can be sensed by the light detectors  54  and  56 . By providing a pair of light detectors  54  and  56 , the sensor assembly  20  can be utilized to sense the distance of an object from the sensor assembly, that is, the sensor assembly  20  has depth perception. Of course, when depth perception or distance sensing is not required, the number of light detectors could be reduced. 
   It is contemplated that the light source  48  could provide many different types of radiation. Thus, the light source  48  could provide electromagnetic radiation anywhere within a wavelength range which includes the infrared range, visible, ultraviolet, and X-rays. Of course, the light source  48  could be utilized to provide a different type of radiation if desired. 
   In the illustrated embodiment of the invention, the light source  48  provides infrared radiation. Therefore, the detectors  54  and  56  are effective to detect the presence of infrared radiation. Of course, if the light source  48  provided a different type of radiation, the detectors  54  and  56  would be constructed to sense this radiation. 
   The housing  22  is advantageously formed of a material through which light having an infrared wavelength can be transmitted. Light in the visible spectrum is blocked by the material of the housing. In one specific embodiment of the invention, the housing  22  was molded of General Electric Lexan (trademark) polymeric material to which a die of color 21092 was added. The resulting housing is transparent to light in the infrared spectrum while being opaque to light in the visible spectrum. 
   Of course, if the light source  40  provided radiation other than infrared light, the housing  22  would be transparent to whatever radiation was provided by the light source  48 . For example, the light source  48  could be a source of light in the visible spectrum and at least the front wall  24  of the housing  22  would be transparent to light in the visible spectrum. Of course, if this was done, the detectors  54  and  56  would be effective to detect light in the visible spectrum. 
   In the illustrated embodiment of the invention, the lenses  40 ,  42  and  44 , light source  48  and light detectors  54  and  56  are all enclosed within the housing  22 . This protects the lenses  40 ,  42  and  44 , light source  48 , and light detectors  54  and  56  from contaminants in an environment in which the sensor assembly  20  is utilized. In the illustrated embodiment of the invention, the housing  22  is sealed so that contaminants from the environment around the housing can not enter the housing. However, if desired, at least the front wall  24  could be formed with openings to at least partially expose the lenses  40 ,  42  and  44 . 
   When the sensor assembly  20  is to be utilized to detect the presence of objects at a location spaced from the sensor assembly, the light source  48  is electrically energized to provide radiation, specifically, infrared radiation. The infrared radiation is transmitted from the light source  48  through the center lens  42  and front wall  24  to the object to be sensed. Infrared light from the light source  48  is reflected from the object to be sensed through the front wall  24  to the upper and lower lenses  40  and  44 . The upper and lower lenses  40  and  44  direct the reflected infrared light to upper and lower light detectors  54  and  56 . 
   The upper and lower light detectors  54  and  56  provide output signals in response to the reflected infrared light. These output signals indicate the presence of the object at the location which is spaced from the sensor assembly  20 . 
   In the illustrated embodiment of the sensor assembly  20 , light emitting diodes are mounted on the circuit board  50  adjacent to a window  60  which is molded into the upper end wall  32  of the housing  22 . The window  60  is transparent to light in the visible spectrum. Therefore, light can be transmitted from the LEDs through the window  60  to an operator to provide a visible indication of the detection of an object. 
   It should be understood, that with the exception of the window  60 , the housing  22  has a black appearance to a person viewing the housing. This is because the housing  22  is formed of a material which is opaque to light in the visible spectrum while being transparent to infrared light. 
   Lens Carrier 
   In accordance with one of the features of the present invention, the lenses  40 ,  42  and  44  are disposed on a lens carrier  66  ( FIGS. 2 ,  3 ,  4 ,  5  and  6 ). In addition, the circuit board  50 , light source  48 , and light detectors  54  and  56  are disposed on the lens carrier  66 . The lens carrier  66  facilitates accurate positioning of the lenses  40 - 44 , light source  48  and light detectors  54  and  56  relative to each other before they are inserted into the housing  22 . 
   The lens carrier  66  has a generally rectangular configuration ( FIGS. 2 and 3 ) and supports the lenses  40 ,  42  and  44  in the housing  22  (FIG.  4 ). The lens carrier  56  includes a plurality of tubular sections  70 ,  72  and  74 . The tubular sections  70 ,  72  and  74  have parallel central axes  76 ,  78 , and  80  ( FIG. 4 ) which extend through the centers of the lenses  40 ,  42  and  44 . The central axes  76  and  80  of the tubular sections  70  and  74  extend through the centers of the light detectors  54  and  56 . Similarly, the central axis  78  of the tubular section  72  extends through the center of the light source  48 . 
   The lens carrier  66  has a mounting section  84  ( FIG. 3 ) disposed between the tubular sections  70  and  72  and offset to the right of the central axes  76  and  78  ( FIG. 4 ) of the tubular sections  70  and  72 . A second mounting section  86  (FIG.  3 ), having the same construction as the mounting section  84 , is disposed between the tubular sections  72  and  74 . The mounting section  86  is offset to the left (as viewed in  FIG. 3 ) of the central axes  78  and  80  ( FIG. 4 ) of the tubular sections  72  and  74 . 
   The lens carrier  66  is connected to the housing  22  by fasteners  90  and  92  ( FIG. 2 ) which extend through openings in the mounting sections  84  and  86  into openings in ribs formed on the side walls  28  and  30  ( FIG. 2 ) of the housing  22 . Although only a single rib  96  on the side wall  28  for receiving the fastener  92  is illustrated in  FIG. 2 , it should be understood that a similar rib is formed on the side wall  30  of the housing  22  and has an opening to receive the fastener  90 . The fasteners  90  and  92  cooperate with the mounting sections  84  and  86  and the ribs  96  to accurately position and securely retain the lens carrier  66  in the housing  22 . 
   The mounting sections  84  and  86  ( FIG. 3 ) cooperate with the ribs  96  in the housing  22  to enable the lens carrier  66  to be inserted into a rectangular chamber  100  ( FIG. 2 ) in the housing  22  only when the lenses  40 ,  42  and  44  are leading so that the lenses are disposed adjacent to the front wall  24  in the manner illustrated in FIG.  4 . The tubular sections  70 ,  72  and  74  have rear end walls  104 ,  106  and  108  ( FIG. 3 ) which enable light to be transmitted between the lenses  40 ,  42  and  44  and the light source  48  and light detectors  54  and  56  mounted on the circuit board  50  (FIG.  4 ). Thus, the end walls  70  and  74  have central slots  112  and  114  ( FIG. 3 ) which are aligned with the upper and lower light detectors  54  and  56  (FIG.  4 ). Similarly, the end wall  106  has a central opening  118  ( FIG. 3 ) which is aligned with the light source  48 . It should be understood that the openings  112 ,  114  and  118  could have a different configuration if desired. 
   In the illustrated embodiment of the invention, the lens carrier  66  is integrally formed as one piece. The lens carrier  66  may be integrally molded of a polymeric material which blocks the transmission of infrared radiation. This results in infrared light and in visible light being blocked by the lens carrier. However, if desired, the lens carrier  66  could be formed of a different material. 
   Generally cylindrical tubes  122 ,  124  and  126  ( FIG. 2 ) of flock paper line cylindrical chambers in the tubular sections  70 ,  72  and  74  (FIG.  4 ). The tubes  122 ,  124  and  126  have black inner surfaces  128 ,  130  and  132  with a velvety texture. This enables the tubes  122 ,  124  and  126  ( FIG. 4 ) to absorb stray rays of light. It is contemplated that the tubes  122 ,  124  and  126  could be formed of material other than flock paper if desired. In fact, the tubes  122 ,  124  and  126  could be omitted if desired and the sides of the interior surfaces of the tubular sections  70 ,  72  and  74  of the lens carrier  66  could be coated with a black material which has a rough or velvety surface and which absorbs light. 
   The tubes  122 ,  124  and  126  extend between the lenses  40 ,  42  and  44  and the end walls  104 ,  106  and  108  of the tubular sections  70 ,  72  and  74  ( FIGS. 3 ,  4 ,  5 , and  6 ). Thus, the end of the tube  124  ( FIG. 5 ) closest to the front wall  24  ( FIG. 4 ) of the housing  22  is disposed in abutting engagement with the lens  42  (FIGS.  5  and  6 ). The opposite end of the tube  124  is disposed in abutting engagement with the end wall  106  of the tubular section  72 . Although only the relationship between the flock paper tube  124  and the tubular section  72  of the lens carrier  66  is illustrated in  FIGS. 5 and 6 , it should be understood that the tubes  122  and  126  in the tubular sections  70  and  74  ( FIG. 4 ) are also disposed in engaged with their associated lenses  40  and  44  and housing end walls  104  and  108  (FIG.  3 ). 
   The lens carrier  66  has a plurality of arcuate shields  134 ,  136 ,  138 ,  140 ,  142  and  144  ( FIGS. 3 and 4 ) which block the transmission of light between the tubular sections  70 ,  72  and  74  of the lens carrier. The shields  134 - 144  are disposed in abutting engagement with an inner side surface  148  ( FIG. 4 ) of the front wall  24 . Therefore, the shields  134 - 144  are effective to block the direct transmission of light between the tubular sections  70 ,  72  and  74  of the lens carrier  66 . 
   The lens carrier  66  supports the lenses  40 ,  42  and  44 . The lenses  40 ,  42  and  44  are positioned in abutting engagement with the inner side surface  148  of the front wall  24  by the lens carrier  66 . However, if desired, the lens carrier  66  could be constructed so as to position the lenses  40 ,  42  and  44  in a spaced apart relationship with the front wall  24  of the housing  22 . 
   The front wall  24  of the housing  22  extends across and protects the lenses  40 ,  42  and  44 . The smooth, flat front wall  24  of the housing  20  is relatively easy to clean. The lenses  40 ,  42  and  44  are protected from dust, dirt and other contaminants in the environment in which the sensor assembly  20  is used. 
   It is preferred to utilize the lens carrier  66  to position the lenses  40 ,  42  and  44  relative to each other while the lens carrier  66  is outside of the housing  22 . The lens carrier  66  and lenses  40 ,  42  and  44  can then be inserted into the housing  22  as a unit with the lenses accurately positioned relative to each other. However, if desired, the lens carrier  66  could be omitted. If this was done, the housing  22  would be constructed so as to have supporting surfaces for engaging the lenses  40 ,  42  and  44 . It is preferred to completely enclose the lenses  40 ,  42  and  44  in the sealed housing  22 . However, if desired, openings could be provided in the front wall  24  to expose the lenses  40 ,  42  and  44 . 
   Lens Connectors 
   In accordance with another one of the features of the present invention, lens connectors  156  are provided to releasably connect the lenses  40 ,  42  and  44  with the lens carrier  66 . The lens connectors  156  enable the lenses  40 ,  42  and  44  to be quickly and accurately positioned relative to the lens carrier  66 . The lens connectors  156  also enable a lens  40 ,  42  or  44  to be easily connected with and subsequently disconnected from the lens carrier  66 . 
   The specific lens connectors  156  disclosed herein for connecting the lenses  40 ,  42  and  44  with the lens carrier  66 , are resiliently deflectable snap-in type connectors. However, it is contemplated that the lens connectors  156  could have a different construction if desired. For example, the lens connectors  156  could have thread convolutions which engage thread convolutions on the lens carrier  66  to retain the lenses  40 ,  42  and  44  in place. Alternatively, the lens connectors  156  could be formed by a plurality of fasteners which are connected with the lens carrier  66  by a threaded connections or by snap-in connections. 
   The specific lens connectors  156  disclosed herein are resilient fingers which are integrally formed as one piece with the lens carrier  66 . The resilient lens connectors  156  are deflectable by the lenses  40 ,  42  and  44  to enable the lenses to snap into place on the lens carrier. However, the lens connectors  156  could be integrally formed as one piece with the lenses  40 ,  42  and  44  if desired. 
   In order to provide the sensor assembly  20  with a relatively compact construction, the lenses  40 ,  42  and  44  are all formed with a noncircular configuration. Thus, the lens  42  ( FIG. 7 ) has a rim portion  160  which extends around the lens  42 . The rim portion  160  includes a plurality of linear side sections  162  and  164 . The side sections  162  and  164  extend parallel to each other. Although a pair of parallel side sections  162  and  164  are provided on the rim portion  160 , it is contemplated that the rim portion could be provided with a greater or lesser number of linear side sections. If a greater number of linear side sections are provided, the side sections could be skewed relative to each other. 
   The rim portion  160  of the lens  42  also includes a plurality of arcuate sections  166  and  168 . The arcuate sections  166  and  168  have centers of curvature which are coincident with the center of the lens  42 . Although the lens  42  has an oval configuration, it should be understood that the lens  42  could have a rectangular configuration if desired. For example, the arcuate sections  166  and  168  could at least be partially replaced by linear sections. This would have the effect of reducing the vertical extent (as viewed in  FIGS. 1 and 4 ) of the sensor assembly  20 . 
   The rim portion  160  forms a rib or flange which extends outward from a main portion  172  of the lens  42 . The main portion  172  of the lens  42  has convex inner and outer side surfaces  174  and  176  ( FIGS. 5 ,  6  and  8 ). The outer side surface  174  of the lens  42  has a smaller radius of curvature than the inner side surface  176 . The inner side surface  176  is almost flat and, if desired, may be flat. 
   The rim portion  160  is releasably engaged by the lens connectors  156  to hold the lens  42  against movement relative to the lens carrier  66 . Thus, the lens connector  156  of  FIG. 8  has a retainer surface  180  which presses the arcuate section  166  of the rim portion  160  of the lens  42  firmly against an end of the lens carrier  66 . The lens connector  156  continuously applies force to press the lens  42  against the lens carrier  66 . In the illustrated embodiment of the invention, there are four lens connectors  156  for each lens  40 ,  42  and  44 . However, a larger or smaller number of lens connectors  156  could be provided for each lens  40 ,  42  and  44  if desired. 
   The lens carrier  66  is formed with a recess  184  having a configuration and size which is the same as the configuration and size of the main portion  172  of the lens  42 . The main portion  172  of the lens  42  is telescopically received in the recess  184  in the lens carrier  66 . This enables the lens connectors  156  to hold the main portion  172  of the lens  42  in the recess  184 . The recess  184  has linear side surface portions and arcuate side surface portions. This enables the linear side sections  162  and  164  of the rim portion  160  to cooperate with corresponding side surfaces of the recess  184  in the lens carrier  66  to hold the lens  42  against rotational movement relative to the lens carrier  66 . Although only the lens carrier recess  184  for the lens  42  is illustrated in  FIGS. 8 and 9 , it should be understood that the lens carrier  66  has a separate recess for each of the lenses  40 ,  42  and  44 . 
   In the illustrated embodiment of the invention, the lens connectors  156  engage the arcuate sections  166  and  168  of the rim portion  160  of the lens  42  to hold the lens  42  in the recess  184  (see  FIG. 5 ) in the lens carrier  66 . The linear side sections  162  and  164  ( FIGS. 6 and 7 ) of the lens  42  cooperate with the recess  184  to hold the lens against rotation relative to the recess. However, additional lens connectors  156  could be provided to engage the linear side sections  162  and  164  of the lens  42  if desired. 
   In the illustrated embodiment of the invention, the lens connectors  156  are integrally formed as one piece with the lens carrier  66  and are resiliently deflected by the rim portion  160  of the lens  42  when the lens is snapped into the recess  184 . Thus, the arcuate section  166  of the rim portion  160  of the lens  42  engages a cam surface  192  ( FIG. 8 ) on the lens connector to resiliently deflect the lens connector toward the left (as viewed in FIG.  8 ). As this occurs, the lens  42  moves downward into the recess  184 . As the lens  42  moves downward (as viewed in  FIG. 8 ) into the recess  184 , the resiliently deflected lens connector  156  snaps back to the position shown in FIG.  8 . As this occurs, the retainer surface  180  on the connector  156  engages the arcuate section  166  of the rim portion  160  to press the lens  42  firmly against the lens carrier  66  and to hold the lens  42  in the lens carrier. 
   In the illustrated embodiment of the invention, the lens connectors  156  engage the arcuate sections  166  and  168  of the lens  42  ( FIGS. 5 ,  7  and  8 ). The lens connectors  156  do not engage the linear side sections  162  and  164  of the lens  42  (FIGS.  6  and  9 ). However, if desired, lens connectors  156  could be provided to engage the linear side sections  162  and  164  of the rim portion  160  of the lens. 
   The illustrated lens connectors  156  have a relatively short arcuate extent (see  FIGS. 2 ,  3  and  5 ) along the arcuate sections  166  and  168  of the rim portion  160 . If desired, the extent of the lens connectors along the rim portions  160  could be increased to increase the extent of engagement of the lens connectors with the rim portion of the lens. 
   Although only the lens connectors  156  for the lens  42  are illustrated in  FIGS. 8 and 9 , it should be understood that the lens connectors  156  all have the same construction and cooperate with rim portions  160  of the lenses  40 ,  42  and  44  in the same manner. Although only the lens carrier recess  184  for the lens  42  is illustrated in  FIGS. 8 and 9 , it should be understood that the lens carrier  66  is provided with a separate recess  184  for each of the lenses  40 ,  42  and  44 . Of course, if a greater or lesser number of lenses was utilized in the sensor assembly a greater or lesser number of recesses  184  would be provided in the lens carrier  66 . 
   Only the lens  42  is illustrated in FIG.  7 . It should be understood that the lenses  40 ,  42  and  44  all have the same construction. The lenses  40 ,  42  and  44  are molded from a suitable polymeric material. If desired, the lens connectors  156  could be integrally molded as one piece with the lenses  40 ,  42  and  44 . If this was done, the lens connectors would extend axially from the rim portions  160  of the lenses  40 ,  42  and  44  into engagement with the lens carrier  66 . 
   The lens connectors  156  and lens carrier recesses  184  cooperate with the lenses  40 ,  42  and  44  to firmly and securely hold the lenses  40 ,  42  and  44  in the sensor assembly  20 . The lens carrier recesses  184  hold the lenses  40 ,  42  and  44  against rotation about central axes of the lenses and against sidewise movement. The lens connectors  156  continuously press the lenses  40 ,  42  and  44  into the lens carrier recesses  184  to prevent rattling of the lenses. Therefore, the lens carrier  66  and lens connectors  156  cooperate with the lenses  40 ,  42  and  44  to ensure that the focal length of the optical system in the sensor assembly  20  is maintained. 
   Connector Assembly 
   An electrical connector assembly  200  ( FIG. 4 ) is utilized to connect the sensor assembly  20  with an electrical conductor. In accordance with another feature of the invention, the connector assembly  200  impedes access to the interior of the sensor housing  22 . To this end, the electrical connector assembly  200  is free of externally accessible elements, such as wrenching flats, which can be engaged to disconnect the electrical connector assembly from the housing  22 . In addition, the connector assembly  200  is relatively simple in construction, easy to install and thereby tends to minimize the cost of the sensor assembly  20 . 
   The connector assembly  200  ( FIG. 4 ) includes a plurality of terminals or prongs  204  which are connected with the circuit board  50  by electrical conductors  208 . Although the illustrated electrical conductors  208  are flexible insulated wires, it is contemplated that suitable sheet metal terminals could be utilized in an interconnected between the connector assembly  200  and the circuit board  56  if desired. 
   The connector assembly  200  includes a generally cylindrical body portion  210  and a flange portion  212 . The body portion  210  of the connector assembly  200  is telescopically received in the mounting section  36 . A pair of coaxial O-rings  216  and  218  extend around the body portion at axially spaced apart locations along the body portion. 
   To maintain a desired axial spacing between the O-rings  216  and  218 , the O-rings are disposed in axially spaced apart grooves  220  and  222  in the body portion  210  of the connector assembly  200 . The O-rings  216  and  218  sealingly engage an inner side surface of the mounting section  36 . The O-rings  216  and  218  seal the cylindrical opening in the mounting section  36  so that contaminants can not enter the housing  22 . 
   A cylindrical socket chamber  228  ( FIG. 4 ) is provided on the outer end portion of the connector assembly  200  to telescopically receive a connector secured to an electrical conductor. The connector secured to the electrical conductor (not shown) has suitable sockets which are engaged by the terminals  204  and  206 . Of course, the connector assembly  200  could be provided with sockets which are engaged by terminals on the connector which is connected with the electrical conductor if desired. 
   In accordance with one of the features of the invention, the connector assembly  200  is retained in the sensor housing  22  by engagement of the flange portion  212  with a recess or slot  230  formed in the housing  22 . The body portion  210  is rotatably received in a cylindrical opening  232  (FIGS.  4  and  10 ). The opening  232  extends through the lower end wall  34  and through the mounting section  36 . 
   The longitudinally extending recess  230  ( FIG. 10 ) has a central axis which extends perpendicular to a central axis  236  of the opening  232 . The recess  230  is offset to one side, that is, toward the side wall  28 , from the opening  232 . The recess  230  has an axial extent which is greater than the length of the flange portion  212  (FIG.  11 ). 
   When the connector assembly  200  is to be positioned in the housing  22 , the cylindrical body portion  210  of the connector assembly is axially aligned with the opening  232  (FIG.  10 ). At this time, an index corner  240  on the rectangular flange portion  212  ( FIG. 10 ) is aligned with an arcuate positioning surface  242  on the inside of the housing  22 . The positioning surface  242  cooperates with the index corner  240  on the flange portion  212  so that the connector assembly  200  can be inserted into the housing in only one orientation. 
   As the connector assembly  200  is moved into the housing  22 , the body portion  210  moves into the opening  232 . As the connector assembly  200  continues to move along the central axis  236  of the opening  232 , the flange portion  212  moves into abutting engagement with the lower end wall  34  of the housing  22  (FIG.  11 ). When this occurs, the connector assembly  200  is accurately positioned relative to the housing  22 . The O-rings  216  and  218  ( FIGS. 4 and 10 ) on the body portion  210  of the connector assembly are disposed in sealing engagement with the cylindrical inner side surface of the opening  232  extending through the mounting section  36 . 
   The connector assembly  200  is then rotated in a counterclockwise direction (as viewed in  FIG. 11 ) to the position illustrated in FIG.  12 . As this occurs, a corner portion  246  of the flange portion  212  moves into the recess or slot  230 . Once the corner portion  246  has entered the slot  230 , the connector assembly  200  is held against axial movement by the housing  22 . Therefore, if an axially upward (as viewed in  FIG. 4 ) force is applied against the connector assembly  200 , engagement of the corner portion  246  with the recess or slot  230  ( FIG. 12 ) in the housing  22  blocks axially upward (as viewed in  FIG. 4 ) movement of the connector assembly  200 . 
   In the illustrated embodiment of the invention, the slot or recess  230  ( FIG. 12 ) is formed by an elongated retainer section  250  of the housing  22 . The retainer section  250  is integrally formed as one piece with the lower end wall  34  and side wall  28  of the housing  22 . If desired, the recess  230  and retainer section  250  could be formed in a different manner and could have a different configuration. 
   It is contemplated that the recess or slot  230  could be formed in the housing  22  in a manner other than by the provision of the elongated retainer section  250 . For example, a relatively small overhanging shelf could be provided adjacent to the lower end wall  34  of the housing  22 . Although only a single retainer section  250  is provided in the illustrated embodiment of the invention, it is contemplated that a pair of recesses or slots  230  could be provided in the housing  22  to engage opposite corners on the flange portion  212  of the connector assembly  200 . 
   In order to prevent removal of the connector assembly  200  once the sensor assembly  20  has been assembled, the retainer flange or finger  254  is provided to block clockwise (as viewed in  FIGS. 12 and 13 ) rotational movement of the connector assembly  200 . In the illustrated embodiment of the invention, the rear wall  26  of the housing  22  is formed on a cover portion  258 . After all of the components of the sensor assembly  20  have been positioned in the housing  22 , the cover portion  258  is moved downward (as viewed in  FIG. 12 ) into engagement with the main portion of the housing. The cover portion  258  is then secured in place by a suitable adhesive. Securing of the cover portion  258  in place is facilitated by a plurality of pins  262  which extend from the cover portion and are received in suitable sockets formed in the housing  22  at the corners of the housing. 
   Once the cover portion  258  has been secured in place, as shown in  FIG. 13 , a generally L-shaped recess  266  ( FIG. 12 ) defined by the retainer flange  254  engages a corner portion  268  of the flange portion  212  ( FIG. 13 ) to hold the connector assembly  20  against clockwise rotation relative to the housing  22 . Thus, the flange  254  engages the corner portion  268  and blocks rotational movement of the corner portion  268  into alignment with the retainer section  250 . Therefore, the corner portion  246  of the flange portion  212  remains in the recess  230 . 
   In the illustrated embodiment of the invention, the flange portion  212  of the connector assembly ( FIG. 10 ) is integrally formed as one piece with the body portion  210  of the connector assembly. Thus, both the flange portion  212  and body portion  210  of the connector assembly  200  are integrally molded from a suitable polymeric material. It is contemplated that the same polymeric material and pigment which is utilized to form the housing  22  may also be utilized to form the connector assembly  210 . 
   The flange portion  212  may be formed separately from the body portion  210 . If this is done, the flange portion  212  may be fixedly connected with the body portion  210 . Both the body portion  210  and the flange portion  212  would rotate together between the position shown in FIG.  11  and the position shown in FIG.  12 . 
   Alternatively, the flange portion  212  may be rotatably connected with the body portion  210  of the connector assembly  200 . This would enable the flange portion  212  to be rotated relative to the housing  22  while the body portion  212  of the connector assembly  200  remains stationary relative to the housing. If the flange portion  212  is formed separately from the body portion  210  of the connector assembly  200 , the flange and body portions could be formed of different materials. For example, the flange portion  212  could be formed of metal while the body portion  210  is formed of a polymeric material. 
   The illustrated connector assembly  200  has a generally square flange portion  212  (FIG.  10 ). However, it is contemplated that the flange portion  210  could have a different configuration if desired. For example, the flange portion  212  could have a generally ovoid configuration with a circular portion which is connected with the body portion  210  and an outwardly projecting arm portion. The outwardly projecting arm portion may be received in the recess  230  to hold the connector assembly  200  against axial movement relative to the housing  22 . Alternatively, the flange portion  212  could be formed with a pair of outwardly extending arms which would be received in recesses in the housing  22  disposed at opposite sides of the opening  232 . 
   Circuit Board 
   The circuit board  50  ( FIGS. 2 and 4 ) is mounted on the lens carrier  66 . Thus, the circuit board  50  is mounted on a rearwardly facing end portion of the lens carrier  66  opposite from the lenses  40 ,  42  and  44 . The circuit board  50  is fixedly connected to the lens carrier  66  by a plurality of fasteners  280  (FIG.  2 ). 
   By mounting the lenses  40 ,  42  and  44  on the rightwardly (as viewed in  FIG. 2 ) facing end portion of the lens carrier  66  and the circuit board  50  on the leftwardly facing (as viewed in  FIG. 2 ) end portion of the lens carrier  66  prior to insertion of the lens carrier into the housing  22 , fabrication of the sensor assembly  20  is facilitated. Thus, the lens carrier  66 , tubes  122 ,  124  and  126  (FIG.  2 ), lenses  40 ,  42 , and  44 , and circuit board  50  are all interconnected while the lens carrier  56  is spaced from the housing  22 . These components are then inserted into the housing  22  as a unitary module. 
   Although it is preferred to mount the circuit board  50  on the lens carrier  66  in the manner illustrated in  FIG. 4 , it is contemplated that the circuit board  50  could be mounted in the housing separately from the lens carrier if desired. For example, the circuit board  50  could be connected with the cover portion  258  of the housing  22 . Alternatively, the circuit board  50  could be connected with suitable mounting lugs mounted on the side walls  28  and  30  and/or end walls  32  and  34  of the housing  22 . 
   In accordance with one of the features of the present invention, the position of the light source  48 , upper light detector  54  and lower light detector  56  ( FIGS. 2 and 4 ) can be adjusted relative to each other. By adjusting the positions of the light source  48 , upper light detector  54  and lower light detector  56  relative to each other, the location of an object from which infrared red light from the light source  48  is reflected back to the light detectors  54  and  56  can be adjusted. This enables the effective operating range of the sensor assembly  20  to be adjusted. 
   In the illustrated embodiment of the invention, the light detectors  54  and  56  are movably mounted on the circuit board  50  to enable their positions to be adjusted relative to the light source  48 . However, it is contemplated that the light source  48  could also be movably mounted on the circuit board  50  to enable the position of the light source to also be adjusted. 
   To facilitate positioning of the light source  54  relative to the circuit board  50 , the upper lens  40  and the light source  48 , the upper light detector  54  is mounted on a daughter board or carriage  286  (FIGS.  4  and  14 ). The daughter board or carrier  286  is received in a slot  288  formed in a main or mother board  290 . The daughter board  286  and mother board  290  are part of the circuit board  50 . 
   The slot  288  ( FIGS. 2 and 4 ) in the main or mother board  290  is aligned with the slot  112  ( FIGS. 2 and 3 ) formed in the rear end wall  104  of the tubular section  70  of the lens carrier  66 . The slot  288  in the mother or main board  290  is slightly wider than the slot  112  in the rear end wall  104  of the tubular section  70  of the lens carrier ( FIGS. 2 ,  14  and  15 ). This enables the carriage or daughter board  286  to be supported by the end wall  104  of the lens carrier  66  as the carriage or daughter board is moved along the slot  288  in the main or mother board  290  (FIG.  15 ). 
   Thus, once the circuit board  50  has been fixedly connected with the lens carrier  66 , the carriage  286  on which the light detector  254  is mounted is moved along the slot  288  in the mother board  290 . During this movement, the carriage  286  engages the rear end wall  104  ( FIGS. 3 and 15 ) of the tubular section  70  of the lens carrier  66  to support the carriage. At this time, the light detector  54  is aligned with and disposed in the slot  112  in the rear end wall  104  of the tubular section  70  (FIG.  14 ). 
   Once it has been determined that the light detector  54  has a desired position relative to the mother or main board  290 , the carriage  286  is fixedly connected to the mother or main board. This may be accomplished by soldering a pair of wires  296  and  298  (FIG.  15 ), which extend across the carriage  286 , to both the carriage and the mother or main board  290 . 
   By having the position of the light detector  54  adjustable relative to the light source  48 , the light detector is effective to detect light reflected from an object at a predetermined distance from the sensor assembly  20 . Thus, the closer the light detector  54  is to the light sensor  48 , the greater is the distance at which light will be reflected from an object to the upper light detector  54 . Similarly, the further the upper light detector  54  is from the light source  48 , the smaller is the distance at which light from the light source  48  will be reflected from an object to the upper light detector  54 . Since the effective operating range of the sensor assembly  20  is determined by the distance at which light from the light source  48  is reflected from an object back to the light detectors  54  and  56 , accurate positioning of the light detectors  54  and  56  relative to the light source  48  is important. 
   Although only the upper light source  54  is illustrated in  FIGS. 14 and 15 , it should be understood that the lower light source  56  ( FIG. 4 ) is mounted on a carriage or daughter board  304  having the same construction as the carriage  286 . The carriage  304  is movable along a slot  306  in the mother or main board  290  to position the light detector  56  relative to the light source  48 . The light detector  56  detects light which is reflected from an object and transmitted through the lens  44  to the light detector. The light detector  56  is aligned with the slot  114  ( FIG. 3 ) in the rear end wall  108  of the tubular section  74  of the lens carrier  66 . Suitable fasteners, corresponding to the wires  296  and  298 , are provided to secure the carriage or daughter board  304  to the main or mother board  290 . In the embodiment of the invention illustrated in  FIGS. 14 and 15 , the carriage  286  is moved along the slot  288  in the mother or main board  290  to a desired position. The wires  296  and  298  are then fixedly connected with the carriage or daughter board  286  and the main or mother board  290  to hold the carriage in the desired position. 
   In the embodiment of the invention illustrated in  FIGS. 16 and 17 , a drive mechanism is connected with the carriage to enable the position of the light detector to be adjusted. Since the embodiment of the invention illustrated in  FIGS. 16 and 17  is generally similar to the embodiment of the invention illustrated in  FIGS. 14 and 15 , similar numerals will be utilized to designate similar components, the suffix letter “a” being added to the numerals of  FIGS. 16 and 17  to avoid confusion. 
   A light detector  54   a  ( FIG. 16 ) is mounted on a carriage or daughter board  286   a . The carriage or daughter board  286   a  is movable relative to a mother or main board  290   a  by a drive mechanism  320 . The drive mechanism  320  includes a screw  322  which is rotatably supported by a pair of support elements  324  and  326 . The support elements  324  and  326  are fixedly connected to the mother or main board  290   a  and hold the screw  322  against axial movement relative to the mother or main board  290   a.    
   A generally U-shaped bracket  330  is fixedly connected to the carriage or daughter board  286   a . The bracket  330  has upstanding (as viewed in  FIG. 16 ) sections  334  and  336  which are engaged by an external thread on the screw  322 . Therefore, upon rotation of the screw  322 , the bracket  330  and carriage  286   a  are moved along a slot  288   a  formed in the mother or main board  290   a.    
   The longitudinally extending slot  288   a  in the mother or main board  290   a  is aligned with a longitudinally extending slot  112   a  in an end wall  104   a  of the tubular section  70   a  of the lens carrier  66   a . The slot  288   a  in the main or mother board  290   a  is wider than the slot  112   a  in the end wall  104   a  of the lens carrier  66   a  (FIG.  17 ). Therefore, the end wall  104   a  of the lens carrier  66   a  is effective to support the carriage or daughter board  286   a  as it is moved along the slot  288   a  in the main or mother board  290   a  by operation of the drive mechanism  320 . Although only the drive mechanism  320  for moving the carriage  286   a  has been illustrated in  FIGS. 16 and 17 , it should be understood that a similar drive mechanism is provided to move a light detector corresponding to the light detector  56  of  FIG. 4 , relative to the circuit board  50   a  and a light source corresponding to the light source  48  of FIG.  4 . 
   In the embodiment of the invention illustrated in  FIGS. 14 and 15 , the carriage  286  and detector  54  are moved to a desired position relative to the light source  48  and then fixedly secured in that position by the wires  296  and  298 . In the embodiment of the invention illustrated in  FIGS. 16 and 17 , the carriage  286   a  and light source  54   a  are moved to a desired position relative to a light source corresponding to the light source  48  of  FIG. 4 , by operating the drive mechanism  320 . It is contemplated that the drive mechanism  320  could be locked so that once the position of the carriage  286   a  and light source  54   a  has been adjusted, their positions can not be readily changed. Alternatively, the drive mechanism  320  may be accessible from outside of the sensor assembly so that a user could adjust the position of the carriage  286   a  and light source  54   a.    
   Black Coating 
   Portions of the circuit board  50  are exposed to the interior of the tubular sections  70 ,  72  and  74  ( FIGS. 2 and 4 ) of the lens carrier  66 . In addition, wiring extends through openings between opposite sides of the circuit board  50 . These openings, which may be referred to as vias, and the surface area of the circuit board  50  may result in an increase in the magnitude of background light within the sensor assembly  20 . This background light may tend to impair the operating characteristics of the sensor assembly. 
   In order to minimize unwanted background light, a black coating  344  ( FIG. 18 ) is applied to a side  346  of the circuit board  50  which faces towards the lenses  40 ,  42  and  44 . The black coating  344  extends across openings or vias  348  which extend between the front side  346  of the circuit board  50  and a rear side  352  of the circuit board  50 . A circuit component, such as a wire  354 , extends through the opening  348 . It should be understood that the wire  354  should be considered as merely being representative of many different circuit components and/or mountings for circuit components, which may extend through openings in the circuit board  50 . 
   The black coating  344  extends across the front end portion of the opening  348  to block transmittal of light through the opening. In addition, the black coating  344  blocks light from passing through laminations which form the circuit board  50 . The black coating  344  also reduces stray light reflections within the sensor assembly  20 . 
   The black coating  344  advantageously has an irregular surface which faces towards the lenses  40 - 44  in order to enhance the light absorbing characteristics of the black coating. The black coating may be formed by a non-reflective layer of black paint which may be referred to as flat black paint. Alternatively, the coating  344  could be formed with a velvety surface similar to the surface of flock paper. 
   In one specific instance, the light absorbing black coating  344  was an epoxy paint. However, it is contemplated that the black coating  344  could be formed of other materials if desired. For example, the black coating  344  could be formed by a black layer which is secured to the circuit board  50  by a suitable adhesive. 
   The black coating  344  has been illustrated in  FIG. 18  as being applied to the main or mother board  290 . It is also contemplated that the black coating  344  will extend across the sides of the carriages  286  and  304  ( FIG. 4 ) which face toward the lenses  40 ,  42  and  44 . It is believed that it may be advantageous to extend the flat black coating to the side surfaces of the slots  288  and  306  along which the carriages  286  and  304  are movable. Thus, the black coating  344  would cover not only the side of the mother board or main section  290  which faces toward the lenses  40 - 44  but could also cover the sides of the carriages or daughter boards  286  and  304  which face toward the lenses and the sides of the slots  288  and  306  and/or the sides of the carriages  286  and  304  which extend between the front side  346  and rear side  352  of the circuit board  50 . 
   Conclusion 
   The present invention relates to a new and improved sensor assembly  20 . The sensor assembly  20  includes a light source  48  and a lens  42  which directs light from the light source to a remote object. Light reflected from the remote object is transmitted through another lens  40  to a light detector  54 . 
   The lenses  40  and  42  may advantageously be mounted on a lens carrier  66 . The lens carrier  66  is disposed in a housing  22 . The lenses  40  and  42  are advantageously connected with the lens carrier  66  by a plurality of releasable connectors  156 . The connectors  156  may be disposed in engagement with the rim portions  160  of the lenses  40  and  42  and press the lenses into recesses  184  formed in the lens carrier  66 . The connectors  156  may be of the snap-in type. 
   The sensor assembly  20  may advantageously include a connector assembly  200  which connects the sensor assembly with an electrical conductor. This tamper resistant electrical connector assembly  200  may include a body portion  210  and a flange portion  212 . The flange portion  212  may be movable to engage a recess  230  in the sensor housing  22  and retain the electrical connector assembly  200  against movement along a central axis of body portion of the connector assembly. In order to resist unauthorized access to the interior of the sensor assembly, a retainer  254  may engage the flange portion  212  of the electrical connector assembly and hold the flange portion  212  against movement out of engagement with the recess. 
   The light source  48  and/or the light detector  54  may be movable relative to a circuit board  50  to adjust the distance at which light from the light source is reflected from an object back to the detector. The circuit board  50  may be connected with the lens carrier  66 . A black coating  344  may advantageously be provided on a side of the circuit board  50  facing toward the lenses. 
   The sensor assembly  20  may include one or more of a plurality of features of the present invention. It should be understood that although the features may advantageously be used in combination with each other, the features may also be used separately. For example, the lens connectors  156  may be used in combination with or separately from the electrical connector assembly  200 . Similarly, the lens carrier  66  may be used separately or in combination with the lens connectors  156  and/or electrical connector assembly  200 .