Abstract:
An Improved Circuit Design and Optics System for Infrared Signal Transceivers is disclosed. The preferred system includes an IR transceiver assembly that is easily grasped by assemblers. Furthermore, the primary and secondary lenses associated with the transceiver system are easier to manufacture than current lens designs. Also, the heretofore critical lens separation between the infrared emitting and infrared detection devices and the primary lens is rendered a flexible dimension, dependent only upon the particular appliance in which the system is installed. The present invention permits the stand for infrared emitting and infrared detection devices to be eliminated as a result of exchanging a non-imaging transceiver system with the current imaging transceiver system. The present invention further comprises assembling or otherwise combining infrared emitting and infrared detection devices into a single infrared emitting/infrared detection device stack. Finally, the present invention provides a Ir transceiver assembly that has a smaller footprint by backside mounting and/or stacking the discrete devices.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of, and claims priority under 35 U.S.C. §120 from, nonprovisional U.S. patent application Ser. No. 09/285,608, filed on Apr. 2, 1999, now abandoned, the subject matter of which is incorporated herein by reference. Application Ser. No. 09/285,608 is a continuation-in-part of, and claims priority under 35 U.S.C. §120 from, nonprovisional U.S. patent application Ser. No. 09/113,036 filed on Jul. 9, 1998, now U.S. Pat. No. 6,281,999, the subject matter of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to infrared communications systems and, more specifically, to an Improved Circuit Design and Optics System for Infrared Signal Transceivers. 
     2. Description of Related Art 
     As technology becomes continually more accessible to the “common man,” the ability to use, store, transfer and otherwise manipulate information has become the focus of most businesses as well as for the individual consumer. Access to the information resources is commonly by some sort of network system, including World Wide Web, “Intranets”, local area networks, wide area networks, as well as corporate databases. 
     While the conventional method for connecting to one of these information networks has been via cable and wire, as the reliance upon connectivity to information has deepened, the desire to gain such access from mobile or portable devices has strengthened. These portable devices, such as Personal Digital Assistants, handheld computers, and even cellular telephones are now being connected to each other and to networks via Infrared Data Communications. In fact, it is virtually impossible to purchase a notebook computer today that does not include an Infrared Data Communications assembly resident within it. 
       FIG. 1  depicts the typical infrared data communications hardware that is installed in electronic devices; it is a perspective view of a prior infrared transceiver assembly  10 . As discussed above, these assemblies  10  are found in virtually every notebook computer sold today. The components of the assembly  10  are virtually identical across all manufacturers&#39; product lines, with few exceptions. The typical assembly  10  comprises a housing  12  within which the infrared emitting device and infrared detection device (see  FIG. 2 ) are mounted. The “transceiver” is actually data processing circuitry for managing the infrared emitting device and infrared detection device; its location is therefore not optically-dependent (and, in fact, it operates better in “IR darkness”). The housing  12  usually is molded from plastic, with a primary lens unit  14  formed in one of the sides of the housing  12 . As can be seen, the conventional primary lens unit  14  comprises two lenses; one each for the infrared emitting device and infrared detection device (both lenses with similar optical properties, and both requiring precision and reproducibility). Adjacent to the housing  12 , is a protective lens  16 . The protective lens  16  is generally constructed from a colored plastic that is transparent to infrared signals. In most cases, the protective lens  16  is attached to the external case of the electronic device, its purpose being to protect the inner workings of the device, while also permitting infrared signals to pass in and out.  FIG. 3  gives further detail regarding the workings of the prior assembly  10 . 
       FIG. 2  is a cutaway side view of the prior infrared transceiver assembly  10  of  FIG. 1 . As can be seen, the housing  12  is generally attached to the “motherboard”  18  or other printed circuit board within the electronic device. Within the housing  12  is located an infrared emitting/infrared detection device pair  20 . It should be understood that it is also common to place more than a single infrared emitting device and/or infrared detection device inside of one housing  12  (e.g. two infrared emitting devices and one infrared detection device, etc.); an infrared emitting device and infrared detection device pair  20  is used here simply in the interest of brevity. 
     The infrared emitting device and infrared detection device pair  20  transmit and receive infrared signals. The infrared emitting device and infrared detection device pair  20  is typically mounted to a stand  22 , and thereby positioned in the signal path of the primary lens  14  in order to send and receive infrared signals therethrough. As discussed earlier, the appliance case  24  has an aperture  25  formed therein, and into which a protective lens  16  is installed. The protective lens  16  simply protects the inner workings of the appliance from contamination. 
     This prior assembly  10  has several deficiencies. First, the protrusion of the primary lens unit  14  can make the housing  12  difficult to grasp by humans and/or machines assembling the electronic devices. The difficulty in grasping can result in manufacturing defects, production delays, and generally higher costs of production. What is needed is a primary lens unit design that does not present a grasping difficulty to assemblers. 
     Second, the primary lens unit  14  mandates higher manufacturing and design standards than the average plastic housing for an electronic device to insure that the light-refractive traits of the primary lens  14  are predictable and repeatable. Because the primary lens unit  14  is integral to the housing  12 , the entire housing  12  becomes subject to the elevated quality standards. It would be much more cost-effective if the design of the integral primary lens unit  14  did not mandate elevated quality standards for the entire housing  12 . 
     Other defects with the prior assembly  10  are illustrated by  FIG. 3 .  FIG. 3  is a cutaway side view of the transceiver assembly  10  of  FIGS. 1 and 2 , depicting the typical transmit dispersion angle θ T  of the assembly  10 . By current IrDA (Infrared Data Association) standards, the transmit dispersion angle θ T  must be at least 15 (fifteen) degrees from the focal axis  26  (in two dimensions, of course). The transmit dispersion angle θ T  is the sum-total of the primary lens refraction angle θ 1  and the protective lens refraction angle θ 2 . All prior assemblies  10  include a protective lens  16  that has no refractive power; the protective lens  10  refraction angle θ 2  is, therefore, typically 0 degrees. Consequently, the conventional primary lens unit refraction angle θ 1  is 15 (fifteen) degrees. 
     There are several design implications resulting from having the entire transmit dispersion angle θ T  provided by the primary lens unit  14 . The infrared emitting device and infrared detection device pair  20  must be located at the focal point  30  of the primary lens unit  14  in order to insure that no signal data is lost. As such, the height  28  (as well as horizontal placement) of the infrared emitting device and infrared detection device pair  20  is very specifically defined. Moreover, the stand (see  FIG. 2 ) must be included in order to raise the infrared emitting device/infrared detection device pair  20  above the printed circuit board  18 . It would be a better arrangement if the infrared emitting device/infrared detection device pair  20  could be mounted directly to the printed circuit board  18 . Furthermore, the separation  32  between the primary lens unit  14  and the protective lens  16  is very critical. Unless the primary lens unit  14  is very close to the protective lens  16 , the protective lens  16  must be relatively large or else the mandated angular dispersion will not be met. A large protective lens  16  can be a serious design constraint for the smaller electronic devices, where component real estate is very tight. What would be better is a design that permits the protective lens  16  to be very small, allows the lens separation distance  32  to be flexible, and still meets the IrDA angular dispersion requirements. 
     Another problem exists in regard to the conventional design for IF infrared transceiver assemblies. As can be seen from  FIG. 9 , which depicts the infrared transceiver assembly  10  of  FIGS. 1 and 2 , the infrared transceiver assembly  10  comprises a housing  12  within which is found a PC board  18 . It is understood that the PC board in some cases might be replaced with a lead frame. The PC board generally has a front side  68  and a back side  70 ; the housing  12  is typically formed with an infrared detection device lens element  14 A and an infrared emitting device lens element  14 B (which together comprise primary lens element  14  described above in connection with  FIG. 1 ). Mounted on the PC board  18  and in the optical path of the infrared detection device lens element  14 A is a conventionally infrared detection device  64 . Also mounted on the PC board  18 , and in the optical path of the infrared emitting device lens element  14 B, is an infrared emitting device  62 . Transceiver circuit device  72 , which is typically an integrated circuit device comprising hardware which can send and receive signals from the infrared emitting device  62  and the infrared detection device  64 , respectively, is also attached to the PC board  18 , (geographically located between the infrared detection device  64  and the infrared emitting device  62 ). For the PC board  18  situation, transceiver circuit device  72 , infrared detection device  64  and infrared emitting device  62  are electrically connected to the pc board  18  via connection means  74  which in this case is of the wire bond type conventionally known in the field. A problem with conventional infrared transceiver assemblies  10  is one of real estate. In the package shown in  FIG. 9 , the requirement for separate footprints for the infrared emitting device  62 , the infrared detection device  64  and the transceiver circuit device  72 L mandates that the PC board  18  is wide and further mandates that there be a plurality of lens elements. It would be beneficial if this large combination of footprints could be minimized by reducing the device size of the transceiver assembly and potentially the cost, among other advantages. 
     SUMMARY OF THE INVENTION 
     In light of the aforementioned problems associated with the prior devices, it is an object of the present invention to provide an improved circuit design and optics system for infrared signal transceivers. It is a further object that the improved system include an infrared transceiver assembly that is easily grasped by assemblers. It is also an object that the primary and secondary lenses associated with the transceiver system be easier to manufacture than current lens designs. It is a still further object that the heretofore critical lens separation between the infrared emitting and infrared detection devices and the primary lens become a flexible dimension, dependent only upon the particular appliance in which the system is installed. It is another object that the stand for infrared emitting and infrared detection devices be eliminated as a result of exchanging a non-imaging transceiver system with the current imaging transceiver system. Finally, it is an object that infrared emitting and infrared detection devices be assembled or otherwise combined into a single infrared emitting/infrared detection device stack. A further object of the present invention is to provide and improved the infrared transceiver assembly that has much smaller outside dimensions than the current state of the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The objects and features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages, may best be understood by reference to the following description, taken in connection with the accompanying drawings, wherein: 
         FIG. 1  (prior art) is a perspective view of a prior art infrared transceiver assembly; 
         FIG. 2  (prior art) is a cutaway side view of the prior art infrared transceiver assembly of  FIG. 1 ; 
         FIG. 3  is a cutaway side view of the transceiver assembly of  FIGS. 1 and 2 , depicting the typical transmit dispersion angle; 
         FIG. 4  is a cutaway side view of a preferred embodiment of the improved transceiver assembly of the present invention; 
         FIG. 5  is a cutaway side view of another preferred embodiment of the improved transceiver assembly of the present invention; 
         FIG. 6  is a partial cutaway side view of yet another preferred feature of the improved transceiver assembly of the present invention; 
         FIG. 7  is a partial perspective view of still another preferred embodiment of the present invention; 
         FIG. 8  is a partial cutaway side view of an integrated infrared emitting infrared detection device stack of the present invention; 
         FIG. 9  (prior art) is a cutaway top view of a conventional infrared transceiver assembly depicted in  FIG. 1 ; 
         FIG. 10  is a cutaway top view of the improved infrared transceiver assembly of the present invention depicting a backside-mounted transceiver circuit device; 
         FIG. 11  is a cutaway top view of another improved infrared transceiver assembly depicting another backside-mounted transceiver circuit devices; 
         FIG. 12  is a cutaway top view of yet another improved infrared transceiver assembly depicting an integrated infrared emitting infrared detection device and a backside mounted transceiver circuit device; 
         FIG. 13  is a cutaway top view of another improved infrared transceiver assembly also employing the integrated infrared emitting infrared detection device of the present invention and another example of a backside-mounted transceiver circuit device; and 
         FIG. 14  is a cutaway top view of still another improved infrared transceiver assembly using a front side-mounted transceiver/infrared emitting infrared detection device stack. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description is provided to enable any person skilled in the art to make and use the invention and sets forth the best modes contemplated by the inventors of carrying out their invention. Various modifications, however, will remain readily apparent to those skilled in the art, since the generic principles of the present invention have been defined herein specifically to provide an Improved Optics System for Infrared Signal Transceivers. 
     The present invention can best be understood by initial consideration of  FIG. 4 .  FIG. 4  is a cutaway side view of a preferred embodiment of the improved transceiver assembly  34  of the present invention. Similar to the prior assemblies, this improved assembly comprises a housing  36  and a secondary lens  40 , which are separated by a distance  38 . What is unique about this particular assembly  34  is the optical characteristics of the secondary lens  40 . Instead of simply being a protective cover for the electronics, this secondary lens  40  also has refractive characteristics. As such, the transmit dispersion angle θ TA  of this preferred assembly  34  is equal to the primary lens unit refraction angle θ 1A  plus the additional secondary lens refraction angle θ 2A . In this new arrangement, therefore, a much wider field of transmission is possible, because the transmit dispersion angle OTA can be increased to well beyond the standard fifteen degrees. Furthermore, the secondary lens  40  can be exchangeable with other secondary lenses having different optical characteristics. In this manner, a limitless variety of dispersion angles θ TA  can be achieved for a single piece of equipment. 
     Now turning to  FIG. 5 , we might further explore the implications and benefits of the new design.  FIG. 5  is a cutaway side view of another preferred embodiment of the improved transceiver assembly  42  of the present invention. Similar to the assembly  34  of  FIG. 4 , this assembly  42  comprises a secondary lens  40  that has refractive power. In this present embodiment, however, the primary lens unit  46  has no refractive power (i.e. θ 1B =0 degrees). As such, the entire transmit dispersion angle θ TB  is determined by the contributions from the secondary lens  40 ; no redirection of the light occurs as it passes through the primary lens unit  46 . 
     Because there is no redirection of the light by the primary lens unit  46 , the lens separation distance  52  ceases to be determined by the size of the aperture (see  FIG. 2 ) and secondary lens  40 . This provides a significant advantage over the prior assemblies because the housing  44  can be placed in a location on the PC board that is convenient to the PC board layout, without the concern for its distance from the case (and the secondary lens  40 ). 
     Furthermore, there are other benefits to this new design. Since there is no focussing of the light by the primary lens unit  46 , there is no focal point for the light. The conventional infrared emitting device/infrared detection device pair  20  can be replaced with “non-imaging” infrared emitting device/infrared detection device pair  50  that is not dependent upon a focal point. “Non-imaging” infrared detection devices simply detect any (and all) incident infrared light—they are commonly less expensive than the “imaging” infrared detection devices in use by conventional IR transceiver assemblies. The incident (and transmitted) light may simply be redirected by a mirror  48  and down to (or out from) the infrared emitting device/infrared detection device pair  50 . Because there is no longer a focal point to deal with, the location of the infrared emitting device/infrared detection device pair  50  is very flexible. In fact, it would be natural to mount the infrared emitting device/infrared detection device pair  50  directly onto the PC board, with the infrared emitting device/infrared detection device height  28  being effectively zero. This means that the infrared emitting device/infrared detection device pair  50  can be mounted easily by conventional PC board assembly processes—the housing might actually be added on later. Consequently, the manufacturing costs attributable to the IR transceiver assembly  42  are substantially reduced. 
     In another series of embodiments, there may be different dispersion angles for different regions of the secondary lens  56 . An example is provided in  FIG. 6 , which is a partial cutaway side view of yet another preferred embodiment of the improved transceiver assembly  54  of the present invention. In this Figure, the transmit dispersion angle θ TC  is equal to the total of the secondary lens upper region refraction angle θ 2C  and the secondary lens lower region refraction angle φ 2C . As can be seen, these two regions have different refracting characteristics. It should be appreciated that a virtually limitless set of combinations of different refracting regions may be desired.  FIG. 7  is a partial perspective view of still another preferred embodiment of the infrared transceiver assembly  58  of the present invention. In this embodiment, the secondary lens  60  is divided into four regions, each having unique refractive characteristics, as indicated by the upper left refraction angle θ 2DL , the upper right refraction angle θ 2DR , the lower left refraction angle φ 2DL , and the lower right refraction angle φ 2DR . Again, it should be apparent that this is simply one design example; a wide variety of regions and refraction characteristics is expected. 
     It is also possible that a secondary lens employing shiftable and/or variable refracting regions is currently available, such as via Liquid Crystal technology. Furthermore, the secondary lens might be configured to mask out certain regions by being selectively opaque to infrared signal transmission. Each of these features is a significant advancement over the prior devices. 
     Another significant advancement of the present invention involves assembling or otherwise combining the infrared emitting device/infrared detection device pair into a single, integrated infrared emitting/infrared detection device stack  66 , as depicted by  FIG. 8 . The infrared emitting device is much smaller than the infrared detection device (0.3 mm 2  vs. 1.8 mm conventionally); furthermore, the infrared emitting device circuitry is conventionally built upon a transparent substrate. It is an aspect of the present invention that the infrared emitting device  62  be placed directly on top of the infrared detection device  64  (i.e. in the path of incident and exiting IR signals) to form an integrated infrared emitting/infrared detection device stack  66 . This was very difficult under prior transceiver assembly designs, because the infrared emitting device and infrared detection device would most likely have different focal points. Under the improvement described previously herein, however, the focal point of the primary lens unit is no longer an issue. 
     Now turning to  FIG. 10 , we can take a look at another embodiment of the present invention.  FIG. 10  is a cutaway top view of the improved infrared transceiver assembly  76  of the present invention depicting a backside-mounted transceiver circuit device  72 . Similar to  FIG. 9 , the device of  FIG. 10  has a PC board  18  having a front side  68  and a backside  70 . Also, this transceiver assembly  76  includes an infrared detection device lens element  14 A and an infrared emitting device lens element  14 B located to the front side  68  of the PC board  18  and electrically connected through connection means  74 . What is unique about this present embodiment is that the transceiver circuit device  72  is actually located on the backside  70  of the PC board  18 . In this case, the transceiver circuit device  72  is electrically connected to the PC board  18  via alternate connection means  78 , which in this case comprises “bump” attachment (a common device soldering method). As can be seen from  10  the improved assembly  76  of  FIG. 10 , since the transceiver circuit device  72  is no longer located between the infrared detection device lens element  14 A and the infrared emitting device lens element  14 B, the width of PC board  18  and therefore the size of the housing  12  is much narrower, allowing the assembly  76  to be much smaller in size. 
     If we now turn to  FIG. 11 , we can see yet another embodiment of an improved infrared transceiver assembly  80 .  FIG. 11  is a cutaway top view of another improved infrared transceiver assembly depicting another backside-mounted transceiver circuit device  72 . In  FIG. 11 , the base structure is a lead frame  82 . A lead frame, like the PC board of the previous figures, is a common device mounting structure in the semi-conductor and electronics industry. The lead frame  82  has a back side  84  and a front side  86 , just as with the PC board  18 . In the transceiver assembly  80  of this preferred embodiment, the infrared detection device  64  and infrared emitting device  62  are both attached to the front side of the lead frame  86 , however in this case, the transceiver circuit device  72  is attached to the backside of the lead frame  84 , through the conventional connection means  74 , comprising typical wire bond interconnection for electrical conductance. Just as with assembly  76  in  FIG. 10 , this embodiment  80  provides the advantage of a reduced package size, as well as providing at least two mounting and connection options for the transceiver circuit device  72 . 
       FIG. 12  depicts yet another improved infrared transceiver assembly  88  of the present invention.  FIG. 12  is a cutaway top view of yet another improved infrared transceiver assembly  88  depicting an integrated infrared emitting/infrared detection device stack  66  and a backside-mounted transceiver circuit device  72 . In this embodiment, the integrated infrared  10  emitting/infrared detection device stack  66  is employed on the front side of the PC board  68  and connected thereto via connection means  74 . Since the infrared emitting/infrared detection device stack  66  is integrated, the need for two lens elements is eliminated, resulting in a single primary lens element  14 C. Furthermore, the transceiver circuit device  72  is attached to the backside of the PC board  70 , just as described above in connection with  FIG. 10 . As can be appreciated, this preferred embodiment of the transceiver assembly  88  provides even further package size reduction over the previous units. 
     Similarly,  FIG. 13  depicts the integrated infrared emitting/infrared detection device stack  66  attached to the lead frame&#39;s front side  86  with the transceiver circuit device  72  being attached to the backside of the lead frame  84 .  FIG. 13  is a cutaway top view of another improved infrared transceiver assembly  89  also employing the integrated infrared emitting/infrared detection device stack  66  of the present invention and another example of a backside-mounted transceiver circuit device  72 . Again, like the assembly  88  of  FIG. 12 , this present embodiment of an improved infrared transceiver assembly  89  provides significant benefits in package size reduction. 
     Finally, we will turn to  FIG. 14  to examine yet another preferred embodiment of an improved infrared transceiver assembly  90 .  FIG. 14  is a cutaway top view of still another improved infrared transceiver assembly  90  having a front side-mounted transceiver/infrared emitting/infrared detection device stack. This assembly  90  provides the smallest package size yet. In this case, the integrated infrared emitting/infrared detection device stack  66  and the transceiver circuit device  72  are stacked together in a transceiver/infrared emitting/infrared detection device stack  96 . Since the infrared emitting/infrared detection device stack  66  and the transceiver circuit device  72  are stacked, all devices can be attached to the front side of the circuit structure  94 . As can be appreciated, the circuit structure  92  might comprise a PC board or a lead frame or other conventional structural circuit-providing devices conventional in the art. It should be understood from this view that since all of the devices are attached to the front side of the circuit structure  94 , the housing  12  is not only reduced in width, but is also thinner in depth than those improvements previously described in connection with  FIGS. 10 through 13 . In other embodiments, there might be multiple infrared emitting/infrared detection device stacks  66  spread out over the face of a single transceiver circuit device  72 , which is then attached to the front side of the circuit structure  94 . Furthermore, and as discussed previously in connection with  FIGS. 3 through 8 , while a single primary lens element  14 C is shown here, this improved infrared transceiver assembly  90  might also include an embodiment where there is a primary lens element  14 C as well as a secondary lens element  40 . Still further, the embodiment is conceived where in a single device, the transceiver circuitry as well as the infrared emitting device and infrared detection device circuitry are combined such that a single set of connection means  74  attaches this integrated device to the circuit structure front side  94 . 
     Those skilled in the art will appreciate that various adaptations and modifications of the just-described preferred embodiment can be configured without departing from the scope and spirit of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.