Abstract:
An apparatus and method for acquiring an image of a patterned object such as a fingerprint including a light refracting device, a focusing lens, a light source, and a biometric circuit for detecting the presence of a patterned object such as a fingerprint at the light refracting device. Incident light from the light source is projected through a light receiving surface of the light refracting device and is directly reflected off an imaging surface. The resulting image is projected through the focusing lens. The focusing lens has a diameter which is larger than the projection of the patterned object through the light refracting device.

Description:
This application claims benefit under 35 U.S.C. §119(e) of U.S. Provisional Application Ser. No. 60/095,525 filed Aug. 6, 1998. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention generally relates to fingerprint capturing and recognition systems. More specifically, the present invention relates to compact optical fingerprint capturing and recognition systems. 
   2. Description of the Related Art 
     FIG. 1  shows a schematic diagram of an earlier optical fingerprint capturing and recognition system. In  FIG. 1 , an optical recognition system  100  includes an illuminating light source  105 , an optical prism  110 , a lens assembly  115 , an image sensor  120 , and a storage and processing unit  125 . The illuminating light source  105 , which may, for example, be a light emitting diode (LED), generates a light ray that is transmitted to the optical prism  110 . The optical prism  110  has an apex angle θ that is approximately 45 degrees. In an optical fingerprint capturing and recognition system, the apex angle is defined as the angle opposite to the incident surface of the optical prism, i.e., the surface of the prism that receives light from the light source. When there is no fingerprint or other object placed on the optical prism&#39;s fingerprinting surface  111 , light entering the optical prism  110  from the illuminating light source  105  undergoes total internal reflection at the fingerprinting surface  111  if the incidence angle of the incoming light exceeds the critical angle of the optical prism  110 . However, when there is a fingerprint or other object, such as object  112 , touching the upper surface  111 , then there is some scattering and/or absorption of the light incident on the point of contact between the object  112  and the fingerprinting surface  111 . As a result of the scattering and/or absorption, there is less than total internal reflection of the incident light beam at points on the exterior surface that are in contact with object  112 . Consequently, the reflected light beam at such contact points are weaker. Weaker light beams eventually translate into darker points to indicate the presence of an object at the point of incidence between the light beam and the fingerprinting surface  111 . Conversely, stronger reflected light beams, such as those that undergo total internal reflection, translate into brighter points to indicate the absence of an object at the point of incidence between the light beam and the fingerprinting surface  112 . This allows distinguishing the darker fingerprint ridge points from the lighter fingerprint valley points. Light beams reflected from the fingerprinting surface  111 , both totally internally reflected light beams and partially internally reflected light beams, are transmitted in the direction of the lens assembly  115 , which may contain one or more optical lenses. Thereafter, light beams from the lens assembly  115  are captured by the image sensor  120 . Image sensor  120 , which may, for example, be a charge coupled device (CCD), captures optical light images and converts them to electrical signals. The electrical signals are then transmitted to the storage and processing unit  125 . Storing and processing unit  125  may include a memory unit, a processor and an analog to digital converter. The analog to digital converter converts the analog electrical signals from the image sensor  120  into digital data. The memory is used to store the digital data and algorithms for comparing a captured fingerprint image with a stored fingerprint image. The processor compares the captured digital data with data previously stored in memory based on an algorithm for comparing such data. The processor may also analyze the captured digital data for purposes different from comparison with stored data. 
   The above described system allows capturing an optical fingerprint image and processing the electrical representation of the optical fingerprint image. However, the above system suffers from some severe disadvantages. First, the optical recognition system  100  tends to be relatively large due to the relatively large distance between the optical prism  110  and the lens assembly  115 . The large distance between the optical prism  110  and the lens assembly  115  is dictated by the following problems associated with attempting to capture optical images of an object that is larger than the first lens (i.e., the first lens that receives light rays from the optical prism) in the lens assembly in a system whose optical prism is relatively close to the lens assembly. In systems whose optical prism is relatively close to the lens assembly, when the object is larger than the first lens in the lens assembly, points near the ends of the object are not captured by the system. Moreover, the optical path of the light rays incident on the first lens in the lens assembly are not parallel to the optical axis of the first lens. Light paths that are not parallel to the optical axis are not well defined and generate greater uncertainty in determining the optical paths in the system. Thus, the large distance between the optical prism  110  and the lens assembly  115  is required in the above mentioned system in order to (1) help capture optical images near the ends of an object that is larger than first lens in lens assembly  115  and (2) make the optical paths of light rays from the optical prism  110  to the lens assembly  115  approximately parallel to the optical axis of the first lens in the lens assembly  115 . Second, such systems can suffer from significant image distortions. 
   To overcome the disadvantage of large distortions in the captured images with respect to the object images, some fingerprint capturing and recognition systems, such as that disclosed in Korean Patent Number 94-7344, use an optical prism with an apex angle θ greater than 45 degrees.  FIG. 2  shows the optical assembly  200  using an optical prism having an apex angle greater than 45 degrees. In the system used by Korean Patent Number 94-7344, which is herein incorporated by reference, the apex angle θ is determined by the following equation:
 
sin(θ)/ n ≅sin( b )sin( c )  equation (1)
         where θ is the apex angle;   n is the refractive index of the optical prism  210 ;   b is the angle between the fingerprinting surface  211  (also known as the imaging surface) and the light reflected from it;   c is the angle between the light escaping the optical prism  210 , at the image collecting surface  214 , and the image collecting surface  214  (also known as the prism surface).       

   Optical assembly  200  comprises an optical prism  210 , a lens assembly  215  and an image sensor  220 . The optical assembly  200  also suffers from some disadvantages of earlier optical structures. 
   First, there is the problem of image distortion because non-parallel light rays are transmitted from the object to the lens assembly  215 . As a result, even when angle θ a  is equal to angle θ β , the ratio of length AB to EF is not equal to the ratio of length BC to DE. This is an indication of the presence of distortion in the optical assembly due to the optical prism  210 . More generally, the ratio of lengths of AB to PQ is not equal to the ratio of lengths of BC to PO, indicating the presence of distortion in the optical assembly  200 . Second, there is some image loss in the system when lens assembly  215  is not placed sufficiently far away from the optical prism  210  so as to make the optical paths essentially parallel to the optical axis of the first lens in lens assembly  215 . 
   In the system of  FIG. 2 , since the lens is smaller than the projection of the object through the optical prism, not only parallel light reflected from the object, such as a fingerprint, is employed to produce an image of the object. Therefore, some non parallel light reflected from the object is used in such a system. As a result of using non-parallel light reflected from the object, the lens is typically located at a relatively long distance from the object in order to approximate the condition of total internal reflection. Otherwise, if the lens is close enough to the optical prism such that a condition approximating total internal reflection is not met, then some of the light rays from the object will be lost and will not be captured by the sensor. 
   As the optical assembly  200  also may suffer from the problem of image loss when the optical prism is relatively close to the lens assembly, the lens assembly is placed such that the optical prism is relatively far from the lens assembly in order to capture the entire fingerprint. This causes the fingerprint capturing and recognition systems using the optical assembly of  FIG. 2  to be relatively large due to the required relatively large distance between the optical prism and the lens assembly. 
   As the lens system in  FIG. 2  has a finite entrance pupil, the problems associated with the optical assembly  200  may succinctly be explained as those associated with lens systems using a finite entrance pupil. In an optical fingerprint capturing and recognition system, a first lens diameter that is not larger than the projection of the fingerprint through the optical prism is characteristic of a lens assembly having a finite entrance pupil. The first lens diameter is the diameter of the first lens in the lens assembly, i.e., the first lens in the lens assembly that receives an optical image of the object through the optical prism.  FIG. 3  shows a conventional lens system with a finite entrance lens. As shown in  FIG. 3 , the optical paths are finite light paths that are not parallel to the optical axis of the object lens. 
   Other earlier systems have used holographic techniques to deal with the problems of distorted images. Holographic systems typically use a polarizer and a scanning line guide to reduce distortion in images and to provide optical parallelism between the plane of the fingerprint image and the image capturing surface. However, these systems ordinarily require expensive and complex optical components. Moreover, holograms generally require nearly perfect data about the object whose image needs to be captured. As a result, such a system requires complementary optical systems to make up for the likely shortages in fingerprint data. The complexity of the system in addition to the need for complementary optical systems makes the fingerprint capturing and recognition system using holographic techniques large and complex, both in terms of hardware and software. 
   Thus, there has been a need for an optical fingerprint capturing and recognition system that uses an optical structure with which the entire image of an object may be captured without distortion when the distance between the lens assembly and the optical prism is too small to approximate the condition of total internal reflection. In other words, there has been a need for a compact optical structure that can capture the entire image of an object, such as a fingerprint, without distortion. 
   SUMMARY OF THE INVENTION 
   The present invention overcomes the aforementioned disadvantages by using an optical fingerprint recognition system comprising an optical prism with an apex angle larger than 45 degrees and a lens assembly with a relatively large first lens. An apparatus for forming an image of a patterned object according to the present invention includes a light refractor such as a prism, at least one focusing lens, and at least one light source. The light refractor has an imaging surface against which a patterned object is to be placed, at least one light entrance surface adjacent to the imaging surface through which light enters the refractor, and a viewing surface through which an image of the object to be imaged is projected. The focusing lens is adjacent to the viewing surface and receives and focuses an image of the patterned object projected through the viewing surface. The focusing lens has a diameter that is larger than a projection of the patterned object through the light refractor. The light source is located adjacent to the light receiving surface and emits incident light which enters the light refractor to create an image of the patterned object. The light source defines a light source plane. The light source is positioned such that substantially all light emitted from the light source in a direction substantially parallel to the light source plane directly strikes the imaging surface of the light refractor. The apparatus can also include a biometric circuit having at least one contact located adjacent to the imaging surface. The biometric circuit is for detecting the presence of a finger touching the contact. 
   Because the focusing lens is larger than a projection of the object through the light refractor, the focusing lens can be placed relatively close to the viewing surface without losing a portion of the image near the edges of the image. This advantageously allows the image forming apparatus to be relatively compact because the focusing lens does not have to be placed a relatively large distance from the viewing surface. Additionally, by configuring the light source such that substantially all the light emitted in a direction perpendicular to a light source plane directly strikes the imaging surface (that is, the light does not first strike another surface), the amount of stray, reflected light in the light refractor is reduced. This advantageously reduces background or “noise” light in the light refractor that might cause degradation of an image by reducing the contrast of the image. Further, by including a biometric circuit which detects the presence of a live finger at the imaging surface, the likelihood that the imaging apparatus will be fooled by a replica of a fingerprint is advantageously reduced. 
   In another aspect of the present invention, a fingerprint imaging apparatus includes an imaging surface against which a fingerprint to be imaged is to be placed. The imaging apparatus also includes a biometric circuit for detecting the presence of the fingerprint to be imaged by the imaging apparatus. The biometric circuit has at least one electrical contact adjacent to the imaging surface and against which a finger, which acts as an ac signal source, can be placed. The biometric circuit also includes a charging circuit connected with the electrical contact. The charging circuit charges in response to the ac signal sourced from the finger placed against the electrical contact. A switching circuit which is electrically connected with the charging circuit is responsive to the charging circuit to indicate the presence of a finger at the imaging surface. 
   In another embodiment, the biometric circuit of the fingerprint imaging apparatus includes at least two electrical contacts adjacent to the imaging surface and against which a finger, which acts as an electrical resistance, can be placed to create an electrical connection between the contacts. A voltage supply is electrically connected to at least one of the contacts. A switching circuit is electrically connected to at least one of the electrical contacts and the voltage supply. The switching circuit is responsive to a reduction in voltage from the voltage supply caused by an electrical resistance placed between the contacts to detect the presence of a finger on the contacts. 
   Each of the above two described embodiments of a fingerprint imaging apparatus having a biometric circuit are advantageously relatively simple, can be made relatively compact, require relatively little circuitry, and do not require an ac signal source internal to the biometric circuit. 
   The present invention also encompasses a pointing device, such as a cursor pointing device including a computer mouse, a track ball, a touch pad or a joy stick, comprising the optical structure of the fingerprint capturing and recognition system of the present invention. In a presently preferred embodiment, the pointing device of the invention includes both a horizontal guide and a vertical guide for aligning a finger whose fingerprint image is to be taken to be properly aligned with the optical prism of the optical structure. Additionally, the pointing device includes a serial port connector for transmitting data representing a capture image of a fingerprint from an optical structure to a computer to which the pointing device is coupled and a conventional pointing device port connector for transferring power and other signals between a pointing device and a computer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram of one prior art optical capturing and recognition system. 
       FIG. 2  is a schematic diagram of an optical assembly of another prior art optical capturing and recognition system. 
       FIG. 3  is a schematic diagram of a lens system with a finite entrance pupil such as that of the optical assembly of FIG.  2 . 
       FIG. 4  is a schematic diagram of the optical structure of the optical fingerprint capturing and recognition system of the present invention. 
       FIG. 5  is a schematic diagram of a lens system with an infinite entrance pupil of the present invention such as that of the optical structure of FIG.  4 . 
       FIG. 6  is a circuit diagram of one embodiment of the biometric sensing circuit of the present invention. 
       FIG. 7  is a circuit diagram of another embodiment of the biometric sensing circuit of the present invention. 
       FIG. 8  is a top view of a computer mouse of the present invention with a serial port connector and a conventional computer mouse connector. 
       FIG. 9  is a side perspective view of the computer mouse of the present invention. 
       FIG. 10  is a side view of the computer mouse of the present invention. 
       FIG. 11  is a top view of the computer mouse of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 4  is a schematic diagram of the optical structure of the optical fingerprint capturing and recognition system of the present embodiment of the invention. The optical structure  300  comprises an illuminating light source  305 , an optical prism  310 , an object lens assembly  315 , an eyepiece lens assembly  316 , and an image sensor  320 . 
   Illuminating light source  305  is a plane light source, such as an LED array. As incident surface  313  of optical prism  310  is translucent, it uniformly disperses the incoming light received from illuminating light source  305  such that optical prism  310  receives light of uniform intensity from incident surface  313 . The incident surface  313  may be made translucent by sand papering or other means known to those skilled in the art. In one alternative embodiment, a translucent layer may be placed between the illuminating light source  305  and the optical prism  310 . In yet another embodiment, illuminating light source  305  may be a uniform light source. 
   Optical prism  310  has an apex angle θ that is determined by using equation (1) disclosed in the Background of the Invention, is greater than 45 degrees and is preferably between 52 and 72 degrees. Fingerprinting surface  311  is laminated or coated with polyethylene, polypropylene or polyethylene terephthalate (PET) treated with a surfactant to improve scattering of light impinging on the fingerprint surface  311  and to provide better contact between the imaged object  312  (i.e., a finger, and more specifically the ridges on the fingerprint) and the fingerprinting surface  311 . The treatment with surfactant provides the improved contact between the finger  312  and the fingerprinting surface  311 . The incoming light in the optical prism  310  undergoes reflection/absorption at the internal side of fingerprint surface  312 . Some light is absorbed or scattered at points of contact between the fingerprint ridges and the fingerprint surface  312 . As a result, dark line images are captured representing the fingerprint ridges in a bright background representing the fingerprint valleys or other points where there is no contact between the finger and the fingerprinting surface  311 . Points where there is no contact between the finger and the fingerprinting surface  311  are represented by bright images because light at those points is totally internally reflected. Alternatively, a polyurethane or other flexible material layer may be used on the fingerprinting surface to improve scattering as is known in the art. Similarly, as is known in the art, a viscous oily liquid may be used on the fingerprinting surface to improve contact between the fingerprint and the fingerprinting surface. 
   Object lens assembly  315  may include one or more lenses. The first lens in object lens assembly  315 , i.e., the first lens which receives light rays from the optical prism  310 , has a diameter that is larger than the projection of the fingerprint through the optical prism  310  or is larger than the diagonal line segment connecting diagonally opposed corners of the smallest rectangle that completely encompasses the fingerprint whose image is to be captured. A first lens diameter that is larger than the projection of the fingerprint through the optical prism is characteristic of a lens assembly having an infinite entrance pupil. The first lens diameter is the diameter of the first lens in the lens assembly, i.e., the first lens in the lens assembly that receives an optical image of the object through the optical prism. A first lens with a large diameter as defined above allows placing the lens in close physical proximity to the optical prism  310  without losing light rays representative of the image of the fingerprint. The close proximity between the optical prism  310  and the first lens of the object lens assembly  315  reduces the overall size of the optical structure of the optical fingerprint capturing system. Thus, using a large lens, as defined above, allows reducing the size of the optical system. Similarly, using lenses having relatively small focal lengths allows placing the image sensor  320  closer to the object lens assembly  315  while capturing the entire image of the fingerprint. As explained further below, the reduced size of the optical structure enables one to place the optical structure in a small device, such as a computer mouse or keyboard, a door or other type of locking system. The optical structure can also be placed in an automatic teller machine (ATM). Additionally the first lens is tilted away from the apex angle in order to reduce or eliminate the optical path difference between light rays reflected from different points of the target area that whose fingerprints are to be captured by the optical fingerprinting system so as to eliminate distortion. Light rays from the first lens are then passed to other lenses within the object lens assembly  315  and are eventually transmitted to the eyepiece lens assembly  316 , which may include one or more lenses. Eyepiece lens assembly  316  focuses light rays received from the object lens assembly  315  onto the surface of the image sensor  320 . 
   In a presently preferred embodiment, image sensor  320  is a complementary metal-oxide-semiconductor (CMOS) sensor. Image sensor  320  receives light rays from lens assembly  315  and converts the captured light rays into electrical signals. In a presently preferred embodiment, the image sensor converts the light rays into 4 bit digital data. In other embodiments, the light rays may be converted to 8 bit digital data or some other number of bits. Image sensor  320  may be a CMOS sensor available from OMNI Vision a United States based company, VLSI Vision a United Kingdom based company, Hyundai Electronics a South Korea based company. In another embodiment, image sensor  320  may comprise a CCD which converts the light rays into analog rather than digital signals. The analog signals are then converted to digital signals by an analog to digital converter. The digital data is then transferred to a computer for storage and/or processing. 
   In one embodiment, which is further described below in relation to a computer mouse having a fingerprint image capturing optical structure, the digital data is transferred to a bus controller which then transfers the data on a RS  232  serial bus to the computer. In another embodiment, a universal serial bus (USB) or some other computer interface bus may be used to transfer digital data from the bus controller to the computer. In a preferred embodiment, the image sensor  320 , such as a CMOS sensor, and the bus controller (not shown) are on the same integrated circuit (IC) chip. 
     FIG. 5  is a schematic diagram of a lens system with an infinite entrance pupil in accordance with a present embodiment of the invention such as that of the optical structure of FIG.  4 . In  FIG. 5 , the object lens is larger than the object and parallel light paths from the object are transmitted to the object lens. A lens system with an infinite entrance pupil, such as that shown in  FIG. 5 , allows placing the lens assembly  315  close to the optical prism  310  without losing any part of the image or causing any distortion. 
   In  FIG. 4 , the lens system of optical structure  300  includes the object lens assembly  315  and the eyepiece lens assembly  316  and has an infinite entrance pupil. As the lens system of optical structure  300  has an infinite entrance pupil, the ratio of lengths AB to IH is equal to the ratio of the lengths of BC to HG. It then follows that when length AB is equal to length BC, then length IH will be equal to length HG. Furthermore, θ 1 , θ 2 , and θ 3 , which are shown in  FIG. 4 , are all equal to one another. In other words, θ 1 =θ 2 =θ 3 . As the ratio of lengths AB to IH is equal to the ratio of the lengths of BC to HG and θ 1 =θ 2 =θ 3 , the optical structure  300  of  FIG. 4 , captures complete and distortion-free fingerprint images. 
     FIG. 6  is a circuit diagram of one embodiment of the biometric sensing circuit of a present embodiment of the invention. In biometric sensing circuit  600 , a person touching the electrode  605  acts as an AC signal source. In the positive half of the first AC cycle while a person contacts the electrode  605 , the output of inverter  610  is low and the output of inverter  620  is high. As the output of inverter  620  is high, transistor  650  will not turn on. It is also considered to use any other suitable active electronic component such as a field effect transistor or an operational amplifier in place of transistor  650 . In the negative half of the first AC cycle while a person contacts the electrode  605 , the output of inverter  610  is high and the output of inverter  620  is low. As the output of inverter  620  is low, transistor  650  will turn on and source current to the optical structure  640 , therefore, turning on the optical structure  640 . After a transient period which may be set to shorter than the period for the AC signal induced from the person touching the electrode  605 , the capacitor  630  is charged such that the voltage at the input of inverter  620  remains high both during the positive and negative halves of the AC cycle for as long as the person continues to maintain contact with the electrode  605 . As a result the output of inverter  620  continues to remain low and transistor  650  continues to remain on and source current to the optical structure  640 . When the person stops holding the electrode  605 , capacitor  630  discharges such that the voltage at the input of inverter  620  turns low. As a result the output of the inverter  620  becomes high and the transistor  650  is turned off and stops sourcing current to the optical structure  640  thus causing optical structure  640  to turn off. 
     FIG. 7  is a circuit diagram of an alternative biometric sensing circuit of a present embodiment of the invention. In biometric sensing circuit  700 , a person touching electrodes acts as a resistance. Resistor  760  has a sufficiently large resistance such that the voltage at the input of inverter  710  is low even when a person touches electrodes  705  and  706 . In one embodiment, resistor  760  has a resistance of greater than 10 megaohms and preferably has a resistance greater than 15 megaohms. This is also the case with respect to resistor  660  shown in FIG.  7 . When a person touches resistors  705  and  706 , the voltage at input of inverter  710  will be low and the output of inverter  710  will be high. As the output of the inverter  710  is high the transistor  750  will be turned on and will source current to the optical structure  740 , therefore, turning on the optical structure  740 . It is also considered to use any other suitable active electronic element in place of transistor  750 , such as a field effect transistor or an operational amplifier. When a person discontinues contacting electrodes  705  and  706 , the input of inverter  710  will be high and the output of inverter  710  will be low. When the output of inverter  710  is low, transistor  750  will turn off and discontinue sourcing current to optical structure  740 , therefore, causing optical structure  740  to turn off. 
   The biometric sensors  600  and  700  may be used to prevent the image of a fingerprint instead of an actual fingerprint for accessing a system that uses the fingerprint as a security access key. 
     FIG. 8  is a top view of a computer mouse  810  of a present embodiment of the invention with a serial port connector  820  and a conventional computer mouse connector  830 . In a presently preferred embodiment, computer mouse  810  includes both a horizontal guide  811  and a vertical guide  812  for ensuring that a finger whose fingerprint image is to be taken is properly aligned in the horizontal and vertical directions, respectively, with respect to the fingerprinting surface of the optical prism of the optical structure. In some embodiments of the computer mouse use of only one of the horizontal and vertical guides may be sufficient for aligning the finger with the optical prism. Furthermore, computer mouse  810  includes an optical structure of the present invention such as optical structure  300  used in the optical fingerprint capturing and recognition system of the present invention. The ability to house the optical structure  300  inside computer mouse  810  is due to the relatively small size of optical structure  300 . The relatively small size of optical structure  300  is accomplished by use of a lens system with an infinite entrance pupil which allows placing the lens assembly within close proximity of the optical prism while capturing the image of the entire object and being distortion free. 
   The mouse  810  is coupled to a serial or parallel connector  820  and a conventional computer mouse connector  830 . The serial connector  820  transmits fingerprint capture data from the optical structure to a computer to which the pointing device is coupled. The serial connector  820  is in one embodiment an RS  232  port connector. Since RS  232  lines are relatively slow, they preferably transmit 4 bit data signals, representing 4 bit gray levels, from the computer mouse  810  to the computer (not shown) to which the computer mouse  810  is coupled. It is to be noted that the 4 bit data signals transmitted from the mouse  810  to the RS  232  port connector by way of the RS  232  lines are video data as they represent fingerprint images. Thus, the present invention uses RS  232  lines and RS  232  port connectors to transfer video data. Alternatively, serial connector  820  may be a USB connector. Since USB is a fast bus, it will preferably transmit 8 bit data representing 8 bit gray levels. The conventional mouse port connector transfers power and other signals related to conventional mouse operation, between the computer mouse  810  and a computer (not shown) to which the computer mouse  810  is coupled. The conventional mouse port connector may be a PS/2 port connector. 
     FIG. 9  is a side perspective view of the computer mouse of a present embodiment of the invention. In  FIG. 9 , vertical guide  812  is shown as being near the bottom of the computer mouse  810  (or the fingerprinting surface  880 ). In an alternative embodiment, vertical guide  812  may be located near the top of computer mouse  810  (or the fingerprinting surface  880 ) rather than the bottom as shown in FIG.  9 .  FIG. 9  also shows the fingerprinting surface  880  of the optical prism of the optical structure of the present invention. The optical structure of the present invention captures the optical image of a fingerprint placed against the fingerprint surface  880 . The optical image of the fingerprint may be used as a security access key or password for accessing a computer system, either upon booting the computer or when reentering a computer system from a screen saver. 
     FIG. 10  is a side view of the computer mouse of the present invention. 
     FIG. 11  is a top view of the computer mouse of the present invention. 
   Although the above description has been made in relation to a computer mouse, it is to be noted that the optical structure of the present invention may be used in conjunction with other pointing device, including other cursor pointing devices. For example, the optical structure of the present invention may be used in conjunction with a track ball, a touch pad or a joy stick. More specifically, the optical structure of the present invention may be included inside a track ball, a touch pad, or a joy stick, among other cursor pointing devices. In fact, the optical structure may be incorporated into devices other than pointing devices. For example, the optical structure may be incorporated into telephones, televisions, cars, doors, as well as other items. The fingerprint image may be used as a security access key by the aforementioned items. 
   While the present invention has been particularly described with respect to the illustrated embodiments, it will be appreciated that various alterations, modifications and adaptations may be made based on the present disclosure, and are intended to be within the scope of the present invention. While the invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the present invention is not limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements.