Abstract:
An image alignment device for tandem optics (IAD-TO) is disclosed which provides a standalone means for the operator to align and optimize the imagery produced by dissimilar optical devices to achieve overall system capability gain. The IAD-TO is inserted into the optical path between the optical devices when they are configured for in line use and provides the operator an on-demand capability to compensate for the inherent image shift between them, especially for those optical devices that provide no alignment adjustment mechanisms. Featuring interchangeable adaptor arms and quick action mount interfaces, the IAD-TO can be used with various types of optical devices and can be mounted to a variety of surfaces.

Description:
RELATED U.S. APPLICATION DATA 
       [0001]    Provisional application No. 61/656,247, filed Jun. 6, 2012 
       REFERENCES CITED 
       [0002]      
         [0000]    
       
         
               
             
               
               
               
               
               
             
           
               
                   
               
               
                 U.S. Patent Documents 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 3,359,849 A 
                 December 1967 
                 Friedman 
                 356/153 
               
               
                   
                 4,629,295 A 
                 December 1986 
                 Vogl 
                 350/503 
               
               
                   
                 5,892,617 A 
                 April 1999 
                 Wallace 
                 359/353 
               
               
                   
                 6,111,692 A 
                 August 2000 
                 Sauter 
                 359/429 
               
               
                   
                 6,172,821 B1 
                 January 2001 
                 Isbell et al. 
                 359/809 
               
               
                   
                 6,992,843 B2 
                 November 2006 
                 Juhala 
                 359/819 
               
               
                   
                 7,142,357 B2 
                 November 2006 
                 Greenslade 
                 359/353 
               
               
                   
                 7,359,114 B2 
                 April 2008 
                 Sauter et al. 
                 359/353 
               
               
                   
                 8,094,309 B1 
                 January 2012 
                 Pochapsky 
                 356/399 
               
               
                   
                   
               
             
          
         
       
     
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0003]    Not applicable 
       REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX 
       [0004]    Not applicable 
       BACKGROUND OF THE INVENTION 
       [0005]    1. Technical Field 
         [0006]    The present invention is in the technical field of optical systems. More particularly, the present invention is in the technical field of alignment tools for optical systems. 
         [0007]    2. Background Art 
         [0008]    Optical devices exist in many different forms and exhibit various operational and physical characteristics suited to their specific purposes. These characteristics may not be shared by other optical devices. Therefore, it is desirable at times to utilize more than one optical device simultaneously in order to realize the combined benefits provided by the devices, and thereby achieve an overall capabilities gain. 
         [0009]    For example, a day-vision optical system, referred to hereinafter as “day optic,” may have characteristics such as magnification and a range estimation reticle that are useful to an operator. However, the day optic&#39;s capabilities are severely limited when used in low-light conditions. A night-vision optical system, referred to hereinafter as “night optic,” enhances an operator&#39;s vision in low-light conditions, but may not possess the magnification and ranging capabilities that the day optic does. By using these dissimilar optical devices together, an operator gains increased usefulness of both systems. 
         [0010]    Several approaches exist to achieve the simultaneous use of dissimilar optics. Unfortunately, due to irregular manufacturing techniques, non-uniform design characteristics, etc. between such systems, there often exists an inherent problem of optical path deviation. This results in image misalignment when configuring separate optical devices for tandem use. This problem is common throughout the various approaches used to achieve the benefits of combining dissimilar optical systems. 
         [0011]    An integrated approach incorporates structures and methods to provide both day and night capabilities in a single system, such as those described in U.S. Pat. No. 5,892,617, U.S. Pat. No. 6,111,692, and U.S. Pat. No. 6,172,821. This approach results in a complex system of lenses and mirrors to achieve proper image alignment, additional bulk that must be carried even when the night capability is not required, and increased cost to produce, maintain, and repair. 
         [0012]    An alternate approach is to temporarily attach a night optic to a mount that suspends the night optic next to or above the day optic, as described in U.S. Pat. No. 4,629,295. A series of mirrors directs the collimated night imagery into the day optic&#39;s input aperture. In this arrangement, true imagery alignment must give way to a parallel alignment due to the different mounting heights of the optics. 
         [0013]    Tandem-mounted, or in-line, systems maintain the advantages of modularity, low center of gravity, and coaxial optical paths. Image alignment is more easily accomplished when optics are configured in this way. 
         [0014]    In this streamlined arrangement, an optical system, referred to hereinafter as “optic #1”, is mounted ahead of another optical system, hereinafter referred to as “optic #2”. Optic #1 is closest to the scene being viewed and the image it produces is projected into optic #2. Optic #2 is considered by the operator to be the primary optic. It produces an image that the operator uses most of the time. Optic #1 is added to the optical path when its imagery characteristics are desired to augment those of optic #2. To be of optimum use to the operator, the images produced by each of the optics must be properly aligned, or overlaid, for display to the operator. The inherent image misalignment, or image shift, must be eliminated or reduced to an acceptable level. 
         [0015]    Reducing or eliminating image shift due to alignment error has been achieved in several different ways. One way is to determine the amount of alignment error, and compensate by adjusting the primary optic (optic #2) to be aligned to the image output of optic #1. Unfortunately, this approach is not preferred because the primary optic will no longer be properly aligned to the target line of sight when optic #1 is removed. In some cases, the optical devices may not provide for a means of such adjustment. Another way, then, is to provide mechanical adjustment capability to each of the optics&#39; mounts. This approach is not desirable because realignment needs to be performed every time either of the optics is replaced. 
         [0016]    A more efficient approach is to introduce an assembly into the optical path between tandem optics that will provide for image shift correction. U.S. Pat. No. 3,359,849, U.S. Pat. No. 6,992,843, U.S. Pat. No. 7,142,357, U.S. Pat. No. 7,359,114, and U.S. Pat. No. 8,094,309 describe such structures and methods utilizing moveable lenses, rotating Risley prisms, pivotable mirrors, and diverting wedge-prism assemblies positioned within the optical path to redirect the imagery output in another direction. However, these structures and methods are typically incorporated into the housing of specific optical devices, near the output aperture. This limits the number of optical devices that can be used as optic #1 in a tandem configuration. 
         [0017]    The prior art methods and structures described in the aforementioned patents introduce and disclose a number of noteworthy advances and technological improvements within the art. 
         [0018]    However, they are limited in application, as they are typically integrated into a specific optical device, introduce complexity and performance degradation into the system, add bulk, increase cost, and require the non-intuitive manipulation of multiple assemblies, lenses, prisms, mirrors, etc. to accomplish the desired imagery alignment effect. Additionally, the alignment procedure is typically required to be performed by technicians at the device manufacturer&#39;s facilities rather than by the operator in the field. 
         [0019]    Accordingly, there is a need in the art for an improved, stand-alone image alignment device which enables the operator to optimize the use of a wider variety of tandem-mounted optical systems. 
       BRIEF SUMMARY OF THE INVENTION 
       [0020]    An image alignment device for tandem optics (IAD-TO) is disclosed which provides a stand-alone means to optimize the imagery produced by dissimilar tandem-mounted optics. The (IAD-TO) is comprised of an optical alignment element within a sealed housing that is installed between tandem optics through the use of an adaptor arm and mount interface. The optical alignment element not only aligns light rays transmitted from optic #1, it also compensates for field of view differences between the optical devices. The housing includes external adjusting mechanisms which act upon the alignment element, enabling the operator to execute image alignment adjustments on demand. Further attached to the housing is an adaptor arm which accommodates mounting an optical device in front of and in line with the optical alignment element. This arm is exchangeable with other adaptor arms designed to accommodate various optical devices as required. Further attached to the adaptor arm is a quick action mount that interfaces to the mounting surface upon which optic #2 is directly mounted. 
         [0021]    The IAD-TO enables and optimizes the use of tandem optics thereby imparting a (retrofit) system capability increase to multiple types of existing optical devices without physically modifying them or replacing them with another device. The increased system capability realized by the operator is the result of combining the performance characteristics of each optical device and enabling them to share capabilities. 
         [0022]    The IAD-TO also provides an aftermarket means for injecting data and other source imagery into the optical path, thereby adding new capability to the base optics. 
         [0023]    Featuring interchangeable adaptor arms and quick action mount interfaces, the IAD-TO can be used with multiple types of optical devices and can be mounted to a variety of surfaces when needed, and as quickly removed as required by the operator. 
         [0024]    The IAD-TO enables the operator to make on-demand image alignment adjustments, especially when using optical devices that provide no such alignment mechanisms. 
         [0025]    Other methods and technical features may be readily apparent to one skilled in the art from the following figures and descriptions. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0026]      FIG. 1  is a side view of an embodiment of the present invention configured for direct viewing use with a night vision monocular and an optical day scope. 
           [0027]      FIG. 2  is a cut-away view of the main housing component of an embodiment of the present invention showing the optical alignment element within. 
           [0028]      FIG. 3  is a cross-sectional view of the optical alignment element subcomponent of an embodiment of the present invention. 
           [0029]      FIG. 4  is a side view of an embodiment of the present invention configured for use with a telescope and a video camera on a remotely operated platform and using a remote display device. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    Referring now to the invention in more detail, in  FIG. 1  to  FIG. 3 , there is shown an IAD-TO  300  configured to be used with a night vision optic  001  and a day vision optic  002  for direct viewing.
         15  Mounting Surface—Picatinny Rail or other suitable surface upon which the IAD-TO and tandem optics are mounted.     001  Optic #1—The optical device which generates the imagery that is to be aligned with the imagery produced by optic #2.     002  Optic #2—The optical device which produces the base imagery upon which the aligned imagery output from IAD-TO  300  is superimposed.     300  Image Alignment Device for Tandem Optics (IAD-TO)     301  Main Housing of IAD-TO  300 .     302  Adaptor Arm—Attached to IAD-TO  300 , provides a mounting platform for Optic #1  001       303  Mounting Interface—Attaches IAD-TO  300 /Optic #1  001  assembly to the mounting surface  15  upon which Optic #2  002  is separately attached.     304  Attachment Mechanism—Thumbscrew, latch, or similar mechanism that secures Optic #1  001  to adaptor arm  302       305  Protective Caps for external adjustment mechanisms  306       306  External Adjustment Mechanisms—One on top and one on the side of the IAD-TO  300  which provide for lateral and vertical adjustments of the optical alignment element  320 .     307  Adjustment Driver—Acts directly upon the optical alignment element  320 .     308  Compression Spring—Located between the housing  301  and the adjustable lens tube opposite the corresponding adjustment driver  307 .     309  Pivot Gasket—Provides environmental seal and aft pivot surface between housing  301  and optical alignment element  320 .     310  Bearing Ring—Provides environmental seal and forward pivot surface between optical alignment element  320  and window cap  311 .     311  Window Cap—Forward end of housing  301  through which the optical alignment element     320  accepts imagery to be aligned.     320  Optical Alignment Element     321  Adjustable Lens Tube     322  Foctek Doublet Lens Assembly     323  Lens Retaining Ring     330  Magnification Lens       
 
         [0052]    In more detail, still referring to the invention of  FIG. 1  to  FIG. 3 , An image alignment device for tandem optics (IAD-TO)  300  is disclosed which provides a method and means to optimize the imagery produced by dissimilar tandem-mounted optics  001  &amp;  002 . In this arrangement, the imagery output from optic #1  001  is inherently misaligned with the imagery produced by optic #2  002 . The IAD-TO  300  allows the operator to correct this image shift so that it coincides more precisely with the desired imagery output from optic #2  002 . 
         [0053]    The IAD-TO  300  is comprised of an optical alignment element  320  within a sealed housing  301  that is positioned on a common mounting surface  15  between tandem optics  001  &amp;  002  through the use of an adaptor arm  302  and mount interface  303 . Attached to the housing  301  is an adaptor arm  302  which provides for mounting an optical device  001  in front of and in line with the optical alignment element  320 . The adaptor arm  302  is exchangeable with other adaptor arms designed to accommodate various optical devices as specified. Optical device  001  is secured to the adaptor arm  302  by a thumbscrew, latch, or similar mechanism  304 . Further attached to the underside of the adaptor arm  302  is a quick action mount  303  which interfaces to the mounting surface  15  upon which optic  002  is separately mounted. The IAD-TO  300 /optic #1  001  assembly is attached to the mounting surface  15  in front of optic #2  002 . 
         [0054]    The housing  301  includes two external adjusting mechanisms  306 , one on top and one on the side, which act upon the alignment element  320 , enabling the operator to execute image alignment adjustments on demand. Protective caps  305  cover the external adjusting mechanisms  306  and prevent inadvertent adjustment, physical damage, and environmental degradation to the adjustment mechanisms  306 . The adjustment mechanisms  306  actuate the adjustment drivers  307  which are in contact with the adjustable lens tube  321  of the optical alignment element  320 . In concert with opposing compression springs  308 , located between the housing  301  and the adjustable lens tube, the adjustment drivers  307  control lateral and vertical movement of the optical alignment element  320 . A pivot gasket  309  and bearing ring  310  provide pivot surfaces and environmental seals for the ends of the optical alignment element  320  as well as manage fore and aft movement within the housing  301 . 
         [0055]    The optical alignment element  320  is comprised of a Foctek doublet lens assembly with spacer  322  fixed within an adjustable lens tube  321  by a retaining ring  323 . As an option, this same assembly may be used separately as an afocal magnifier lens installed on the objective lens of various optics. The imagery output of optic #1  001  is received by the optical alignment element  320  through the window cap  311  at the forward end of the housing  301 . By adjusting the orientation of the optical alignment element  320  within the housing  301 , the optical path is altered so that the imagery output from the IAD-TO  300  is properly aligned with the optical path of optic #2  002 . Once this alignment has been achieved, the IAD-TO  300 /optic #1  001  assembly may be removed from the mounting surface  15  and reinstalled as needed without requiring further alignment. 
         [0056]    In further detail, still referring to the invention of  FIG. 1  to  FIG. 3 , when dissimilar optical devices are arranged in tandem, an inherent optical misalignment of 1-15′ of arc occurs due to manufacturing differences between the optics. The IAD-TO  300  enables the operator to correct for up to 35 minutes of angle (MOA) in any direction from center in 0.5 MOA increments. Lateral and vertical movements of the optical alignment element  320  are controlled by AZ/EL adjustment drives  307  and their corresponding springs  308  acting on the opposite side of the optical alignment element  320  from each adjuster  307 . A bearing ring  310  and pivot gasket  309  control movement of the fore and aft surfaces of the optical alignment element  320  within the main housing  301 , and assist in providing adjustment retention. 
         [0057]    Each movement of the optical alignment element  320  results in a corresponding deviation of the optical path, allowing the operator to “steer” the imagery output of optic #1  001  as necessary so that it precisely aligns with the imagery produced by optic #2  002 . 
         [0058]    The most efficient mounting arrangement is one that has all 3 devices at a common optical axis height above the mounting surface  15 , in this case approximately 40 mm. The adaptor arm  302  can be exchanged easily with adaptor arms designed for specific applications of different heights and/or optical devices. 
         [0059]    The optical alignment element  320  not only aligns light rays transmitted from optic #1  001 , it also compensates for field of view differences between the optical devices  001  &amp;  002 . The Foctek doublet lens assembly  322  within the optical alignment element  320  is specifically sized to convert optic #1  001  output to match the normal field of view (FOV) of optic #2  002 , in this case converting 40 degree FOV to 9 degrees. This is accomplished through the matching of a Foctek doublet lens assembly  322  with an appropriate length spacer. The sizes of the lenses and spacer lengths will affect the magnification and FOV ratios, providing for design flexibility to accommodate multiple types of dissimilar optical devices. 
         [0060]    An additional optical alignment element  320  subcomponent (magnification lens  330 ) can be used on optic #1  001  objective lens to magnify the scene and restore a 1:1 magnification ratio of the optic #1  001 /IAD-TO  300  combination. This means the scene as viewed through optic #2  002  will have the same FOV and magnification as it does with or without optic #1  001 /IAD-TO  300  assembly installed in front of optic #2  002 . As an option, an optical alignment element  320  subcomponent may be used separately as an afocal magnifier lens  330  installed on the objective lens of various optics to increase their useful operating range. 
         [0061]    The construction details of the invention as shown in  FIG. 1  to  FIG. 3  are that the IAD-TO  300  is constructed of lightweight materials, and that the materials are very durable against physical and environmental stressors such as direct impact, atmospheric pressure, extreme temperature, etc. 
         [0062]    The main external components may be made of aluminum (with a scratch resistant anodized coating applied), injection molded plastic (with glass or carbon fiber reinforcement), or other sufficiently rigid and strong material. These include the main housing  301 , protective caps  305 , adaptor arm  302 , mount interface  303 , attachment mechanism  304 , window cap  311 , adjustable lens tube  321 , and lens retaining ring  323 . 
         [0063]    The lens assembly  322  is optical glass that is specially hard carbon coated to provide scratch resistance and optimize low light performance. High strength plastic or other compounds suitable as replacements for optical glass may be used. 
         [0064]    Other hardware such as retaining screws, compression springs  308 , and adjuster drivers  307  is made from metals such as stainless steel, aluminum, and titanium. 
         [0065]    Flexible seals are made of neoprene rubber, silicon, or other suitable material to prevent environmental effects penetrating the housing  301 . 
         [0066]    Referring now to the invention in more detail, in  FIG. 2  to  FIG. 4 , there is shown an IAD-TO  300  configured to be used with an optical telescope (optic #1)  001 - 4  and a digital video camera (optic #2)  002 - 4  mounted on a remotely operated positioning apparatus  400 . The combined imagery is transmitted to a remote display device  401  for viewing by the operator.
         001 - 4  Optic #1—(Optical Telescope) generates the imagery that is to be aligned with the imagery produced by optic #2.     002 - 4  Optic #2—(Video Camera) produces the base imagery upon which the aligned imagery output from IAD-TO  300  is superimposed.     300  Image Alignment Device for Tandem Optics (IAD-TO)     301  Main Housing of IAD-TO  300       305  Protective Caps for external adjustment mechanisms  306       306  External Adjustment Mechanisms—One on top and one on the side of the IAD-TO  300  which provide for lateral and vertical adjustments of the optical alignment element  320 .     307  Adjustment Driver—Acts directly upon the optical alignment element  320 .     308  Compression Spring—Located between the housing  301  and the adjustable lens tube opposite the corresponding adjustment driver  307 .     309  Pivot Gasket—Provides environmental seal and aft pivot surface between housing  301  and optical alignment element  320 .     310  Bearing Ring—Provides environmental seal and forward pivot surface between optical alignment element  320  and window cap  311 .     311  Window Cap—Forward end of housing  301  through which the optical alignment element  320  accepts imagery to be aligned.     320  Optical Alignment Element     321  Adjustable Lens Tube     322  Foctek Doublet Lens Assembly     323  Lens Retaining Ring     400  Remotely Operated Positioning Apparatus     401  Remote Display     402  Adaptor Arm to mount Telescope     403  Mount Interface for Tilt &amp; Pan platform     404  Attachment Mechanism—Optic #1  001 - 4  to adaptor arm  402       415  Mounting Surface—Platform, Tilt &amp; Pan     430  Magnification Lens       
 
         [0089]    In more detail, still referring to the invention of  FIG. 2-FIG .  4 , in this embodiment, the IAD-TO  300  is used with optic #2  002 - 4  to retrofit alignment and video capture capabilities to optic #1  001 - 4  that was originally manufactured without them. 
         [0090]    The IAD-TO  300  is coupled with optic #1  001 - 4  by means of the adaptor arm  402  with attachment mechanism  404 . Attached to the underside of the adaptor arm is the mount  403  which interfaces with the tilt &amp; pan platform  415  upon which optic #2 is separately attached. When initially configured this way, the imagery output from optic #1  001  is inherently misaligned with the imagery produced by optic #2  002 . The IAD-TO  300  allows the operator to correct this image shift so that it precisely overlays the desired imagery output from optic #2  002 . The operator manipulates the external adjustment mechanisms  306  of the IAD-TO  300  to align the imagery output from Optic #1  001 - 4  to that of Optic #2  002 - 4 . The combined imagery is then sent to the remote display  401  for viewing by the operator. 
         [0091]    The IAD-TO  300  is comprised of an optical alignment element  320  within a sealed housing  301  that is positioned on a common mounting surface  415  between tandem optics  001 - 4  &amp;  002 - 4  through the use of an adaptor arm  402  and mount interface  403 . Attached to the housing  301  is an adaptor arm  402  which provides for mounting an optical device  001 - 4  in front of and in line with the optical alignment element  320 . The adaptor arm  402  is exchangeable with other adaptor arms designed to accommodate various optical devices as specified. Optical device  001 - 4  is secured to the adaptor arm  402  by a thumbscrew, latch, clamp or similar attachment mechanism  404 . Further attached to the underside of the adaptor arm  402  is a quick action mount  403  which interfaces to the mounting surface  415  upon which optic #2  002 - 4  is separately mounted. The IAD-TO  300 /optic #1  001 - 4  assembly is attached to the mounting surface  415  in front of optic #2  002 - 4 . 
         [0092]    The housing  301  includes two external adjusting mechanisms  306 , one on top and one on the side, which act upon the alignment element  320 , enabling the operator to execute image alignment adjustments on demand. Protective caps  305  cover the external adjusting mechanisms  306  and prevent inadvertent adjustment, physical damage, and environmental degradation to the adjustment mechanisms  306 . The adjustment mechanisms  306  actuate the adjustment drivers  307  which are in contact with the adjustable lens tube  321  of the optical alignment element  320 . In concert with opposing compression springs  308 , located between the housing  301  and the adjustable lens tube, the adjustment drivers  307  control lateral and vertical movement of the optical alignment element  320 . A pivot gasket  309  and bearing ring  310  provide pivot surfaces and environmental seals for the ends of the optical alignment element  320  as well as manage fore and aft movement within the housing  301 . 
         [0093]    The optical alignment element  320  is comprised of a Foctek doublet lens assembly with spacer  322  fixed within an adjustable lens tube  321  by a retaining ring  323 . As an option, this same assembly may be used separately as an afocal magnifier lens installed on the objective lens of various optics. The imagery output of optic #1  001 - 4  is received by the optical alignment element  320  through the window cap  311  at the forward end of the housing  301 . By adjusting the orientation of the optical alignment element  320  within the housing  301 , the optical path is altered so that the imagery output from the IAD-TO  300  is properly aligned with the optical path of optic #2  002 - 4 . Once this alignment has been achieved, the IAD-TO  300 /optic #1  001 - 4  assembly may be removed from the mounting surface  415  and reinstalled as needed without requiring further alignment. 
         [0094]    In further detail, still referring to the invention of  FIG. 2  to  FIG. 4 , when dissimilar optical devices are arranged in tandem, an inherent optical misalignment of 1-15′ of arc occurs due to manufacturing differences between the optics. The IAD-TO  300  enables the operator to correct for up to 35 minutes of angle (MOA) in any direction from center in 0.5 MOA increments. Lateral and vertical movements of the optical alignment element  320  are controlled by AZ/EL adjustment drives  307  and their corresponding springs  308  acting on the opposite side of the optical alignment element  320  from each adjuster  307 . A Ring bearing ring  310  and pivot gasket  309  control movement of the fore and aft surfaces of the optical alignment element  320  within the main housing  301 , and assist in providing adjustment retention. 
         [0095]    Each movement of the optical alignment element  320  results in a corresponding deviation of the optical path, allowing the operator to “steer” the imagery output of optic #1  001 - 4  as necessary so that it precisely aligns with the imagery produced by optic #2  002 - 4 . 
         [0096]    The most efficient mounting arrangement is one that has all 3 devices at a common optical axis height above the mounting surface  415 , in this case approximately 40 mm. The adaptor arm  402  can be exchanged easily with adaptor arms designed for specific applications of different heights and/or optical devices. 
         [0097]    The optical alignment element  320  not only aligns light rays transmitted from optic #1  001 - 4 , it also compensates for field of view (FOV) differences between the optical devices  001 - 4  &amp;  002 - 4  and optimizes the analog imagery in preparation for digital conversion. The Foctek doublet lens assembly  322  within the optical alignment element  320  is specifically sized to convert optic #1  001 - 4  output to match the normal FOV of optic #2  002 - 4 . This is accomplished through the matching of a Foctek doublet lens assembly  322  with appropriate length spacer. The sizes of the lenses and spacer lengths directly affect the magnification and FOV ratios, providing for design flexibility to accommodate multiple types of dissimilar optical devices. 
         [0098]    An additional magnification lens  430  can be used on optic #1  001 - 4  objective lens to magnify the scene and restore a 1:1 magnification ratio of the optic #1-4/IAD-TO  300  combination. This means the scene as viewed through optic #2  002 - 4  will have the same FOV and magnification as it does with or without optic #1  001 - 4 /IAD-TO  300  assembly installed in front of optic #2  002 - 4 . 
         [0099]    The construction details of the invention as shown in  FIG. 2  to  FIG. 4  are that the IAD-TO  300  is constructed of lightweight materials, and that the materials are very durable against physical and environmental stressors such as direct impact, atmospheric pressure, extreme temperature, etc. The main external components may be made of aluminum (with a scratch resistant anodized coating applied), injection molded plastic (with glass or carbon fiber reinforcement), or other sufficiently rigid and strong material. These include the main housing  301 , protective caps  305 , adaptor arm  402 , mount interface  403 , attachment mechanism  404 , window cap  311 , adjustable lens tube  321 , and lens retaining ring  323 . 
         [0100]    The lens assembly  322  is optical glass, specially hard carbon coated to provide scratch resistance and optimize low light performance. High strength plastic or other compounds suitable as replacements for optical glass may be used. 
         [0101]    Other hardware such as retaining screws, compression springs  308 , and adjuster drivers  307  is made from metals such as stainless steel, aluminum, and titanium. 
         [0102]    Flexible seals are made of neoprene rubber, silicon, or other suitable material to prevent environmental effects penetrating the housing. 
         [0103]    The advantages of the present invention include, without limitation, that it provides a retrofit capability increase to existing products. It provides a pathway to inject data and other source imagery into the optical stream, thereby enabling new capabilities to be added to both optical devices. It enables the operator to make alignment adjustments as needed without having to involve technicians or send the device back to the manufacturer. It provides a means and method of alignment for those devices where no such provision exists. It is easily adaptable to many different types of devices. It is a modular approach which yields an easy to remove/replace component that does not degrade the original operating capabilities of either of the other optical devices. It is a simple design for low cost and ease of manufacture and maintenance. It is a low cost investment for improving items—not a high cost replacement product. 
         [0104]    In broad embodiment, the invention is an improved image alignment device for optimizing the use of tandem-mounted optical systems. 
         [0105]    While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The invention should therefore not be limited by the above described embodiment, method, and examples, but by all embodiments and methods within the scope and spirit of the invention as claimed.