Patent Publication Number: US-2023152550-A1

Title: Actuator for Positioning Optical Filters

Description:
STATEMENT OF GOVERNMENT INTEREST 
     The invention described was made in the performance of official duties by one or more employees of the Department of the Navy, and thus, the invention herein may be manufactured, used or licensed by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. 
    
    
     BACKGROUND 
     The invention relates generally to actuators. In particular, the invention relates to mechanical devices for remote interchanging of optical filters, especially for camera recording of laser tests. 
     Imaging the engagement of a laser beam on a target is a diagnostic technique used to assess system performance and specifications. This imaging can be difficult due to the high irradiance levels delivered to the target by modern High Energy Laser (HEL) systems. Absorbing neutral density (ND) filters are required in order to attenuate the light intensity to a level that will not saturate the camera&#39;s sensor. These ND filters are typically threaded in to the camera lens and must be manually installed or removed based on the anticipated light level. 
     This process can be burdensome for a camera located where it is difficult for personnel to gain access. Additionally, optimizing lens settings, such as focus and field-of-view, for imaging a target is challenging with installed ND filters. Therefore, by utilizing a remotely actuated filter system, the camera can be positioned and optimized relative to the target prior to installing the filters and then the appropriate filter can be installed without disturbing the cameras position or settings. Particular filters can be switched on and off remotely by the operator as the laser engagement scenarios change to match test conditions. 
     SUMMARY 
     Conventional optical filter positioners yield disadvantages addressed by various exemplary embodiments of the present invention. In particular, various exemplary embodiments provide an actuator mechanism for disposing a plurality of filters into and out of a camera line-of-sight. The mechanism includes a base, a pair of frames, an axial shaft, a plurality of filter housings and a plurality of pivotable drivers. The base includes an auxiliary platform. The frames flank the base, and the shaft is disposed between the frames. Each filter housing holds a corresponding optical filter and is disposable in a deployment position in the line-of-sight and a withdrawn position out of the line-of-sight. The drivers are disposed on the platform. Each driver corresponds to an associated housing and is rotatable along the shaft to swing at least one housing between deployment and withdrawn positions upon command. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and various other features and aspects of various exemplary embodiments will be readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings, in which like or similar numbers are used throughout, and in which: 
         FIG.  1    is a diagram view of a conventional test setup; 
         FIG.  2    is a diagram view of an exemplary test setup; 
         FIG.  3    is a diagram view of an exemplary test site; 
         FIG.  4    is an isometric assembly view of an imaging equipment assembly; 
         FIG.  5    is an isometric exploded view of a filter actuator assembly; 
         FIG.  6    is an isometric exploded view of a filter mechanism; 
         FIG.  7    is an elevation assembly view of the filter mechanism; and 
         FIGS.  8 A and  8 B  are isometric assembly views of the filter mechanism. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description of exemplary embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific exemplary embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized, and logical, mechanical, and other changes may be made without departing from the spirit or scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims. 
     The disclosure generally employs quantity units with the following abbreviations: length in inches (in), mass in pounds-mass (lb m ), time in seconds (s), and torque in inch-pounds-force (in-lb f ). 
       FIG.  1    shows a diagram view  100  of a conventional laser test setup. A blockhouse  110  with laser  120 , laser operator  125 , data collection operator  130 . Laser  120  directed towards target test site  140  with a target  150 . Reflections therefrom are received through a filter mechanism  160  into a lens  170  and recorded by a camera  180  remotely controlled electronic linkage  190  via the data control operator  130 . 
       FIG.  2    shows a diagram view  200  of an exemplary laser test setup. The blockhouse  210  maintains the laser operator  125  and the data collection operator  130 , while the laser  120  is disposed at an exemplary test site  220  to illuminate the target  150 . Beam imaging equipment  240  controlled via linkage  250  via the data collection operator  130  includes an exemplary filter actuation mechanism  260  receives reflections from the target  150  transmitted through the lens  170  and into the camera  180 . 
       FIG.  3    shows a diagram view  300  of the test site  220 . The laser  120  emits a coherent electromagnetic light beam  310  to illuminate the target  150 , which reflects some of the incident energy and thereby producing a reflection area  320 . The filter mechanism  260  as one module of the beam imaging equipment  240  has a field-of-view  330  from which to receive reflected electromagnetic energy, which is then transmitted through the lens  170  and recorded by the camera  180 . 
       FIG.  4    shows an isometric assembly view  400  of the beam imaging equipment  240 , illustrated as modules, rather than as generic boxes. The filter actuation mechanism  260  includes a series of movable filter actuator assemblies  410 , so the quantity of reflected electromagnetic energy into the camera  180  can be adjusted by selecting the number of filter assemblies  410  to interpose between the reflection area  320  and the lens  170 . 
       FIG.  5    shows an isometric exploded view  500  of the filter actuator assembly  410  comprising a filter module  510  to contain an optical filter disk  515  and an actuator module  520 . The filter module  510  includes a housing ring  530  to contain the ND filter disk  515  along with a swing armature  535 . The actuator module  520  includes a linear actuator or driver  540  with a ribbon  545  and terminating in pin joint  550 . Each pivotable joint  550  includes a hinge  555 , a nutand-bolt fastener  560  and a bracket  565 . 
     The swing armature  535  includes a sleeve  570  into which a bronze bushing  580  inserts therein to reduce friction. The housing ring  530  can secure the filter  515  by tightening peripheral locking screws  590 . The driver  540  unwinds or retracts the ribbon  545  to lengthen or shorten the distance between opposite pivotable joints  550 . The driver  540  is preferably a miniature electric linear actuator, for example, an Actuonix PQ12-001-6-R. 
       FIG.  6    shows an isometric exploded view  600  of filter actuation mechanism  260 . In the example view  600 , five filter assemblies  410  are featured. These include a distal unit  610 , a withdrawn unit  612 , an intermediary unit  614 , an adjacent unit  616  and a proximal unit  618  shown disassembled. The units  610 ,  614 ,  616  and  618  are shown in deployment position aligned with the camera  180 . Any filter module  510  and its associated actuator module  520  are presented herein as the filter actuator assembly  410 . 
     The filter actuator assemblies  410  separately identified as units  610 ,  612 ,  614 ,  616  and  618  are contained between flanking aluminum frames  620 , each with a hole  625  and mounted to a base  630  that supports tangent spacer blocks  640  to separate the drivers  540 . A plate  650  provide a mount onto which the actuator modules  520  attach. A shaft rod  660  inserts into the holes  625  while also passing through the bushing  580  in the sleeve  570  of each ring  530 . Screws  670  secure the frames  620  to the base  630 . Screws  680  secure the blocks  640  and the base  630 . Screws  690  secure the plate  650  to the frames  620  for anchoring the driver  540  to the plate  650 . The rings  530 , filter disks  515 , drivers  540  and ribbons  545  are uniform in size. Opacity distinctions in filter disks  515  are independent of exemplary embodiments. 
     Each filter module  510  includes the optical filter disk  515  encased in the ring  530  secured by the locking screws  590 . By the driver  545  expanding and contracting the ribbon  545 , the armature  535  turns on the rod  660 , operating as a swing arm attached to the plate  650  and to the ring&#39;s sleeve  570  by pivotable joints  550 . 
       FIG.  7    shows an isometric assembly view  700  of the filter actuator mechanism  260  with exemplary scales. With select filter actuator assemblies  410  engaged and withdrawn, the mechanism  260  extends 6.9 inches in length, 2.75 inches in width and 7.35 inches in height. The filter disks  515  have an outer diameter of 3.75 inches with a center  710  that the driver  540  rotates along an arc  720 . The ring  530  connected via the rod  660  follows, rotating along an arc  730  about the axis of the rod  660 . Total mass of the actuator mechanism  260  is about 1.0 lb m . Torque of the drivers  540  is about 2.5 in-lb f . These dimensions are exemplary and not limiting. 
       FIGS.  8 A and  8 B  show isometric assembly views  800  of the filter actuator mechanism  260 , in which withdrawn unit  512  is elevated out from the laser optical line-of-sight. The assembly shows the actuator module  520  connecting to the rings  530  by fasteners  560  and to the plate  670  by fasteners  550 . The rod  660  passes through sleeves  570  and their bushings  580  and terminate at the holes  625  of the frames  620 . 
     The filter modules  510  are swung into or out of alignment with the camera  180  by miniature electric drivers  540  controlled remotely using an onboard microcontroller that communicates with a control computer via the operator  130  in the blockhouse  210 . Alignment of the filter disks  515  with the camera  180  is ensured when in the lowered position by the pair of tangent spacer blocks  640 . 
     The rings  630  with their armatures  535  are fabricated as a single unit from 6061 aluminum and contain an oil impregnated bronze bushing  580  in the sleeve  570  to ensure smooth operation. The filter modules  510  are swung into or out of alignment with the camera  180  by their corresponding drivers  540 , which are controlled remotely using an onboard microcontroller via the operator  130  in the blockhouse  210 . Alignment of the filter disks  515  with the camera  180  is ensured when in the lowered position by the two tangent spacer blocks  640 . 
     The exemplary filter mechanism  260  operates in open-air HEL Test and Evaluation (T&amp;E) events. The camera  180 , lens  170 , and filter mechanism  260  are disposed near the target  150  being engaged by the laser  120  at the test site  220 , which can be an isolated location in which personnel are prohibited. The operator  130  is at a separate blockhouse  210  for safety reasons. The remotely actuated filter mechanism  260  enables the optical filters  515  to be switched without personnel having to travel downrange to the target test site  220 . 
     The ability to remotely change and stack filters on the exemplary mechanism  260  is an advantage when the camera  180  and the operator  130  cannot be co-located. This enables settings for the camera  180  and lens  170  to be optimized for each situation as, for instance, reflectivity of the target  150  or the laser power change. Additionally, initial setup can be accomplished with no filters actuator assemblies  410  installed, which enables a clear view of the target  150  with the camera  180 . Once settings are adjusted and the position aligned, the appropriate filter actuator assemblies  410  can be remotely deployed without affecting the position of the equipment  240 . 
     As a conventional alternative, filter disks  515  can be manually threaded into camera lenses  170 . Remotely operated filter wheels exist but these require a much larger volume for a given aperture size. These are typically limited to apertures of 50 mm or less. 
     While certain features of the embodiments of the invention have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the embodiments.