Abstract:
A night vision device comprising a first detector, a beam splitter, a user optical output and a camera. The first detector is configured to detect and transmit a scene image in a first spectral band along a first optical path. The beam splitter is configured to receive the first optical path image; to output, along a second optical path, a first portion of the first optical path image, and to output, along a third optical path, a second portion of the first optical path image. The user optical output is configured to receive and output images traveling along the second optical path. The camera is configured to receive and store images traveling along the third optical path.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to night vision devices, and more particularly, to a night vision device including a camera to record the images produced by the night vision device. 
     Night vision devices are commonly used by military personnel for conducting operations in low light or night conditions. The night vision devices utilized by the military typically include image intensifier tubes and associated optics that convert visible and near infrared light into viewable images. Conventional night vision goggles (NVG) have been in widespread use for several decades. All variants of the currently fielded hardware are based on a common optical architecture. This architecture consists of an objective lens, an image intensifier tube, and an eyepiece lens. Functionally, the objective lens focuses an image of a low light level scene onto the image intensifier tube. The intensifier tube amplifies this faint image and presents an amplified image on its output surface. The eyepiece lens allows a human eye to view the amplified image. 
     To enhance night vision devices, enhanced night vision goggles (ENVG) have been developed. See for example U.S. Pat. Nos. 5,035,472; 6,560,029; 6,762,884; and 6,791,760, each of which is incorporated herein by reference. These ENVG&#39;s incorporate thermal imaging cameras or detectors to detect infrared radiation. Thermal imaging cameras are responsive to different portions of the infrared spectrum and are often referred to as infrared cameras, thus providing additional information to the viewer. The images from the image intensifier tube and from the infrared camera are combined to provide an enhanced image to the user. 
     SUMMARY OF THE INVENTION 
     The present invention provides a night vision device generally comprising a first detector, a beam splitter, a user optical output and a camera. The first detector detects and transmits a scene image in a first spectral band along a first optical path. The beam splitter is configured to receive images traveling along the first optical path; to output, along a second optical path, a first portion of the images traveling along the first optical path; and output, along a third optical path, a second portion of the images traveling along the first optical path. The user optical output is configured to receive and output images traveling along the second optical path. The camera is configured to receive and store images traveling along the third optical path. 
     The present invention also provides a night vision device comprising a housing, a first optical receiver located within the housing, wherein the first optical receiver transmits a first optical signal, and a second optical receiver located within the housing, wherein the second optical receiver transmits a second optical signal. A signal combiner is located within the housing, wherein the signal combiner combines the first optical signal and the second optical signal to form a first combined optical signal and a second combined optical signal. An optical display is optically aligned with the first combined optical signal to display the first combined optical signal to a user. A camera is optically aligned with the second combined optical signal, such that the camera records at least the first optical signal. 
     Further, the present invention provides a method of observing and recording an image through a night vision goggle comprising the steps of transmitting an image intensification generated optical image to a beam splitter; transmitting an infrared generated optical image to the beam splitter; splitting the image intensification generated optical image at the beam splitter and transmitting a first percentage of the image intensification generated optical image to a lens for viewing and transmitting a remaining percentage of the image intensification generated optical image to a camera for recording; and splitting the infrared generated optical image at the beam splitter and transmitting a first percentage of the infrared generated optical image to a lens for viewing and transmitting a remaining percentage of the infrared generated optical image to a camera for recording. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is best understood from the following detailed description when read in connection with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawing are not to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawing are the following figures: 
         FIG. 1  shows an embodiment of the night vision goggle of the invention as worn by a user. 
         FIG. 2  is a cross-sectional view of the night vision goggle of  FIG. 1 . 
         FIG. 3  is a block diagram of the night vision goggle of  FIG. 1  with a filter configured to provide only images from an image intensifier to a modular camera assembly. 
         FIG. 4  is a block diagram of the night vision goggle of  FIG. 1  with a filter configured to provide images from an image intensifier and a second channel display to a modular camera assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1–4 , a night vision goggle  10  that is a first embodiment of the present invention is shown. The night vision goggle  10  may be monocular or binocular. As shown in  FIG. 1 , the night vision goggle  10  may be mounted on a helmet  14  via a support bracket  12 . While the present invention is described as mounted to a helmet, the invention is not limited to such. The night vision goggle  10  may be used in various other applications. For example, the night vision goggle  10  may be a handheld device, mounted to a head harness or on a weapon, or supported by a strap assembly independent of the helmet. 
     The night vision goggle  10  generally includes an image intensifier  20 , a second channel sensor, such as an infrared camera  40 , a user output  50  and a camera assembly  60 . These devices are retained within a housing  18 . While a single housing  18  is shown, one or more of the components may be provided as stand alone components that are attached to or otherwise associated with the housing  18 . The camera assembly  60  may be a stand-alone camera that can be attached as needed and stored when unnecessary, thereby reducing weight of the system. A plug or cover (not shown) can be positioned over the camera assembly&#39;s port when not in use. 
     The image intensifier  20  includes an objective lens assembly  22  configured to focus visible and near infrared light from a sensed image  102  onto an image intensifier tube  24 . The image intensifier tube  24  is preferably a known I 2  tube, which generally includes a photo-cathode that converts the light photons to electrons, a multi-channel plate that accelerates the electrons and a phosphor screen that receives the accelerated electrons and creates a luminance in response to the accelerated electrons. The image created by image intensifier  20  is directed along an image intensified input path, as indicated by arrow  103 , to a beam splitter  54 . The beam splitter  54  may combine and/or split received beams, as will be described in more detail hereinafter, but is referred to herein as a beam splitter. The user display optics  52  are substantially co-axial with the image intensifier  20  and the beam splitter  54 , but instead may be offset with a non-linear optics path defined therebetween. Image intensifier  20  is preferably a late model version such as referred to in the art as Generation III, or a later model when such becomes available. If desired, an earlier model, such as a Generation II, may be used. 
     While the second channel sensor may be any suitable sensor, for purposes of the present disclosure, the second channel sensor will be described as the infrared camera  40 . The infrared camera  40  is used to convert infrared imagery into a visible image. The infrared camera  40  may be based on an uncooled focal plane array (FPA) and incorporates its own objective lens  42 , which is designed to provide a thermal video field of view that is essentially the same as the field of view of the image intensifier  20 . The optical axes of infrared camera  40  and image intensifier  20  are aligned generally parallel to each other during assembly of the night vision goggle  10 . The objective lens  42  focuses the infrared image  106  on to the thermal sensor  44 , which outputs a signal indicative of the image. A system electronics  100  receives the output signal from the thermal sensor  44  and projects the image onto a display  46 . The display  46  is configured to provide an infrared image along a camera output path  107  to the beam splitter  54  at a substantially right angle relative to the path of the image intensifier image  103 . 
     The display  46  can have various configurations, for example, an emissive type, reflective type, or transmissive type. An emissive type is preferred for the present application since it offers the smallest package and consumes the least power, although reflective and transmissive type displays are encompassed herein. Emissive displays include electroluminescent displays, vacuum fluorescent displays, field emissive displays and OLEDS (organic LED&#39;s). As the name implies, the emissive source emits light and does not require a separate light source. 
     The beam splitter  54  includes a dichroic surface  56  that is configured to control passage of the image intensifier image  103  and the infrared camera video image along the camera output path  107  through the beam splitter  54 . The dichroic surface  56  allows a predetermined percentage of light incident thereon to pass through while reflecting the remainder of the light. For example, the dichroic surface  56  may be configured to allow approximately 70–90 percent of the light incident thereon to pass through while the remaining 10–30 percent is reflected. The percentage of pass through may be varied and is not limited to the indicated range. 
     In the present embodiment of the invention, the dichroic surface  56  is configured to allow a percentage of the light incident thereon to pass through. By way of example only, 85 percent of the incident thereon may pass through. As such, approximately 85 percent of the image intensifier image  103  passes through the beam splitter  54  toward the user display optics  52 , along a visual lens output path, as indicated by arrow  104 , while a remaining percentage, in this case, approximately 15 percent, is reflected. With the dichroic surface  56  at an approximately 45 degree angle, the reflected portion of the image  105  is directed upward in the figures, parallel to the path of the camera output path  107 . Similarly, a percentage of the video display image along the camera output path  107  passes through the dichroic surface  56 , as indicated by arrow  108 , and combines and travels with the intensifier image reflected portion  105 . Again, by way of example only, this percentage may be 85 percent of the video display image. The remaining percentage, in this case, approximately 15 percent, of the video display image along the camera output path  107  reflects off the dichroic surface  56 , as indicated by the arrow  109 , and combines with the passed through portion  104  of the intensifier image. Mathematically speaking, the percentage of light incident on the dichroic surface  56  that passes through the dichroic surface  56  may be “x” percent, while a remaining percentage, “(100-x)” percent, is reflected. The percentage of the video display image along the camera output path  107  that passes through the dichroic surface  56  is also “x” percent, while a remaining percentage, “(100-x)” percent, is reflected. 
     The combined images  104  and  109  are directed along a visual lens output path toward the user display optics  52 . The user display optics  52  provide the user with the ability to focus on the beam splitter  54  such that the combined image is provided to the user&#39;s eye. 
     The reflected portion  105  of the intensifier image and the passed through portion  108  of the video display image travel along a camera output path toward the camera assembly  60 . The camera assembly  60  generally comprises a filter  62 , a relay lens  64 , and a recording camera  66 . The recording camera  66  senses all or part of the image portions  105  and  108 , depending on the filter  62 , and creates still images or a video signal that contains a rendition of the sensed image portions  105  and  108 . To capture both the image portions  105  and  108  with a balance equivalent to that observed through the display optics  52 , the filter  62  may be an absorbing filter that reduces, but does not eliminate, the sensed image portion  108 , such that the combined image is provided to recording camera  66 . This filter configuration is shown in  FIG. 3 . To capture only the intensifier image portion  105 , the filter  62  may be a band pass filter to eliminate the video display image portion  108 , thereby only passing the intensifier image portion  105  to the recording camera  66 , as shown in  FIG. 4 . The system controller  80  may be configured to allow the user to adjust the filter  62  to select the image configuration delivered to the recording camera  66 . 
     The recording camera  66  may be of the CMOS or CCD type, for example, a CMOS “camera-on-a-chip” or a CCD chip with its associated camera printed circuit boards, although other solid state imaging arrays could also be used. The recording camera  66  may have various configurations, for example, the recording camera  66  may be a monochrome camera or a VGA camera, depending on the desired recorded image or video. A monochrome camera with fast optics may provide a larger field of view at a desired resolution. A VGA camera with a higher pixel count may provide a higher resolution and field of view, although such may effect the bandwidth. The field of view for any camera may also be increased by increasing the size of beam splitter  54 . 
     The recording camera  66  may have an integral automatic gain control (AGC) function or other manual or automatic function controls. The AGC control loop has the purpose of adjusting effective camera gain so the video signal image has optimum intra scene dynamic range at any given time. The AGC loop may be integral to the CMOS camera-on-a-chip. 
     Depending on the specific type, the recording camera  66  may output digital, video, or both signals. The output signals are output to a memory  65 . The memory  65  may be a removable memory, a permanent memory or a combination of both. With a removable memory, the stored images or video may be removed from the camera assembly  60  for storage and review. With a permanent memory, an I/O port may be used to output the stored images or video. In the illustrated embodiment, the I/O port includes a wireless transmitter  67 , for example, an RF transmitter or telemetry transmitter, configured to send image or video signals to a remote location. The I/O port may also include hardwire ports (not shown). The transmitter  67  may be configured to provide real-time signals to the remote location to allow users at the remote location to observe the scene observed by the NVG  10  user in real-time. 
     Referring to  FIGS. 3 and 4 , system electronics  100  are associated with the image intensifier  20 , the infrared camera  40 , the video display  46  and the camera assembly  60 . The system electronics  100  are also associated with a battery  120  and a controller  80 . The battery  80  supplies power to each of the components of NVG  10 . Alternatively, the camera assembly  60  may have an independent power supply. The controller  80  is configured to control the image intensifier  20  and the infrared camera  40  and may also be configured to control the camera assembly  60 . Alternatively, the camera assembly  60  may have an independent control assembly. 
     Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.