Camera Systems

High-performance imaging devices need specialized camera systems that will take full advantage of the unique features of these devices and will not degrade their inherent low-noise performance. Following are a few examples of cameras and special assemblies that the Advanced Imager Technology program area has built for different applications.

The Ground-Based Electro-Optical Deep-Space Surveillance (GEODSS) camera (Figure 1) is used in an operational system to track and classify satellites in low Earth orbit. A cooled charge-coupled-device (CCD) camera fits into a legacy 1 m diameter telescope.

Space Surveillance CameraFigure 1. The GEODSS camera is the black tube mounted to the telescope (left). The picture on the right is the side view of the camera with its case removed.

 

Cold head of 4-sample high-speed cameraFigure 2. Cold head of four-sample high-speed camera. Note the multiple vacuum electrical feed-through posts for driving the electronic shutter.

The camera (Figure 2) designed for the Four-Sample High-Burst-Rate CCD device is another example. This device also operates at cryogenic temperatures, has constraints on the space available to mount components, must operate in several modes with low noise, and needs special high-current pulse drivers integrated into the dewar to meet the speed requirements of the electronic shutter of the device.

Photon sensitive cameraFigure 3. Photon-counting camera capable of taking photon-starved pictures with high-bit-depth.

There have been a number of single-photon-sensitive cameras designed and built, both for LADAR and passive photon-counting applications. The camera shown in Figure 3 counts photons reflected from a target. Each frame is binary—that is, a photon either is or is not detected at each pixel site. The camera takes many 256 x 256-pixel frames at high speed (10,000 fps) and co-adds hundreds of frames to constitute an intensity image of the target (more frames constitute larger bit depth of the picture).

We developed a high-dynamic-range camera (Figure 4) to see through brownout conditions during helicopter landings in the desert or other dusty conditions. Brownout conditions during landing or takeoff cause many helicopter accidents. To mitigate this problem, a high-dynamic-range, low-noise sensor is required. We built a custom camera using our digital-pixel focal plane array technology, which meets these requirements.

LWIR cameraFigure 4. On the left is the high-dynamic-range camera to mitigate brownout conditions, and on the right is the MH-60 helicopter the camera was installed on for tests.

 

Using our digital-pixel focal plane array technology, we designed and built a scanning sensor engine for the Wide-Area Infrared System for Persistent Surveillance (WISP) program. The airborne version of WISP provides greatly improved coverage area compared to other sensors. (Figure 5 shows the scanning sensor engine for the WISP integrated into a Constant Hawk gimbal.) Figure 6 shows the digital-pixel focal plane array sensor package used in the sensor engine; Figure 7 is a movie showing the scanning operation of the WISP tower sensor engine.)

Figure 7. Movie showing operation of scanning WISP tower sensor engine. A 100 Mpixel image, 360 deg in azimuth by 10 deg in elevation above and below the horizon, is captured every two seconds with 150 urad resolution everywhere in the scene.

 

The Space Surveillance Telescope (SST) rapidly scans the sky for dim satellite targets and to perform astrometry. This very wide-field telescope is enabled by a special Mercene-Schmidt telescope that has a curved, not flat, focal surface. Using its expertise in working with thin silicon membranes, Lincoln Laboratory fabricated unique spherical surface CCD imagers (see Figure 8) to fit the curved focal surface to within 5 microns over the entire 12-device image surface.

 

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