Scientific and DoD CCD Imagers

Scientific and surveillance imaging charge-coupled-device (CCD) design and fabrication are driven primarily by performance requirements, unlike commercial device fabrication. Because scientific and surveillance CCDs often are used to detect images from large optical systems, a very large-area imager is often required.

Historical Growth in Lincoln Laboratory-fabricated CCDsFigure 1. Growth in size of Lincoln Laboratory–fabricated CCDs over our first 20 years of operation.

 

Figure 1 shows the growth in size of CCD imaging devices over the first 20 years of development at MIT Lincoln Laboratory. Since 1995, the size of the largest devices has remained similar to the largest device shown in this picture. This size has proven to be convenient for packaging and assembling in large arrays. Development of Lincoln Laboratory's most recent scientific imaging devices has focused on advanced features; for example, use of orthogonal-transfer CCD technology; smaller pixel size; anti-blooming; ultradeep-depletion devices; and non-planar imagers.

Another important attribute of surveillance imagers is high sensitivity, which implies high (~100%) quantum efficiency and low read noise (which implies low output data rate). Search rate is another attribute that is often important for Department of Defense (DoD) applications. The combined requirements for high search rate and low read noise led us to use eight outputs in the 10-megapixel device in Figure 1. This device is used in the Air Force Ground-Based Electro-Optical Deep-Space Surveillance network and is a replacement for a vacuum-tube-based imaging technology that had been used in this system since the 1970s. The optics image size determined the size requirement for this device, which is approximately 9.7 cm in its diagonal measurement. This device is well suited for rapidly searching the sky for very faint objects and has been used very successfully to search for asteroids in the Lincoln Near-Earth Asteroid Research (LINEAR) program.

101 Megapixel CCD focal plane Figure 2. One-hundred-one–megapixel CCD focal plane fabricated in 1998 for the CFHT on Mauna Kea, Hawaii. (Photo: University of Hawaii.)

Astronomy telescopes have large optics that create large prime image areas and are used to look at dim objects; therefore, they have needs similar to those of defense surveillance CCDs. The array shown in Figure 2 was constructed for the Canada-France-Hawaii Telescope (CFHT) on Mauna Kea, Hawaii, in 1998. It is composed of twelve 8.4-megapixel imagers, for a total focal plane size of 100.7 megapixels. The physical size of this image array is about 12 × 18 cm, which at the time was probably the largest CCD focal plane in existence.

Today, the largest known astronomy CCD focal plane array, for the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) project at the University of Hawaii, is 1.4 gigapixels in size and measures about 40 x 40 cm (a picture of this FPA appears on the home page of the Advanced Imager Technology Group). This FPA was assembled from 60 devices, each about 5 x 5 cm in size, designed and fabricated at Lincoln Laboratory. Each device, known as an orthogonal-transfer array, uses the Laboratory-developed orthogonal-transfer CCD technology and is able to largely compensate for atmospheric distortions over the very large field of view of this telescope.

Other examples of Lincoln Laboratory's scientific and DoD CCDs are
  • A unique silicon imaging CCD device that was made in a slightly spherical shape using thin silicon membrane technology. The spherical shape allows the use of special wide field optics which have a non-flat image plane. The Space Surveillance Telescope, an Air Force facility to observe satellites in orbit, uses a focal plane of these imagers and was enabled by this technology.
  • A number of Lincoln Laboratory scientific CCDs have been used in satellites such as the NASA Chandra X-Ray Observatory and the Transiting Exeoplanet Survey Satellite. Discussion of these and other satellite mission examples are found in the space-based imager page.

 

top of page