Sensors Mag

Intevac Boosts Low Light Night Vision Sensing

September 1, 2005 By: Peter Adrian

This content is excerpted from Sensor Technology Alert and Newsletter, a sensor intelligence service published by the Technical Insights unit of Frost & Sullivan.

Intevac Inc. (Nasdaq: IVAC)--a key supplier of magnetic media sputtering equipment for the hard disk drive industry, and a developer and provider of extreme low light-level sensors, cameras, and systems for military, government, and commercial markets--has garnered the 'most innovative product award' at the fifth annual Soldier Technology Conference in Brussels, Belgium, for the company's patented extreme low light electron bombarded active pixel sensor (EBAPS).

A panel, including the program managers for soldier modernization programs in the United States, UK, France, Netherlands and Norway, were among the judges. The criteria for the award centered on products that reduce weight, bulk and power consumption; provide increased situational awareness; and reduce collateral damage.

The EBAPS sensor is an extreme low light digital sensor designed to provide compact size, light weight, and low power consumption for use in next-generation head-mounted night-vision systems. Digital output enables sensor fusion, symbology overlay, and image processing, which contribute to situational awareness. The EBAPS sensor is also targeted at commercial applications, such as industrial and scientific cameras.

Verle Aebi, president of Intevac's photonics technology division, told Sensor Technology that Intevac expects initial production and delivery of EBAPS sensors for a North Atlantic Treaty Organization (NATO) military user to take place in 2006.

Intevac develops and manufactures electro-optical sensors, cameras, and systems that designed to allow highly sensitive detection of photons in the visible and near infrared portions of the spectrum, enabling vision in extreme low light situations.

Intevac's laser illuminated viewing and ranging (LIVAR) target identification system consists of a near infrared extreme low light camera integrated with an eye-safe laser illuminator. Depending on the application, LIVAR can be utilized to identify targets at distances exceeding 20 kilometers.

Intevac's sources note that, while laser imaging has been used in limited applications, previous systems operated in infrared wavelengths that put observed and friendly forces at risk of severe optical damage (blinding). This danger resulted in a general ban on the use of the technique. However, Intevac's development of the transferred electron (TE) photocathode facilitated the realization of a high performance imaging sensor with the desired "single photon level" sensitivity in the eye-safe band .

Working on internal and government funding from the Air Force, Army and Defense Advanced Research Projects Agency, Intevac combined its TE photocathode with an electron-bombarded silicon imager technology to yield a small imaging sensor that could be retrofitted into existing forward looking infrared equipped sights or added to new systems.

LIVAR can complement forward looking infrared technology at ranges where targets can be detected by forward looking infrared, but not recognized. In this role, LIVAR can purportedly deliver the resolution to identify the detected targets at ranges extending beyond the identification range capabilities of currently fielded infrared cameras.

The company's NightVista camera was initially developed through the US Department of Commerce National Institute of Standards and Technology and is being advanced through development programs with the US Army.

The NightVista E1100 camera is a CMOS-based day/night video camera that reprocesses and optimizes low light images and is designed for low light level surveillance applications.

Imaging involves the capture and display of light or heat, which is infrared radiation, emitted or reflected from an object. A segment of the imaging market has evolved into focusing on specialized technology for capturing low light images. Low light imaging involves the capture and display of light at intensities of approximately one-millionth, or less, of daytime light levels. The US military has funded the development of night vision technology, which has evolved into the contemporary deployed 'Generation-III' night vision tubes.

Generation-III night vision tubes are typically placed in front of a user's eyes, in the fashion of a pair of binoculars, and produce a direct-view, 'green glow' image. However, Aebi noted that US and NATO military users are looking to transition from night vision goggle technology to miniaturized head-mounted night vision displays that are coupled with a low light vision camera. An imaging sensor with a digital output allows for image fusion and other image processing functions (such as image storage).

Intevac's sources note that the military is funding the development of next generation extreme low light imaging technology that provides digital video output.

Intevac develops imaging technology that combines the low light capability of Generation-III with silicon-based digital video technology. Aspects of Intevac's proprietary solutions include: advanced photocathode technology (the company is developing photocathodes that are engineered to optimize sensitivity at specific wavelengths ranging from the visible to the near infrared); use of lower power CMOS sensors; increased silicon sensor sensitivity (the company's technology purportedly allows CMOS and charge coupled device (CCD) sensors to capture the accelerated electrons emitted from the photocathode more efficiently); and compact, ultrahigh vacuum sensor packaging (which allows for combining a megapixel-imaging chip with photocathodes in a package that is approximately one inch square and one quarter inch thick).

Aebi explained that Intevac's photocathode, which essentially converts the photon image to an electron image that bombards the CMOS or CCD sensor, allows the semiconductor image sensing chip to detect the individual, high energy electrons, which provides the photon sensitivity required for low light level detection.

The intensified digital video sensors under development by Intevac for military and commercial applications include: the electron bombarded charge couple device (EBCCD); and the EBAPS. The EBCCD sensors tend to be used for specialized applications. The EBAPS, which contains a CMOS sensor, is a low power device which allows for more on-chip functionality and is more suitable than the EBCCD for mobile applications.

The EBCCD sensor has a transparent glass window through which photons are focused onto a III-V semiconductor photocathode. When photons strike the photocathode, electrons are emitted into a vacuum cavity. The electrons are then electrically accelerated into a CCD array that outputs a high resolution, low noise video signal. Gain is achieved through the electron bombarded semiconductor gain process in silicon.

The EBCCD sensors are manufactured utilizing Intevac's patented TE photocathode technology for use with actively illuminated, eye-safe laser imaging applications. Such devices function in the near infrared (950 nm to 1650 nm) wavelength range and can achieve thermally stable quantum efficiencies of greater than 30%.

The EBAPS imaging sensor incorporates the same basic technology, but uses a CMOS imager instead of a CCD chip. The EBAPS, in its current version, has 1.3 million pixels, and uses a gallium arsenide photocathode that is identical to that employed in Generation-III image intensifiers. The EBAPS can be mated with different photocathodes to provide low light imaging capability for a variety of applications from nighttime surveillance to fluorescence microscopy.

Aebi explained that low-light image sensors, which work in the visible to close near-infrared range, can complement microbolometer, pyroelectric, or thermopile type thermal imaging detectors, which detect blackbody radiation and work in the spectrum of around 8 micrometers to 14 micrometers. He noted that the US Army is looking at combining a low-light camera and a thermal imaging camera (containing a microbolometer detector) to fuse images and provide a soldier with enhanced situational awareness at night.

Intevac is working on increasing the resolution and sensitivity of their low light image sensors.

According to Frost & Sullivan's North American Image and Optoelectronic Color Sensors Market research service (published August 2003), North American revenues (encompassing the United States, Canada, and Mexico) for CMOS image sensors are projected to reach about $602.4 million (representing 74.9 million units) in 2009. At that time, the distribution of the overall North American image sensor revenues by end-user segment is expected to be: digital still cameras--28.5%; mobile phones--16.5%; optical mice--12.3%; PC cameras--10.2%; other (scientific and semiconductor equipment)--0.4%; machine vision--7.7%; other consumer (handheld devices, video games, personal digital assistants)--6.4%; security and surveillance--7.4%; bar code readers--5.4%; medical--3.8%; and automotive--1.4%.

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