Phase I Sensor Module

Phase I Sensor Module images

Distant Focus designed and fabricated the sensor module for the AWARE 2 camera. This was both an electronic and mechanical design challenge. Unlike conventional camera systems, this design required that the image sensor (not the optic) move with micron level precision to adjust focus. Additionally, the geometry of the AWARE camera allowed very little lateral space between cameras requiring novel mechanical and electronic designs.

The sensor was built on a rigiflex cable which was routed through the focus mechanism drive mechanics to act as a strain-relief. The sensor flex portion is attached to a precision bushing system that is driven by a finely threaded screw that itself is turned by another screw to improve the motion precision. The system was initially focused manually and later retrofitted with electronic focus using a servo and a driver rod. This proved to be extremely useful because it allowed for development of an autofocus algorithm and proved that the AWARE cameras can have a variety of focal distances in the scene and still produce a single scene with smooth seams between sensors.

The mechanics for the sensor needed to be very robust to maintain positional accuracy during focus actuation while causing the sensor flex to move appropriately. Each complete sensor module weighed 42 grams for the AWARE 2 prototype.

Phase II Sensor Module

Phase II Sensor Module images

To reduce the volume required for the optical design, the sensor modules needed to have a narrower profile. In addition, to reduce the overall system mass, the weight needed to be reduced significantly. To do this, the optical design was changed to use a moving optical element instead of moving the sensor, and the sensor module was completely redesigned.

Allowing the sensor to remain stationary removed the need for the precision bushing system. The sensor also did not need to be on a flex cable anymore. After exploring some simple options, it was determined that the sensor module profile had to be reduced as much as possible in order to maximize system performance. To achieve this, Distant Focus designed an injection-molded 3-dimensional circuit that allows all of the electronics to be positioned behind the sensor itself. DFC also developed novel assembly techniques that allowed for efficiently producing the thousands of sensor modules that were needed for the full AWARE program.

To move the lens focus elements for the AWARE 10 sensor module, a custom focus driver was used which attaches to the sensor module and pushes against a 'plunger' that moves the lens carriage. The sensor module and focus driver together had a small enough profile to fit behind the micro-optics barrel without causing any increase in the system volume.

Another useful feature of the Phase II sensor module is the aluminum heatsink which directly contacts the back of the sensor. This allows the heat generated by the sensor to be transferred very efficiently to the metal outer housing of the module and also allows for cooling the sensor for low-noise applications. The sensor was successfully cooled and run below -30 °C.

AWARE OVERVIEW

Back to the overview page for the AWARE camera systems.

System Integration

The AWARE system integration for both the Phase I and Phase II prototypes consisted of mounting the optical assembly, designing compact electronics modules, mounting the electronics, thermal management, and designing outer covers. Due to the large number of sensors in each system, special attention needed to be paid to assembly strategy, and this was also a major concern during design.