Project Description
This project started in the Philips Technology Incubator. During this start-up phase a complete development environment was built including a validation box with FPGA board, ADC, DAC and analogue interfacing. The FPGA in the validation box runs clock-gated VHDL ported from an ASIC to the FPGA. The validation box can be configured and controlled by a microprocessor board with HID-mouse software stack, SPI debug stack and raw data monitor stack. The validation box’s interface connects to an analogue mouse board with laser drivers and photo diode amplifier. To evaluate the final product an evaluation kit was built, representing a fully functional mouse with plastic housing. A dedicated PC software tool programs these evaluation kits, executes scripts to evaluate and validate the ASIC, captures raw data and controls the microprocessor board and validation box.
Philips Laser Sensors introduced its first product on the market in September 2005, and was transferred from the Technology Incubator to Philips Lighting in January 2006. Since then a range of products has been introduced with a differentiation in tracking performance and power consumption.
After the market introduction and the mass-production start of the twin-eye laser sensor the focus of our group shifted to code optimisation, performance extension, power reduction, test methods and tools, documentation, application support, customer and partner relationship.

After the market introduction and the mass-production start of the twin-eye laser sensor the focus of our group shifted to code optimisation, performance extension, power reduction, test methods and tools, documentation, application support, customer and partner relationship.

Participation
This project is executed on site to enable close cooperation between the project team and the customer. It runs over 3 years.
Members from our group primarily participated in:
project management
architectural design
software design
analogue design
digital design
product testing (release, regression)
customer support

Technology
Most displacement sensors used in commercially available computer mice are based on an LED or laser in combination with a CCD camera. The LED or laser acts as a light-source that illuminates the surface over which the mouse is moved. The surface over which the mouse moves is scanned by a CCD camera, and a dsp calculates the displacement. The motion is detected by algorithms that derive motion vectors from the displaced image (LED), or the shift in speckles (laser).
Philips twin-eye laser technology exploits a phenomenon known as laser self-mixing, in which laser light reflected from the target surface re-enters the illuminating laser where it optically interferes with the emitted laser light. This interference effect, which depends on the frequency difference between the emitted and reflected radiation caused by motion of the target, results in power fluctuations in the laser that are detected by a photo-diode integrated into the sensor. The resolution is similar to that in far more expensive laser Doppler interferometers. By modulating the wavelength of the laser it is possible to detect the direction in which the target surface is moving as well as its speed, allowing continuous displacement vectors to be calculated. Eye-safety is insured by dynamic control of laser power and independent power-monitoring circuitry integrated into the device. Compared to other optical sensors like LED and CCD based devices, this twin-eye laser sensor has high resolution, consumes less power and can detect the movement of virtually any physical surface.
A major advantage of this system over other laser sensors on the market is that the optical pathways for the illuminating and reflected laser light are identical, which greatly simplifies the complexity and alignment of the optical components required. The use of the same laser component as both source and detector means that the detector is inherently aligned with the laser, increasing system resolution and sensitivity.
Philips Laser Sensors