Reynard has developed a proprietary photolithography deposition technique that allows the placement of multiple filters on a substrate without a gap or overlap between filters. Removing the gap allows for more surface area for the filter and minimizes diffraction edge effects when filtering light. Overlapping filters has been the most common approach to exclude a gap; however, the overlap again reduces the filter surface area and can still cause unwanted edge effects. An example of use is in the 3-color Bayer filter, or similar, shown below, where color filters are placed just above detector pixels. Any diffraction patterns or stray light can affect the signal reaching the detector. A gapless deposition technique eliminates these anomalies.
This technology is best utilized when creating sensor windows at the wafer level. Many gapless multiple-window arrays can be deposited on a wafer substrate. After the wafer is tested for compliance, it is diced to produce the individual sensor windows. Any deposition material or filter design can be implemented in conjunction with this photolithography processing technique. An example of a gapless 3-band color filter is shown below.
3-band gapless filter
The same gapless photolithography technique can be applied to a wafer level packaging window for sensors. In this configuration, multiple multi-element filters are created on a single substrate. Each filter can then be diced and applied to a sensor, dramatically reducing the per filter cost to manufacture in high volume. As shown in the image below, large filter test areas can be defined that spatially represent the smaller sensor filters. Testing prior to dicing allows the customer to have confidence that the smaller filters meet their specifications.
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