You can freely build on How a Modern Camera Sensor Captures Light and Converts It to Data

What this patent covers

The patent describes an imaging device, like a digital camera sensor, built on a single silicon chip using a common manufacturing process (CMOS). Each tiny picture element, or "pixel cell," has a photogate (Claim 1) that collects light and turns it into an electrical charge. This charge is then moved within the pixel by a small charge coupled device (CCD) section (Claim 1) to a sensing node. From there, a CMOS readout circuit (Claim 1) with an output field effect transistor (Claim 1) converts the charge into a voltage signal that can be read by the camera. For example, when light hits a pixel, the photogate gathers the light's energy, which is then quickly shifted by the CCD part to the readout circuit, allowing the camera to process the image.

What is now free to use

All 0 claims of US 5471515 are in the public domain. Specifically:

The 0 dependent claims add narrowing limitations and are also free.

What is NOT covered

Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.

• Image sensors that use only traditional CCD technology for both charge collection and readout across the entire chip.

• Sensors where the charge is read out directly from the photogate without an intermediate charge coupled device section within the pixel.

• Image sensors that do not use a complementary metal oxide semiconductor (CMOS) circuit for the pixel's readout.

• Sensors that rely on different charge accumulation mechanisms other than a photogate.

• Pixel designs where the charge transfer and readout are handled by entirely separate, off-chip components.

Who is building on this today

The original assignee, California Institute of Technology, licensed this technology. Companies like Sony, Samsung, Omnivision, and Canon are major players in the CMOS image sensor market, continuously developing and improving upon the fundamental principles laid out in patents like this one. Many startups also leverage advanced CMOS sensor designs for specialized applications like medical imaging or autonomous vehicles.

Products built on expired version of this technology

How to cite this patent in your documentation

California Institute of Technology. US Patent 5471515. Active pixel sensor with intra-pixel charge transfer. Granted 1995, expired 2014. Now in the public domain.

Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.

PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.