How a Modern Camera Sensor Captures Light and Converts It to Data
This patent describes a camera sensor technology that combines light-capturing elements with a special circuit to read out the image data quickly and efficiently, all on a single chip.
Original patent title: “Active pixel sensor with intra-pixel charge transfer”
This patent describes a camera sensor technology that combines light-capturing elements with a special circuit to read out the image data quickly and efficiently, all on a single chip. Granted to California Institute of Technology in 1995 with 21 claims and 620 forward citations, and it is now in the public domain.
Key facts
Coverage
What does this patent actually cover?
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 (ClaimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 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.
The gap
What does this patent NOT cover?
- 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.
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
What made this novel
The innovation was integrating a small, efficient charge transfer mechanism (a CCD section) within each pixel of a CMOS sensor, allowing for faster and lower-noise readout than previous CMOS designs, while still benefiting from the cost and integration advantages of CMOS manufacturing.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Smartphone camera sensors (e.g., Apple iPhone, Samsung Galaxy)
Digital single-lens reflex (DSLR) and mirrorless camera sensors
Webcams
Security cameras
Automotive cameras
Why it matters
The bigger picture
This patent is foundational for the development of modern CMOS image sensors. These sensors became a key alternative to older CCD sensors, offering advantages in power consumption, manufacturing cost, and integration with other electronics. The technology enabled the widespread adoption of digital cameras in everything from smartphones to webcams and professional cameras.
Filed
January 28, 1994
Granted
November 28, 1995
Market context
Who's building on this
Companies in this space
The original assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →, 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.
Market impact
This patent helped pave the way for the widespread adoption of CMOS image sensors, which eventually surpassed traditional CCD sensors in many applications due to their lower power consumption, smaller size, and lower manufacturing costs. It enabled the integration of high-quality cameras into mobile phones and other portable devices, creating entirely new product categories and significantly expanding the digital imaging market.
Claim 1 — Plain English
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.
The clever bit
The innovation was integrating a small, efficient charge transfer mechanism (a CCD section) within each pixel of a CMOS sensor, allowing for faster and lower-noise readout than previous CMOS designs, while still benefiting from the cost and integration advantages of CMOS manufacturing.
What it does not cover
- 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.
Patent Journey
From filing to expiry
PatentBrief Score
Impact Score
Strong
Citation count
40/40
Highly cited
Claim breadth
14/20
Broad claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
0/20
Older than 20 years
Assignee scale
20/20
Major company or institution
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$82K – $262K
Midpoint $164K · expired or expiring · industry ×1.4
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
The original legal language
Original claims
21 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Fossum, E. R., Mendis, S., & Kemeny, S. E. (1995). How a Modern Camera Sensor Captures Light and Converts It to Data (U.S. Patent No. 5,471,515). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/5471515/cmos-active-pixel-image-sensor
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
Embed
Add this patent to your site
Drop this plain-English patent card into any blog post or article — free, no signup. It always links back to the full breakdown here.
<div data-patentlens-widget data-patent-number="US5471515"></div> <script src="https://patentbrief.org/embed.js" async></script>
Stay in the loop
Get a weekly digest of new patents.
One email per week. No spam. Unsubscribe anytime.
Keep exploring
Related patents you should know
US 4683195 · 1987
How to Make Billions of Copies of a DNA Segment
This patent describes the Polymerase Chain Reaction (PCR), a method to rapidly create many copies of a specific piece of DNA or RNA, enabling its detection and analysis.
Cetus Corp
US 8697359 · 2014
How to Edit Genes in Human Cells Using an Engineered CRISPR System
This patent describes an engineered CRISPR-Cas9 system for precisely cutting DNA in eukaryotic cells to change how genes work, opening the door for gene editing in complex organisms.
Massachusetts Institute of Technology
US 7657849 · 2010
How the iPhone's Slide-to-Unlock Gesture Works
Apple's 2010 patent describes unlocking a device by dragging a specific graphical image across the touchscreen along a predefined path, a gesture that became iconic with the original iPhone.
Apple Inc
US 4733665 · 1988
How Doctors Implant a Permanent Stent Using a Balloon
This patent describes the method for placing a permanent, expandable wire mesh tube inside a blood vessel or other body tube using a balloon-tipped catheter to widen it and keep it open.
Expandable Grafts Partnership
US 4405829 · 1983
How RSA Public-Key Encryption Keeps Digital Messages Secret
This patent describes the foundational RSA algorithm, a method for securely sending messages where anyone can encrypt a message using a public key, but only the intended recipient can decrypt it using a secret private key.
Massachusetts Institute of Technology
US 4575330 · 1986
How 3D Printers Build Objects Layer by Layer from Liquid
This patent describes the foundational method for 3D printing, where a machine builds a three-dimensional object layer by layer by hardening a liquid material with light or other energy.
UVP Inc
Semantically similar
You might also find these interesting
US 3792322 · 1974
How Buried Channel CCDs Move Data Deep Inside Silicon Chips
US 4131919 · 1978 · Eastman Kodak Co
The First Digital Camera's Core Technology
US 8493330 · 2013 · Apple Inc
How Touchscreens Precisely Align Signals to Detect Your Touch
US 4531203 · 1985 · Tokyo Shibaura Electric Co Ltd
How Flash Memory Cells Use an Erase Gate to Clear Data
More to explore
More in Consumer Electronics
US 7657849 · 2010 · Apple Inc
How the iPhone's Slide-to-Unlock Gesture Works
US 7479949 · 2009 · Apple Inc
How Touchscreens Understand Your Finger Swipes and Scrolls
US 4528643 · 1985 · FPDC Inc
How Stores Make Custom Products On-Demand with Remote Approval
US 7469381 · 2008 · Apple Inc
How Touchscreens Show and Snap Back When You Scroll Past an Edge
New to patents?
Common Questions
Frequently Asked Questions
What does How a Modern Camera Sensor Captures Light and Converts It to Data cover?
This patent describes a camera sensor technology that combines light-capturing elements with a special circuit to read out the image data quickly and efficiently, all on a single chip.
Who owns patent US 5471515?
California Institute of Technology owns this patent, granted in 1995.
When does this patent expire?
This patent has expired and is now in the public domain — anyone can use the invention freely.
What is patent US 5471515 cited by?
This patent has been cited by 620 later patents that build on its ideas.
What problem does this patent solve?
This patent is foundational for the development of modern CMOS image sensors. These sensors became a key alternative to older CCD sensors, offering advantages in power consumption, manufacturing cost, and integration with other electronics. The technology enabled the widespread adoption of digital cameras in everything from smartphones to webcams and professional cameras.
What does this patent NOT cover?
Image sensors that use only traditional CCD technology for both charge collection and readout across the entire chip.
Same assignee
More from California Institute of Technology
Patent monitoring