Photo Diode

The Geometry of Impossible Vision Standard photography relies on a predictable cone of light. A Pinhole Camera operates by allowing light to pass through a single point, projecting an inverted image onto a sensor. This creates the perspective we consider natural: objects appear smaller as they move further away. But this fixed geometry limits our ability to see past obstructions. To break this, we have to rethink the physical path light takes before it hits a sensor. By moving a single-pixel sensor across a wide physical area and varying its angle, we can simulate optics that don't exist in nature, effectively allowing a machine to "wrap" its vision around a central object. Mechanical Precision and the Balancing Act Building a camera that moves through space requires solving extreme mechanical challenges. A linear gantry moving fast enough to capture an image would vibrate so violently it would destroy the data. The solution is a spinning arm. This design maintains a constant velocity, eliminating the sudden accelerations that cause blur. The hardware involves a Photo Detector on a cart that travels the length of the arm, counterbalanced by a steel weight to prevent the assembly from shaking itself apart at high RPMs. To keep the wires from twisting into a knot, a Slip Coupling handles the electrical connection between the stationary base and the rotating computer, while a high-resolution Encoder tracks the arm's position to within fractions of a degree. Amplifying the Ghost of a Signal Capturing light with a single pixel at ten thousand readings per second creates a massive signal-to-noise problem. Unlike a standard camera that can take a long exposure, each measurement here is essentially instantaneous. The initial signal from the Photo Diode is so weak it is virtually indistinguishable from background electronic noise. Solving this requires a high-end Trans-Impedance Amplifier to boost the signal by a factor of 10 million. Without this specialized hardware, the resulting images are just gray static. Even with it, the software must perform heavy lifting, using linear algebra to map every timed reading back to a specific coordinate in a 2D image. Orthographic and Reverse Perspective Once you control the sensor's position and angle, the "rules" of reality become optional. By keeping the sensor pointed perfectly straight at all times, the camera produces an orthographic projection. In this mode, perspective vanishes; a foam head 100 feet away appears exactly the same size as one inches from the lens. Taking it further, we can create reverse perspective by pointing the sensor inward as it moves outward. This makes distant objects loom larger than those in the foreground, a visual effect that contradicts every instinct of human biology but proves the flexibility of computational imaging. Seeing Around the Obstacle The ultimate goal is the "ring camera" configuration. By pathing the sensor in a circle and angling it toward a central point behind an obstruction, the camera effectively peers around the edges of a barrier. When capturing a human face behind a wall, the camera doesn't just see the person; it sees them from five different angles simultaneously and flattens that data into a single frame. The result is a surreal, unfolded map of a human head—an authentic, if slightly haunting, look at what happens when you remove the physical constraints of a traditional lens.