FlatCam: Thin, Lensless Cameras Using Coded Aperture and Computation

Abstract

FlatCam is a thin form-factor lensless camera that consists of a coded mask placed on top of a bare, conventional sensor array. Unlike a traditional, lens-based camera where an image of the scene is directly recorded on the sensor pixels, each pixel in FlatCam records a linear combination of light from multiple scene elements. A computational algorithm is then used to demultiplex the recorded measurements and reconstruct an image of the scene. FlatCam is an instance of a coded aperture imaging system; however, unlike the vast majority of related work, we place the coded mask extremely close to the image sensor that can enable a thin system. We employ a separable mask to ensure that both calibration and image reconstruction are scalable in terms of memory requirements and computational complexity. We demonstrate the potential of the FlatCam design using two prototypes: one at visible wavelengths and one at infrared wavelengths.

Image and Depth Estimation with Mask-Based Lensless Cameras

“…(2) An alternating gradient descent-based refinement algorithm that jointly estimates the light distribution and depth map on a continuous domain. cameras avoid this problem by increasing the number of pinholes and allowing more light to reach the sensor [4], [8]- [11]. In contrast to a pinhole camera where only one inverted image of the scene is obtained through a single pinhole, the measurements captured through a coded-mask are a linear combination of all the pinhole images under every mask element.…”

“…In contrast to a pinhole camera where only one inverted image of the scene is obtained through a single pinhole, the measurements captured through a coded-mask are a linear combination of all the pinhole images under every mask element. To recover an image of the scene, we need to solve a computational image recovery problem [4], [8].…”

“…Such mask-based cameras offer an alternative design for building cameras without lenses. A recent example of mask-based lensless camera is known as FlatCam [4]. In contrast with a lens-based camera that is designed to map every point in the scene to a single pixel on the sensor, every sensor in a FlatCam records light from every point in the scene.…”

Single-shot diffuser-encoded light field imaging

“…Microlens arrays and attenuation masks have also been used without a main imaging lens to create very flat cameras for 2D imaging [37,5], since the lens function can be achieved in computation. Very small 2D cameras have also been created with diffractive optics and computation [36] using a purely wave-optics model.…”

FlatCam: Replacing Lenses with Masks and Computation

“…The FlatCam achieves the thin form factor by dispensing with a lens and replacing it with a coded, binary mask placed almost immediately atop a bare conventional sensor array. The image formed on the sensor can be viewed as 1 A longer version of the paper with additional results is available in [1]. a superposition of many pinhole images.…”