Edge-guided resolution enhancement in projectors via optical pixel sharing

Abstract

Imaging Lens 2 nd LCD (14x10.5) Scaling Lens d = 25, f = 30 Lens Array d = (7x5.4), f = 42 1 st LCD (14x10.5) Target High Resolution Enhanced Resolution Low Resolution I ne I e I v I Time Sequential Figure 1: Left: This illustrates the basic concept of decomposing a target high resolution image, I, to a high resolution edge image, I e and a complementary low resolution non-edge image, I ne . I e and I ne are then displayed in a time sequential manner to create an image with spatially varying resolution where edges are displayed at a higher pixel density than the rest of the image. We call this the edge-enhanced image, I v . I v is perceptually close to I. Middle: The image from the enhanced-resolution projector compared with a target high-resolution image and a low resolution image. Note that the edge-enhanced image is perceptually almost indistinguishable from the target high-resolution image. Right: A side view of our prototype enhanced-resolution projector that achieves 1024 × 768 edge-enhanced images by cascading two light modulator panels of 512 × 384 resolution (animated illustrations in the video). The numbers in the image are in millimeters. AbstractDigital projection technology has improved significantly in recent years. But, the relationship of cost with respect to available resolution in projectors is still super-linear. In this paper, we present a method that uses projector light modulator panels (e.g. LCD or DMD panels) of resolution n × n to create a perceptually close match to a target higher resolution cn × cn image, where c is a small integer greater than 1. This is achieved by enhancing the resolution using smaller pixels at specific regions of interest like edges.A target high resolution image (cn × cn) is first decomposed into (a) a high resolution (cn × cn) but sparse edge image, and (b) a complementary lower resolution (n × n) non-edge image. These images are then projected in a time sequential manner at a high frame rate to create an edge-enhanced image -an image where the pixel density is not uniform but changes spatially. In 3D ready projectors with readily available refresh rate of 120Hz, such a temporal multiplexing is imperceptible to the user and the edge-enhanced image is perceptually almost identical to the target high resolution image.To create the higher resolution edge image, we introduce the concept of optical pixel sharing. This reduces the projected pixel size by a factor of 1 c 2 while increasing the pixel density by c 2 at the edges enabling true higher resolution edges. Due to the sparsity of the edge pixels in an image we are able to choose a sufficiently large subset of these to be displayed at the higher resolution using perceptual parameters. We present a statistical analysis quantifying the expected number of pixels that will be reproduced at the higher resolution and verify it for different types of images.

A virtual pixel software and hardware technology to increase projector resolution

“…The fixed overlay approach has been referred to by numerous terms including superimposed projection [24] / superimposed displays [25], optical pixel sharing [26], and display supersampling [27]. This approach is exemplified by the work of Jaynes and Ramakrishnan's [12] using multiple projectors and Heide, et al's [13] and Lanman, et al's [14,15] demonstration of stacked LCD panels).…”

“…Sajadi, Gopi and Majumder [26] demonstrate a technique where this approach is used to only enhance a single sub-frame image's edges, with the remainder of the image being displayed as a second sub-frame, creating the appearance of a higher resolution. Ulichney, Ghajarnia and Damera-Venkata [30], alternately, compare movement-based (wobulation) and multi-projector approaches, demonstrating that the two have comparable performance.…”

A virtual pixel technology to enhance the resolution of monitors and for other purposes

“…A variety of work has been performed both in the fixed overlay and movement based categories. Fixed overlay approaches include superimposed projection [20] / superimposed displays [21], optical pixel sharing [22], and display super-sampling [23]. Movement-based techniques have included motor-based sub-pixel vibration [24], mirror-based [15] and simulated-movement [25] techniques.…”

Enhancing head and helmet-mounted displays using a virtual pixel technology

“…Prior work on overlaid coloration sources has included the use of optical pixel sharing [23], display super-sampling [24], and superimposition techniques for projectors [25] and conventional displays [26]. Techniques that incorporate movement have also been developed.…”