High dynamic range

About: High dynamic range is a research topic. Over the lifetime, 4280 publications have been published within this topic receiving 76293 citations. The topic is also known as: HDR.

HDR image encoding and decoding methods and devices

Abstract: An image encoder includes an input for a high dynamic range input image (M_HDR); an image grading unit arranged to allow a human color grader to specify a color mapping from a representation (HDR_REP) of the high dynamic range input image defined according to a predefined accuracy, to a low dynamic range image (Im_LDR) by a human-determined color mapping algorithm. The image encoder is configured to output data specifying the color mapping (Fi(MP_DH)). Further, the image encoder includes an automatic grading unit configured to derive a second low dynamic range image (GT_IDR) by applying an automatic color mapping algorithm to one of the high dynamic range input image (M_HDR) and the low dynamic range image (Im_LDR).

Progress in Design of Improved High Dynamic Range Analog-to-Digital Converters

Abstract: We describe several improvements that are being pursued to improve the dynamic range of lowpass phase modulation-demodulation (PMD) analog-to-digital converters (ADC). The existing ADC has been tested at sampling frequencies up to 29.44 GHz; a 89.15 dB signal to noise ratio (SNR) is achieved for a 10 MHz sinusoidal input, with the noise being measured in a reference 10 MHz bandwidth in the decimated band. The first improved approach involves a multi-rate ADC where the modulator sampling frequency is increased in multiples of the decimation filter clock. We have tested the multi-rate ADCs at sampling frequencies up to 46.08 GHz and 29.44 GHz for chips fabricated using the 4.5 and 1 kA/cm2 fabrication processes respectively. For a single channel ADC, with a 9.92 MHz sinusoidal input, sampled at 29.44 GHz, the SNR is 83.93 dB in a reference 10 MHz bandwidth. The spur-free dynamic range (SFDR) is 95 dB. In another improved architecture, called the quarter-rate ADC, the modified quantizer quadruples the input dynamic range by distributing the input in a cyclical fashion to four output channels, each operating at a quarter of the fluxon transport rate. This enables quadrupling the synchronizer channels, providing an opportunity for up to 12 dB performance enhancement. A parallel counter following the multi-channel synchronizer converts the differential code to a multi-bit binary code, which is further processed by the decimation filter. A prototype version of this ADC with a two channel synchronizer, fabricated using the 4.5 kA/cm2 process, has been tested up to a sampling frequency of 25.6 GHz. For a 10 MHz sinusoidal input, the SNR is 82.54 dB, with the noise measured in a reference 10 MHz bandwidth. We are also designing a subranging ADC with two PMD front-ends. Simulation results promise greater than 20 dB performance enhancement.

High-dynamic-range laser range finders based on a novel multimodulated frequency method

Abstract: A continuous-wave phase-shift laser range finder employs a novel multimodulation frequency method associating an undersampling analog-digital converter (ADC) with digital synchronous detection. This presentation greatly improves measured phase accuracy and reduces prior art scheme complexities. The novel patented design includes one phase-lock-loop (PLL) chip to produce a multimodulation frequency, one analog-to-digital converter operating at a low sampling rate, and an effective algorithm to calculate the final distance, which has encoded computing codes, and is implemented into compact computing circuits but without mixers and redundant components. The experimental results prove that a nonambiguity range is easily achieved to 1.5 Km when the modulation frequency is operated at 0.1 MHz. The measured accuracy approaches 2.9 mm using the same apparatus when the modulation frequency is tuned to 14.5 MHz. Dynamic range can reach 5.2×105 without a very high modulation frequency below 15 MHz, as revealed by a detailed analysis.

Content metadata enhancement of high dynamic range images

Abstract: Image data is encoded for distribution in a lower bit-depth format The image data has a range that is less than a maximum range and is mapped to the lower bit depth format using a mapping such that a ratio of a range of the lower bit depth representation to a maximum range of the lower bit depth representation is greater than a ratio of the range of the image data to a maximum range of the image data Metadata characterizing the mapping is associated with lower bit depth representation The metadata may be used downstream to reverse the mapping so that tonal detail is better reproduced

An optimal tone reproduction curve operator for the display of high dynamic range images

Abstract: We present a new tone mapping method for the display of high dynamic range images in low dynamic range devices. We formulate high dynamic range image tone mapping as an optimisation problem. We introduce a two-term cost function, the first term favours linear scaling mapping, the second term favours histogram equalisation mapping, and jointly optimising the two terms optimally maps a high dynamic range image to a low dynamic range image. We control the mapping results by adjusting the relative weightings of the two terms in the objective function. We also present a fast and simple implementation for solving the optimisation problem. We present results to demonstrate that our method works very effectively.