OSA Fall Vision Meeting Note

Zickler used apertures of different chromaticity to take pictures. Since aperture size determines the depth of focus, an image taken with a camera with different apertures will have different depths of focus for different color. This information allows the researchers to estimate the depth of different objects in the image.

Bank investigated different 3D display technologies. He focused on depth distortion. Left-right lateral movement on a stereo display appears forward and backward movement in depth. It may be an artifact caused by the current time-sequential display technique. He used a rotating wheel stimuli (disks of different disparity rotating about the fixation point) to measure the nulling depth and estimate the distortion.

Read showed that much disparity information n the retina is lost when disparity is encoded in V1. She used gratings modulated in depth (cf. Kontsevich & Tyler). V1 has on-off regions for luminance but same-disparity tuning for the whole receptive field. Therefore, some areas must integrate V1 cells to see gratings modulated in depth. The cell response for sinewave grating depends on the depth modulation, but not square wave. It is because that larger disparities is encoded by larger receptive fields. To design video codec, it is better to have high resolution monocular images with low resolution depth maps. The depth percept has even less information than V1. In addition, it is easier to detect horizontal grating than vertical grating at lower spatial frequencies.  She also measured the reverse correlation threshold for joined disparity and motion grating.  The reverse correlation threshold allows her o estimate the receptive size for disparity and motion. The RF tuned t different combinations of motion and disparity. It is unlikely to be MT neurons. So, Information is read out from V1, but it is not clear who read it.

Tsirlin from Wilcox 's lab talked about cross talk on perceived depth in 3D displays. Crosstalk=(leakage/signal)*100%.  Crosstalk reduce image quality, quality of depth and induce discomfort. She asked observer to estimate the depth of two bars with and without cross talk. Increase in cross talk reduced perceived depth. Significant reduction started at 4-8% cross talk.

Kazimi from 3D film innovation consortium taled about Hazardous stereography.  UK constraint disparity to be 4% positive (object in front of the background)  and 2% negative as safe zone. Depth setting changes with display size. 

Rudd. Lightness contrast with two contexts. The target disk is surrounded by an immediate surround and then on a large background. The radius of the surround has an effect on the perceived lightness of the target.  The matched target luminance peaks at certain physical luminance, suggesting a contrast gain control mechanism. 

VSS2012 Note

21.14 Mullen measured TvC functions for equilluminance Gabor target with luminance Gabor mask of orthogonal orientation. She found that the TvC function is facilitative for monocular viewing and suppressive for dichoptic viewing. Further studies showed that monocular viewing is color selective but the dichotopic viewing is not. She proposed that there are two different pathways for luminance-color gain control. A binocular summation model is used to explain the result.

This study is quite interesting as it shows binocular summation may alter the contrast gain control in the color vision mechanisms. I can immediately think about several experiments to exploit such binocular summation properties. What Mullen did was to put my thesis work in dichoptic viewing. Similarly, one can put noise in one eye and target in the other (i.e., Eskew’s stimuli); first order pattern in one eye and the second order in the other, half of the symmetry in one eye and the other half in the other. What we need is a good binocular summation model.

21.17 Brainard used an unsupervised network to simulate how the cortex label whether an input is from L-cone or M-cone. The simulated retina has different types of cones randomly distributed in the visual field. The algorithm is based on the assumption that neighboring cones of the same type tend to have a high correlation. while those of different types tend to have low correlation. After hundred of images, two distinct distributions appear and can be used to separate different cone types.

26.401 A noise masker can have two effects: one is to increase the variability and the other is to contribute to the mean excitation of the target filter. Baker & Meese wonders whether these two inputs are comparable. So, they measured TvC function with jittered Gabor pedestal (Jitter provided variability) and normal noise mask. The TvC funcion always merge at high contrast. They think that the two components are not additive.   

26.404 Geogeson & Wallis showed that the 3rd order derivative is necessary to identify the location of Mach Band.

31.12 There are two visualization talks in perceptual organization session. Maloney showed that the observers tend to underestimate the product of two probability values, that is, p(A&B)<P(A)P(B), when the probability were shown as pie graphs.

31.13 Resnik studied the correlation perception. He showed correlated data on a scatter plot, and measure much more correlation is needed for the observer to detect a difference in correlation. The result conforms Weber's law. A lot factors, such as color or brightness, has no effect on such relationship.   "Visualization is an interesting visual stimulus"

33.426 Vekser & Wilson showed that interocular distance judgment (i.e., second order configuration) on faces can actually be accounted for by the  two-dot separation paradigm. That is, facial configuration processing may be supported by early visual mechanisms.   

42.14 42.15. These two studies used a good paradigm to study the role of pSTS in face expression and face identity processing. They used a block design, one block has 5 pictures of the same person,  same expression; the second, same person,  different  expression; the third different person,  same expression; and the forth, different person,  different  expression. The differential activation between the blocks shows that pSTS is sensitive to facial expression.  

56.446 & 56.447 These two from Welchman's lab used fMRI to study cue combination in depth perception. There MVPC is quite special. The used two levels of two cues (and thus, four types of stimuli) in four different blocks to present two levels of surface slant. The MVPC is to classify slants, not the cues. This technical has a good potential in my own research as well.