Binocular overlap: Difference between revisions
Created page with "==Introduction== thumb|Figure 1. Human binocular overlap. (Image: David Johnson, University of Utah) File:Eyepieces with no binocular overlap...." |
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[[File:Binocular rivalry.png|thumb|Figure 5. Binocular rivalry caused by a partial-overlapping visual system. (Image: roadtovr.com)]] | [[File:Binocular rivalry.png|thumb|Figure 5. Binocular rivalry caused by a partial-overlapping visual system. (Image: roadtovr.com)]] | ||
Binocular overlap is the overlapping region between the two eyes of a stereoscopic vision system. It is a term that describes the shared space that can be seen by both eyes as opposed to by just one of the eyes (Figure 1). It is different from the visual field, which is defined as the area of space seen by either eye at a single instant. In a virtual reality (VR) environment, the binocular overlap area is the region where true stereoscopy is produced. According to Mon-Williams et al. (1993), “the HMD attempts to simulate binocularly overlapped images so that the fusion of disparate images can create the illusion of a three-dimensional world.” <ref name=”1”>Boger, Y. (2016). Understanding binocular overlap and why it’s important for VR headsets. Retrieved from https://www.roadtovr.com/understanding-binocular-overlap-and-why-its-important-for-vr-headsets/</ref> <ref name=”2”>Virtual Worldlets. Binocular Overlap. Retrieved from http://www.virtualworldlets.net/Resources/Dictionary.php?Term=Binocular%20Overlap</ref> <ref name=”3”>Fuchs, P. (2017). Virtual Reality Headsets - A Theoretical and Pragmatic Approach. CRC Press</ref> <ref name=”4”>Mon-Williams, M., Wann, J.P. and Rushton, S. (1993). Binocular vision in a virtual world: visual deficits following the wearing of a head-mounted display. Ophthalmic and Physiological Optics, 13: 387-391</ref> | Binocular overlap is the overlapping region between the two eyes of a stereoscopic vision system. It is a term that describes the shared space that can be seen by both eyes as opposed to by just one of the eyes (Figure 1). It is different from the visual field, which is defined as the area of space seen by either eye at a single instant. In a [[virtual reality]] (VR) environment, the binocular overlap area is the region where true [[Stereoscopic|stereoscopy]] is produced. According to Mon-Williams et al. (1993), “the HMD attempts to simulate binocularly overlapped images so that the fusion of disparate images can create the illusion of a three-dimensional world.” <ref name=”1”>Boger, Y. (2016). Understanding binocular overlap and why it’s important for VR headsets. Retrieved from https://www.roadtovr.com/understanding-binocular-overlap-and-why-its-important-for-vr-headsets/</ref> <ref name=”2”>Virtual Worldlets. Binocular Overlap. Retrieved from http://www.virtualworldlets.net/Resources/Dictionary.php?Term=Binocular%20Overlap</ref> <ref name=”3”>Fuchs, P. (2017). Virtual Reality Headsets - A Theoretical and Pragmatic Approach. CRC Press</ref> <ref name=”4”>Mon-Williams, M., Wann, J.P. and Rushton, S. (1993). Binocular vision in a virtual world: visual deficits following the wearing of a head-mounted display. Ophthalmic and Physiological Optics, 13: 387-391</ref> | ||
There are different amounts of binocular overlap required in a VR experience depending on the distance of focus. For long distances, a lesser degree of binocular overlap is necessary compared to close-up objects. In this case, a high degree of binocular overlap is needed to achieve realism. <ref name=”2”></ref> | There are different amounts of binocular overlap required in a VR experience depending on the distance of focus. For long distances, a lesser degree of binocular overlap is necessary compared to close-up objects. In this case, a high degree of binocular overlap is needed to achieve realism. <ref name=”2”></ref> | ||
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Binocular overlap plays an important role in depth perception. When an object is seen, each eye rotates so the object is observed in the same location in both views. The relative angles of the eyes provide an estimate of how far away the object is located. If the object being observed is far away, the angle in which it is seen by both eyes is almost the same; however, if the object is close, the angles will be different. <ref name=”1”></ref> <ref name=”5”></ref> | Binocular overlap plays an important role in depth perception. When an object is seen, each eye rotates so the object is observed in the same location in both views. The relative angles of the eyes provide an estimate of how far away the object is located. If the object being observed is far away, the angle in which it is seen by both eyes is almost the same; however, if the object is close, the angles will be different. <ref name=”1”></ref> <ref name=”5”></ref> | ||
For virtual reality application, head-mounted display (HMD) manufacturers can increase the overall horizontal and diagonal field of view (FOV) of the VR headset by creating partially overlapped systems. <ref name=”6”>Sensics. How binocular overlap impacts horizontal field of view. Retrieved from http://sensics.com/how-binocular-overlap-impacts-horizontal-field-of-view/</ref> | For virtual reality application, [[head-mounted display]] (HMD) manufacturers can increase the overall horizontal and diagonal [[field of view]] (FOV) of the VR headset by creating partially overlapped systems. <ref name=”6”>Sensics. How binocular overlap impacts horizontal field of view. Retrieved from http://sensics.com/how-binocular-overlap-impacts-horizontal-field-of-view/</ref> | ||
==Binocular overlap in VR HMDs== | ==Binocular overlap in VR HMDs== | ||
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However, if the VR HMD manufacturer decided to install eyepieces with 75% horizontal overlap (called partial overlap) the resulting binocular horizontal field of view would be 60 degrees. The overlapping region would encompass 36 degrees (75% of 48 degrees); adding to this the 12 degrees that are just shown in the left eyepiece, plus the 12 degrees only shown by the right eyepiece (Figure 4), and the 60-degree horizontal FOV is reached. Converting this number to the diagonal field of view gives a total of 70 degrees, which is larger than the diagonal field of view obtained when using 100% overlap. <ref name=”1”></ref> | However, if the VR HMD manufacturer decided to install eyepieces with 75% horizontal overlap (called partial overlap) the resulting binocular horizontal field of view would be 60 degrees. The overlapping region would encompass 36 degrees (75% of 48 degrees); adding to this the 12 degrees that are just shown in the left eyepiece, plus the 12 degrees only shown by the right eyepiece (Figure 4), and the 60-degree horizontal FOV is reached. Converting this number to the diagonal field of view gives a total of 70 degrees, which is larger than the diagonal field of view obtained when using 100% overlap. <ref name=”1”></ref> | ||
Indeed, a wider field of view is one of the advantages of using partial overlap. This means a greater level of immersion can be realized. Another advantage is an improved aspect ration. Following the example provided above, the original aspect ratio was 4:3. When using 75% overlap, the aspect ration became 5:3, making it more suitable for viewing widescreen content. <ref name=”1”></ref> | Indeed, a wider field of view is one of the advantages of using partial overlap. This means a greater level of [[immersion]] can be realized. Another advantage is an improved aspect ration. Following the example provided above, the original aspect ratio was 4:3. When using 75% overlap, the aspect ration became 5:3, making it more suitable for viewing widescreen content. <ref name=”1”></ref> | ||
However, partial overlap can have its disadvantages in a virtual reality headset such as binocular rivalry. If there is an object that is partially in the binocular overlap region and partially in a region exclusive to one of the eyes (Figure 5) it will be fully visible by one of the eyes and only partially by the other. If a user looks through both eyepieces at the same time, he might notice the border on the field of view of one of the eyes caused by the object's location, and this might be distracting. Instead of seeing a summation of the two images, the user’s perception will switch from one image to the other. <ref name=”1”></ref> | However, partial overlap can have its disadvantages in a virtual reality headset such as binocular rivalry. If there is an object that is partially in the binocular overlap region and partially in a region exclusive to one of the eyes (Figure 5) it will be fully visible by one of the eyes and only partially by the other. If a user looks through both eyepieces at the same time, he might notice the border on the field of view of one of the eyes caused by the object's location, and this might be distracting. Instead of seeing a summation of the two images, the user’s perception will switch from one image to the other. <ref name=”1”></ref> | ||
