GB2477174A

GB2477174A - Right angled camera housing

Info

Publication number: GB2477174A
Application number: GB1016811A
Authority: GB
Inventors: Naveen Chawla
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-01-25
Filing date: 2010-10-06
Publication date: 2011-07-27
Also published as: GB201001152D0; GB201016811D0

Abstract

A system which comprises one or more fixtures 1,2, wherein each fixture forms at least one empty inner right angle shape and has at least one camera 8 attached to it in a known position and orientation. Two fixtures may be attached to each corner of a television display and may be backed by a magnet, ferrous metal, adhesive or suction pumps. The cameras may use fisheye lenses. The system may automatically calculate the TV screen size by using the camera on a first fixture and determining the pixel location of known features on a second fixture, or using an ultrasonic transmitter 4 and receiver 3. Based on the known position of each camera, the system may estimate a user's 3D viewing location and match this to the location of a virtual camera set relative to a virtual 3D environment. The system may estimate the 3D locations of stereoscopic glasses or devices 13,14 held/worn by the user. This system does not require the stereo calibration step that hinders multiple camera 3D tracking systems.

Description

A Stereo-Calibration-Less Multiple-Camera Human-Tracking System For Human-Computer 3D Interaction One of the problems of multiple-camera 3D tracking is stereo calibration. What is proposed is a system that does not require a stereo calibration step by the user or installer of the system.

In 3D human-computer interaction (e.g. with virtual object 1 in Fig.1), it is important to establish a 3D coordinate space relative to the screen (17 in Fig. 1). Normally one would perform a stereo calibration step to establish the position and orientation of the cameras in order to enable 3D tracking of objects located within viewing range of two or more of the cameras.

However for home use this step is cumbersome, and requires re-doing every time any camera is moved even slightly, for example by accident when someone brushes past.

What is therefore proposed first is the use of right-angled brackets such as 1 and 2 in Fig.1, which would be mounted on corners of the user's screen by the user, in line with the edges of the screen, via a self-attaching method, such as magnets, a magnet and a ferrous metal (one of which is attached to the screen by adhesive), adhesive or suction pumps. The size of the user's screen would then either then be input into the system by the user, or calculated automatically by the system by using at least one ultrasonic receiver such as 3 in Fig. 1 and transmitter such as 4 in Fig. 1 mounted on different brackets, and using a time-of-flight calculation to calculate the distance between the two, and hence deduce the size of the screen, or using at least one camera such as 5 in Fig. 2, to pick up two or more objects or features in known locations on the other bracket such as LEDs 6 and 7 in Fig. 2, and using their pixel locations on the camera (or cameras) to calculate, given the known information, the actual distance to those objects from that camera.

The cameras do not need be exposed as shown by 8 in Fig. 1. That is an under-the-hood drawing. The screen-corner-brackets cou'd typically provide casing for the cameras as denoted by 16 in Fig. 1 for discreetness and extra protection and security. The casing in front of the cameras would need to he transparent to whatever wavelengths of electromagnetic radiation the cameras need to detect, or could he transparent to those wavelengths exclusively.

Using screen-corner-mounted brackets is significantly better than using, for example, a single bar at the top of the screen because the user does not have to perform any kind of measurements to place them in a precise way. Also, the units allow for more compact packing of the system than a long bar would, allowing for more convenient transit, storage and stocking of the system.

The cameras used for 3D tracking, denoted by 8 in Fig. 1, would he pre-mounted on the brackets securely and in a precise way, so that their position and orientation in relation to their bracket is already known. This would then be used in conjunction with the calculation of the screen size as described above to deduce the position and orientation of the cameras in relation to the screen. The position and orientation of the cameras relative to the screen is sufficient information to deduce the 3D location, relative to the screen, of any tracked object in view of two or more of the cameras.

Therefore a second method of avoiding a stereo calibration step proposed here is to produce a television screen or monitor with cameras already mounted in accurately predefined and known locations and orientations relative to its screens, as denoted by 19 in Fig.3.

Typically, in order for realistic 3D interaction, all versions of the system would need to track, or estimate using tracking, either the 3D locations of the user's left and right eyes or a single compromise between the two, in order to place at least one virtual camera position (two if stereoscopic presentation is being used) in the virtual 3D world to match that location, and set its viewing frustum to the asymmetric pyramid shape that the user's viewing position (or each eye position respectively) would make with the corners of the screen if you were to draw a straight line from that position to each of the four corners of the screen at any given time. Example virtual camera frustums for a stereoscopic system with respect to the left and right eyes is denoted by 9 and 10 in Fig. 1. Markers mounted on the user's stereoscopic glasses such as LEDs 11 and 12 in Fig. 1 provide one way of estimating those positions. Another way would be tracking the users head and estimating the left and right eye positions that way. This requires a little more computation than tracking LEDs but would be far more desirable.

The system would also typically need to track another part of the user, or a device that the user is in control of, to enable interaction with the virtual world.

An example of such a user-controlled device is denoted by the proposed handsets 13 and 14 in Fig. 1. Markers such as LEDs 15 in Fig. 1 mounted on each device can provide a simpler way of tracking the device's position and orientation than tracking the device or user by itself.

The system is significantly beneficial in comparison to systems that require stereo calibration because it would be incredibly easy and quick for the user to set up.

A good way of increasing the range of view of the cameras is to use fisheye lenses on them.