GB2116334A

GB2116334A - Eye follower

Info

Publication number: GB2116334A
Application number: GB08206373A
Authority: GB
Inventors: Keith Christopher Hobbs
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1982-03-04
Filing date: 1982-03-04
Publication date: 1983-09-21
Also published as: GB2116334B

Abstract

Patent No. 1581018 describes a so-called eye follower, in which a TV camera views an operator's eye. The image of that eye is analysed and the result of the analysis indicates the direction in which the operator is looking. This result generates an output which can be used to operate a peripheral device. This is usable to enable a disabled person to control operations to be performed. In such a system some inaccuracies may occur due to minor head movements or an initial misalignment. To overcome this, when the user's eye (10) is viewing a screen (11) bearing indications of the desired control functions, a closed loop is set up. For this, the output of the eye follower (13) is applied to the screen (11) so that the user can see if it is correct. If it is not, he adjusts, via a manual input (14) or a calibration subroutine, the output of the eye follower until the latter coincides with the intended viewing point. The control function output from the eye follower is only effective when this adjustment - or confirmation - of the setting occurs. <IMAGE>

Description

SPECIFICATION Eye follower This invention relates to a man-machine interface which uses optical coupling to the human eye.

In our Patent Specification No. 1 581018 (K. C.

Hobbs 2) we have described and claimed a socalled eye follower, which is an arrangement which looks at an operator's eye by a TV camera, determines in which direction the operator is looking by analysing the shape of the image, and controls appropriate outputs in response to the operator's gaze. This has application for the provision of communication and control for disabled persons, and also for industrial and other control functions.

Figure 1 of the attached drawing illustrates th6 general principle of the eye follower. Here the operator's eye 1 is shown looking at a screen 2, with a TV camera 3 looking at the operator's eye.

The output of the camera 3 is applied to an eye detector circuit 4 which determines the position and shape of the eye. Its output is applied to an iris detector and analyser 5, which assesses from the characteristics of the image the direction in which the eye is looking. An output indicative of this direction is applied to an output controller 6, which has a separate input from a screen information store 7.

Thus from a combination of its two inputs, the controller determines at which part of the screen the operator is looking, and on the basis of this determination it covers the operation appropriate to the region of the screen 2 at which the operator is looking. As can be seen from the second output from the controller 6, the contents of the screen information store can be updated during operation.

The human eye has a relatively simple geometric form which is consistent in shape, size and colour contrast. It is possible to determine in which direction a person is looking even when his eye is partly obscured by an eyelid by mentally analysing the shape of the visible iris. When viewed directly along the line of sight the iris appears circular, and when viewed from another direction it appears elliptical, the degree of eccentricity and the elevation of the minor axis varying with the direction of vision and the viewing angle. As the shape is simple, it can readily be identified and analysed via the TV camera. Thus a two-dimensional TV image of the subject's eye is analysed to determine the eccentricity and elevation of the ellipse formed by the eye.These parameters determine the direction of vision, and this with the information presented to the user enables the eye follower to operate peripheral devices in response to the operator's gaze.

Such an arrangement may be subject to some lack of accuracy due to minor head movements or misalignments of the equipment, and it is an object of the invention to provide an arrangement in which such inaccuracies are dealt with.

According to the invention there is provided an electro-optical man-machine interface arrangement, which includes a television camera aimed at an operator's eye such as to produce an image of that eye when the latter is aimed at any desired position on a viewing screen, an eye recognition circuit which detects the position of the eye's image in the output from the camera, a shape analyser which determines from the shape of the eye image the direction in which the eye is looking, a feedback circuit connected to the viewing screen and on which an indication is produced indicative of the said direction as determined by said analyser, so that the operator can see the difference if any between his intended viewing point and the point to which the analyser output corresponds, and adjustment means whereby the operator can correct the analyser output so that it corresponds to the desired viewing point, and an output from the analyser for exercising a control influence appropriate to the intended viewing point.

An embodiment of the invention will now be described with reference to Fig. 2 of the accompanying drawings.

Here we see the eye 10 viewing the screen 1 1, and being itself viewed by a TV camera 12 whose output is analysed by an eye follower network 13, which is assumed to follow the principles set out with reference to Fig. 1, above. The output from the block 13 in addition to being sent to the controlled function (not shown) is applied to the screen 11. In some cases, as indicated above, some inaccuracy in the output of the block 13 may be present. Thus although the eye is actually looking at the point A the eye follower's output indicates that the latter has "assumed" that the eye is looking at point B. In such case the operator makes an adjustment via an input 14 to the eye follower block 13, which adjusts the input of the block 13. Hence the information fed back to the screen is adjusted, and with it the control output.

This latter only becomes effective when the points A and B actually coincide, so that the eye follower has correctly determined the operator's line of signal.

The adjustment can be effected in many ways, either by hand operation or under optical control using a calibration subroutine.

In a control system using eye follower techniques, one of the options available in the operations of the displays includes "Recalibration." When this is selected the output displays a single white point in the centre of the screen. The operator stares at this dot, which is now allowed to move under control of the output controller. If the device is calibrated correctly the dot remains stationary. However, if the machine is misaligned the dot moves to a new position depending on the degree of misalignment. The eye follows the dot and the process is repeated. Eventually the dot will disappear off the screen in the direction of misalignment. The device automatically corrects for the error and repeats the procedure if required until the dot has remained within the field of view for an acceptable period of time, depending on the response time of the device.

Claims

1. An electro-optical man-machine interface arrangement, which includes a television camera aimed at an operator's eye such as to produce an image of that eye when the latter is aimed at any desired position on a viewing screen, an eye recognition circuit which detects the position of the eye's image in the output from the camera, a shape analyser which determines from the shape of the eye image the direction in which the eye is looking, a feedback circuit connected to the viewing screen and on which an indication is produced indicative of the said direction as determined by said analyser, so that the operator can see the difference if any between his intended viewing point and the point to which the analyser output corresponds, and adjustment means whereby the operator can correct the analyser output so that it corresponds to the desired viewing point, and an output from the analyser for exercising a control influence appropriate to the intended viewing point.

2. An electro-optical man-machine interface, substantially as described with reference to Fig. 2 of the accompanying drawing.