Abstract: The invention is directed to a headgear with a holding device for a measuring unit, illuminating unit or viewing unit. The headgear has a headband and a frontal band and is mounted on the head of the wearer of the headgear. A base body is mounted on the frontal band and a bracket for holding the unit is attached to said base body by a clamping device. The clamping device is manually actuable between a fixing position wherein the bracket is movably fixed relative to the base body and a releasing position wherein the bracket is released so as to permit movement of the bracket in elevation relative to the base body. A detent device permits the bracket to be rotated relative to the base body while the clamping device is in the fixing position.

Abstract: An optical test chart for testing binocular vision. The chart has three lines of text, with the middle line printed or marked in letters or characters which have no polarizing effect. The line above this middle line is marked in letters or characters which have the effect of polarizing light reflected from them, in a plane of polarization in one direction, while the line below the middle line is similarly marked with letters or characters having the effect of polarizing reflected light but with the plane of polarization in a different direction at a substantial angle, preferably a right angle, to the direction of polarization caused by the upper line. The person whose vision is being tested views the test chart through polarizing spectacles, the spectacle in front of one eye having a plane of polarization corresponding to that of the upper line of text on the chart, and the spectacle in front of the other eye having a plane of polarization corresponding to that of the lower line of the text.