A facsimile scanning method for converting a video signal, generated by opto-electronic scanning of an original copy, into a bilevel black/white signal in facsimile reproduction. In the black/white recording of colored originals in which both the background and the information can be white, black, grey or colored, white/grey (colored)/black transitions in the original are frequently not picked up correctly so that information is lost in the copy. The invention solves this problem by recording colored, grey or black areas in the original as "white" with black boundary lines, by means of suitable electronic circuits. If the colored area in the original is a background area without information content of its own but containing a black item of information (letter), the legibility of the black letter in the area is increased in the copy by reproducing the background area as "white". On the other hand, the background area remains recognizable in the copy with respect to the white of the paper by virtue of its surround. If the colored area in the original, however, is itself an item of information, e.g. a broad letter, the line-boundary according to the invention causes at least the contour of the letter to be recorded in the copy, making the letter legible. In general, black areas in the original can be reproduced in the copy as white areas with black surround. This has the advantage that overheating of thermal print of needle print recording devices is avoided due to the reduced black component in the copy.

Methods for converting a video signal into a black/white signal

A method and apparatus for determining or adjusting a projecting direction of a light beam emitted from an automobile headlight is provided. In a first aspect of the present invention, the peripheral region of a light beam is used in determining its projecting direction. In particular, a region definable in a light pattern of the projected beam having a proportionality relation between log S and I, where S indicates the value of an area having light intensity I or above, is determined and its outer contour or any predetermined point in the contour is used in determining the projecting direction. In a second aspect, apparatus for determining a projecting direction of a light beam emitted from an automobile headlight includes an indicator which automatically indicates a predetermined position of a light pattern of the light beam projected. In a third aspect, there is provided a system for automatically adjusting a projecting direction of a light beam if it deviates from a predetermined direction using a motor engageable with a mounting structure of the headlight.

Light destribution of headlight beam

A video signal produced by picking up the light image of light projected upon a screen is quantized by a plurality of voltage comparators grouped in pairs and applied with different reference voltage levels. One of the outputs of comparators of respective pairs is inverted in an orderly manner and then synthesized with the rest of the outputs to produce a dark and bright stripe signal which is displayed on a video display device to form a radially discrete annular pattern representative of equibrightness curves.

Method and apparatus for measuring the distribution of a light field about the optical axis of a light source

The headlamp of the automobile is a very important device for the safety of driving in the dark. Therefore, the distribution of the light designed to provide forward and lateral illumination needs to meet the requirements of various regulations. Traditional measurement of the distribution has been based on a point-by-point approach using a goniophotometer. In this paper, an imaging photometer is developed by combining a regular digital camera and a high dynamic range imaging technique to achieve faster and more complete measurement of the entire distribution. The experimental results indicate that errors of the measurements are within 10% of the true values, which is better than the 20% requirements of the industry.

Fast measurement of automotive headlamps based on high dynamic range imaging

The dimensions and light output of a beam in a shadow mask cathode-ray tube are determined by means of an optical system 7 focussed on a phosphor dot to pick up and record the light generated by a ray 4 passing through a single aperture 6 in the shadow mask 2. The cathode-ray beam 1 is moved so that the whole cross-section of the beam passes the aperture 4. The detected light outputs are plotted to provide an accurate representation of the whole beam. Repeating the procedure for each gun gives a precise record of the misconvergence of the beam

Method and apparatus for determining beam dimensions at the screen of a shadow mask cathode-ray tube

Automobile headlamp illumination is of concern because uniformity and shape of the beam pattern are quite important for optimum road visibility and safety for oncoming drivers. The Society of Automotive Engineers' specification on headlamp illumination [1] designates the maximum and minimum intensities at several spots within the beam. Many states require inspection of vehicle-mounted headlamps for illumination and aiming, and this test is commonly performed using a device which clamps on the headlamp lens. This clamp-on device is limited to checking the maximum intensity at beam center, rather than checking the overall beam pattern to the SAE-J579a specifications. In addition, mechanical limitations of this device have often resulted in the mis-aiming of vehicle headlamps. Present instrumentation available for measuring light intensity per SAE-J579a is primarily of the photo-cell type device, and the point-to-point measurement of light intensities is quite tedious and time consuming. A technique is described in this paper which incorporates electronic signal processing into a closed-circuit television system for displaying contours of constant illumination intensity. The technique is capable of rapidly performing vehicle-mounted headlamp testing per SAE-J579a and could be adapted for use at state inspection stations.

J.A. Bruder

Papers

Instrumentation for mapping light intensity contours