Dedicated LED light source
Publication Date: 2009-Aug-28
The IP.com Prior Art Database
The optical transfer curve of digital TV cameras (such as the commonly used Viper video stream camera) shows significant differences for the 3 channels (RGB). To improve the video stream quality often color balance is applied. If color balance is applied electronically in post production (Post Production Color Balance) by simply adjusting the gains to balance over the linear portion, we achieve a wide exposure range where the balance is correct. However, the bottom part of the curve shows the different noise levels in the colors and the (extreme) highlight portion shows a coloration towards magenta.
An alternative approach is to color balance before the CCDs, i.e., using optical filters (referred to as Optical Color Balance, typically with Magenta Filters). If this is done, the color balance is achieved over a wider exposure range and improved signal to noise, but since this is achieved by reducing the two higher level color signals, it is at the expense of sensitivity.
An improved method is described, combining the advantages of the optical color balance method with still very high sensitivity. To achieve this, we consequently propose a color tunable lamp for generating light comprising at least 3 different (sets of) semiconductor light emitting elements (e.g. an LED or a laser), illuminating a scene, which is recorded by a digital motion picture recording system. The spectral emission characteristic of said lamp is adjusted in a way that the RGB signal levels in the camera are substantially balanced. This is achieved by a light emission spectrum of said lamp that enhances emission in the blue and red part of the spectrum but relatively reducing green emission with respect to conventional white light sources.
Moreover a method is disclosed for adjusting the suitable spectral light settings of said lamp by linking the 3 sensor signals of the camera (optionally averaged in time and/or space) to the light control unit of said color tunable lamp.
The technical field of the present invention is lighting. More specifically, it relates to a lighting device for a motion picture recording system, e.g. a television recording system.
The Figure gives a model of camera in a real studio environment application for simulating the process of light reflected from the scene to the camera sensor and it puts nearly every interaction of light with each particular (optical) integrant into a physical/mathematical model.
Figure : The principle of one camera mode in handling the reflective light. The top block is a simple abstraction of real studio environment and the bottom block is a function modeling of typical studio camera. The interaction of light with each particular (optical) integrant is shown clearly, corresponding to specific a physical process in modeling.
In the Figure, the top dashed line block is the sketch of...