Television – Video display – Projection device
Reexamination Certificate
1998-12-11
2002-11-19
Hsia, Sherrie (Department: 2614)
Television
Video display
Projection device
C348S807000, C348S744000
Reexamination Certificate
active
06483555
ABSTRACT:
TECHNICAL FIELD TO WHICH THE INVENTION RELATES
The present invention relates to a universal device, provided with means to be controlled by a control unit which forms art of a projector. The device in conjunction with this control nit can be used inter alia for the automatic adjustment of the projector.
BACKGROUND ART
A standard CRT projector comprises three cathode ray tubes: one red, one green and one blue. Each of these cathode ray tubes is provided with projection means, which direct the light from these cathode ray tubes to a common screen. Three separate pictures are formed in this way, each in a different colour, which are superimposed on the screen. To obtain a good and clear picture on the screen, the different colours must be coordinated with one another. When a red, blue and green line are projected onto the screen, a white line can be seen on the superimposed picture when these three lines impinge exactly on each other, in other words when the convergence is well adjusted.
Many systems have been devised to improve the accuracy of the convergence adjustment.
First of all there is a manual adjustment system, as described for example in U.S. Pat. No. 4,672,275. In this, a reference picture provided with a number of reference points is projected onto the screen. A test picture which looks like the reference picture is projected onto this. This test picture is provided with a number of adjustment points, each corresponding to one of the reference points. In addition, a correction part is provided which corresponds to a given part of the reference picture. The correction part is a partial collection of the adjustment points. On carrying out the convergence adjustment, an adjustment point is selected within the correction part. The position of the selected adjustment point is altered with respect to the corresponding reference point. At the same time and proportionally, the positions of the other points within the correction part are also altered. As a result, the convergence of the correction part is built up in relation to the corresponding part of the reference picture. The correction data are stored in a large RAM.
This manual adjustment is very labour-intensive and time-consuming. Many potentiometers need to be set and moreover these frequently interact. It therefore follows that one requires a high level of knowledge to optimally adjust the equipment.
U.S. Pat. No. 4,999,703 describes a device for automatic convergence adjustment of a projector. Convergence correction is executed automatically, even during the operation of the projector, faults occurring as a result of drift in the electronic and mechanical components of the projector being eliminated. A test pattern for each of the primary colour pictures is projected onto a screen and the light reflected by the screen is scanned by a scanning system. The positions where the light sensor of the scanning system detects the test pattern for each of the primary colours are stored in a memory. These positions are then processed to determine correction values for the convergence of the primary colour pictures, in order to obtain convergence over the whole screen. A disadvantage of this method is that complete pictures are stored in the memory. For this purpose, large, and therefore expensive, memories are required.
U.S. Pat. No. 5,345,262 also describes a method and device for automatic convergence adjustment. In accordance with the method described therein, a test pattern is generated consisting of a row of discrete pattern units each of which has a contour and a central area, a variation in the illumination intensity appearing between the contour and the central area of the pattern unit. The test pattern is projected by each of the cathode ray tubes of the system. A row of light-sensitive elements is arranged so that they pick up the light from the test patterns that has been reflected by the screen. The position of each of the pattern units of a first projected test pattern is compared with the positions of the corresponding pattern units of the other projected test patterns. A number of error signals are generated and these are then used to control the cathode ray tubes so that the position of one of the test patterns is displaced in relation to the other such that the size of the error signals is reduced.
In accordance with a characteristic of the method described in the abovementioned American patent, the positions of different pattern units are compared by determining the centre of the slightly varying illumination intensity of each of the projected test patterns and comparing this with the position of the centres of the illumination intensity of the other test patterns.
A disadvantage of this is that a complete picture is sampled, which requires large memories, so-called frame memories. Frame memories are large memories that are able to store a complete picture. These are expensive and, in addition, time is lost during the adjustment process by looking for those locations where the test patterns have been displaced in relation to each other—thus where the convergence is not well adjusted.
The convergence adjustment takes place in the said patent by calculating central points. This calculation is background-sensitive, and in some cases (for example with a blurred picture) can lead to incorrect results. If the central points are adjusted on top of one another, the eye will not necessarily view this as the correct convergence adjustment.
Another disadvantage of the adjustment method described therein and the corresponding adjustment equipment is that only the convergence can be adjusted. For complete adjustment of a projector, the geometry, focus, astigmatism, contrast modulation and gamma correction must also be adjusted in addition to the convergence. All these adjustments have a mutual influence on each other.
In the method and equipment described in U.S. Pat. No. 5,342,262, the intensity of the background light is measured and stored once only. This has the disadvantage that during the further adjustment process fluctuations in the background light are not taken into account.
In U.S. Pat. No. 5,091,733, U.S. Pat. No. 5,231,481, EP-A-0 616 473, EP-A-0 498 659, U.S. Pat. No. 5,497,054 and U.S. Pat. No. 5,432,404, devices with specific applications are described for automatic adjustments of projectors. All these named publications are based on test pattern generators being specifically present, which ensure the generation of a pre-defined pattern unit or units. The associated adjustment methods are based on the presence of the generated test pattern and its shape (for example discrete light points etc.).
These said publications all deal with devices with specific applications which execute only a limited number of adjustments automatically, demands frequently being made on the hardware used and on the underlying hardware which ensures actual controlling. There are thus publications which are based on the fact that a filter is included for the camera used, and that there is no connection between different control zones and different adjustments per se, that the hardware is synchronized with the analog signal coming from the camera, and that the measurement results are absolute, etc. Other publications make demands on the camera used: the resolution of the camera must be sufficiently high, in some cases the camera must be set up so that it is itself movable, and/or the complete picture must be sampled, requiring the presence of large memories.
Not one of the abovementioned publications provides suitable solutions for obtaining rapid adjustments using a universal device in a broad range of projectors, irrespective of the control hardware itself. Besides, the devices described in the aforementioned patents (applications) are not able to fulfil any tasks other than the adjustments of the projectors. They cannot serve as a peak detector, as a signal decoder, as a RAM expansion, for signal testing and analysis, or for wire-free transfer of information, without anything needing to be altered on the device.
It is an objec
Thielemans Robbie
Tydtgat Claude
Barco N.V.
Hsia Sherrie
Pillsbury & Winthrop LLP
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