Computer graphics processing and selective visual display system – Data responsive crt display control
Reexamination Certificate
1999-03-23
2001-11-27
Saras, Steven (Department: 2675)
Computer graphics processing and selective visual display system
Data responsive crt display control
C345S011000, C348S181000
Reexamination Certificate
active
06323828
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to video output testing, particularly in personal computers.
BACKGROUND OF THE INVENTION
Generally personal computers must pass a number of manufacturing tests after the system is built to ensure their quality.
One aspect that must be tested is the video output. At present, the video output is usually tested by having a human engineer connect a monitor to the system unit and inspect by eye an image generated by the system under test and displayed on the monitor. The efficiency of this method is low and suffers from being somewhat subjective in that each engineer has their own judgement and vision. Thus the testing can be inconsistent and inaccurate.
Various automatic systems have been proposed to try and improve this situation, but these have certain drawbacks and are not thought to have been widely adopted.
For instance U.S. Pat. No. 4894718 describes a video signal testing system in which a cyclic redundancy check circuit is connected to a expansion slot of the computer and the video output. A value measured from a video signal is compared with a fixed value to justify the correctness of the signals without the use of the human eye. This system suffers from the disadvantage that since the unit is connected to an expansion slot of the computer under test, the test must either be carried out before the unit is fully assembled, or the unit must be dismantled in order to effect the test.
U.S. Pat. No. 5537145 discloses a system in which the image display ed on the monitor is measured by an optical testing unit and the result fed back to the system via an I/O subsystem. As well as suffering from the disadvantages set out above of having to connect to an expansion slot in the computer, this system also suffers from an inability to distinguish between problems related to the monitor itself and the circuitry within the computer under test which generates the video signals.
This invention is directed to overcoming the problems of the prior art by providing a simple and relatively cheap arrangement for testing the video output of a computer.
SUMMARY OF THE INVENTION
In brief, this is achieved by a system for testing the video output of a computer of the type in which a video output connector includes a data channel permitting data to be transmitted from a monitor connected to the video output connector to th e computer, the system comprising test apparat us having a connector for connection to the video output connector of a computer under test; the test apparatus comprising means to measure parameters of test video signals received through the connector and means to generate a result signal from the measured parameters for transmission to the computer under test over the data channel; and software for execution on the computer under test to generate the test video signals and to receive and process the result signal received over the data channel.
The invention makes use of the fact that the video output connector of a modern computer is provided with a data display channel. The VESA Display Data Channel (DDC) standards define a communications channel between a computer display and a host system. The channel is generally used to carry configuration information to allow optimum use of the display and may also carry display control information. In addition, it may be used as a data channel for accessing bus peripherals connected to the host via the display.
In at least a preferred implementation of the invention this Display Data Channel is used as a means to feedback measured test information from the video signal for processing by software running on the system under test. Of course application of this invention to other similar systems is not excluded. Only a very simple piece of extra hardware is required which simply plugs into the video output connector of a unit under test and does not require any additional connection to the computer. The tests can therefore be carried out on the final assembled computer product.
In a preferred embodiment, the test apparatus is arranged to derive power for its operational components from the video output connector, thereby obviating the need for separate power supply.
The test apparatus can have a video output connector and an operating mode in which signals from the connector are passed transparently to the video output connector. This enables a monitor to be connected to the unit which can be useful in monitoring the test process.
A switch can be provided for switching from a mode in which signals from the connector are passed transparently to the video output connector to a mode in which signals received from the connector are processed within the test apparatus, the switch being responsive to a signal received via the connector to switch between the modes. In the preferred embodiment, this signal is a predefined number of EDID read commands being received by the test apparatus within a predefined time.
The relatively low cost of the unit has the consequence that many of the units is use simultaneously at a plurality of final assembly stations as are typically used in modern personal computer final assembly. Units can also be used for off-site maintenance and testing of units in the field.
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Automated Video Test Card with Self-Test Mechanisms: IBM Technical Disclosure Bulletin, vol. 32, Issue 5B, pp. 257-263, Oct. 1989.
Hewlette-Packard Company
Kumar Srilakshmi
Saras Steven
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