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BTC302: Interim Report Sample


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  • 1. Interim Report Monitor Calibrator Kit BTC302 Engineering Project by Able Baker 1
  • 2. Contents 1 Introduction pg.3 2 Aims pg.3 3 Objectives pg.5 4 Market Research pg.5 5 Options Analysis pg.6 6 Extensions/Reductions pg.7 to Project 7 Budget pg.7 8 Project Development pg.8 9 Specification pg.9 2
  • 3. 1. Introduction: In this project, it is intended to build an easy-to-use CRT monitor calibrator, designed to be used by both technical and non-technical people, and will be both portable and practical in broadcasting environments. It is essential in broadcasting that monitors used for camera colour controls and post-production are calibrated, to assure the operator their output colours are the same as what is being broadcast. In broadcasting, lining up monitors can be time consuming in a very pressurised environment, and requires skill and technical understanding from the user. Currently, the most common way to calibrate a monitor is by using various test signals (sawtooth, pluge etc.) and using the eye to adjust. This method can be difficult to achieve calibration quickly, and can also cause the user a lack of confidence that their reference monitor is correctly calibrated. This CRT monitor calibrator is intended simply to guide the user step by step to adjust the contrast, brightness, red, green and blue levels, taking the calibration to the near complete stage quickly, leaving the user to apply minor tweaks by eye to complete the calibration if necessary. 2. Aims: It is therefore intended in this project to create a device that will provide the monitor its own PAL test signals to the CRT monitor, and will have a remote handheld sensor to be held against the monitor that will intelligently read the luminance values in a specific sequence of test signals. The test signals will have no pattern, and provide one colour at a time to the full screen, to make circuitry simpler and make easier for the operator to use, as the handheld sensor can be held anywhere on the monitor display. Using these readings, it will then be possible to adjust the contrast, brightness and individual red, green and blue pots, ultimately setting the correct colour temperature of 6500kelvin to match referenced calibrated values. The device will be able to communicate to the user via an LED display, which will guide the user which pot to tweak and which direction to tweak it, and when the pot is set correctly. It will also allow feature a next button to take the user to the next test signal, a restart button to begin a new calibration, and will be able to display when a calibration is successfully completed. See Figure 1 for a potential user interface of the main control unit. Figure 1 – Potential User Interface 3
  • 4. The design of the handheld sensor is also imperative. As it will be a calibration device, accuracy is essential, therefore consideration of cable length, photodiode position and filtering external light is critical. It will be designed for the operator to be held against the monitor display. See Figure 2 for a potential handheld sensor design. Figure 2 – Potential Handheld Sensory Design As it is unlikely any light sensory calibration device will be able to provide 100% accuracy due to a mix of factors including warm-up time, temperature, cable length etc. it is intended this device will be able to take the operator to the final stage of calibration quickly, leaving the user to apply minor tweaks by eye to complete the calibration if necessary. It is intended also for this device to also able to support various monitors, as some monitors only have simpler contrast, brightness and chroma controls. See Figure 3 for a simplified system block diagram of the electronic circuitry. Figure 3 – System Block Diagram 4
  • 5. 3. Objectives: Below is a list of objectives in order to successfully achieve the project aim; • To create a system that will generate a PAL signal generator with the signals required. • To design an appropriate handheld sensory device that filters out external light and considers factors including cable length, temperature and photodiode position. • To provide a live calibration system that will instruct the operator when the levels are correct and display in clear form (LED for too high, too low and correct level). • To conduct extensive research into electronic components required. • To develop a prototype to test the product functionality, and to develop hardware and software improvements. • To conduct extensive testing of photodiode performance. • To gather accurate readings and calibrate the monitor accurately. • To design the system to be as ‘easy-to-use’ as possible, suitable for both technical and non-technical personnel. • To conduct extensive testing of calibration performance with various monitors. • To design a suitable and practical electronics and housing design. These are the key objectives of project, however, they are subject to change during the development of the project, and may by extended or reduced, influenced by improvement or difficulty decisions. 4. Market Research: The manufacturers Sony, LaCie and Eizo have various monitor calibrators in the market used for computer monitor calibration. Personnel in the photography and graphics sector, working with software such as Adobe Photoshop etc. typically use these calibrators. These calibrators work in a similar design to the design in this project, with an external USB calibrator to be held against the monitor, however, they use software to provide test signals to the display using the graphics card, therefore, much simpler. These devices also enable an operator to calibrate a monitor to various the various colour temperatures used. Devices like these however were not found for broadcast monitor calibration. These devices, such as the ColorVision Figure 4 – ColorVision SpyderPRO Calibrator ( SpyderPRO Monitor Calibrator (See Fig 4) however have a variety of handheld sensor designs. The design of the remote calibrator is important to prevent external light entering the sensor and to prevent damage to the screen. The spider shape helps distribute weight over a larger surface area, which is least prone to damage an LCD if held against the monitor with too much force. Although the manufacturers of these devices haven’t released how exactly these products work, many claim to work with both CRT and LCD monitor displays. Although computer monitors and television monitors have a considerable difference in contrast ratio’s and brightness, it opens an investigation whether it is possible to also include LCD monitor support in to this product. 5
  • 6. In the research process, only very limited information was found regarding a specific monitor calibrator for broadcast monitors. Sony Broadcast have a monitor calibrator device to work with their BVM-Series monitors, however, these do not provide the sensor reading functionality to calibrate a monitor, and are typically used for maintenance and servicing, including advanced geometry controls etc. In contact with various vision engineers in the broadcasting industry, discussion was made on how monitor calibration is achieved currently. The most common method currently remains a complete calibration by eye with the aid of test signals including sawtooth, pluge, colour bars and blue only methods. On average, this process took an engineer between 5-10minutes per monitor to calibrate. Discussion regarding other calibration tools on the market for monitor calibration purposes was also conducted, and it was found one tool some engineers currently used to conduct monitor calibration was used to measure the level of black when using a pluge test signal. The response received regarding a broadcast monitor calibrator was very positive, and was suggested a successful product would be welcomed by vision engineers, lighting directors and editors in post-production etc. 5. Options Analysis: At this current stage, production of a prototype test board has begun to design the circuitry required to develop this product, especially focussing on the calibrator, involving the photodiode, filters and ADC. Various research into how CRT monitors operate and the issues that might affect the accuracy of calibration of this product such as scan rate have also been investigated. The key decision in this project has been whether or not to include an inbuilt PAL signal generator in this product. An alternative to having an inbuilt PAL signal generator would be using a computer graphics card to output a PAL signal to the monitor, requiring a RS232 communication link between the calibrator and a computer. This option would ultimately reduce the circuitry required in making a PAL signal generator, and could lower the costs of the product. It would also make it possible for instructions to be displayed on the screen of the monitor being calibrated, making it therefore more user-friendly, and would be much more achievable within the given timeframe of this project, enabling more time to focus upon development priorities such as the handheld sensor. Using this option, it would also enable a simple design for a calibrator, consisting simply of a photodiode, next and restart button, and the required circuitry, which could be directly connected to a computer and powered via USB (Universal Serial Bus). The intelligence of this calibrator could also be within the computer software. With the accuracy of this calibrator being essential, and with the calibration method designed to match monitor luminance outputs to referenced values in contrast, brightness, red, green and blue using PAL test signals, the test signal output to the monitor must be accurate. Tests have been conducted to find whether this system would compromise the accuracy and user-friendliness of the calibrator. A simple test signals sequence application was Figure 4 – Visual Basic Test Software made using Visual Basic, designed to be mirrored onto a second display on a computer outputting a PAL signal, allowing testing of the colour output and the instructions clarity (See Figure 4). In testing, we found this system would have major compatibility issues with many computers, as not all have the facility to output PAL signals. It was found also in Windows XP there was no option to output with a PAL colour temperature as standard, compared to Mac OSX. Using a VGA to Video converter, there was still difficulty outputting a PAL signal. Using a Scan Rate converter, converting VGA to PAL, it was then possible to view our calibration software on 6
  • 7. a monitor. With this signal looped through to a waveform monitor, the 100% white signal did not line up at 1 Volt. After testing the other test patterns and configurations, the conclusion is that the poor signal accuracy of this method was unsuitable for calibration purposes. It also requires other expensive equipment and compromises the user-friendliness of the product. It has therefore been decided to keep the PAL signal generator within the product. Another key option was to use a photodiode. With the calibration method being unproven and based on researched theory, it is required for a light sensor to measure the level of luminance in a range of test signals. With aid of the PAL signal generator, producing signals such as red, blue and green only, it is expected to find the luminance value of each red, green and blue value, and therefore adjusting accordingly to produce the correct colour temperature of 6500kelvin whilst not requiring colour filters in front of the photodiode. The photodiode is therefore an easy to produce and cheap solution to read luminance values. 6. Extensions/Reductions to Project: Should the development of the full project appear to not be achievable within the timeframe, a possible reduction to the project would be to exclude the LED communication interface on the main unit. To communicate to the operator alternatively, the main unit will connect to a computer via RS232 and the instructions will appear onscreen via full GUI (Graphical User Interface) software. The main software intelligence for the calibrator can also be programmed in the computer software rather than in the PIC chip inside the main unit. This will make development of the calibrator easier and will provide extra expandability should the calibrator require another feature. This modification will still allow full functionality of the product, however, it will also require a connection to a computer with software installed and running. Software will natively be made to run using the Windows operating system, however, if time is available, Mac OSX software can also be made. Both systems will be able to communicate with the monitor calibrator via a USB to RS232 cable. Other possible extensions to this project include adjustable colour temperature control and LCD display support. 7. Budget: After research of components required to produce the CRT monitor calibrator kit, it is expected to fall within the £100 budget. With research having been conducted to find the specifications required for the key component the photodiode, a suitable component was found for £6 excluding postage. The photodiode had the desired sensitivity ratings, dark level current and visible spectrum wavelength coverage required for this calibrator, and was an ideal choice. Amongst research via various UK electronic component distributors, this was the most ideal photodiode within our budget. Should there be concern that this photodiode is not suitable after testing, there has been budget allocated to invest in an alternative photodiode. Other equipment that will be required within the budget includes; capacitors, resistors, microchips, LEDs, BNC connectors, coaxial cable, product casing etc, however, these are all relatively low cost. Facilities required to develop the project including software and tools are available at no costs. To keep costs down, it has been decided this device will have a PAL signal generator rather than an SDI signal generator. PAL has a better compatibility rate within most broadcast monitors in the UK, however, its disadvantage is that signal levels can reduce over long cable lengths resulting in lower amplitudes which could cause the calibrator to become inaccurate, however, the calibrator will be set to work with a fixed 5 metre cable length, which should therefore not affect calibration readings. PAL encoder chips are available for £10, however, they will also require alternative circuit boards to be able to mount different chips. Budget has been made available also should replacement components be required. Please see Logbook Page 1 for an ordered component list. 7
  • 8. 8. Project Development: To date, there has been various development into producing a test board to be able to test the performance of the photodiode. Consideration of monitor scan rates have been made, therefore a 1kHz low pass filter has been made with the aid of MicroChip FilterLab software to design the circuitry (See Figure 5). Using an Oscilloscope, it has been possible to see the filter reduce noise in the signal dramatically, and filter out frequencies above 1kHz using an oscillator. Figure 5 – Photodiode Low Pass Filter Design The photodiode has now also been connected to the development board via the low pass filter and ADC (Analog to Digital Convertor) for testing (See Logbook Page 6). With data being sent now directly to a computer via RS232, we are now testing the photodiode response and ADC readings. (See Logbook Page 8 for circuit diagram). It is intended to have the PAL signal generator development begin by early 2008, and have extensive photodiode testing complete measuring performance against temperature, time etc. to obtain a full understanding of how to calibrate with optimum performance. For a full planned development schedule please see attached Gannt Chart (Figure 6). Figure 6 – Gannt Chart – Development Schedule 8