DESIGNING COST-EFFECTIVE 3D TECHNOLOGY

Transcription

1 DESIGNING COST-EFFECTIVE 3D TECHNOLOGY By Robert Murphy, Applications Engineer Senior, Cypress Semiconductor As consumer adoption rates for 3D display technologies increase, manufacturers of 3D active shutter glasses face the continual challenge of developing high quality glasses at costs consumers are willing to accept. Reducing the physical size, developing true universal operation, and lowering power consumption have also become critical considerations for manufacturers vying for a piece of this market. This article will examine the current 3D active shutter architectures employed today and contrast those with the next generation solutions now available. 3D Active Shutter Architecture 3D active shutter glasses operate by alternately driving a pair of liquid crystal lenses on and off. The switching of the lenses is synchronized with alternating left-eye and right-eye images generated from a 3D display. When the left-eye image is displayed, the glasses will open the left-eye lens and close the right-eye lens (and vice-versa). This synchronization happens at the refresh rate of your display (typically 120 Hz) and your brain then combines the two images giving a perception of depth. While the overall look of different 3D active shutter glasses may vary, the electrical architecture is very similar and typically broken into four distinct subsystems. Display Synchronization In order for the user to experience the 3D image, the display and the glasses must be perfectly synchronized as described above. To accomplish this, the display will transmit an infrared (IR) signal that contains synchronization information. This signal is detected by a photodiode in the glasses and then amplified and filtered to eliminate any ambient IR noise. Once complete, the signal is passed to the system controller for decode operations. System Control The system controller is the heart of the glasses and interfaces all the subsystems together. It will take the amplified and filtered signal from the display and decode the information before passing it to the shutter control subsystem. The system controller will also interface to the battery management system to ensure power is supplied throughout the system. Finally, the system controller will typical interface to any external peripherals, such as control inputs and buttons or USB. Shutter Control Once synchronization data has been decoded, the system controller will communicate with the shutter control system to operate the shutters in synchronization with the display. The shutter control system will typically boost the system voltage to match specifications of the liquid crystal shutters being used. The shutter voltage varies from vendor to vendor but is usually somewhere between 10 and 20 volts. This voltage is then supplied to the shutters, which are switched at a frequency that matches the refresh rate of the display. Battery Management All active shutter glasses require a battery to power the electrical components. The battery can either be a single-use coin cell battery or a rechargeable lithium based battery. Both systems require constant monitoring to ensure constant power output is being delivered to the system. In the case of rechargeable batteries, systems must be in place to monitor and control charging activities. This is specifically meant to safe guard against over voltage and over current which can cause damage to the device and the user in the case of a battery failure. Discrete Solutions As mentioned, the general architecture for all 3D active shutter glasses is the same. For first generation active shutter designs, manufacturers have utilized discrete components for each subsystem of the overall architecture described above and Designing Cost-Effective 3D Technology Page 1 of 6

2 shown in the block diagram in Figure 1. While this may have initially provided a quick time to market, this approach has three primary limitations that impact consumers. Cost Figure 1: Block Diagram of Current 3D Glasses Solution The primary driver for manufacturers today is reducing overall cost, and a discrete solution tends to be the most expensive option. When you add up the necessary op amps, boost converters, switches, battery charging ICs, microcontrollers, and various passive components required to implement the design, the BOM costs quickly escalate. Handling, inventory, and assembly costs are also increased as the number of components increases, making this design methodology very expensive. Size With a discrete component solution, the number of devices needed and real estate required to implement the design is significant. Even efficiently routed designs with proper noise isolation can require a significant amount of space on the PCB for routing traces of the numerous discrete components. Consumers are continually pushing for lighter weight glasses that have a sleeker design profile. Designs using discrete components struggle to deliver on both of the requirements. Flexibility Discrete component architectures offer far less flexibility in the overall design, making it difficult and expensive to create true universal operation. Instead, discrete component designs are targeted for a specific display or a specific model. While this may be effective for a quicker time to market, it reduces consumer options when buying glasses and locks them in to a specific brand specified by the display manufacturer. Integrated Solutions While the first generation designs used discrete components, some vendors are now moving to a more integrated solution using an ASIC (Application Specific Integrated Circuit). An ASIC is ideal for 3D glasses because they can be specifically tailored to do the task of decoding the IR synchronization protocol, while also handling the battery charging and shutter control. This is accomplished by integrating the boost circuitry and switching FETs internally to the device. Additionally, ASICs can do these tasks efficiently with relatively low power consumption and with a limited number of required external components to implement the entire solution. Unfortunately, an ASIC based design provides a fixed solution that is unable to be modified as the device requirements change. ASICs are also expensive to design and provide limited configurability options once implemented in a design. If the design significantly changes, then the ASIC will no longer be an ideal solution. While the individual cost of an ASIC may be minimal, most ASIC manufacturers will require upfront NRE (Non Recurring Engineering) fees that can reach cost levels of $1 million or greater. Designing Cost-Effective 3D Technology Page 2 of 6

3 Another area designers are considering is a move to more configurable microcontrollers with fixed function analog capabilities. These microcontrollers work well because they are able to provide a wide range of configurability options versus an ASICbased solution. Despite the increase in analog capabilities, most microcontrollers still have limited internal resources. Although many devices contain some fixed internal peripherals such as ADCs, comparators, timers, and PWMs, they lack many other key components that are required in a 3D glasses design. While the configuration options are great, the integration options are limited. To help compensate for the limited integration, many companies adopt an IR module to handle the IR receiver. This module contains all the required components to receive, amplify, and filter the IR synchronization signal in a small and simplistic package. The issue with the module is it contains fixed specifications and does not allow manufacturers to tweak or modify the module as they see fit. These limitations also require decoding of the IR synchronization to be handled with assistance of the CPU, increasing the power consumption of the device. This methodology may also reduce the performance of the CPU when working on other tasks because of the time critical nature of decoding the synchronization signal, which is dependent on how often synchronization is required. The limitations of both the ASIC-based and microcontroller-based architectures force device manufacturers to choose between configurability and integration. This tradeoff also makes it difficult to implement a true universal design as discussed in the previous section. Programmable System on a Chip (SoC) The Consumer Electronics Association (CEA) is working on a standardization of the IR synchronization protocol for 3D glasses. However, until this standard is finalized and adopted by the television manufacturers, designing a universal pair of 3D glasses to operate with all major television brands will require a significant amount of effort in terms of component count and design time. Each television manufacture will have a different requirement for the IR frequency, filtering requirements, and IR protocol. The challenge is to be able to detect which television manufacturer the viewer is using and dynamically adjust the 3D glasses to support that television s various requirements. This is where System on Chip (SoC) devices will play an essential role in the universal 3D glasses market. They provide the ability to migrate from the traditional fixed function device to fully configurable devices. These SoC devices include a wealth of programmable digital and analog resources that are capable of being adjusted dynamically. Upon powering of the SoC device, the analog and digital peripherals can reconfigure as they scan the IR signal until the device acquires a match on a television manufacturer. The device can then fully adjust the programming and operation to match the manufacturer s specifications, functioning just as a pair of glasses produced by that manufacturer would. Many of these SoC devices include analog peripherals such as filters, amplifiers, demodulators, and comparators. These peripherals remove the need for an elaborate external analog front end. Since these analog peripherals are internal to the device, register adjustments are all that is required to change the gain, filter parameters, and threshold levels. Digital peripherals such as timers/counters, PLDs, and various communication protocols, can also be adjusted dynamically to suite the protocol decoding and shutter control requirements. The analog and digital capabilities of these SoC devices also allow the battery charger and the high voltage shutter control to be implemented in a single device, leaving only passive components externally, such as FETs, inductors, capacitors, diodes, etc. This also allows the design to be transferred to different pairs of glasses with minimal design changes. Adjusting a few parameters in firmware, the boost output voltage for the shutters can be modified without changing the external hardware. As the battery capacity changes, a few adjustments in firmware can accommodate the new battery without modifying the external circuit. Finally, with majority of the display synchronization front end implemented internally in the device, the external schematic remains untouched while the internal peripherals are adjusted in firmware. Designing Cost-Effective 3D Technology Page 3 of 6

4 Figure 2: SoC Integration Capabilities In demonstrating this concept, the PSoC 3 family of devices from Cypress Semiconductor were chosen for their programmable analog and digital resources and their ability to implement the majority of 3D glasses functionality internally. These devices include programmable analog routing and functional blocks for analog peripherals, PLD logic to create digital peripherals, and a high speed Intel 8051 core. These devices also contain an internal digital filter block that can be used to implement dynamic adjustments of the IR filtering requirements depending on the design. Figure 3 shows how PSoC can integrate many of the required components in an active shutter design. Designing Cost-Effective 3D Technology Page 4 of 6

5 Figure 3: PSoC 3 Ability to Integrate 3D Glasses These new SoC devices offer the capability give designers the best of both worlds with integration and configurability. This in turn enables true universal operation and reduces the cost, size, and weight of the 3D glasses. Power consumption is also reduced due to the integrated components, improved power management, and overall efficiency of the design. Schematic design becomes significantly more simplistic which greatly reduces the possible failure nodes and go-to-market development time. In the end, moving from the discrete or ASIC based solutions of today to more flexible System on Chip solutions now being offered, provide significant advantages for both designers and consumers. Designing Cost-Effective 3D Technology Page 5 of 6

6 Cypress Semiconductor 198 Champion Court San Jose, CA Phone: Fax: Cypress Semiconductor Corporation, The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the use of any circuitry other than circuitry embodied in a Cypress product. Nor does it convey or imply any license under patent or other rights. Cypress products are not warranted nor intended to be used for medical, life support, life saving, critical control or safety applications, unless pursuant to an express written agreement with Cypress. Furthermore, Cypress does not authorize its products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress products in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges. PSoC Designer, Programmable System-on-Chip, and PSoC Express are trademarks and PSoC is a registered trademark of Cypress Semiconductor Corp. All other trademarks or registered trademarks referenced herein are property of the respective corporations. This Source Code (software and/or firmware) is owned by Cypress Semiconductor Corporation (Cypress) and is protected by and subject to worldwide patent protection (United States and foreign), United States copyright laws and international treaty provisions. Cypress hereby grants to licensee a personal, non-exclusive, non-transferable license to copy, use, modify, create derivative works of, and compile the Cypress Source Code and derivative works for the sole purpose of creating custom software and or firmware in support of licensee product to be used only in conjunction with a Cypress integrated circuit as specified in the applicable agreement. Any reproduction, modification, translation, compilation, or representation of this Source Code except as specified above is prohibited without the express written permission of Cypress. Disclaimer: CYPRESS MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARD TO THIS MATERIAL, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Cypress reserves the right to make changes without further notice to the materials described herein. Cypress does not assume any liability arising out of the application or use of any product or circuit described herein. Cypress does not authorize its products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress product in a life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges. Use may be limited by and subject to the applicable Cypress software license agreement. Designing Cost-Effective 3D Technology Page 6 of 6