Selecting an LCD for medical equipment involves more than choosing a display size and resolution.
The display becomes part of the mechanical design, electrical architecture, user interface, power budget, qualification process, and long-term product lifecycle.
For OEM engineers developing clinical, diagnostic, monitoring, respiratory, or other high-value medical equipment, these decisions should be made early enough to avoid unnecessary redesign later.
Focus LCDs works with OEM engineering teams on standard and customized LCD solutions, from prototyping through production.
Start With the Medical Equipment Requirements
The first step is defining what the display must accomplish in the finished equipment.
Important questions include:
- What information must the user see?
- How much information must appear at once?
- Will the equipment use graphics, text, symbols, or a combination?
- Will the operator interact with the display?
- What viewing distance is expected?
- What ambient lighting conditions will be present?
- Is the equipment portable or stationary?
- What power is available?
- What operating environment is expected?
- How long is the product expected to remain in production?
These requirements help determine which display technology and configuration are appropriate.
Monochrome LCD or TFT?
The required user interface should drive the technology selection.
Monochrome LCDs
A monochrome display can be appropriate when the equipment primarily needs:
- Numerical information
- Fixed symbols
- Status indicators
- Characters
- Simple graphics
Monochrome LCDs can also be customized at the glass level.
Depending on the project, Focus LCDs can customize characteristics such as dimensions, shape, resolution, segment layout, viewing mode, backlight, connector configuration, and other elements of the assembly.
This flexibility can be useful when the medical equipment has a specific mechanical envelope or user-interface requirement.
TFT LCDs
A TFT may be more appropriate when the product requires:
- Full-color graphics
- Detailed graphical interfaces
- Images
- Multiple data fields
- More complex navigation
- Touchscreen interaction
Focus LCDs does not modify the TFT glass itself.
Instead, customization can be applied to the components surrounding an established TFT panel, including FPC cables, backlights, touchscreens, cover glass, optical bonding, adhesives, and custom PCB or PCBA integration when part of the LCD assembly.
For more information, see Custom TFT Displays: What Can Actually Be Customized?.
Consider the Product Lifecycle Early
Medical equipment can remain in production and service for many years.
That makes display lifecycle particularly important.
Changing the LCD later may affect:
- Mechanical fit
- PCB layout
- Firmware
- Touchscreen operation
- Optical performance
- Documentation
- Qualification
- Manufacturing procedures
For equipment that requires significant engineering or qualification effort, changing the display after the product has entered production can be disruptive.
Engineers should therefore consider not only whether a display works for the prototype, but whether it is appropriate for the expected life of the equipment.
For additional information, see LCD lifecycle risk management for OEM programs.
Display Size and Mechanical Integration
The display should be evaluated as part of the complete mechanical assembly.
Important characteristics can include:
- Overall dimensions
- Active area
- Viewing area
- Thickness
- Connector position
- FPC orientation
- Mounting method
- Cover glass
- Touchscreen stack-up
- Enclosure clearance
A display that meets the electrical and optical requirements may still create problems if it does not integrate properly with the enclosure or PCB.
Mechanical requirements should therefore be defined before the product design becomes fixed.
Selecting the Display Interface
The LCD interface affects the customer’s processor, PCB, firmware, signal routing, and overall electronics architecture.
Focus LCDs supports display configurations using interfaces such as:
- SPI
- I2C
- Parallel
- RGB
- LVDS
- MIPI DSI
- MCU
- Other interfaces depending on the selected display
The appropriate interface depends on the display technology and system architecture.
Selecting the interface early can reduce the risk of PCB or firmware changes later in development.
Power Consumption for Portable Medical Equipment
Power consumption can be particularly important for portable and battery-powered medical equipment.
The display subsystem may include more than the LCD panel itself.
Power may also be required by:
- Backlights
- Touch controllers
- Display controllers
- Interface electronics
- Power-conversion circuitry
- Supporting PCB components
The engineering team should therefore evaluate the complete display assembly rather than only the nominal power requirement of the panel.
For portable equipment, backlight usage may have a significant effect on the system power budget.
Backlight Requirements
Backlight selection should be based on the actual operating environment.
Considerations may include:
- Ambient lighting
- Required readability
- Viewing distance
- Available power
- Thermal requirements
- Expected duty cycle
- Mechanical space
The brightest available configuration is not automatically the best choice for every product.
The correct backlight should support the viewing requirements of the equipment while fitting within the overall electrical and mechanical design.
Focus LCDs can customize backlights as part of appropriate display assemblies.
Touchscreen Selection
Medical equipment may require touch interaction, but the appropriate touch technology depends on how the equipment will actually be used.
Focus LCDs supports both resistive and capacitive touchscreen integration.
Resistive Touch
A resistive touchscreen may be appropriate for applications requiring a straightforward pressure-based input method.
Capacitive Touch
Capacitive touchscreens can support more advanced user interfaces and may be appropriate for products requiring modern touch interaction.
However, touchscreen performance should always be evaluated under the actual operating conditions of the equipment.
Factors such as gloves, moisture, cover materials, enclosure design, and user interaction requirements should be considered during development rather than assumed.
Custom Cover Glass
Cover glass can become an important part of the user interface and mechanical assembly.
Depending on the project, requirements may involve:
- Overall dimensions
- Display opening
- Printed borders
- Touchscreen integration
- Mounting
- Mechanical protection
- Product appearance
Cover glass requirements should be coordinated with the LCD, touchscreen, enclosure, and bonding approach early in the design.
Focus LCDs can integrate custom cover glass into appropriate display assemblies.
Optical Bonding
Optical bonding may be considered when the display, touchscreen, and cover layer need to be integrated into a more complete assembly.
The suitability of optical bonding depends on the materials, display construction, mechanical requirements, and intended operating environment.
Because bonding affects the complete display stack, it should be considered before the enclosure and touchscreen design are finalized.
Focus LCDs supports optical bonding as part of customized display assemblies.
Viewing Conditions and Readability
Medical equipment may be used under a wide variety of lighting conditions.
Engineers should consider:
- Indoor lighting
- Bright ambient lighting
- Viewing angle
- Viewing distance
- Required contrast
- Backlight level
- Reflective or transflective options where appropriate
The correct display configuration depends on the actual environment in which the equipment will be used.
Readability should therefore be evaluated during prototype testing rather than based only on a specification sheet.
Operating Temperature and Environment
The LCD must also be appropriate for the equipment’s expected operating environment.
Potential considerations include:
- Operating temperature
- Storage temperature
- Humidity
- Mechanical shock
- Vibration
- Repeated transportation
- Cleaning environment
- Enclosure characteristics
The applicable requirements will vary considerably between equipment intended for a controlled clinical environment and equipment expected to operate in the field.
Engineers should define the real operating conditions before selecting the display.
Standard LCD or Customized Display?
Customization is not always necessary.
If an existing standard display meets the mechanical, electrical, optical, and lifecycle requirements, it may provide the simplest development path.
Customization becomes useful when an existing product does not adequately support the application.
Examples might include the need for:
- Different mechanical dimensions
- Custom monochrome glass
- A different FPC
- Touchscreen integration
- Custom cover glass
- Optical bonding
- Modified backlighting
- PCB or PCBA integration
The objective should be to use the level of customization that solves the actual engineering problem.
View Focus LCDs custom display capabilities.
Prototype Evaluation
Prototype evaluation should reflect the way the medical equipment will actually be used.
Depending on the project, engineers may evaluate:
- Mechanical fit
- Electrical operation
- Interface compatibility
- Firmware behavior
- Viewing angle
- Readability
- Backlight performance
- Touchscreen operation
- Cover-glass alignment
- Optical appearance
- Environmental performance
Prototype requirements and schedules depend on the individual project.
Engineering feedback should be resolved before approving the display configuration for production.
Documentation and Change Control
For long-lifecycle medical equipment, display documentation becomes particularly important.
The OEM should maintain accurate records of the approved display configuration, including the characteristics that are critical to the product.
These may include:
- Part number
- Drawings
- Electrical requirements
- Interface
- Pinout
- Controller
- Backlight
- Touchscreen
- Cover glass
- FPC configuration
- Approved assembly details
Clear documentation helps the engineering team understand which characteristics can change and which must remain controlled throughout the product lifecycle.
Regulatory Responsibility Remains With the OEM
The display is one component within the complete medical equipment design.
Focus LCDs can provide display-related technical information and engineering support, but the OEM remains responsible for determining and satisfying the regulatory, safety, verification, validation, and documentation requirements applicable to the finished equipment.
Display selection should therefore be coordinated with the OEM’s broader product-development and qualification process.
Questions to Answer Before Selecting the LCD
Before finalizing a display for medical equipment, consider:
- What must the user see?
- Is monochrome or TFT technology more appropriate?
- What mechanical space is available?
- Which interface will the system use?
- What is the display subsystem’s power budget?
- Is touch required?
- Will gloves or other operating conditions affect touch interaction?
- What cover-glass requirements exist?
- Is optical bonding required?
- What ambient lighting conditions are expected?
- What operating and storage environment must the display support?
- How long is the product expected to remain in production?
- Which display characteristics would be difficult to change after qualification?
- Is a standard display sufficient, or is customization required?
Answering these questions early helps prevent the display from becoming a late-stage integration problem.
Plan the Display Early in Medical Equipment Development
Display selection affects the mechanical, electrical, software, user-interface, and lifecycle requirements of the finished product.
For long-life medical equipment, those decisions can become increasingly difficult to change after the product architecture has been established.
Focus LCDs works with OEM engineering teams to evaluate standard displays, custom monochrome LCDs, customized TFT assemblies, touchscreens, cover glass, optical bonding, backlights, FPCs, and other display-related requirements.
Contact Focus LCDs engineering support to discuss the display requirements for your medical equipment project.
