A Comprehensive Guide to Thermal Camera Modules
Thermal imaging is no longer a futuristic technology reserved for high-budget military projects. Today, it is a vital tool for makers, engineers, and researchers. This guide provides a foundational understanding of thermal camera technology and how to choose the right module from MLAB.
Part 1: Understanding Thermal Imaging Basics
Before choosing a module, it is essential to understand the technical parameters that define how a thermal camera "sees" the world.
1. How Thermal Cameras Work
Unlike visible light cameras that capture reflected light, thermal cameras detect Infrared Radiation (IR) emitted by all objects with a temperature above absolute zero. This radiation is converted into an electronic signal and then processed into a visual image where different colors represent different temperatures.
2. Key Technical Parameters
Resolution (Array Size)
Resolution is the number of pixels in the thermal sensor. A 32x24 resolution means the camera has 768 individual "thermal pixels."
Higher resolution provides sharper images and allows you to detect smaller objects from further away.
For example:
- 32x24 to 80x62: Entry-level, best for close-range sensing, human presence detection, or simple temperature monitoring.
- 160x120 to 320x256: Mid-range, the industry standard for detailed industrial inspection, electrical surveys, and professional diagnostics.
- 640x512 and above: High-end, required for long-range surveillance, high-altitude drone mapping, or applications demanding maximum detail.
Thermal Sensitivity (NETD)
NETD stands for Noise Equivalent Temperature Difference. It is measured in milliKelvin (mK) or Kelvin (K).
It represents the smallest temperature difference the camera can distinguish. The lower the NETD value, the higher the sensitivity, and the better the camera is at detecting subtle thermal variations.
For practical purposes, sensitivity tiers can be categorized as:
- <30mK (Excellent): Ideal for high-precision applications like medical imaging, detecting subtle structural issues in buildings, or advanced R&D.
- 50mK - 70mK (Good): Suitable for most industrial inspections, security, and general-purpose applications.
- >100mK (Entry-Level): Best for simple "hot vs. cold" detection where high thermal contrast is present, such as basic monitoring or simple sensor applications.
Spectral Range (LWIR vs. MWIR)
Most modular thermal cameras operate in the Long-Wave Infrared (LWIR) range (8-14μm).
- LWIR: Ideal for room-temperature objects and works through smoke and dust. It does not require expensive cooling systems.
- MWIR (3-5μm): Used for high-temperature targets or long-range surveillance, often requiring cryogenic cooling.
Emissivity
Emissivity is a measure of how efficiently an object radiates heat.
- A "Blackbody" has an emissivity of 1.0 (perfect emitter).
- Shiny metals have low emissivity (e.g., 0.1), meaning they reflect thermal energy from the surroundings rather than emitting their own. Most thermal cameras allow you to adjust the emissivity setting to get accurate temperature readings.
Field of View (FOV)
FOV determines the extent of the scene the camera can see, typically measured in degrees (e.g., 45°, 90°, 110°). It is a critical factor that directly impacts the camera's spatial resolution and working distance.
Understanding the Trade-off:
A wider FOV captures a larger area but means each pixel covers a larger portion of the scene, reducing the detail on distant objects. A narrower FOV "zooms in," providing greater detail (higher spatial resolution) on objects further away.
Practical Examples:
- Wide FOV (90° to 110°): Essential for applications where you need to see a large area at close range, such as indoor security, building envelope inspections (finding heat leaks in walls), or close-up PCB analysis. The MLAB MLX90640 offers a 110° option, perfect for this.
- Narrow FOV (45° to 55°): Ideal for applications requiring detail at a distance, such as inspecting power lines, monitoring machinery from a safe distance, or long-range outdoor surveillance. The MLAB ESP32-S3 Module offers a 45° option for this purpose.
Choosing the right FOV is a balance between the size of the area you need to cover and the distance from which you need to measure or observe.
Part 2: Choosing Your MLAB Thermal Module
Now that you understand the basics, let's look at how these parameters apply to the professional solutions available at MLAB.
1. The Entry-Level Powerhouse: MLX90640 IR Array
The MLX90640 is a fantastic starting point for those new to thermal imaging.
- Resolution: 32 × 24 Pixels.
- Sensitivity (NETD): 0.1K (100mK) — Excellent for distinguishing heat signatures in DIY projects.
- Interface: I2C, making it highly compatible with Arduino, ESP32, and Raspberry Pi.
- Best For: Gesture recognition, simple smart home sensors, and basic heat leak detection.
Figure 1: The MLX90640 - A compact and affordable I2C thermal sensor.
2. The Advanced Choice: ESP32-S3 IR Thermal Module
For projects requiring more detail and wireless flexibility, the ESP32-S3 Thermal Module is the ideal choice.
- Resolution: 80 × 62 Pixels (over 6x more pixels than the MLX90640).
- Connectivity: Built-in WiFi and Bluetooth, plus a USB Type-C port.
- Refresh Rate: Up to 25 FPS, providing smooth real-time video.
- Best For: Remote industrial monitoring, drone payloads, and detailed PCB thermal analysis.
Figure 2: The ESP32-S3 Module - High resolution with wireless capabilities.
Part 3: Technical Comparison Table
|
Parameter
|
MLX90640 (MLAB)
|
ESP32-S3 Module (MLAB)
|
|
Array Size
|
32 × 24
|
80 × 62
|
|
Total Pixels
|
768
|
4,960
|
|
Sensitivity (NETD)
|
100mK
|
125mK
|
|
FOV Options
|
55° / 110°
|
45° / 90°
|
|
Max Refresh Rate
|
64Hz
|
25 FPS
|
|
Communication
|
I2C
|
WiFi, BT, USB-C, UART
|
Conclusion
Choosing a thermal camera module is a balance between your technical requirements and your budget. If you are just starting out or need a simple sensor, the MLX90640 is a reliable choice. For professional-grade imaging with wireless integration, the ESP32-S3 module stands out.