The integration of thermal imaging devices into security surveillance, a major achievement in surveillance technology, is deeply dependent on the precision of its manufacturing and machining processes. This in-depth look delves into the complex world of custom imaging components and highlights the central role of machining in the production of infrared thermal imaging devices. From the expertly machined lens housings to the custom infrared detectors, the manufacturing of each component is critical to improving security measures.
This article not only analyzes the complex system composition and operating mechanisms of imaging devices, but also highlights key design considerations and challenges involved in manufacturing these sophisticated imaging components.
Composition of the security camera system with thermal imaging
Thermal imaging cameras are fundamental to modern security surveillance and consist of several important thermal imaging components that enhance functionality.
1. Lens and optics
The lens of a thermal imaging camera can focus infrared energy onto the sensor. The lens design and material determine the field of view (FOV) and extent of the scene captured by the camera. Taking into account factors such as lens diameter, focal length, and mounting threads, imaging device lens assemblies must be customized to accommodate specific lens sizes and shapes.
Lathe-mill machining is the primary manufacturing process for imaging device components, ensuring not only precision but also proper alignment within the imaging device. Customization of the lens housing highlights the importance of each individual component in the production of thermal imaging devices.
2. The detector
The infrared detector is the main component of infrared thermal cameras and is primarily responsible for detecting infrared energy. The resolution of the detector, determined by its pixel configuration, directly affects the level of detail and accuracy of the thermal image.
Additionally, the detector's thermal sensitivity, or noise equivalent temperature difference (NETD), is an important specification that reflects the camera's ability to detect minute temperature differences. This setting allows detection of small temperature differences as small as 0.01°C, displayed using different color palettes.
Another important aspect is the spectral range. Most thermal cameras operate in the longwave spectral range of 8 to 14 µm and are therefore suitable for numerous applications, from electrical inspection to firefighting.
3. Image processing and analysis
The final component is the processing and analysis of the captured infrared data. Modern thermal imaging devices have technologies to correct image irregularities, reduce noise and improve pseudocolors. These processing techniques refine the raw thermal data and improve image quality and readability.
Sophisticated algorithms are used to interpret thermal data, allowing the camera to distinguish between objects and backgrounds and detect anomalies or specific thermal signatures. Thermal cameras using this principle can work in total darkness or smoky environments because they rely on heat signatures rather than visible light. This processed data is essential for making informed decisions in security monitoring and other applications.
Considerations when designing thermal imaging devices
When designing thermal imaging devices, careful attention is required in material selection, surface finish, and assembly of machined parts. This section explores these aspects in more detail, highlighting the technical details and precision required for optimal performance.
Selection of materials for manufacturing thermal imaging devices
When manufacturing thermal imaging devices, consideration must be given to durability, lightweight construction, and impact resistance when choosing materials for casings and components.
- Aluminum: Commonly used in processing imaging equipment because it is lightweight, has excellent heat dissipation properties and durability. Aluminum is ideal for machining imaging components because it can minimize weight while maintaining thermal stability.
- Magnesium alloy: Due to their high strength-to-weight ratio, they are chosen for machined parts of imaging components. Magnesium alloys exhibit excellent thermal conductivity and mechanical properties and meet the requirements of customized imaging devices.
- Engineering plastics and polymers: High-quality polymers are used due to their lightweight construction, good thermal insulation and resistance to shocks, chemicals and environmental influences. These materials provide additional durability and protection against external influences, ensuring the longevity and reliability of the device.
- Titanium alloy: Titanium alloys are valued for their exceptional strength, corrosion resistance and light weight. They are ideal for applications that require durability and minimal weight, increasing the overall robustness of imaging devices.
To meet stringent dimensional specifications in manufacturing imaging devices, EDM and 5-axis machining are used. Techniques like laser marking and cutting are always used for complicated design requirements and precise manufacturing.
Material selection plays an important role in the production of individual thermal imaging devices. Combined with modern machining techniques, these materials are transformed into components that improve the functionality and durability of thermal imaging devices.
Surface Finish for Machined Imaging Components
When machining imaging devices, high-quality surface quality in the machining state ensures optimal device performance, such as lens assemblies or structural housings.
Anodizing or chemical film coatings can not only improve corrosion resistance but also increase heat emissivity, which is crucial for components in imaging devices exposed to infrared radiation.
Hard oxidation improves aluminum's surface hardness and wear resistance, making it suitable for harsh environments. This process also improves the corrosion resistance and thermal insulation properties of the material, which are essential to the stability and longevity of thermal imaging devices.
In military applications, the durability of these components can be further increased with military-grade spray paint, ensuring resilience in extreme conditions.
Assembly test of imaging equipment parts
Any misalignment or assembly defect may affect accuracy and sensitivity.
A critical aspect of assembly testing is ensuring tightness and fit of components. Proper sealing is essential for IP67 protection. The IP67 rating means the device is fully protected against ingress of dust and can withstand temporary immersion in water, making it suitable for a variety of demanding environmental conditions.
Vibration resistance and shock absorption tests ensure sensor reliability in environments with strong vibrations and possible shocks.
The tables and graphs shown in this figure illustrate tests performed on flexible temperature sensors to evaluate their resistance to shock and vibration. Vibration testing exposed the sensor to frequencies from 10 Hz to 2000 Hz and monitored the output under various conditions. The impact test evaluated the sensor's ability to withstand a force of 100g, simulating a sudden impact. The results, including real-time sensor output and temperature stability (129°C-130°C), demonstrated the robustness of the sensor to mechanical stress.
Finally, thermal imaging devices are often subjected to various environmental tests where they are exposed to different temperatures, humidity and other environmental factors to ensure that they function effectively under different conditions.
How are thermal imaging devices made?
The Multisensor Driver Visibility Enhancement System is a multiband imaging system that can be mounted on land, sea and air vehicles, enabling more efficient and frequent inspections of sites and equipment for large critical infrastructure and heavy industrial sites. It typically combines digital sensors to provide adequate situational awareness in darkness, smoke, smog, fog and other atmospheric disturbances that are normally invisible to the naked eye. This multi-sensor imaging device mounted on industrial drones enables short-range visual and thermal observations, minimizing operational and safety risks.
This multi-sensor imaging device is mainly composed of a sensor system, a data analysis system, a main metal frame and an outer shell. The sensor system detects and collects characteristic signals from the external environment using sensor components with different properties. The data analysis system is responsible for combining, analyzing and generating the information collected by the sensor system. The metal structure plays a role in securing and protecting the components of the sensor system and data analysis system. The external casing acts as armor for the entire system, isolating the internal components from the external environment through a seal between the parts, thus minimizing the impact of the external environment on the detection system and data analysis system.
In this section, we present a case study of adapting the main metallic structure of a multi-sensor vision system for heavy industrial installations.
1. Material requirements for processing the main metal structure
Multi-sensor enhanced driver vision system is commonly mounted on land, sea and air vehicles. It may be exposed to extreme environments such as extreme heat, extreme cold, humidity, dryness, oxidative and corrosive gases, and underwater, as well as high-intensity usage scenarios such as vibration and shock. This places high demands on the strength, hardness, corrosion resistance and apparent density of materials.
Under such requirements, 6061-T6 aluminum alloy is one of the best choices. It not only meets the requirements of the above application scenarios well, but also has cost advantages over magnesium alloys and titanium alloys in terms of material and processing costs.
2. Design analysis and machining process selection
Before selecting the processing technology, we must carefully analyze the product drawings and parts assembly structure.
The frame structure shown in the figure consists of 6 parts: front PCB support plate, rear PCB support plate, upper PCB support, lower PCB support, TI detector support and EO support.
- Preventing deformation when processing PCB boards and brackets
First, let's take a look at carrier boards and PCB supports. As we can see in the image, the red areas are the mounting surfaces, and the surfaces of the parts are intended for alignment with each other, which are then tightened with screws. Therefore, we found a parallelism positional tolerance requirement of 0.01 for these four parts in the corresponding positions of the drawings.
Deformation is the most common problem when machining thin, flat parts. As the structural properties of materials change during the machining process, the tension balance between material molecules is also disturbed, meaning profiles can easily deform and deform.
There are generally two ways to resolve this issue:
The first method is to add a heat treatment stabilization process before final finishing. This method is generally used on complex structural parts that require extremely high precision.
The second method is to reduce the feed rate for each machining and increase machining times. In this way, the stress in the material can be reduced gradually and slowly. This method is applicable to parts with a relatively simple structure.
In this specific case, these four parts can be machined using the logic of the second method, and the precision requirements of the parts can be met while controlling the machining cost for the customer.
- Sensor support
TI detector bracket and EO bracket are for sensor parts. Sensor parts detect and collect characteristic signals from the external environment. Deviation of the installation angle and position of sensor components may affect the accuracy of the input data. To ensure accurate installation of parts, high requirements must be placed on the accuracy of the installation position of parts.
- EO holder processing
The EO bracket is the Low Lux CMOS box. Mounting position accuracy is critical for imaging systems. As we can see from the drawing, the positional accuracy of the purple EO sensor mounting position is defined by the yellow surface A and the red surface B, and an accuracy requirement of 0.01 mm is proposed. The diameter accuracy of the purple area is +0.02 to +0.05, which not only allows smooth mounting, but also effectively limits the vibration of the sensor in the mounting position.
EO holder processing takes place in three stages:
- First, quickly process the rough surface of parts to save precision machining time in subsequent steps.
- In the second clamping process, the yellow, red and purple areas are processed in one pass through the combined turning and milling process, so that these three position characteristics can meet the requirements of position accuracy and precision in the drawing.
- Finally, the remaining structural features are processed in the third round. It is necessary to design suitable devices to prevent deformation of parts.
- TI detector bracket machining process
The support for the TI detector is the housing for the thermal imaging camera or SWIR camera. In the drawing we can see that four holes are provided for fixing the main parts. In this particular case, the distance between the centers of the circle is very important, we must maintain a tolerance of ±0.01 mm. To meet these accuracy requirements, we must use appropriate clamping devices to ensure that the workpiece is placed flat and vertical.
Furthermore, the two red holes are concentric circles and the two purple holes are concentric circles. Concentric circles must be machined in a single pass to ensure concentricity.
3. Surface Finish Considerations
Surface treatment is an important step that cannot be ignored after part processing is completed. Common parts are treated with normal anodizing for surface treatment. However, for products exposed to extreme environments, Military Grade III hard anodizing is the best choice.
The oxide layer of three-stage hard anodizing is thicker, up to 50 μm above m, the texture is denser and has better scratch and corrosion resistance.
In addition to the usual operational aspects that need to be taken into consideration when anodizing, there are two other things that we need to pay attention to due to the properties of the six parts of the casing.
- Choose a suitable air pressure for sandblasting
Before oxidation treatment, it is necessary to sandblast the surface of the parts to cover the knife lines created during CNC machining, so that the surface has a more uniform and perfect texture. Sandblasting involves spraying glass beads onto the surface of a part using a high-pressure airflow, thereby covering the original markings on the part's surface with glass bead stack markings. Excessive impact may cause parts to deform. Therefore, we must pay attention to adjust the air flow pressure according to the material, structure and precision requirements of the parts.
In our specific case, these 6 parts deform easily, so we should not set the air pressure too high.
- Carefully remove metal residue from the blind holes.
If the metal residues in the blind hole are not treated thoroughly, after oxidation treatment, they will form a compact hard block that is difficult to remove at the bottom of the blind hole, which will affect the effective depth of the blind hole and thread and affect the product assembly.
In our specific case, the lower PCB bracket and the upper PCB bracket each have 6 non-penetrating threads, which are blind hole structures. The EO bracket has 4 non-penetrating threads and is a blind hole structure. If it is blocked by metal debris, resulting in insufficient effective thread depth, it will seriously affect the assembly of parts.
Concluding
The production and processing of thermal imaging devices, especially for security surveillance, features a harmonious combination of advanced materials, precision technology and innovative image processing. Custom imaging components, from intricately crafted lens housings to detailed image analysis algorithms, represent the latest in surveillance technology.
Its wide range of uses in areas ranging from forest fire monitoring to industrial security underline its versatility and reliability. The targeted design and testing processes used in manufacturing these custom devices ensure they meet the high standards required for effective and reliable security and surveillance solutions.
