Optical sensors are playing a vital role in remote sensing as the agricultural sector strives to transform itself. This modernisation involves “doing less with more” because demand is increasing at the same time as climate change is hindering traditional farming methods.
Sensors collect a wide range of data, all of which contributes to greater crop protection. And while sensors might not always be the most visible part of smart technology, they are certainly one of the most important. After all, as with many other things, “you can't improve what you don't measure”.
Here, we examine some of the main types of optical sensors used in remote sensing and how they ultimately protect crops.
Agriculture is changing
Agriculture across the world is currently under intense social, commercial and environmental pressures, arising from:
- Surging demand for higher-quality food.
- Shrinking availability of farmland.
- Climate change and extreme weather conditions.
- Rising costs of energy and chemicals.
- Labour shortages.
- Increased regulation.
- Supply chain pressures.
But the good news is that data-driven smart farming is helping the industry to overcome these problems. There are now many systems and devices available to scan fields, test soil, monitor crops and track livestock. Examples of these include: seeding, weeding and crop-harvesting robots; precision irrigation systems; soil health sensors; automated milking and feeding machines; and crop-spraying drones.
In each case, the aim is to increase productivity in a cost-effective, safe and environmentally sustainable way.
Types of optical sensors
Many different optical sensors are used in agtech, each with its own qualities and capabilities.
1. Multispectral sensors
These sensors detect wavelengths that fall both inside and outside of the visible spectrum. They offer detailed insight into plant health, water stress and nutrient levels, which allows farmers to optimise management practices for maximum yields.
2. Hyperspectral sensors
Hyperspectral imaging analyses the reflection patterns of plants under different spectral bands. This provides information on vegetation mapping, plant health, yield and environmental conditions.
3. Thermal infrared sensors
These measure surface temperature and thermal distribution, which helps farmers to understand their crops, identify any issues and predict yields. For example, by identifying changes in leaf surface temperature, famers can detect disease or water-stress.
4. Fluorescence sensors
Fluorescence sensors detect subtle changes in plant physiology and health through fluorescent emissions. This enables precise monitoring of photosynthetic activity, nutrient uptake and stress responses in crops.
5. LiDAR (light detection and ranging)
These sensors provide highly accurate 3D mapping of terrain and crops, which facilitates precise analysis and management. By measuring distances with laser pulses, LiDAR helps farmers to assess canopy structure, monitor growth patterns and optimise planting densities for maximum productivity.
6. RGB (red, green and blue) cameras
RGB cameras capture high-resolution images of crops, fields and landscapes, providing valuable visual data for analysis and decision-making. With their ability to detect colour variations and patterns, these cameras enable farmers to assess plant health, detect pests and monitor crop development with precision.
Key applications of optical sensors in crop protection
Similarly, there is a wide range of applications of optical sensors, all of which contribute towards crop protection and maximising productivity.
1. Disease detection: The early identification of plant diseases is crucial for effective crop protection. Optical sensors can detect minute changes in leaf colour and texture, which allows identification of diseases before they are noticeable to the human eye. This enables timely intervention by the farmer, reducing the spread and severity of disease and so minimising crop loss.
2. Pest infestation monitoring: Certain pests leave specific signatures on crops, which can be detected by optical sensors. By monitoring these changes, farmers can implement targeted pest control measures, ensuring that interventions are both timely and only where needed.
3. Nutrient deficiency identification: Nutrient deficiencies manifest in various ways, such as changes in leaf colour and vitality. Optical sensors can detect these anomalies, enabling farmers to apply fertilisers and nutrients where they are needed most, promoting healthy crop growth and maximising yields.
4. Water-stress detection: Water is a critical resource in agriculture – too much of it or too little can both be catastrophic for the crop. Optical sensors identify areas that are experiencing water stress, allowing for more precise irrigation. This not only ensures that crops receive the moisture they need for optimal growth but also conserves water.
5. Yield prediction and optimisation: By analysing data collected from optical sensors, farmers can accurately predict crop yields. This information is invaluable for planning and resource allocation, ensuring that agricultural practices are optimised for maximum efficiency and sustainability.
Benefits of using optical sensors for crop protection
There are many benefits of using optical sensors in agriculture, including:
- Increased precision: Optical sensors provide precise, real-time data, which enables targeted interventions that save time and resources.
- Enhanced sustainability: By optimising the use of water, fertilisers and pesticides, optical sensors contribute to more sustainable agricultural practices.
- Increased crop yields: Timely detection of crop issues and proactive intervention lead to healthier plants and increased yields.
- Cost efficiency: Reducing the waste of resources (e.g. seeds, fertiliser and water) and minimising crop losses directly translate to increased profitability for farmers.
Challenges in scaling production and value engineering innovation
So, it’s clear that there is now a huge opportunity within the agricultural sector for OEMs. It is a time of great invention and innovation of agtech solutions, but there are some potential pitfalls.
This evolving industry will require collaboration between partners with different areas of expertise if new products and services are to be scaled up and commercialised quickly and effectively. For example, specific microelectronics support might be needed to create bespoke sensors that are used in vertical farming.
There are also technological challenges around OEMs scaling the production of components. Often, components need to be light, durable, accurate and able to function in hostile environments – for example, sensors are used in aquaculture, where they operate underwater and have to withstand the corrosive effects of seawater. At the same time, sensors must remain cost-effective, even for small-scale farmers who might not have the budget of a multinational agribusiness.
To function reliably in these extreme conditions, the manufacturer of sensor technology requires:
- The use of high-performance materials: Titanium, stainless steel, ceramics and polymers are able to withstand extreme environmental conditions, plus hydrophobic coatings offer additional protection against water
- Precision engineering: Tiny components for miniature sensors are produced via microfabrication and nanofabrication, along with 3D printing
- Controlled conditions: Sensors require assembly in cleanroom conditions to prevent contamination, which can impair their functionality; also hermetic sealing is used to protect against moisture and contaminants
- Active alignment technologies: This process corrects any manufacturing variances, ensuring that each sensor operates optimally
- Rigorous testing: Environmental and durability testing are crucial to determine whether the sensor will survive harsh conditions over long periods
- Quality control and calibration: Sensors require high-precision calibration to ensure accuracy – it’s no use getting lots of detailed data if the values don’t reflect reality
In this way, optical sensors can be tailored to meet the performance requirements for use in land-based and aquatic farming environments. But this process will be easier when it is supported by electronic manufacturing services (EMS) partners, who will have unique insights, skills and experience.
