In this blog post, we’ll explore the principles and advantages of capacitive fingerprint recognition technology and examine whether it’s evolving to be convenient for everyone to use.
The term ‘one-touch’ means simplifying a task that requires multiple steps into a single action. This concept of simplification is becoming increasingly important in modern society. Being able to resolve complex procedures or tasks with a single touch significantly contributes to saving time and enhancing efficiency in daily life. Particularly in a rapidly changing technological environment, the concept of one-touch has become a core element across various industries and services. Since effectively utilizing one-touch saves wasted time and effort, products and infrastructure employing this concept are steadily increasing.
While several tools enable one-touch functionality, fingerprint recognition technology is commonly employed. Offering both security and convenience, fingerprint recognition is rapidly being adopted across diverse fields. From easily accessible door locks to the automated immigration screening at Incheon Airport, fingerprint recognition technology enables one-touch solutions, adding convenience to our lives.
But a question arises: Can everyone truly enjoy this convenience? What about people whose fingerprints have worn away or those with injured fingers? Surprisingly, fingerprint recognition technology exists for them too. It’s called Active Capacitive fingerprint recognition technology. This technology overcomes existing limitations, allowing more people to benefit from fingerprint recognition. To understand this more easily, let’s first look at the technology used to create fingerprint recognition sensors.
The technology for making fingerprint recognition sensors is broadly divided into optical and capacitive types. For example, optical sensors are used at airport security checkpoints, while capacitive sensors are used in door locks and laptop computers. Capacitive sensors are further divided into two types: Directive Capacitive and Active Capacitive. For instance, Directive Capacitive is used in door locks, while Active Capacitive is used in laptop computers.
Optical fingerprint recognition sensors, as the name suggests, shine a strong light onto the finger and utilize the reflected fingerprint image. This method directly captures the fingerprint surface to collect data, offering high precision and stability as its advantages. However, its disadvantages include being expensive and bulky. Another drawback is that since it relies on the actual surface image of the finger, recognition rates can drop if the fingerprint is worn or damaged.
In contrast, capacitive fingerprint recognition sensors use electricity instead of light. Non-conductive objects can store electricity; this stored electricity is called static charge, and the amount of electricity that can be stored is called capacitance. Static electricity occurs precisely because of this capacitance. Since the capacitance of skin is greater than that of air, measuring this capacitance allows the fingerprint pattern to be obtained. This technology is particularly excellent at minimizing recognition errors caused by the condition of the finger.
There are two main methods for implementing capacitive fingerprint recognition sensors: direct measurement and signal measurement. The direct measurement method, as the name implies, measures the capacitance at the point where the fingerprint touches. While this method is inexpensive and can be made compact, it has the disadvantage of poor recognition accuracy. Therefore, this technology is primarily used in low-cost door locks or small electronic devices.
On the other hand, the signal measurement method sends a signal through the finger to measure capacitance. The signal entering the finger then exits back toward the sensor, but only from the area where the fingerprint on the finger makes contact. By measuring the signals flowing out here, the image of the fingerprint on the finger can be obtained. The signals measured in this way are influenced by the fingerprint imprinted in the dermis beneath the epidermis, not the epidermis itself. Unlike the epidermis, the dermis is resistant to damage and unaffected by environmental factors like dust or humidity, allowing it to capture a much more accurate image than optical or direct measurement sensors. Thanks to these characteristics, the signal measurement method is widely used in fields requiring higher security.
Using a signal measurement fingerprint recognition sensor allows even people with worn or injured fingerprints to enjoy the convenience of one-touch operation. Furthermore, because it can measure fingerprints with extreme precision, it also offers high security. Methods like replicating fingerprints from a glass, as seen in movies, to bypass security no longer work. Breaching the security of a signal measurement fingerprint sensor requires placing a finger directly on a high-resolution scanner for a precise scan.
However, signal measurement fingerprint sensors also have a critical drawback: their high cost per unit area. Consequently, many companies continue researching ways to make this technology more affordable, with some exploring new materials and designs to solve the pricing issue. Currently, they are typically produced in a thin, elongated shape, just the width of a finger, to reduce surface area. Because the narrow sensor cannot recognize the entire fingerprint at once, users must swipe their finger from top to bottom to capture the fingerprint. This makes the recognition process more inconvenient compared to other methods, adding another drawback.
Recently, there was welcome news that a smartphone has been released featuring an area-type signal measurement fingerprint sensor capable of recognizing the entire fingerprint. This news is welcome because it signifies that the technology has become affordable enough to be integrated into smartphones and produced in an area-based form capable of resolving the inconvenience of the recognition process. We look forward to further technological advancements, anticipating a future where more people can enjoy the convenience of fingerprint recognition technology in more places beyond smartphones.
