Fingerprint Scanners 101: Capacitive vs. Optical vs. Ultrasonic

Fingerprint Scanners 101: Capacitive vs. Optical vs. Ultrasonic

Biometrics through fingerprint scanners or readers have increasingly become a default feature in most smartphone, tablets, laptops, and other consumer electronic devices. Although some companies have also moved toward facial recognition such as in the case of the Face ID technology found in iPhone and iPad devices of Apple or the Iris Scanner of Samsung, a number of manufacturers still prefer fingerprints as the primary biometric entry point to their devices and user authentication.

Take note that there are different technologies for implementing biometrics through fingerprints. Nonetheless, understanding how fingerprint scanners work requires understanding the difference between capacitive, optical, and ultrasonic scanners.

The Difference Between Capacitive, Optical, and Ultrasonic Fingerprint Scanners

How Do Capacitive Scanners Work: The Pros and Cons

The most common type of fingerprint scanning technology is capacitive scanning. A particular capacitive scanner uses an array of tiny capacitor circuits. These circuits use electrical currents to scan and generate an image of the ridges and valleys of a finger. Once captured, the processor linked to the scanner analyzes the digital image to look for distinctive and unique fingerprint attributes.

Below are the pros or advantages of capacitive fingerprint scanners:

• The technology has become easier to implement due to economies of scales stemming from the availability of outsourced manufacturers.

• Implementing the technology has become less costly as well, thus making capacitive scanners available to both budget-oriented and high-end devices.

• A key advantage of capacitive scanners over optical scanners is that they do not depend on the pattern of light and dark. These scanners depend on the physical nuisances of fingerprints, thereby making them more secure.

• The component of a specific capacitive scanner is more compact than the component of an optical scanner because it is based primarily on a semiconductor.

• They are also faster and more efficient than both optical scanners and ultrasonic scanners. Capacitive scanners are the fastest fingerprint scanning technology.

• Capacitive scanners can be placed on a physical button or solid surface. Other input gestures, as well as swiping and scrolling, can also be placed alongside the capability to read fingerprints.

A major drawback of capacitive fingerprint readers is that they cannot be used as in-display fingerprint scanners because the technology is not compatible with the specific capacitive touch input technology used in display techs such as IPS LCD or OLED display.

Hence, manufacturers of mid-level to high-end devices are moving away from capacitive fingerprint scanning because of a design rend that revolve around larger screen real estate and bezel-less display. Its common implementations include placing them alongside a physical button or an accessible surface of a device.

How Do Optical Scanners Work: The Pros and Cons

Optical fingerprint sensors or optical scanners have become a common solution to implementing in-display fingerprint scanning. The technology works by capturing a two-dimensional optical image of the fingerprint and analyzing ridges and valleys.

Central to optical scanning technology is a light sensor system called a charge coupled device or CCD. Note that this same sensor is used in camcorders and digital cameras. The CCD essentially captures an image of the finger with the help of LEDs to illuminate the surface of the finger.

The following are the pros or advantages of optical scanners:

• They can be placed within a capacitive display screen, thus enabling in-display fingerprint scanning and allowing manufacturers to develop devices with larger screen real estate and minimal to zero bezels.

• Compared with ultrasonic fingerprint scanners, implementing an optical fingerprint scanning technology is less costly. This allows manufacturers to use optical scanning on mid-level devices.

• The entire system is still considerably small. The optical module can occupy an area footprint of less than one millimeter.

There are some concerns over this type of fingerprint scanner. Below are the cons and limitations:

• A major disadvantage of optical fingerprint sensors is that most CCD components cannot always distinguish between a picture of a finger and the finger itself.

• Note that the technology only captures a two-dimensional image. Prosthetics and images with a considerably quality can be used to fool the system.

• Essentially, optical fingerprint scanning technology is less secure and more unreliable than the technologies used in capacitive scanners and ultrasonic scanners.

• The scanners are generally slower than capacitive scanners. Furthermore, newer ultrasonic scanners are considerably faster than optical scanners.

How Do Ultrasonic Scanners Work: Pros and Cons

The latest fingerprint scanning technology uses ultrasonic transmitter and receiver. Generally, an ultrasonic scanner generates and transmits an ultrasonic pulse against the finger. Depending upon the ridges, valleys, pores, and other nuisances of the finger, some of the pulse gets absorbed while some bounces back to the sensor. The pulse essentially maps out a three-dimensional image of the fingerprint.

The following are the pros or advantages of ultrasonic scanners:

• Ultrasonic scanners can capture a highly detailed three-dimensional image of the fingerprint.

• They are more secure than capacitive scanners and, of course, definitely more reliable than optical scanners.

• An ultrasonic scanning module can be used as an in-display fingerprint scanning solution, thus allowing large screen real estate and bezel-less designs.

• They also work in non-ideal situations, such as if the users have dirty or wet hands. They do not depend on electrical charges, unlike capacitive scanners.

Below are the cons or disadvantages and limitations:

• They are considerably slower than capacitive scanners because of the underlying operational mechanism.

• Scanners used as in-display fingerprint scanners do not work effectively with some screen protectors because the ultrasonic pulse cannot travel through a thick surface.

A Note on the Pros and Cons of Capacitive, Optical, and Ultrasonic Fingerprint Scanners

Remember that capacitive, optical, and ultrasonic scanners also share the same general advantages and disadvantages of biometrics and user authentication through electronic fingerprint identification.

Some of the notable advantages of fingerprint scanning include convenience over PIN or password, security of biometrics over other identity verification methods, and easier and less costly implementation than facial recognition.

Major disadvantages include inferior biometric solution than facial recognition, does not take into consideration changes in physical attributes, and susceptibility to false acceptance and false rejections.

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