256階調

WO2013049248(特表2015-504616)
"Ultrasonic sensors useful in the eyepiece or associated controller include Sonavation's SonicTouch™ technology used in Sonavation's SonicSlide™ sensors, which works by acoustically measuring the ridges and valleys of the fingerprint to image the fingerprint in 256 shades of gray（256階調）in order to discern the slightest fingerprint detail. The key imaging component of the SonicSlide™ sensor is the ceramic Micro-Electro Mechanical System (MEMS) piezoelectric transducer array that is made from a ceramic composite material."

WO2010065242(特表2012-510760)
"[0003] The Human Visual System (HVS) can distinguish much more gray levels（階調レベル）than the 256 levels offered by 8 bit data. Weber's Law states that the smallest step the eye can see is proportional to the absolute intensity, Δl/I ~ 1.4. This means the eye is more sensitive to changes in levels at lower gray levels and significant banding or contouring is visible when the steps are not small enough. In order to produce a smooth gray scale ramp from black to white that has no visible banding or contouring effects, at least 1024 levels are required, corresponding to a bit depth of 10 bits per channel."

"Figure 9 illustrates what image 8-800 looks like when it is displayed using only 256 gray shades（256階調）corresponding to 8 bits per channel."