imperceptible

adj.

感觉不到的；细微的，逐步的；

1. The pulse is almost imperceptible.
   脉搏几乎摸不清。
2. He gave an almost imperceptible nod.
   他略一点头,别人几乎无法察觉。
3. The difference between the two colors is imperceptible.
   这两种颜色之间的差别很难区别。
4. There is an imperceptible change in temperature.
   温度有细微的变化。

Fragile imperceptible digital watermark with privacy control
Embedding and reading imperceptible codes on objects
Bokode: imperceptible visual tags for camera based interaction from a distance
An ultra-lightweight design for imperceptible plastic electronics.
A secure, imperceptible yet perceptually salient, spread spectrum watermark for multimedia
Embedding Imperceptible Patterns into Projected Images for Simultaneous Acquisition and Display
New echo embedding technique for robust and imperceptible audio watermarking
New echo embedding technique for robust and imperceptible audio watermarking
Tiled, flat-panel microdisplay array having visually imperceptible seams
Ankle stiffness of standing humans in response to imperceptible perturbation: reflex and task-dependent components.