Hidden text is used most in the hologram label. Utilize the conjugation principle of optics to store the characters of the picture information in the holographic picture. Under the ordinany environment, the information can not appear.

When shine with the laser pen, people can see the information stored through sulphric, acid paper or blank sheet of paper.

The information stored cn be characters, identification, grey level picture, even an article. The form of expression is a reflecting type and transmission.