Abstract: In an optically readable information carrier, an information symbol has a predetermined area and includes an optically readable mark. The optically readable mark indicates at least part of the predetermined area. The information symbol is optically readable by an information reader after the predetermined area has been identified thereby. A mask member is arranged to abut on the information symbol. The mask member is also arranged to mask at least part of the optically readable mark while keeping presence of the information symbol externally visible to change the predetermined area of the information symbol to be unidentifiable.

Abstract: In an optically readable information carrier, an information symbol has a predetermined area and includes an optically readable mark. The optically readable mark indicates at least part of the predetermined area. The information symbol is optically readable by an information reader after the predetermined area has been identified thereby. A mask member is arranged to abut on the information symbol. The mask member is also arranged to mask at least part of the optically readable mark while keeping presence of the information symbol externally visible to change the predetermined area of the information symbol to be unidentifiable.

Abstract: Apparatus and method for recognizing optical information such as bar code has a light source and an image sensor which converts intensity of light reflected by the optical information into an electric image signal. The electric image signal is sample-and-held to detect the average intensity of light from the light source. The time interval for activating the light source is pulse width modulated in accordance with the detected average intensity in a previous operational cycle.