The present invention relates to a liquid-crystal medium which comprises a component A which consists of one or more compounds of the formula IA, in which the parameters have the respective meanings given in the claims or in the text, and to the corresponding, novel mesogenic compounds and to the preparation thereof. The hydrophobic phase, if present, is composed of a hydrophobic polymer, particularly a hydrophobic pressure-sensitive adhesive, a plasticizing elastomer, a tackifying resin, and an optional antioxidant. The light coupler couples the light source to the multimode optical fiber such that objective speckle contrast is reduced. Further, another lens barrel having a coaxial drop lighting function of radiating light to the main surface of the chip along the same optical axis as that of the camera is disposed. The fastener is disposed on the case, and may be deformed under a force. On a selection of the visually modified icon, additional previewing may be provided.