一种用于在介质光学测量的压力差（ΔP）的装置（14; 14“; 15）由一个法布里 - 珀罗干涉仪（9）的装置包括（1）具有第一反光镜的透明平行平面板（7）和上一个 设置测量膜片（4）第二反射镜（8），其是可移动的垂直于所述光轴（10）的镜平面，其中在所述测量膜片（4）中的压力差导致的膜偏移。 在测量膜片的机械残余应力（4），以防止承载板（2）是在测量膜片的范围（4）被降低到预定的厚度。 承载板（2）的材料是圆形无缝到承载板的材料（2）跨越测量膜片（4）。

An apparatus for optically measuring a pressure difference (Dp) in a medium (14; 14 '; 15) by means of a Fabry-Perot interferometer (9) comprises a transparent plane-parallel plate (1) having a first mirror (7) and on a measuring diaphragm (4) disposed second mirror (8) which is movable perpendicular to the mirror plane in the optical axis (10), wherein the pressure difference across the diaphragm (4) causes a diaphragm stroke. In order to avoid mechanical residual stress in the measuring diaphragm (4), the carrier plate (2) in the region of the measuring diaphragm (4) is reduced to a predetermined thickness. The material of the carrier plate (2) goes round seamlessly into the material of the carrier plate (2) spanned measuring diaphragm (4).