Ridge Pattern Recording System

A system for recording ridge patterns comprising:

• a source of light,
• an element determining the position of the scanning surface,
• an optical system,
• a multi-element image sensor, and
• an electronic memory for storing images and a processing unit,
• wherein an output image from the system is electrically linked in the electronic memory with at least two intermediate images, by blending in the processing unit the intensity values of elements of the intermediate images corresponding to different intermediate images of one and the same region on the scanning surface and assigning the value obtained for the intensity corresponding to this region to an element of the output image, and
• wherein each of the intermediate images is linked electrically with light-sensitive elements of the image sensor, which are linked optically with the light source and the ridge pattern scanning surface by way of the image of the ridge pattern scanning surface formed by the optical system, wherein, in the spectral range of sensitivity of the image sensor, the total flux of useful light with wavelengths less than the boundary wavelength L is at least five times greater than the total flux of stray light with wavelengths greater than L, and the value of L satisfies the condition:
• 0.37
• 
• 
• L
• 1.5
• A
• ·
• N
• ·
• T
• 1.2
• <
• 1
• wherein L is the boundary wavelength, expressed in micrometres;
• T is the interval between centres of the elements sensitive to the useful light in the image sensor, expressed in micrometres;
• A is the effective numerical aperture of the optical system forming the image of the scanning surface on the light-sensitive surface of the image sensor, on the image sensor side;
• N is the number of light-sensitive elements in the image sensor per one element of the output image.