Method of image acquisition by an image sensor of CMOS type for the recognition of optically readable code

Method for acquiring an image of one or more codes that are optically readable by a CMOS electronic image sensor, which is activated on reception, by the sensor, of an external triggering signal (Trig) and which comprises carrying out a measurement image capture in order to determine a desirable exposure-time value, said desirable exposure-time value then being applied as current exposure-time value to all the pixels of the matrix array, in order to carry out a nominal image capture, characterized in that the measurement image capture (Mode-Mes) comprises:

• an integrating phase (100), which is common to the pixels, and in which k different exposure-time values (Ti) are applied to pixels that are regularly distributed over the rows or columns of the matrix array, each pixel being associated with one among the k different exposure-time values, k integer at least equal to 2;
• a rapid-acquiring phase (102), in which digital image data (DATA(Ti)) are rapidly acquired with the various pixel-exposure-time values, and which comprises a rapid read-out phase applying under-sampling of the rows of the matrix array;
• and
• a determining phase (110), in which the desirable exposure-time value (Topt) is determined by comparing histograms calculated on the basis of the digital image data obtained in the rapid-acquiring phase for each different exposure-time value.