Optimizing focus plane position of imaging scanner

A method comprising:

• projecting a light pattern towards a target object;
• detecting light returned from the target object through an imaging lens arrangement with an imaging sensor to capture a first image during a first frame exposure time period, the imaging sensor having rows of photosensitive elements arranged in a matrix wherein each row of photosensitive elements is associated with a corresponding row-exposure-time period;
• changing the position of the focus plane of the imaging lens arrangement during a time period that covers at least a first row-exposure-time period and a second row-exposure-time period, and the average position of the focus plane of the imaging lens arrangement during the first row-exposure-time periods associated with a first selected row is different from the average position of the focus plane of the imaging lens arrangement during the second row-exposure-time period associated with a second selected row;
• processing the first image to determine an optimized position of the focus plane of the imaging lens arrangement, wherein said processing the first image comprises comparing a first part of the first image with a second part of the first image, and wherein the first part of the first image includes pixels captured with photosensitive elements at least in the first selected row, and the second part of the first image includes pixels captured with photosensitive elements at least in the second selected row;
• and
• detecting light returned from the target object through the imaging lens arrangement with the imaging sensor during a second frame exposure time period to capture a second image when the position of the focus plane of the imaging lens arrangement during at least part of said second frame exposure time period is maintained at the optimized position as determined from processing the first image;
• and
• processing an image of a barcode in the second image to decode the barcode.

An apparatus comprising:

• an imaging sensor having rows of photosensitive elements arranged in a matrix, the imaging sensor being configured to capture an image from a target object during a frame exposure time period wherein each row of photosensitive elements is associated with a corresponding row exposure time period;
• an imaging lens arrangement configured to operate together with the imaging sensor for detecting light from the target object within a field of view;
• a light pattern arrangement configured to generate a light pattern projected towards the target object;
• a controller operative to change the position of the focus plane of the imaging lens arrangement during at least a fraction of a first frame exposure time period when a first image is captured with the imaging sensor, to process the first image to determine an optimized position of the focus plane of the imaging lens arrangement, and to cause the imaging sensor to capture a second image during a second frame exposure time period when the position of the focus plane of the imaging lens arrangement during at least part of said second frame exposure time period is maintained at the optimized position as determined from processing the first image.