1, Problem Background:

During the project, I encountered several instances where, after generating the image, half of the screen was sharp while the other half was blurry—and even when I refocused, the issue persisted.

But it got better after I switched to a different lens. This must be a problem with the lens quality, but what exactly caused this issue with the lens?

2Problem Analysis:

Ideally, the imaging configuration of the module is as shown in the schematic diagram below, with the lens and sensor positioned directly opposite each other.

The imaging result shows that the center of the image is the sharpest, while the clarity at the edges is slightly lower (this is a normal phenomenon, as cameras use convex lenses—light refraction becomes greater toward the edges).

This causes greater deviations in the light’s propagation trajectory, so the light no longer projects accurately onto the image sensor, thereby degrading the resolution at the image edges.

And now, the problem we’re facing is that half of the image is blurry while the other half is perfectly sharp. This is abnormal and unacceptable.

The primary reason for this issue lies in the camera packaging process, which involves multiple stages of assembly of components such as the image sensor, lens mount, motor, lens, and circuit board. As a result, the cumulative tolerances of these parts keep increasing.

Ultimately, the effect reflected on the camera is that the sharpest part of the photo may be off-center, and the sharpness at the four corners may be uneven.

The following are diagrams illustrating the two phenomena that cause this issue.

a、This is caused by assembly tolerances in the lens and barrel. If the lens is installed at an angle, the image projected onto the sensor will have inconsistent focus between the upper and lower portions, resulting in significant image quality degradation.

b、Due to assembly tolerances in the lens barrel and image sensor, a similar issue can arise, causing inconsistent focus between the upper and lower portions of the image on the sensor and resulting in significant deviations in image quality.

3So, how can we solve or avoid this kind of problem?

During the module assembly process, AA testing is required for all modules.Its full name is Active Alignment, which means...Active alignment is a technique used to determine the relative positions during the assembly of parts and components.

During the AA process, as each component is assembled, the equipment will inspect the semi-finished product being assembled and actively align itself according to the actual condition of the semi-finished product before proceeding to assemble the next component into place.

This active alignment technology can effectively reduce the assembly tolerances of the entire module, significantly improving the consistency of camera products and also opening up possibilities for packaging higher-end camera products.