Long-Term Degradation of Optical Performance in Smartphone Camera Modules: Mechanisms and Mitigation Strategies

Smartphone camera modules achieve diffraction-limited or near diffraction-limited imaging performance at the time of manufacture, relying on sub-micron alignment between multiple lens elements, the image sensor, and compact electromechanical actuators. Users routinely observe, however, that image quality — sharpness, contrast, and low-light performance — declines measurably over a device's typical two-to-five-year service life, independent of software changes. This review examines four physical degradation mechanisms responsible for this decline: (i) creep and fatigue of the adhesive bonds that maintain lens-to-sensor alignment under repeated thermal cycling; (ii) mechanical wear in voice coil motor (VCM) actuators used for autofocus and optical image stabilization; (iii) ingress of particulate matter and moisture through imperfect module seals; and (iv) abrasion of thin-film anti-reflective coatings on the protective cover lens. Each mechanism is discussed with reference to its underlying physics, its measurable effect on standard image-quality metrics such as the modulation transfer function (MTF), and practical mitigation strategies available to end users and manufacturers.