Lens holder to compensate for optical focal shift by thermo-mechanical expansion

A mobile device, comprising:

• a camera module comprising:
• a lens assembly having a particular optical design, the lens assembly including at least:
• a lens barrel;
• and
• multiple lens elements embedded within the lens barrel,
• wherein a change of temperature causes an optical focal shift that is determined according to a particular optical thermal shift rate associated with the particular optical design;
• a lens holder having a lens holder coefficient of thermal expansion (CTE) to compensate for the optical focal shift by thermo-mechanical expansion, wherein:
• a first area of the lens holder is attached to the lens barrel using a lens attach adhesive;
• and
• the change in temperature causes a length expansion of the lens holder that is determined at least in part according to the lens holder CTE;
• an image sensor assembly that includes at least:
• an image sensor configured to capture light passing through the multiple lens elements and to convert the captured light into image signals;
• and
• a substrate coupled to the image sensor,
• wherein the lens holder is attached to the substrate using a holder attach adhesive;
• wherein:
• a total defocus rate is determined based on a difference between the particular optical thermal shift rate and a holder expansion rate of the lens holder, and wherein the total defocus rate satisfies an image quality performance metric;
• the image quality performance metric is a just-noticeable-defect (JND) metric associated with an unsatisfactory loss in image sharpness;
• the JND metric corresponds to a threshold defocus rate value within a range of 0.1 μm/° C. to 0.2 μm/° C.;
• and
• the total defocus rate satisfies the JND metric when the total defocus rate is less than the threshold defocus rate value;
• a display;
• and
• one or more processors configured to cause the display to present an image based at least in part on one or more of the image signals from the image sensor.

An article of manufacture, comprising:

• a lens assembly having a particular optical design, the lens assembly including at least:
• a lens barrel;
• and
• multiple lens elements embedded within the lens barrel and having an optical axis,
• wherein a change of temperature causes an optical focal shift that is determined according to a particular optical thermal shift rate associated with the particular optical design;
• and
• a lens holder having a lens holder coefficient of thermal expansion (CTE) to compensate for the optical focal shift by thermo-mechanical expansion, wherein the lens holder CTE is within a range of 100 parts-per-million (ppm)/° C. to 140 ppm/° C., and wherein:
• a first area of the lens holder is attached to the lens barrel using a lens attach adhesive that comprises a first epoxy material having a lens attach CTE within a range of 70 parts-per-million (ppm)/° C. to 100 ppm/° C.;
• and
• the change of temperature causes a length expansion of the lens holder that is determined at least in part according to the lens holder CTE.