Active optical alignment station (camera module active alignment)

01

Set the alignment method and the focus budget it must meet

Commonlands, a camera lens maker, describes active alignment as positioning the lens relative to the powered image sensor in up to six degrees of freedom while scoring through-focus sharpness on live video — a system SFR measurement of the assembled lens and sensor, not the lens MTF on a data sheet — and then locking the position with UV-cure adhesive. Because the sensor is streaming, each lens is aligned to the true position of its own die, absorbing placement and stack-up tolerances; the company notes that errors inside the lens or sensor package, die warp, field curvature and adhesive shrinkage are not removed by the rigid-body move. [1]

It sets out the six axes as X, Y and Z translation (Z sets focus, X and Y decentre) and tip, tilt and rotation (tip and tilt set the corner focus gradient, rotation sets geometric registration), and contrasts a threaded M12 lens, which controls only Z. Its worked example: on a 1/2.3-inch sensor with a corner image height of about 3.95 mm, a working f-number of 2.0 and an allowed blur of 3 µm give a depth-of-focus budget of ±6 µm, and a tilt of 1.5 mrad (about 0.09°) alone moves one corner to +6 µm and the opposite corner to −6 µm, leaving nothing for Z or field curvature. [1]

A patent application assigned to Semiconductor Components Industries (onsemi) describes the conventional AA loop: a calibration target is viewed through the camera optics, contrast-detection algorithms measure edge contrast, and a multi-axis manipulator moves the lens to maximise it; it proposes using phase-detection pixels in the sensor to tell the alignment system how far and in which direction to move, with computer-controlled positioners able to move the lens in one to six axes, and the alignment locked by curing UV adhesive that stays uncured during alignment. [2]

Give the supplier the module drawing (lens barrel, holder, sensor package and board), sensor interface and resolution, pixel size, working f-number, field of view and object distance, the target and image-quality metric (SFR, MTF, contrast), centre and corner limits, the axes that must be adjusted, required cycle time and yield, and whether fixed-focus or autofocus modules are built.

02

Set the positioner, adhesive dispense and cure

Physik Instrumente (PI) describes hexapods for six-axis active optical alignment as a single platform on six motorised struts, equivalent to an XYZ stack with a rotation stage and two-axis goniometer, whose pivot point can be placed anywhere in space — such as at an optical focus — and whose controller adds a waveform generator, data recorder and gradient-search alignment routines; it says multiple hexapods carrying lens elements can optimise MTF simultaneously, and that optimisation can continue during adhesive curing to correct curing stresses. [3]

Its H-811.S2 miniature hexapod data lists travel of ±17 mm in X, ±16 mm in Y and ±6.5 mm in Z, rotation of ±10°, ±10° and ±21°, maximum velocity 25 mm/s (10 mm/s recommended), minimum incremental motion of 1 µm in X and Y and 0.5 µm in Z, unidirectional repeatability of ±0.5 µm in X and Y, ±0.2 µm in Z and ±6 µrad in tip and tilt, stiffness 0.7 N/µm in X and Y and 8 N/µm in Z, a load of 2.5 kg with the base horizontal (0.9 kg in any orientation) and an operating range of 0 to 50 °C. [4]

Commonlands lists the AA cycle as: dispense adhesive beads on the holder or barrel (the glue gap must absorb the whole Z range being corrected); grip and coarse-position the lens while the sensor streams video; sweep through Z scoring SFR at the centre and four corner regions; move tip, tilt, X, Y and Z until centre and corner scores peak inside one shared window; then cure with UV LEDs within seconds while the gripper holds the pose, with the target pre-offset by the characterised cure shrinkage, followed by thermal post-cure where the chemistry needs it and an end-of-line through-focus check. It notes UV acrylates cure fastest, modified epoxies, "often dual-cure UV plus thermal, are more stable", all adhesives shrink, and a single fibre under the bond line becomes a permanent tilt. [1]

Editorial calculation: against the ±6 µm example budget above, a tip-tilt repeatability of ±6 µrad moves a 3.95 mm corner by about 3.95 mm × 6 µrad ≈ 0.024 µm, roughly 0.4% of the 1.5 mrad tilt that would consume the whole budget; in this example the positioner's repeatability is not the limiting term, so ask the supplier for measured post-cure shift and end-of-line yield. [1] [4]

03

No station maker linked yet: what to ask for

No active alignment station maker is linked to this page yet. When you request quotations, ask each for positioner data in the form PI publishes for the H-811.S2 and for measured post-cure shift on a module like yours.

04

Positioner, gripper and fixture, target, scoring software, dispenser, UV head and controller

The rows follow the AA cycle described above, from holding the lens to curing the bond.

05

Travel, repeatability, speed, load and cure for the quotation

The focus budget and cycle time come from your module and line. The middle column uses PI H-811.S2 data and the Commonlands worked example; achieved post-cure accuracy must come from the supplier.

06

Send the module, budget and line data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Module: [lens; holder; sensor; board; fixed focus or autofocus]
Budget: [pixel size; f-number; field; tilt and Z tolerance]
Measurement: [target; SFR or MTF; centre and corner limits]
Motion: [axes; travel; repeatability]
Bonding: [adhesive; UV and thermal cure; shrinkage offset]
Line: [cycle time; yield; data logging; quantity]

See manufacturer records Send an enquiry through CNFX