Cognisys Stackshot?

Started Aug 14, 2019 | Discussions thread
mawyatt2002 Contributing Member • Posts: 502
Re: Cognisys Stackshot?

ClosePhoto wrote:

mawyatt2002 wrote:

Ellis Vener wrote:

John K wrote:

What are you photographing, what's the primary light source, and what macro lens/setup do you have to get to 4:1?

Asking cause I shoot single frames up to 5x.

Nothing complex: just rocks.

I wouldn't characterize all rocks as "nothing complex", some rocks & minerals can be very challenging because of the complex surface reflections.

Yes, things certainly get complicated when the subject requires significant lighting yet many surfaces are reflective.

FOV: 6mm

Yes lighting these kind of subjects is a challenge indeed!!

I've had to deal with surface reflections with some silicon chips I've imaged that have small 40~100um solder balls all over the chip for attachment. These are like tiny spherical mirrors, and reflect from every direction. The initial lighting solution to create an absolutely uniform lighting was quadruple diffusion using dual light tents, one inside the other and double diffused strobes, used up to 11!! Now I still use the light tents, sometimes dual tents, up to 7 strobes and use a white styrofoam cup attached to the microscope objective lens for higher magnifications. This isn't ideal since the cup moves with the lens for stacking and thus changes the subject lighting, but the movement is only a couple mm. For lower magnifications the cup is attached to a fixture and the lens "pokes" thru the end of the cup. BTW these cups are some of the best diffusers I've found for studio work, they are cheap available in various sizes, but they do eat light so you need lots of optical power.

Here's a large crop (can't show entire chip image (~20mm by 18mm), it's proprietary) for a older chip oxidized solder ball, for reference the multiple small squares are ~2um I recall. The top is overexposed, note the dent on the ball top this is from wafer scale probing using test. Also note the slight jags in the middle left of the coil spiral, this is caused by slight sub-micron rail lateral movement rather than perfectly along the optical axis. The stacking software can't totally compensate for this because the slight movement across ~20mm creates a very slight perspective change since the custom lens assembly isn't perfectly telecentric (magnification doesn't vary with subject position nor distance).

Initial setup used for imaging chips with solder balls

Stackshot rail with custom lens assembly (Mitutoyo Objective)

Later setup


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