The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Category: Photography & Images

Taking & making images.

Mystery Microscope Objective Illuminator

Rummaging through the Big Box o’ Optics in search of something else produced this doodad:

Microscope objective illuminator – overview

It carries no brand name or identifier, suggesting it was shop-made for a very specific and completely unknown purpose. The 5× objective also came from the BBo’O, but wasn’t related in any way other than fitting the threads, so the original purpose probably didn’t include it.

The little bulb fit into a cute and obviously heat-stressed socket:

Microscope objective illuminator – bulb detail

The filament was, of course, broken, so I dismantled the socket and conjured a quick-n-dirty white LED that appears blue under the warm-white bench lighting:

Microscope objective illuminator – white LED

The socket fits into the housing on the left, which screws onto a fitting I would have sworn was glued / frozen in place. Eventually, I found a slotted grub screw hidden under a glob of dirt:

Microscope objective illuminator – lock screw

Releasing the screw let the fitting slide right out:

Microscope objective illuminator – lamp reflector

The glass reflector sits at 45° to direct the light coaxially down into the objective (or whatever optics it was originally intended for), with the other end of the widget having a clear view straight through. I cleaned the usual collection of fuzz & dirt off the glass, then centered and aligned the reflection with the objective.

Unfortunately, the objective lens lacks antireflection coatings:

Microscope objective illuminator – stray light

The LED tube is off to the right at 2 o’clock, with the bar across the reflector coming from stray light bouncing back from the far wall of the interior. The brilliant dot in the middle comes from light reflected off the various surfaces inside the objective.

An unimpeachable source tells me microscope objectives are designed to form a real image 180 mm up inside the ‘scope tube with the lens at the design height above the object. I have the luxury of being able to ignore all that, so I perched a lensless Raspberry Pi V1 camera on a short brass tube and affixed it to a three-axis positioner:

Microscope objective illuminator – RPi camera lashup

A closer look at the lashup reveals the utter crudity:

Microscope objective illuminator – RPi camera lashup – detail

It’s better than I expected:

Microscope objective illuminator – RPi V1 camera image – unprocessed

What you’re seeing is the real image formed by the objective lens directly on the RPi V1 camera’s sensor: in effect, the objective replaces the itsy-bitsy camera lens. It’s a screen capture from VLC using V4L2 loopback trickery.

Those are 0.1 inch squares printed on the paper, so the view is about 150×110 mil. Positioning the camera further from the objective would reduce both the view (increase the magnification) and the amount of light, so this may be about as good as it get.

The image started out with low contrast from all the stray light, but can be coerced into usability:

Microscope objective illuminator – RPi V1 camera image – auto-level adjust

The weird violet-to-greenish color shading apparently comes from the lens shading correction matrix baked into the RPi image capture pipeline and can, with some difficulty, be fixed if you have a mind to do so.

All this is likely not worth the effort given the results of just perching a Pixel 3a atop the stereo zoom microscope:

Pixel 3a on stereo zoom microscope

But I just had to try it out.

2020-09-30

Raspberry Pi HQ Camera Mount

As far as I can tell, Raspberry Pi cases are a solved problem, so 3D printing an intricate widget to stick a Pi on the back of an HQ camera seems unnecessary unless you really, really like solid modeling, which, admittedly, can be a thing. All you really need is a simple adapter between the camera PCB and the case of your choice:

HQ Camera Backplate - OpenSCAD model — HQ Camera Backplate – OpenSCAD model

A quartet of 6 mm M2.5 nylon spacers mount the adapter to the camera PCB:

RPi HQ Camera - nylon standoffs — RPi HQ Camera – nylon standoffs

The plate has recesses to put the screw heads below the surface. I used nylon screws, but it doesn’t really matter.

The case has all the right openings, slots in the bottom for a pair of screws, and costs six bucks. A pair of M3 brass inserts epoxied into the plate capture the screws:

RPi HQ Camera - case adapter plate - screws — RPi HQ Camera – case adapter plate – screws

Thick washers punched from an old credit card go under the screws to compensate for the case’s silicone bump feet. I suppose Doing the Right Thing would involve 3D printed spacers matching the cross-shaped case cutouts.

Not everyone agrees with my choice of retina-burn orange PETG:

RPi HQ Camera - 16 mm lens - case adapter plate — RPi HQ Camera – 16 mm lens – case adapter plate

Yes, that’s a C-mount TV lens lurking in the background, about which more later.

The OpenSCAD source code as a GitHub Gist:

	// Raspberry Pi HQ Camera Backplate
	// Ed Nisley KE4ZNU 2020-09

	//– Extrusion parameters

	/* [Hidden] */

	ThreadThick = 0.25;
	ThreadWidth = 0.40;

	HoleWindage = 0.2;

	function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
	function IntegerLessMultiple(Size,Unit) = Unit * floor(Size / Unit);

	Protrusion = 0.1; // make holes end cleanly

	inch = 25.4;

	ID = 0;
	OD = 1;
	LENGTH = 2;

	//- Basic dimensions

	CamPCB = [39.0,39.0,1.5]; // Overall PCB size, plus a bit
	CornerRound = 3.0; // … has rounded corners

	CamScrewOC = [30.0,30.0,0]; // … mounting screw layout
	CamScrew = [2.5,5.0,2.2]; // … LENGTH = head thickness

	Standoff = [2.5,5.5,6.0]; // nylon standoffs

	Insert = [3.0,4.0,4.0];

	WallThick = IntegerMultiple(2.0,ThreadWidth);
	PlateThick = Insert[LENGTH];

	CamBox = [CamPCB.x + 2*WallThick,
	CamPCB.y + 2*WallThick,
	Standoff.z + PlateThick + CamPCB.z + 1.0];

	PiPlate = [90.0,60.0,PlateThick];
	PiPlateOffset = [0.0,(PiPlate.y – CamBox.y)/2,0];

	PiSlotOC = [0.0,40.0];
	PiSlotOffset = [3.5,3.5];

	NumSides = 234;

	TextDepth = 2*ThreadThick;

	//———————-
	// Useful routines

	module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes

	Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);

	FixDia = Dia / cos(180/Sides);

	cylinder(r=(FixDia + HoleWindage)/2,h=Height,$fn=Sides);
	}


	//———————-
	// Build it

	difference() {

	union() {
	hull() // camera enclosure
	for (i=[-1,1], j=[-1,1])
	translate([i(CamBox.x/2 – CornerRound),j(CamBox.y/2 – CornerRound),0])
	cylinder(r=CornerRound,h=CamBox.z,$fn=NumSides);
	translate(PiPlateOffset)
	hull()
	for (i=[-1,1], j=[-1,1]) // Pi case plate
	translate([i(PiPlate.x/2 – CornerRound),j(PiPlate.y/2 – CornerRound),0])
	cylinder(r=CornerRound,h=PiPlate.z,$fn=NumSides);
	}

	hull() // camera PCB space
	for (i=[-1,1], j=[-1,1])
	translate([i(CamPCB.x/2 – CornerRound),j(CamPCB.y/2 – CornerRound),PlateThick])
	cylinder(r=CornerRound,h=CamBox.z,$fn=NumSides);

	translate([0,-CamBox.y/2,PlateThick + CamBox.z/2])
	cube([CamScrewOC.x – Standoff[OD],CamBox.y,CamBox.z],center=true);

	for (i=[-1,1], j=[-1,1]) // camera screws with head recesses
	translate([iCamScrewOC.x/2,jCamScrewOC.y/2,-Protrusion]) {
	PolyCyl(CamScrew[ID],2*CamBox.z,6);
	PolyCyl(CamScrew[OD],CamScrew[LENGTH] + Protrusion,6);
	}

	for (j=[-1,1]) // Pi case screw inserts
	translate([0,j*PiSlotOC.y/2 + PiSlotOffset.y,-Protrusion] + PiPlateOffset)
	PolyCyl(Insert[OD],2*PiPlate.z,6);

	translate([-PiPlate.x/2 + (PiPlate.x – CamBox.x)/4,0,PlateThick – TextDepth/2] + PiPlateOffset)
	cube([15.0,30.0,TextDepth + Protrusion],center=true);
	}

	translate([-PiPlate.x/2 + (PiPlate.x – CamBox.x)/4 + 3,0,PlateThick – TextDepth – Protrusion] + PiPlateOffset)
	linear_extrude(height=TextDepth + Protrusion,convexity=2)
	rotate(-90)
	text("Ed Nisley",font="Arial:style=Bold",halign="center",valign="center",size=4,spacing=1.05);

	translate([-PiPlate.x/2 + (PiPlate.x – CamBox.x)/4 – 3,0,PlateThick – TextDepth – Protrusion] + PiPlateOffset)
	linear_extrude(height=TextDepth + Protrusion,convexity=2)
	rotate(-90)
	text("KE4ZNU",font="Arial:style=Bold",halign="center",valign="center",size=4,spacing=1.05);

view raw HQ Camera Backplate.scad hosted with ❤ by GitHub

2020-09-29

Raspberry Pi Streaming Video Loopback
As part of spiffing my video presence for SquidWrench Zoom meetings, I put a knockoff RPi V1 camera into an Az-El mount, stuck it to a Raspberry Pi, installed the latest OS Formerly Known as Raspbian, did a little setup, and perched it on the I-beam over the workbench:

Raspberry Pi – workbench camera setup

The toothbrush head has a convenient pair of neodymium magnets affixing the RPi’s power cable to the beam, thereby preventing the whole lashup from falling off. The Pi, being an old Model B V 1.1, lacks onboard WiFi and requires a USB WiFi dongle. The white button at the lower right of the heatsink properly shuts the OS down and starts it up again.

Zoom can show video only from video devices / cameras attached to the laptop, so the trick is to make video from the RPi look like it’s coming from a local laptop device.

Start by exporting video from the Raspberry Pi:
```
raspivid --nopreview -t 0 -rot 180 -awb sun --sharpness -50 --flicker 60hz -w 1920 -h 1080 -ae 48 -a 1032 -a 'RPi Cam1 %Y-%m-%d %X'  -b 1000000 -l -o tcp://0.0.0.0:5000
```
The -rot 180 -awb sun --sharpness -50 --flicker 60hz parameters make the picture look better. ~~The bottom of the video image~~ There is no way to predict which side of the video will be on the same side as the cable, if that’s any help figuring out which end is up, and the 6500 K LED tubes apparently fill the shop with “sun”.

The -l parameter causes raspivid to wait until it gets an incoming tcp connection on port 5000 from any other IP address, whereupon it begins capturing video and sending it out.

Then, on the laptop, create a V4L loopback device:
```
sudo modprobe v4l2loopback devices=1 video_nr=10 exclusive_caps=1 card_label="Workbench"
```
Zoom will then include a video source identified as “Workbench” in its list of cameras.

Now fetch video from the RPi and ram it into the loopback device:
```
ffmpeg -f h264 -i tcp://192.168.1.50:5000 -f v4l2 -pix_fmt yuv420p /dev/video10
```
VLC knows it as /dev/video10:

RPi – V4L loopback – screen grab

That’s the edge of the workbench over there on the left, looking distinctly like a cliff.

The RPi will happily stream video all day long to ffmpeg while you start / stop the display program pulling the bits from the video device. However, killing ffmpeg also kills raspivid, requiring a manual restart of both programs. This isn’t a dealbreaker for my simple needs, but it makes unattended streaming from, say, a yard camera somewhat tricky.

There appear to be an infinite number of variations on this theme, not all of which work, and some of which rest upon an unsteady ziggurat of sketchy / unmaintained software.

Addendum: If you have a couple of RPi cameras, it’s handy to run the matching ssh and ffmpeg sessions in screen / tmux / whatever terminal multiplexer you prefer. I find it easier to flip through those sessions with Ctrl-A N, rather than manage half a dozen tabs in a single terminal window. Your mileage may differ.
2020-09-28
Monthly Image: Mantis Mating

The Praying Mantis in the Butterfly Bush is definitely female:

Praying Mantis Mating – front

I’d noticed her distended abdomen a day or two earlier, when it was highlighted in the sun and pulsing slowly. The indentations under the male’s legs shows the surface is definitely softer than the hard chitin of most insect armor:

Praying Mantis Mating – rear

The tip of the male’s abdomen twisted around to make contact, but I have no idea what all the little doodads common to both of them back there were doing.

The whole process started in mid-afternoon, they were still locked together six hours later, and the male was gone in the morning. The stories about female mantises eating the males seem greatly exaggerated, but she did manage to catch and eat a moth while otherwise engaged.

We’ll keep watch for ootheca on the tall grasses again, although we’ll never know the rest of their story.

2020-09-15
Cicada Time

Even though cicadas are completely harmless, Mary was quite startled to discover one crawling up the back of her garden pants:

Cicada – left front

It seems the cicada mistook her for a tree.

They’re handsome creatures:

Cicada – left dorsal

They’re very conspicuous on fabric:

Cicada – right dorsal

I teleported it to a maple tree, where it was better camouflaged:

Cicada – on tree – right

When last seen, it was headed upward at a pretty good pace. We wished it well on its adventures …

2020-09-13
Striped Hairstreak Caterpillar

Mary found this gadget gnawing holes in a bean:

Striped Hairstreak Butterfly – caterpillar

The lump on the right is frass, not a mini-me tagging along behind.

We had no clue what it might be when it grew up, but Google Lens suggested a Striped Hairstreak Butterfly caterpillar and, later that day (and for the first time ever!), we saw an adult Hairstreak fluttering on a goldenrod in the corner of the garden.

As with all caterpillars, you’d never imagine the adult butterfly. It seems they move their hind wings to make predators aim at the south end of a northbound butterfly …

2020-09-12
Praying Mantis On Duty

A Praying Mantis has once again taken up watching over the Butterfly Bush:

Praying Mantis – waiting

I made a slight noise that prompted an immediate weapons lock:

Praying Mantis – attentive

We’ve watched her stalk and capture a bumblebee, as well as chow down on one of the myriad moths feeding on the bush at night.

As always, if I were smaller, I’d be worried …

2020-09-06