high resolution optical encoder patterns.

[Cory Seligman]

Hi all.

I've successfully made a linear optical encoder with a stroke of about
25cm using a flattened steel rod with a nice shiny surface, and gluing
on a laser printed transparency with a pattern of stripes. This works
find with a 1mm pattern, and a homemade detector. The detector is an
IR LED, a small lense and a Honeywell HLC2701 encoder detector
chip/opto thingy.

No worries, except it's fiddly. The lense and detector and pattern
have to be adjusted just right, and it's hard to put together.

So I got some Agilent HEDR-8100 detector chips. they have the lenses
built in and do all the hard work for you. The only problem is that
they're 150 lines per inch, which is more than I can do reliably on a
laser printer. So I'm looking for alternatives.

Does anyone know of somewhere I can get stripes like that printed
directly on the steel? Or etched?

Any thoughts on producing a clear strip with black stripes
photographically?

Or maybe a replacement reflective optical encoder detector that works
on a 1mm stripe spacing? As far as I can tell, the Agilent one is the
only device of its type.

Thanks in advance,
Cory

 

[Rod Speed]

"Cory Seligman" <coryms+google@azazel.eng.monash.edu.au> wrote in message news:a64581c0.0309242126.7a4fe4ee@posting.google.com...

Hi all.

I've successfully made a linear optical encoder with a stroke of about
25cm using a flattened steel rod with a nice shiny surface, and gluing
on a laser printed transparency with a pattern of stripes. This works
find with a 1mm pattern, and a homemade detector. The detector is an
IR LED, a small lense and a Honeywell HLC2701 encoder detector
chip/opto thingy.

No worries, except it's fiddly. The lense and detector and pattern
have to be adjusted just right, and it's hard to put together.

So I got some Agilent HEDR-8100 detector chips. they have the lenses
built in and do all the hard work for you. The only problem is that
they're 150 lines per inch, which is more than I can do reliably on a
laser printer. So I'm looking for alternatives.

Does anyone know of somewhere I can get stripes like that printed
directly on the steel? Or etched?

Any thoughts on producing a clear strip with black stripes
photographically?

Or maybe a replacement reflective optical encoder detector that works
on a 1mm stripe spacing? As far as I can tell, the Agilent one is the
only device of its type.

Or use an optical mouse that doesnt need
anything special on what the sensor passes over.

 

[Paul Burke]

Cory Seligman wrote:

Does anyone know of somewhere I can get stripes like that printed
directly on the steel? Or etched?

Any thoughts on producing a clear strip with black stripes
photographically?

If you get hold of some old HP Deskjet printers, they have a nice little

linear encoder (a transparent plastic strip) for the head positioning
system. It's about the width of an A4 sheet and probably has a
resolution of 300DPI! I expect they used to produce the stuff in long
lengths, so maybe HP have it in their catalog somewhere.

Paul Burke

 

[David]

So I got some Agilent HEDR-8100 detector chips. they have the
lenses
built in and do all the hard work for you. The only problem is
that
they're 150 lines per inch, which is more than I can do reliably
on a
laser printer. So I'm looking for alternatives.

In terms of getting a better printed resolution trying asking a
graphic designer studio or a printer if they can produce a
photographic bromide image or a photo-plot.

BTW, why does the 150 lpi limit your application? You only need
to count the transitions, and as long as you know how many pulses
there are per distance unit you can scale it. You might need to
make your lines nice and sharp and solid, but unless I am missing
something it should still see them and encode accordingly. The
HEDR-8000 does 75 lpi, would that be easier?

 

[Fritz Schlunder]

"Cory Seligman" <coryms+google@azazel.eng.monash.edu.au> wrote in message
news:a64581c0.0309242126.7a4fe4ee@posting.google.com...

Hi all.

I've successfully made a linear optical encoder with a stroke of about
25cm using a flattened steel rod with a nice shiny surface, and gluing
on a laser printed transparency with a pattern of stripes. This works
find with a 1mm pattern, and a homemade detector. The detector is an
IR LED, a small lense and a Honeywell HLC2701 encoder detector
chip/opto thingy.

No worries, except it's fiddly. The lense and detector and pattern
have to be adjusted just right, and it's hard to put together.

So I got some Agilent HEDR-8100 detector chips. they have the lenses
built in and do all the hard work for you. The only problem is that
they're 150 lines per inch, which is more than I can do reliably on a
laser printer. So I'm looking for alternatives.

Does anyone know of somewhere I can get stripes like that printed
directly on the steel? Or etched?

Any thoughts on producing a clear strip with black stripes
photographically?

Or maybe a replacement reflective optical encoder detector that works
on a 1mm stripe spacing? As far as I can tell, the Agilent one is the
only device of its type.

Thanks in advance,
Cory

Have you tried using a high quality ink jet type printer with ink jet
transparency? Even the local Walmart will sell Lexmark printers that claim
up to 2400dpi or up to 11ppm capability and only cost $35. 2400dpi aught to
be way more than adequate for the job. You have to use the right type of
transparency though (a laser transparancy or the wrong type of ink jet
transparency will yeild terrible results).

Using my ordinary Epson ink jet printer I regularly develop etched copper
PCBs with line sizes sometimes as small as say 5 mils wide. I haven't
extensively tested smaller features because I haven't really had much need
for it, but I think it is certainly possible given todays ink jet
technology. If you aren't going to be using any photoresist and copper
etching I should imagine the quality would be a fair amount better as well
(with just the plain transparency).

 

[nospam]

coryms+google@azazel.eng.monash.edu.au (Cory Seligman) wrote:

Any thoughts on producing a clear strip with black stripes
photographically?

Create your pattern with a PCB layout package, export to Gerber and get
your local PCB house to plot a sheet of it.

 

[Spehro Pefhany]

On 24 Sep 2003 22:26:12 -0700, the renowned
coryms+google@azazel.eng.monash.edu.au (Cory Seligman) wrote:

Any thoughts on producing a clear strip with black stripes
photographically?

They can be created on an imagesetter from a Postscript (or PDF) file.
I just paid $60 for two oversize pages on litho film, price seems to
be going up as more printing goes to direct-to-plate. But that would
be a heck of a lot of strips.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[Tim Shoppa]

coryms+google@azazel.eng.monash.edu.au (Cory Seligman) wrote in message news:<a64581c0.0309242126.7a4fe4ee@posting.google.com>...

Does anyone know of somewhere I can get stripes like that printed
directly on the steel? Or etched?

Any thoughts on producing a clear strip with black stripes
photographically?

At the very fine end, ruled diffraction gratings are available, but
they're in the hundreds or low thousands of lines per mm.

Ronchi targets are very high precision and have the resolution you
desire, but mounting them to your device may present some difficulties.

Getting a pattern put onto lith film is something your local
repro shop can do for you, and probably something you can deal with
in mounting.

You told us you want a resolution of a few hundred lines per inch, but
you didn't tell us how precisely they must be spaced. Others have
suggested using consumer-quality printers to do this, and those are
probably capable of giving the resolution you desire, but they are
very abysmal in terms of absolute precision.

Tim.

 

[Zak]

Cory Seligman wrote:

Any thoughts on producing a clear strip with black stripes
photographically?

A litho house can make this for you - even from your PC produced file.

They usually work with Postscript to produce a 2400 DPI output on silver
halide film. Huge sized are posible, but 30 cm wide wide is the beginning.

It shouldn't be expensive either.


Thomas

 

[Frank Bemelman]

"Cory Seligman" <coryms+google@azazel.eng.monash.edu.au> schreef in bericht
news:a64581c0.0309242126.7a4fe4ee@posting.google.com...

Hi all.

I've successfully made a linear optical encoder with a stroke of about
25cm using a flattened steel rod with a nice shiny surface, and gluing
on a laser printed transparency with a pattern of stripes. This works
find with a 1mm pattern, and a homemade detector. The detector is an
IR LED, a small lense and a Honeywell HLC2701 encoder detector
chip/opto thingy.

No worries, except it's fiddly. The lense and detector and pattern
have to be adjusted just right, and it's hard to put together.

So I got some Agilent HEDR-8100 detector chips. they have the lenses
built in and do all the hard work for you. The only problem is that
they're 150 lines per inch, which is more than I can do reliably on a
laser printer. So I'm looking for alternatives.

Does anyone know of somewhere I can get stripes like that printed
directly on the steel? Or etched?

Any thoughts on producing a clear strip with black stripes
photographically?

Or maybe a replacement reflective optical encoder detector that works
on a 1mm stripe spacing? As far as I can tell, the Agilent one is the
only device of its type.

If you place a transparent filter on top, also printed with 1mm stripes,
you don't need a very well adjusted sensor. When the rod with the stripes
move behind the filter, even you can clearly see that it moves. Most
optical encoders work like that, makes them get away with pretty coarse leds
and fotodiodes.

Situation 1:
# # # # # # # # # # # # # # # # # ROD
# # # # # FILTER

^^^ looks like 100% black from this point


Situation 1, rod moved a bit:
# # # # # # # # # # # # # # # # # # ROD
# # # # # FILTER

^^^ looks like 50% black from this point


Place two filters with the stripes 90 degrees apart for A & B signals.
The effect is named after Moire, it's inventor, I think.

--
Thanks,
Frank Bemelman
(remove 'x' & .invalid when sending email)

 

[Cory Seligman]

"Frank Bemelman" <bemelmanx@euronet.nl.invalid> wrote in message news:<3f747ee2$0$28885$1b62eedf@news.euronet.nl>...

"Cory Seligman" <coryms+google@azazel.eng.monash.edu.au> schreef in bericht
news:a64581c0.0309242126.7a4fe4ee@posting.google.com...

So I got some Agilent HEDR-8100 detector chips. they have the lenses
built in and do all the hard work for you. The only problem is that
they're 150 lines per inch, which is more than I can do reliably on a
laser printer. So I'm looking for alternatives.

If you place a transparent filter on top, also printed with 1mm stripes,
you don't need a very well adjusted sensor. When the rod with the stripes
move behind the filter, even you can clearly see that it moves. Most
optical encoders work like that, makes them get away with pretty coarse leds
and fotodiodes.

Place two filters with the stripes 90 degrees apart for A & B signals.
The effect is named after Moire, it's inventor, I think.

Thanks for the ideas. I have a suspicion that the optical devices I'm
using already exploit the Moire effect, since they appear to only work
at 150 lpi. This would indicate that they already have a 150lpi screen
internally.

The optical mouse sensor idea is something I already thought of, but
the specs for some of the modules they use show fairly lousy
repeatability, which I guess amkes sense. I need pretty good (0.5 mm
or so) repeatability.

I have yet to have any success with ink jet printer on transparencies.
The ink is either too think, blobbing up and obscuring the gaps, or
not dark enough to block the reflection. Perhaps I need better
stationary.

In any case, I've ordered the lower resolution (75 lpi) encoders. I've
printed out some 75 lpi stripes, and checked them under a microscope.
They look clear and distinct, so I'm just going to go with that.

thanks for the responses though.

Cory

 

[John Eaton]

Cory Seligman <coryms+google@azazel.eng.monash.edu.au> wrote:

: I have yet to have any success with ink jet printer on transparencies.
: The ink is either too think, blobbing up and obscuring the gaps, or
: not dark enough to block the reflection. Perhaps I need better
: stationary.

: In any case, I've ordered the lower resolution (75 lpi) encoders. I've
: printed out some 75 lpi stripes, and checked them under a microscope.
: They look clear and distinct, so I'm just going to go with that.

: thanks for the responses though.


Find an old hp ink jet that someone is tossing and salvage the encoder strip.


1/150 dpi.


John Eaton

 

[Rod Speed]

"Cory Seligman" <coryms+google@azazel.eng.monash.edu.au> wrote in message news:a64581c0.0310052014.27d17e70@posting.google.com...

"Frank Bemelman" <bemelmanx@euronet.nl.invalid> wrote in message news:<3f747ee2$0$28885$1b62eedf@news.euronet.nl>...
"Cory Seligman" <coryms+google@azazel.eng.monash.edu.au> schreef in bericht
news:a64581c0.0309242126.7a4fe4ee@posting.google.com...

So I got some Agilent HEDR-8100 detector chips. they have the lenses
built in and do all the hard work for you. The only problem is that
they're 150 lines per inch, which is more than I can do reliably on a
laser printer. So I'm looking for alternatives.

If you place a transparent filter on top, also printed with 1mm stripes,
you don't need a very well adjusted sensor. When the rod with the stripes
move behind the filter, even you can clearly see that it moves. Most
optical encoders work like that, makes them get away with pretty coarse leds
and fotodiodes.

Place two filters with the stripes 90 degrees apart for A & B signals.
The effect is named after Moire, it's inventor, I think.

Thanks for the ideas. I have a suspicion that the optical devices I'm
using already exploit the Moire effect, since they appear to only work
at 150 lpi. This would indicate that they already have a 150lpi screen
internally.

The optical mouse sensor idea is something I already thought
of, but the specs for some of the modules they use show
fairly lousy repeatability, which I guess amkes sense.

Makes no sense at all, you dont see any problem like that using a good one.

I need pretty good (0.5 mm or so) repeatability.

Should be completely trivial with a decent optical mouse
and the most you might want to do is make sure that what
you are running it on isnt dead smooth like glass etc.

I have yet to have any success with ink jet printer on transparencies.
The ink is either too think, blobbing up and obscuring the gaps, or
not dark enough to block the reflection. Perhaps I need better
stationary.

Yeah, thats completely trivial to do properly too. Basically
just the right combination of transparent film and ink.

In any case, I've ordered the lower resolution (75 lpi) encoders. I've
printed out some 75 lpi stripes, and checked them under a microscope.
They look clear and distinct, so I'm just going to go with that.

thanks for the responses though.

Cory

 

[Cory Seligman]

"Rod Speed" <rod_speed@yahoo.com> wrote in message news:<bltkuj$g1593$1@ID-69072.news.uni-berlin.de>...

"Cory Seligman" <coryms+google@azazel.eng.monash.edu.au> wrote in message news:a64581c0.0310052014.27d17e70@posting.google.com...

The optical mouse sensor idea is something I already thought
of, but the specs for some of the modules they use show
fairly lousy repeatability, which I guess amkes sense.

Makes no sense at all, you dont see any problem like that using a good one.

hey, yeah. You're right. They have good repeatability. I'll give em a
go for the next version of the prototype. As it is now, I have the 75
lpi encoders and they work fine with laser printed stripes.

I need pretty good (0.5 mm or so) repeatability.

Should be completely trivial with a decent optical mouse
and the most you might want to do is make sure that what
you are running it on isnt dead smooth like glass etc.

Yeah. It's machined steel, and an optical mouse picks it up fine. I do
have pretty limited space though, and it'd be a tight squeeze with the
sensors used in the mouses I've looked at so far. I'm sure they make
tiny ones though....

I have yet to have any success with ink jet printer on transparencies.
The ink is either too think, blobbing up and obscuring the gaps, or
not dark enough to block the reflection. Perhaps I need better
stationary.

Yeah, thats completely trivial to do properly too. Basically
just the right combination of transparent film and ink.

Yeah, I assumed so. But the combination I had was lousy.

Anyhow, it's all moot now, since the 75 lpi stuff all works fine, and
the laser printed stripes are nice and clear when glued to the steel
rod.

thanks anyhow,
cory