nanoDLP

It is too much work on nanodlp side for something which will be rarely used by users. And it will be hard to use.
But I could add grid and mask generator to the program. But data should be entered manually. Let me know if they will be useful.

I have worked on an alternative before.

• Display Grid

• RPi takes photo

• Detect projector area

• Calculate light strength in different positions

In addition to making mask, Also we could detect if the projector is out of focus or not. Even give clue to the users how much they are close to focus in realtime so they could dial focus ring until getting acceptable focus level.
And it could runs each time before print (do not start printer if it is out of focus), also data could be used to optimize cure time by detecting weakening blub output.

Unfortunately banding would not let me to calculate correct values. So I have abandoned the method. I think probably there is a suitable filter to use in these kind of conditions to prevent banding.

I will add both feature to my task lists.

From bottom but it could have angle as the new rpi cam has better resolution which could be used to fix perspective problems.

I think it will be ideal if we could work with resin filled vat using only red pattern which will not cause resin cure.

I am sure there are couple of other tricks would be possible (theoretically) using cam, for example alarming on low resin level or finding out uncalibrated platform (part of platform pressed hard on vat before other sides reaching that) Even with some resins, it will be possible to guess if parts are fallen or not. And etc.

I hope it will be possible to measure intensity of UV range light by measuring other part of light spectrum too (I guess blub light output should homogeneous at least for light spectrum range). We do not need absolute intensity value just relative value will be enough. Hopefully somebody could test those filters as I do not have access and knowledge to test these things.

Just another quick thought... if you project red squares separated by a grid (same size grid as for the UV sensor), then the algorithm could determine the average intensity within each square, and you could feed that into the mask generation algorithm used for the UV sensor.

The grid sample is the uvcal.stl document that can be downloaded here: http://www.buildyourownsla.com/forum/vi … 684#p11719

Three data samples (DS1, DS2, DS3) are this OpenOffice document: bicubic-interpolation-larry-v1.ods

That file also gives an example of bi-cubic interpolation. It was really slow, and I honestly don't remember if I left it in a working state.

Unfortunately almost all of new cast resins which I have tried were not transparent at all so It will be very hard to detect any piece on bottom of VAT.

I hope you don't mind me throwing out another concept idea...
For the UV sensor, rather than taking measurements and entering all that data in, here is another possible method:
For each grid section, allow the user to adjust the grayscale value being displayed (maybe one slider for big changes and a small slider for small changes)
The user could simply change the sliders on each grid section until the UV Sensor displays the value they want.  The user could indicate [done] and have that show on the UI. Perhaps the user could select the section they are working on, or the UI  enforces going in a particular order.
Then you could use the grayscale values to create the mask. Seems like it would be pretty accurate too. Thoughts?

As a side note, it would be really helpful if there were a way to regenerate the plates using the latest uploaded mask (so you don't have to re-create plates every time you change the mask). Even better if you could have multiple masks and select the mask on the plate (for example, you could use a brighter mask if you are only using the center portion of the plate for the print for faster prints). Just an idea. Thanks!

Lets finalize the plan based on your the most recent post.

1. User decide how many points she/he want to measure

2. Nanodlp display a grid based as Image and based on the number of points draw input boxes

3. User measure points on side and find out dimmest point

4. User enter dimmest point's value into interface

5. User select next input

6. Nanodlp disable all points and just display squire which corresponding input has been focused

7. User measure point and enter value

8. User continues step 5 ~ 7 for all points

9. User could press display mask anytime and mask will be displayed

10. User could check if whole surface brightness is same or continue tweak values

11. User click on export and mask will be saved

Do you have any suggestion?

I just saw the plan. I've been out-of-town. The challenge I have had is determining a mask from the measured points. I have found that the formula to go from measured points to a working mask is non-linear. I ended up using a 5th order regression to try to get a mask that makes all the points the same measured value.

To avoid all of that, I would suggest the following:
1. User decides how many points she/he wants to measure
2. Nanodlp displays grid based as an image (with no mask applied) on the projector, and displays a edit field for entering the dimmest values on the UI
3. User measures points to find the dimmest value
4. User enters dimmest point value into interface
5. User selects next input (or chooses a particular grid position - there may only be one wrong position that needs to be corrected)
6. Nanodlp displays only grid position #1 & user places sensor on grid position #1
7. User enters a value between 1 to 256 (1=full brightness, 256=black) to dim the grid position until the sensor reading matches the dimmest value
8. User continues steps 5 ~ 7 for all points
9. User could press display mask anytime and mask will be displayed (allow to choose with or without grid)
10. User could check if whole surface brightness is same or continue to tweak values
11. User click on export and mask will be saved

The difference here is that when you calculate the mask, you already know how much to dim at each grid position. You will not need to figure out some special formula to create the mask.

Note on #5: The user could press a [next] button or enter a grid position number
Note on #6: displays grid position #1 (if [next] is pressed) or the grid position number entered
Note on #7: may need to be 1 ~ 1024 (I'm not sure)

I agree ,  visual grid  better

#7 you cannot use 24bit for grayscale 8bit for each color as you need same value for all three colors for perfect gray, technically you could only have 256 shades of grey.

You can try mask generation feature on the beta version on projector calibration page.

It is not perfect right now, one the edges we need some smoothing/blurring and etc.