Take a peek at our newest projector:
A 4K Ultra-High-Definition UV Projector designed specifically for Additive Manufacturing!

May 6, 2019 by Keith Elliott

Keynote Photonics’ newest UHD projector gives you unparalleled 3D printing performance in a compact, production-ready package.

Keynote Photonics is now shipping pre-production quantities of our newest projector:  the LRS-4KA.  This Ultra High Definition UV projector uses Texas Instruments’ (TI) new .66 inch UHD DMD (DLP660TE), and is powered by Keynote’s Photonics’ custom control electronics.  By combining our advanced electronics with a compact opto-mechanical design, we are able to display over 8 million pixels using an incredibly small package.  As a result, the LRS-4KA provides a great projector for your own industrial 3D printer.   

Designed specifically for stationary, high-resolution stereolithography applications, the LRS-4KA will be a core element of the next-generation 3D printers.  With complete control of an integrated optical actuator, you can address 8.3 million locations, enabling the manufacture of extremely high-resolution parts.

Developed in close partnership with Visitech Engineering (Germany), the optics include the choice of two high-performance projection lenses.  Using the DMD’s 5.4-micron mirrors and the optical actuator, these lenses can print 3D features as small as 32.5 microns.  If a larger build area is more important for your application, you can select a different projection lens and adjust the working distance to increase the image size by 3.5x.


OK, but how does it work?

TI’s 4K DMD uses the principle of super-resolution.   Super-resolution allows you to combine multiple data sets from slightly different perspectives, thereby dramatically increase the resolution of the final data.  For example, by shifting the image ½ pixel and then displaying a 2nd set of data and , we can effectively double our resolution.   As a result, we can achieve 8 million-pixel resolution with only 4 million mirrors.

Due to its incredible speed, this technique is especially well-suited to DLP™ projection technology.  The projector shifts the image by using an additional lens in the projection optics.  This lens is connected to a voice coil, which can shift the image ½ pixel along the diagonal of the mirror.

To take advantage of this technique, the input data needs to consist of two separate 2716×1528 images.  When exposing the resin, your first exposure will use the “red” data set.  After that exposure is complete, the optical actuator will then shift the projected image ½ pixel and then expose the 2nd set of data (the “yellow” pixels).  This technique can create much smoother surfaces and can double the resolution of any edges…and that’s exactly where the resolution is needed.


Watch out for projectors that try to mess with your data!

You can only take full advantage of this incredible resolution if the electronics are designed to accept data as two separate images of 2716×1528 resolution (the native resolution of the DMD).

Unfortunately, most companies are only copying TI’s video reference design, which is tailored for TV applications, not 3D printing.  Those designs will only accept 3840×2160 data (the standard 4K video format).  However, they will need to scale and resample the input data to convert it to 2716 x 1528.  Consequently, their electronics can introduce errors in your 3D print that you don’t want.

Keynote Photonics’ design always accepts data as two separate images of 2716×1528 resolution.  This matches the DMD perfectly and doesn’t require the projector to scale and resample your input.



8,300,096 pixels!!!  How should I use them?

Even though you’ve got 8 million pixels of resolution to play with, you might not always want to use them. There are different ways to use this projector and, with Keynote’s design, you can choose the method that’s best for your particular application.


Option 1:  Every layer uses all of the pixels:

To get the highest resolution possible for every layer, expose the first set of data with the optical actuator in Position 1.  Then, after the resin has hardened, shift the image to Position 2 and expose the 2nd set of data.

The result is that every layer in your print will have the maximum possible resolution.  Note how the second set of data is extremely sparse since, in this example, the added detail is only along the edges of the image.






Option 2:  Alternate the image shift on every other layer:

If you want to speed up your build, you can limit the image shift to every other layer.  Although this can still create features that are as small as half a pixel, it does it in a manner that only uses half the time.








Option 3:  Customize the exposure on every layer:

If you are developing your own slicer, you can take full advantage of the projector’s versatility by using both option 1 and option 2 throughout the build.

This way you don’t have to make compromises.  You can choose the best exposure process for every layer depending on its complexity.








12 bits of resolution ensures an even exposure across your entire build.

3D prints are considered binary in that you either want a pixel exposed or not exposed.  But you should plan on compensating for any roll-off in the projection optics or your resin bath design so that every pixel receives the same integrated power across your entire build area.  The LRS-4KA provides up to 12 bits of grey-scale compensation to achieve a perfectly balanced exposure across your projected image.


A compact package makes it easy to integrate.

If you are integrating a 3D printer into your production flow, you need the projector to be as small as possible.  Our 4K industrial projector has one of the smallest form factors available.  Moreover, the cable connections and cooling vents are located on the sides of the projector.  This allows the back of the projector to rest on the bottom of your 3D printer, with the lens pointed upward toward your resin bath.

Another helpful feature is the user replaceable LED light source.  By quickly changing the wavelength of the projector’s light output, the same projector can be used to work with a variety of resin material.  Although a 405nm high-power LED is the standard light source, 365 nm, 380 nm, and 460 nm sources are also available.  If you use a variety of resins, you may want to keep a variety of LEDs in stock.

A small number of our pre-production models are available now.  Although the pre-production design already projects an impressive 2 watts of UV power, our production design will provide a significant increase in output power, enabling even faster build times.  The delivery of production models will start in late 3Q.

Let us help…

If you’d like further information on this product or would like to discuss developing your own custom product using DLP technology, please contact us.

Keynote Photonics is an authorized provider of custom DLP electronics and projection systems. Our systems are currently helping customers develop and produce a variety of solutions for high-resolution display, 3D scanning, 3D printing, and UV exposure.


DLP® and the DLP logo are registered trademarks of Texas Instruments


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