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The Visitech technology glossary

DLP imaging, direct imaging lithography and additive manufacturing carry a vocabulary that is half acronym. This is what we mean by each of them — in plain terms, written by the engineers who build the hardware.

A to Z

Every term, defined

Search for a term, or narrow the list to a theme. Every entry links to itself, so you can send a colleague straight to the definition you meant.

32 terms

#

4K
A DMD resolution of 4096 × 2160 — nearly nine million native pixels addressed in a single exposure, without stitching two smaller frames together.

C

Calibration camera
The camera that measures the substrate — fiducials, distortion, position — before exposure, so the pattern can be corrected to it. It is what makes per-panel correction possible rather than theoretical.
Contrast ratio
The ratio between the light in an exposed pixel and the light leaking into one that is off. Low contrast fogs the areas meant to stay unexposed, which shows up as lost line/space rather than as a dim picture.

D

DLP
Digital Light Processing — Texas Instruments' imaging technology, built on a chip of millions of individually tilting micromirrors. It is what lets a photohead form a whole pattern at once, with no mask and no moving optics.
DMD
Digital Micromirror Device — the DLP chip itself. Each micromirror is one pixel: tilted one way it sends light to the substrate, tilted the other it sends it into a beam dump. The DMD type largely sets a photohead's resolution and speed.
DMD Type
Which Texas Instruments micromirror device is in the head. It sets the native resolution and the frame rate, and with the lens it sets the pixel pitch — so it is the first line of a datasheet worth reading.

E

Edge blending
Overlapping two projected fields and grading the light across the overlap, so the seam between them does not show as a line in the finished layer.

F

Frame rate
How many patterns per second the DMD can display. With data throughput it sets how fast a scrolling exposure can run.

L

LASER
A light source of a single, tightly defined wavelength. Some LLS heads offer a laser instead of an LED where the process needs the narrower spectrum and the higher power density it gives.
LED
Light-emitting diode. The light source in most LUXBEAM heads: it switches instantly, has no warm-up and no lamp to replace, and its output is set electronically rather than with a shutter.
Lens
The projection optics between the DMD and the substrate. The lens choice sets the pixel pitch, the field size and the working distance together — they cannot be picked independently.
Light engine
The optical subsystem that turns image data into a projected pattern: light source, DMD, projection optics and the electronics that drive them. The LRS range are light engines.
Light source
What produces the light: an LED array or a laser. It sets the wavelength, the available power and, through its stability, how repeatable the exposure is.

M

Metrology
Measuring the shape and size of physical objects; at Visitech, DLP-based 3D metrology. A projector casts precise light patterns onto a surface and a camera reconstructs its shape from how the patterns deform. Visitech Americas, the former Keynote Photonics team, serves this market.
Mounting distance
The distance from the head's mounting face to the substrate — the number an integrator actually builds the frame to, since it is measured from the surface they bolt to.

N

Native image size
The area one exposure covers at the work plane, with no stitching or stage movement. Pixel pitch multiplied by the DMD's resolution.
NIR
Near-infrared — light just beyond the red end of the visible spectrum. NIR heads are used where the process is driven by heat rather than by a photochemical reaction, such as sintering.

O

Optical multiplexing
Combining several light paths into one output, to put more power through a single head than one source could deliver.
Optics
The lenses and mirrors that carry light from the source to the DMD and from the DMD to the substrate.

P

Photohead
A complete imaging unit — DMD, optics, light source, driver and control electronics in one housing — that a machine builder mounts into their own system. It exposes the pattern; the machine around it handles the substrate.
Pixel pitch
The distance from one projected pixel to the next at the work plane, in microns. Together with resolution it sets both the field size and the smallest feature.
Power uniformity
How evenly the light is distributed across the exposed field, as a percentage. Uneven power means the same pattern develops differently in different places, so this number limits what the line-width spec can honestly claim.
Projector
An optical unit that images a pattern onto a surface at a distance. An industrial projector is specified by its output power, wavelength and pixel pitch at the work plane, not by brightness and contrast.
Projector output power
The optical power the head delivers at the work plane, in watts. With the material's required dose it is what sets how fast a layer can be exposed.

R

Resolution
How small a feature the system can form. In a DLP system it follows from the DMD's pixel count and the optics that image it onto the substrate.

S

Stitching
Building one large pattern out of several exposures placed side by side. The accuracy of the joins is what decides whether the result behaves as one continuous pattern.
Sub-pixelation
Placing an edge between two pixels rather than on one, by modulating what the neighbouring mirrors do. It buys a finer effective grid than the pixel pitch alone would give.

W

Wavelength
The colour of the light, in nanometres. It has to match what the resist or the material responds to — 365, 375, 385, 405 nm are the usual UV choices, with NIR used where the process is thermal.
Working distance
The distance from the last optical surface to the substrate. It is fixed by the lens, and it is one of the first constraints a machine has to be designed around.
WQXGA
A DMD resolution of 2560 × 1600. The workhorse format across much of the LUXBEAM range: a good balance of field size against pixel pitch for both lithography and additive manufacturing.
WUXGA
A DMD resolution of 1920 × 1200.
WXGA
A DMD resolution of 1280 × 800 — the compact format, chosen where a smaller, faster frame suits the process better than a larger one.

Still not clear?

Ask the people who built it

A definition only goes so far. Tell us the substrate, the line/space you are aiming at and the format, and we will come back with what it means for your machine — usually within two business days.