Agfa

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Agfa

COLOR - THERMOSUBLIMATION Agfa
Marc De Clerck
Agfa Gevaert n.v.
Medical Division
M. De Clerck
COLOR IMAGING Koln, January 20, 1999
Agfa Lectures - Fachhochschule Köln
1
COLOR - THERMOSUBLIMATION Agfa
OVERVIEW :
M. De Clerck
–
–
–
–
Principles of thermal sublimation printing
Market segments
Printing concept
Medical color printing
2
Principles of thermal sublimation printing
Agfa
M. De Clerck
-Basic principle
-Thermal head
-Donor
-Receiver
3
Basic principle
Agfa
Sublimation printing or dye diffusion thermal transfer [D2T2] printing
is a color hardcopy process that is capable of producing photo-graphic quality
images.
Thermal head
resistor element
donor ribbon
Substrate
dyes
Transferred dyes
Receiver coating
Substrate :PET
M. De Clerck
receicer sheet
4
Basic principle
Agfa
M. De Clerck
• continous tone printing [not binary, not screened]
• 2 sheet system [donor & receiver]
• 3 [Yellow, Magenta, Cyan]or 4 passes [+ K=black]
to generate color image
• difference of dye concentration is driving dye transfer
5
M. De Clerck
Basic principle
Agfa
6
Basic principle
Agfa
• physical process : dye is diffused and not sublimated
• process described by 3 equations :
• thermal diffusion process
Cp
∂T
∂ æ ∂T ö ∂ æ ∂T ö
= çK
÷ + çç K
∂y è ∂y
∂t ∂x è ∂x
• dye diffusion process
∂C ∂ æ ∂C ö ∂ æ ∂C ö
= çD
÷ + çç D
∂t ∂x è ∂x
∂y è ∂y
M. De Clerck
• diffusion coefficient
D=Do .exp[D1/Ru.T]
7
Temperature (degree)
Basic principle: temperature-transfer time
Agfa
360
340
320
300
280
260
240
220
200
180
160
140
120
100
80
60
40
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
T im e (m s )
M. De Clerck
dy e/rec
PET/dy e
head/PET
8
Basic principle: concentration-transfer time Agfa
receiver
donor
dye concent
0,45
0,4
0,35
0,3
0,25
0,2
0,15
0,1
0,05
0
0
0,5
1
1,5
2
2,5
3
3,5
4
4,5
5
5,5
D istance (µm)
M. De Clerck
8ms
6ms
4m s
10m s
9
Basic principle: density-transfer time
Agfa
4,5
4
3,5
OD
3
2,5
2
1,5
1
0,5
0
4
5
6
7
8
9
10
M. De Clerck
Pu lse W id th (ms)
EXP-12V
PRE-11V
EXP-11V
PRE-12v
10
Thermal Head: concept
Agfa
M. De Clerck
Origin: fax, label printers,...
11
Thermal Head: concept
exclusive protective
liquid glass :
wear, pinholes
Agfa
heating line
resistor layer (0.5um)
protective coating (7um)
glaze bulb (50um)
electrodes (1um)
ceramic substrate (0.9mm)
aluminium base plate (9mm) / heat sink
M. De Clerck
cross section of thermal print head
12
M. De Clerck
Thermal Head: operation
Agfa
13
Thermal Head: driving circuits
Agfa
thermal head voltage
shift
latch
register
register
V
th
= 14.7 V
2880 resistor elements
R = 2600 Ohm
e
2880
2880
bit
bit
resistor switches
SERIAL DATA
30 lines
clock
latch
6 MHz
STROBE (12 us)
M. De Clerck
print head driving circuits
14
Thermal Head: temperature profile
(°C)
temperature T
Agfa
e
T
e max
150
Te min
35
18
6
6
36
16
90
72
54
16
16
time
(ms)
transfer time
line time
M. De Clerck
temperature profile for different transfer time's
15
Thermal Head: driving method
Agfa
line time t l
transfer time t
t
skipped strobe pulse
expanded view
strobe time
t s
M. De Clerck
t son
strobe-on time
print head driving method
16
Thermal Head: thermal model
P e
Agfa
•Resolve non
uniformities
•increase sharpness
closed if element is heating
closed if head down
R
R
th e-d
T
+
T
e
th e-s
R
T s
C th e
C
th s-h
R
T h
C
th s
th h-a
+
th h
T a
d
-
R
th e-d
R
th e-s
R th
: thermal resistance (°C/W)
d: drum
C th
: thermal capacitance (J/°C)
e: element
T
: temperature (°C)
s: substrate
P
: power (W)
h: heatsink
a: ambient
M. De Clerck
thermal model of the print head
17
Thermal Head: types & production
Agfa
M. De Clerck
•Thick film :
•performance : lower cost [-15%], large size,
adressability up to 600dpi, higher variation R
•Production steps : screen printing , exposure and etching
thick glass paste doped with gold is put on substrate and
hardened under 900 C
• suppliers : Rohm [Japan]
18
Thermal Head: types & production
Agfa
M. De Clerck
•Thin film:
• performance : higher quality [uniformity]
resolution up to 600 dpi,
• production steps : sputtering and etching
of resistors, Al layers, conductors
• Suppliers: Kyocera, TDK, Toshiba
• based an automated manufacturing cost of
thin film heads for fax is 2000Yen
• history : Japan pushed fax thermal printing versus telex,
to communciate electronically Kanji text
19
Thermal Head: discussion
Agfa
Advantages :
• continous tone : foto quality
• solid state device : fully software controllable
• line printing : fast
M. De Clerck
Issues:
• impact printing or mechanical wear : glaze and donor
• differences resistors : measurement and calibration
• sharpness : electronic compensations
• chemical wear : glaze
20
Donor: concept
Agfa
receiver
Dye layer : 1.5um
stitching layer:
0.02um
PET : 5um
stitching layer:
0.02um
thermostable back
layer : 0.5um
M. De Clerck
slipping layer
head
21
Donor: properties of dyes
Agfa
M. De Clerck
• high absorption of light
• high diffusion rate into receiver
• low cost
• large color space
• high light stability in receiver
22
Donor: properties of dyes
Agfa
M. De Clerck
Graphic absorption
gamut
23
M. De Clerck
Donor: production
Agfa
• 1 cylinder per color and in register
• finishing in rolls
24
Receiver: concept
Agfa
donor
dye absorbing, hardening
layer : 4um
PET : 175um
[transparant, opaque]
anti-static :1um
matting :2um
sheet
M. De Clerck
drum
25
M. De Clerck
Receiver: production
Agfa
26
Market segments: history
Agfa
• starting point : ‘80’s intro SONY Mavigraph system
• Mavigraph = digital foto camera and A6 color sublimation printer
• but no success : low image quality camera , high price
• starting point for several Japanese compagnies to asses first
the capabilities of sublimation printing in their markets
M. De Clerck
• 4 markets will be discussed :
• consumer : photo
• proofing
• office
• medical
27
Market segments: photographic prints
Agfa
M. De Clerck
• where used ?
• home printing [A6] of digital camera’s images or
scanned photos
• professional photo printing of digital images :
• photo shop: interactive A5, A4 prints
[e.g AGFA Innova Touch ]
• amusement park : A5 prints of live attractions
• advantages :
• photo like image quality [ color, sharpness]
• stable image
• strong receiver media
28
M. De Clerck
Market segments: photographic prints
Agfa
• competition :
• home :
•ink jet printing with special consumables
• still lower quality
• low price printer : 500 DEM
• still expensive price for media : high ink filling
[A4: 2.5 DEM plain-6 DEM glossy]
• professional :
• conventional mini-lab with digital printer [CRT, laser]
• very high investment
• ink jet ?
• Low throughput
• low quality
29
Market segments: proofing
Agfa
M. De Clerck
• where used ?
• Provide in prepress environment hard copy to check
color and quality result , before starting the press
• advantages :
• access time [ 5’ for A3]
• image quality
• color matching
• BUT price : printer 25.000 DEM, media 14 DEM /A3
30
Market segments: proofing
Agfa
M. De Clerck
• competition :
• recently ink jet is coming up based on price decrease
• printer : 10.000 DEM [A3 format]
• media : 2 DEM = NEW
• better simulation on same plain paper
• still long print time : 15’
31
Market segments: office
Agfa
M. De Clerck
• where used ?
• Provide high quality color overheads [and paper like]
• advantages :
• access time [ 1-3’ for A3]
• image quality
• high density
• durability of print out
• BUT price : 5 DEM per A4
32
Market segments: office
Agfa
• competition :
•ink jet :
• low price printer
• price print out depending of fill factor [cartridge ]
• throughput and quality is improving
M. De Clerck
• [electrophotographic] laser printer :
• high price color printer [ 8.000 DEM]
• low price print out
• network, high throughput
• high quality text bl/wh print outs
• lower quality overheads
33
Market segments: medical
Agfa
M. De Clerck
• where used ?
• Provide hardcopy for medical diagnosis in radiology
• advantages :
• diagnostic image quality
• high density also on film
• paper and film media
• continous tone
• color matching
• durability of print out
• archivability
34
Market segments: medical
Agfa
M. De Clerck
• competition :
•ink jet :
• low price printer
• high price media [images]
• non diagnostic
• low throughput
• no stiff film sheet
• [electrophotographic] laser printer :
• medium price printer
• throughput lowers in Postscript / bitmap mode
• non diagnostic
• lower quality overheads
35
M. De Clerck
Printing concept
Agfa
36
M. De Clerck
Printing concept
Agfa
37
M. De Clerck
Printing concept
Agfa
Load donor & receiver
38
Printing concept
Agfa
M. De Clerck
Connection :
•power supply
•host [PC, SUN,..]
video RGB or
ethernet Postscript.
39
Printing concept: data flow
Acquisition
R
G
B
layout
6-8bit
M. De Clerck
Video RGB [1280x1024]
ethernet network [Postscript]
DA - convertion
Postscript RIP
W/L,
processing
6-8bit
# images /page
scaling image
correction
Agfa
engine
compenstions
Y
M
C
thermal
head
Heat
6-10bit
donor
Compensations
calibrations
bits - time slices
RGB-YMC
color matching
40
Printing concept: scaling algorithmes
Agfa
• nearest neighbour or replication :
• sharp
• pixel structure visible
• aliasing with non integer scaling factor
Interpolation funtion
E.g:.Step Transition
level
255
0
M. De Clerck
-1
0
+1
position
41
Agfa
• lineair :
• smooth
• “blurry”
• some aliasing with non integer scaling factor
level
255
0
M. De Clerck
-1
0
+1
position
42
Agfa
• high resolution cubic spline:
• f[x]=ax3 -5ax2 +8ax-4a
• a parameter : smooth to sharp
• limited aliasing with non integer scaling factor
level
255
0
M. De Clerck
-1
0
+1
position
43
Printing concept: RGB-YMC
Agfa
• input[= RGB image] converted to output YMC image[donor]:
• based on the color coordinates of RGB and of the donor dyes
a transfer look up tabel of 256 3 values is calculated [8 to 8bit]
• original RGB color space could be based on different devices
[e.g. CRT monitor]
M. De Clerck
• issues :
• saturated red ,blue and green are not easy to achieve in YMC
• processing a color image through look up table takes time
depending on CPU power. Speed is increased by limiting to 333
table and a lineair interpolating for the other points
• consequence is a possible hue deviation in the grey regions
44
Printing concept: color matching
Agfa
Fit color space original [monitor ] image to space print out:
• color space of monitor is different [larger] from space print out
• via mapping techniques [clipping, [non]-lineair] a best fit
is reached
M. De Clerck
• issues :
• monitor has larger L range than print out
• mapping could generate contouring in print out
• absolute color reproduction is not accurate anymore
• shift in hue of blue is easily seen
• shift in luminance of red is easily seen
45
Printing concept: performance issues
Agfa
M. De Clerck
TAKE CARE :
• color registration : pixel of every pass on same spot
• color reproduction : stability media, matching ,delta E <1?
• banding : thermal head non uniformity
• density non uniformity : temperature compensations
• color or bl/wh contouring : accuracy of processing [LUT, matching]
and printing > 8bit
• maximum density versus print time
• aliasing : algorithmes
• sharpness : dyes & receiver, thermal modelling, dpi of head
• adressability of head : not equal to sharpness
46
M. De Clerck
Printing concept
Agfa
47
Printing concept: assesment sublimation
Agfa
M. De Clerck
Advantages :
• continous tone - photographic quality [no screening artefacts]
• high density
• high spatial resolution and small contrast reproduction
• scratch resistance
• color reproduction
• price printer 1.000-25.000 DEM?
Disadvantages :
• price of media [but independent of contents]
• waste [donor]
• special receiver sheet
48
Printing concept: suppliers
Agfa
• Printers :
• Sony, Seiko, Mitsubishi, Agfa, Kodak,..
M. De Clerck
• Media :
• Sony, Seiko, ICI, Dai Nippon Printing, Agfa, Kodak,..
49
M. De Clerck
Medical color printing
Agfa
50

Agfa

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