Photographic printer

A photographic printer includes integral densitometry apparatus for performing scanned transmissive, large area transmissive, and reflective density measurements using a single light sensor. The densitometry apparatus includes a rotatable filter wheel supporting both scanning and large area transmissive filters used in making all of the density measurements. The scanning and large area density measuring apparatus use the same light projector as and share common optical hardware with that used to print pictorial negatives. The reflection densitometry apparatus includes a detachable holder for supporting reflective patches, and a second light source activated responsive to the introduction of the holder into the printer for illuminating the reflective patch.

REFERENCE TO RELATED APPLICATIONS 
Reference is hereby made to related, copending applications Ser. Nos. 
062,522, 062,304, and 062,523 filed concurrently herewith. 
BACKGROUND OF THE INVENTION 
The present invention relates generally to photographic printers and more 
particularly to a photographic printer which provides apparatus for 
measuring the scanned and large area transmissive densities of negatives, 
and the large area reflective density of reflective test patches. 
In the process of developing photographic negatives, printing the 
negatives, and developing the prints, it is necessary to measure various 
density characteristics of both negatives and prints. For example, to 
monitor the quality of a film processor, it is necessary to measure the 
transmissive characteristics of a developed strip of transmissive test 
patches, commonly referred to as a film process control strip. To properly 
control exposure when printing negatives, it is common practice to scan 
the transmissive characteristics of each negative at a plurality of 
discrete locations whereby to measure the scanned transmissive density of 
each negative. When printing certain types of negatives it may also be 
desirable to measure the large area transmissive density (LATD) of these 
negatives, in lieu of or in addition to the measurement of the scanned 
transmissive densities. To monitor the quality of a film processor, it is 
necessary to measure the LATD of transmissive test patches developed in 
the film processor. To monitor the quality of a paper processor, it is 
necessary to measure the reflective density of a developed strip of 
reflective patches, commonly referred to as a paper process control strip. 
To monitor the quality of a printer, it is necessary to measure the 
reflective density of a printer control test print, exposed in the printer 
and processed in the paper processor. These measurements are used to 
control the printing process. 
To perform these various densitometric measurements, photographic 
laboratories often must have available several pieces of sophisticated 
equipment, including transmissive and reflective densitometers. High costs 
are associated with purchasing and maintaining this equipment. 
Some printers include apparatus for performing one or two of the 
above-described densitometry measurements. U.S. Pat. No. 4,526,462 to Hope 
et al. shows a color printer incorporating red, green, and blue photocells 
connected to amplifiers for measuring the transmissive density of 
negatives, and a probe for measuring the reflective density of a test 
print. Both the reflective and transmissive densities are input to a 
microprocessor, which subsequently calculates exposure times for 
negatives. Hope et al. makes no provisions for measuring scanned 
transmissive densities of negatives. Further, the printer in Hope et al. 
requires the use of four separate light sensors to measure the various 
densities: one in the probe for measuring reflective densities, and three 
disposed at an apparent right-angle to the optical path for measuring the 
transmissive densities. Hope et al. suffers the disadvantages inherent in 
maintaining and calibrating this number of light sensors. 
U.S. Pat. No. 3,083,614 to Veit shows a photographic printer wherein a 
single photocell is pivoted between a first position where it is used to 
measure the transmissive density of a negative, and a second position 
wherein it is used to measure the reflective density of paper. Veit, 
however, does not provide for measuring the scanned density of the 
negative. Further, the time required to pivot the photocell of Veit limits 
the speed at which the printer can be operated. 
U.S. Pat. No. 3,462,221 to Tajima et al. shows a photographic printer 
wherein a first photocell is employed at a first location to measure the 
transmissive density of a negative, and a second photocell is employed at 
a second location to measure the reflective density of developed prints. 
Measurements made by these first and second photocells are used to control 
both the printing and developing processes. Tajima et al. suffers from the 
disadvantages inherent in maintaining and calibrating two separate 
photocells. Further, Tajima et al. does not provide for measuring the 
scanned transmissive density of a negative. 
It would thus be desirable to provide a photographic printer which, with 
the inclusion of as few additional components as possible, provides the 
capability to measure the scanned and large area transmissive density of 
negatives (or transmissive test patches), as well as the reflective 
density of prints (or reflective test patches). It would be further 
desirable if such a photographic printer were capable of operating at 
relatively higher speeds than hand-operated printers of the type shown in 
Veit above. 
OBJECTS OF THE INVENTION 
The principal object of the present invention is to provide a photographic 
printer capable of measuring the scanned and large area transmissive 
densities of negatives and the large area reflective densities of prints. 
A further object of the present invention is to provide a photographic 
printer capable of measuring both transmissive and reflective densities of 
negatives and prints, respectively, using a single light sensor. 
Another object of the present invention is to provide a photographic 
printer capable of measuring both transmissive and reflective densities of 
negatives and prints, respectively, which eliminates the need for 
expensive, external equipment. 
Yet another object of the present invention is to provide a method of 
operating a photographic printer to selectively measure scanned or large 
area transmissive characteristics of a negative or large area reflective 
characteristics of a print. 
SUMMARY OF THE INVENTION 
A new and improved photographic printer includes integral densitometry 
apparatus. The printer includes a single light sensor disposed integrally 
therewith. First densitometer means are provided disposed integrally with 
the printer for measuring the scanned transmissive density of the negative 
using the light sensor. Second densitometer means are provided integrally 
with the printer for measuring the large area transmissive density of the 
negative using the light sensor. Third densitometer means are provided, 
integral with the printer and responsive to the introduction of a 
reflective patch into the printer, for using the light sensor to measure 
the reflective density of the reflective patch. 
In a preferred embodiment of the invention, the light sensor is stationary, 
and a light source is provided for projecting light through the negative 
and selectively onto the light sensor. Further, in this preferred 
embodiment, the first, second and third densitometer means share a 
rotatable disc disposed between the negative and the light sensor. The 
rotatable disc supports scanning transmissive filters for use with the 
first densitometer means to measure the scanned density. The disc further 
supports large area transmissive filters for use with the second 
densitometer means (to measure the large area transmissive density of the 
negative) and the third densitometer means (to measure the reflective 
density of the reflective patch). 
Further in accordance with the present invention, a new and improved method 
is provided for operating a photographic printer to measure selected 
characteristics of a negative or a reflective test patch. The method is 
implemented in a printer including a single light sensor. The method 
comprises selectively measuring the scanned transmissive density of the 
negative using the light sensor. The light sensor is further used to 
selectively measure the large area transmissive density of the negative. 
Responsive to the introduction of a reflective patch into the printer, the 
light sensor is used to measure the reflective density of the reflective 
patch.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to FIG. 1, a color photographic printer 20 includes a light 
source 22 and photodiode 24, both situated on a common optical axis 26. 
Light source 22 is directed so as to project light along axis 26 towards 
photodiode 24. Light source 22 comprises, for example, a tungsten-halogen 
lamp 22A incorporating a "cold-mirror" reflector 22B, and also a heat 
absorbing glass plate 23. Photodiode 24 comprises, for example, a 
blue-enhanced silicon diode. An amplifier/converter unit 25 (described in 
detail below) is connected to the output of photodiode 24, the two forming 
a photometer 27. 
Adjacent light source 22 are three subtractive light filters, a Cyan filter 
28A, a Magenta filter 28B, and a Yellow filter 28C. A colored balance 
filter, in this embodiment of the invention a red-yellow balance filter 
28D, is disposed between Cyan filter 28A and light source 22. Each filter 
28A-28D is connected to a filter control mechanism 30, the filter control 
mechanism comprising a separate rotary solenoid connected to each filter. 
The rotary solenoids are indicated at 30A-30D in correspondence with the 
filters 28A-28D. Filter control mechanism 30 operates to selectively 
dispose filters 28A-28C into the light path along axis 26 to stop exposure 
of their respective colors. Filter control mechanism 30 further operates, 
in a manner described in further detail hereinbelow, to selectively 
dispose filter 28D out of the light path along axis 26 when scanning a 
negative, and into the light path when exposing/printing a negative. 
Adjacent filter 28C and centered on axis 26 is a light integrating box 
(LIB) 32. LIB 32 comprises, for example, a reflecting box 32A having a 
light-reflecting interior, including pyramid glass 32B at a first end 
proximate light source 22, and a diffuser 32C at the opposing second end. 
Situated adjacent LIB 32 between light source 22 and photodiode 24 is a 
film negative 34 to be printed. Negative 34 typically comprises one of a 
roll or disk of negatives, such as 135 or 110 type photographic negatives, 
and is supported in an appropriate holder and advance mechanism 35. As 
used herein, the term "negative" includes all transparent film images, 
including photographic transparencies. 
Situated between film negative 34 and photodiode 24, in a plane of focus 
perpendicular to and substantially centered on axis 26, is an optically 
transparent paper platen 36 comprised, for example, of an optically clear 
glass. A projection lens 38 and dark shutter 40 are disposed, 
respectively, between negative 34 and paper platen 36. Disposed adjacent 
platen 36, between the platen and photodiode 24, is a field lens 42. Field 
lens 42 preferably comprises a fresnel lens, chosen for its substantially 
flat, thin dimensions. Adjacent field lens 42, between the field lens and 
photodiode 24, is a reflection densitometry assembly 50 (described in 
detail below). Situated between reflection densitometry assembly 50 and 
photodiode 24 are, respectively, a relay lens 44, a rotating scanning disc 
46, and a condensing lens 48. A position sensing mechanism 51 is 
positioned adjacent the edge of scanning disc 46. 
Disposed proximate one end of platen 36 is a roll-paper dispensing 
mechanism 52 containing a roll 54 of unexposed photographic paper. 
Proximate an outlet 52A of roll-paper dispensing mechanism 52 is a cutting 
mechanism 56, such as a blade. In FIG. 1, printer 20 is shown with a 
portion 58 of unexposed photographic paper 54 dispensed from roll-paper 
dispensing mechanism 52 so as to overlay platen 36 with the 
light-sensitive side facing negative 34. 
It will be understood that the various lenses including projection lens 38, 
field lens 42, relay lens 44, and condensing lens 48 comprise lenses of 
standard design selected to provide appropriate focal lengths and f-stops 
(apertures). 
A digital computer 60 is provided for controlling printer 20 and for 
interacting with a human user (not shown) via a keyboard and display unit 
62. Computer 60 is connected to photometer 27 via amplifier/converter unit 
25. Computer 60 is further connected to filter controller 30, roll-paper 
dispensing mechanism 52, reflection densitometer apparatus 50, film holder 
and advance mechanism 35, dark shutter 40, position sensing mechanism 51, 
and a paper processor 64. 
Referring now to FIG. 2, scanning disc 46 comprises an improvement to what 
is typically referred to in the art as a Nipkow disc. In accordance with 
the known features of a Nipkow disc, scanning disc 46 includes three 
spirally disposed rows of scanning filters including a set of Red scanning 
filters 66, a set of Blue scanning filters 68, and a set of Green scanning 
filters 70. Each set of filters 66, 68, 70 includes ten small apertures 
72, each aperture being overlaid with an appropriately colored filter. 
Filters 66, 68, 70 each preferably comprises a broad-band filter so as to 
provide adequate light to photodiode 24 when measuring scanned densities 
as described in detail below. Further in accordance with the known 
features of a Nipkow disc, scanning disc 46 includes a plurality of timing 
marks 74 and a single starting mark 75 disposed about its periphery. In a 
manner described in detail below, timing marks 74 and starting mark 75 are 
used to determine the relative position of the various apertures on 
scanning disc 46 with respect to optical axis 26, and to communicate this 
information to computer 60 via position sensing mechanism 51. 
In accordance with the improvements of the present invention, scanning disc 
46 further includes Red, Green, and Blue large area transmissive (LAT) 
filter, indicated at 76, 78 and 80, respectively. Each LAT filter 76, 78, 
80 comprises an aperture relatively large than aperture 72 overlain by an 
appropriately colored filter. LAT filters 76, 78, 80 each preferably 
comprises a narrow-band filter for providing the desired precision when 
performing LATD measurements as will be described in detail below. LAT 
filters 76, 78 and 80 are positioned relative to timing marks 74 and 
position mark 75 so that their position relative to axis 26 can be 
determined by computer 60. 
Referring now to FIG. 2A, position sensing mechanism 51 comprises a pair of 
light-emitting diodes (LED's) 83, 85, situated on a first side of scanning 
disc 46 and positioned to project light through timing marks 74 and 
starting mark 75 of the scanning disc, respectively. Positioned on the 
opposite side of scanning disc 46 are a pair of photodiodes 87, 89. 
Photodiodes 87, 89 are located so as to oppose LED's 83, 85, respectively. 
Hence, photodiodes 87, 89 sense the position of scanning disc 46 by 
monitoring the rotation of timing marks 74 and starting mark 75, 
respectively. 
Referring now to FIG. 3, an exemplary embodiment of amplifier/converter 
unit 25 is shown for converting a current I.sub.pd output by photodiode 24 
to a digital output code D.sub.0-N for processing by computer 60. It will 
be understood that the exact structure of photometer 64 does not 
constitute a portion of the present invention, and thus the implementation 
of such circuits is not treated exhaustively herein. Amplifier/converter 
unit 25 includes a high gain current-to-voltage converter 130 connected to 
a temperature compensated, precision current source 132. The output of 
current source 132 is connected to a logarithmic amplifier (log amp) 134, 
the current source and log amp both being supplied with a reference 
voltage V.sub.ref1 by a reference voltage generator 136. The output of log 
amp 134 is connected to a 10-bit A/D converter 138, the A/D converter 
being supplied a reference voltage V.sub.ref2 by a second reference 
voltage generator 140. The 10-bit digital word output D.sub.0-N of A/D 
converter 138 is connected to computer 60. 
In operation, picoamp-level current I.sub.pd is converted to an amplified 
voltage V.sub.1, which is in turn converted to a nanoamp-level current 
I.sub.1 by current source 132. Current I.sub.1 is converted to an 
amplified log voltage V.sub.2 by log amp 134. Log voltage V.sub.2 is 
subsequently converted to a 10 bit digital word D.sub.0-N by A/D converter 
138, which is read and stored by computer 60 as described below. Reference 
voltage generators 136 and 138 are used to calibrate current source 132, 
log amp 134, and A/D converter 140. Photometer 27 exhibits an operating 
range of approximately three decades. 
In accordance with the present invention, printer 20 operates in three 
basic modes to provide the capabilities of: (1) measuring the LATD and/or 
scanned densities of negatives, and printing those negatives according to 
their measured transmission characteristics; (2) measuring the LATD of 
transmissive test patches; and (3) measuring the large area reflective 
density (LARD) of reflective test patches. All measurements and printing 
are performed on optical axis 26 using single photodiode 24. For purposes 
of explanation, these modes of operation will be described separately 
below. 
In the preferred embodiment of the invention, the first mode of operation 
described immediately above is performed using the scanned densities of 
the negatives, and will thus be referred to herein as the `scan and print` 
mode of operation. In the scan and print mode of operation, negative 34 is 
loaded into holder and advance mechanism 35. With no paper on platen 36, 
and with filters 28A, 28B, 28C, and 28D all removed from the light path 
along optical axis 26, light source 22 projects light along axis 26 
towards photodiode 24. This projected light, illustrated by dashed-line 
rays 84, is diffused by LIB 32 so as to impinge uniformly on negative 34. 
Dark shutter 40 is opened to pass light, and the light projected through 
negative 34 is focused by projection lens 38 onto glass platen 36. Because 
no paper is on platen 36, the light passes through the platen and is 
focused by field lens 42 onto relay lens 44. In this scan and print mode 
of operation, reflection densitometer apparatus 50 is transparent to this 
projected light. Scanning disc 46 is rotated by a motor (not shown). Relay 
lens 44 focuses the projected light through a medial region of scanning 
disc 46 towards condensing lens 48. Relay lens 44 and scan disc 46 are 
aligned such that all of the filters on the scan disc pass through the 
light output of the relay lens. As scan disc 46 rotates, each of scanning 
filters 66, 68, 70 will scan substantially the entirety of the projection 
of negative 34, while large area transmission filters 76, 78, 80 each will 
intercept substantially the entirety of the projection. The portions of 
the light filtered by the various filters on scanning disc 46 are 
subsequently focused by condensing lens 48 onto photodiode 24. 
As a first step in the process of scanning and printing negative 34, 
computer 60 controls the scanning of the negative by R, G, and B scanning 
filters 66, 68 and 70, respectively, on scanning disc 46. This scanning is 
performed by storing the output of photometer 27 in computer 60 as the 
various apertures 72 in the scanning filters 66, 68, 70 pass preselected 
regions of the light projected through negative 34. Computer 60 controls 
the scanning by monitoring the position of timing marks 74 and starting 
mark 75 using position sensing mechanism 51. The location of the various 
filters on scanning disc 46 being known relative to timing marks 74 and 
starting mark 75, computer 60 uses this information to calculate when a 
selected window 72 of a scanning filter 66, 68, 70 is aligned with a 
selected region of negative 34. Computer 60 then stores the output of 
photometer 27 at the calculated time. It will be appreciated that in this 
manner substantially the entirety of negative 34 can be scanned in as many 
discrete units as is desired, the only limitation being the physical 
limitations of the equipment. The scanned transmissive densities of 
negative 34 thus obtained are stored in a memory (not shown) of computer 
60 for subsequent use in determining exposure times for the negative. 
At this point in the process of printing negative 34, computer 60 has 
scanned and stored the transmissive density of the negative at a plurality 
of locations. For example, and without limitation, it may be desired to 
utilize scanning disc 46 in the manner described above to scan 80 discrete 
units of negative 34 to determine the R, G, and B density of each of these 
units. Using these scanned transmissive density measurements, computer 60 
now calculates an appropriate exposure time for printing negative 34 onto 
the portion 58 of unexposed photograhic paper 54 which will be advanced to 
overlay platen 36 in the manner described below. It will be understood 
that one of many known algorithms can be utilized to calculate the 
printing exposure time. Such algorithms can include, for example, the use 
of a printing density conversion matrix in computer 60 as a first step in 
calculating exposure times in a manner well known to those skilled in the 
art. The selection of an appropriate algorithm is not a part of the 
present invention, and will not be discussed in detail herein. 
Subsequent to the conclusion of the scanning step, and after the initiation 
of the exposure calculations, dark shutter 40 is closed. The light 
projected by light source 22 is stopped by dark shutter 40, and roll-paper 
dispensing mechanism 52 is actuated by computer 60 to unroll unexposed 
paper portion 58 onto platen 36. 
Wth the light-sensitive side of paper portion 58 directed at negative 34, 
solenoid 30D of filter control mechanism 30 is used to position red-yellow 
balancing filter 28D on axis 26, and then dark shutter 40 is opened to 
pass light. Cyan, magenta, and yellow filters 28A, 28B, 28C, are 
manipulated by corresponding solenoids 30A-30C of controller 30 to expose 
negative 34 onto paper portion 58 in accordance with the results of the 
exposure algorithm calculation done by computer 60. Upon proper exposure 
of paper portion 58, dark shutter 40 is closed. Cutting mechanism 56 is 
then activated to separate now exposed paper portion 58 from roll 54, and 
the paper portion is subsequently removed for development by paper 
processor 64 (the details of which are not shown herein). Filters 28A-28D 
are reset off of optical axis 26 out of the light path. The scan and print 
process described above is then repeated for subsequent negatives 34. 
In the second mode of operation described above, i.e. measuring the LATD of 
negative 34 (or a transmissive test patch substituted therefore) the 
negative is placed in holder and advance mechanism 35, and paper portion 
58 is removed from (or not advanced onto) platen 36. Computer 60 then 
reads and stores the output of photometer 27 as LAT filters 76, 78 and 80 
are respectively disposed in the light path along axis 26. In a manner 
similar to the scanning operation described above, computer 60 controls 
these measurements by monitoring timing marks 74 and starting mark 75 via 
position sensing mechanism 51. The measured R, G and B LATD's of negative 
34 are stored in the memory of computer 60. 
It is to be understood that, in the preferred embodiment of the invention, 
LATD's are only used to measure the transmissive density of transmissive 
test patches, for example to control a film processor (not shown). Scanned 
transmissive densities are used, in the manner described above, to 
calculate exposure times for pictorial negatives. However, LATD's can be 
used to calculate the exposure times for pictorial negatives. Similarly, 
some combination of LATD's and scanned densities can be also used to 
calculate the exposure times for pictorial negatives, the densities used 
being dependent on the types of negatives being printed and the exposure 
calculation algorithm implemented in computer 60. The scope of the present 
invention is thus intended to cover all of these density 
measurement/exposure calculation combinations. 
Referring now to FIGS. 4 and 5, a portion of printer 20 is shown including 
details of reflection densitometer apparatus 50. Apparatus 50 includes a 
removable carrier 90 (best shown in FIG. 5) for supporting a paper strip 
92. Carrier 90 comprises two generally rectangular halves 90A, 90B hinged 
along a lower, length-wise edge by hinges 94 so that they can be opened to 
accept strip 92. Four rectangular apertures 96A, 96B, 96C, and 96D are 
disposed in side 90B of carrier 90, these apertures being generally 
rectangular in shape and in vertical alignment within the carrier side. 
For purposes of explanation, paper strip 92 will be described herein as a 
paper process control strip including four developed, reflective patches 
98A, 98B, 98C, and 98D. Patches 98A-98D vary in density from white patch 
98D to black patch 98A, each of the patches having a known exposure. 
Patches 98A-D are located on test strip 92 so as to be in respective 
alignment with apertures 96A-D of carrier 90. Carrier 90 further includes 
a white calibration patch 100 of constant density, disposed permanently on 
the outer surface of side 90B thereof in vertical alignment with apertures 
96A-D. Five V-shaped detents are provided along the unhinged, lengthwise 
edge of carrier 90, these detents being indicated at 102A, 102B, 102C, 
102D, and 102E. Detents 102A-102D are in vertical alignment with apertures 
96A-D, respectively. Detent 102E is in vertical alignment with calibration 
patch 100. An upper corner 103 of carrier 90 is chamfered to engage a 
roller in a manner described in detail below. 
Referring back to FIG. 4, it is seen that carrier 90 is supported in 
printer 10 so as to be disposed in a plane perpendicular to axis 26. 
Carrier apertures 96A-D, and hence strip patches 98A-D and calibration 
patch 100, face photodiode 24. A generally U-shaped bracket 104, including 
a pair of legs 104A, 104B connected by a common base 104C, is disposed 
between carrier 90 and photodiode 24. Bracket 104 is disposed 
symmetrically about axis 26, with legs 104A and 104B disposed on opposite 
sides of the axis and projecting towards carrier 90. Each leg 104A and 
104B supports a lamp 106 in a reflective tube 108. Optionally included in 
each reflective tube 108 is a heat absorbing glass 109 including 
infrared-rejecting interference filters. Each reflective tube 108 
functions as an integrating box to direct the light output of the lamp. 
Each lamp 106 and tube 108 are directed to project light, indicated by 
rays 110, at the aperture of carrier 90 centered on axis 26; i.e. aperture 
96C as shown in FIG. 4. 
Continuing to describe apparatus 50 as shown in FIG. 4, a movable 
supplementary lens 112 is shown situated in base 104C of bracket 104. A 
lens control mechanism 114, details of which are described below with 
respect to FIG. 6, is connected to lens 112 and further connected so as to 
sense the presence of carrier 90 in printer 20. A position sensing 
mechanism 116, the details of which are also described with respect to 
FIG. 6 below, is disposed so as to sense detents 102A-E of carrier 90 as 
the carrier is inserted into printer 20. 
Referring now to FIG. 6, printer 20 includes a slot 118 for accepting 
carrier 90 and supporting the carrier in the plane perpendicular to axis 
26. Position sensing mechanism 116 is seen to comprise a spring portion 
120 shaped and positioned to engage each respective detent 102A-E, one at 
a time, as carrier 90 is inserted into printer 20. Spring portion 120 is 
connected to a pressure sensitive switch 122 which electronically senses 
the movement of the spring portion through detents 102A-E and transmits 
this information to computer 60. 
Lens control mechanism 114 includes a holder 124 for lens 112, the holder 
being connected to a roller 126 via a pivoting member 128. A spring 130 
normally biases pivoting member 128 in a counter-clockwise direction about 
a pivot point 131. With member 128 thus biased, holder 124 is normally 
biased towards the top (as viewed in FIG. 6) of bracket base 104C such 
that lens 112 is removed from the optical path along axis 26. When carrier 
90 is inserted into slot 118, roller 126 engages chamfered corner 103 of 
the carrier, and pivoting member 128 pivots, thereby sliding lens 112 into 
a centered position in the optical path along axis 26. In FIG. 6, 
reflection densitometry apparatus 50 is shown in solid line with carrier 
90 inserted in printer 20 such that patch 100 and lens 112 are both 
centered on optical axis 26. Further shown, in dashed-line, is the 
engagement of roller 126 with chamfered corner 103 of carrier 90. 
As described above, in the scan-and-print and LATD measurement modes of 
operation, carrier 90 is removed from printer 20, lens 112 is 
automatically removed from the optical path along axis 26, lamps 106 are 
off, and reflection densitometry apparatus 50 is effectively transparent 
to the printer. When it is desired to measure the large area reflective 
density of patches 96A-D of paper strip 92, the paper strip is inserted in 
carrier 90, and the carrier is inserted in slot 118 of printer 20. 
Position sensing mechanism 116 senses the insertion of carrier 90 into 
printer 20 and signals computer 60. Under the control of computer 60, 
lamps 106 are switched on. Roller 126 engages carrier 90 and pivoting 
member 128 pivots to position lens 112 on axis 26. 
As position sensor 116 senses each respective detent 102A-E, computer 60 
controls the measurement of the large area reflective density of the 
corresponding paper strip patch 96A-D or the calibration patch 100 aligned 
along axis 26. For purposes of explanation, the operation of printer 20 in 
the large area reflection densitometry mode of operation will now be 
described with respect to FIG. 4, wherein detent 102C is aligned with axis 
26 and paper strip patch 96C is centered about the axis. Light rays 110 
projected by lamps 106 are directed by reflective tubes 108 through 
aperture 96C onto paper strip patch 98C, and reflected therefrom into lens 
112. Supplementary lens 112 forms a virtual image of paper strip patch 96C 
in the plane of fresnel lens 42 for relay lens 44, which in turn focuses 
this image onto rotating scanning disc 46 in the manner described above. 
The apertures in disc 46 for the filters 76, 78, 80 act as optical field 
stops to reduce stray light from reaching photodiode 24 so that only light 
reflected from patch 92C is measured. The light projected through filters 
76, 78, 80 on scanning disc 46 is focused by condensing lens 48 onto 
photodiode 24. Computer 60 then measures the light detected by photodiode 
24 when LAT filters 76, 78, and 80 (FIG. 2) are aligned, respectively, on 
axis 26. It will thus be appreciated that LAT filters 76, 78, 80 are used 
to measure the LATD of negative 34 (as described above), or the large area 
reflective density of the reflective test patches 96A-D on paper strip 92. 
The timing of this process is controlled by computer 60, using position 
sensing mechanism 51 in the manner described above. 
Thus, as carrier 90 is inserted into printer 20 (from left to right as 
viewed in FIG. 6), reflection densitometry apparatus 50 of the printer is 
used to measure the large area reflective density of white calibration 
patch 100, and paper strip patches 96D, 96C, 96B, and 96A, in that order. 
When the large area reflective densitometry measurements are complete, 
carrier 90 is removed from printer 20, and, under the control of computer 
60, reflection densitometry apparatus 50 becomes essentially invisible to 
the printer. If, for example, paper strip 92 comprises a paper process 
control strip, the large area reflective densities measured during the 
above-described refelection densitometry mode of operation would then be 
compared to previously measured large area reflection reference densities 
and limits stored in computer 60. The invention is not thus limited, 
however, and the reflection densitometry capability provided by printer 20 
can be used, for example, to measure the LATD of printer control test 
prints, or to make any other appropriate reflection densitometry 
measurements. 
FIGS. 7 and 8 show an alternate embodiment of position sensing mechanism 
116' wherein a pair of LED's 134, 136 and opposing photosensors 138, 140, 
respectively, are used to sense position holes 142 in carrier 90'. LED's 
134, 136, and photosensors 138, 140, are fixed on printer 20 on opposite 
sides of slot 118 (FIG. 6) A separate position hole 142 is positioned on 
carrier 90' in fixed relation to patch 100 and each aperture 96A-96D. 
Detents 102A-102E are still used to position carrier 90' in printer 20. 
However, computer 60 senses the position of carrier 90' by monitoring 
photosensors 138, 140. Specifically, when carrier 90' is inserted into 
printer 20, the carrier will block the light path between LED 136 and 
photosensor 140, turning the photosensor off. As carrier 90' is advanced 
into printer 20, LED 134 and photosensor 138 will together sense each hole 
142 as patch 100 and apertures 96A-96E are positioned, sequentially, to 
perform large area reflection densitometry measurements in the manner 
described above. 
In summary, there is thus provided a color photographic printer which 
provides the capability to measure the scanned and large area transmissive 
densities of negatives (or transmissive test patches), and the large area 
reflective density of reflective patches, without the use of any 
significant external equipment. The printer requires a minimum of 
additional equipment relative to that equipment required to make prints. 
More specifically, while providing the capabilities described herein, the 
printer utilizes a single light sensor, a single scanning disc, a single 
computer, and additionally shares much of the optical and mechanical 
hardware otherwise necessary to just print negatives onto paper. In the 
scan-and-print mode of operation, the printer is capable of automatically 
scanning and printing negatives, without user intervention, at relatively 
high rates of speed. 
While a preferred embodiment of the invention has been illustrated and 
described, it will be clear that the invention is not so limited. Numerous 
modifications, changes, variations, substitutions and equivalents will 
occur to those skilled in the art without departing from the spirit and 
scope of the present invention. Accordingly, it is intended that the 
invention herein be limited only by the scope of the appended claims.