Hard copy simulator with stored data to correct for lighting conditions

A simulator simulates a hard copy to be made and displays an image thereof on a color monitor. In such a simulation, a lighting condition correction unit corrects a video signal in accordance with the lighting conditions where the color monitor is installed. The color balance and density of the simulated image under an illumination thus are the same as the hard copy to be made.

BACKGROUND OF THE INVENTION 
The present invention relates to a hard copy simulator, and, more 
particularly, to a hard copy simulator for displaying an image simulating 
a finished hard copy, the simulator taking into account the illumination 
state in working environments. 
A hard copy apparatus containing a built-in simulator, such as a 
photographic printer, ink jet printer, laser printer, and the like is 
well-known in the art. With such a hard copy apparatus, an image 
simulating the finished hard copy is displayed on a color monitor to check 
the hard copy quality prior to producing a hard copy of the image. If the 
finished hard copy quality is anticipated to be unsatisfactory, it may be 
corrected by a keyboard. 
Generally, a color monitor for inspecting installed finished hard copy 
quality, situated in a bright working room, is used for improving work 
efficiency. However, if the lighting conditions within a working room are 
different (e.g., in color temperature) from the standard inspection light 
source, a simulated hard copy image on a color monitor hard copy will be 
different from an actual finished hard copy, resulting in improper 
inspections. 
Therefore, it is a principal object of the present invention to provide a 
hard copy simulator capable of displaying an image simulating the hard 
copy corrected according to the work environment illumination state. 
It is another object of the present invention to provide a hard copy 
simulator allowing correct inspection of finished hard copy quality. 
SUMMARY OF THE INVENTION 
In order to achieve the above objects of the present invention, the 
capability is provided for correcting a simulated image displayed on a 
color monitor, according to lighting conditions in a work area where the 
color monitor is installed. Preferably, the correction capability uses a 
table look-up memory containing data, more preferably, for respective 
types of illumination light sources, so that table data can be selectively 
used so as to obtain a hard copy identical to the simulating image. 
According to the present invention, the finished hard copy quality can be 
inspected by monitoring a simulated image which is not substantially 
affected by lighting conditions since a simulated image is corrected 
according to the lighting conditions in the work area where a color 
monitor is installed. Consequently, even in a work environment using an 
artificial light source, a correct inspection can be performed resulting 
in a hard copy being formed having proper color balance.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a video printer embodying the present invention in which an 
image input device 10 is constructed of, for example, a video tape 
reproducing unit, a color video camera, or the like. The image input 
device 10 is supplied with red (R). green (G), and blue (B) color video 
signals of a positive image of an object or a photographic print. These 
color video signals are supplied to analog/digital (A/D) converters 11 
provided, respectively, for different color video signals, and are 
converted into digital signals. The digital signals are inputted to a 
logarithmic conversion look-up table memory (LUT) 14 to be converted 
logarithmically into density (strictly speaking, logarithmic conversion 
value) signals. 
FIG. 2 shows an example of the characteristics of table data stored in LUT 
14. If the image input device 10 has inputted a negative image, such as 
that of a color negative film, the table data shown in FIG. 2 are used by 
reversing the data, and the negative-to-positive conversion is performed 
simultaneously with the logarithmic conversion. 
The density signals outputted from LUT 14 are sent to a matrix calculation 
circuit 15 for color correction by a known matrix (three rows and three 
columns) formula. With this color correction, the difference between the 
spectral characteristics of a color paper and the spectral sensitivity of 
a color television is corrected. The density signals color-corrected by 
the matrix calculation circuit 15 are written in a frame memory 16 
provided for the respective colors. 
The density signals outputted from LUT 14 also are sent to an automatic 
exposure calculation circuit 17 in which the exposure amount is calculated 
based on, for example, an average transmittance density (LATD) value, 
maximum and minimum values, or the like. The calculated exposure amount is 
sent to a controller 13. Depending upon the exposure amount, reference 
table data stored in density/color balance correction LUTs 19 and 35 in 
the CRT exposure system and in the simulator system, respectively, are 
shifted, and again are written in LUTs 19 and 35 under the control of the 
controller 13. 
The density signals written in the frame memory 16 are read in response to 
a read signal sent from the controller 13, and are sent to the CRT 
exposure system and to the simulator system. In the CRT exposure system, 
the density or color balance of each print frame is corrected using the 
density/color balance correction LUT 19 provided for the respective 
colors. Such density/color balance correction is performed so that the 
correction amount is determined empirically while monitoring a simulated 
image on a monitor CRT 34. The determined correction amount is inputted 
via color correction keys 18a, 18b, and 18c, or density correction key 
18d. Then, reference table data stored in a memory 12 are shifted by the 
correction amount, or multiplied by a correction coefficient, to obtain 
correction table data which are written in LUT 19. FIG. 3 shows an example 
of the correction table data set. 
The density signals corrected by the density/color balance LUT 19 undergo 
data conversion by an exposure LUT 20. FIG. 4 shows an example of this 
table data, which are determined while considering the light emission 
characteristics of an exposure CRT 23 and the color characteristics of a 
color paper 25. The density signals subjected to data conversion by the 
exposure LUT 20 are further subjected to positive/negative conversion. 
Thereafter, the density signals are converted into analog signals by a D/A 
converter 21, and then are sent to a CRT driver 22. The CRT driver 22 
drives the monochrome exposure CRT 23 under the control of the controller 
13 upon pressing a print key on a keyboard 18. 
An image displayed on the exposure CRT 23 is focussed via a printing lens 
24 onto the color photographic paper 25 set on an exposure stage while a 
shutter 28 is opened by a shutter driver 26. In order to change a 
monochrome image displayed on the exposure CRT 23 to a red, green, or blue 
image, a red filter 29, green filter 30, and blue filter 31 are provided, 
respectively, one of which is selected by a filter switching unit 27 and 
inserted into a printing optical path. 
In the simulator system, the density signals written in the frame memory 16 
are read under the control of the controller 13, and are sent to a matrix 
calculation circuit 33 provided for respective colors for correction of 
the color monitor characteristics. The matrix calculation circuit 33 
performs color correction, thereby enabling the light emission 
characteristics of the color monitor CRT 34 to match the color 
characteristics of the color paper 25. 
The density signals corrected by the matrix calculation circuit 33 are sent 
to the density/color balance correction LUT 35 provided for respective 
colors for correction of density/color balance, according to the 
determined correction data. This correction performed in the simulator 
system corresponds to the correction performed by the density/color 
balance correction LUT 19 in the CRT exposure system. 
The corrected density signals are sent to an environment correction LUT 36 
for correction according to the lighting conditions of the work area where 
the monitor CRT 34 is installed. This correction is performed allowing a 
reference image to be printed for test purposes. Then, the color tone of 
the test print photograph is compared with that of the displayed image on 
the monitor CRT 34 to determine empirically the correction amount which is 
then inputted via the keyboard 18. This actuates the keyboard 18 to enter 
an environment correction mode, and the correction amount is inputted with 
the correction keys 18a through 18d. The controller 13 causes the 
reference table data to shift according to the inputted correction amount 
so that the work area's lighting conditions are matched, and also causes 
the shifted table data to be written in the environment correction LUT 36. 
FIG. 5 shows an example of the table data written in the environment 
correction LUT 36. The table data are those data selected from the table 
data shown in FIG. 3 according to the correction amount. 
The image signal corrected by the environment correction LUT 36 is 
subjected to data conversion by using the table data in a display LUT 37 
so that a simulated image having the same gradation as the finished print 
can be displayed on the monitor CRT 34. The table data are determined in 
accordance with the measured data under the standard environment 
condition. FIG. 6 shows an example of this table data. The table data in 
LUT 37 are determined such that the brightness/chromaticity of a test 
pattern image having stepwise gradations at the respective areas, and 
displayed on the monitor CRT 34, is the same as for the finished print. 
The brightness/chromaticity is measured with a spectral luminance meter 
and a density meter. Thus, a grey spot on the print can be displayed on 
the monitor CRT 34 as a spot having a chromaticity of a standard white 
light source. 
White color on the monitor CRT 34 being sensed by a person is affected by 
the conditions within the field of view outside of the monitor CRT 34 
screen. Therefore, even a spot having a chromaticity of a standard white 
light source and displayed on the monitor CRT 34 is not sensed as white, 
if, for example, the work area lighting condition's color temperature is 
low. Rather, the spot is sensed as being somewhat cyan. In this case, 
correcting the display chromaticity of the spot to become somewhat red is 
required so that a proper inspection results for a simulated image 
displayed on the monitor CRT 34. The environment correction LUT 36 makes 
such a correction possible. 
The image signal corrected by the display LUT 37 is converted into an 
analog signal by a digital/analog (D/A) converter 38, and thereafter, sent 
to a CRT driver 39. The CRT driver 39 drives the monitor CRT 34 which 
displays a color image simulating a finished print photograph. 
The controller 13 includes a microcomputer, and updates the table data in 
LUTs 14, 19, 20, 35, 36, and 37, correction coefficients, and the like of 
the formulas used by the matrix calculation circuits 15 and 33, according 
to the correction amount inputted by the keyboard 18. The controller 13 
also controls the shutter driver 26 and filter switching unit 27. 
The embodiment described above is operated by turning on the apparatus. The 
controller 13 thereby initializes the data in the frame memory 16, matrix 
calculation circuits 15 and 33. LUTs 14, 20, 35, 36, and 37 according to 
the memory 12 contents, and actuates associated circuitries. The type of 
color photographic paper 25 to be used by the video printer is inputted to 
the controller 13 by a paper type input key of the keyboard 18, and the 
controller 13 writes the coefficient data of the matrices used by the 
matrix operation circuit 15 according to the paper type information. 
The video printer corrects the image according to the work area lighting 
conditions such that the monitor CRT 34 of the simulator system displays 
an image with the same characteristics as the print photograph. Reference 
data are set at LUTs and the like, and a reference video image is printed 
on a color photographic paper 25. The reference data then are shifted 
according to the work area lighting conditions so that the image displayed 
has the same color tone as the test print image. The shifted data are 
written in the environment correction LUT 36. 
After writing data in the environment correction LUT 36, an inspection mode 
is entered by pressing an inspection key. The image data inputted by the 
image input device 10 are processed by LUTs 14, 35, 36 and 37, matrix 
calculation circuits 15 and 33, and the like. The color balance/density is 
corrected according to the exposure amount calculated by the automatic 
exposure amount calculation circuit 17. A color image simulating a print 
photograph is displayed on the monitor CRT 34. The operator inspects the 
density/color balance while monitoring the color image displayed on the 
monitor CRT. The density/color balance is corrected, if necessary, by the 
correction keys 18a through 18d. Upon correction, the correction table 
data in the density/color balance correction LUTs 20 and 33, of the CRT 
exposure system and simulator system, respectively, are converted into the 
table data by shifting the reference table data by the correction amount. 
Thus, a color image, simulating a finished print photograph after manual 
correction, is displayed on the monitor CRT 34. If the manual correction 
still is not sufficient, the correction keys 18a through 18d are actuated 
again for another correction cycle. 
If the finished simulated image is deemed proper, a print key is depressed 
to start printing and perform exposure of one frame of the color 
photographic paper 25. That is, the image signals for respective colors 
sequentially read out from the frame memory 16 are corrected by the 
density/color balance correction LUT 19, and the CRT driver 22 drives the 
monochrome exposure CRT 23 according to the corrected image signals. The 
red, green, and blue components of the negative image are displayed 
sequentially in black-and-white on the exposure CRT 23. While a 
black-and-white monochromatic color image is displayed on CRT 23, a 
corresponding color filter 29, 30, or 31, is inserted into the optical 
printing path to convert the image into a red, green, or blue image, 
respectively, thus performing an additive three color plane sequential 
exposure. 
In the above embodiment, a simulator is built into the video printer. The 
present invention is not limited thereto, but a simulator may be mounted 
on a photographic printer for printing a photographic paper 51, as shown 
in FIG. 7, in the second embodiment of the invention. The simulator system 
is substantially the same as in the first embodiment except for the 
removal of the CRT exposure system. Like circuits have been represented by 
using identical reference numerals, with the description therefor being 
omitted. 
A negative image of the negative film 50 is picked up, for example, by a 
color television camera 1Oa. Three color image signals are obtained and 
are written in a frame memory 16 via an A/D converter 11 for each 
separated color. The image signals from the frame memory 16 undergo 
logarithmic conversion and negative/positive conversion by LUT 14 
simultaneously, and are sent to an automatic exposure amount calculation 
circuit 17. According to each color exposure amount calculated by the 
automatic exposure amount calculation circuit 17, a controller 13 rewrites 
the table data in a density/color balance LUT 35, and controls a filter 
driver 58 and an exposure time for each color. The density signals from 
LUT 14 are color-corrected by a matrix calculation circuit 15a provided 
for the respective colors. This color-correction eliminates the difference 
between the spectral sensitivity of the color television camera 10c and 
the light emission characteristics of the monitor CRT 34. 
If necessary, the density signals corrected by the matrix calculation 
circuit 15a have each print frame corrected by density/color balance 
manner similar to the first embodiment, by a density/color balance 
correction LUT 35 provided for respective colors. Thereafter, the density 
signals are sent to an environment correction LUT 36 where they are 
corrected according to the lighting conditions of the work area where the 
monitor CRT 34 is installed. 
The density signals corrected by the environment correction LUT 36 are 
corrected further by a display LUT 37. Thereafter, the corrected density 
signals are converted into analog signals by a D/A converter 38, and are 
sent to a CRT driver 39. The CRT driver 39 drives the monitor CRT 34 which 
thereby displays a color image simulating a finished print photograph on 
its screen. 
The photographic image exposure system is described below. White light 
projected from a white light source 52 passes through a mixing box 53 and 
film carrier 54, and reaches a negative film 50 set at the printing stage 
to illuminate the film from the underside thereof. The mixing box 53 is 
constructed of a rectangular tube with its inner surface formed with a 
mirror plane, and diffusion plates mounted on opposite openings. The 
negative film 50 is placed on the film carrier 54 and is pushed downward 
with a mask 54A. 
Above the film carrier 54, a zoom lens 55 is provided for focussing the 
negative image of the negative film 50 onto the color photographic paper 
51 set on the exposure stage while a shutter 56 is opened. The shutter 56 
is controlled by shutter driver 57 such that it opens for a time 
corresponding to the sensitivity of the color photographic paper 51 and 
the condition of the negative image. 
A cyan filter 59, magenta filter 60, and yellow filter 61 for a subtractive 
color print are disposed between the shutter 56 and zoom lens 55. A filter 
driver 58 is controlled by the controller 13 so that, for example, after 
the lapse of exposure time for a red color, the cyan filter 59 of the 
complementary color is inserted into the optical printing path to thus 
terminate red color exposure. 
The second embodiment operates by image data being sent from the television 
camera 10a to the A/D converter 11 where they are converted into digital 
signals and written in the frame memory 16. The image signals written in 
the frame memory 16 are converted into density signals by LUT 14, and, 
thereafter, are color-corrected by the matrix calculation circuit 15c. The 
color-corrected image data also are corrected by density/color balance for 
each print frame by the density/color balance correction LUT 35. Next, the 
image data are corrected by the environment correction LUT 36 according to 
the work area lighting conditions, and, thereafter, undergo gradation 
correction by the display LUT 37. The corrected image signals are 
converted into analog signals at the D/A converter 38, and sent to the CRT 
driver 39 which drives CRT 34 according to the image data to thereby 
display a color image having the same color balance/density as the print 
photograph. 
As described above, the operator inspects a finished print condition while 
monitoring the simulated image displayed on the color monitor CRT 34, and, 
if necessary, performs density/color balance correction. Since the 
simulated image has been corrected according to the work area lighting 
conditions, an image having the same color tone as the print photograph 
can be monitored so that precise inspections result even if an artificial 
light source is used in the work environment. 
After inspecting a finished print condition, the operator depresses a print 
key to start printing. According to the exposure amount for each color 
calculated by the automatic exposure amount calculation circuit 17, or 
according to the corrected exposure amount, the controller 13 controls the 
timing of when each color filter 59, 60, or 61 is to be inserted into the 
optical path, so that each color's exposure time is adjusted. This 
guarantees a print photograph having a proper color balance and density. 
Thus, in the second embodiment, exposure time has been controlled. However, 
each color's filter insertion amount may be controlled for the exposure 
control. 
In the above embodiments, the color balance correction LUT 35, environment 
correction LUT 36, and display LUT 37 of the simulator system have been 
provided separately. However, the present invention is not limited 
thereto, and a single LUT may be used for all three types of corrections. 
Furthermore, the invention has been described using a configuration of a 
video printer and photographic printing apparatus as an example. The 
present invention is also applicable to other hard copy apparatuses such 
as ink jet printers, laser printers, and the like. Furthermore, the 
present invention may be embodied as a unit type simulator capable of 
being configured with another discrete printer. Additionally, different 
types of monitors may be used, including color liquid crystal displays as 
well as color CRT displays. 
While certain preferred embodiments have been shown and described, many 
changes and modifications within the spirit of the invention will be 
apparent to those of working skill in this technical field. Thus, the 
scope of the invention should be considered as limited only by the 
appended claims.