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Claims  |
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What is claimed is:
1. A method of setting color copying conditions of a color copying machine,
said color copying machine being provided with scanning means for scanning
an original with illuminating light; three light measuring means, one
individual to each of three primary colors; and three adjustable color
filters for regulating respective components of light, said method
comprising the steps of:
scanning a test chart having density patterns for said three primary colors
to detect three primary color components of light reflected from said test
chart using said three light measuring means, so as to obtain three
primary color exposures based on said three primary color components;
scanning said test chart to make a color copy thereof;
scanning said color copy to detect three primary color components of light
reflected from said color copy using said three light measuring means, so
as to detect reflected amounts of light for said three primary colors;
logarithmically transforming said reflected amounts of light into color
densities for said three primary colors;
providing relationships between said three primary color densities and said
three primary color exposures for said three primary colors; and
adjusting said three color filters so as to make said relationships
coincide with predetermined relationships between color densities and
exposures for said three primary colors, respectively.
2. A method as defined in claim 1, wherein said three primary colors are
cyan, magenta and yellow.
3. A method as defined in claim 2, wherein said three light measuring means
are photoconversion elements for sensing blue, green and red light,
respectively.
4. A method as defined in claim 1, wherein said color filters are cyan,
magenta and yellow filters.
5. A method as defined in claim 1, wherein said color filters are adjusted
based on relationships between opening positions of said color filters in
said copying light path and light amounts passed through said color
filters at said positions, respectively.
6. A method of setting color copying conditions of a color copying machine,
said copying machine being provided with scanning means for scanning an
original to be copied placed on a copy table with illuminating light;
cyan, magenta and yellow filters disposed in a copying light path between
said copying table and a recording material; and three light measuring
means, one individual to each of three primary colors, said method
comprising the steps of:
scanning a plate having a constant density with said illuminating light to
detect three primary color components of light reflected from said plate
through said filters using said three light measuring means, respectively,
said filters being placed in turn in said copying light path and changed
in position stepwise; so as to obtain three primary color exposures;
scanning said plate again with said illuminating light to make a color copy
of said plate through said filters placed in turn in said copying light
path;
scanning said color copy to detect three color components of light
reflected from said color copy using said three primary light measuring
means, so as to detect amounts of light reflected from said color copy for
said three primary colors;
logarithmically transforming said reflected amounts of light into color
densities of said color copy of said three primary colors;
providing relationships between said color densities and said three primary
color exposures for said three primary colors; and
adjusting said filters so as to make said relationships coincide with
predetermined relationships between densities and exposures for said three
primary colors.
7. A method as defined in claim 6, wherein said three light measuring means
are photoconversion elements for blue, green and red light.
8. A method as defined in claim 6, wherein said filters are adjusted based
on relationships between opening positions of cyan, magenta and yellow
filters in said copying light path and light amounts passed through said
cyan, magenta and yellow filters at said positions, respectively.
9. A method as defined in claim 7, wherein said plate is a cover having a
white reflection surface for covering said original.
10. A method of setting color copying conditions of a color copying
machine, said color copying machine being provided with scanning means for
scanning an original placed on a copying table with illuminating light and
three light measuring means, one individual to each of three primary
colors, said method comprising the steps of:
scanning a test chart having density patterns for said three primary colors
to detect three primary color components of light reflected from said test
chart using said three light measuring means, so as to detect three
primary color exposures based on said three primary primary color
components;
scanning said test chart again to make a color copy thereof;
scanning said color copy to detect three primary color components of the
light reflected from said color copy using said three light measuring
means, so as to detect light quantities for said three primary colors;
logarithmically transforming said light quantities into color densities for
said three primary colors;
providing relationships between said three primary color densities and said
three primary color exposures for said three primary colors; and
controlling exposures for said three primary colors based on said
relationships, respectively.
11. A method as defined in claim 10, wherein said three primary colors are
cyan, magenta and yellow.
12. A method as defined in claim 11, wherein said three light measuring
means are photoconversion elements for blue, green and red light.
13. A method as defined in claim 10, prior to performing said step of
controlling exposures further comprising the steps of:
detecting exposures as desired values corresponding to white level copy
densities, based on said relationships for said three primary colors; and
measuring a reflection plate having said white level copy densities to
detect light reflected from said reflection plate for said three primary
colors; and
wherein said controlling exposure step further comprises the step of
adjusting cyan, magenta and yellow filters located in a copying light path
so that said white level copy densities coincide with said light reflected
from said reflection plate for said three primary colors to thereby
control said three primary color exposures.
14. A method as defined in claim 10, prior to performing said step of
controlling exposures further comprising the steps of:
detecting exposures as desired values for said three primary colors
corresponding to white level copy densities, based on said relationships
for said three primary colors; and
wherein said controlling exposure step further comprises the step of
adjusting cyan, magenta and yellow filters located in a copying light path
based on relationships between opening positions of said color filters and
light amounts passed through said color filters at said positions for each
filter to thereby control said three primary color exposures.
15. A method of setting a color copying machine to various copying
conditions, said copying machine being provided with a scanning means for
scanning an original to be copied with illuminating light; cyan, magenta
and yellow filters disposed in a copying light path between said original
and a recording material; and three light measuring means, one individual
to each of three primary colors; said method comprising the steps of:
scanning a plate having a uniform density to detect three primary color
components of light reflected from said plate through said cyan, magenta
and yellow filters disposed in turn in said optical path and stepwise
changed in position, using said three light measuring means, respectively,
so as to obtain three color exposures for said three primary colors;
scanning said plate again with said illuminating light so as to make a
color copy of said plate through said filters placed in turn in said
copying light path;
scanning said color copy to detect three primary color components of light
reflected from said color copy using said three light measuring means, so
as to detect amounts of light reflected from said color copy for said
three primary colors;
logarithmically transforming said amounts of light into color densities for
said three primary colors;
providing relationships between said color densities and said three color
exposures for said three primary colors; and
controlling exposures for said three primary colors based on said
relationships, respectively.
16. A method as defined in claim 15, wherein said light measuring means are
photoconversion elements for blue, green and red light.
17. A method as defined in claim 15, prior to performing said step of
controlling exposures further comprising the steps of:
detecting exposures as desired values corresponding to white level copy
densities based on said relationships for said three primary colors; and
measuring a reflection plate having said white level copy densities to
detect light reflected from said reflection plate for said three primary
colors; and
wherein said controlling exposure step further comprises the step of
adjusting cyan, magenta and yellow filters so as to make said detected
exposures coincide with said desires values for said three primary colors,
thereby controlling said three primary color exposures.
18. A method as defined in claim 15, prior to performing said step of
controlling exposures further comprising the steps of:
detecting exposures as desired values corresponding to white level copy
densities, based on said relationships for said three primary colors; and
wherein said controlling exposure step further comprises the step of
adjusting cyan, magenta and yellow filters based on relationships between
opening positions of said cyan, magenta and yellow filters and light
amounts passed through said filters, said adjustments being made by
altering the opening position of said filters, respectively, thereby
controlling said three primary color exposures.
19. A method as defined in claim 17, wherein said plate is a cover having a
white reflection surface for covering said original.
20. A method of setting color copying conditions of a color copying machine
comprising the steps of:
making a color copy of density patterns in three primary colors;
scanning said color copy with illuminating light to detect the amount of
three primary color light components reflected from said color copy, using
said three primary light measuring means:
logarithmically transforming said light amounts into color densities for
said three primary colors;
providing relationships between said three primary color densities and said
light amounts previously memorized in a memory of said color copying
machine for said three primary colors;
detecting exposures as desired values corresponding to white level copy
densities based on said relationships for said three colors; and
measuring a reflection plate having said white level copy densities to
detect light reflected from said reflection plate for said three colors;
and
subsequently controlling three color exposures based on said relationship
by adjusting cyan, magenta and yellow filters positioned in a copying
light path so as to make said detected exposures coincide with said
desires values for said three colors, thereby controlling said three color
exposures.
21. A method of setting color copying conditions of a color copying machine
comprising the steps of:
making a color copy of density patterns in three primary colors;
scanning said color copy with illuminating light to detect the amount of
three primary color light components reflected from said color copy, using
said three primary light measuring means;
logarithmically transforming said light amounts into color densities for
said three primary colors;
providing relationships between said three primary color densities and said
light amounts previously memorized in a memory of said color copying
machine for said three primary colors;
detecting exposures as desired values corresponding to white level copy
densities based on said relationships for said three colors; and
subsequently controlling three color exposures based on said relationship
by adjusting cyan, magenta and yellow filters positioned in a copying
light path based on relationships between opening positions of said cyan,
magenta and yellow filters and light amounts passed through said color
filters to amounts of light passed through said color filters at said
positions for said three colors, thereby controlling said three color
exposures.
22. A method as defined in claim 1, wherein said illuminating light is in
the form of slit illumination.
23. A method as defined in claim 1, wherein said illuminating light is in
the form of a flying spot.
24. A method of setting color copying conditions of a color copying
machine, said copying machine being provided with scanning means for
scanning an original with illuminating light; three light measuring means,
one individual to each of three primary colors; and filters for regulating
respective components of light, said method comprising the steps of:
scanning a test chart having density patterns for said three primary
primary colors to detect three primary color components of light reflected
from said test chart using said three light measuring means, so as to
obtain three primary color exposures based on said three primary color
components and store them in a memory; and
setting copying conditions for said three primary colors, said setting step
comprising the steps of:
scanning said test chart to make a color copy thereof;
scanning said color copy to detect three primary color components of light
reflected from said color copy using said three primary light measuring
means, so as to detect reflected amounts of light for said three primary
colors;
logarithmically transforming said reflected amounts of light into color
densities for said three primary colors;
providing relationships between said three primary color exposures read out
from said memory and said three primary colors densities; and
adjusting said three color filters so as to make said relationships
coincide with predetermined relationships between color densities and
exposures for said three primary colors, respectively.
25. A method as defined in claim 24, wherein said three primary color
exposures are stored in said memory after being logarithmically
transformed.
26. A method as defined in claim 24, wherein said three primary colors are
cyan, magenta and yellow.
27. A method as defined in claim 26, wherein said three light measuring
means are photoconversion elements for sensing blue, green and red light,
respectively.
28. A method as defined in claim 24, wherein said color filters are cyan,
magenta and yellow filters.
29. A method as defined in claim 24, wherein said color filters are
adjusted based on relationships between said color filters between
positions in said copying light path and light amounts passed through said
color filters at said positions, respectively.
30. A method of setting color copying conditions of a color copying
machine, said copying machine being provided with scanning means for
scanning an original placed on a copying table with illuminating light and
three light measuring means, one individual to each of three primary
colors, said method comprising the steps of:
scanning a test chart having density patterns for said three primary
primary colors to detect three primary color components of light reflected
from said test chart using said three light measuring means, so as to
obtain three primary color exposures based on said three primary color
components and store them in a memory; and
setting copying conditions for said three primary colors, said setting step
comprising the steps of:
scanning said test chart again to make a color copy thereof;
scanning said color copy to detect three primary color components of light
reflected from said color copy using said three primary light measuring
means, so as to detect light quantities for said three primary colors;
logarithmically transforming said light quantities into color densities for
said three primary colors;
providing relationships between said three primary color exposures read out
from said memory and said three primary colors densities; and
controlling exposures for said three colors, based on said relationships,
respectively.
31. A method as defined in claim 30, wherein said three primary colors are
cyan, magenta and yellow.
32. A method as defined in claim 31, wherein said three light measuring
means are photoconversion elements for sensing blue, green and red light,
respectively.
33. A method as defined in claim 30, wherein said three primary color
exposures are stored in said memory after being logarithmically
transformed. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
The present invention relates to a method of setting color copying
conditions in color image copying and more particularly to a method of
setting color copying conditions when copying half-tone color images from
color originals.
In copying color images from color originals, using color image copying
machines such as electronic color image copiers, ink-jet color printers,
laser color printers, photographic color printers using reversal color
paper or diffusion transfer type photosensitive materials, video color
image copiers apparatus, or heat sensitive copying machines, it is
essential to reproduce a color image with both proper color density and
proper color balance. To provide well finished color copies, color copying
machines are generally adjusted to a proper color copying condition when
starting operations and periodically thereafter. The important factors on
which the color density and color reproductivity of color copies depend
are the dispersion in performance of the copying lens systems, changes in
the copying lens system due to aging, dispersion in characteristics of
developers, developer changes due to aging, and changes in developing
conditions. Therefore, color copying machines, even of the same type, set
their color copying conditions individually. For example, in silver salt
diffusion transfer processing type color copying machines, the optical
factors are dispersion and the changes due to aging of the light source,
the copying lens, color filters, reflection mirrors, light sensors, the
scanning speed at which a color original is scanned, and the like. The
factors which depend on photographic materials are the types of and the
changes due to aging of the photosensitive materials, the differences in
manufacturing batches, and the like. The factors which depend on
developing materials include the characteristic dispersion and changes due
to aging of developers. Furthermore, the factors which depend on
developing conditions include the time of developing, the temperature of
developing, and the like. In electrophotographic copying machines, other
factors include the sensitivity dispersion and the changes due to aging of
the photosensitive drums, the characteristic dispersion and changes due to
aging of toners, and the characteristic dispersion and changes due to
aging of chargers.
Heretofore, various systems for setting color copying conditions have been
well known. One such method, as is disclosed in, for example, Japanese
Patent Unexamined Publication No. 57-7051, comprises providing a
standardized density pattern near a table on which a color original is
placed, optically exposing a photosensitive drum to the standardized
density pattern to form an electostatic latent image on the drum,
detecting a surface voltage of the electrostatic latent image, and
controlling the charge and exposure of the photosensitive drum in such a
way as to equalize the detected surface voltage to a desired value.
In another system, as is described in Japanese Patent Unexamined
Publication No. 57-60348, a standardized density pattern is disposed
adjacent to the available area of a table on which a color original is
placed. A toner image of the standardized density pattern is formed on a
photosensitive drum and the density of the toner image is detected by
means of a special densitometer. The charge and exposure of the
photosensitive drum is controlled in such a way as to equalize the
detected density to a desired value.
A third system is disclosed in Japanese Unexamined Patent Publication No.
61-14663, where, while controlling the luminance of a light source or
developing a bias voltage for the developing device during copying, a
black and white copy with strips having different densities is made. This
black and white copy is visually examined to set the proper density
settings.
As disclosed in Japanese Unexamined Patent Application No. 60-243649, an
electrostatic latent image of a test chart is formed on a photosensitive
drum while increasing or decreasing the exposure. A toner image of the
electrostatic latent image formed on paper is visually examined to
determine the proper exposure.
A problem associated with the above described systems is the difficulty in
setting the copying conditions with high accuracy. For example, in the
first system, it is difficult to set the color copying conditions in
consideration of the developing conditions, the characteristic dispersion,
and changes due to aging of the development materials. It is also
difficult to set accurate color copying conditions because a corrected
exposure is determined based upon the density of a single point, on the
assumption that charging is proportional to exposure. Further, the use of
this technique is limited to specific types of copying machines.
The second system described above allows setting the color copying
conditions in consideration of the changes and dispersion of various
factors, in that a special densitometer is employed to measure the density
of the toner image. However, since measurement is effected at a single
point, it is hard to set correct color copying conditions. It is also
difficult to apply this system to silver salt type copying machines or
color copying machines using diffusion transfer type photographic
materials.
The remaining color copying systems require visual examination of a black
and white copy in order to correct the exposure levels. High skill is
required to correct the exposures for all three colors (blue, red, and
green) to provide well balanced copies.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of setting
color copying conditions with high accuracy. It is another object of the
present invention to provide a color copying condition setting method
which can be applied to various types of color copying machines.
In the invention, a test chart having a plurality of density patterns for
each of the three primary colors is employed. Each pattern includes a
plurality of smaller divisions having different densities. The test chart
is placed on a table on which color originals to be copied are placed and
is scanned to measure the three color components of the reflected light so
as to detect the light intensities based on which exposures are determined
for each of the three colors. After the light intensity measurement, the
test chart is again scanned to make a color copy thereof. The color copy
is then placed on the table and scanned to measure the three color
components of the reflected light to detect the densities of each of the
three colors as copied. Characteristic data of the copy density with
respect to the exposure is prepared for each color. Color filters, for
example cyan, magenta and yellow filters for regulating the three color
components of the copying light are controlled so as to make the three
prepared characteristics coincide with standardized characteristic data
previously prepared individually for each of the three colors.
Based on the measured and the standardized characteristic data, exposure
differences for the same copy density are calculated. The color filters
are controlled so as to cancel the exposure differences.
The invention also allows the use of a pseudo test chart which is prepared
by variously combining color filters such as cyan, magenta and yellow
filters.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be described with reference to plural
embodiments shown in the accompanying drawings, wherein identical
reference numerals designate identical or similar parts throughout the
several views, and in which:
FIG. 1 is a fragmentary cross-sectional illustration showing a color
copying machine using a silver salt diffusion transfer process and
embodying the present invention;
FIG. 2 is a cross-sectional view of a light collecting means used the color
copying machine of FIG. 1;
FIG. 3 is a fragmentary illustration of a light measuring means used in the
color copying machine of FIG. 1;
FIG. 4 is a block diagram of an exposure condition setting means used in
the color copying machine of FIG. 1;
FIG. 5 is an explanatory illustration of a test chart;
FIG. 6 is a flowchart showing one example of how the copying conditions are
set in the color copying machine of FIG. 1;
FIG. 7 graphically illustrates the density distributions of the test chart
of FIG. 5;
FIG. 8 graphically illustrates the relationship of filter position to the
logarithm of exposure for each of the three colors;
FIG. 9 illustrates the relationship between filter position and the
logarithm of the amount of light;
FIG. 10 is a flowchart similar to that of FIG. 6 but showing another
example of how the copying conditions of the color copying machine of FIG.
1 may be set;
FIG. 11 is a set of graphs similar to those of FIG. 8, each showing the
relationship between position and the logarithm of the exposure;
FIG. 12 is a graph similar to that of FIG. 9 showing the relationship
between filter position and the logarithm of the amount of light;
FIG. 13 is an explanatory illustration showing the sequence of forming a
pseudo test chart; and
FIG. 14 is another example of a color image copying machine embodying the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to FIG. 1, there is illustrated a silver salt diffusion
transfer processing type copying machine in which the color image copying
condition setting method according to the present invention is embodied.
On a transparent table 10, a test chart 11 is placed in position with its
front surface down and covered by a opaque cover 12 having a white inner
surface. On the under surface of the transparent table 10 is provided a
standardized reflection plate 13 which reflects light which is in turn
detected to check the light intensity of the lamp 15 and the
transmittances of the color filters, as described subsequently.
Light source unit 14 includes illumination lamp 15, reflector 16, and
reflection mirror 17. Unit 14 is capable of reciprocally moving in
parallel with the table 10 to scan lengthwise over the test chart 11 on
the table 10 with the illuminating light. Scanning can take place using
either the slit method or a flying spot. Mirror unit 18 supports therein a
pair of reflection mirrors 19, 20 disposed facing its each other at a
90.degree. angle so as to reflect light through 180.degree. . The mirror
unit 18 is maintained in a selected position but is moved when the copying
ratio is changed.
A lens unit 22 has front and rear lens groups 23, 24, each of which is
depicted as a single element lens group for simplicity. Also included are
yellow Y, cyan C and magenta M color filters disposed between the front
and rear lens groups, and oppositely movable aperture plates 25, 26
disposed behind the rear lens group 24. The lens unit 22 is synchronized
with the light source unit 14 to focus an image of the test chart 11 on
photosensitive paper 36. Each filter Y, C, M is independently movable into
and out of the optical path of the first and second lens groups 23, 24 so
as to regulate the amount of exposure light passed therethrough in order
to control the light components and hence the color balance of the
exposure light.
Fixed mirrors 28, 29 are used to direct light from the lens unit to a
swingable mirror 31, which in turn is made capable of directing light to
the photosensitive paper 36. The swingable mirror 31 is pivoted at 30, and
swings out of the light path during pre-scanning so as to allow light
reflected from the test chart 11 to reach a light measuring unit 33.
A light collecting mirror unit 32 is brought into the optical path as shown
by the dotted line in FIG. 2 when pre-scanning is conducted. As is shown
in detail in FIG. 2, the light collecting mirror unit 32 comprises a
plurality of reflection mirrors 32a arranged to reflect incident light
toward the light measuring unit 33.
As is shown in FIG. 3, the light measuring unit 33 comprises sensors 33a,
33b and 33c for red, green and blue light, respectively, to allow the
detection of the light components in the respective colors.
Paper magazine 35 contains a roll of the photosensitive paper 36 which is
processable using a silver salt diffusion transfer method. The paper 36 is
withdrawn by means of a pair of rollers 37, 38 disposed in front of the
paper magazine 35, and is cut to a predetermined length by means of a
cutter 39. A cut paper sheet 36a thus formed is nipped at its forward end
by a pair of rollers 42, 43. Between the pair of rollers 42, 43 and a
second pair of supporting rollers 40, 41 there is formed an exposure space
located just beneath the swingable mirror 31.
During the copying of an image of a color original, rollers 40-43 are
driven in synchronism with the movement of the light source unit 14 to
transport the paper sheet 36a toward a rotary drum 45. Disposed
surrounding the rotary drum 45 are a guide member 46 and a guide roller
47. The paper sheet 36a, after having been exposed to the light reflected
by the test chart 11, is transported by the rotary drum 45 until it is
stopped by abutting a first stopper 48.
An image receiving sheet holding cassette 53 is mounted on the copying
machine. In the cassette 53 there is a stack of diffusion transfer
processing type image receiving sheets 50, each of which is provided at
its leading end with a rupturable pod containing a processing liquid and a
funnel member 52 for leading the processing fluid out of the pod. A
feeding roller 54 is brought into contact with the upper most image
receiving sheet 50 upon mounting the cassette 53 on the copying machine.
The roller 54 feeds the uppermost sheet to a pair of nip rollers 55, 56
during pre-scanning. Upon exposing the photosensitive paper sheet 36a, the
nip rollers 55, 56 are driven in a well known manner to transport the
image receiving sheet 50 to second stopper 57 which halts the image
receiving sheet 50 at its leading end and places it in position. It is to
be noted that the nip rollers 55, 56 nip the side margins of the image
receiving sheet 50 so as to avoid accidentally releasing the processing
liquid within the pod 51. The photosensitive paper 36 and the image
receiving sheets 50 are the same in mechanical and chemical construction
as those well known in the instant photography art and now available on
the market.
The exposed photosensitive paper sheet 36a is attached at its leading end
to the image receiving sheet 50 with the aid of, for example, heat sealing
means 60. The coupled sheets are then passed between a pair of pressure
applying rollers 61, 62 so as to rupture the pod and release the
processing liquid between the two sheets. As the sheets 36a and 50 are
passed between the pressure applying rollers 61, 62, the released
processing liquid is distributed between the sheets in a thin uniform
layer. For short time duration diffusion transfer processing, the
overlapped sheets as a unit are placed on a constant temperature plate 63
for a given time. By separating the image receiving sheet 50 from the
photosensitive paper sheet 36a, the finally developed image of the test
chart 11 may be visualized on the image receiving sheet 50.
FIG. 4 illustrates the copying condition setting circuit. Sensors 33a, 33b
and 33c which may be designated as red, green and blue sensors,
respectively, receive light and provide electrical signal according to the
amounts of light which they receive. These signals, after amplification,
are converted to digital signals by means of A/D converters 65, 66, 67,
respectively. The digital signals are then subjected to signal processing
in look-up tables 68, 69 and 70. Each look-up table includes two data
tables A and B. Data table A contains data for correcting the signal for
the sensitivity of each sensor to provide data on the corrected exposure.
Data table B memorizes data for correcting the signal according to the
sensitivity of each sensor and converts the corrected signal into
logarithmic form. Each look-up table is controlled by a signal from the
I/O port 71 to select table data A, B.
The outputs from the look-up tables 68-70 are sent to RAM 73 through I/O
port 71 and CPU 72. The CPU 72 executes operations according to a program
sequence memorized in ROM 74, as described hereafter.
Connected to the I/O port 71 are a mode selection key 76 for selecting
either the copying condition setting mode or the reproduction mode, a
reproduction key 77 for starting the operation of the machine according to
the selected mode, and color correction keys 78-80 for manually setting
desired color corrections with respect to the automatically set copying
exposures.
Upon setting the copying exposures or manually effecting color corrections,
the CPU 72 causes motors 85-87 to rotate via drivers 82-84 so as to adjust
the color filters Y, M and C. A driver 88 is provided to start motor 89 so
as to move the aperture plates 25, 26 close to or apart from each other in
order to regulate the amount of light passing therethrough.
Referring now to FIG. 5, an example of a test chart is shown. The test
chart 11 is provided at one end with a white division 11a, and a plurality
of filter strips 11b with different densities are provided thereafter and
are distributed at regular intervals. The test chart 11 is placed on the
table 10 in such a way that the strips 11a and 11b extend perpendicularly
to the direction in which the light source unit 14 moves. In this
embodiment, the test chart 11 has four strips 11b for each color, each of
a different density. Thus, in total, the test chart 11 has one white strip
and four different gradations of each of cyan, magenta and yellow.
The method by which copying conditions are set will now be described with
reference to FIG. 6. The mode selection key 76 is operated to select the
copying condition setting mode. After placing the test chart 11 on the
table 10, the reproduction key 77 is operated to start the copying
condition setting operation. Motors 85-89 start to rotate, setting the
filters Y, M and C and the aperture plates 26, 26 to their normal
positions. Simultaneously, the light collecting mirror unit 32 and the
swingable mirror 31 are moved to the positions shown in dotted lines in
FIG. 1. Thereafter, the light source unit 14 and the lens unit 22 move in
synchronism with each other to effect a first scan of the standardized
reflection plate 13 and the test chart 11 with illuminating light.
The light reflected from the standardized reflection plate 13 and the test
chart 11 is directed toward the light collecting unit 32 via mirrors 17,
19, 20, lens unit 22, and mirrors 28, 29 in this order. As is shown in
FIG. 2, the light collecting mirror unit 32 collects all or part of the
reflected light and directs it to the light measuring unit 33. The light
measuring unit 33 has sensors 33a to 33c individual to each color, and
thereby detects the three color components of the light.
Outputs from the sensors 33a to 33c are, after being converted into digital
signals, sent to the look-up tables 68-70 by color. On the first scan,
each look-up table selects table B, and the digital signal is transformed
into a logarithmic value to provide exposure data which is in turn
memorized in the RAM 73.
When the light source unit 14 reaches the right extremity in FIG. 1, the
first scan is completed and the copying mode can commence. At this time,
the swingable mirror 31 is brought into the optical path P and the light
collecting mirror unit 32 is moved out of the optical path. Thereafter,
transportation of the photosensitive paper 36 and the image receiving
sheet 50 is carried out. In more detail, the rollers 54 to 56 start their
rotation, so as to withdraw the foremost image receiving sheet 50 until
the image receiving sheet 50 is stopped at the second stopper 57. The
rollers 37 and 38 simultaneously start their rotation, so as to withdraw
the photosensitive paper 36 by a predetermined length. Upon drawing out a
predetermined length of paper 36, the rollers 42 and 43 nip the leading
end of the paper and, simultaneously, the cutter 39 cuts the paper to a
predetermined length to provide the paper sheet 36a. Photosensitive paper
sheet 36a is further transported until the leading end thereof is nipped
by the rollers 40, 41. When the sheet 36a is in position, the rollers
40-43 all stop.
When the photosensitive sheet 36a and the image receiving sheet 50 are both
in position, the light source unit 14 returns to its initial position so
as to effect a second scan of the test chart 11. In synchronism with the
movement of the light source unit 14 to the left as viewed in FIG. 1, the
rollers 40-43 rotate to continuously transport and expose the
photosensitive paper sheet 36a to illuminating light. In this manner, a
latent image of the test chart 11 is formed in the photosensitive paper.
The sheet containing the latent image thereon is transported by the rotary
drum 45 and is placed in position at the first stopper 48. When the
photosensitive sheet is stopped at the first stopper 48, the rotary drum
45 stops to maintain the rear end of the photosensitive sheet between the
roller 47 and the drum 45. When the rotary drum 45 stops, the first
stopper 48 is moved out of the path of the photosensitive sheet 36a.
Next, the rollers 55 and 56 are actuated to rotate and thereby transport
the image receiving sheet 50 under the photosensitive sheet 36a. When the
leading end of the sheet 50 is stopped by the second stopper 57, the
rollers 55 and 56 are stopped so as to position the sheet 50 such that the
funnel member 52 overlaps the leading end of the sheet 36a. The heat
sealing device 60 moves downwardly to weld the leading end of the
photosensitive sheet to the funnel member 52. Due to this welding
operation, the sheet 36a is maintained in correct registry with the image
receiving sheet 50 during processing so as to prevent the reproduced image
from being blurred or changed in position. To enable easy welding, a hot
melt adhesive agent is applied to the upper surface of the funnel member
52 in advance.
After the second stopper 57 has been removed from the path of the sheet 50,
the rollers 45 and 46 are actuated again so as to forward the overlapped
sheets 36a, 50. During this advancement, the roller 47 rotates following
the movement of the sheet 36a. Since the pressure applying rollers 61, 62
are synchronized with the rollers 55, 56, the pressure applying rollers
61, 62 nip and transport the overlapped sheets 36a, 50 therebetween while
applying pressure. When the leading end of the image receiving sheet 50
passes between the pressure applying rollers 61, 62, the pod 51 is
ruptured to release the processing liquid between the overlapped sheets.
As the sheets continue to be transported, the processing liquid is
distributed in a uniform layer. The overlapped sheets are then left on the
constant temperature plate 63, which is heated to approximately 25.degree.
C., for a predetermined time. After this time, the sheet 50 is separated
from sheet 36a to provide a color positive image of the test chart 11
reproduced thereon by the well known diffusion transfer processing
technique.
Thereafter, the test chart 11 is replaced with the color copy (the sheet 50
on which the test chart 11 has just been copied) and the copying key 77 is
again operated to start a third scan which is effected in the same manner
as the first scan so as to measure the color components of the copy using
the measuring unit 33. In this third scan, each look-up table 68, 69, 70
selects table B to provide an output from the sensor 33a, 33b, 33c in
logarithmic form. Based on the logarithmic outputs of the standardized
reflection plate and the color copy, the look-up table provides a density
signal representing a copy density. This density signal is memorized in
the RAM 73 to finish the third scan. After the third scan, the light
source unit 14 returns to its initial position shown in FIG. 1.
The CPU 72 retrieves the logarithmically transformed signals representative
of the exposure obtained by the first scan and the copy density obtained
by the third scan from the RAM 73 and provides characteristic data 90, 91,
92 indicating the relationship between logarithmically transformed
exposures and copied densities for each color, as shown in FIG. 8. In this
embodiment, the color copy is measured at four points for each color, and
the densities of adjacent divisions are connected by a straight line.
Densities outside the opposite end points are shown as extensions of the
straight lines connecting the two adjacent points. Alternatively, the
characteristic data may be formulated by deriving a characteristic curve
which intersects the respective four density points according to a
Lagrange interpolation. The characteristic data sets 90-92 are used either
as table values or in equational form (using either the straight lines or
the generated curve).
The characteristic data are used in the following manner. Taking blue as an
example, an exposure EB1 is obtained from the characteristic curve 90 for
a point specified by density D1, while an exposure EB2 is obtained from a
standardized characteristic curve 94 for the same density. The exposure
difference .DELTA. E1 between the exposures EB1 and EB2 is obtained. In
the same manner, exposure differences .DELTA. E2 and .DELTA. E3 are
obtained for red and green. The standardized characteristic data may be
provided in the ROM in advance, either when designing the copying machine
or in the previously described manner when installing the copying machine.
After the exposure differences are obtained, the light source 14 is ready
for the next scan. The standardized reflection plate 13 is illuminated and
the light reflected thereby is measured by the light measuring means 33 to
detect the exposures for the three colors. According to the three color
exposures, the color filters Y, M and C are adjusted in such a way as to
cancel the exposure differences for each of the colors, thereby completing
the setting of the color copying conditions.
The standardized white color reflection plate may be replaced with a gray
color reflection plate. Alternatively, a characteristic curve of the
relationship between the filter position and the logarithm of light
quantity may be used to adjust the color filters Y, M and C. Taking the
yellow filter Y as an example, as is shown in FIG. 9, the amount of light
EB4 which is distanced .DELTA. E1 from the amount of light EB3 when the
yellow filter Y is at its normal position S is determined. Using the
characteristic curve, a position A at which the yellow filter can provide
light amount EB4 is determined. Subsequently, the yellow filter Y is moved
to the position A from the normal position S.
After setting the color copying conditions, the mode selection key 76 is
operated to select the copy mode. As a result of this selection, the light
collecting mirror unit 32 is brought into the optical path P and the
swingable mirror 31 is moved out of the optical path. A color original to
be copied is placed on the table 10 and is covered with the light opaque
cover 12. Thereafter, when operating the copying key 77, the color
original is copied in the same manner as the test chart 11 was copied. The
color original is copied with the light source unit 14 moving toward the
right as viewed in FIG. 1.
Reference is now made to FIGS. 10-12 which illustrate another preferred
embodiment of the invention, also usable in the same copying machine shown
in FIGS. 1-4. In this embodiment, the same characteristic curves | | |
