Image exposure apparatus and image exposure method

An image exposure apparatus and method generates a first optical image light and a second optical image light. The first optical image is input to a read side of a spatial light modulating element, and the second optical image light is input to a write side of the spatial light modulating element, so that the first optical image light is modulated by the second image light to be output from the read side again; and exposing the light sensitive material to the output image from the read side, that is the both images are combined, or the intensity of both image lights are modulated.

BACKGROUND OF THE INVENTION 
The present invention relates to exposure to an image of a photographic 
film, and particularly relates to an image exposure apparatus and an image 
exposure method in which a photosensitive material is exposed to add any 
photographic effects to an image of a photographic film. For example, as 
the photographic effects, the contrast of an image is corrected or 
controlled, and photographic paper is exposed to the corrected or 
controlled image light. Further there is a photographic effect in which a 
photosensitive material is exposed to a combination of an image of a 
photographic film and another image. 
Recently, when image exposure is conducted in a photographic printer, it is 
often to expose photographic paper to a combination of an image light of a 
negative film and another image light such as a frame, a graphic, or 
characters. 
In the prior art, this exposure is conducted while inserting a pattern mask 
such as a lith film into an optical path, writing image information which 
is to be combined, to photographic paper by a laser, or inserting a liquid 
crystal mask into an optical path. 
Such exposure has problems as follows: In exposure using a pattern mask, 
the pattern mask must be inserted in the vicinity of photographic paper. 
As a result, the operations of inserting and detaching the pattern mask 
must be conducted in a dark room. 
In exposure using a laser, due to scanning exposure a considerably long 
exposure time is required and the structure of movable parts for 
conducting the scanning is complicated. 
In exposure using a liquid crystal mask, pixels constituting the liquid 
crystal mask are arranged in a matrix. Particularly when exposure to a 
curved image is conducted, therefore, there arises a problem in that the 
resulting image fails to form smooth lines and has low definition. 
Alternately, the contrast characteristic afore-said of an image recorded on 
a photographic film depends on the conditions at thus recording. 
Black-and-white photographic paper or color photographic paper is exposed 
to the image light having the contrast. 
With respect to black-and-white photographic paper, a wide variety of kinds 
which have different tones ranging from high contrast to low contrast are 
available. When a black-and-white image is to be printed, photographic 
paper having a tone which is suitable for the contrast of an image of a 
photographic film or the intention of the photographer is selected. 
With respect to color photographic paper, unlike black-and-white 
photographic paper, a wide variety of kinds which have different tones are 
not available, and only one kind having a certain tone is available. When 
a color image is to be printed, therefore, a contrast conversion is 
performed so that an image of a photographic film is expressed under the 
density latitude which can be expressed by the color photographic paper, 
thereby obtaining a printed image of low or high contrast. 
When an image of a photographic film is to be printed while its tone is 
changed to a lower level, exposure is conducted while inserting a mask in 
which the brightness pattern is the inversion of that of the negative 
image, into an optical path. In contrast, when the image of the 
photographic film is to be printed while its tone is changed to a higher 
level, exposure is conducted while inserting a mask in which the 
brightness pattern is the same as that of the negative image, into the 
optical path. 
In an example of a known contrast correction method which does not use such 
a mask, a liquid crystal panel where electrodes are arranged in a matrix 
form is used, and the transmittance of each pixel is controlled so as to 
obtain a desired amount of light. According to this method, the contrast 
of an image which is to be printed can be corrected by controlling the 
voltage applied to the electrodes. 
When an image is to be printed to black-and-white photographic paper, as 
described above, various kinds of photographic paper having different 
tones may be available. However, photographic paper of a desired tone is 
not always available. 
When an image is to be printed to color photographic paper, considerable 
time and labor are required to determine an appropriate mask and insert 
the mask into an optical path, thereby requiring a great amount of skill. 
In the case where an image is to be printed to color photographic paper 
with using the above-mentioned liquid crystal panel in place of a mask, 
the voltage to be applied must be controlled for every region. A 
configuration of the circuit is complicated. 
In a color image exposure apparatus of the level which is usually 
obtainable in the market, therefore, it is difficult to attain a simple 
exposing process in which the contrast of an image is corrected. 
SUMMARY OF THE INVENTION 
The invention has been conducted in view of the above-mentioned 
circumstances. It is an object of the invention to provide an image 
exposure apparatus and an image exposure method in which an image Of a 
negative film can easily be combined with another image such as that of a 
pattern mask and it is possible to expose photographic paper to a high 
definition image. 
Further there is another object to provide an image exposure apparatus 
which can easily correct the contrast of an image of a photographic film. 
In order to accomplish the above objects, the invention is to provide a 
method and an apparatus for exposing a light sensitive material, in which 
a first optical image light is input to a read side of a spatial light 
modulating element, a second optical image light is input to a write side 
of the spatial light modulating element, so that the first optical image 
light is modulated by the second image light to be output from the read 
side again, wherein said light sensitive material is exposed to said 
output image light from the read side. 
Further, means for generating the first image and means for generating the 
second image generating have the same light source, the first and second 
images being split from one original image from the light source by means 
of a half mirror, whereby the spatial light modulation means modulate 
intensity of the first image light entering through the read side in 
accordance with intensity of the second image light entering through the 
write side. 
Furthermore, the apparatus of the invention is provided with a driving 
means for supplying a predetermined voltage to the transparent electrodes 
to change orientation of the liquid crystal material, a detecting means 
for detecting a density of the output image from the read side. And then a 
control means controls the driving means in accordance with the density of 
the output image so as to adjust a contrast range of the output image into 
a latitude of the light sensitive material. 
According to the image exposure apparatus and method of the invention, 
image information generated by the first image information generation 
means is introduced from the read side of the spatial light modulation 
means, and then modulated with image information generated by the second 
image information generation means. The modulated image information is 
then output. 
On the other hand, in another example, the image entering through the read 
side of the spatial light modulation means is same as the image entering 
through the write side of the spatial light modulation means. Therefore, 
the intensity of light entering through the read side is modulated in 
accordance with the intensity of image light entering through the write 
side. Namely, since the image light has a density distribution 
corresponding to the original image, the intensity of the 
output(modulated) light from the read side corresponds to the density 
distribution. 
Furthermore, the intensity of the output image from the read side is also 
modulated in accordance with a supply voltage to the spatial light 
modulation means, the supply voltage is controlled in accordance with the 
density of the output image so as to adjust a contrast range of the output 
image into a latitude of the light sensitive material. 
A spatial light modulator (hereinafter, abbreviated as "SLM") functioning 
as the spatial light modulation means has a basic structure which includes 
address side material, modulation material, and mirror separating 
therebetween, e.g. a configuration consisting of a photoconductive film, a 
light shielding film, a dielectric mirror, and a liquid crystal in which 
liquid crystal molecules are aligned in a predetermined degree by 
orientation films are arranged in this sequence and provided between a 
pair of glass substrates on which transparent electrodes are respectively 
formed so as to oppose to each other (Japan Society for the Promotion of 
Science, "Handbook of liquid crystal devices," Beam address system, pp. 
434-436 (1989); Takizawa, Kikuchi and Fujikake, "Spatial light modulator 
using a light scattering liquid crystal complex," NHK Giken R & D, No. 12, 
pp. 11-12 (1992); and Okano and Kobayashi, "Liquid crystal, Application," 
chap. 10, Photoconductive liquid crystal display, pp. 223-228 (1985)). 
When image light is introduced into the photoconductive film constituting 
the SLM, the impedance of the photoconductive film is lowered, and as a 
result an electric field is generated in a range of the portion of the 
liquid crystal corresponding to the introduced image light. This causes an 
electrooptic effect to be produced in the liquid crystal passing through 
the mirror, that is the SLM modulates the image light introduced from the 
write side and reflects the image light at the mirror to output the 
modulated image light. The output image light is the one which is a 
combination of the image information sets respectively generated by the 
first and second image light generating means. The output image light is 
supplied to exposure means which in turn conducts exposure to a combined 
image. 
Thus the first image light generating means irradiates an original image 
such as an image of a photographic film, thereby obtaining image light. 
The second image light generating means irradiates a pattern mask on which 
a desired image pattern to be combined with the original image is formed, 
or an image of a photographic film, thereby obtaining a required image. 
Alternatively, the second image light generating means may be the one 
which operates light emitting means such as an EL (electroluminescence) 
display device or a CRT (cathode ray tube) on which a desired image is 
displayed, so as to emit light, thereby obtaining required image. 
Further, the output image light from the read side corresponds to the 
intensity of light entering through the write side. The control means 
determines a preferred exposing amount to control the intensity of the 
modulated image light and irradiating period to the photo-sensitive 
material so as to adjust a contrast range of the output image into a 
latitude of the light sensitive material. The intensity of the modulated 
image light is controlled by the driving voltage to be applied to the SLM, 
and the irradiating period is controlled by the supplying period of the 
driving voltage. 
The liquid crystal provided in the SLM may be selected from a TN (twisted 
nematic) liquid crystal, a GH (guest host) liquid crystal, a surface 
stabilized ferroelectric liquid crystal, and a polymer dispersion liquid 
crystal. 
The TN liquid crystal has the following configuration: A composition 
wherein a trace of a chiral material for suppressing generation of 
reversely twisted domains is added to a multicomponent nematic liquid 
crystal in which molecules twisted by 45 deg. are aligned. and which has a 
positive anisotropy of dielectric constant is provided between transparent 
electrodes that underwent an orientation process and are respectively 
formed on a pair of glass substrates so as to oppose to each other. A 
polarizing plate is disposed on the outer face of each of the glass 
substrates. 
In the SLM in which the TN liquid crystal is provided, when light from the 
write side enters the photoconductive film, the impedance of the 
photoconductive film is lowered. Therefore, an electric field is applied 
to the liquid crystal portion corresponding to the impedance-lowered 
portion, so that the alignment manner of the liquid crystal molecules is 
changed. Light from the read side is modulated by the liquid crystal and 
the polarizing angles at transmission of the polarizing plates become 
optically parallel, whereby the light is allowed to pass through the 
polarizing plates. 
On the other hand, when image light from the write side enters the 
photoconductive film, the same image light from the read side passes 
through the polarizing plate disposed in the light output side, to enter 
the SLM, and the direction of deflection is optically changed, whereby the 
intensity of emitted light which has passed through the polarizing plate 
for the light emitting side can be modulated. 
The phenomenon that direction of deflection becomes parallel with the 
direction of polarization of entering light occurs in the case where the 
intensity of light entering the write side is high, or light which has 
passed through a lower-density portion of the negative image is written 
into the SLM. In this case, if the polarizing plate for the light emitting 
side is orthogonally disposed, the intensity of light to which the 
photographic paper is exposed is decreased, resulting in that the contrast 
of the image is suppressed. 
In contrast, if the polarizing plate for the light emitting side is 
disposed in parallel, the intensity of emitted light becomes high when the 
intensity of light entering the write side is high. Therefore, also the 
intensity of light to which the photographic paper is exposed is 
increased, resulting in that the contrast is emphasized. 
The GH liquid crystal is configured so that a liquid crystal in which a 
dichroic dye is dissolved in a multicomponent nematic liquid crystal in 
which molecules are aligned twistedly and which has a positive anisotropy 
of dielectric constant is provided between transparent electrodes that 
underwent an orientation process and are respectively formed on a pair of 
glass substrates so as to oppose to each other. Molecules of the dichroic 
dye are aligned in parallel with those of the nematic liquid crystal. When 
the alignment of the liquid crystal molecules is changed by applying an 
electric field, therefore, also the alignment of the dichroic dye 
molecules is changed. The optical absorption characteristic of the 
dichroic dye in the major axis direction is different from that in the 
minor axis direction. 
The SLM in which the GH liquid crystal is provided modulates light from the 
read side in accordance with the change of the optical absorption 
coefficient due to the alignment of the dichroic dye molecules. 
In the case of controlling the intensity of image light, the optical 
absorption coefficient depends on the kind of the dichroic dye. By 
adequately selecting the kind of the dichroic dye, it is possible to 
produce a device for emphasizing the contrast or a device for suppressing 
the contrast. 
More specifically, in the case where a dye is used in which the absorption 
coefficient obtained when light passes along the major axis of the dye 
molecules is smaller than that obtained when light passes along the minor 
axis of the dye molecules (negative dichroism), the transmittance of the 
portion to which an electric field is applied becomes greater than that of 
the other portion. Therefore, the intensity of light to which the 
photographic paper is exposed is increased, resulting in that the contrast 
is emphasized. 
In contrast, in the case where a dye is used in which the absorption 
coefficient obtained when light passes along the major axis of the dye 
molecules is greater than that obtained when light passes along the minor 
axis of the dye molecules (positive dichroism), the transmittance of the 
portion to which an electric field is applied becomes smaller than that of 
the other portion. Therefore, the intensity of light to which the 
photographic paper is exposed is decreased, resulting in that the contrast 
is suppressed. 
In the SLM wherein, when an electric field is not applied to a nematic 
liquid crystal having a negative anisotropy of dielectric constant, liquid 
crystal molecules are aligned in the direction perpendicular to the 
substrate, and the relationship between the positiveness and negativeness 
of dichroism of the dye and of the emphasis and suppression of contrast is 
contrary to that described above. This is summarized in Table 1 below. 
TABLE 1 
______________________________________ 
Anisotropy of dielectric 
Liquid constant 
Dye crystal Positive Negative 
______________________________________ 
Dichroism 
Positive Suppression 
Emphasis of 
of contrast 
contrast 
Negative Emphasis of 
Suppression of 
contrast contrast 
______________________________________ 
The SLM in which the GH liquid crystal is provided may or may not includes 
with polarizing plates. The SLM which is not provided with polarizing 
plates has a drawback that the contrast of light emitted therefrom is 
lower than that of light emitted from the SLM wherein the TN liquid 
crystal is provided, but has an advantage that the optical loss in the SLM 
is small. 
On the other hand, the surface stabilized ferroelectric liquid crystal has 
a configuration wherein a chiral smectic liquid crystal is provided 
between transparent electrodes that underwent a parallel orientation 
process and are respectively formed on a pair of glass substrates, so that 
the liquid crystal has a layer thickness of 1 to 2 .mu.m. In a chiral 
smectic liquid crystal, the molecular major axes are inclined at a fixed 
angle to the layer. When a pulse electric field of an adequate polarity is 
applied to a chiral smectic liquid crystal, the molecule major axes are 
inverted to the direction which is symmetrical about the normal of the 
layer. 
The SLM in which the surface stabilized ferroelectric liquid crystal is 
provided modulates linearly polarized light from the read side into 
elliptically polarized light or circularly polarized light, in accordance 
with the change of the inclination of the major axes of the liquid crystal 
molecules. 
In the case of controlling the intensity of image, when light having the 
direction of deflection which is parallel with or perpendicular to the 
major axis direction of the liquid crystal molecules passes the liquid 
crystal, the deflection state of the light is not changed. When a pulse 
electric field is applied to the liquid crystal so that the major axis 
direction of the molecules is inverted, the light is modulated and the 
photographic paper is exposed to light of a desired strength, whereby the 
contrast of an image is controlled. 
On the other hand, the polymer dispersion liquid crystal is a complex 
material in which polymers of the solid phase and a liquid crystal coexist 
while they are dispersed. There are various ratios of the amounts of these 
phases, and steric relationships. The scattering state of the polymer 
dispersion liquid crystal is changed in accordance with an electric field 
applied to the liquid crystal. 
The SLM in which the polymer dispersion liquid crystal is provided 
modulates light from the read side depending on the change of the 
scattering state of the liquid crystal. 
Accordingly, when the intensity of light entering through the write side is 
high so that the electric field applied to the liquid crystal is high, the 
degree of scattering of the liquid crystal is low, and therefore the 
intensity of light emitted from the SLM is high. Accordingly, also the 
intensity of light to which photographic paper is exposed becomes high, 
resulting in that the contrast of an image is emphasized. 
In contrast, when the intensity of light entering through the write side is 
low so that the electric field applied to the liquid crystal is low, the 
degree of scattering of the liquid crystal is high, and therefore the 
intensity of light emitted from the SLM is low. Accordingly, also the 
intensity of light to which photographic paper is exposed becomes low, 
resulting in that the contrast of an image is suppressed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
[First Embodiment] 
Hereinafter, an embodiment of the invention will be described with 
reference to the drawings. 
FIG. 1 shows an image exposure apparatus of the embodiment of the 
invention. Light from a light source 101 is reflected by a reflector 103 
to proceed through color filters 104 of desired colors to a diffusion 
plate 105. After diffused by the diffusion plate 105, the light enters a 
negative film 107. 
The light which has been transmitted through the negative film 107 passes 
through a lens 109 and a half-mirror 111, and is then converted into 
parallel beams by a lens 113 to enter an SLM 115. 
On the other hand, light from another light source 117 is reflected by a 
reflector 119 and then diffused by a diffusion plate 121. Thereafter, the 
light enters a pattern mask 123 on which an image pattern including a 
frame, a graphic, characters or the like is previously formed. The light 
which has been transmitted through the pattern mask 123 enters the SLM 
115. 
Hereinafter, the SLM 115 will be described with reference to FIG. 2. As 
shown in FIG. 2, the SLM 115 has a configuration wherein a photoconductive 
film 209, a light shielding film 211, a dielectric mirror 213, and a TN 
liquid crystal 219 in which liquid crystal molecules are aligned in a 
predetermined degree by orientation films 215 and 217 are arranged in this 
order and fixed between a pair of glass substrates 201 and 203 on which 
ITO (Indium Tin Oxide) transparent electrodes 205 and 207 are respectively 
formed so as to oppose to each other. A driving voltage is applied between 
the transparent electrodes 205 and 207. The glass substrate 203 is further 
provided with a polarizing plate 204. 
Next, the operation of the SLM 115 will be described. When one light enters 
a write side of the SLM 115 (the side in which the glass substrate 201 is 
disposed), the impedance of the photoconductive film 209 is lowered 
according as that the intensity of the entering light increases, and the 
liquid crystal 219 is subjected to an electric field generated 
corresponding to the light intensity distribution. The liquid crystal in 
the portion effected by the electric field produces an electrooptic effect 
so that another light entering through a read side of the SLM 115 (the 
read side in which the glass substrate 203 is disposed) is modulated. 
As shown in FIG. 1, the image light from the pattern mask 123 enters the 
write side of the SLM 115, and the image light from the negative film 107 
enters the read side. 
When the photoconductive film 209 constituting the SLM 115 is irradiated 
with the image light which has been transmitted through the pattern mask 
123, the impedance of the irradiated area of the photoconductive film 209 
is lowered, and an electric field is generated at the area of the liquid 
crystal 219 corresponding to the irradiated area. This causes the 
orientation of the liquid crystal 219 to change in accordance with the 
image of the pattern mask 123, so that the image light which has been 
transmitted through the negative film 107 is modulated by the liquid 
crystal 219 and then emitted from the SLM. 
The light which is emitted from the read side in this way is a combination 
of the image of the pattern mask 123 and that of the negative film 107. 
Moreover as was referred above, the intensity of the light emitted from the 
SLM 115 changes in response to the change of the intensity of the image 
light entering through the write side. Namely, light emitted from the SLM 
having a required intensity can be obtained by controlling the intensity 
of the image light entering through the write side. 
The light emitted from the SLM 115 is converted into converged light by the 
lens 113, and then reflected by the half-mirror 111. After passing through 
lenses 124 and 125 and a pinhole 127, the light impinges on photographic 
paper 129. 
Hereinafter, the image pattern which is to be combined with the image of 
the negative film 107 will be described with reference to FIGS. 3(a), 
3(b), 3(c) and 3(d). 
When a frame image is to be combined with the image of the negative film 
107 shown in FIG. 3(a), a pattern is formed as shown in FIG. 3(b) so that 
the image light is allowed to enter the SLM 115 except for a frame area 
(dotted area in the figure) thereof to be blocked. 
According to this configuration, the image light incident on the 
photoconductive film 209 of the SLM 115 is of restricted to an area out of 
the frame area. Therefore, the impedance of the portion of the 
photoconductive film 209 corresponding to the frame area is not lowered so 
that an electric field is not generated at the portion of the liquid 
crystal 219 corresponding to the frame area. 
Accordingly, the portion of the liquid crystal 219 corresponding to the 
frame area remains to be in the scattering state. Among the image light 
from the negative film 107 which has entered through the read side, 
therefore, only the image light corresponding to the area out of the frame 
area is allowed to be emitted from the SLM 115. As a result, the 
photographic paper 129 is exposed to the image light in which the blank 
space frame is combined with the image of the negative film 107 as shown 
in FIG. 3(c). 
When a character image is to be combined with the image of the negative 
film 107, a pattern is formed as shown in FIG. 3(d) so that the write side 
light except for the character area to be blocked is allowed to enter the 
SLM 115. 
According to this configuration, the image light incident on the 
photoconductive film 209 of the SLM 115 is of restricted to an area out of 
the character area. Therefore, the impedance of the portion of the 
photoconductive film 209 corresponding to the character area is not 
lowered so that an electric field is not generated at the portion of the 
liquid crystal 219 corresponding to the character area. 
Accordingly, the portion of the liquid crystal 219 corresponding to the 
character area remains to be in the scattering state. Among the image 
light from the negative film 107 which has entered through the read side, 
therefore, only the image light corresponding to the area out of the 
character area is allowed to be emitted from the SLM 115. As a result, the 
photographic paper 129 is exposed to the image light in which the void 
character is combined with the image of the negative film 107. 
On the other hand, in stead of the pattern mask 123 and the light source 
117, an EL panel in which horizontal and vertical electrodes are arranged 
in a matrix form, or a CRT may be used. In this case, an image including a 
frame, a graphic, characters or the like is luminously displayed on the EL 
panel or the CRT. Additionally, such an image may be displayed on a liquid 
crystal display device. 
Particularly in the case where an EL panel is used, it is possible to 
obtain a high definition image because an EL panel is not provided with a 
black matrix which is inevitably employed in a liquid crystal display 
device. 
Another negative film may be used in place of the pattern mask 123 so that 
images of different negative films are combined with each other. 
According to the embodiment described above, image information of a 
negative film and that of a pattern mask or the like are introduced into 
the SLM, and therefore the image information of the negative film can be 
modulated in such a manner that the image of the pattern mask or the like 
is combined with that of the negative film. This allows an image of a 
negative film to be easily combined with another image. 
The SLM can emit image information without dividing the image information 
into pixels. Therefore, it is possible to expose photographic paper to a 
high definition image. 
Moreover, the intensity of light emitted from the SLM can be changed by 
controlling the intensity of light incident on the write side of the SLM, 
thereby allowing photographic paper to be exposed to light of a desired 
intensity. 
[Second Embodiment] 
Hereinafter, second embodiment of the invention will be described with 
reference to the drawings. 
FIG. 4 shows a structural view of an image exposure apparatus of the second 
embodiment of the invention. Light from a light source 301 is reflected by 
a reflector 303 to enter a negative film 307 through a lens 305. The light 
which has been transmitted through the negative film 307 is split by a 
half-mirror 311. One of the split beams directly enters a read side of an 
SLM 309 (the read side in which the glass substrate 203 is disposed). 
Hereupon, although in FIG. 4 the incident angle to the SLM 309 is not 
perpendicular for convenience' sake, preferably the incident angle is near 
by 90.degree.. The other split beam passes through an optical path 
consisting of a lens 313, a mirror 315, a lens 317, a mirror 319, a lens 
321, and a mirror 323, and then enters a write side of the SLM 309 (the 
side in which the glass substrate 201 is disposed). 
Since the SLM 309 has a similar construction to the SLM 115 described with 
reference to FIG. 2, similar elements are identified by same numerical 
references. And then a driving voltage for the transparent electrodes 205 
and 207 of the SLM 309 is supplied by a driving unit 349 shown in FIG. 4. 
Next, the operation of the SLM 309 of this embodiment will be described. 
When light enters the write side of the SLM 309, the impedance of the 
photoconductive film 209 is lowered according as that the intensity of the 
entering light is increased, and the liquid crystal 219 is effected from 
an electric field generated corresponding to the light intensity 
distribution. The liquid crystal 219 in the area to which the electric 
field is effected produces an electrooptic effect so that light entering 
through the read side is modulated. 
As shown in FIG. 4, the image light from the negative film 307 enters both 
the write and read sides of the SLM 309. 
When the photoconductive film 209 constituting the SLM 309 is irradiated 
with the image light which has been transmitted through the negative film 
307, the impedance of the irradiated portion of the photoconductive film 
209 is lowered according as that the light intensity increases, and an 
electric field corresponding to the light intensity distribution is 
generated to effect to the portion of the liquid crystal 219 corresponding 
to the irradiated portion. As a result, the alignment of the liquid 
crystal 219 to change in accordance with the brightness pattern of the 
image of the negative film 307, so that the image light which has been 
transmitted through the negative film 307 is modulated by the liquid 
crystal 219 and then emitted from the SLM. 
The light which is emitted from the read side in this way corresponds to 
the brightness pattern of the image of the negative film 307, and impinges 
on photographic paper 327 through a lens 325. 
The exposure of the image of the negative film 307 is conducted in this 
way. As described above, however, it is required to effectively keep the 
image of the negative film 307 within the density latitude of the 
photographic paper 327. 
In the case where a portrait is taken with a bright background, for 
example, the brightness difference between the background and the person 
is large, and the density difference of the image of the negative film is 
therefore large. When photographic paper is exposed to such image light 
from the negative film, there are occasions where the image light exceeds 
the density latitude which can be expressed by the photographic paper. In 
such occasions, even if the exposure value is adjusted, available prints 
are only those in which the skin color of the person is uniformly obscured 
and the background is made white. 
In the case where a portrait is taken with a dark background, the 
brightness difference between the background and the person is small, and 
therefore the density difference of the image of the negative film is 
small. When photographic paper is exposed to such image light of the 
negative film, the image obtained uses a narrow range of the density 
latitude which can be expressed by the photographic paper, resulting in 
that a print without modulation is obtained. 
In the above both photographs, therefore, exposure must be conducted while 
correcting the contrast of the image of the negative film so that the 
image becomes low contrast or high contrast, or effectively using the 
density latitude of the photographic paper. On the contrary, depending on 
the intention of the photographer, there are occasions where a print 
having contrast which is designedly emphasized or suppressed is desired. 
The intensity of light with which the photographic paper 327 is irradiated 
can be controlled by the SLM 309. The intensity of light emitted from the 
SLM 309 corresponds to the intensity distribution of the image light 
entering through the write side. The contrast of the image to which the 
photographic paper 327 is exposed can be corrected by changing the 
response characteristic of the SLM 309 with respect to the light 
intensity. 
Specifically, in the liquid crystal constituting the SLM 309, the 
transmittance of the portion corresponding to the lower intensity portion 
of light entering the write side is lowered so that the intensity of the 
emitted light decreases. An image obtained as a result of the exposure 
using this emitted light has suppressed contrast. In other words, the 
image has low contrast. 
Alternatively, in the liquid crystal constituting the SLM 309, the 
transmittance of the portion corresponding to the high intensity portion 
of light entering the write side is increased so that the intensity of the 
emitted light increases. An image obtained as a result of the exposure 
using this emitted light has emphasized contrast. In other words, the 
image has high contrast. 
The degree of the contrast correction is determined by the characteristics 
of the SLM 309, for example, the characteristics of the photoconductive 
film and the liquid crystal, and the applied driving voltage. 
Returning to FIG. 4, the contrast correction will be described. 
The light emitted from the SLM 309 is split by a half-mirror 329. One of 
the split beams enters an image area sensor 333 through a lens 331. 
The image area sensor 333 outputs an image signal to a monitor image 
processing unit 335, and a photometric signal which is obtained by 
measuring the emitted light, to a characteristic value calculating unit 
337. 
The monitor image processing unit 335 conducts the processes of 
negative/positive conversion, gradation correction, saturation correction, 
etc., and controls a CRT (cathode ray tube) 339 so as to display an image 
obtained by simulating the finished state of a print. Correction data are 
input though a keyboard 345 connected to a controller 343 which will be 
described later. The input correction data are displayed on a display 
device 347 connected to the controller 343. 
The characteristic value calculating unit 337 calculates various 
characteristic values such as the density difference between a high light 
portion and a shadow portion of an image, and an average picture density, 
and outputs the calculation results to an exposure value calculating unit 
341. 
From the calculation results of the characteristic value calculating unit 
337, and, if necessary, the correction data input through the keyboard 
345, the exposure value calculating unit 341 calculates a required 
exposure value which is set by an exposure light intensity and an exposure 
time on the basis of an exposure value calculation formula, and a picture 
density difference. The calculation results are supplied to the controller 
343. 
The relationship between the picture density difference, the driving 
voltage, and the exposure time which is required to reproduce the image of 
the negative film 307 with the latitude of the photographic paper is 
previously stored in a memory of the controller 343. The driving voltage 
and the exposure time are determined on the basis of the calculation 
results with reference to the memory, whereby the required exposure value 
is determined. 
The controller 343 outputs a control signal to the driving unit 349 so that 
the driving unit 349 applies the determined driving voltage to the SLM 309 
for a predetermined time. 
The SLM 309 is operated by the determined driving voltage for the 
determined time, thereby supplying the photographic paper with the 
required exposure value. 
The relationship between the density difference of the image of the 
negative film 307 and the exposure value is determined, for example, in 
such a manner that, when the density difference is large, the exposure 
value is reduced so that the contrast of the image is suppressed, and, 
when the density difference is small, the exposure value is increased so 
that the contrast of the image is emphasized. 
When contrast is to be corrected more finely, detected bright and dark 
positions and bright and dark regions are considered. When the brightest 
or darkest portion is detected in an edge area of the picture, or when the 
minute brightest or darkest portion is detected in the center area of the 
picture, for example, this brightest or darkest portion is neglected. This 
allows the contrast correction to be conducted in consideration of the 
visual characteristics. 
In the embodiment described above, the image light from the negative film 
307 enters the read side of the SLM 309. Alternatively, uniform light 
having no image information may enter the read side of the SLM, the 
intensity of the light may be modulated, and then the light may be 
emitted. In this case, when the light is passed through the SLM, the color 
information is eliminated. Therefore, it is necessary to write light which 
has undergone the three-color separation into the SLM, and read from the 
SLM the modulated color information with the use of light of the same 
color. 
According to the second embodiment of the invention described above, the 
exposure value supplied to photographic paper is controlled in accordance 
with the density distribution of an image of a negative film, and an image 
of adequate contrast can be reproduced with effectively using the density 
latitude of the photographic paper. 
The SLM which controls the exposure value can modulate the intensity of 
light entering through the read side, in accordance with the intensity of 
light entering through the write side, and then output the modulated 
light, without dividing the image information into regions. According to 
the invention, therefore, the light control can be conducted image-wise 
and it is possible to expose photographic paper to a high definition 
image. 
Since the SLM is not required to be divided into regions which are 
independently driven, the calculation of the driving voltage which is 
supplied to the SLM can be simplified.