Projecting apparatus

A projecting apparatus comprises support device for supporting an original, a projection optical system for forming the image of the original, an optical element disposed on the image side of the projection optical system to cause a principal light ray having entered from the original through the projection optical system to travel in parallelism to the optic axis of the projection optical system, and control device for varying the imaging magnification of the original by the projection optical system with the spacing between the exit pupil of the projection optical system and the optical element being kept constant.

BACKGROUND AND SUMMARY OF THE INVENTION 
This invention relates to an apparatus for projecting an original such as a 
negative film or a positive film, and in particular to a projecting 
apparatus which enables an original to be read with the imaging 
magnification thereof varied, in addition to the ordinary reading of the 
original in a facsimile apparatus, a copying apparatus or the like. 
When an original picture such as a microfilm or a 35 mm film is to be read 
by an image pickup device such as a CCD and an enlarged image of the 
original picture is to be formed, it has heretofore been possible to 
obtain the enlarged image by reading the original picture at one-to-one 
magnification and electrically interpolating the resulting image signal. 
According to this method, however, the number of picture elements is small 
and therefore, the image becomes rough and an image of high accuracy 
cannot be obtained. 
In order to overcome such a disadvantage, the applicant has already 
proposed in Japanese Laid-open Patent Application No. 52819/1985 an 
apparatus for forming an enlarged image of an original picture by using a 
projecting apparatus, and then reading the enlarged image by an image 
pickup device such as a CCD. FIG. 1 of the accompanying drawings shows 
this proposed reading apparatus. 
In FIG. 1, an original picture 1 such as a film illuminated by an 
illuminating system, not shown, is enlarged and projected by a projection 
lens 2. A Fresnel lens 3 is disposed on the plane of the image projected 
by the projection lens 2. The focus of this Fresnel lens 3 is aligned to 
the position of the exit pupil of the projection lens 2 and therefore, the 
light having left the Fresnel lens 3 is made parallel to the optic axis of 
the projection lens 2 and passes through an original supporting glass 
plate 4. The light passed through the original supporting glass plate 4 is 
imaged on a solid state image pickup device 6 by an imaging lens 5. The 
imaging lens 5 and the solid state image pickup device 6 together 
constitute a head 7, which may be moved in the direction of arrow 8 to 
read the entire projected image. 
In such a reading apparatus, it is desirable that a reproduced image of a 
desired size of the original be obtained and accordingly, the projection 
optical system is required to have various imaging magnifications. 
It is an object of the present invention to provide a projecting apparatus 
in which any variation in the imaging magnification of the reproduced 
image of an original picture does not affect the characteristic of an 
optical system for reading the reproduced image. 
It is a further object of the present invention to provide a projecting 
apparatus simply mountable on an apparatus capable of reading the optical 
image from an original on an original supporting table. 
To achieve these objects, the projecting apparatus according to the present 
invention comprises: 
means for supporting an original picture; 
a projection optical system for forming the image of the original picture; 
an optical element disposed on the image side of said projection optical 
system to cause a principal light ray having entered from the original 
picture through the projection optical system to travel in parallel to the 
optic axis of said projection optical system; and 
control means for varying the imaging magnification of the original picture 
by said projection optical system with the spacing between the exit pupil 
of said projection optical system and said optical element being kept 
constant.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
An example in which an embodiment of the projecting apparatus according to 
the present invention is mounted on a reading apparatus will hereinafter 
be described with reference to FIG. 2. Reference numeral 11 designates a 
reading apparatus body containing a reading optical system 12, etc. 
therein, and reference numeral 13 denotes a projecting apparatus for 
projecting a photographic film or the like. When a reflective original is 
to be read by the reading apparatus 11, the projecting apparatus is 
detached from the reading apparatus, and an original (not shown) is placed 
on an original supporting table 14 and is illuminated by an illuminating 
lamp 15. In FIG. 2, description will be made of an example in which a 
telecentric optical system is used as a reading optical system 12. The 
principal light ray from the original on the original supporting table 14 
travels parallel to the optic axis of an imaging lens 16, passes through a 
stop 17 lying at the focus position of the imaging lens 16 and reaches a 
solid state image pickup device 18 such as a CCD. Thus, the optical image 
of the original is formed on the solid state image pickup device 18. The 
reading optical system 12 is moved for primary scanning on rails 19 and 
19' in a direction perpendicular to the plane of the drawing sheet, and 
reads the original with a width corresponding to the number of elements of 
the solid state image pickup device 18. After this reciprocal movement in 
the primary scanning direction, the reading optical system 12, together 
with the lamp 15, is moved in the subsidiary scanning direction (the 
direction of arrow A) by the width read in the one reciprocal movement in 
the primary scanning direction, and then again starts the next primary 
scanning. By the primary scanning and the subsidiary scanning being 
repeated in this manner, the entire area of the original on the original 
supporting table 14 is read. Description will now be made of a case where 
the projected image from a film can be read simply by placing the 
projecting apparatus 13 instead of the reflective original onto the 
original supporting table 14. Reference numeral 20 designates an original 
picture having transmittable images thereon, such as a negative film or a 
positive film, and reference numeral 21 denotes a projecting zoom lens for 
projecting the original picture 20 while changing the magnification 
thereof. Reference numeral 22 designates a Fresnel lens as a field lens. 
The relation between the optical systems of the projecting apparatus 13 
and the reading apparatus will now be described with reference to FIG. 3. 
In FIG. 3, the portion constituted by the projection lens 21 and the field 
lens 22 is the optical system of the projecting apparatus 13, and the 
portion constituted by the imaging lens 16, the stop 17 and the solid 
state image pickup device 18 is the reading optical system 12. The field 
lens 22 lies near the imaging position of the projection lens 21, and 
moreover has its focus in the exit pupil of the projection lens 21. If 
such a construction is adopted, the principal light rays of the optical 
image from the original picture 20 are enlarged through the projection 
lens 21 as indicated by dot and-dash lines, are caused to travel in a 
direction perpendicular to the original supporting table 14, i.e., in 
parallelism to the optic axis of the imaging lens 16, by the field lens 
22, and enter the imaging lens 16. In this manner, these principal light 
rays, together with the light beam in the vicinity thereof, are converged 
and imaged on the solid state image pickup device 18 through the stop 17 
lying at the focus position of the lens 16. 
The projecting apparatus of the present invention can make the 
magnification of the projected image variable, and the relation diagram 
thereof is shown in FIG. 4. In FIG. 4, reference numerals 20-1 and 20-2 
designate the positions of the film surface which is the original picture 
corresponding to the changed magnifications, reference numeral 21 denotes 
the projecting zoom lens, and reference numeral 22 designates the field 
lens. The field lens 22 has its focus at the position of the exit pupil of 
the projecting zoom lens 21 and therefore, the spacing b between the exit 
pupil and the field lens 22 is constant. Also, the projecting zoom lens 21 
varies the focal length f to 
##EQU1## 
in accordance with the changed magnification n while keeping the exit 
pupil position at the focus position of the field lens 22. At this time, 
the spacing a between the film surface 20-1 and the projecting zoom lens 
21 is changed to 
##EQU2## 
With such a construction, a projected light C is obtained when the changed 
magnification 
##EQU3## 
and a projected light C' is obtained when the changed magnification 
##EQU4## 
. 
Depending on the design of the zoom lens 21, a magnification change can be 
accomplished while the relative position of the original picture 20 to the 
image of the original picture is kept fixed AND the position of the exit 
pupil is kept fixed. 
That is, in order that a magnification change may be accomplished while the 
position of the exit pupil of the projection optical system such as the 
projecting zoom lens 21 and the position of the image of the original 
picture 20 are kept fixed, the combination of the position of a stop 21' 
(FIG. 2) in the projection optical system and the spacing between the 
original picture 20 and the projection optical system is suitably varied. 
As the control means for this purpose, there are the control device 21" of 
the stop 21' and a device which will hereinafter be described with 
reference to FIG. 2. 
Turning back to FIG. 2, an embodiment of the present invention will 
hereinafter be described in greater detail. 
Reference numeral 23 designates an illuminating light source disposed 
rearwardly of the original picture 20, reference numeral 24 denotes an 
illuminating lamp, reference numeral 25 designates a reflector, reference 
numeral 26 denotes a light diffusing and reflecting plate, and reference 
numeral 27 designates a diffusing and transmitting plate for diffusing the 
light from the illuminating lamp 24 and the reflector 25 and for rendering 
uniform the distribution of light onto the film surface. The focal length 
of the projecting zoom lens 21 is varied by rotating a gear 31 mounted on 
a lens moving barrel 30, by the revolution of a motor 28 through a gear 
29. Reference numeral 32 designates a rack for moving a film supporting 
bed 40 and the illuminating light source 23 at a time. This rack 32 is 
moved up and down by a pinion 33 rotated by a motor (not shown) involving 
at the same time as the revolution of the motor 28 for the zoom lens in 
accordance with a changed magnification, thereby varying the spacing 
between the projection lens 21 and the original picture 20 in accordance 
with the changed magnification. Reference numeral 34 denotes 
light-intercepting bellows, and reference numeral 36 designates the 
housing of the projecting apparatus for supporting a rail 35 on which the 
rack 32 slides, the projecting zoom lens moving barrel 30, the motor 28, 
etc. and intercepting the extraneous light. For the fluctuation of the 
quantity of light during the magnification change of the zoom-lens 21, the 
quantity of light on the imaging surface (the surface of the field lens 
22) can always be made constant by coping with said fluctuation by the 
variation in the size of the stop 21' in the lens by a control device 21" 
or the variation in the quantity of light of the lamp 24 by a control 
device 24'. 
The reading signal read from the solid state image pickup device 17 is 
subjected to suitable signal processing, whereafter it is outputted by an 
electrophotographic type laser beam printer, an ink jet printer, a 
thermosensitive printer or the like and is made into a hard copy, or is 
displayed by a display device such as a cathode ray tube or a liquid 
crystal display plate or is transmitted. In the present invention, an 
in-plane index distribution type planar lens of the same construction as 
an arrangement in which a number of minute lenses are arranged in the form 
of a matrix array may be used instead of the Fresnel lens. In the 
foregoing description, the scanning optical system has been 
two-dimensionally moved and scanned, but alternatively, the original 
picture or the original supporting table may be one-dimensionally moved in 
one of the subsidiary scanning direction and the primary scanning 
direction and the scanning optical system may be one-dimensionally moved 
in the other scanning direction, whereby the original picture or the like 
may be read. 
Also, a full-color original may be read as by disposing three rows of solid 
state image pickup device in the primary scanning direction and providing 
a three-color resolving filter and color image signals may be put out. In 
this case, for the correction of the colors of a negative film, a color 
correcting film may be provided in a portion of the optical path of the 
projecting apparatus as required. 
As described above in detail, the present invention can read the images of 
the original and the original picture faithfully to these images and 
therefore, when these images are reproduced, there can be formed a 
beautiful image free of strain. 
Further, any changed magnification can be freely selected from an original 
of a small size and a projected picture of a large format can be obtained 
and therefore, an image of high accuracy can be formed.