Patent Publication Number: US-6219491-B1

Title: Electro-developing type camera

Description:
This is a division of U.S. patent application Ser. No. 08/658,628, filed Jun. 5, 1996, the contents of which are herein incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a camera using a so-called electro-developing recording medium, in which an image obtained by exposing the recording medium is electronically developed. 
     2. Description of the Related Art 
     Conventionally, there is known a photographic material which electronically develops an optical image formed thereon through a photographing lens. U.S. Pat. No. 5,424,156 (corresponding to Japanese Unexamined Patent Publication No. 5-2280), for example, discloses a recording medium which is a combination of an electrostatic information recording medium and an electric charge keeping medium. In this specification, such a recording medium is referred to as an electro-developing recording medium, and a camera using the electro-developing recording medium is referred to as an electro-developing type camera. 
     In the electro-developing recording medium disclosed in the above publication, the electrostatic information recording medium has a photoconducting layer and an inorganic oxide material layer, and the electric charge keeping medium has a liquid crystal display. In this structure, when the electrostatic information recording medium is exposed while an electric voltage is applied to the electrostatic information recording medium and the electric charge keeping medium, electric charge in accordance with the amount of incident light is generated in the electrostatic information recording medium. Since the intensity of the electric field applied to the liquid crystal display facing the electrostatic information recording medium is varied in accordance with the generated electric charge, an image corresponding to the amount of light distribution is indicated or developed on the liquid crystal display. 
     The image developed on the liquid crystal display can be sensed by using an optical element such as a line sensor. Namely, a front surface of the electro-developing recording medium is illuminated by light, and the light passing through the recording medium is sensed by the line sensor which scans along the rear surface of the recording medium, so that the image can be read out from the line sensor. 
     If the electro-developing type camera is constructed in such a manner that, in addition to the photographing operation, the image can be read out from the electro-developing recording medium, then a member such as an illumination light source needs to be disposed between the photographing optical system and the electro-developing recording medium. This structure causes difficulty in reducing the axial size of the photographing optical system, so that a design restriction occurs. 
     SUMMARY OF THE INVENTION 
     Therefore, an object of the present invention is to provide an electro-developing type camera in which a developing operation and a reading operation can be performed, and the axial size of the photographing optical system can be reduced. 
     According to the present invention, there is provided an electro-developing type camera comprising an electro-developing recording medium, scanning means, and moving means. 
     The electro-developing recording medium has a recording area which electronically develops an image formed thereon, and can move along a surface thereof. The scanning means scans the electro-developing recording medium so that the image formed on the electro-developing recording medium is read out. The moving means moves the electro-developing recording medium in such a manner that, when the image is developed, the electro-developing recording medium is positioned at a first position, and when the image developed on the electro-developing recording medium is read out by the scanning means, the electro-developing recording medium is positioned at a second position which is different from the first position. 
     Further, according to the present invention, there is provided an electro-developing type camera comprising an electro-developing recording medium, scanning means, a color filter and control means. 
     The electro-developing recording medium electronically develops an image formed thereon. The scanning means scans the electro-developing recording medium so that the image is read out. The color filter has color filter elements and a reading area having spectral characteristics different from the color filter elements. The color filter faces the electro-developing recording medium. The control means controls a position of the color filter. The control means positions the reading area to face the electro-developing recording medium when the scanning means scans the electro-developing recording medium. 
     Furthermore, according to the present invention, there is provided an electro-developing type camera comprising an electron developing recording medium, scanning means, a color filter, a light source and control means. 
     The electro-developing recording medium electronically develops an image formed thereon. The scanning means scans the electro-developing recording medium so that the image is read out. The color filter has three primary color filter elements. The color filter faces the electro-developing recording medium. The light source emits light having a predetermined wavelength distribution onto the electro-developing recording medium through the color filter so that the scanning means scans the electro-developing recording medium. The control means controls a position of the color filter. The control means controls the reading area to face a predetermined color filter element included in the primary color filter elements, when the scanning means scans the electro-developing recording medium. The predetermined color filter element has a spectral characteristic such that substantially all light emitted from the light source passes therethrough. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The objects and advantages of the present invention will be better understood from the following description, with reference to the accompanying drawings in which: 
     FIG. 1 is an external view showing a still video camera to which first through third embodiments according to the present invention are applied; 
     FIG. 2 is a block diagram of the still video camera of the first embodiment; 
     FIG. 3 is a perspective view showing a scanning mechanism and members provided close thereto in the first embodiment; 
     FIG. 4 is a sectional view showing a structure of an electro-developing recording medium; 
     FIG. 5 is a timing chart showing a photographing operation of an image signal of the first embodiment; 
     FIG. 6 is a block diagram of the still video camera of the second and third embodiments; 
     FIG. 7 is a perspective view showing a scanning mechanism and members provided close thereto in the second embodiment. 
     FIG. 8 is a view showing a color separation filter provided in the second embodiment; 
     FIG. 9 is a diagram showing spectral characteristics of each of the filter elements of the second embodiment; 
     FIG. 10 is a timing chart showing a photographing operation of an image signal of the second embodiment; 
     FIG. 11 is a view showing a color separation filter provided in the third embodiment; 
     FIG. 12 is a diagram showing spectral characteristics of each of the filter elements of the third embodiment; and 
     FIG. 13 is a timing chart showing a photographing operation of an image signal of the third embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is an external view of a still video camera to which a first embodiment of the present invention is applied. This still video camera is an electro-developing type camera, which is constructed in such a manner that an image is developed by an electro-developing recording medium. 
     When viewing the camera body  11  from a front side, on the front surface of the camera body  11 , a photographing optical system  12  including a photographing lens and so on is provided on approximately the central portion of the front surface, and an electronic flash  13  is disposed on a portion to the right of and above the photographing optical system  12 . A release switch  14  is provided on the side of the optical system  12  opposite to the electronic flash  13 . On the upper surface of the camera body  11 , a view finder  15  is provided at the center portion thereof, and operation switches including a scan start switch  16  are provided on a side of the view finder  15 . On a side surface of the camera body  11 , an output terminal  17  is formed on a lower portion thereof so that an image signal obtained by this camera can be outputted to an external recording device. 
     FIG. 2 is a block diagram of the still video camera. A system control circuit  20  including a micro-computer is mounted to control the still video camera as a whole. 
     The photographing optical system  12  has a plurality of lens groups and an aperture  12   a . A color separation filter  80  and an electro-developing recording medium  30  are disposed behind the photographing optical system  12 , and the color separation filter  80  is positioned closer to the photographing optical system  12  in comparison with the electro-developing recording medium  30 . A quick return mirror  21  is placed between the photographing optical system  12  and the color separation filter  80 . A focusing glass  23   a , included in a view-finder optical system  23 , is disposed above the quick return mirror  21 . A shutter  22  is e provided between the color separation filter  80  and the electro-developing recording medium  30 . 
     The aperture  12   a , the quick return mirror  21  and the shutter  22  are driven by an iris drive circuit  24 , a mirror drive circuit  25  and a shutter drive circuit  26 , respectively, which are controlled by an exposure control circuit  27 . 
     The exposure control circuit  27  is operated in accordance with a command signal outputted by the system control circuit  20 . Namely, when an exposure is controlled, the opening degree of the aperture  12   a  is adjusted by the iris drive circuit  24 , under control of the exposure control circuit  27 , based on an output signal of the photometry sensor  28 . 
     The quick return mirror  21  is usually set to a down position (an inclining position shown by the solid lines in the drawing), so that a light beam passing through the photographing optical system  12  is led to the view-finder optical system  23 . Thus, an object to be photographed can be observed by the photographer. When a photographing operation is carried out, the quick return mirror  21  is rotated upward by the mirror drive circuit  25  and set to an up position (a horizontal position shown by the broken lines in the drawing), so that the light beam is led to the electro-developing recording medium  30 . 
     The shutter  22  is usually closed, and upon a photographing operation, the shutter  22  is opened for a predetermined period by the shutter drive circuit  26  under control of the exposure control circuit  27 . Thus, the light beam passing through the photographing optical system  12  enters light receiving surface of the electro-developing recording medium  30 . 
     The color separation filter  80  and the electro-developing recording medium  30  are disks and are coaxially disposed. A stepping motor  90  has shafts  91  and  92 , which are extended in opposite directions to each other and are connected to central portions of the color separation filter  80  and the electro-developing recording medium  30 , respectively. Namely, the color separation filter  80  and the electro-developing recording medium  30  are rotatable about the center axes thereof, and are rotated in synchronization with each other. The stepping motor  90  is driven by a motor drive circuit  93  based on an output signal of the exposure control circuit  27 , and is rotated approximately 120 degrees at every operation in which the shutter  22  is opened and closed. 
     An electric voltage is applied to the electro-developing recording medium  30  under control of a recording medium drive circuit  41 . By exposing the electro-developing recording medium while applying the voltage, an image formed by the photographing optical system  12  is electronically developed on the electro-developing recording medium  30  as a visible image. Note that the recording medium drive circuit  41  is operated in accordance with a command signal outputted by the system control circuit  20 . 
     A scanning mechanism  50  is provided close to the electro-developing recording medium  30 . The shutter  22  is disposed at a first position above the stepping motor  90  while the scanning mechanism  50  is positioned at a second position lower than the stepping motor  90 . Namely, the scanning mechanism  50  and the shutter  22  are positioned opposite to each other with respect to the center axes of the color separation filter  80  and the electro-developing recording medium  30 . In other words, the first and second positions are symmetrical about the center axis, and the first position corresponds to the optical axis of the photographing optical system  12  while the second position is offset from the optical axis. 
     A light source  42 , including an LED (light emitting diode), for example, a scanner optical system  43  and a line sensor  44  are supported by the scanning mechanism  50 , and are moved along the electro-developing recording medium  30  by a scanning operation of the scanning mechanism  50 . 
     The light source  42  outputs light having a spectral distribution which is suitable for a reading operation in which an image formed on the electro-developing recording medium  30  is read out therefrom. 
     The line sensor  44  may be a one dimensional CCD sensor of 2000 pixels, for example. The light source  42  can be moved along the front surface of the electro-developing recording medium  30 , and the line sensor  44  can be moved along the rear surface of the electro-developing recording medium  30 . The scanner optical system  43  is disposed between the light source  42  and the line sensor  44 . When a scanning is carried out by the scanning mechanism  50 , the light source  42  is positioned in front of the electro-developing recording medium  30  and opposite to the line sensor  44  relative to the electro-developing recording medium  30 , so that the image developed by the electro-developing recording medium  30  is illuminated by the light source  42  and formed on the light receiving surface of the line sensor  44 , due to an operation of the scanner optical system  43 . Namely, the scanner optical system  43  is disposed on the optical path of the light beam which passes through the electro-developing recording medium  30 , and the line sensor  44  is moved in an imaging plane, on which an image is formed, by the scanner optical system  43 . 
     ON-OFF control of the light source  42  is performed by a light source drive circuit  45 . Control of the reading operation of the pixel signal generated in the line sensor  44  is carried out by a line sensor drive circuit  46 . Control of the movement of the scanning mechanism  50  is performed by a scanner drive circuit  46 . The circuits  45 ,  46  and  47  are controlled by the system control circuit  20 . 
     A pixel signal read out from the line sensor  44  is amplified by an amplifier  61 , and converted to a digital signal by an A/D converter  62 . 
     The digital pixel signal is subjected to a shading correction, a gamma correction, and so on by an image processing circuit  63  under control of the system control circuit  20 , and then, is temporarily stored in a memory  64 . The memory includes t an EEPROM in which correction data for the shading correction is stored. Note that the memory  64  may have a storage capacity equal to one horizontal scanning line outputted from the line sensor  44 , or it may have a storage capacity of one frame&#39;s worth of image signals. 
     The pixel signal outputted from the memory  64  is inputted into an interface circuit  65 , through the image processing circuit  63 , so that the pixel signal is subjected to a predetermined process such as a format conversion, and can be outputted to an external display device (not shown) through the output terminal  17 . The pixel signal outputted from the image processing circuit  63  is subjected to a predetermined process, such as an image compression and a format conversion, in a recording device control circuit  66 , so that the pixel signal can be recorded on a recording medium such as an IC memory card, for example, in an image recording device  67 . The interface circuit  65  and the recording device control circuit  66  are operated in accordance with a command signal outputted from the system control circuit  20 . 
     An operation unit  71 , including the release switch  14  and the scan start switch  16 , is connected to the system control circuit  20 . A photographing operation is performed by the operation of the release switch  14 . A reading operation by which an image signal is read from the electro-developing recording medium  30  is performed in accordance with the operation of the scan start switch  16 . 
     Further, a display device  68  and an electronic flash drive circuit  69  are connected to the system control circuit  20 . The display device is provided for indicating various setting conditions of the still video camera. The electronic flash drive circuit  69  is provided for controlling the electronic flash  13  so that the electronic flash  13  radiates a flash of light. 
     FIG. 3 shows the scanning mechanism  50  and a construction provided close thereto. 
     A moving member  52  of the scanning mechanism  50  is slidably supported by a guide shaft  51 , and has first and second leg portions  52   a  and  52   b  and a support portion  52   c . The first leg portion  52   a  is extended between the color separation filter  80  and the electro-developing recording medium  30 , and under the stepping motor  90 . The second leg portion  52   b  is extended along a rear surface of the electro-developing recording medium  30 . The support portion  52   c  is provided behind the second leg portion  52   b.    
     The light source  42  is mounted on the first leg portion  52   a , so that an illumination light beam radiated from the light source  42  is irradiated onto the electro-developing recording medium  30  through a collimator lens (not shown) attached to the first leg portion  52   a . The scanner optical system  43  and the line sensor  44  are provided on the second leg portion  52   b  and the support portion  52   c , respectively. Each of the light source  42  and the line sensor  44  is extended in a horizontal direction. 
     A rack  53  is provided on a side surface of the moving member  52 . The rack  53  meshed with a pinion gear  54 , which meshes with a gear fixed on an output shaft of a scan drive motor  55 . 
     The electro-developing recording medium  30  has a first recording area  30 R on which a red (R) image is formed, a second recording area  30 G on which a green (G) image is formed, and a third recording area  30 B on which a blue (B) image is formed. Each of these recording areas  30 R,  30 G and  30 B is rectangular, faces the shutter  22  when positioned at the first position which is located above the output shaft  92 , and faces the light source  42  and the scanner optical system  43  when positioned at the second position which is located under the output shaft  92 . 
     The color separation filter  80  is divided into an R filter element  80 R, a G filter element  80 G and a blue filter element  80 B by three straight lines radially extending from the axis of the color separation filter  80 . Each of these filter elements  80 R,  80 G and  80 B has a fan-shape the center angle of which is 120 degrees. A mask  95  for blocking light is formed on a portion which is located at an outermost portion of the color separation filter  80 , and on the dividing line between the R filter element  80 R and the B filter element  80 B. An original point sensor  94 , which is a photo-interrupter, is provided on a portion facing a peripheral portion of the color separation filter  80 . 
     When a photographing operation is performed, the color separation filter  80  is positioned in such a manner that one of the filter elements  80 R,  80 G or  80 B is positioned behind the photographing optical system  12 , namely on the photographing optical axis, and the electro-developing recording medium  30  is positioned in such a manner that one of the recording areas  30 R,  30 G or  30 B, corresponding to the filter element, is positioned on the photographing optical axis. Each of the color separation filter  80  and the electro-developing recording medium  30  is rotated by one revolution, while one frame image is photographed. Namely, an R image is developed on the first recording area  30 R, a G image is developed on the second recording area  30 G and a B image is developed on the third recording area  30 B. 
     After completing the photographing operation, if the scan start switch  16  is operated, the scan drive motor  55  is driven so that the moving member  52  is moved upward. Thus, a scanning operation of the line sensor  44  is performed, so that the line sensor  44  is moved in a direction perpendicular to the longitudinal direction thereof. The scanning operation is carried out for each of the recording areas  30 R,  30 G and  30 B. Namely, the electro-developing recording medium  30  is rotated by one revolution for the scanning operation. 
     FIG. 4 shows a structure of the electro-developing recording medium  30 , and is the same as that shown in Japanese Unexamined Patent Publication No. 5-2280. 
     The electro-developing recording medium  30  has includes an electrostatic information recording medium  31  and an electric charge keeping medium  32 , and an electric voltage is applied thereto by an electric power source  33 . The electrostatic information recording medium  31  is formed by laminating a glass base plate  34 , an electrode layer  35 , an inorganic oxide material layer  36  and a photoconducting layer  37 . The photoconducting layer  37  is formed by laminating an electric charge generating layer  37   a  and an electric charge transferring layer  37   b . The electric charge keeping medium  32  is formed by confining liquid crystal  40 , which is a smectic liquid crystal, between a liquid crystal supporting plate  38  and a liquid crystal electrode layer  39 . The electric charge transferring layer  37   b  of the photoconducting layer  37  and the liquid crystal supporting plate  38  of the electric charge keeping medium  32  face each other with a small gap therebetween. 
     An ON-OFF condition of the electric power source  33  is controlled by the recording medium drive circuit  41  (see FIG.  2 ). When the electric power source  33  is turned ON, an electric voltage is applied between the electrode layer  35  and the liquid crystal electrode layer  39 , i.e., between the electrostatic information recording medium  31  and the electric charge keeping medium  32 . When the electrostatic information recording medium  31  is exposed while the electric voltage is applied, an electric charge is generated in the electrostatic information recording medium  31 , in accordance with an image formed thereon. Since the intensity of the electric field applied to the liquid crystal  40  is changed in accordance with the electric charge, the image is indicated on the liquid crystal  40  as a visible image, and thus, an image of an object is developed. Namely, the visible image is generated in accordance with the electric charge. 
     The electric charge keeping medium  32  is a liquid crystal display having a memory-type liquid crystal such as a smectic liquid crystal. Thus, the developed visible image is kept in the liquid crystal display even if the electric field is removed. In the liquid crystal, the developed visible image can be deleted by heating the liquid crystal, using a heating device (not shown) at a predetermined temperature. Consequently, the same electric charge keeping medium  32  can be used repeatedly. 
     FIG. 5 shows a timing chart of a photographing operation of an image signal onto the electro-developing recording medium  30  and a reading operation of an image signal from the electro-developing recording medium through the line sensor  44 . With reference to the drawing, an operation of the first embodiment will be described. 
     When it is sensed that the release switch  14  has been turned ON (reference S 11 ), an output signal of the photometry sensor  28 , i.e., a photometry value, is sensed, and a photometry calculation is performed based on the photometry value (reference  512 ). Based on the result of the photometry calculation, the opening degree of the aperture  12   a  is changed from the fully open state to a predetermined opening degree (reference S 13 ). Then, the quick return mirror  21  is changed from the down condition to the up-condition (reference S 14 ). 
     When it is confirmed that the quick return mirror  21  has been changed to the up-condition and the opening degree adjustment of the aperture  12   a  has been completed, a recording medium activating signal corresponding to the first recording area  30 R is set to an ON-state (reference S 15 ) so that a voltage is applied to the first recording area  30 R. At the same time, the shutter  22  is opened for an exposure period (reference S 16 ) which is obtained by the photometry calculation (reference S 12 ). 
     Note that, prior to the opening operation of the shutter  22 , the color separation filter  80  has been positioned in such a manner that the R filter element  80 R faces the shutter  22  (reference S 17 ) and the G filter element  80 G and the B filter element BOB are positioned close to the scanning mechanism  50  (reference S 18 ). Regarding the electro-developing recording medium  30 , the first recording area  30 R faces the shutter  22 , and the second and third recording areas  30 G and  30 B are positioned close to the scanning mechanism  50 . Therefore, the R image is formed or developed on the first recording area  30 R. 
     When the shutter  22  is closed, the color separation filter  80  and the electro-developing recording medium  30  are rotated by approximately 120 degrees, so that the G filter element  80 G and the second recording area  30 G are set to the first position to face the shutter  22  (reference S 19 ). The R filter element  80 R, the B filter element  80 B, and the first and third recording areas  30 R and  30 B are set to the second position which is close to the scanning mechanism  50  (reference S 20 ). Under this condition, the recording medium activating signal of the second recording area  30 G is set to the ON condition (reference S 21 ), so that an electric voltage is applied to the second recording area  30 G, and the shutter  22  is opened for the exposure period (reference S 22 ) which is obtained by the photometry calculation. Therefore, the G image is formed or developed on the second recording area  30 G. 
     When the shutter  22  is closed, the color separation filter  80  and the electro-developing recording medium  30  are again rotated by approximately 120 degrees, so that the B filter element  80 B and the third recording area  30 B face the shutter  22  (reference S 23 ). The G filter element  80 G, the R filter element  80 R, and the second and first recording areas  30 G and  30 R are positioned close to the scanning mechanism  50  (reference S 24 ). Under this condition, the recording medium activating signal of the third recording area  30 B is set to the ON condition (reference S 25 ), and the shutter  22  is opened for the exposure period (reference S 26 ) which is obtained by the photometry calculation. Thus, the B image is formed or developed on the third recording area  30 B. 
     When the R, G and B images have been developed by the recording areas  30 R,  30 G and  30 B, the quick return mirror  21  is changed to the down-condition (reference S 27 ) and the aperture  12   a  is driven to the fully open condition (reference S 28 ). 
     When the scan start switch  16  is depressed and a scanner drive command signal is outputted (reference S 31 ), the light source  42  is lit (reference S 32 ). The first recording area  30 R is set to the second position where the first recording area  30 R is close to the scanning mechanism  50  (reference S 33 ), and the second and third recording areas  30 G and  30 B face the shutter  22  (reference S 34 ). Note that, at this time, the R filter  80 R is positioned close to the scanning mechanism  50 , and the G and B filter elements BOG and BOB are positioned close to the shutter  22 . Under this condition, the scanning mechanism  50  is driven, so that a scanning operation of the line sensor  44  is carried out (reference S 35 ), and thus, the R image signal is outputted or read out through the line sensor (reference S 36 ). 
     When the output operation of the R image signal is completed, the electro-developing recording medium  30  and the color separation filter  80  are rotated by approximately 120 degrees, and thus, the second recording area  30 G is positioned close to the scanning mechanism  50  (reference S 37 ) and the first and third recording areas  30 R and  30 B face the shutter  22  (reference S 38 ). Under this condition, the scanning mechanism  50  is driven so that the scanning operation of the line sensor  44  is carried out (reference S 39 ), and thus, the G image signal is outputted through the line sensor  44  (reference S 40 ). 
     When the output operation of the G image signal is completed, the electro-developing recording medium  30  and the color separation filter  80  are rotated by approximately 120 degrees, and thus, the third recording area  30 B is positioned close to the scanning mechanism  50  (reference S 41 ) and the first and second recording areas  30 R and  30 G face the shutter  22  (reference S 42 ). Under this condition, the scanning mechanism  50  is driven so that the scanning operation of the line sensor  44  is carried out (reference S 43 ), and thus, the B image signal is outputted through the line sensor  44  (reference S 44 ). 
     Thus, when the R, G and B image signals have been read out from the electro-developing recording medium  30 , the light source  42  is put out (reference S 45 ). 
     As described above, in the first embodiment, the scanning mechanism  50 , by which the images recorded on the recording areas  30 R,  30 G and  30 B of the electro-developing recording medium  30  are read out, is disposed on the second position which is under the rotational axes of the electro-developing recording medium  30  and the color separation filter  80 , and the optical axis of the photographing optical system  12  is provided on the first position which is above the rotational axes. Each of the recording areas  30 R,  30 G and  30 B is set to the first position when the photographing operation is performed, and is set to the second position when the reading operation is performed. 
     Therefore, the scanning mechanism  50  is disposed at a position offset from the optical axis of the photographing optical system  12 , and the size of the camera along the optical axis is reduced, so that the degree of freedom in designing the camera is improved. 
     FIG. 6 is a block diagram of the still video camera (i.e., the electro-developing type camera) to which the second embodiment is applied. Note that an external view of the still video camera is the same as that of the first embodiment, and the construction of the electro-developing recording medium  30  is the same as that of the first embodiment. 
     In FIG. 6, a color separation filter  80  and an electro-developing recording medium  30  are disks, are coaxially disposed, and face each other. An output shaft  91  of a first stepping motor  90  is connected to a center axis of the color separation filter  80 , and an output shaft  92  of a second stepping motor  90 ′ is connected to a center axis of the electro-developing recording medium  30 . The first and second stepping motors  90  and  90 ′ are disposed on opposite positions about the color separation filter  80  and the electro-developing recording medium  30 . The first stepping motor  90  is driven by a first motor drive circuit  93  based on an output signal of the exposure control circuit  27 . The second stepping motor  90 ′ is driven by a second motor drive circuit  93 , based on an output signal of the exposure control circuit  27 . 
     First and second original point sensors  94  and  94 ′ are disposed close to peripheral portions of the color separation filter  80  and the electro-developing recording medium  30 , respectively. These original point sensors  94  and  94 ′ are photo-interrupters, so that the original positions of the color separation filter  80  and the electro-developing recording medium  30  are detected, and signals indicating the original points are inputted into the system control circuit  20 . 
     A scanning mechanism  50  is provided close to the electro-developing recording medium  30 . The scanning mechanism  50  is positioned above the first and second stepping motor  90  and  90 ′, and is retreated upward to a position above the electro-developing recording medium  30 , when an image signal is recorded on the electro-developing recording medium  30 . The scanning mechanism  50  is positioned close to the electro-developing recording medium  30  and is moved along a straight line shown by an arrow A in FIG. 6, when the image signal recorded on the electro-developing recording medium  30  is read out therefrom. 
     The other components shown in FIG. 6 are the same as those of the first embodiment shown in FIG.  2 . 
     FIG. 7 shows the scanning mechanism  50  and members provided closed thereto in the second embodiment. 
     A moving member  52  is slidably supported by a pair of guide shafts  51 , and has first and second leg portions  52   a  and  52   b . The first leg portion  52   a  is extended between the color separation filter  80  and the photographing optical system  12 , and the second leg portion  52   b  is extended along a rear surface of the electro-developing recording medium  30 . 
     The light source  42  is mounted on the first leg portion  52   a , so that an illumination light beam radiated from the light source  42  is irradiated onto the electro-developing recording medium  30  through a collimator lens (not shown) attached to the first leg portion  52   a . The scanner optical system  43  is provided in the second leg portion  52   b  and the line sensor  44  is fixed on a rear surface of the second leg portion  52   b . Each of the light source  42  and the line sensor  44  is extended in a horizontal direction. A rack  53 , provided on a side surface of the moving member  52 , meshes with a pinion gear  54 . Pinion gear  54  meshes with a gear fixed on an output shaft of a scan drive motor  55 . 
     As shown in FIG. 8, the color separation filter  80  is divided into an R filter element  80 R, a G filter element  80 G, a B filter element  80 B and a transparent filter element (i.e., a reading area)  80 T, by two straight lines which pass through the center axis of the filter  80  and intersect at a right angle. Namely, each of the filter elements  80 R,  80 G,  80 B and  80 T has a fan-shape the center angle of which is 90 degrees. 
     The transparent filter element  80 T passes all light having any wavelength. Namely, as shown by reference L 1  in FIG. 9, all wavelength components, included in the light radiated from the light source  42 , pass the transparent filter element  80 T, and thus, the spectral characteristics of the transparent filter element  80 T are flat. Conversely, the filter elements  80 R,  80 G and  80 B pass only light having a predetermined wavelength an example of which is shown by L 2  in FIG.  9 . Namely, the transparent filter element  80 T has spectral characteristics different from those of the filter elements  80 R,  80 G and  80 B. 
     A mask  95  for blocking light is formed on a portion which is located at an outermost portion of the transparent filter element  80 T. An original point sensor  94 , which is a photo-interrupter, is provided on a portion facing a peripheral portion of the transparent filter element  80 T, to sense the mask  95 . 
     In FIG. 7, the electro-developing recording medium  30  has a first recording area  30 R on which a red (R) image is formed, a second recording area  30 G on which a green (G) image is formed, and a third recording area  30 B on which a blue (B) image is formed. Each of these recording areas  30 R,  30 G and  30 B is rectangular, and is positioned between the photographing optical system  12  and the scanner optical system  43  when positioned at the uppermost position (see the recording area  30 R in FIG.  7 ). Similar to the color separation filter  80 , a mask  95 ′ is formed on a portion which is located outside of the first recording area  30 R. An original point sensor  94 ′, which is a photo-interrupter, is provided on a portion facing a peripheral portion of the electro-developing recording medium  30 , to sense the mask  95 ′. 
     When a photographing operation is performed, one of the filter elements  80 R,  80 G or  80 B is positioned behind the photographing optical system  12 , namely on the photographing optical axis, and the electro-developing recording medium  30  is positioned in such a manner that one of the recording areas  30 R,  30 G or  30 B is positioned on the photographing optical axis. When the R image is recorded in the first recording area  30 R, the R filter element  80 R is positioned in front of the recording area  30 R. When the G image is recorded in the second recording area  30 G, the G filter element  80 G is positioned in front of the recording area  30 G. When the B image is recorded in the-third recording area  30 B, the B filter element  80 B is positioned in front of the recording area  30 B. Namely, while one frame image is recorded in the electro-developing recording medium  30 , the color separation filter  80  is rotated by  3 / 4  revolution and the electro-developing recording medium  30  is rotated by one revolution. 
     After completing the photographing operation, if the scan start switch  16  is operated, the scan drive motor  55  is rotated so that the moving member  52  is moved downward. Thus, a scanning operation of the line sensor  44  is performed, so that the line sensor  44  is moved in a direction perpendicular to the longitudinal direction thereof. The scanning operation is carried out for each of the recording areas  30 R,  30 G and  30 B, and while the scanning operation is performed, the electro-developing recording medium  30  is rotated by one revolution, and the color separation filter  80  is stopped. 
     FIG. 10 shows a timing chart of a photographing operation and a reading operation of the second embodiment. 
     The operations from the turning ON of the release switch  14  (reference S 11 ) to the opening operation of the shutter  22  (reference S 16 ) are the same as those of the first embodiment shown in FIG.  5 . 
     Prior to the opening operation (reference S 16 ) of the shutter  22 , the color separation filter  80  has been positioned in such a manner that the R filter element  80 R faces the shutter  22  (reference S 17 ), and the recording medium  30  has been positioned in such a manner that the first recording area  30 R faces the R filter element  80 R (reference S 18 ). Therefore, the R image is formed or developed on the first recording area  30 R. 
     Note that the rotational positions of the electro-developing recording medium  30  and the color separation filter element  80  are obtained based on original point signals and rotational command signals. The original point signals are outputted from the original point sensors  94  and  941  when the sensors  94  and  94 ′ sense the masks  95  and  95 ′, respectively. The rotation command signals are outputted from the motor drive circuits  93  and  93 ′ so that the stepping motors  90  and  90 ′ are driven. 
     When the shutter  22  is closed, the color separation filter  80  is rotated by approximately 90 degrees, and the electro-developing recording medium  30  is rotated by approximately 120 degrees. As a result, the G filter element  80 G faces the shutter  22  (reference S 19 ), and the second recording area  30 G faces the G filter element  80 G (reference S 20 ). Under this condition, the recording medium activating signal of the second recording area  30 G is set to the ON condition (reference S 21 ), so that an electric voltage is applied to the second recording area  30 G, and the shutter  22  is opened for an exposure period (reference S 22 ) which is obtained by the photometry calculation. Therefore, the G image is formed or developed on the second recording area  30 G. 
     When the shutter  22  is closed, the color separation filter  80  is rotated by approximately 90 degrees, and the electro-developing recording medium  30  is rotated by approximately 120 degrees. As a result, the B filter element  80 B faces the shutter  22  (reference S 23 ), and the third recording area  30 B faces the B filter element  80 B (reference S 24 ). Then, the recording medium activating signal of the third recording area  30 B is set to the ON condition (reference S 25 ), so that an electric voltage is applied to the third recording area  30 B, and the shutter  22  is opened for the exposure period (reference S 26 ) which is obtained by the photometry calculation. Therefore, the B image is formed or developed on the third recording area  30 B. 
     Thus, when the R, G and B images have been developed by the recording areas  30 R,  30 G and  30 B, the quick return mirror  21  is changed to the down-condition (reference S 27 ) and the aperture  12   a  is driven to the fully open condition (reference S 28 ). 
     When the scan start switch  16  is depressed and a scanner drive command signal is outputted (reference S 31 ), the light source  42  is lit (reference S 32 ) and the shutter  22  is fully opened (reference S 30 ). The color separation filter  80  is set in such a manner that the transparent filter element  80 T faces the shutter  22  (reference S 47 ), and the electro-developing recording medium  30  is set in such a manner that the first recording area  30 R faces the transparent filter element  80 T (reference S 33 ). The scanning mechanism  50  is then driven, so that a scanning operation of the line sensor  44  is carried out (reference S 35 ). Thus, the R image signal is outputted or read out through the line sensor (reference S 36 ). 
     When the output operation of the R image signal is completed, the electro-developing recording medium  30  is rotated by approximately 120 degrees, so that the second recording area  30 G faces the transparent filter element  80 T (reference S 37 ). The scanning mechanism  50  is then driven so that the scanning operation of the line sensor  44  is carried out (reference S 39 ). Thus, the G image signal is outputted through the line sensor  44  (reference S 40 ). 
     When the output operation of the G image signal is completed, the electro-developing recording medium  30  is rotated by approximately 120 degrees, so that the third recording area  30 B faces the transparent filter element  80 T (reference S 41 ). Then, the scanning mechanism  50  is driven so that the scanning operation of the line sensor  44  is carried out (reference S 43 ). Thus, the B image signal is outputted through the line sensor  44  (reference S 44 ). 
     When the R, G and B image signals have been read out from the electro-developing recording medium  30 , the light source  42  is put out (reference S 45 ), and the shutter  22  is closed (reference S 46 ) 
     As described above, in the second embodiment, the transparent filter element  80 T is provided in the color separation filter  80  which is disposed in front of the electro-developing recording medium  30 . When an image developed by the electro-developing recording medium  30  is read from the electro-developing recording medium, the transparent filter element  80 T is placed in front of the electro-developing recording medium  30 . Therefore, when reading the image, it is not necessary to withdraw one of the color separation filter  80  or the electro-developing recording medium  30  so that the color separation filter  80  and the electro-developing recording medium  30  do not face each other. Namely, a device for retreating one of the color separation filter  80  or the electro-developing recording medium  30  is not necessary, and therefore, the electro-developing type camera can be made with a less complicated structure and becomes less bulky. 
     Note that, instead of the transparent filter element  80 T, an opening  80 P having a fan-shape as shown by a chained line in FIG. 8 may be formed in the color separation filter  80 . Further, the transparent filter element  80 T can be replaced with another filter element which has spectral characteristics which are different from those of R, G and B light beams and are proper for the reading operation, when a light source having a broad spectrum distribution, such as a fluorescent light, is used. 
     If the spectral characteristics of the reading area  80 T of the color separation filter  80  is flat, the reading area  80 T may be disposed on the optical axis of the photographing optical system  12 , so that a simple monochrome image can be obtained using any one of the recording areas  30 R,  30 G and  30 B. 
     FIGS. 11 and 12 show a third embodiment of a color separation filter. FIG. 11 shows a color separation filter, and FIG. 12 shows a diagram showing spectral characteristics of each of the filter elements of the color separation filter. Note that, in the third embodiment, an external view of the still video camera and the structure of the electro-developing recording medium are the same as those of the first and second embodiments, and a block diagram of the still video camera is the same as that of the second embodiment. 
     In the third embodiment, a light source  42 , which is provided in a scanning mechanism  50 , has an LED radiating blue light. Other constructions of the third embodiment are basically the same as those of the second embodiment, except for the color separation filter  80 . 
     In FIG. 11, the color separation filter  80  has three primary color filter elements  80 R, BOG and BOB. Namely, the color separation filter  80  is divided into the R filter element  80 R, the G filter element  80 G and the B filter element  80 B, by three lines which pass through the center axis of the filter  80 , so that each of the filter elements  80 R,  80 G and  80 B has a fan-shape the center angle of which is 120 degrees. 
     A mask  95  for cutting light is formed on an outermost periphery of the B filter element  80 B. An original point sensor (reference  94  in FIG.  7 ), which is a photo-interrupter, is disposed at a portion facing the outer periphery of the color separation filter  80 . 
     The B filter element  80 B passes blue light, and has spectral characteristics such that substantially all of the light emitted from the light source  42  passes therethrough. Namely, as shown by reference L 3  in FIG. 12, spectral characteristics of the B filter element  80 B are slightly broader than wavelength distribution L 4  of the light radiated from the light source  42 . The spectral characteristics of the B filter element  80 B may be substantially the same as that of wavelength distribution of the light radiated from the light source  42 . 
     FIG. 13 shows a timing chart of a photographing operation and a reading operation of the third embodiment. 
     The operations from the turning ON of the release switch  14  (reference S 11 ) to the opening operation of the shutter  22  (reference S 16 ) are the same as those of the second embodiment shown in FIG.  10 . Therefore, the R image is formed, or developed, on the first recording area  30 R. 
     The rotational positions of the electro-developing recording medium  30  and the color separation filter element  80  are obtained based on original point signals which are outputted from the original point sensors  94  and  94 ′, and the rotation command signals which are outputted from the motor drive circuits  93  and  93 ′, similarly to the second embodiment. 
     When the shutter  22  is closed, the color separation filter  80  and the electro-developing recording medium  30  are rotated by approximately 120 degrees, respectively. Thus, the G filter element  80 G faces the shutter  22  (reference S 19 ), and the second recording area  30 G faces the G filter element  80 G (reference S 20 ). Then, a recording medium activating signal of the second recording area  30 G is set to the ON condition (reference S 21 ), so that an electric voltage is applied to the second recording area  30 G, and the shutter  22  is opened for an exposure period (reference S 22 ) which is obtained by the photometry calculation. Therefore, the G image is formed or developed on the second recording area  30 G. 
     When the shutter  22  is closed, the color separation filter  80  and the electro-developing recording medium  30  are rotated by approximately 120 degrees, respectively. Thus, the B filter element BOB faces the shutter  22  (reference S 23 ), and the third recording area  30 B faces the B filter element  80 B (reference S 24 ). Then, the recording medium activating signal of the third recording area  30 B is set to the ON condition (reference S 25 ), so that an electric voltage is applied to the third recording area  30 B, and the shutter  22  is opened for the exposure period (reference S 26 ) which is obtained by the photometry calculation. Therefore, the B image is formed or developed on the third recording area  30 B. 
     Thus, when the R, G and B images have been developed by the recording areas  30 R,  30 G and  30 B, the quick return mirror  21  is changed to the down-condition (reference S 27 ) and the aperture  12   a  is driven to the fully open condition (reference S 28 ). 
     When the scan start switch  16  is depressed and a scanner drive command signal is outputted (reference S 31 ), the light source  42  is lit (reference S 32 ) and the shutter  22  is fully opened (reference S 30 ). The color separation filter  80  is set in such a manner that the B filter element  80 B faces the shutter  22  (reference S 47 ), and the electro-developing recording medium  30  is set in such a manner that the first recording area  30 R faces the B filter element  80 B (reference S 33 ). Then, the scanning mechanism  50  is driven, so that a scanning operation of the line sensor  44  is carried out (reference S 35 ). Since substantially all components included in the blue light outputted from the light source  42  pass through the B filter element  80 B, the first recording area  30 R is effectively illuminated by the light outputted from the light source  42 . Therefore, the R image signal recorded on the first recording area  30 R is read out through the line sensor and is outputted therethrough (reference S 36 ). 
     When the output operation of the R image signal is completed, the electro-developing recording medium  30  is rotated by approximately 120 degrees, so that the second recording area  30 G faces the B filter element  80 B (reference S 37 ). Under this condition, the scanning mechanism  50  is driven so that the scanning operation of the line sensor  44  is carried out (reference S 39 ), and thus, the G image signal is outputted through the line sensor  44  (reference S 40 ). 
     When the output operation of the G image signal is completed, the electro-developing recording medium  30  is rotated by approximately 120 degrees, so that the third recording area  30 B faces the B filter element  80 B (reference S 41 ). Then, the scanning mechanism  50  is driven so that the scanning operation of the line sensor  44  is carried out (reference S 43 ), and thus, the B image signal is outputted through the line sensor  44  (reference S 44 ). 
     Thus, when the R, G and B image signals have been read out from the electro-developing recording medium  30 , the light source  42  is put out (reference S 45 ) and the shutter  22  is closed (reference S 46 ). 
     As described above, in the third embodiment, the LED radiating blue light is provided as the light source  42 . And, when an image developed on the electro-developing recording medium  30  is read out therefrom, the B filter element  80 B, through which substantially all of the light outputted from the light source  42  passes, is disposed in front of the electro-developing recording medium  30 . Therefore, the R, G and B images recorded in the electro-developing recording medium  30  can be read out therefrom. Thus, an effect which is the same as that of the second embodiment is obtained. 
     Note that, the filter element, which passes light radiated from the light source  42  in the image reading operation, is not restricted to the B filter element  80 B, but any filter element can be used if it has spectral characteristics close to a wavelength distribution of the light outputted from the light source  42 . 
     Note that, although the electro-developing recording medium  30  and the color separation filter  80  are constructed in the above described embodiments to rotate about the axes thereof, they can be constructed so as to move along straight lines, respectively. 
     Further, note that the electro-developing recording medium  30  is not restricted to the structure described above, and may be any other structure by which an image is electronically developed. 
     Although the embodiments of the present invention have been described herein with reference to the accompanying drawings, obviously many modifications and changes may be made by those skilled in this art without departing from the scope of the invention. 
     The present disclosure relates to subject matter contained in Japanese Patent Application No. 7-162922 (filed on Jun. 6, 1995), No. 7-162923 (filed on Jun. 6, 1995) and No. 7-182094 (filed on Jun. 26, 1995) which are expressly incorporated herein, by reference, in their entirety.