Electronic image pickup apparatus

An electronic image pickup apparatus comprises a photographic optical system; solid state image pickup devices disposed on a plant where a subject image formed by subject beams which have passed through the photographic optical system is formed; a main mirror disposed between the photographic optical system and the solid state image pickup devices, wherein a part of the main mirror is formed of a half mirror to divide the subject beams which have passed through the photographic optical system into an observing beam and a focus detecting beam; a sub-mirror for reflecting the subject beam which has passed through the part of the main mirror; a focus detecting optical system for forming an image of the subject beam reflected by the sub-mirror on a partial area of the solid image pickup devices; and an electrical circuit for outputting focus detecting information based on image signals of the partial areas of the solid image pickup devices. The structure provides an electronic image pickup apparatus which contributes to the down-sizing of the apparatus and to the reduction of production cost by eliminating an image pickup device which is dedicated for focus detection.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electronic image pickup apparatus and more specifically to a focus detecting unit applied to an electronic image pickup apparatus having image pickup devices for generating electrical image signals by photoelectrically converting an optical image of a subject formed by a photographic optical system.

2. Description of the Related Art

Various proposals have been made lately on electronic image pickup apparatuses such as a digital still camera and a digital video camera which are capable of photoelectrically converting an optical image of a subject formed of light beams which have been transmitted through a photographic optical system into electrical signals by utilizing image pickup devices such as CCDs (Charge Coupled Device) and of recording image signals generated therefrom to a recording medium or the like as image data of a predetermined mode.

For instance, Japanese Patent Laid-Open No. Hei. 8-262564 has disclosed a single-lens reflex type electronic image pickup apparatus constructed so as to be able to form an optical image to be photographed and recorded and an optical image for observation at different positions by using beams which have been transmitted through a single photographic optical system. This electronic image pickup apparatus is provided with image pickup means such as solid state image pickup devices on an image forming plane for picking up the image and image pickup means for detecting a focal point at the position equivalent to that image forming plane beside the image pickup means. The apparatus is arranged so as to carry out a focusing operation by a focus detecting means (AF means) using the TTL phase difference detecting method for detecting the focusing state of the optical image by guiding a part of the beams which have been transmitted through the photographic optical system to the focus detecting image pickup means.

An electronic image pickup apparatus disclosed in Japanese Patent Laid-Open No. Hei. 274130 is a so-called video movie camera for shooting and recording mainly video images. While it is provided with image pickup means such as image pickup devices disposed within the camera main body, a focusing detecting unit of the TTL phase difference detecting method comprising other image pickup means different from the image pickup means such as the image pickup devices is disposed with the inside of a lens barrel for holding camera lenses.

However, the prior art electronic image pickup apparatuses disclosed in Japanese Patent Laid-Open Nos. Hei. 8-262564 and 274130 comprise an image pickup means such as image pickup devices dedicated for detecting the focal point beside an image pickup means such as image pickup devices for shooting and recording an optical image.

Such a construction has caused problems that a number of parts of the whole electronic image pickup apparatus increases and the size of the apparatus itself increases. At the same time, because it requires a plurality of expensive parts such as the image pickup devices, it has caused a problem that the production cost also increases.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide an electronic image pickup apparatus for photoelectrically converting an image of a subject formed by a photographic optical system into image signals by utilizing image pickup devices which can contribute to the down-sizing of the apparatus itself and to the reduction of the production cost and wherein no image pickup device dedicated for detecting a focal point is required.

An electronic image pickup apparatus according to a first aspect of the invention comprises a photographic optical system; solid image pickup devices disposed on a plane where a subject image formed by beams of subject light which have passed through the photographic optical system is formed; a main mirror disposed between the photographic optical system and the solid state image pickup devices, wherein a part of the main mirror is formed of a half mirror to divide the subject light beams which have passed through the photographic optical system into an observing beam and a focus detecting beam; a sub-mirror for reflecting the subject light beam which has passed through the part of the main mirror; a focus detecting optical system for forming an image of the subject light beam reflected by the sub-mirror on a partial area of the solid state image pickup devices; and an electrical circuit for outputting focus detecting information based on image signals of the partial areas of the solid state image pickup devices.

An electronic image pickup apparatus according to a second aspect of the invention comprises a photographic optical system; a finder optical system for allowing a subject image formed of subject light beams which have passed through the photographic optical system to be observed; solid image pickup devices disposed on a plane where the subject image formed by the subject light beams which have passed through the photographic optical system is formed; a reflecting mirror for reflecting at least a part of the subject light beams in a direction different from the finder optical system; a focus detecting optical system for forming an image of the subject light beam reflected by the reflecting mirror on a predetermined area of the solid state image pickup devices; and an electrical circuit for outputting focus detecting information based on image signals of the predetermined areas of the solid state image pickup devices.

An electronic image pickup apparatus according to a third aspect of the invention comprises a photographic optical system; image pickup means for executing an image pickup operation for picking up a subject image via the photographic optical system; reflecting means which advances between the photographic optical system and the image pickup means during a photographing preparing state to reflect at least a part of subject light beams to the outside of the photographing optical path; a focus detecting optical system for forming an image of the subject light beams reflected by the reflecting means in a predetermined area in the image pickup area of the image pickup means; and focus detecting means for carrying out a focus detecting operation based on signals from the solid image pickup means.

The above and other objects and advantages of the invention will become more apparent from the following detailed explanation.

According to the present invention, it is possible to provide an electronic image pickup apparatus for photoelectrically converting a subject image formed by the photographic optical system into image signals by utilizing image pickup devices, and for recording the image signals to a recording medium as image data, which can contribute to the down-sizing of the apparatus itself and to the reduction of the production cost by arranging the apparatus such that no image pickup device dedicated for detecting the focal point is required.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a diagram schematically showing the disposition of the main components of an electronic image pickup apparatus of a first embodiment of the invention together with optical paths within the electronic image pickup apparatus of beams which have been transmitted through a photographic optical system. It is noted thatFIG. 1shows only components which are directly related to the invention to simplify the diagram.

As shown inFIG. 1, a photographic optical system11comprising a plurality of lenses and other elements for condensing beams from a subject (hereinafter referred to as subject beams) and for guiding the subject beams to the inside of the electronic image pickup apparatus is disposed at the front side of the electronic image pickup apparatus.

The photographic optical system11comprises an in-focus lens11awhich is a focus adjusting optical system for adjusting the focus by moving in the direction along an optical axis0to form the subject image at a predetermined position and a stopping member11bfor controlling a quantity of light of the subject beams transmitting through the photographic optical system11. The stopping member11bhas functions of holding a predetermined diaphragm opening and of blocking the input subject beam by completely closing the opening.

An infrared cut filter12for mainly removing the infrared component in light components contained in the subject beams and an optical low-pass filter (LPF)13for reducing noise components such as moire among the optical components contained in the subject beams are disposed behind the photographic optical system11.

A main mirror14which is a reflecting mirror is partly formed of a half-mirror section, serves as a dividing optical system capable of dividing the subject beams which have been transmitted through the photographic optical system11into an observing focus detecting beam. The main mirror14is an optical member capable of passing the subject beam by receding to the outside of the optical path of the subject beam and is disposed behind the LPF13so that one end thereof freely turns in the direction of an arrow X1inFIG. 1with respect to an internal fixing member (not shown) of the electronic image pickup apparatus.

A sub-mirror19formed of an optical member such as a total reflection mirror is provided at a predetermined position on the back of the main mirror14and is turnable with respect to the main mirror14so as to be able to guide the subject beams which have been transmitted through the half-mirror section of the above-mentioned main mirror14to a focus detecting optical system30.

Then, image pickup means comprising solid image pickup devices21(hereinafter simply referred to as CCDs21) is disposed behind the main mirror14and at the position of an image forming plane where a subject image formed by the subject beams which have been transmitted through the photographic optical system11is formed. The CCD21generates an electrical image signal by receiving and photoelectrically converting the optical subject image. Various solid image pickup devices such as the CCD described above and a MOS type sensor may be applied to the CCD21.

A finder optical system for receiving the beams of the subject from the photographic optical system11to mainly observe the subject image is disposed at a predetermined position above the main mirror14. A focus detecting optical system30for receiving the part of the beams of the subject from the photographic optical system11to guide to predetermined a position on the light receiving plane of the CCD21to form the image again is disposed at a predetermined position under the main mirror14.

Only a partial area of the main mirror14is formed of the half mirror as described above and another area is formed of a total reflecting mirror. The partial area in this case is the area corresponding to the sub-mirror19and the area formed of the half-mirror, i.e., the half-mirror section, is arranged so as to transmit the subject beam from the photographic optical system11and the area other than the half-mirror section is arranged so as to totally reflect the subject beam from the photographic optical system11.

The main mirror14turns centering on the fulcrum of a fixed member (not shown) between the position (hereinafter referred to as a photographic preparing position) indicated by a solid line in FIG.1and the position (hereinafter referred to as a photographing position) indicated by a dash line in FIG.1. At the same time, the sub-mirror19is disposed at a predetermined position corresponding to the position of the main mirror14by following the turn of the main mirror14.

When the main mirror14is located at the photographing preparing position (the position of the solid line inFIG. 1) the main mirror14is disposed aslant by about 45 degrees with respect to the optical axis. The reflecting plane of the main mirror14faces to the side of the photographic optical system11(that is, to the side of the subject in front of the electronic image pickup apparatus) and to the side of the finder optical system.

The sub-mirror19is disposed so as to have a predetermined angle with respect to the main mirror14on the optical path of the subject beam at this time. Then, the reflecting plane of the sub-mirror19faces to the side of the photographic optical system11(the side of the subject) and to the side of the focus detecting optical system30.

Accordingly, a part of the subject beam from the photographic optical system11is guided to the side of the finder optical system by the total reflecting plane of the main mirror14and the other part of the subject beams which have been transmitted through the half-mirror section of the main mirror14is guided to the side of the focus detecting optical system30by the total reflecting plane of the sub-mirror19.

Thereby, when the main mirror14is located at the photographing preparing position, only the subject beams which have been transmitted through the half-mirror section of the main mirror14and have gone through the sub-mirror19and the focus detecting optical system30are guided to the CCD21.

Meanwhile, when the main mirror14is located at the photographing position (the position of the dot line in FIG.1), the main mirror14and the sub-mirror19recede to the position where they do not block the optical path of the subject beams which have been transmitted through the photographic optical system11as described above. Accordingly, all of the subject beam is guided to the side of the CCD21at this time and is irradiated to the whole area of the light receiving plane of the CCD21.

The finder optical system comprises a pint plate15and a condenser lens16which are disposed in the vicinity of an image forming plane where the observing subject image is formed to guide the subject beam to the position for observing the subject image, a pentagonal prism17for guiding the subject image to the observing position and for reversing right and left images, an eyepiece lens18for magnifying the subject image formed on the pint plate15to form the image at the optimum observing position and other elements (not shown).

The focus detecting optical system30comprises a view field mask31, a field lens32, a total reflection mirror33, a pupil mask34, an image reforming lens35and other elements (not shown) and plays a role of forming an image of a predetermined mode at a predetermined position on the light receiving plane of the CCD21from a focus detecting subject beam which is a part of the subject beam from the photographic optical system11and which is guided by the action of the main mirror14and the sub-mirror19when the electronic image pickup apparatus is put in the photographing preparing state.

The focus detecting optical system30in the electronic image pickup apparatus will be explained in detail below.

FIGS. 2 and 3are side section and perspective views showing the conceptual structure of the focus detecting optical system in the electronic image pickup apparatus and conceptually showing the state how the subject beams which have been transmitted through the photographic optical system11arrive at the CCD21via the focus detecting optical system30. It is noted that inFIGS. 2 and 3, the components which are considered to be unnecessary for explaining the structure and the action of the focus detecting optical system30, i.e., the main mirror14, the sub-mirror19, the total reflection mirror33and a casing member for holding and unitizing each component of the focus detecting optical system30, will be omitted here and only the main components are shown here to simplify the figures. Further, although the optical path of the subject beam of only one exit pupil Ha side is shown inFIG. 2, that of the other side (Hb side) is not shown in the figure because it is symmetrical to Ha.

The focus detecting optical system30in the electronic image pickup apparatus is an optical system for guiding the focus detecting beam contributing for the focus detecting operation to the CCD21and comprises a part of the so-called TTL phase difference detecting type focus detecting means.

As shown inFIGS. 2 and 3, the focus detecting optical system30comprises the view filed mask31for restricting an irradiation range of the subject beams which have been transmitted through the photographic optical system11(not shown in FIG.3), the field lens32for condensing the subject beam which has passed through the view field mask31, the total reflection mirror33(not shown inFIGS. 2 and 3) for bending the optical path of the subject beams which have been transmitted through the field lens32to guide to the side of the CCD21, the pupil mask34having two openings34aand34bwhich are disposed almost symmetrically about the optical axis O of the subject beam to split the subject beam reflected by the total reflection mirror33into two beams, the image reforming lens35comprises two lenses35aand35bdisposed at the behind positions corresponding to the openings34aand34bof the pupil mask34and other elements (not shown).

The subject beam which has been inputted from the photographic optical system11to the electronic image pickup apparatus constructed as described above follows the following path.

The subject beam inputted to the photographic optical system11is restricted to a predetermined quantity of light by the stopping member11b. When it is outputted to the rear part after passing through the photographic optical system11, its unnecessary light components are removed by the infrared cut filter12and the LPF13.

The optical path of the subject beam varies depending on the state of the main mirror14disposed behind the photographic optical system11and the two filters12and13as described above.

When the main mirror14is located at the photographing position (the position indicated by the dash line in FIG.1), the optical path of the subject beams which have been transmitted through the photographic optical system11is not blocked by the main mirror14and, the sub-mirror19and the whole beam is irradiated to the whole area of the light receiving plane of the CCD21. Receiving such beam, the image pickup means such as the CCD21executes a predetermined image pickup operation.

When the main mirror14is located at the photographing preparing position (the position indicated by the solid line inFIG. 1) on the other hand, the optical path of the subject beam irradiated toward the main mirror14is bent, except for a part thereof, by about 90 degrees by the total reflecting plane of the main mirror14and is reflected toward the finder optical system disposed thereabove.

The subject image is formed from the subject beam guided to the finder optical system side on the pint plate15and the condenser lens16. At the same time, the beam which has been transmitted through them enters the pentagonal prism17. The pentagonal prism17changes the optical path thereof in a predetermined direction and the beam is outputted behind the electronic image pickup apparatus via the eyepiece lens18. Then, the eyepiece lens18forms the subject image into a predetermined size again.

In this case, the main mirror14reverses the upper and lower images of the subject image formed from the subject beam to form on the pint plate15. The pentagonal prism17also reverses the right and left images and the eyepiece lens18magnifies the image. Thereby, the photographer can observe the subject image adequately.

The part of the subject beam from the photographic optical system11transmits through the half-mirror section of the main mirror14and advances to the sub-mirror19. The sub-mirror19bends its optical path by a predetermined angle to guide to the focus detecting optical system30.

The subject beam guided to the focus detecting optical system30arrives at a predetermined position on the light receiving plane of the CCD21through the following path.

That is, the subject beams which have been transmitted through the two areas Ha and Hb of the output pupil H of the photographic optical system11as shown inFIGS. 2 and 3form the image on the plane corresponding to a reference character G shown inFIG. 2(hereinafter the plane indicated by the reference character G will be referred to as an image forming plane). The image forming plane G is the position corresponding to the light receiving plane of the pint plate15when the main mirror14is located at the photographing preparing position (the position of the solid line inFIG. 1) and is the position corresponding to the light receiving plane of the CCD21when the main mirror14is located at the photographing position (the position of the dotted line in FIG.1).

While the subject beam enters the focus detecting optical system30via the path described above, the subject beam which has entered the focus detecting optical system30is irradiated to predetermined light receiving areas152aand152bon an image pickup area100which is the light receiving plane of the CCD21to form the image again there after passing through the view field mask31, the field lens32, two openings34aand34bof the pupil mask34and the image reforming lens35(see FIG.5).

When an image I is formed on the image forming plane G in focus by the photographic optical system11in this case (see FIG.2), the image I turns to first and second images I1and I2as it is imaged again on the image pickup area100of the CCD21by the field lens32and the image reforming lens35. It is noted that the image pickup area100of the CCD21is a secondary image forming plane which is vertical to the optical axis O.

When the state of the photographic optical system11is that of front pin, i.e., when the subject image F is formed in front of the image forming plane G, the subject image F is imaged again at the position close the optical axis O as the first and second images F1and F2.

When the state of the photographic optical system11is that of rear pin, i.e., when the subject image R is formed behind the image forming plane G, the subject image R is imaged again at the position separated from the optical axis O as the first and second images R1and R2.

That is, the focus detecting optical system30forms the two images of the first image (I1, R1or F1) and the second image (I2, R2or F2) by receiving the part of the subject beam as described above. Then, it can detect the state of the photographic optical system11, i.e., whether it is focused or not or it is in the front pin state or in the rear pin state, by detecting the output of the CCD21by the first and second images in each case and by detecting the distance between them by implementing a predetermined process based on a signal thus obtained. Means generally used in the conventional focus detecting unit of measuring the distance between the both images by finding the distributions of light intensity of the first and second images from each image data output of the corresponding predetermined areas152aand152b(seeFIG. 5) of the CCD21is adopted for the detecting means of this time.

It is noted that the whole photographic area, i.e., the range of the image pickup area100of the CCD21, corresponds to a photographing screen frame150(seeFIG. 4) which can be observed by the finder optical system for example. Then, the focus detecting area151is set within the photographing screen frame150to implement the focus detecting operation to the subject corresponding to a predetermined area within the range of the photographing screen frame150, e.g., the area located almost at the center.

The focus detecting subject beam transmits through the half-mirror section of the main mirror14to be guided to the focus detecting optical system30by the sub-mirror19as described above. Accordingly, the focus detecting area151may be set at a desired position by arbitrarily setting the position of the half-mirror section of the main mirror14and the sub-mirror19.

Then, the focus detecting optical system30forms view field mask images153aand153bat the predetermined position within the range specified by the view field mask31and the predetermined images again in the areas within the view field mask images153aand153b, i.e., in the focus detecting light receiving areas152aand152b. At this time, the output signal, i.e., the image data in the predetermined range, from the CCD21is fed to a control circuit (not shown inFIGS. 1 through 5see the micro-computer61inFIG. 6described later, which executes a focus detecting arithmetic operation.

It is noted that the view field mask images153aand153bturn out to be trapezoidal images whose upper part is opened more or less as shown inFIG. 5because the beam is irradiated obliquely from the lower side to the CCD21and the image is formed again on the light receiving plane of the CCD21. Although the images formed again on the light receiving areas152aand152bare also deformed in the same manner in this case, the influence to the symmetrical similarity of the focus detecting light receiving areas152aand152bis very small because it is a deformation almost in the vertical direction with respect to the pupil splitting direction (direction along the long side of the photographic screen). Accordingly, it barely affects the accuracy in detecting the focus state.

FIG. 6is a block diagram showing the main electrical components of the electronic image pickup apparatus.

The whole electronic image pickup apparatus is controlled by the micro-computer61which is the control means comprising a central processing unit (hereinafter referred to as a CPU)61a. That is, the micro-computer61is a controller of the system of the electronic image pickup apparatus and comprises the CPU61a, a ROM61b, a RAM61c, and A/D converter (ADC)61d, an EEPROM61ewhich is an internal memory, and other elements (not shown). The micro-computer61controls a series of operations of the electronic image pickup apparatus in accordance with a sequence program stored in advance in the ROM61bprovided therein.

Correcting data peculiar to each electronic image pickup apparatus related to arithmetic operations on focus control, photometry, exposure, AWB (auto white balance) and the like is stored in the EEPROM61e.

The micro-computer61is connected electrically with a diaphragm driving section63for driving and controlling the stopping member11b(see FIG.1), a lens driving section62for driving and controlling the in-focus lens11a(seeFIG. 1) and other element, and a group of switches for generating various command signals in linkage with various control members (not shown), e.g.., a first release switch (1RSW)47for generating command signals for executing preliminary operations such as photometry and AF operation in starting the photographing operating and a second release switch (2RSW)48for generating a command signal for driving the stopping member11band other elements (not shown) to execute an exposing operation.

It is noted that the 1RSW47and the 2RSW48are configured as a so-called two-stage switch which is constructed so that it can be manipulated by a single manipulating member.

The micro-computer61is also connected electrically with a CCD control section43which comprises a timing generator (hereinafter referred to as a TG)82and a signal generator (hereinafter referred to as a SG)83as shown in a diagram showing the structure of the main block in FIG.7. Then, the CCD control section43is connected electrically with the CCD21so as to control the drive of the CCD21.

The CCD21converts the optical subject image formed by the subject beams which have been transmitted through the photographic optical system11into electrical signals. The detailed structure of the CCD21will be described later (see FIGS.8and9).

The CCD21is connected electrically with an image signal processing section42. The signal processing circuit42generates image signals of a predetermined mode by implementing predetermine processes on the output signal from the CCD21. The signal processing circuit42is connected electrically with a focus detecting computing section50, a photometry and exposure computing section45, an AWB section51, a display section46, a recording section44and other elements (not shown). Then, the signal processing circuit42generates and outputs the image signals of the optimum mode and information accompanying thereto to the respective structure blocks.

The focus detecting computing section50is a circuit comprising a focus detecting section for detecting and computing the focal position by receiving the output signal from the signal processing circuit42. The result of the computation, data judging the focusing state and data on predetermined drive of the in-focus lens11aare outputted to the micro-computer61.

The photometry and exposure computing section45is a circuit for calculating the optimum exposure data, i.e., the stopping value of the stopping member11band the value of speed of an electronic shutter of the CCD21, by receiving the output signal from the signal processing circuit42and by detecting the brightness of the subject. The result of calculating is outputted to the micro-computer61. Then, receiving the data, the micro-computer61drives the stopping member11bvia the diaphragm driving section63so that the predetermined stopping value is attained and drives and controls the CCD21with the predetermined value of electronic shutter speed via the CCD control section43.

The AWB section51is a circuit for automatically adjusting the white balance of the subject so that it is optimized by receiving the output signal from the signal processing circuit42. The image signal optimally adjusted by the AWB section51is outputted to the display section46.

The display section46is formed of an image displaying device such as a liquid crystal display (LCD) for example and displays the image signals inputted via the signal processing circuit42and the AWB section51as an image. It also displays photographing information accompanying to the image signal and internal information of the electronic image pickup apparatus itself such as a photographing mode visually in the shape of characters and symbols.

The recording section44receives the output signal from the signal processing circuit42and records the image signal and accompanying photographing information (hereinafter simply referred to as image signal and others) in a predetermined mode.

The detailed structure of the signal processing circuit42, the recording section44and the CCD control section43will be explained below.

FIG. 7is a block diagram showing the main part by taking out the image signal processing section42, the recording section44and a part of the main electrical circuits electrically connected to them.

The signal processing circuit42comprises a correlational double sampling circuit (hereinafter referred to as a CDS)78for removing reset noise and the like from the image signal obtained by the CCD21, a gain control amplifier (hereinafter referred to as an AMP)79for amplifying the output of the CDS78, an AD converter (hereinafter referred to as an A/D)80for converting the output (analog signal) of the AMP79into a digital signal, a process processing circuit81for implementing predetermined processes to the image signal converted into the digital signal by the A/D80, and other elements (not shown).

The CCD control section43controls the predetermined operations of the CCD21by outputting driving signals thereto and comprises a TG82, a SG83and other elements (not shown).

The TG82generates a driving signal such as a transfer pulse for driving the CCD21as well as sample-hold pulses of the correlational double sampling circuit78of the signal processing circuit42and AD conversion timing pulses of the A/D converter80. The SG83generates a signal for synchronizing the micro-computer61with the TG82.

Then, the CCD control section43plays a role of an electronic shutter of the CCD21during exposure, i.e., of controlling the exposure time, based on the result of computation of the photometry and exposure computing section45under the command of the micro-computer61.

The recording section44is constructed so as to be able to store the output signal from the signal processing circuit42in a recording medium86as image data file of a predetermined mode as described above.

That is, the recording section44comprises a DRAM84which is a temporary memory for receiving the image signal and others outputted from the process processing circuit81of the signal processing circuit42to store them temporarily, a recording medium86for storing the image signal and others in a predetermined area as the image data file, and a compressing/expanding circuit85comprising a circuit for implementing the optimum signal processing, i.e., compressing the image signal and others inputted via the DRAM84to record to the recording medium86as the image data file and a circuit for implementing the optimum signal processing for reading and reproducing the image data file recorded in the recording medium86.

The structure of the CCD21of the electronic image pickup apparatus will be explained below in detail.FIG. 8is a diagram showing the image pickup device (CCD) of the electronic image pickup apparatus by enlarging a part thereof.

The charge transfer type of the CCD21applied to the electronic image pickup apparatus of the present embodiment is an interline transfer type. A plurality of light receiving devices which turn out to be an image pickup section are arrayed two-dimensionally in the horizontal and vertical directions in the light receiving plane of the CCD21so that each individual light receiving device forms one pixel.

The CCD21comprises photodiodes101which are a group of light receiving devices disposed two-dimensionally in the horizontal and vertical directions, a transfer gate102for transferring charges (first video image) stored in the photodiodes101to a vertical shift register103, the vertical shift register103for transferring the transferred charges sequentially in the vertical direction and a horizontal shift register104for transferring the charges transferred in the vertical direction by the vertical shift register103sequentially in the horizontal direction and an output section105for converting the charges transferred in the horizontal direction by the horizontal shift register104into a voltage signal to be outputted.

A micro-lens array (not shown) formed of spherical lenses each having predetermined curvature and predetermined focal distance is disposed in front of the photodiode101, i.e., on the side of the light receiving plane. This micro-lens array is disposed corresponding to each light receiving device in order to improve the light sensitivity of the CCD21.

Input light may be condensed efficiently by providing the micro-lens array in front of each light receiving device, i.e., on the beam input plane side. Such arrangement has been generally put into practical use and is called as on-chip micro-lenses.

Color filters (not shown in FIG.8. SeeFIG. 9) are disposed in front of the photodiode101. The color filters are arrayed in the manner of a so-called Bayer array as shown in FIG.9. It is noted that the reference characters R, G and B shown inFIG. 90denote color filter elements selectively transmitting red, green and blue, respectively.

The operation of the electronic image pickup apparatus of the present embodiment constructed as described above will be explained below.

FIG. 10is a flowchart showing a main routine of the micro-computer61, i.e., the cm, of the electronic image pickup apparatus.FIGS. 11A through 11Gare time charts showing actions when the image pickup operation is carried out in the electronic image pickup apparatus.

The electronic image pickup apparatus is activated when power is started to be fed to the electrical circuits including the micro-computer61by turning on a main power switch (not shown) or by loading a battery for example. Thereby, the sequence program stored in the ROM61bin the micro-computer61in advance is executed.

In this state, each electrical circuit block of the electronic image pickup apparatus is initialized in Step S101.

Next, the micro-computer61detects the status of the 1RSW47to confirm whether it is turned on or not. When it confirms an ON signal of the 1RSW47which is generated as a predetermined manipulating member (not shown) is manipulated in Step S102, it advances the process to Step S103.

When it confirms no ON signal of the 1RSW47, it advances the process to Step S105. A series of photometric operations (hereinafter referred to simply as photometric operations) such as storing and reading operations of the light receiving devices which are the image pickup section of the CCD21are carried out in Step S105.

Then, receiving the image signal outputted from the signal processing circuit42and is obtained by the CCD21, the photometry and exposure computing section45executes the predetermined photometric and exposure computing processes in Step S106. Thereby, the micro-computer61calculates information required during the main exposure operation (in recording images), i.e., adequate exposure information corresponding to the subject such as the stopping value of the stopping member11band the value of electronic shutter speed of the CCD21.

That is, the photometric operation is started when the electronic image pickup apparatus is activated and is repeatedly executed (see reference numeral [2] in FIG.11F). At this time, the stopping member11bis in the released state as indicated by the reference number [3] in FIG.11G.

When, when the micro-computer61confirms that the 1RSW47has been turned on in Step S102described above (see the reference number [1] inFIG. 11A, it executes the focus detecting operation in the next Step S103by using the CCD21. At this time, the subject beams which have been transmitted through the photographic optical system11are guided to the focus detecting optical system30via the main mirror14and the sub-mirror19as described above. Then, the predetermined images are formed on the predetermined light receiving areas152aand152bin the image pickup area100of the CCD21via the focus detecting optical system30.

Accordingly, the storing operation (AF exposure. See the reference numeral [4] in FIG.11C. The detail will be described with reference toFIG. 12) within the light receiving areas152aand152bin the CCD21is carried out in Step S103. The focus detecting image signal thus obtained is outputted from the CCD21to the focus detecting computing section50via the signal processing circuit42(reading operation) and the focus detecting computing section50executes the predetermined focus detecting arithmetic operation based on that output signal in Step S104(see the reference numeral [5] in FIG.11F). It is noted that the predetermined focus detecting operation executed here will be described later in detail (see FIG.13).

Next, it is judged whether the result of the focus detecting operation executed in the above-mentioned Step S104is in the in-focus state or non-focus state in Step S107. When it is judged to be the in-focus state, the process is shifted to Step S109or when it is judged to be the non-focus state, the process is shifted to Step S108.

The micro-computer61calculates an amount of move of the in-focus lens11ato put the system into the in-focus state based on the result of the focus detecting operation in the above-mentioned Step S104and moves the in-focus lens11aby driving and controlling the lens driving section62based on that calculation result (see the reference numeral [7] in FIG.11F). After that, the micro-computer61returns the process to Step S102to repeat the similar process of the AF operation thereafter.

Meanwhile, the micro-computer61detects the status of the 2RSW48to confirm whether it is ON or not in Step S109. When it confirms that the 2RSW48is ON (see the reference numeral [6] in FIG.11A), the micro-computer61advances the process to Step S110. When it confirms that the 2RSW48is OFF, it returns the process to Step S102to continuously execute the sequence thereafter while waiting for the time when the 2RSW48is turned ON.

The main exposure operation (see the reference numeral [8] inFIG. 11F) is executed in the process after Step S110.

In the main exposure operation, the micro-computer61controls the photographic optical system11via the diaphragm driving section63to drive same so that the exposure stopping value calculated in the above-mentioned Step S106is attained (diaphragm controlling process. See the reference numeral [9] inFIG. 11G) in Step S110.

Then, in Step S111, the CCD control section43controls the CCD21to start the storing operation of the CCD21by changing over a charge sweep-out signal (SUB. SeeFIG. 11B) to OFF and to execute the main exposure operation by the electronic shutter speed value calculated by the exposure computing process in Step S106(see the reference numeral [8] in FIG.11F). Here, controlling the electronic shutter is an operation for transferring the storage charges of the photodiode101to the vertical shift register103by generating the charge transfer pulse (TGP. SeeFIG. 11C) at a predetermined timing corresponding to the electronic shutter speed value calculated by the CCD control section43.

Then, in Step S112, the micro-computer61drives the stopping member11bso that it is completely closed via the diaphragm driving section63to prevent noise components such as so-called smear from mixing into the image signal to be obtained (see the reference numeral [10] in FIG.11G). Thereby, the light receiving plane of the CCD21is shaded.

Next, the CCD control section43outputs an image reading signal (DCLK. SeeFIG. 11D) to the CCD21while keeping the shaded state of the CCD21in Step S113. Then, the signal processing circuit42reads it after A/D converting the signal of the CCD21(CCD signal: Image signal. SeeFIG. 11E) outputted in synchronism with that signal (DCLK).

Then, the micro-computer61transits a predetermined diaphragm releasing command to drive the stopping member11bto release the stopping member11bvia the diaphragm driving section63(see the reference numeral [12] inFIG. 11G) in Step S114.

Further, the signal processing circuit42implements a predetermined process such as a compressing process to put the image signal obtained by the CCD21into the optimum recording mode and then stores it in the predetermined area of the recording medium86(see the reference numeral [12] inFIG. 11G) in Step S115. After that, the micro-computer61ends the series of operations and returns the process to Step S102described above to repeat the processes thereafter in the same manner.

Next, the procedure of the focus detecting storing operation (AF exposure) and of the focus detecting arithmetic operation carried out by the image pickup device (CCD) in carrying out the focus detecting operation in the electronic image pickup apparatus will be explained by referring to the flowcharts inFIGS. 12 and 13.

FIG. 12is a flowchart showing the sequence of storing and reading operations in the focus detecting light receiving area of the image pickup device (CCD) of the electronic image pickup apparatus andFIG. 13is a flowchart showing the sequence of a focus detecting arithmetic operation.

It is noted that the sequence shown inFIG. 12corresponds to the process in Step S103in FIG.10and the sequence shown inFIG. 13corresponds to the process in Step S104in FIG.10. These will be described below in detail.

The sequence of the storing and reading operations in the focus detecting light receiving area will be explained at first by using FIG.12.

In Step S200, the micro-computer61reads information related to the focus detecting light receiving areas152aand152b,i.e., information related to the effective pixel range of the light receiving areas152aand152b,in the image pickup area100of the CCD21in the electronic image pickup apparatus from the EEPROM61e.

The information related to the effective pixel range of the light receiving areas152aand152bis peculiar information different per each CCD21applied to the individual electronic image pickup apparatus. Accordingly, the peculiar information has been confirmed per each electronic image pickup apparatus in advance in manufacturing the electronic image pickup apparatus and adequate information corresponding to each electronic image pickup apparatus is stored in advance in the EEPROM61eprovided within the micro-computer61of each electronic image pickup apparatus.

Next, the micro-computer61calculates and decides a storage time by which an adequate image signal may be obtained by making reference to the image signal in the light receiving areas152aand152bobtained by the storing operation previously carried out in Step S201.

Then, based on the storage time calculated in Step S201, the micro-computer61controls the storing operation of the CCD21via the CCD control section43in Step S202.

The micro-computer61executes the operation for reading the output of the CCD21, i.e., the image signal, in Step S203. The image signals in the area other than the light receiving areas152aand152bof the image pickup area100are not used in carrying out this focus detecting operation, so that the reading time may be shortened by carrying out the so-called quick sweep-out operation.

Then, in Step S204, the micro-computer61reads only the image signals of the area corresponding to the light receiving areas152aand152bbased on the information on the effective pixel range read out of the EEPROM61ein the process of Step S200and returns to the main routine in FIG.10.

It is noted that the arithmetic operations of photometry, exposure and AWB are carried out by using the CCD21beside such focus detecting arithmetic operation in the electronic image pickup apparatus. In this case, they may be carried out by utilizing the whole area of the image pickup area100without carrying out the quick sweep-out process as described above or by reading the image signal of the area corresponding to a predetermined area for carrying out the photometric and exposure computing processes and for carrying out the AWB computation in the same manner with the focus detecting computation process. It may be carried out by storing information related to each predetermined area in advance in the EEPROM61eand others and by carrying out a process for reading the corresponding information before executing each computation. Then, the required subject beam must be guided to each predetermined area in the image pickup area100of the CCD21by predetermined means by forming the whole of the main mirror14by the half-mirror for example.

Next, the sequence in carrying out the focus detecting computation based on the image signals of the focus detecting light receiving areas152aand152bobtained as described above will be explained with reference to FIG.13.

The known TTL phase difference detecting method is used in the focus detecting computing process executed in the electronic image pickup apparatus. Accordingly, its detailed explanation will be omitted here and only the part characteristic in the present embodiment will be explained below in detail.

After shifting to the sequence of the focus detecting computation (see Step S104in FIG.10and FIG.13), the micro-computer61adds the same color signals within the focus detecting area, i.e., within the light receiving areas152aand152bin Step S300.

That is, the micro-computer61adds the pixel signals of the same color in the column direction in the direction orthogonal to the pupil splitting direction denoted by a reference character X inFIG. 14in the focus detecting light receiving areas152aand152bof the CCD21. This adding process is carried out for the respective color elements of R, G and B. It is noted thatFIG. 14is a diagram conceptually showing the adding process in carrying out the focus detecting arithmetic operation.

The adding process is carried out as follows.

In the focus detecting light receiving area152aof the CCD21, data obtained by adding the R signals among the same color signals in the first column is R1L and data obtained by adding the G signals is G1L as shown in FIG.14. In the same manner, data obtained by adding the G signals among the same color signals in the second column is G2L and data obtained by adding the B signals is B1L.

The similar adding process is carried out also in the focus detecting light receiving area152bof the CCD21to obtain predetermined data in the same manner. Then, the data G1L, G2L, G3L, . . . may be obtained for the G signals on the side of the light receiving area152aand G1R, G2R, G3R, . . . may be obtained on the side of the light receiving area152b.In the same manner, the data R1L, R2L, R3L, . . . may be obtained for the R signals on the side of the light receiving area152aand R1R, R2R, R3R, . . . may be obtained on the side of the light receiving area152band the data B1L, B2L, B3L, . . . may be obtained for the B signals on the side of the light receiving area152aand B1R, B2R, B3R, . . . may be obtained on the side of the light receiving area152b.

Next, in Step S301, the micro-computer61carries out the general phase difference detecting operation per each color element of R, G and B by using the data of the same color added signal obtained in Step S300.

For instance, it carries out the phase difference detecting operation by the added data G1L, G2L, G3L, . . . on the light receiving area152aside and the added data G1R, G2R, G3R, . . . of the light receiving area152bside.

Then, the micro-computer61evaluates the reliability of the phase difference detecting operation in Step S301to judge whether or not it is possible to detect the focal point in Step S302.

Next, the micro-computer61selects the results of computation judged to be reliable and to be capable of detecting the focal point and carries out an averaging process.

Then, the micro-computer61calculates a defocusing amount from the above-mentioned calculation result in Step S304and returns the process to the main routine inFIG. 10(return).

According to the first embodiment described above, the focus detecting operation is carried out by providing the half-mirror section at the part of the main mirror14, by guiding the subject beams which have been transmitted through the half-mirror section to the focus detecting optical system30by the sub-mirror19and by irradiating the subject beam to the predetermined light receiving areas152aand152bin the image pickup area100of the CCD21via the focus detecting optical system30.

That is, the focusing detecting operation is carried out by utilizing the image pickup means by guiding the part of the subject beam to the predetermined position of the image pickup means without specifically providing image pickup means dedicated for the focus detecting operation. Accordingly, it allows the number of components of the electronic image pickup apparatus to be reduced. Thus, it contributes to the down-sizing of the apparatus and to the reduction of the production cost of the whole apparatus.

The following means may be adopted for the focus detecting computing process carried out in the electronic image pickup apparatus of the first embodiment described above.

FIG. 15is a conceptual diagram showing a modified example of the adding process of the focus detecting arithmetic operation carried out in the electronic image pickup apparatus of the first embodiment of the invention.

This modified example shows a case of carrying out a so-called culling reading of taking out only predetermined signals among image signals which may be obtained by the focus detecting light receiving areas152aand152b.

That is, the micro-computer61adds the same color signals in the focus detecting area, i.e., in the light receiving areas152aand152b,for example as shown in FIG.15. In this case, the culling reading of obtaining one image signal out of three same color signals in the column direction is carried out and the read image signals are added within the vertical shift register103.

This culling reading may be readily realized by controlling the operation of the vertical shift register103by controlling the reading clock when the CCD is applied as the image pickup device as the present applicant has disclosed in Japanese Patent Laid-Open No. Hei. 10-136244 for example.

It is noted that althoughFIG. 15only shows one light receiving area152a,the totally same process is carried out also in the other light receiving area152b.

The time for reading the whole pixel signals may be shortened by reading the pixel signals per predetermined intervals in the column direction and the computing speed may be readily quickened because the number of pixel signals handled of the operating process is reduced. Therefore, the focus detecting operation can be further quickened.

FIG. 16is a conceptual diagram showing another modified example of the adding process of the focus detecting arithmetic operation carried out in the electronic image pickup apparatus of the first embodiment of the invention.

The modified example shown inFIG. 16shows a different case of carrying out the culling reading of taking out only predetermined signals among the pixel signals which can be obtained by the focus detecting light receiving areas152aand152bin the same manner as with the case of FIG.15.

In this case, the culling reading of obtaining two pixel signals out of three predetermined pixel signals among the same color signals in the column direction is accomplished in the same manner as with the modified example described above. The pixel signals thus read are added within the vertical shift register103in the same manner as with the first embodiment and its modified example.

Such a process allows the reading time to be shortened and the computing speed to be quickened due to the reduction of the number of pixel signals to be read in the same manner as with the modified example described above.

Next, a second embodiment of the invention will be explained below.

FIG. 17is a diagram schematically showing the disposition of the main components of an electronic image pickup apparatus of a second embodiment of the invention together with optical paths within the electronic image pickup apparatus of beams which have been transmitted through a photographic optical system.FIG. 17corresponds toFIG. 1in the first embodiment and the components not related to the invention are omitted from the figure to simplify the figure.

The structure of the electronic image pickup apparatus of the present embodiment is basically the same as that of the first embodiment except for the structure of the focus detecting optical system.

A focus detecting optical system130of the present embodiment comprises a view field mask131, a field lens132, a first total reflection mirror133, a second total reflection mirror136, a pupil mask134, and an image reforming lens135as shown in FIG.17. The concept of the basic structure of the focus detecting optical system130is totally the same as that of the first embodiment (see FIGS.2and3).

It is noted that a total reflection mirror137is disposed behind the sub-mirror19in the present embodiment in order to guide the focus detecting beam outputted from the focus detecting optical system130to a predetermined position of the image pickup area of the CCD21. The total reflection mirror137is provided to guide the beam from the focus detecting optical system130located below to the CCD21disposed behind the electronic image pickup apparatus to form the image again on its light receiving plane by bending the optical path of the focus detecting beam from the focus detecting optical system130by reflecting it.

While the main mirror14and the sub-mirror19recede to the photographing position (the position of dashed line inFIG. 17) during the photographing operation also in the electronic image pickup apparatus, the total reflection mirror137also moves to the position where it will not block the subject beam, i.e., to the position indicated by a dashed line atFIG. 17, in the same time by a predetermined moving mechanism (not shown) to recede from the optical path of the subject beam.

In the focus detecting optical system130constructed as described above, the focus detecting beam is inputted to the CCD21almost vertically to form the focus detecting image again at the predetermined position of the image pickup area100. The view field mask images153aand153band the focus detecting light receiving areas152aand152bformed on the image pickup area100of the CCD21will not deform like those in the first embodiment as shown in FIG.18.

The other structure and operation of the electronic image pickup apparatus are almost the same as the electronic image pickup apparatus of the first embodiment.

It is noted that the total reflection mirror137also recedes to the outside of the optical path of the subject beam by the moving mechanism not shown at the same time when the main mirror14and the sub-mirror19recede to the outside of the optical path of the subject beam at the time of a photographing operation as described above in the present embodiment. It allows the whole subject beams which have been transmitted through the photographic optical system11to be irradiated to the image pickup area100of the CCD21.

As described above, the second embodiment allows the same effects as the first embodiment to be obtained, the problem of deformation of the image (seeFIG. 5) generated by the focus detecting optical system30in the electronic image pickup apparatus of the first embodiment to be eliminated and thus the focus detecting accuracy to be improved.

Next, a third embodiment of the invention will be explained below.

FIG. 19is a diagram showing the disposition of the main components of an electronic image pickup apparatus of a third embodiment of the invention together with optical paths within the electronic image pickup apparatus of beams which have been transmitted through the photographic optical system.FIG. 20is a perspective view showing the concept of the structure of the focus detecting optical system of the electronic image pickup apparatus and conceptually showing the state how the beams of the subject which have been transmitted through the photographic optical system arrive at the image pickup device via a focus detecting optical system230.

It is noted thatFIG. 19corresponds toFIG. 1in the first embodiment andFIG. 20corresponds toFIG. 3in the first embodiment. The components not related to the invention are omitted fromFIGS. 19 and 20to simplify the figure.

The structure of the electronic image pickup apparatus of the present embodiment is basically the same as that of the first embodiment except for the structure of the focus detecting optical system and except that a focal plane shutter is disposed on the whole plane of the CCD21.

The focus detecting optical system230of the present embodiment comprises a field mirror233, a pupil mask234, and an image reforming lens235as shown in FIG.19. The field mirror232is formed of a reflecting mirror having a reflecting plane at the inside of a concave plane. The field mirror232is what realizes the functions of the view field mask31, the field lens32and the total reflection mirror33comprising the focus detecting optical system30of the electronic image pickup apparatus of the first embodiment by one member.

The field mirror232is provided with a reflecting section232aof a predetermined range near the center of the reflecting plane A so as to be able to reflect only a partial beam among the beam from the sub-mirror19(not shown inFIG. 20) which has been transmitted through the photographic optical system11(not shown in FIG.20).

Because the field mirror232is formed of the reflecting mirror having the reflecting plane A at the inside of the concave plane as described above, only the predetermined beam condensed by the reflecting section232ais reflected. Accordingly, the optical path of the beam is changed by that and is guided to the CCD21side. Thus, the field mirror232realizes the functions of the view field mask31, the field lens32and the total reflection mirror33of the focus detecting optical system30in the first embodiment by one member.

Then, the beam reflected by the field mirror232is outputted from the focus detecting optical system230via the pupil mask234having two openings234aand234band the image reforming lens235comprised of two lenses235aand235b.

The focus detecting beam outputted from the focus detecting optical system230as described above is inputted to the predetermined light receiving areas152aand152bof the image pickup area100of the CCD21as shown in FIG.20.

Meanwhile, the focal plane shutter22which is a mechanical shutter mechanism is disposed in front of the CCD21. The focal plane shutter22comprises a front sheet23, a rear sheet24and other elements (not shown) similarly to what is applied to a single-lens reflex camera in general and carries out an exposing operation by a slit formed between the front sheet23and the rear sheet24.

When the focusing detecting operation is carried out, i.e., when the electronic image pickup apparatus is in the photographing preparing state, the main mirror14is positioned as indicated by a solid line in FIG.19and the front sheet23is disposed at the position where it is released. Thereby, only the focus detecting beam is inputted to the predetermined light receiving areas152aand152bof the image pickup area100(seeFIG. 20) of the CCD21.

The light inputted to the part other than the predetermined light receiving areas152aand152bof the image pickup area100of the CCD21is blocked by the total reflection mirror section of the main mirror14, i.e., by the area other than the half-mirror section corresponding to the sub-mirror19, as in the first embodiment. Accordingly, only the focus detecting beam is inputted to the predetermined light receiving areas152aand152bof the image pickup area100(seeFIG. 20) of the CCD21when the focus detecting operation is carried out.

When the photographing operation is carried out, the main mirror14and the sub-mirror19recede to the position (the photographing position) indicated by the dashed line in FIG.19and the focal plane shutter22is charged by the action of a mechanical charging mechanism (not shown) so as to set the front sheet23.

Then, as a result of computing processes by the photometry and exposure computing section45, the front sheet23and the rear sheet24are driven based on information of calculated shutter seconds to thus execute the main exposing operation.

Further, although the stopping member11bhas been completely closed to block the beam to the CCD21in reading the pixel data of the CCD21carried out after the main exposing operation in the electronic image pickup apparatus of the first embodiment described above, the stopping member11bplays a role of only stopping function of restricting the input beam to the photographic optical system11by keeping the diaphragm opening because the light blocking state of the CCD21may be maintained by the focal plane shutter22disposed on the whole plane of the CCD21.

The other structure is almost the same as that of the electronic image pickup apparatus of the first embodiment. The action thereof is also the same as that of the first embodiment except that the action of the focal plane shutter22described above is added and the light blocking operation of the stopping member11bbecomes unnecessary.

As described above, the third embodiment allows the same effects as the first embodiment to be obtained. In addition to that, the functions realized by the view field mask31, the field lens32and the total reflection mirror33of the focus detecting optical system30in the electronic image pickup apparatus of the first embodiment are achieved by one member of the field mirror232in the focus detecting optical system230of the electronic image pickup apparatus of the third embodiment, so that the third embodiment allows a number of members comprising the focus detecting optical system230to be reduced and the structure thereof to be simplified. Accordingly, it contributes to the reduction of the production cost of the whole electronic image pickup apparatus.

Further, because the light blocking state of the CCD21is maintained by the focal plane shutter22disposed on the whole plane of the CCD21in reading pixel data of the CCD21carried out after the main exposing operation, the stopping member11bcarries out only the operation of restricting the beam from entering the photographic optical system11by keeping the diaphragm opening. Accordingly, the third embodiment allows the control sequence of the diaphragm driving section63for driving the stopping member11bto be simplified further.

Next, a fourth embodiment of the invention will be explained.

FIG. 21is a diagram showing the disposition of the main components of an electronic image pickup apparatus of the fourth embodiment of the invention together with optical paths within the electronic image pickup apparatus of beams which have been transmitted through the photographic optical system andFIG. 22is a perspective view showing the structural concept of the focus detecting optical system of the electronic image pickup apparatus and conceptually showing the state how the beams of the subject which have been transmitted through the photographic optical system arrive at the CCD21via the focus detecting optical system330.

It is noted thatFIG. 21corresponds toFIG. 1in the first embodiment andFIG. 22corresponds toFIG. 3in the first embodiment. The components not related to the invention are omitted fromFIGS. 21 and 22to simplify the figures.

The structure of the electronic image pickup apparatus of the present embodiment is basically the same as that of the first embodiment except for the structure of the focus detecting optical system.

The focus detecting optical system330of the present embodiment comprises a view field mask331, a field lens332, a first total reflection mirror333, a second total refection mirror336, and an image reforming lens235as shown in FIG.21. The image reforming mirror335comprises mirrors335aand335bwhich are two concave reflecting mirrors having the total reflection plane at the inside. The image reforming mirror335has the functions of the pupil mask34and the image reforming lens35comprising a part of the focus detecting optical system30in the electronic image pickup apparatus of the first embodiment.

A reflecting section of a predetermined range is provided in the vicinity of the center of each reflecting plane of the two mirrors335aand335bof the image reforming mirror335similarly to the field mirror232of the focus detecting optical system230in the electronic image pickup apparatus of the third embodiment described above. Accordingly, it has the function of the pupil mask34of the focus detecting optical system30in the first embodiment. At the same time, the image reforming mirror335has the function of the image reforming lens35for forming a predetermined image again by condensing the beam by the condensing and reflecting actions of the concave reflecting mirror.

The other structure and operation are almost the same as those of the electronic image pickup apparatus of the first embodiment.

It is noted that the optical path of the focus detecting beam which has been guided from the sub-mirror19to the focus detecting optical system330follows the following path when the focus detecting operation is carried out in the present embodiment.

That is, the focus detecting subject beams which have been transmitted through the photographic optical system11and which have been guided from the sub-mirror19to the focus detecting optical system330is restricted by the view field mask331as a beam of predetermined quantity. After passing it, the beam is condensed by the field lens332and is reflected by the reflecting plane of the first total reflection mirror333. Thereby, the optical path is changed and the beam is guided to the second total reflection mirror336. Then the beam is reflected again by the second total reflection mirror336and changes the optical path, and is guided to the image reforming mirror335.

Each beam inputted to the two mirrors335aand335bof the image reforming mirror335are reflected by the respective reflecting planes and two images are irradiated to the two predetermined light receiving areas152aand152bto form a predetermined image. Then, the focus detecting operation is executed based on the two images.

The other structure and operation are almost the same as that of the electronic image pickup apparatus of the first embodiment.

The fourth embodiment allows the same effects as the first embodiment to be obtained as described above.

Further, although there has been a problem such as a dislocation of the images by being influenced by aberration caused due to the lenses35aand35bin the focus detecting optical system30of the electronic image pickup apparatus of the first embodiment because the beams which have passed through the two openings34aand34bof the pupil mask34are formed again by the two lenses35aand35bof the image reforming lens35, such problem may be solved by realizing the functions of the pupil mask34and the image reforming lens35of the focus detecting optical system30of the electronic image pickup apparatus of the first embodiment by the image reforming mirror335. Accordingly, a highly accurate focus detecting operation may be readily realized.

While the preferred embodiments have been described, it is apparent that the invention is not limited thereto but may be otherwise variously embodied within the spirit and scope of the invention. The scope of the invention is therefore to be determined solely by the appended claims.