Abstract:
A zoom lens camera records an image to be photographed. A zoom switch is operated to drive a zoom lens of the camera. The zoom lens is driven in response to the operation of the zoom switch, and is controlled so that the zoom lens and the image recorder are alternately activated when the operation of the zoom lens and the operation of the image recorder are simultaneously instructed.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a zoom lens camera having a power zoom function. 
     2. Description of Related Art 
     Electronic still cameras (i.e., still video cameras), have becomes available in recent years. In these cameras, the image of one frame (one field) is recorded on one track of a magnetic disk. Accordingly, the magnetic disk is controlled so that it makes one revolution at the period of one field (i.e., 1/60 sec. according to NTSC). 
     Since the magnetic disk, which serves as a recording medium, is rotated at such a high speed, a large number of frames can be photograph in quick succession (i.e., continuous shooting mode), such as, 1, 2 or 5 frames per second, for a desired period of time. 
     By combining this continuous shooting mode with zooming, a series of images, which is gradually enlarged or reduced, can be photographed. 
     However, the conventional electronic still cameras suffer from the problem that when the continuous shooting mode and zooming are to be simultaneously executed, as described above, a series of recording operation is carried out while the zoom lens is being moved, and consequently, associated elements, such as an imaging circuit, recording circuit, aperture motor, tracking motor, spindle motor, etc., are simultaneously activated, resulting in an increase in the peak current consumed. 
     Accordingly, the load on the power supply circuit increases and the rated capacity thereof must be increased, which results in an increase in the over-all size of the camera and a rise in the cost of manufacture. 
     SUMMARY OF THE INVENTION 
     In view of these circumstances, it is an object of the present invention to enable the zooming mode and the continuous photographing (shooting) mode to be simultaneously executed without increasing the overall size and cost of the camera. 
     The zoom camera of the present invention comprises a device for recording a photographed image on a recording medium, a zoom switch which is operated to drive a zoom lens; a drive mechanism for driving the zoom lens in response to the operation of the zoom switch and a controller for controlling, when two instructions are simultaneously given to drive the zoom lens and effect recording with the recording device, the zoom driving mechanism and the recording device such that the zoom lens and the recording device are alternately activated. 
     In the zoom camera having the above-described arrangement, when the continuous shooting (photographing) mode, for example, is set, a series of frames is shot at a rate of a predetermined number of frames per second, as long as the release switch is turned ON, and the photographed images are successively recorded on a recording medium, such as, a magnetic disk. 
     If the zoom switch, which comprises, for example, a TELE or WIDE switch, is ON during this photographing operation, the zoom lens is driven in either the TELE or WIDE direction by the zoom driving mechanism, which comprises, for example, a zoom motor. 
     The movement of the zoom lens and the recording operation are alternately carried out. In other words, for example, movement of the zoom lens is suspended after being moved for a predetermined time. While the zoom lens is at rest, recording on the recording medium, shift of tracks from one to another, etc. are conducted. After completion of a series of recording operations, the movement of the zoom lens is resumed. The described operation is then repeated. 
     Accordingly, the movement of the zoom lens and the recording operation are not simultaneously executed and it is therefore possible to minimize the peak power consumption of the apparatus. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described below in detail with reference to the accompanying drawings, in which: 
     FIG. 1 is a block diagram showing an arrangement of one embodiment in which a zoom camera of the present invention is applied to an electronic still camera; 
     FIG. 2 is a flowchart showing a release process used in the embodiment shown in FIG. 1; and 
     FIG. 3 is a flowchart showing more detailed processing steps in the zoom processing shown in FIG. 2. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a block diagram showing the arrangement of one embodiment in which the zoom camera of the present invention is applied to an electronic still camera. 
     A zoom lens 2, through which light from an object passes, falls upon an imaging device 4 (such as a CCD,) after passing through an aperture 3 is provided. 
     The zoom lens 2 is driven by a zoom motor 5, which is driven by a zoom driving circuit 6. The aperture 3 is driven by an aperture motor 7, which is driven by an aperture driving circuit 8. 
     An imaging circuit 9 reads out an image signal from the imaging device 4 and transmits its output signal to a signal processing circuit 10. An encoder 11 encodes the output from the signal processing circuit 10 into an NTSC television signal, for example, and supplies it to a monitor (TV) 12. 
     A recording circuit 13 records a signal that is outputted from the signal processing circuit 10 onto a magnetic disk 15 through a magnetic head 14. 
     A spindle motor driving circuit 16 drives a spindle motor 17, which rotates the magnetic disk 15. A tracking motor driving circuit 18 drives a tracking motor 19, which moves the magnetic head 14. 
     A track detecting circuit 20 detects a level, such as a DPSK signal, control code signal, etc. from a reproduced signal that is outputted from the magnetic head 14, and outputs the detected information to a microcomputer 22, which serves as a control means. 
     A photometric circuit 21 measures light from the object 1 and outputs the result of the photometry to the microcomputer 22. 
     A TELE switch 23 and a WIDE switch 24 are operated to move the zoom lens 2 in the TELE direction and the WIDE direction, respectively. A mode change over switch 25 is operated to set various photographing modes. A release switch 26 is operated to effect a series of recording operations (e.g., photometry, exposure computation, aperture drive, imaging device exposure, reading, recording, track shift, etc.). 
     The release switch 26 comprises, for example, a two-stage switch which is arranged such that when the first-stage switch is turned ON, photometry, distance measurement and exposure computation are executed, and when the second-stage switch is turned ON, the following image recording operation is initiated. 
     A power supply circuit 27 has a battery therein to supply necessary electric power to the circuits, means, etc. 
     An optical finder 28, which is used to identify the object 1, has a light-receiving element 29 therein for photometry. 
     The operation will next be explained with reference to flowcharts shown in FIGS. 2 and 3. 
     Light from the object 1 enters the imaging device 4 through the zoom lens 2 and the aperture 3. A signal that is produced in the imaging device 4 through photoelectric conversion is read out to the imaging circuit 9 and then inputted to the signal processing circuit 10. The signal processing circuit 10 processes the input signal into a signal which is conformable to the format of the electronic still camera. 
     When the monitor mode is set through the mode change over switch 25, the signal that is processed in the signal processing circuit 10 is inputted to the encoder 11, in which it is converted into a signal conformable to the NTSC format, for example, and the converted signal is then outputted to the monitor 12. In this way, object 1 can be monitored through the monitor 12. 
     Meantime, the photometric circuit 21 measures the light from the object 1 on the basis of the output from the light-receiving element 29 and outputs the result of the photometry to the microcomputer 22. The microcomputer 22 computes the signal that is inputted thereto from the photometric circuit 21 to determine a correct exposure quantity. The aperture driving circuit 8 drives the aperture motor 7 in accordance with the exposure quantity. Thus, the aperture 3 is moved to a position where a given exposure is obtained. 
     Accordingly, the display 12 always displays an image with a correct exposure. 
     In this way, object 1 is monitored through the monitor 12, and release switch 26 is turned ON at a given timing. Thus, the microcomputer 22 controls the zoom driving circuit 6 to suspend the zoom motor 5 (steps S1 and S2). Next, the microcomputer 22 computes an exposure quantity on the basis of the output from the photometric circuit 21 and controls the aperture driving circuit 8 in accordance with the result of the computation. 
     The aperture motor 7 is driven by the aperture driving circuit 8 to move aperture 3 to a position corresponding to the computed value (steps S3 and S4). 
     Meanwhile, a signal that is outputted from the imaging device 4 is inputted to the signal processing circuit 10 through the imaging circuit 9. The signal, which is converted into a signal conformable to the format of the electronic still camera in the signal processing circuit 10, is inputted to the recording circuit 13, where it is frequency-modulated. The signal is then supplied to the magnetic head 14. In the meantime, microcomputer 22 drives the spindle motor 17 through the spindle motor driving circuit 16 to rotate the magnetic disk 15 at a speed of 3,600 rpm. Accordingly, an image of one frame (one field) is recorded on a given track of the magnetic disk 15 (step S5). 
     Upon completion of this recording, microcomputer 22 drives the tracking motor 19 through the tracking motor driving circuit 18 to move the magnetic head 14 inwardly to the next track on the magnetic disk 15 (step S6). Then, a signal is reproduced from this track. The reproduced signal is inputted to the track detecting circuit 20 from the magnetic head 14. The track detecting circuit 20 detects and outputs a level of the reproduced signal to microcomputer 22. 
     Microcomputer 22 judges, from the signal that is inputted thereto from the track detecting circuit 20, whether another image signal has already been recorded on the track concerned. If another image signal has already been recorded on track, the magnetic head 14 is moved to a subsequent vacant track. In this way, it is checked whether image data is recordable on a track where the magnetic head 14 is placed (step S7). 
     After the completion of a series of recording operations, it is determined whether the continuous shooting mode is set. If the continuous shooting mode is not set through the mode changeover switch 25, the photographing operation is ended with the operations described above (step S8). 
     If the continuous shooting (photographing) mode is set, microcomputer 22 instructs its built-in timer to start a timing operation (step S8 and S9). 
     Even when the timer is performing a timing operation, if release switch 26 has already been turned OFF, the photographing operation is ended (step S10). If the release switch 26 is still ON, the zoom processing is executed (step S11). 
     More specifically, if the TELE switch 23 is ON and a TELE limit switch (not shown) is OFF microcomputer 22 drives the zoom motor 5 through the zoom driving circuit 6 to move the zoom lens 2 in the TELE direction (steps S21, S22 and S23). 
     If the TELE switch 23 is OFF, it is determined whether the WIDE switch 24 is ON (steps S21 and S24). If the WIDE switch 24 is ON and a WIDE limit switch (not shown) is OFF, the zoom lens 2 is moved in the WIDE direction (S25 and S26). 
     Whenever the zoom lens is moved, i.e., in the TELE direction or the WIDE direction, the drive of related the zoom motor 5 is suspended when the limit switch turns ON (steps S22, S25 and S27). 
     This zoom processing is carried out until the timer finishes counting a predetermined time, which has been set in advance. After the predetermined time has elapsed, the processing of step S2 and those following it are repeated (step S12). 
     More specifically, in this embodiment, when both the continuous shooting mode and the zooming mode are instructed to be executed, a series of recording operations, i.e., photometry, exposure, recording, tracking, and track content processing, is conducted while the zoom lens 2 is at rest. 
     After completion of these recording operations, the zoom lens 2 is moved again for a predetermined time. In this way, the movement of the zoom lens and the recording operation are alternately conducted. 
     It should be noted that the movement of the zoom lens and a series of recording operations are conducted at different times, as described above, not only when the continuous shooting mode and the zooming mode are combined together but also when another mode, e.g., the single AF mode, and the zooming mode are combined together. 
     Although the present invention has been described by way of an example in which it is applied to an electronic still camera, it should be noted that the present invention is also applicable to ordinary cameras which are designed to effect photographic recording on film. In such a case, the movement of the zoom lens and a recording operation, which includes the movement of a film that serves as a recording medium, are alternately conducted. 
     As has been described above, the zoom camera of the present invention is arranged such that the movement of the zoom lens and a series of recording operations are alternately conducted. It is therefore possible to minimize the peak power consumption of the apparatus. As a result, the power supply circuit can be reduced in terms of both the capacity and configuration, so that it is possible to reduce the overall size of the apparatus and make the camera compact for the carrying convenience. In addition, the manufacturing cost is also lowered.