Video camera for camera system

Abstract: A video camera having a zoom function and a camera system are provided, wherein a ratio of view fields of the video camera and a photographic camera is calculated based on information about zooming powers of imaging lenses, and an image frame of the photographic camera is displayed in a variable size at an electronic viewfinder in accordance with the ratio of the view fields and based on a picked-up image of fixed size, or a picked-up image is displayed in a variable size on the basis of the image frame of the photographic camera. View angles of the video camera and the photographic camera are obtained from the information about the zooming powers of the imaging lenses, and zoom adjustment is carried out with the view angles coinciding with each other, or the zooming power of one of the video camera and the photographic camera is adjusted such that the view angles become equal to each other. Accordingly, the view field of the photographic camera can be accurately recognized even if the zooming power is changed.

Description: BACKGROUND OF THE INVENTION This invention relates to a video camera having a zoom function and including an electronic viewfinder. Using a video camera permits both a still image and a dynamic image to be obtained. Since the resolution of video cameras is lower than that of photographic cameras (film cameras), there is a demand for a combined use of a video camera and a photographic camera. For example, a photographic camera may be firmly fixed to a video camera so that the shutter of the photographic camera can be operated while a dynamic image is recorded by the video camera. In the US-A-4,148,072 a camera system is disclosed which includes a photographic camera of the still or motion picture type with an adjustable lens system and a TV camera with a fixed lens system. whereby the object angle of the photographic camera is less than or equal to the object angle of the TV camera. In this system, a circuit is provided to define the variable object field of the photographic camera by a luminous frame on a monitor screen also displaying the fixed object field of the TV camera. The JP-A-1-013 530 discloses a visual field expanded type camera for finder wherein the photographic range of a camera having a zoom lens is confirmed in a video picture of a video camera having a fixed focal length. In video cameras having a zoom function, the angle of view of a picked-up image changes as the zooming power is changed. This is the case with photographic cameras having a zoom function. Accordingly, when operating the shutter of the photographic camera while viewing an electronic viewfinder of the video camera, the field of view of the photographic camera cannot be accurately recognized, and thus the shutter cannot be correctly released. An object of this invention is, therefore, to provide a video camera which permits the view field of a photographic camera to be accurately recognized even if the zooming power is changed. SUMMARY OF THE INVENTION The invention is defined in appended claim 1. According to this invention, the image frame of the photographic camera is displayed at the electronic viewfinder on the basis of a picked-up image of fixed size. Accordingly, the view field of the photographic camera can be accurately recognized, whereby the user can correctly operate the shutter of the photographic camera while viewing the display screen of the electronic viewfinder. The objects, advantages and novel features of the present invention will be apparent from the following detailed description when read in conjunction with the appended claims and attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an external appearance of an embodiment according to this invention; FIG. 2 is a block diagram showing the arrangement of a video camera section; FIG. 3 is a schematic diagram showing a color coding of an imaging device; FIG. 4 is a diagram showing an output of a horizontal output register of the imaging device; FIG. 5 is a diagram illustrating a chrominance signal processing; FIG. 6 is a diagram also illustrating the chrominance signal processing; FIG. 7 is a schematic diagram showing the arrangement of a zoom driver; FIG. 8 is a graph showing the relationship between a zoomed view angle and a detection signal; FIG. 9 is a diagram illustrating a procedure for obtaining an angle of view; FIG. 10 is a diagram showing an image plane size of a 1/3-inch CCD solid-state imaging device; FIG. 11 is a diagram showing an image plane size of a 35 mm film; FIG. 12 is a diagram showing fields of view (horizontal direction) of a picked-up image and a photographic camera; FIG. 13 is a diagram showing fields of view (vertical direction) of the picked-up image and the photographic camera; FIG. 14 is a flowchart showing an image frame data output process; FIG. 15 is a diagram showing a display screen of an electronic viewfinder; FIG. 16 is a block diagram showing the arrangement of a video camera section; FIG. 17 is a schematic diagram showing the arrangement of a zoom driver; FIG. 18 is a graph showing the relationship between the zoomed view angle and a detection signal; FIG. 19 is a schematic diagram showing the arrangement of a zoom driver; FIG. 20 is a graph showing the relationship between the zoomed view angle and a detection signal; FIG. 21 is a diagram showing the view fields (horizontal direction) of a picked-up image and a photographic camera; FIG. 22 is a diagram showing the view fields (vertical direction) of the picked-up image and the photographic camera; FIG. 23 as is a flowchart showing an image frame data output process; FIG. 24 is a diagram showing a display screen of an electronic viewfinder; DETAILED DESCRIPTION OF THE INVENTION One embodiment of this invention will be described with reference to the drawings. The embodiment comprises an integral combination of a video camera and a photographic camera. FIG. 1 is a perspective view showing an entire arrangement, wherein reference numeral 1 denotes a cabinet which has a built-in video camera section including an imaging device, a signal processing circuit, etc., and a built-in photographic camera section including a film loading mechanism, a film drive mechanism, etc., none of which are shown. Reference numeral 2 denotes an imaging lens of the video camera section, and 3 denotes an imaging lens of the photographic camera section. The optical system for the video camera section is separate from that for the photographic camera section. A 6-power zoom lens having a focal length f of 7 to 42 mm is used for the imaging lens 2, and a fixed-focus lens having a focal length f of 55 mm is used for the imaging lens 3. In this embodiment, an electronic viewfinder comprising a small-sized CRT is arranged in the cabinet 1, for displaying an image picked up by the video camera section through the imaging lens 2. Reference numeral 4 represents an eyecup. There is provided no finder permitting a direct observation of an image to be photographed by the photographic camera section through the imaging lens 3. Further, 5T and 5W denote zoom buttons for a zooming operation in a TELE direction and a WIDE direction, respectively, 6 denotes a record button for recording a video signal output from the video camera section in a VTR, 7 denotes a shutter button of the photographic camera section, and 8 denotes a film rewind button. FIG. 2 is a block diagram showing the arrangement of the video camera section. An image light from an object enters through the imaging lens 2 and an iris 11 and falls upon a single-plate CCD solid-state imaging device 12 having a complementary checkered color filter. FIG. 3 is a schematic diagram showing a color coding of the imaging device 12, and as illustrated, a field readout is carried out. In A field, charges are mixed in pairs, such as a pair of A1 and A2, and in B field, charges are mixed in pairs such as a pair of B1 and B2. For the A field, charges are output in the order of A1, A2, ..., and for the B field in the order of B1, B2, ..., from a horizontal shift register Hreg. As shown in FIG. 4, the order of charges a, b, ..., is (Cy + G), (Ye + Mg), ... in A1 line, (Cy + Mg), (Ye + G), ... in A2 line, (G + Cy), (Mg + Ye), ... in B1 line, and (Mg + Cy), (G + Ye), ... in B2 line. The charges output from the imaging device 12 in the aforementioned manner are supplied to a CDS circuit (correlation double sampling circuit) 13 and are extracted thereby to obtain an image signal. By using the CDS circuit 13, it is possible to reduce reset noise, as is known in the art. Timing pulses needed by the imaging device 12 and the CDS circuit 13 are produced by a timing generator 14. The timing generator 14 is supplied with reference clock pulses CK0 at 8 fsc (fsc represents the color subcarrier frequency) from an oscillator 15, as well as horizontal and vertical synchronizing signals HD and VD from a synchronizing generator 16. The synchronizing generator 16 is supplied with clock pulses CK1 at 4 fsc from the timing generator 14. An image signal output from the CDS circuit 13 is supplied to a level detecting circuit 17, which outputs a signal to an iris driver 18. The iris driver 18 automatically controls the aperture of the iris 11. A process for obtaining a luminance signal Y and a chroma signal (color differential signal) from the image signal output from the CDS circuit 13 will be explained. The luminance signal Y is obtained by adding adjacent signals together. Namely, referring to FIG. 4, summation signals are produced in the sequence of a + b, b + c, c + d, d + e, .... For example, the A1 line can be approximated as shown in the following equation: Y = {(Cy + G) + (Ye + Mg)} x 1/2 = (2B + 3G + 2R) x 1/2 where Cy = B + G, Ye = R + G, and Mg = B + R. The A2 line can be approximated as follows: Y = {(Cy + Mg) + (Ye + G)} x 1/2 = (2B + 3G + 2R) x 1/2 The other lines in the A field and the lines in the B field can be approximated in a similar manner. The chroma signal is obtained by subjecting adjacent signals to a subtraction. For example, the A1 line can be approximated as shown in the following equation: R - Y = (Ye + Mg) - (Cy + G) = (2R - G) The A2 line can be approximated as follows: -(B - Y) = (Ye + G) - (Cy - Mg) = -(2B - G) Similarly, for the other lines in the A field and the lines in the B field, a red differential signal R - Y and a blue differential signal -(B - Y) are alternately derived in a line sequential manner. Referring again to FIG. 2, the image signal output from the CDS circuit 13 is supplied to a low-pass filter 20 constituting a luminance processing unit through an AGC circuit 19. The low-pass filter 20 carries out an addition (averaging) of adjacent signals, and accordingly, a luminance signal Y is output therefrom. The image signal output from the AGC circuit 19 is supplied to sample holding circuits 21 and 22 forming a chroma processing unit. The sample holding circuits 21 and 22 are supplied with sampling pulses SHP1 and SHP2 (shown in FIGS. 5 and 6 at E and F), respectively, from the timing generator 14. The sample holding circuit 21 outputs a continuous signal S1 of (Cy + G) or (Cy + Mg) to a subtracter 23 (see B of FIGS. 5 and 6), and the sample holding circuit 22 outputs a continuous signal S2 of (Ye + Mg) or (Ye + G) to the subtracter 23 (see C of FIGS. 5 and 6). The subtracter 23 subtracts the signal S1 from the signal S2, whereby a red differential signal R - Y and a blue differential signal -(B - Y) are alternately output therefrom in a line sequential manner (as shown at D in FIGS. 5 and 6). The color differential signals output from the subtracter 23 are supplied directly to a fixed terminal b of a changeover switch 24 and a fixed terminal a of a changeover switch 25, and also supplied to a fixed terminal a of the changeover switch 24 and a fixed terminal b of the changeover switch 25 via a delay circuit 26 having a delay time corresponding to one horizontal period. The switching operation of the changeover switches 24 and 25 is controlled by a controller 27. Specifically, the switches connect to the respective terminals b during a horizontal period in which the red differential signal R - Y is output from the subtracter 23, and connect to the respective terminals a during a horizontal period in which the blue differential signal -(B - Y) is output. The controller 27 is supplied with the synchronizing signals HD and VD as reference synchronizing signals from the synchronizing generator 16, and the clock pulses CK1 from the timing generator 14. Since the changeover switches 24 and 25 are operated in the aforementioned manner, a red differential signal R - Y is output from the changeover switch 24 in each horizontal period and a blue differential signal -(B - Y) is output from the changeover switch 25 in each horizontal period. The luminance signal Y output from the low-pass filter 20 and the color differential signals (R - Y) and -(B - Y) output from the changeover switches 24 and 25 are supplied to an encoder 28. The encoder 28 is further supplied with a composite synchronizing signal SYNC, a blanking signal BLK, a burst flag signal BF, and a color subcarrier signal SC from the synchronizing generator 16. In the encoder 28, as is conventionally known, the luminance signal Y is combined with the synchronizing signal SYNC, and the color differential signals are subjected to quadrature two-phase modulation to form a carrier chrominance signal C and further combined with a color burst signal. The luminance signal Y and the carrier chrominance signal C are added together to form, e.g., a color video signal SCV according to the NTSC system. The color video signal SCV thus generated by the encoder 28 appears at an output terminal 29. The encoder 28 also generates a monochromatic video signal SV (i.e., the luminance signal Y combined with the synchronizing signal SYNC), which is supplied to an electronic viewfinder 30 through an adder 31. Thus, a picked-up image is displayed at the small-sized CRT constituting the electronic viewfinder 30. The zooming power of the imaging lens 2 is adjusted by a zoom driver 41. FIG. 7 shows in detail the arrangement of the zoom driver 41, wherein reference numeral 411 denotes a lens constituting the imaging lens 2 for adjusting the zooming power. The lens 411 can be moved back and forth when rotated, whereby the zooming power is adjusted. For example, if the lens 411 is rotated in a direction T, the zooming power changes in the TELE direction; if the lens is rotated in a direction W, then the zooming power changes in the WIDE direction. The lens 411 is rotated by a DC motor 412, which is connected to output terminals q1 and q2 of a zoom driver unit 413. Input terminals p1 and p2 of the zoom driver unit 413 are respectively connected to fixed terminals T and W of a zoom switch 42. In this arrangement, when a high-level "H" signal is supplied to the terminal p1, a current flows through the motor 412 from the terminal q1 to the terminal q2 (as indicated by the solid line), and the lens 411 is rotated in the direction T. On the other hand, when a high-level "H" signal is supplied to the terminal p2, a current flows through the motor 412 from the terminal q2 to the terminal q1 (as indicated by the dashed arrow), and the lens 411 is rotated in the direction W. When neither the terminal p1 nor the terminal p2 is supplied with a high-level "H" signal, no current flows through the motor 412, and accordingly, the lens 411 is not rotated in either direction and the position thereof remains unchanged. A movable terminal of the zoom switch 42 is connected to a power supply terminal. When the operating button 5T or 5W of the aforementioned cabinet 1 is pressed, the zoom switch 42 is connected to the terminal T or W, and a high-level "H" signal is supplied to the terminal p1 or p2 of the zoom driver unit 413, whereby the zooming power is adjusted in the TELE or WIDE direction. Further, as shown in FIG. 2, a variable resistor 44 constituting a potentiometer is arranged at a location where the lens 411 of the imaging lens 2 is mounted. The variable resistor 44 is constructed such that the position of a movable terminal thereof is shifted with a rotation of the lens 411, whereby a voltage corresponding to the zooming power builds up at the movable terminal and is applied to the controller 27 as a detection signal SD. As shown in FIG. 8, the detection signal SD is set such that it is 1 V at the WIDE end (f = 7 mm) and 4 V at the TELE end (f = 42 mm). In this embodiment, a picked-up image is displayed at a fixed position on the screen of the small-sized CRT of the electronic viewfinder 30, and at the same time an image frame of the photographic camera is displayed on the same screen. The angle of view of a picked-up image changes in accordance with the zooming power, and thus the view field thereof changes accordingly. To display an image frame of the photographic camera on the screen of the small-sized CRT, the ratio of the view fields of the photographic camera and the picked-up image must be obtained. Here, the angle of view will be explained with reference to FIG. 9. The angle of view, , can be obtained from an image plane size T and the value f (focal length), as shown in equation (1) below. In FIG. 9, T' denotes the view field, and L denotes the distance to an object.  = 2tan -1 T/2f The imaging lens 2 is a 6-power zoom lens having a focal length f of 7 to 42 mm, and where the imaging device 12 is a 1/3-inch type, the image plane having a horizontal size ZH of 4.9 mm, a vertical size ZV of 3.69 mm, and a diagonal size ZD of 6.13 mm (see FIG. 10). Therefore, angles ZH, ZV and ZD of view in the horizontal, vertical and diagonal directions at the WIDE end (f = 7 mm) are 38.6°, 29.5°, and 47.3°, respectively, and angles ZH, ZV and ZD of view in the horizontal, vertical and diagonal directions at the TELE end (f = 42 mm) are 6.7°, 5.0°, and 8.3°, respectively. The imaging lens 3 is a fixed-focus lens having a focal length f of 55 mm, and where the film used is a 35 mm type, the image plane having a horizontal size PH of 36 mm, a vertical size PV of 24 mm, and a diagonal size PD of 43.3 mm (see FIG. 11). Therefore, angles PH, PV and PD of view in the horizontal, vertical and diagonal directions are 36.2°, 24.6°, and 43.0°, respectively. From the above, the relationship between the angles of view of the imaging lens 2, which is a zoom lens, and the angles of view of the imaging lens 3, which is a fixed-focus lens, can be summarized as shown in Table 1 below. Picked-up image WIDE - TELE Photographic camera Horizontal direction ZH = 38.6 to 6.7° PH = 36.2° Vertical direction ZV = 29.5 to 5.0° PV = 24.6° Diagonal direction ZD = 47.3 to 8.3° PD = 43.0° The ratio of the view fields of the photographic camera and picked-up image will be now explained. From FIG. 9, the view field T' is given by the following equation (2): T' = 2Ltan/2 Provided that the distances L from an object to both the imaging lenses 2 and 3 of the video camera section and the photographic camera section are the same, the view field ratio is found to vary as a function of view angle . From the horizontal and vertical view angles ZH and ZV of the picked-up image shown in Table 1, view fields T'ZH and T'ZV in the horizontal and vertical directions at the WIDE end are 0.7L and 0.53L, respectively, and view fields T'ZH and T'ZV in the horizontal and vertical directions at the TELE end are 0.12L and 0.09L, respectively. View angles ZH and ZV of the picked-up image at any point between the WIDE and TELE ends can be obtained from the detection signal SD, using the following equations (3): ZH = 38.6° - (38.6° - 6.7°)(SD - 1)/3 ZV = 29.5° - (29.5° - 5.0°)(SD - 1)/3 By substituting the view angles ZH and ZV obtained by equations (3) individually for  in equation (2), the view fields T'ZH and T'ZV can be obtained. From the horizontal and vertical view angles PH and PV of the photographic camera shown in Table 1, view fields T'PH and T'PV in the horizontal and vertical directions are 0.65L and 0.44L, respectively. Based on the foregoing, the relationship between the view fields of the picked-up image and those of the photographic camera can be summarized as shown in Table 2 below. FIG. 12 shows the relationship of the horizontal view fields, and FIG. 13 shows the relationship of the vertical view fields. Picked-up image WIDE - TELE Photographic camera Horizontal direction T'ZH = 0.7L to 0.12L T'PH = 0.65L Vertical direction T'ZV = 0.53L to 0.09L T'PV = 0.44L Table 3 shows view field ratios T'PH/T'ZH and T'PV/T'ZV in the horizontal and vertical directions, respectively. Picked-up image WIDE - TELE View field ratio T'PH/T'ZH in horizontal direction 0.93 to 5.42 View field ratio T'PV/T'ZV in vertical direction 0.83 to 4.89 From FIG. 9, the view field T' can also be obtained as shown in equation (4). T' = L x T/f The focal length f can be obtained from the detection signal SD, using the following equation (5): f = 7 mm + (42 mm - 7 mm)(SD - 1)/3 The focal length f, obtained by equation (5), is substituted into equation (4) and the horizontal and vertical sizes ZH and ZV of the image plane are substituted individually for T in equation (4), whereby the horizontal and vertical view fields T'ZH and T'ZV are obtained. Referring again to FIG. 2, the controller 27 generates image frame data Dm for displaying the image frame of the photographic camera at a position corresponding to the horizontal and vertical view field ratios T'PH/T'ZH and T'PV/T'ZV. FIG. 14 is a flowchart showing an image frame data output process executed by the controller 27. First, the focal length f is computed from the detection signal SD, using equation (5) (Step 51). Subsequently, the focal length f is substituted into equation (4), and the horizontal and vertical sizes ZH and ZV of the image plane are substituted individually for T in equation (4), to thereby obtain horizontal and vertical view fields T'ZH and T'ZV of the picked-up image (Step 52). Then, using the view fields T'ZH and T'ZV, ratios T'PH/T'ZH and T'PV/T'ZV of the view field of the photographic camera to that of the picked-up image in the horizontal and vertical directions are calculated (Step 53). Next, image frame data Dm corresponding to the view field ratios T'PH/T'ZH and T'PV/T'ZV is output (Step 54). The image frame data Dm is used, e.g., for an image frame signal to indicate horizontal and vertical positions. In this case, the image frame data Dm is generated based on the horizontal and vertical display lengths of a picked-up image of fixed size such that the horizontal and vertical lengths of the image frame are substantially equal to the corresponding lengths specified by the view field ratios T'PH/T'ZH and T'PV/T'ZV. The horizontal length of the image frame is adjusted in units of pixel pitch, and the vertical length of the same is adjusted in units of line pitch. The image frame data Dm output from the controller 27 is supplied to a frame signal generating circuit 32. The frame signal generating circuit 32 is also supplied with the synchronizing signals HD and VD from the synchronizing generator 16, and the clock pulses CK1 from the timing generator 14. The frame signal generating circuit 32 outputs, e.g., a white peak level signal at times corresponding to the horizontal and vertical positions specified by the image frame data Dm, and this signal is supplied to the adder 31 as a frame signal Sm to be added to the monochromatic video signal SV. Accordingly, a picked-up image as shown in FIG. 15 and the image frame of the photographic camera are displayed on the screen of the small-sized CRT of the electronic viewfinder 30. In this case, while the size of the picked-up image is fixed, the image frame of the photographic camera is displayed at a location corresponding to the zooming power. The size of the picked-up image is previously reduced to such an extent that the image frame of the photographic camera at the TELE end can be displayed, and the picked-up image is shown at the center of the screen of the small-sized CRT. A time base compressing process for such an image reduction is executed, e.g., by the encoder 28. In this embodiment, since the image frame of the photographic camera is displayed on the screen of the small-sized CRT of the electronic viewfinder 30 on the basis of the picked-up image of fixed size, the view field of the photographic camera can be accurately recognized even if the zooming power is changed. Accordingly, the user can correctly release the shutter of the photographic camera while viewing the display screen of the electronic viewfinder 30. Although, in this embodiment, the video camera and the photographic camera are integrally combined, this invention can be applied to a video camera to which a separate photographic camera is firmly fixed. In this case, input means for inputting, e.g., data representing the view fields T'PH and T'PV of the photographic camera (or data of the view angles PH and PV, or data representing the focal length f and the image plane size, PH and PV, of the film used) to the controller 27 may be provided, whereby the invention can be applied to any type of photographic cameras. A further embodiment of this invention will be described with reference to the drawings. FIG. 16 is a block diagram showing the arrangement of a video camera section according to this embodiment. In FIG. 16, the same reference numerals are used to denote corresponding parts in FIG. 2, and a detailed description thereof is omitted. As shown in FIG. 16, a monochromatic video signal SV output from an encoder 28 is supplied to an electronic viewfinder 30 through an adder 31, and a picked-up image is displayed at a small-sized CRT constituting the electronic viewfinder 30. A zoom driver 41 in FIG. 16 has an arrangement shown in FIG. 17. In the figure, reference numeral 411 represents a lens which constitutes an imaging lens 2 and is used to adjust the zooming power. The lens 411 can be moved back and forth when rotated, whereby the zooming power is adjusted. For example, when the lens 411 is rotated in a direction T, the zooming power changes in the TELE direction; when the lens is rotated in a direction W, the zooming power changes in the WIDE direction. The lens 411 is rotated by a DC motor 412, which is connected to output terminals q1 and q2 of a zoom driver unit 413. Input terminals p1 and p2 of the zoom driver unit 413 are connected, respectively, to fixed terminals T and W of a zoom switch 42 through terminals v of respective changeover switches 45 and 46. The switching of the changeover switches 45 and 46 is carried out by a zoom selection button (not shown in FIG. 1) arranged in the cabinet 1. For example, when the zoom selection button is not pressed, the switches 45 and 46 are connected to the respective terminals v, and when the button is pressed, the switches are connected to respective terminals p. When a high-level "H" signal is supplied to the terminal pl of the zoom driver unit 413, a current flows through the motor 412 from the terminal ql to the terminal q2 (as indicated by the solid line), and the lens 411 is rotated in the direction T. On the other hand, when a high-level "H" signal is supplied to the terminal p2, a current flows through the motor 412 from the terminal q2 to the terminal q1 (as indicated by the dashed arrow), and the lens 411 is rotated in the direction W. When neither the terminal p1 nor p2 is supplied with a high-level "H" signal, no current flows through the motor 412, and therefore, the lens 411 is not rotated in either direction and the position thereof is maintained. A movable terminal of the zoom switch 42 is connected to a power supply terminal. When the operating button 5T or 5W of the cabinet 1 is pressed, the zoom switch 42 is connected to the terminal T or W. When the operating button 5T or 5W is pressed with the zoom selection button released, a high-level "H" signal is supplied to the terminal p1 or p2 of the zoom driver unit 413, whereby the zooming power is adjusted in the TELE or WIDE direction. As shown in FIG. 16, a variable resistor 44 constituting a potentiometer is arranged at a location where the lens 411 of the imaging lens 2 is mounted. The variable resistor 44 is constructed such that the position of a movable terminal thereof is shifted as the lens 411 is rotated, whereby a voltage corresponding to the zooming power appears at the movable terminal and is applied to the controller 27 as a detection signal SDv. As shown in FIG. 18, the detection signal SDv is set such that it is 1 V at the WIDE end (f = 7 mm) and 4 V at the TELE end (f = 42 mm). In this embodiment, a 3-power zoom lens having a focal length f of 35 to 105 mm is used for the imaging lens 3 of the photographic camera section, and the zooming power of the imaging lens 3 is adjusted by a zoom driver 47. FIG. 19 shows the arrangement of the zoom driver 47 in detail. This zoom driver 47 has an arrangement similar to that of the aforementioned zoom driver 41, and therefore, the same reference numerals are used to represent corresponding parts and a detailed description thereof is omitted. Input terminals p1 and p2 of a zoom driver unit 413 of the zoom driver 47 are connected to fixed terminals T and W of a zoom switch 42 through terminals p of changeover switches 45 and 46, respectively. When the operating button 5T or 5W of the cabinet 1 is pressed, the zoom switch 42 is connected to the terminal T or W. When the operating button 5T or 5W is pressed with the zoom selection button held down, a high-level "H" signal is supplied to the terminal p1 or p2 of the zoom driver unit 413, whereby the zooming power is adjusted in the TELE or WIDE direction. As shown in FIG. 16, a variable resistor 48 constituting a potentiometer is arranged at a location where the lens 411 of the imaging lens 3 is mounted. The variable resistor 48 is constructed such that the position of a movable terminal thereof is shifted as the lens 411 is rotated, whereby a voltage corresponding to the zooming power appears at the movable terminal and is applied to the controller 27 as a detection signal SDp. As shown in FIG. 20, the detection signal SDp is set such that it is 1 V at the WIDE end (f = 35 mm) and 4 V at the TELE end (f = 105 mm). In this embodiment, a picked-up image is displayed at a fixed position on the screen of the small-sized CRT of the electronic viewfinder 30, and at the same time, an image frame of the photographic camera is displayed on the same screen. The angles of view of the video camera and the photographic camera change in accordance with the zooming power, and thus the view fields thereof change accordingly. To display an image frame of the photographic camera on the screen of the small-sized CRT, the ratio of the view fields of the picked-up image and the photographic camera must be obtained. The view angle  can be obtained from the image plane size T and the value f (focal length), using the above equation (1) and based on FIG. 9. The imaging lens 2 is a 6-power zoom lens having an f value of 7 to 42 mm. In the case wherein the imaging device 12 is a 1/3-inch·type, the image plane has a horizontal size ZH of 4.9 mm, a vertical size ZV of 3.69 mm, and a diagonal size ZD of 6.13 mm (see FIG. 10). Therefore, the view angles ZH and ZV in the horizontal and vertical directions at the WIDE end (f = 7 mm) are 38.6° and 29.5°, respectively. The view angles ZH and ZV in the horizontal and vertical directions at the TELE end (f = 42 mm) are 6.7° and 5.0°, respectively. The imaging lens 3 is a 3-power zoom lens having an f value of 35 to 105 mm. Where the film used is a 35 mm type, the image plane has a horizontal size PH of 36 mm, a vertical size PV of 24 mm, and a diagonal size PD of 43.3 mm (see FIG. 11). Therefore, the view angles PH and PV in the horizontal and vertical directions at the WIDE end (f = 35 mm) are 54.4° and 37.8°, respectively, and the view angles PH and PV in the horizontal and vertical directions at the TELE end (f = 105 mm) are 19,5° and 13.0°, respectively. From the above, the relationship between the view angles of the imaging lenses 2 and 3, which each comprise a zoom lens, can be summarized as shown in Table 5 below. Picked-up image WIDE - TELE Photographic camera WIDE - TELE Horizontal direction  ZH = 38.6 to 6.7°  PH = 54.4 to 19.5° Vertical direction  ZV = 29.5 to 5.0°  PV = 37.8 to 13.0° The ratio of the view fields of the photographic camera and the picked-up image will be now explained. From FIG. 9, the view field T' can be obtained by the aforementioned equation (2). Provided that the distances L from the object to both the imaging lenses 2 and 3 of the video camera section and the photographic camera section are the same, the view field ratio is found to vary as a function of view angle . From the horizontal and vertical view angles ZH and ZV of the picked-up image shown in Table 5, view fields T'ZH and T'ZV in the horizontal and vertical directions at the WIDE end are 0.7L and 0.53L, respectively, and view fields T'ZH and T'ZV in the horizontal and vertical directions at the TELE end are 0.12L and 0.09L, respectively. View angles ZH and ZV of the picked-up image at any point between the WIDE and TELE ends can be obtained from the detection signal SDv, using the following equations (6): ZH = 38.6° - (38.6° - 6.7°)(SDv - 1)/3 ZV = 29.5° - (29.5° - 5.0°)(SDv - 1)/3 By substituting the view angles ZH and ZV obtained by equations (6) individually for  in equation (2), the view fields T'ZH and T'ZV can be obtained. From the horizontal and vertical view angles PH and PV of the photographic camera shown in Table 5, view fields T'PH and T'PV in the horizontal and vertical directions at the WIDE end are 1.03L and 0.69L, respectively, and view fields T'PH and T'PV in the horizontal and vertical directions at the TELE end are 0.34L and 0.23L, respectively. View angles PH and PV of the photographic camera at any point between the WIDE and TELE ends can be obtained from the detection signal SDp, using the following equations (7): PH = 54.4° - (54.4° - 19.5°)(SDp - 1)/3 PV = 37.8° - (37.8° - 13.0°)(SDp - 1)/3 By substituting the view angles PH and PV obtained by equations (7) individually for 9 in equation (2), the view fields T'PH and T'PV can be obtained. From the foregoing, the relationship between the view field of the picked-up image and that of the photographic camera can be summarized as shown in Table 6 below. FIG. 21 shows the relationship of the view fields in the horizontal direction, and FIG. 22 shows the relationship of the view fields in the vertical direction. Picked-up image WIDE - TELE Photographic camera WIDE - TELE Horizontal direction T'ZH = 0.7L to 0.12L T'PH = 1.03L to 0.34L Vertical direction T'ZV = 0.53L to 0.09L T'PV = 0.69L to 0.23L Further, view field ratios T'PH/T'ZH and T'PV/T'ZV in the horizontal and vertical directions become as shown in Table 7. View field ratio T'PH/T'ZH in horizontal direction 0.49 to 8.58 View field ratio T'PV/T'ZV in vertical direction 0.43 to 7.67 From FIG. 9, the view field T' can also be obtained as shown in the aforementioned equation (4). The focal length f of the imaging lens 2 can be obtained from the detection signal SDv, using the following equation (8): f = 7 mm + (42 mm - 7 mm)(SDv - 1)/3 The focal length f, obtained by equation (8), is substituted into equation (4) and the horizontal and vertical sizes ZH and ZV of the image plane are substituted individually for T in equation (4), whereby the horizontal and vertical view fields T'ZH and T'ZV are obtained. The focal length f of the imaging lens 3 can be obtained from the detection signal SDp, using the following equation (9): f = 35 mm + (105 mm - 35 mm)(SDp - 1)/3 By substituting the focal length f obtained by equation (9) into equation (4) and substituting the horizontal and vertical sizes PH and PV of the image plane individually for T in equation (4), the horizontal and vertical view fields T'PH and T'PV can be obtained. Referring again to FIG. 16, the controller 27 generates image frame data Dm for displaying the image frame of the photographic camera at a location on the display screen corresponding to the horizontal and vertical view field ratios T'PH/T'ZH and T'PV/T'ZV. FIG. 23 is a flowchart showing an image frame data output process executed by the controller 27. First, the focal length f of the imaging lens 2 is computed from the detection signal SDv, using equation (8) (Step 71). Subsequently, the obtained focal length f is substituted into equation (4), and the horizontal and vertical sizes ZH and ZV of the image plane are substituted individually for T in equation (4), to thereby obtain horizontal and vertical view fields T'ZH and T'ZV of the video camera (Step 72). The focal length f of the imaging lens 3 is then calculated from the detection signal SDp, using equation (9) (Step 73). Next, the thus-obtained focal length f is substituted into equation (4), and the horizontal and vertical sizes PH and PV of the image plane are substituted individually for T in equation (4), to thereby obtain horizontal and vertical view fields T'PH and T'PV of the photographic camera (Step 74). Then, using the view fields T'ZH, T'ZV, T'PH and T'PV, ratios T'PH/T'ZH and T'PV/T'ZV of the view field of the photographic camera to that of the picked-up image in the horizontal and vertical directions are calculated (Step 75). Next, image frame data Dm corresponding to the view field ratios T'PH/T'ZH and T'PV/T'ZV is output (Step 76). The image frame data Dm is used. e.g., for an image frame signal to indicate horizontal and vertical positions. In this case, the image frame data Dm is generated based on the horizontal and vertical display lengths of a picked-up image of fixed size such that the horizontal and vertical lengths of the image frame are substantially equal to the corresponding lengths determined by the view field ratios T'PH/T'ZH and T'PV/T'ZV. The horizontal length of the image frame is adjusted in units of pixel pitch, and the vertical length of same is adjusted in units of line pitch. Referring again to FIG. 16, the image frame data Dm output from the controller 27 is supplied to a frame signal generating circuit 32. The frame signal generating circuit 32 is also supplied with synchronizing signals HD and VD from the synchronizing generator 16, and clock pulses CK1 from the timing generator 14. The frame signal generating circuit 32 outputs, e.g., a white peak level signal at times corresponding to the horizontal and vertical positions specified by the image frame data Dm, and this signal is supplied to an adder 31 as a frame signal Sm to be added to a monochromatic video signal SV. Accordingly, a picked-up image as shown in FIG. 24 and the image frame of the photographic camera are displayed on the screen of the small-sized CRT of the electronic viewfinder 30. In this case, while the size of the picked-up image is fixed, the image frame of the photographic camera is displayed at a location corresponding to the zooming power. The size of the picked-up image is previously reduced to such an extent that the image frame of the photographic camera at the WIDE end can be displayed when the picked-up image is generated by the video camera at the TELE end. The picked-up image is shown at the center of the screen of the small-sized CRT. A time base compressing process for such an image reduction is executed, e.g., by an encoder 28. In this embodiment, since the image frame of the photographic camera is displayed on the screen of the small-sized CRT of the electronic viewfinder 30 on the basis of the picked-up image of fixed size, the view field of the photographic camera can be accurately recognized even if the zooming power of the video camera or that of the photographic camera is changed. Accordingly, the user can correctly release the shutter of the photographic camera while viewing the display screen of the electronic viewfinder 30. Although, in this embodiment, the video camera and the photographic camera are integrally combined, this invention can be applied to a video camera to which a separate photographic camera is firmly fixed. In this case, input means for inputting, e.g., data representing the view fields T'PH and T'PV of the photographic camera (or data of the view angles PH and PV, or data representing the focal length f and the image plane size, PH and PV, of the film used) to the controller 27 may be provided, whereby the invention can be applied to any type of photographic cameras. Further, in the above embodiment, the zoom buttons 5T and 5W (zoom switch 42) are used for changing the zooming power of both the imaging lenses 2 and 3, but separate operating buttons may be provided for the purpose. It will be obvious to those having ordinary skill in the art that many changes may be made in the above-described details of the preferred embodiments of the present invention without departing from the scope of the present invention.

Claims: A video camera for use with a photographic camera, said video camera comprising: an electronic viewfinder (30) for providing image information of said video camera and of a photographic camera; video pickup means (2, 11) for picking-up a video image; video signal generating means (12) for generating an image video signal representative of said picked-up video image; image frame signal generating means (32) for generating an image frame signal representative of an image frame of the field of view of the photographic camera; image frame position changing means (27) for affecting the image frame signal generating means to generate said image frame signal so as to change said image frame representing the field of view of the photographic camera; and signal composition means (31) for providing a composite signal for driving the electronic viewfinder (30) by combining the image video signal with the image frame signal; wherein the picked-up video image is displayed with a fixed size on the screen of the electronic viewfinder (30), and the image frame of the photographic camera is displayed on the screen relative to the picked-up video image in accordance with the view field ratio of the photographic camera with respect to the video camera, characterized in that the video camera has a zoom function affecting the field of view of said video camera in accordance with an adjustable zoom power, whereby said video pickup means picking up the video image within the field of view determined by said zoom power; and whereby said image frame of the photographic camera being changed in accordance with the field of view of the video camera that is calculated based on information about said zoom power of the video camera, and in that said fixed size of the picked-up video image is reduced to such an extent that it covers only a portion of the view finder screen so that the image frame of the photographic camera can always be displayed on said screen, even when the picked-up image is generated by said video camera at the TELE end.

Inventors: HARUO SAITO, HIROYUKI HASHIMOTO, HARUO, SAITO, HIROYUKI, HASHIMOTO
Applicants: AIWA CO, AIWA CO., LTD.
Application year: 1992
Main classification: G03B17
IPC codes: H04N5, G03B17