JP3048437B2 - Video camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera suitable for taking a still image.

[0002]

2. Description of the Related Art By using a video camera, it is possible to capture a still image in addition to a moving image. In this case, when the light amount of the subject is insufficient, it is conceivable to use a strobe so that the amount of charge accumulated in the image sensor becomes sufficient.

[0003]

By the way, when an image pickup device having an electronic shutter function is used and the amount of light emitted from the strobe is constant, the charge accumulation time in the image pickup device becomes shorter as the shutter speed increases. The amount of accumulated charges is reduced, and the level of the imaging signal is reduced.

Therefore, in the present invention, the level of an image pickup signal by strobe light emission is kept constant even when the shutter speed changes, for example.

[0005]

The present invention comprises a shutter, strobe light emitting means, an AGC circuit for controlling the level of an image signal output from an image pickup device, and control means for controlling light emission of the strobe light emitting means. The control means controls the light emission peak according to the shutter speed of the shutter so that the light emission peak is within the charge accumulation period of the image sensor and the image pickup signal is at a constant level. In addition, the light emission amount is controlled based on the control signal of the AGC circuit.

[0006]

The higher the shutter speed of the electronic shutter, the smaller the amount of charge stored in the image sensor, and the lower the level of the image signal output from the image sensor. The control signal of the AGC circuit corresponds to the level of the imaging signal (the illuminance of the subject taking into account the shutter speed). Therefore, by controlling the light emission amount of the strobe light emitting means based on the control signal of the AGC circuit, it becomes possible to keep the level of the imaging signal output from the AGC circuit constant even if the shutter speed changes, for example.

[0007]

An embodiment of the present invention will be described below with reference to the drawings. In this example, a video camera and a photo camera are integrally formed.

FIG. 1 is a perspective view showing the overall configuration. In FIG. 1, reference numeral 1 denotes a cabinet. Although not shown, the cabinet 1 contains a video camera unit including an image sensor, a signal processing circuit, and the like, and a photo camera unit including a film loading mechanism, a film driving mechanism, and the like.

Reference numeral 2 denotes an imaging lens of a video camera unit,
Reference numeral 3 denotes an imaging lens of the photo camera unit. That is, the optical systems of the video camera unit and the photo camera unit are configured separately. The focal length f of the imaging lens 2 is 7 mm to 42 m
A 6 × m zoom lens is used. On the other hand, as the imaging lens 3, a fixed focal length lens having a focal length f of 55 mm is used.

In the present embodiment, an electronic view finder made of a small CRT is provided in the cabinet 1.
A screen captured by the video camera unit via the imaging lens 2 is displayed on the RT. 4 is an eyecup. In addition,
There is no finder for directly checking the screen imaged by the photo camera unit via the imaging lens 3.

Reference numerals 5T and 5W denote zoom operation buttons for performing zoom operations in the TELE direction and the WIDE direction, respectively. Reference numeral 6 denotes a recording button for performing an operation of recording an imaged video signal output from the video camera unit on a VTR. Reference numeral 7 denotes a shutter button, 8 denotes a film rewind operation button, and 9 denotes a flash.

FIG. 2 shows the configuration of the video camera unit. Image light from a subject is supplied via an imaging lens 2 and an iris 11 to a single-chip CCD solid-state imaging device 12 having complementary color checkerboard color filters.

The zoom magnification of the imaging lens 2 is adjusted by a zoom driver 41. FIG. 7 shows a specific configuration of the zoom driver 41. In the figure,
Reference numeral 411 denotes a lens constituting the imaging lens 2 for adjusting a zoom magnification. By moving the position of this lens 411 back and forth by rotational driving,
The zoom magnification is adjusted. For example, by rotating to the T side, it is adjusted in the TELE direction, and by rotating to the W side, it is adjusted in the WIDE direction.

The rotation of the lens 411 is performed by a DC motor 412. One end and the other end of the motor 412 are connected to output terminals q1 and q2 of the zoom driver 413, respectively. The input terminals p1 and p2 of the zoom driver unit 413 are respectively connected to the zoom operation switch 4
2 are connected to the fixed terminals on the T and W sides.

In this case, when a high-level "H" signal is supplied to the terminal p1, a current flows through the motor 412 in the direction from the terminal q1 to the terminal q2 (shown by a solid line), and the lens 411 rotates in the T direction. Driven. Conversely, when a high-level "H" signal is supplied to the terminal p2, the terminal q2
, A current flows to the motor 412 in the direction of the terminal q1 (shown by a broken line), and the lens 411 is driven to rotate in the W direction. When a high-level "H" signal is not supplied to either of the terminals p1 and p2, no current flows through the motor 412, the lens 411 is not driven to rotate in any direction, and the position is maintained. Is done.

The movable terminal of the zoom operation switch 42 is connected to a power supply terminal. Operation button 5 of cabinet 1 described above
When pressing T and 5W, the zoom operation switch 42 is connected to the T side and the W side, respectively. Zoom operation switch 4
When 2 is connected to the T side and the W side, a high-level "H" signal is supplied to terminals p1 and p2 of the zoom driver unit 413, respectively, and zoom adjustment is performed in the TELE direction and the WIDE direction.

FIG. 3 is a schematic diagram of the color coding of the image pickup device 12. As shown in the figure, field reading is performed. In the A field, charges are mixed in pairs such as A1 and A2, and in the B field, charges are mixed in pairs such as B1 and B2. From the horizontal shift register Hreg, A1, A2,.
.. Are output in the B field in the order of B1, B2,.

Here, as shown in FIG. 4, the order of the charges a, b,... Is (Cy +
G), (Ye + Mg),..., (Cy + Mg), (Ye + G),... In the A2 line, and (G + Cy), (Mg + Y) in the B1 line.
e),..., and (Mg +
Cy), (G + Ye),.

Returning to FIG. 2, the electric charge output from the image pickup device 12 as described above is supplied to a CDS circuit (correlated double sampling circuit) 13, and is taken out from the CDS circuit 13 as an image pickup signal. By using the CDS circuit 13, reset noise can be reduced as is well known.

Timing pulses required by the image pickup device 12 and the CDS circuit 13 are supplied from a timing generator 14. The timing generator 14 has 8
fsc (fsc is the color subcarrier frequency) reference clock CK0
, And horizontal and vertical synchronization signals HD and VD are supplied from the synchronization generator 16. On the other hand, synchronization generator 1
6 is a clock CK of 4 fsc from the timing generator 14.
1 is supplied.

Although not described above, the image sensor 12 has an electronic shutter function. The shutter speed is set by a shutter speed setting switch 32 connected to the timing generator 14. In the controller 27,
Shutter speed information is supplied from the timing generator 14. The shutter speed setting switch 32 may be provided on the controller 27 side.

The image signal output from the CDS circuit 13 is supplied to a level detection circuit 17a. This detection circuit 17
The output signal a is supplied as a control signal to the iris 11 via the iris driver 17b, and the aperture of the iris 11 is automatically controlled.

Here, a process for obtaining a luminance signal Y and a chroma signal (color difference signal) from the imaging signal output from the CDS circuit 13 will be described.

The luminance signal Y is obtained by adding adjacent signals. In FIG. 4, a + b, b +
An added signal of c, c + d, d + e,... is sequentially formed.

For example, the A1 line is approximated by the following equation. Here, Cy = B + G, Ye = R + G, Mg
= B + R.

Y = {(Cy + G) + (Ye + Mg)) × 1/2 = (2B + 3G + 2R) × 1/2 Further, the A2 line is approximated by the following equation.

Y = {(Cy + Mg) + (Ye + G)) × 1/2 = (2B + 3G + 2R) × 1/2 Other lines in the A field and lines in the B field are similarly approximated.

The chroma signal is obtained by subtracting adjacent signals.

For example, the A1 line is approximated by the following equation.

R−Y = (Ye + Mg) − (Cy + G) = (2R−G) Further, the A2 line is approximated by the following equation.

− (B−Y) = (Ye + G) − (Cy−Mg) = − (2B−G) Similarly, the other lines in the A field and the lines in the B field are also provided with the red difference signals RY and RY. The blue difference signal-(BY) is obtained alternately in a line-sequential manner.

Returning to FIG. 2, the imaging signal output from the CDS circuit 13 is supplied to the AGC amplifier 19a. The output signal of the AGC amplifier 19a is supplied to a level detection circuit 19b.
The output signal of the detection circuit 19b is supplied as a control signal Sgc to the AGC amplifier 19a via the buffer 19c, and is also supplied to the controller 27.

The image signal output from the AGC amplifier 19a is supplied to a low-pass filter 20 constituting a luminance processing unit. The low-pass filter 20 performs an addition process (averaging) of adjacent signals. Therefore, a luminance signal Y is output from the low-pass filter 20.

The image pickup signal output from the AGC amplifier 19a is supplied to sample and hold circuits 21 and 22 constituting a chroma processing unit. Sample hold circuit 2
Sampling pulses SHP1 and SHP2 (illustrated by E and F in FIGS. 5 and 6) are supplied from the timing generator 14 to 1 and 22. FIG. 5A shows the signal of the A1 line,
FIG. 6A shows a signal on the A2 line.

From the sample hold circuit 21, (Cy
+ G) or (Cy + Mg) continuous signal S1 is output and supplied to the subtractor 23 (shown in FIGS. 5B and 6B). From the sample and hold circuit 22, (Ye + M
g) or a continuous signal S2 of (Ye + G) is output and supplied to the subtractor 23 (shown in FIGS. 5C and 6C).

In the subtractor 23, the signal S1 is subtracted from the signal S2. Therefore, the subtractor 23 outputs the red difference signal RY and the blue difference signal-(BY), respectively, in a line-sequential manner (illustrated in FIGS. 5D and 6D).

The color difference signal output from the subtractor 23 is supplied to the fixed terminal b of the direct changeover switch 24 and the fixed terminal a of the changeover switch 25 and has a delay time of one horizontal period. The signal is supplied to the fixed terminal on the a side of the changeover switch 24 and the fixed terminal on the b side of the changeover switch 25 via 26.

The switching of the changeover switches 24 and 25 is controlled by the controller 27. That is, one horizontal period during which the red difference signal RY is output from the subtractor 23 is b.
, While one horizontal period during which the blue difference signal-(BY) is output is connected to the a side. The controller 27 is supplied with the synchronization signals HD and VD from the synchronization generator 16 as reference synchronization signals, and is also supplied with a clock CK1 from the timing generator 14.

Since the changeover switches 24 and 25 are switched as described above, the changeover switch 24 outputs the red color difference signal RY in each horizontal period, and the changeover switch 25 outputs the blue color difference signal-() in each horizontal period. BY) is output.

The luminance signal Y output from the low-pass filter 20 and the color difference signals (RY) and-(BY) output from the changeover switches 24 and 25 are supplied to an encoder 28. The encoder 28 is supplied with a composite synchronization signal SYNC, a blanking signal BLK, a burst flag signal BF, and a color subcarrier signal SC from the synchronization generator 16.

As is well known, the encoder 28 adds the synchronizing signal SYNC for the luminance signal Y and quadrature two-phase modulation for the color difference signal to form the carrier chrominance signal C and adds the color burst signal. . And
The luminance signal Y and the carrier chrominance signal C are added to form, for example, an NTSC color video signal SCV. Color video signal S output from encoder 28
The CV is led out to the output terminal 29.

A black-and-white video signal SV (a luminance signal Y to which a synchronization signal SYNC is added) is output from the encoder 28. The black-and-white video signal SV is supplied to an electronic viewfinder 30, and an image pickup screen is displayed on a small CRT. Is done.

A strobe mode setting switch 33 is connected to the controller 27. Turning on the setting switch 33 switches the mode from the normal mode to the strobe mode. In the strobe mode, when the shutter button 7 (shown in FIG. 1) is pressed and the shutter switch 34 connected to the controller 27 is turned on, the flash emission signal S is transmitted from the controller 27 to the strobe 9 in the next vertical period.
tr is supplied and controlled to emit light.

In the strobe mode, the level detection circuit 19
b to control signal Sgc supplied to AGC amplifier 19a
, The amount of light emitted from the strobe 9 is controlled, and the level of the imaging signal output from the AGC amplifier 19a is controlled to be constant. The control signal Sgc corresponds to the level of the image signal output from the image sensor 12, and thus corresponds to the illuminance of the object when the iris is open.

Here, even if the illuminance of the object is the same, as the shutter speed increases, the charge accumulation time decreases, the amount of accumulated charge decreases, and the level of the imaging signal from the imaging element 12 decreases. FIG. 8 shows the relationship between the shutter speed (charge storage time) and the amount of stored charge. In the figure, the accumulated charge amount when the charge accumulation time is 1/60 second is shown as 100%. That is, the higher the shutter speed, the lower the illuminance of the subject is.

The solid line a in FIG. 9 shows the relationship between the illuminance of the subject and the output of the AGC amplifier 19a. The hatched portions are due to the emission of the strobe light 9. The dashed line b in the figure shows the relationship when the iris 11 is open and the gain of the AGC amplifier 19a is fixed to the gain when the iris is open.

By the way, the electronic shutter function of the image pickup device 12 operates so that the charge accumulation time in each vertical period becomes equal to the shutter speed.
This is performed by supplying a charge sweeping pulse to the image sensor 12. Therefore, the higher the shutter speed, the longer the charge sweep pulse supply period (charge sweep period).

In this embodiment, the controller 27 controls the timing of the light emission trigger signal Str supplied to the strobe 9 as the shutter speed increases, so that the light emission peak of the strobe 9 coincides with the charge accumulation period. Is controlled.

In the above configuration, when the setting switch 33 is turned on, the mode changes from the normal mode to the strobe mode in synchronization with the next vertical synchronizing signal VD (shown in FIG. 10D). FIG. 10A shows the vertical synchronization signal VD.

Each vertical period is constituted by a charge sweeping period To in which a charge sweeping pulse is supplied to the image pickup device 12 and a charge accumulation period Tc in which charges are accumulated without supplying a charge sweeping pulse to the image pickup device 12. Thus, the accumulated charges are as shown in FIG. 10E. The supply period To of the charge sweeping pulse is controlled so that the charge accumulation period Tc matches the shutter speed. FIG. 10B shows an example of setting the shutter speed.
It has been changed to 50 seconds.

At the end of each vertical period, a read pulse is supplied to the image sensor 12 (shown in FIG. 10C). Therefore, the charge stored in the image sensor 12 is as shown in FIG. 10E. On the other hand, the image pickup signal output from the image pickup device 12, that is, from the AGC amplifier 19a is as shown in FIG.

When the shutter switch 34 is turned on (shown in FIG. 10G), a flash trigger signal Str is supplied from the controller 27 to the strobe 9 in the next vertical period in synchronization with the vertical synchronization signal VD (see FIG. 10H). Illustrated). The light emission trigger signal Str is generated after a time τa from the vertical synchronization signal VD, and the time τa is changed according to the shutter speed. Thereby, the emission peak of the strobe 9 is made to coincide with the charge accumulation period Tc (FIG. 10E,
I). In FIG. 10I, τb is a light emission trigger signal S
This is the time from the timing of tr until the flash 9 actually emits light, and the time τb is a fixed amount.

Here, when the shutter speed changes, the charge accumulation time changes, and the illuminance of the subject substantially changes. Therefore, when the subject illuminance is in the flash emission range (see FIG. 9), the level of the imaging signal output from the AGC amplifier 19a decreases as the shutter speed increases (shown in FIG. 10J).

However, since the light emission amount Va of the strobe 9 is controlled based on the control signal Sgc of the AGC amplifier 19a corresponding to the illuminance of the subject, even if the shutter speed changes, an image signal by the light emission of the strobe 9 (see FIG. 10J). The level indicated by hatching is always constant.

FIG. 10K shows a capture pulse PTI output from the controller 27. By using the capture pulse PTI, for example, a still image recorder connected to the output terminal 29 emits an image from the strobe 9 by emitting light.
The imaging signals (n + 1) and (m + 1) for the screen can be captured.

As described above, in this embodiment, since the light emission amount of the strobe 9 is controlled based on the control signal Sgc of the AGC amplifier 19a, even if the shutter speed changes and the illuminance of the subject changes substantially, the AGC is performed. The level of the imaging signal output from the amplifier 19a can be constant.

Further, the timing of the light emission trigger signal Str is changed in accordance with the shutter speed so that the light emission peak of the strobe light 9 coincides with the charge accumulation period Tc of the image sensor 13, so that the light emission of the strobe light 9 is performed. Can be used effectively.

In the above-described embodiment, the change in the illuminance of the subject due to the change in the shutter speed is focused on. Even if the subject illuminance changes in the light emission range, the level of the imaging signal output from the AGC amplifier 19a can be kept constant.

[0059]

According to the present invention, the light emission amount of the strobe light emitting means is controlled based on the control signal of the AGC circuit, so that a constant level image signal can be obtained from the AGC circuit even if the shutter speed changes. Can be.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an appearance of an embodiment.

FIG. 2 is a diagram illustrating a configuration of a video camera unit.

FIG. 3 is a schematic diagram of color coding of an image sensor.

FIG. 4 is a diagram illustrating an output of a horizontal output register of the image sensor.

FIG. 5 is a diagram for explaining color signal processing.

FIG. 6 is a diagram for explaining color signal processing.

FIG. 7 is a diagram illustrating a configuration of a zoom driver.

FIG. 8 is a diagram illustrating a relationship between a shutter speed and an accumulated charge amount.

FIG. 9 is a diagram showing the illuminance of a subject and the output of an AGC amplifier.

FIG. 10 is a diagram showing an operation in a strobe mode.

[Explanation of symbols]

 Reference Signs List 1 cabinet 2, 3 imaging lens 4 eyecup 5T, 5W zoom operation button 6 recording button 7 shutter button 9 strobe 12 CCD solid-state imaging device 14 timing generator 16 synchronization generator 19a AGC amplifier 20 low-pass filter 21, 22 sample hold circuit 23 Subtractor 24, 25 changeover switch 26 Delay circuit 27 Controller 28 Encoder 29 Output terminal 30 Electronic viewfinder 32 Shutter speed setting switch 33 Strobe mode setting switch 34 Shutter switch

Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03B 15/04-15/05 G03B ^7/ 00-7/28 H04N 5/222-5/257 H04N 5/30-5 / 335

Claims (1)

(57) [Claims] A shutter for controlling a level of an image signal output from an image sensor;
A control circuit for controlling light emission of the strobe light emitting means, wherein the control means controls the light emission peak to be within a charge accumulation period of the image pickup device, and sets the image pickup signal to a constant level. A video camera, wherein the light emission timing of the strobe light emitting means is varied according to a shutter speed of a shutter, and the light emission amount is controlled based on a control signal of the AGC circuit.