JP2960075B2 - Camera using image sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a camera using an imaging device.

[Prior Art] Many non-lens interchangeable so-called compact cameras are equipped with a half-open shutter that also functions as an aperture as a shutter. Many of the known compact cameras are configured as built-in strobe cameras with built-in strobes. The built-in strobe built-in flash cameras include an aperture value (shutter aperture value) at the time of flash photography as a component of a guide number. In many cases, an aperture control device or a light control device called a flashmatic which is automatically set in accordance with the subject distance is mounted.

In flash photography by a compact camera equipped with this flashmatic, in the process of opening the half-open shutter, the flash is fired when the shutter opening reaches a predetermined F value, and the shutter is closed after the emission is completed. The operation is performed. This flash control method is effective only when the flash emission time is very small compared to the aperture speed of the aperture, and is appropriate when the flash emission time is not small compared to the aperture speed of the aperture. Can not be obtained.

That is, in the case of the compact camera described above, the shutter blades travel at 10 to 20 msec from the fully closed state to the fully opened state, but the strobe emission time is several tens of μsec. Therefore, the flash emission time is extremely short, and the fluctuation of the aperture value (shutter aperture value) at the time of flash emission is a value enough to fall within the latitude of the silver halide film. Therefore, when the shutter is opened and the shutter aperture value reaches a predetermined F-number, a predetermined exposure can be performed on the film surface even when the strobe is fired and the photographing is performed, and the exposure may be insufficient. There was no.

On the other hand, recently used electronic still cameras use a semiconductor such as a CCD (charge-coupled device) having a smaller latitude than a silver halide film as an optical image input device. Therefore, it is impossible to employ a digital camera, and therefore, in an electronic camera, an external dimming type dimming control device used in a single lens reflex camera is mounted. As is well known, the external dimming method projects strobe light onto a subject, integrates the amount of reflected light from the subject, and when the integrated value reaches a predetermined value (integrated dimming constant). This is a dimming method that stops the flash emission. In this method, the flash emission time varies depending on the reflectivity of the subject and the subject distance, so the maximum flash time may be several milliseconds. When light is emitted, the ratio of the light emission time to the aperture opening speed becomes significantly larger than the value in the flashmatic system, so that the change in the aperture value becomes a considerable size, and as a result, stable exposure cannot be obtained. Therefore, in the case of the external dimming type, it is desirable to perform a constant aperture strobe light emission method in which the aperture value at the time of flash emission is fixed so that the aperture value does not fluctuate during the flash emission.

[Problems to be Solved by the Invention] As a simplest method for setting the aperture to a constant aperture at the time of strobe light emission, for example, a full aperture strobe light emission method of opening the aperture at the time of strobe light emission can be considered.

FIG. 5 shows the time relationship between the aperture value and the flash emission when the aperture is opened during flash emission as described above. In Figure 5, horizontal axis represents time and the vertical axis represents the aperture fully open necessary time to open aperture from the fully closed state T _c is squeezed, T _st is the flash light emission time, T _o is the throttle fully opened This is the time required for closing until it is completely closed. In the case where the running characteristics of the shutter blade are represented by a in FIG. 5, the hatched portion indicates an extra exposure amount more than necessary for flash photography. However, according to this full-open strobe light emission method, there is a problem in that the image is overexposed by the amount represented by the hatched portion during daytime shooting requiring backlight correction, and the above-described hatched portion is also used in nighttime flash shooting. If the portion is large, a problem arises that the dark current of the CCD increases and the image quality deteriorates.

Therefore, in order to solve the above problem, (i) the speed of the shutter blade (aperture blade) is increased to reduce the exposure by light other than the light required for photographing, and (ii) some control means is used when strobe light is emitted. Therefore, it is necessary to take measures such as holding the shutter or the aperture at an aperture value other than the open aperture value.

The case where the running characteristic of the shutter blade is represented by the line b in FIG. 5 indicates the relationship between the aperture and the flash emission when the measure (i) is taken.

FIG. 6 shows the relationship between the aperture and the strobe light emission when the measure (ii) is implemented.

By the way, in order to implement the measure (i) (that is, to increase the speed of the shutter blades), it is necessary to increase the power of the motor or the like or increase the current supplied to the motor. However, an increase in the motor capacity and an increase in the motor energizing current are not preferable because they not only increase the size and cost of the camera and the like but also increase the battery consumption speed and the running cost.

On the other hand, in order to realize the above measure (ii), for example, (a) a constant aperture method using mechanical means of inserting a round aperture having an appropriate aperture diameter into the optical path at the time of flash photography, b) decelerating a motor which is a drive source of a shutter blade (aperture blade) when the blade approaches a predetermined stop position;
A constant throttle method by electrical control of stopping at the predetermined position after that may be considered, but each of these methods has the following disadvantages.

That is, the method (a) inevitably increases the complexity and size of the shutter mechanism, and naturally requires a considerable increase in cost.

On the other hand, in order to realize the above method (b), advanced drive control is required, which results in a large increase in the cost of both hardware and software of the electronic device, and the precision of the shutter blades for the following reasons. Positioning is difficult. That is, as shown in FIG. 7, in order to accurately stop at a position corresponding to the shutter blades to the aperture diameter F _x of a given aperture value, the speed of the shutter blade as the target aperture value is small aperture side Must be smaller,
If the speed of the shutter blade is set to a slightly lower speed that allows the shutter blade to stop accurately without overshooting at the target aperture value, conversely, if it is necessary to stop and control the shutter blade near the fully open position, This is because the dark current of the CCD is increased and the image quality is deteriorated, and the overexposure is caused by excessive strobe light.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a camera using an image pickup device capable of performing appropriate photographing using an external light control type flash device.

[Means for Solving the Problems] In a camera using an image pickup device according to the present invention, an aperture / shutter, an image pickup device for receiving a light beam incident through an opening of the shutter, and an image signal from the image pickup device In addition to a control circuit for processing and recording, the sensor receives reflected light from the object due to flash light emission, monitors the amount of flash light emission with the received light amount, and the amount of flash light emission corresponds to the shutter opening value. In a camera using an image sensor that performs flash photography with an external dimming strobe device that stops flash emission when a predetermined value corresponding to a set flash dimming constant is reached, the camera adjusts according to the distance of an object. Information setting means for setting shutter opening value information in accordance with data from the data forming means for forming data; and shutter opening by driving the shutter and setting the shutter opening by the information setting means. A drive circuit that shifts to the aperture value of the aperture value information based on the obtained aperture value information, a detection unit that detects information corresponding to an actual aperture value at the end of shutter driving by the drive circuit, And a strobe dimming constant setting means for setting a strobe dimming constant of the external dimming type strobe device in accordance with the detected information.

Example An example of the present invention will be described below with reference to the drawings.

FIG. 4 shows a shutter portion of an electronic camera using a CCD as an image sensor as an embodiment of a camera using the image sensor according to the present invention.

In FIG. 4, reference numerals 1 and 2 denote shutter blades which can be moved in the direction of the arrow in the figure, reference numeral 3 denotes a gear rotated by a motor (not shown), and reference numeral 4 denotes a rotation about an axis perpendicular to the plane of FIG. Shutter plate.
The shutter plate 4 has teeth 4c that mesh with a rack member (not shown).
The rack member is engaged with the gear 3 and is driven by the gear 3. A pair of pins 4a and 4b are projected from the shutter plate 4 symmetrically with respect to the axis, and the pins 4a are slidably inserted into grooves 1b formed through the protrusions 1a of the shutter blade 1, The pin 4b is slidably inserted into a groove 2b penetrating the projection 2a of the shutter blade 2.

Reference numeral 5 denotes a stepped gear driven gear that meshes with teeth 4c of the shutter plate 4 and is driven to rotate by the shutter plate 4, reference numeral 6 denotes a pulse sheet (that is, an encoder) fixed to an end surface of the driven gear 5, and reference numeral 7 denotes a pulse sheet. Photointerrupters 8a and 8b for generating an electrical pulse signal corresponding to the light transmitting portion
Reference numeral 1c denotes a fixed guide pin which is inserted into the linear grooves 1d and 2d of the shutter blades 1 and 2 to guide and support the shutter blades 1 and 2 so that they can move in the left-right direction in FIG.
Reference numerals 2c and 2c denote aperture holes for shutter openings penetrating through the shutter plates 1 and 2, respectively. FIG. 4A shows the shutter fully closed state, and FIG. 4B shows the shutter small aperture state.

The operation of the half-open shutter shown in FIG. 4 will be described below.

When the motor (not shown) rotates, the rack member (not shown) is driven straight forward by the gear 3, and the shutter plate 4 meshing with the rack member is rotated clockwise in FIG. 4 (a). Then, the pin 4a of the shutter plate 4
4A moves to the right in FIG. 4A and the pin 4b moves to the left, so that the shutter blade 1 is moved to the left and the shutter blade 2 is moved to the right. Therefore, the shutter
The state changes from the fully closed state in FIG. 4A to the small aperture state in FIG. 4B. On the other hand, since the shutter plate 4 is rotated, the driven gear 5 meshing with the teeth 4c of the shutter plate 4 is rotated, and the pulse sheet 6 fixed to the gear 5 is used as a light emitting element and a light receiving element of the photo interrupter 7. Therefore, an electric pulse signal is generated in the light receiving element every time the light passes through the light transmitting portion of the pulse sheet 6, and the pulse signal is counted by a pulse counter to be described later. The speed and the instantaneous position are electrically detected.

Then, the shutter blades 1 and 2 are driven by the motor.
Is driven in the opening direction, and when the shutter opening diameter reaches a predetermined value, the motor is stopped. After that, after the strobe light emission is performed, the motor is reversed and the shutter blades 1 and 2 are rotated. Is returned to the fully closed state in FIG. 4A by the motor or a spring (not shown).

The motor is controlled by a driving unit in a flash photography control device described later.

Next, the configuration of the electronic camera of this embodiment is shown in FIGS. 1 and 2, and its operation is shown in the flowchart of FIG.

In FIG. 2, a dotted line represents a light beam, two solid lines represent a mechanical transmission system, and one solid line represents transmission of an electric signal.

In FIG. 2, a light beam having passed through a photographing lens 11 is subjected to exposure control by a shutter 12 also serving as an aperture, then enters a CCD 13, and is photoelectrically converted by the CCD 13. The output of the CCD 13 is processed in a signal processing circuit 14 according to a predetermined format, and then recorded on a recording medium such as a magnetic disk in a disk drive 15.

To adjust the focus of the taking lens 11, when the release switch SW1 of the camera is turned on (# 1), the distance measurement information output from the AF sensor 20 is taken into a control circuit 23 composed of a microcomputer or the like, and the lens movement amount (measurement). The distance value D) is calculated, and the focusing lens is driven by the driving means 16 (# 2).

In the control circuit 23, main parts of a flash (flash emission) photographing control device, that is, aperture setting means 24, speed control means 25, and flash light control constant resetting means 26 are formed.

In flash photography, the amount of light emitted by the flash 22, ie, the guide number (GNO), and the output of the AF sensor 20, ie, the distance measurement value (D) are taken in, and the aperture setting means 24 calculates the aperture at the time of flash emission ( #
3) The speed control means 25 controls the speed of the shutter blade drive motor so that the calculated value becomes a shutter blade speed that can be realized at the time of flash emission (# 4, #).
5). Then, the actual aperture value after the motor stops is detected (#
6) If there is an error between the calculated aperture value and the initial aperture value, the flash dimming constant (guide number integrated dimming constant) as a setting condition is corrected based on the actual aperture value (# 7) and corrected. Flash emission is performed based on the flash dimming constant (#
8) When the light emission amount matches the corrected dimming constant, the light emission is stopped (# 9), the shutter is closed (# 10), and the flash photography is terminated.

[Effects of the Invention] According to the camera using the imaging device of the present invention, it is possible to accurately control the amount of flash light without performing high-precision aperture drive control, and to perform flash light emission shooting with an appropriate exposure. Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram of a flash photography control device showing an embodiment of a camera using an image sensor according to the present invention. FIG. 2 is a block diagram showing an embodiment of a camera using an image sensor according to the present invention. FIG. 3 is a flowchart showing the operation of the camera using the image sensor according to the present invention, FIG.
FIG. 5B is a front view of a shutter portion of an electronic camera using a CCD as an image sensor as an embodiment of a camera using the image sensor according to the present invention, and FIGS. FIG. 7 shows a relationship between an aperture value of a camera having a light control device and a flash emission time, and FIG. 7 shows a characteristic diagram of a shutter blade. 1,2 Shutter blade 4 Shutter plate 5 Driven gear 6 Pulse sheet 7 Photo interrupter 23 Control circuit

Claims (1)

(57) [Claims] An image pickup device for receiving a light beam incident through an aperture of the shutter; a control circuit for processing and recording an image signal from the image pickup device; The reflected light from the object is received by the sensor, and the amount of flash light is monitored based on the amount of received light, and the amount of flash light reaches a predetermined value corresponding to the strobe light control constant set in accordance with the shutter opening value. In a camera using an image sensor that performs flash photography with an external dimming strobe device that stops flashing when the shutter is opened, the shutter is opened according to data from the data forming means that forms data according to the distance to the object An information setting means for setting value information; and driving a shutter to shift a shutter aperture to an aperture value of the aperture value information based on the aperture value information set by the information setting means. A drive circuit, a detecting means for detecting information corresponding to an actual aperture value at the end of shutter driving by the drive circuit, and a strobe control of the external light control type strobe device according to the information detected by the detecting means. A camera using an image sensor, comprising a strobe light control constant setting unit for setting a light constant.