JPS6250819A - Exposure controller for electronic camera - Google Patents

Abstract

PURPOSE:To simplify structure and to improve the precision of exposure control by providing two sector blades rotatably to a lens aperture and driving them by a stepping motor which is controlled by an exposure program. CONSTITUTION:A CPU 8 receives a signal from a subject brightness measuring circuit 12 and accesses a data storage ROM 13 for automatic iris operation and a data storage ROM 14 for shutter operation. The ROM 13 is stored with an optimum aperture for subject brightness as data and the ROM 14 is stored with the optimum quantity of exposure for the subject rightness. A stepping motor driving circuit 15 outputs driving pulses for rotating the stepping motor on the basis of the data read out of the ROMs 13 and 14. Then, still picture photography and motion picture photography are brought under programmed control according to the subject brightness. Thus, the exposure control is carried out precisely by the simple structure.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an exposure control device suitable for an electronic camera capable of capturing moving images and still images.

(Prior Art) In recent years, cameras that use a solid-state imaging device such as a charge-coupled device (CCD) to convert a subject image into an electrical signal and store this signal in a small storage medium such as a magnetic floppy disk have been developed. So-called electronic cameras have been put into practical use. - Since this electronic camera processes the subject image as an electrical signal, it is possible to record video by simply connecting an external device such as a video tape recorder with a large storage capacity, so it can also be used as a video camera. is proposed.

Incidentally, regardless of whether the camera is an optical camera or an electronic camera, an aperture mechanism and a shutter mechanism are required for still image photography, and an automatic aperture mechanism, so-called auto-iris, is required for video photography. For this reason, when attempting to shoot still images and videos at the same time, both the shutter mechanism and the iris mechanism must be placed in the narrow space between the photographing lens and the photographing element, which complicates the structure. was there.

In order to solve such problems, Japanese Patent Application Laid-Open No. 60-834
As shown in Publication No. 74, there is a movable plate that rotatably supports the end of the aperture blade that also serves as a shutter around the opening and has an armature coil on its surface, and a movable plate that rotatably supports the end of the aperture blade that also serves as a shutter, and a movable plate that has an armature coil on its surface, and An exposure control device for an electronic camera, in which a substrate is assembled so as to be relatively rotatable, and a substrate is provided with an engaging pin surrounding an opening and a magnet that cooperates with an armature coil to form an electromagnetic drive mechanism. is proposed. According to this, by rotating the aperture blades using the electromagnetic drive mechanism, it becomes possible to serve both as a shutter when photographing still images and as an auto iris when photographing moving images.

However, the structure is not only complicated due to the large number of pins that regulate the movement of the diaphragm blades around the aperture, the movable plate, and the electromagnetic mechanism that are arranged centrally around the aperture, but also the shutter is in a closed state and an open state when operating. There is a problem in that the exposure amount can only be controlled in two states, and the exposure control becomes rough.

(Objective) In view of these problems, it is an object of the present invention to provide an exposure control device for an electronic camera that has a simple structure and can perform fine exposure control.

(Structure) That is, the present invention is characterized in that two sector blades are rotatably provided in the lens aperture and are driven by a step motor controlled by an exposure program.

FIG. 2 shows an embodiment of an electronic camera to which the present invention is applied, and reference numeral 17 in the figure indicates a camera case 18.
The exposure amount control mechanism, which will be described later, is disposed on the optical path of the photographing lens 19 provided in the camera, and is rotated by a step motor 6 that receives a signal from the control section 20, and is used as an auto iris during video shooting. When taking a picture, when the release button 23 is pressed, the optical path C is used as a shutter.
It is configured to irradiate light onto a solid-state image sensor 21 such as an OD. Reference numeral 22 denotes a light-receiving element for detecting object brightness provided in the camera case 18, which outputs a brightness signal to the object brightness measuring circuit 12 in the control section 20. 23 is
This is a magnetic storage device that stores signals output from the solid-state image sensor 21 by operating the release button 24 on a magnetic sheet as a still image. Note that the reference numeral 28 in the figure is
Indicates a connector that outputs video signals to external equipment.

Therefore, details of the present invention will be explained below based on illustrated embodiments.

FIG. 1 shows an embodiment of the present invention, in which reference numerals 1 and 2 denote shafts 1 and 2 on a front plate having an opening 3, respectively.
A, a sector blade rotatably attached by 2a,
Notches 1b and 2b, which change the aperture opening degree as the aperture rotates in the closed state, are formed on the opposing end faces so as to be symmetrical about the optical axis, and a pin is implanted in one of the sector blades 2. , a through hole 1c through which a pin 2c is inserted is formed in the other sector blade 1, and the two are engaged with each other via the pin 2c. 4 is a drive lever rotatably attached to the base by a shaft 4a, and one end is connected to the 2 by a pin 2C.
The sector blades 1 and 2 are engaged with each other, and the other end is provided with a toothed portion 4.
b, and is connected to a step motor 6, which will be described later, via an intermediate wheel 5. 6 is the step motor mentioned above,
Coils 6a, 6at - core 6b wound and arranged oppositely
, 6b, and a rotor 6C that receives the magnetic flux from this, and is configured to rotate forward and reverse in a stepwise manner in response to pulse signals.
It is placed in a position where it meshes with the

Reference numeral 8 in the figure is a CPU, which is connected to one of the video shooting mode setting circuit 9 and the still image shooting mode setting circuit 10 via the shooting mode changeover switch 11, and receives a signal from the subject brightness measurement circuit 12. It is configured to have 7' access to an auto iris operation data storage ROM 13 and a shutter operation data storage ROM 14, which will be described later. Reference numeral 13 denotes the aforementioned auto-iris operation data storage ROM, which associates subject brightness with an address and stores the optimum aperture degree for the subject brightness as data. Reference numeral 14 denotes a shutter operation m data storage ROM in which the optimum exposure amount for the subject brightness is stored as data in correspondence with the subject brightness. Reference numeral 15 denotes a step motor drive circuit that outputs a drive pulse for rotating the step motor 6 based on data read from each ROM 13, 14. Note that reference numeral 16 in the figure indicates a release signal generation circuit that outputs a still image photographing signal in response to pressing of the release button 24.

Next, the operation of the apparatus configured as described above will be explained based on FIG. 3.

[Still and old image shooting mode] When the shooting mode changeover switch 11 is operated to select the still image shooting mode, a signal from the still and both shooting mode setting circuit 10 is input to the CPU 8, and the shutter operation data storage ROM 14 is accessed. It becomes possible.

In this state, the shirt release button 23
When pressed to the first stage, the sector blades 1 and 2 close to block light from the lens 19, discharge the charge accumulated in the solid-state image sensor 21, and prepare for still image photography.

When the shirt release button 23 is further pressed, the signal from the subject brightness measurement circuit 1z is accessed, data in the shutter actuation data storage ROM is accessed, and exposure data matching the subject brightness is sent to the step motor drive circuit 15. Output. As a result, the sector blades 1.2 receive rotation from the step motor 6 via the drive lever 4 and begin to rotate about the respective shafts 1a and 2a, thereby opening the lens aperture 3. When the opening corresponds to the subject brightness, the phase of the pulse signal is reversed and the step motor 6 is rotated in reverse. By reversing the step motor 6, the sector blades 1 and 2 reverse their rotational directions and close the lens aperture 3. As a result, the solid-state image sensor 21 detects the subject brightness -
The subject image is exposed with the matched optimal exposure amount,
Accumulates charges corresponding to the subject image. Solid-state image sensor 21
The accumulated charges are written on the magnetic sheet 25 as an imaging signal to form a still image.

[Video shooting mode] When the video shooting mode is selected by the shooting mode changeover switch 11, the signal from the video shooting mode setting circuit 9 is changed to C.
By inputting it to the PU 8, the auto iris operation data storage ROM 13 can be accessed.

As a result, the signal from the subject brightness measurement circuit 12 is taken in at a constant cycle and is stored in the data storage ROM 1 for auto iris operation.
3 and outputs the number of pulses matching the subject brightness to the step motor drive circuit 15. The step motor drive circuit 15 outputs a pulse signal corresponding to this number of pulses to rotate the step motor 6, and requests rotation of the step motor 6 when it has rotated by the number of pulses. As a result, the sector blades 1.2 are rotated by the step motor 6 to an aperture that matches the brightness of the subject to form an aperture aperture and maintain this aperture. In this way, the subject brightness measurement circuit 1
Data storage R for auto iris operation by signal from 2
The OM13 is accessed, and each time the subject brightness changes, the number of pulse signals corresponding to the change is output, and the step motor is rotated forward or reverse to follow the change in the subject brightness, and the sector blades 1.2 Adjust the opening degree.

As a result, the solid-state image sensor 21 always receives the optimum amount of light regardless of changes in subject brightness, and outputs the subject image as a photographing signal to an external device such as a video table recorder.

In the above embodiment, the lens aperture is closed by two sector blades, but it goes without saying that three or more sector blades can be provided to close the lens aperture.

(Effects) As described above, according to the present invention, the sector blades of the lens aperture that can be closed are driven by the driving means, so the structure is improved by decentralizing the light shielding member and the drive unit that drives it. Not only can this be simplified, but by selecting the shape of the notch in the sector blade, it is possible to set an exposure pattern suitable for the solid-state image sensor by combining the aperture pattern and the exposure time. In addition, since a step motor is used as the drive means, not only can digital control be applied to improve control accuracy, but it can also be matched with the signal processing format of electronic cameras, allowing the signal processing circuit to be shared. It becomes possible to convert into Furthermore, since the step motor is controlled by the storage means that stores the relationship between the subject brightness signal, the exposure amount, and the aperture degree, still image shooting and video shooting can be program-controlled according to the subject brightness.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a device constituting an embodiment of the present invention, Fig. 2 is a sectional view showing an embodiment of an electronic camera to which the same device is applied, and Fig. 3 shows the operation of the device shown in Fig. 1. FIG.

Claims (1)

[Claims] A first storage means includes a plurality of sector blades for closing an aperture facing the photographing lens, a step motor for rotating the sector blades, and stores a relationship between subject brightness and exposure amount; 1. An electronic camera exposure control device comprising: second storage means storing relationships between the following: and means for selecting one of said storage means according to a photographing mode and controlling rotation of said step motor.