JP3234991B2 - Peripheral light correction camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure system for a focal plane shutter type single-lens reflex camera, and more particularly to a method for equalizing a light amount difference between a central portion and a peripheral portion of a photographed image.

[0002]

2. Description of the Related Art Generally, in the case of a camera lens, the brightness of an image decreases as it goes away from the center.
The causes of the decrease in the brightness of the image include those caused by the imaging itself and those external to the structure of the lens barrel and the optical system. Assuming that the brightness of the off-axis image is E and the brightness of the center is E _O , there is a relationship of E = E _O cos ⁴ ω.

That is, the brightness of an off-axis image decreases in proportion to the fourth power of the cosine of the inclination ω of the principal ray incident on the optical system with respect to the optical axis.

Another factor that reduces the brightness of off-axis images is vignetting of the light beam by the lens holding frame, that is, vignetting. The luminous flux from the object point on the optical axis is circular on the entrance pupil plane, but the luminous flux from the off-axis object point is vignetted by the holding frame before and after the lens, the cross-sectional shape is no longer circular, and its area is also generally reduced. . The opening efficiency (%) is an evaluation amount that quantitatively represents this vignetting. This is because the reduction in brightness of the actual off-axis image of the off-axis light beam on the entrance pupil plane becomes COS ⁴ ω and the aperture efficiency.

[0005]

The aperture efficiency decreases as the angle of view increases, and in a wide-angle lens with the aperture open,
It is a big problem. The present invention solves the problem peculiar to this wide-angle lens by making the aperture value of the focal plane shutter and the aperture not constant during the shutter travel as in the conventional case, and increasing the aperture value at both ends of the film surface from the center of the film. It is an object of the present invention to provide a system for correcting a decrease in efficiency.

[0006]

In a focal plane type single-lens reflex camera, an adjusting means for adjusting the aperture of an interchangeable lens when a shutter is running is provided, and a light amount difference between a central portion and a peripheral portion of an image based on a characteristic inherent to the lens. The problem was solved by leveling.

[0007]

The adjusting means for adjusting the aperture of the interchangeable lens during the movement of the shutter is provided at a position near the start and stop of the shutter corresponding to the peripheral portion of the film surface. Is increased, the light amount difference between the central portion and the peripheral portion of the image based on the characteristic unique to the lens can be equalized.

[0008]

Embodiments of the present invention will be described below. FIG. 1 shows an external configuration of a camera body to which the present invention is applied, and FIG. 2 shows an external configuration of an interchangeable lens.

In the camera body 10 shown in FIG. 1, reference numeral 11 denotes a slider for turning on a main switch. When the slider 11 is in an ON position, the camera body 1 is turned on.
0 is in an operable state, and when in the OFF position, the camera body 10 is in an inoperable state.

Reference numeral 12 denotes a slider for turning on the peripheral light amount correction switch. When the slider 12 is in the ON position, the aperture ratio of the diaphragm is made larger than that at the center of the film surface to form an image based on the inherent properties of the lens. A peripheral light amount correction mode for leveling a light amount difference between the central portion and the peripheral portion is set.

Reference numeral 13 denotes a release button, and when the first step is depressed, the photographing preparation switch SWS is turned on to expose and release the image.
Each operation of exposure calculation / AF starts. In addition, the release switch SWR is turned on by pressing the second stage, and the exposure control operation starts.

Reference numerals 14a to 14h denote contact groups for supplying power and transmitting and receiving signals between the camera body 10 and the interchangeable lens 20.

Reference numeral 14a denotes a power supply contact for supplying a power supply voltage Vcc2 for driving the motor from the body side to the interchangeable lens side, and 14b denotes a power supply voltage VDD other than for driving the motor from the body side to the interchangeable lens side. Power contacts, 14
c is a contact for outputting a signal indicating a data communication request from the camera side to the interchangeable lens side; 14d is a contact for outputting a data communication clock signal from the camera side to the interchangeable lens side;
e is a contact for outputting data from the body side to the interchangeable lens side, 14f is a contact for inputting data from the interchangeable lens side to the body side, 14g is a ground contact of a circuit other than the lens motor driving circuit, and 14h is a lens. This is a ground contact of the motor drive circuit.

In the interchangeable lens 20 shown in FIG.
Reference numeral 24h denotes a group of contacts for supplying power and exchanging signals between the camera body 10 and the interchangeable lens 20.

Reference numeral 24a denotes a power supply contact for supplying a power supply voltage Vcc2 for driving the motor from the body side to the lens side;
b is a power supply contact for supplying a power supply voltage VDD other than for motor drive from the body side to the lens side, 24c is a contact for inputting a signal indicating a data communication request, and 24d is a clock signal for data communication input from the body side. 24e is a contact for inputting data from the body side, 24f is a contact for outputting data to the body side, 24g is a ground contact for circuits other than the motor driving circuit, and 24h is a ground contact for the motor driving circuit. is there.

Next, a circuit configuration of the camera system will be described with reference to FIGS.

FIG. 3 is a circuit diagram of an internal circuit built in the camera body 10.

ΜCOM1 is a microcomputer in the body (hereinafter, referred to as a microcomputer) for controlling the entire camera and performing various calculations.

The AFCT is a focus detection light receiving circuit, which includes a focus detection CCD, a CCD drive circuit, a circuit for processing the output of the CCD, A / D converting the data, and supplying the converted data to the microcomputer μCOM1. Microcomputer μCO via bus
It is connected to M1.

Reference numeral LM denotes a photometric circuit provided in the finder optical path.
COM1 is given as luminance information.

Reference numeral DX denotes a film sensitivity reading circuit which reads data such as film sensitivity provided in the film container and serially outputs the data to the microcomputer μCOM1.

LECT is a lens internal circuit built in the interchangeable lens 20 described later, and supplies information unique to the interchangeable lens to the microcomputer μCOM1.

TVCT is a shutter control circuit for controlling a shutter based on a control signal from the microcomputer μCOM1.

SWM is a main switch for enabling the operation of the camera.
Each time the pulse generator changes from FF to ON, the pulse generator PG outputs "Lo".
A w "level pulse is generated, and is input to the interrupt terminal INT2 of the microcomputer μCOM1 as an interrupt signal.

SWS is a shooting preparation switch which is turned on when the release button 13 is depressed at the first stage. When the shooting preparation switch SWS is turned on, the microcomputer μCOM
A preparatory operation required for photographing, such as photometry and AF operation, is performed by inputting an interrupt signal to the first interrupt terminal INT1.

SWV is a peripheral light amount correction switch for increasing the aperture ratio of the diaphragm from the center of the film surface and leveling the light amount difference between the central portion and the peripheral portion of the image based on the inherent properties of the lens. When the switch SWV is turned on, it is input to the interrupt terminal INT3 of the microcomputer μCOM1 as an interrupt signal.

Photometric circuit LM, film sensitivity reading circuit DX
Performs serial data communication with the microcomputer μCOM1 via signal lines of the serial input terminal SI, the serial output terminal SO, and the serial clock terminal SCK. And
Communication with the microcomputer μCOM1 is performed by the chip select terminal C
When the SLM is at the "Low" level, the photometric circuit LM is selected. When the chip select terminal CSDX is at the "Low" level, the film sensitivity reading circuit DX is selected. When the chip select terminal CSLE is at the "Low" level, the circuit LECT in the lens. Is selected.

FIG. 4 is a circuit diagram of an in-lens circuit LECT built in the interchangeable lens 20.

ΜCOM2 is built in the interchangeable lens 20,
Control of focus motor and aperture motor and camera body 1
This is a microcomputer that controls data communication with 0.

Reference numeral 24a denotes a power supply contact for supplying a power supply voltage Vcc2 for driving the motor from the body side to the lens side;
b is a power supply contact for supplying a power supply voltage VDD other than for motor drive from the body side to the lens side; 24c is a contact connected to the chip select terminal CSLE for inputting a signal indicating a data communication request from the camera side; Is connected to the clock terminal CSLE, a contact for inputting a clock signal for data communication from the body side, 24e is connected to the serial input terminal SI, and is a contact for inputting output data from the body side, and 24f is a contact from the serial output terminal SO. A contact for outputting data to the body side, 24g is a ground contact of a circuit other than the motor driving circuit, and 24h is a ground contact of the motor driving circuit.

The chip select terminal CSLE is connected to a contact 24c.
When a signal is transmitted from the microcomputer μCOM1 to the microcomputer μCOM2 via the microcomputer, an interrupt occurs in the microcomputer μCOM2, the microcomputer μCOM2 is activated, and the interchangeable lens is designated as a communication target with the body.

MD1 is a motor drive circuit for driving the focus motor M1, and controls the rotation of the focus motor M1 according to a control signal indicating the motor drive direction and the drive amount given from the microcomputer μCOM2.

MD2 is a motor drive circuit for driving the aperture motor M2, and controls the rotation of the aperture motor M2 according to a control signal indicating the motor drive direction and the drive amount given from the microcomputer μCOM2.

AVCT is the peripheral light amount correction switch SWV
When the aperture is set to N, the aperture of the aperture is made larger than the center of the film surface, and the aperture diameter is adjusted so as to equalize the difference in light amount between the central part and the peripheral part of the image based on the inherent properties of the lens. Circuit.

FIGS. 5 to 8 show, as an example, the open aperture F
The proper aperture when using the 2.8 interchangeable lens is F4.
FIG. 9 is an explanatory diagram showing the relationship between the operation of the focal plane shutter and the lens aperture when the shutter speed is 5;

In FIG. 5, when the front curtain 31 starts running and the slit 32 starts moving, the aperture of the interchangeable lens is in the state of F4, which is one step larger than the appropriate aperture. As shown in FIG. 6, the front curtain 31 advances, the rear curtain 33 follows, and the aperture of the interchangeable lens changes to F5.6, which is an appropriate aperture, near the center of the slit 32. Further, as shown in FIG. 7, the aperture of the interchangeable lens is held at an appropriate aperture of F5.6, and at the time shown in FIG. 8, the aperture of the interchangeable lens is again reduced to the state of F4.
Ends traveling and completes the exposure. In this way, the difference in light amount between the center and the periphery on the film surface is leveled.

FIG. 9 is a diagram showing the relationship between the position of the shutter slit and the correction of the aperture diameter. The central portion of the shutter slit position has an appropriate aperture diameter, and the left and right sides near the start and stop of the shutter are one step. By setting the aperture to an open aperture, the difference in light amount between the central part and the peripheral part of the image based on the properties unique to the lens is leveled.

Next, the operation of the peripheral light amount correction mode in the peripheral light amount correction camera will be described with reference to the flowchart of FIG.

When the photographing preparation switch is turned on by pressing the release button at the first stage, it is determined whether the photographing mode is the peripheral light amount correction mode or not. It is determined whether or not the optical system is of a type in which the amount of peripheral light decreases. Peripheral light amount correction mode
Normal shooting is performed without shooting in the peripheral light amount correction mode.

Next, the operations of exposure, exposure calculation and AF are started, the EV value is measured, and an appropriate shutter speed and aperture are determined. Then, it is determined whether the determined shutter speed is equal to or more than １ ／ of the fully open shutter speed. If the condition is not met, display a warning and return to the first step. Next, it is determined whether the determined aperture value is one or more stops smaller than the open aperture value. Similarly, if the condition is not met, a warning is displayed and the process returns to the first step.

When the release button is pressed in the second stage, the release switch is turned on, the exposure control operation is started, and the aperture of the interchangeable lens is set one step wider than the set aperture value. Then, shutter drive is started, and when the front curtain passes through 1/4 of the shooting screen, the aperture of the interchangeable lens is set to a set value. Then, when the rear curtain passes through 撮 影 of the photographing screen, the aperture of the interchangeable lens is set again to be one step larger than the set aperture value. When the shutter drive ends, the aperture of the interchangeable lens is set to the open state, and the photographing ends.

[0042]

According to the present invention, in a focal plane shutter camera, the problem of a decrease in the amount of peripheral light when using a wide-angle lens, particularly an ultra-wide-angle lens, can be realized without increasing the size of the interchangeable lens, and it is technically extremely difficult. The present invention can be realized without any improvement of the optical system, and provides a practical solution at extremely low cost.

[Brief description of the drawings]

FIG. 1 is an external configuration diagram of a camera body to which the present invention is applied.

FIG. 2 is an external configuration diagram of an interchangeable lens to which the present invention is applied.

FIG. 3 is a circuit diagram of an internal circuit incorporated in the camera body.

FIG. 4 is a circuit diagram of an in-lens circuit built into the interchangeable lens.

FIG. 5 is an explanatory diagram showing a relationship between a shutter operation and a lens stop.

FIG. 6 is an explanatory diagram showing a relationship between a shutter operation and a lens stop.

FIG. 7 is an explanatory diagram illustrating a relationship between a shutter operation and a lens stop.

FIG. 8 is an explanatory diagram showing a relationship between a shutter operation and a lens stop.

FIG. 9 is an explanatory diagram showing a relationship between a position of a shutter slit and correction of an aperture diameter.

FIG. 10 is a flowchart illustrating an operation of a peripheral light amount correction mode in the peripheral light amount correction camera.

[Explanation of symbols]

 10 Camera Body 20 Interchangeable Lens 31 Front Curtain 32 Slit 33 Rear Curtain AFCT Focus Detection Light Receiving Circuit AVCT Aperture Adjustment Circuit DX Film Sensitivity Reading Circuit LECT In-Lens Circuit LM Photometry Circuit M1 Focus Motor M2 Aperture Motor MD1 Motor Drive Circuit MD2 Motor Drive Circuit SWV Peripheral light correction switch TVCT Shutter control circuit μCOM1 microcomputer μCOM2 microcomputer

Claims (1)

(57) [Claims] In a focal plane shutter type single-lens reflex camera, there is provided an adjusting means for adjusting an aperture diameter at the time of shutter running so that a light amount difference between a central portion and a peripheral portion of an image unique to a lens is leveled. A peripheral light amount correction camera characterized in that: