JP2533176B2 - Camera exposure controller - Google Patents

Description

The present invention relates to an exposure control device for a program AE type camera.

[Conventional technology]

The autofocus device is composed of a distance measuring device that detects a distance measuring signal corresponding to a subject distance, and a lens moving device that moves a photographing lens to a position corresponding to the distance measuring signal. In recent popular compact cameras and electronic still cameras, the active type is often used as the distance measuring device. An active distance measuring device projects, for example, light for distance measurement (generally infrared light) toward a subject, receives the light reflected from the main subject among this light, and detects the subject distance by the triangulation distance measurement method. To measure the distance.

By the way, when using the active distance measuring device, when the subject distance exceeds, for example, 10 m, the distance measuring light reflected from the subject becomes extremely weak and may be detected as a significant signal. It will be difficult. Therefore, until now, the farthest set position of the photographing lens has been set to a position at which the distance to the subject is in focus, for example, a subject distance of 10 m, and the distance measuring light reflected from the subject is detected. When it is not possible, the photographing lens is moved to the farthest setting position and photographing is performed.

[Problems to be explained by the invention]

However, according to the above method, the photographing lens is set at a position where the in-focus position is 10 m even for a subject at infinity, and the focus is often poor.

In order to reduce such an adverse effect, it has been attempted to manually move the taking lens to a position where it is in focus at infinity, but such a method only complicates the taking lens moving mechanism. Of course, for subjects between 10m and infinity, it is inevitable that the subject will be out of focus.

[Object of the Invention]

The present invention has been made to solve the above problems, and an exposure control device for a camera that can obtain sharpness equivalent to short-distance shooting even in long-distance shooting without complicating the structure of the camera. The purpose is to provide.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a first program exposure unit that performs exposure with a shutter speed and an aperture value that are determined corresponding to subject brightness, and the subject brightness is within a predetermined range or below this predetermined range. At a certain time, a second program exposure unit for performing exposure control with priority given to a smaller aperture than the first program exposure unit or priority given to a shutter speed in which hand shake is less likely to occur is provided, and the photographing lens is set to a predetermined farthest photographing position. An exposure control device for a camera that uses the second programmed exposure means only when set is configured.

[Action]

According to the above, the first
The exposure control is performed according to the program exposure means, the second program exposure means is used for the farthest photographing position, and when the subject brightness is within a predetermined range, the exposure control is performed with a smaller aperture than the first program exposure means. When the subject brightness is equal to or lower than the predetermined range, shutter speed priority exposure control that is slower than the first program exposure unit and is less likely to cause camera shake is performed, and exposure control according to the subject brightness can be performed in this range. As a result, it becomes possible to shoot an object beyond the range-finding limit while suppressing blurring and camera shake.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

〔Example〕

In FIG. 2, which is an external view of a compact camera incorporating the exposure control device of the present invention, a taking lens 14 is provided on the front surface of a camera body 10 so as to be movable back and forth along an optical axis 13. Reference numerals 16 and 17 denote a light emitting window and a light receiving window for distance measurement,
Behind this, an active distance measuring device 27 described later is arranged. Reference numeral 18 indicates a photometric window, behind which a photometric device described later is arranged. A shutter button 19 is provided on the upper surface of the camera body 10.

In FIG. 1, which is a schematic explanatory view of the electrical configuration of the present embodiment, a release signal generation circuit 20 detects half-pressing operation and full-pressing operation of the shutter button 19 and outputs these operation signals to the CPU 22. , Executes the processing written in the sequence program ROM 29. Further, the photometric device 21 is provided behind the photometric window 18, detects the subject brightness, and supplies it to the CPU 22 as a digitized brightness signal.

Conceptually, the first exposure program ROM 31 associates the EV value with the shutter speed and the aperture value, as shown by the solid line S1 in FIG. 3, so that the proper exposure can be obtained according to the subject brightness. A combination of a different shutter speed and aperture value is uniquely determined. According to this first exposure program S1,
For example, the EV17 has a shutter speed of 1/500 second and aperture value of F1.
The EV11 has a shutter speed of about 1/100 second and an aperture value of about F4.8. The first exposure program S1 is an active distance measuring device, as will be described later in detail.
Referenced when the ranging signal is obtained from 27.

The second exposure program ROM 32 determines the combination of the shutter speed and the aperture value with respect to the EV value, as shown by the broken line in FIG. According to the second exposure program S2, the EV17 has a shutter speed of "1/500 seconds" and an aperture value of "F16" as in the case of the first exposure program S1, but between EV10 and EV12 within a predetermined range. In, the aperture value is fixed to "F5.6", the shutter speed changes according to this aperture value,
For EV10 and below, which is below the specified range, the shutter speed is "1 /
It is fixed to "30 seconds", the aperture value changes according to this shutter speed, and the combination is different from that of the first exposure program S1. The second exposure program S2 is referred to when the distance signal L is not obtained from the active distance measuring device 27.

The active distance measuring device 27 includes the light emitting / receiving windows 16 and 17 shown in FIG.
It is composed of a projector 23, a light receiver 26, and a distance detection circuit 24 which receives a photoelectric signal from the light receiver 26 and outputs a distance signal L. As is well known, an infrared light emitting diode or the like that projects infrared light toward a subject is used for the light projector 23, and a position detection sensor (PSD) or the like is used for the light receiver 26. Further, the lens moving device 34 corresponds to the distance signal L obtained by the distance detection circuit 24 and the photographing lens 14
Is moved in the direction of the optical axis 13 to adjust the focus.

The shutter drive device 39 and the aperture drive device 38 are shutters so that the shutter speed and aperture value determined by the above-mentioned first or second exposure program ROM 31, 32 are realized.
By driving 37 and the diaphragm 36, the film 41 can be properly exposed.

Hereinafter, the operation of the present embodiment having the above configuration will be described with reference to the flowchart of FIG.

When the shutter button 19 is pressed halfway down, the CPU 22 drives the light projector 23, and infrared light for distance measurement is projected toward the subject. When the distance to the main subject is within 10 m, the reflected light is detected by the light receiver 26, and the distance signal L is input to the distance detection circuit 24. In this way, when the distance signal L is obtained from the active distance measuring device 27, the photographing lens 14 is moved to the position corresponding to the distance signal L by the driving of the lens moving device 34, and focus adjustment is performed.

When the focus adjustment is completed in this way, the shutter button 19
Is fully pressed, and the exposure sequence is executed by the full pressing operation. The processing of the exposure sequence differs depending on whether the distance signal L is obtained from the active distance measuring device 27 or not. That is, when the distance signal L is detected, the CPU 22 determines the shutter speed and the aperture value by referring to the first exposure program ROM 31 based on the brightness signal at that time. The CPU 22 operates the shutter drive device 39 and the aperture drive device 38 according to the shutter speed and the aperture value thus determined, so that the exposure is performed.

On the other hand, when the distance signal L is not obtained from the active distance measuring device 27, it is assumed that the distance to the main subject is long and the infrared light for distance measurement is attenuated and does not return to the light receiver 26. Therefore, the CPU 22 moves the taking lens 14 to the farthest setting position via the lens moving device 34. This farthest set position has a subject distance of 10 m, which is the farthest side distance limit of the active distance measuring device 27, as the in-focus position.

When the shutter button 19 is fully pressed after the photographing lens 14 moves to the farthest setting position, the CPU 22 determines the shutter speed and the aperture value by referring to the second exposure program ROM 32 based on the brightness signal at that time. In this way, when the exposure control is performed by the second exposure program S2, as is apparent from FIG.
Aperture-priority exposure control in which the aperture value is limited to “F5.6” is performed, and the depth of field can be deeper than that during exposure control by the first exposure program S1.

FIG. 5 shows this state, in which the taking lens 14 at the farthest setting position converges the light flux 50 from the subject 10 m away on the film 41. When the diaphragm 36 remains "F4.8" by the first exposure program S1, the light flux 52 from infinity is converged to a position further away by a distance 1 than the film 41, and the diameter of the circle of confusion on the film 41 is becomes ε '.

On the other hand, when the diaphragm 36 is set to "F5.6" by the second exposure program S2, the light flux 53 from infinity is similarly converged forward by the distance 1 from the film 41, but on the film 41. The confusion circle diameter at is ε. And this confusion circle diameter ε can be generally regarded as the in-focus state.
Since it can be suppressed to about 03 mm, it is possible to focus a subject at a distance of 10 m or more to a satisfactory degree. Further, when the subject brightness exceeds EV12, the diaphragm 36 can be sufficiently narrowed down even with the first exposure program S1, so that there is no problem in matching the second exposure program S2 with the first exposure program S1 in this region. .

In the second exposure program ROM 32, the subject brightness is E
If V10 or less, the shutter speed is fixed to "1/30 second" at which camera shake is less likely to occur, and exposure control with shutter speed priority is performed. As a result, it is possible to prevent the occurrence of camera shake at low brightness. In this case also, in most cases, the image is taken with a smaller aperture value than the aperture value determined by the first exposure program S1, and therefore the same effect is obtained in terms of increasing the depth of field.

The present invention has been described above with reference to the illustrated embodiment, but the present invention is equally applicable to a still video camera in which a solid-state image pickup device such as a CCD image sensor is arranged at the position of the film 41. In this case, if the shutter speed is controlled by controlling the charge storage time of the solid-state imaging device for imaging, the shutter device 37 that mechanically opens and closes the shutter blades can be omitted.

〔The invention's effect〕

As described above, according to the present invention, the first program exposure unit that performs exposure with the shutter speed and the aperture value determined corresponding to the subject brightness, and when the subject brightness is within the predetermined range or below the predetermined range And a second program exposure means for performing exposure control with a smaller aperture priority than the first program exposure means or with a shutter speed priority in which camera shake is less likely to occur, and the photographing lens is set at a predetermined farthest photographing position. The second programmed exposure means is used only when Therefore, it is possible to reduce the diameter of the circle of confusion for a subject beyond the range-finding limit of the active AF device. As a result, blurring can be suppressed to a small level, sharpness equivalent to that at short-distance shooting can be obtained, and the occurrence of camera shake can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of an exposure control device using the present invention. FIG. 2 is an external view of the camera according to the embodiment of FIG. FIG. 3 is a schematic diagram of the AE program according to the embodiment of FIG. FIG. 4 is a flow chart showing the processing according to the embodiment shown in FIG. FIG. 5 is an explanatory view of the operation of exposure control by the second exposure program. 10 …… Camera body 14 …… Shooting lens 16 …… Emitter 17 …… Receiver 18 …… Metering window 21 …… Metering device 22 …… CPU 27 …… Active rangefinder 29 …… Sequence program ROM 31 …… No. 1st exposure program ROM 32 …… Second exposure program ROM 36 …… Aperture 37 …… Shutter S1 …… First exposure program S2 …… Second exposure program

Claims (1)

(57) [Claims] 1. An exposure control device for a camera, comprising an autofocus device, which corresponds to an output from an active distance measuring device and which sets a taking lens between a close-up position and a predetermined farthest shooting position, First program exposure means for performing exposure control by a shutter speed and an aperture value determined corresponding to subject brightness when the taking lens is set between the closest distance position and the farthest photographing position by the autofocus device, Second used when the lens is set to the farthest shooting position
And a second program exposure means, wherein the second program exposure means includes a first program exposure means when the subject brightness is within a predetermined range.
The shutter speed is combined with an aperture value that is smaller than the aperture value determined by the program exposure unit as a reference, and when the subject brightness is equal to or higher than the predetermined range, the same exposure control as that of the first program exposure unit is performed to determine the subject brightness. When the value is less than or equal to the predetermined range, exposure control is performed by combining aperture values with reference to a shutter speed that is slower than a shutter speed determined by the first program exposure unit and is less likely to cause camera shake. Exposure control device.