JPH0731342B2 - Camera exposure controller - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure control device for a camera, and more particularly to an exposure control device for a camera having a variable focal length lens and a shutter that also serves as an aperture.

[Prior Art] As is well known, when the focal length of a taking lens of a camera changes, its open F value also changes. Therefore, if you have an EE camera with an automatic exposure control device that incorporates two types of lenses, telephoto and wide-angle, and use a fixed aperture in common, the F value of the aperture will differ depending on the focal length of the lens. I have to make some EE correction here. Conventionally, this correction means is a type in which a dark filter (ND filter) is combined with a wide-angle lens in advance, or the amount of light received by the light-receiving element is adjusted by switching between telephoto and wide-angle (Actual number 58-103025). (Japanese Laid-Open Patent Publication No. 53-25433), or the one in which the capacitance of the integrating capacitor in the EE circuit is switched between telephoto and wide-angle.

On the other hand, in an EE camera using a zoom lens as a photographing lens, in general, the aperture error amount gradually changes from zero to a large value as the focal length of the zoom lens changes from the shortest focal length to the long focal length. Therefore, in such an EE camera with a zoom lens, a means for correcting an ENo error due to zooming by exposure calculation of a CPU (central processing unit) in a microcomputer (Japanese Patent Laid-Open No. 58-169135).
No. gazette) is proposed.

[Problems to be Solved by the Invention] As described above, although various conventional EE correction means are provided for the error of the FNo caused by the change in the focal length, these are all EE devices. Was independently constructed, and its structure was complicated and expensive. Further, there is a correction means that can be used for two types of lenses for switching between telephoto and wide angle, but cannot be used for a zoom lens, and a very complicated correction circuit was required even for zooming.

In particular, when a zoom lens is combined with an EE camera that employs a program shutter that also functions as a diaphragm, the conventional correction means cannot be used as it is because it also functions as a diaphragm shutter. Moreover, it becomes completely unsuitable when a flashmatic mechanism or the like is incorporated.

Therefore, an object of the present invention is to provide an exposure of a camera having an EE correction means that is optimal for an EE camera that employs a shutter that also serves as an aperture and uses two types of lenses for switching telephoto / wide-angle and variable focal length lenses such as zoom lenses. To provide a control device.

[Means and Actions for Solving Problems] The exposure control device according to the present invention is used as a variable point lens for changing the open F value in accordance with a change in focal length, and a diaphragm that is opened and closed by an electromagnetic drive source. A shutter, a detection unit that detects focal length information according to a change in the focal length, and an opening / closing speed required for the shutter opening that is determined before the operation of the shutter corresponding to the detected focal length information are obtained. As described above, the shutter opening / closing speed control circuit for changing the driving speed of the electromagnetic driving source is provided.

[Embodiment] The present invention will be described below with reference to an embodiment shown in the drawings.

First, the basic principle of the present invention will be described with reference to FIGS. In the present invention, the shutter including the shutter blade that also serves as the diaphragm is automatically driven by a motor that is an electromagnetic drive source (hereinafter, this is referred to as a motor shutter).

Further, in the present invention, the opening / closing speed of the shutter is controlled in accordance with the focal length information obtained by detecting the change in the focal length of the lens, thereby performing the EE correction. That is, as shown in FIG. 1, first, a change in the focal length of the lens due to the switching between telephoto and wide angle, or in the zoom lens, a change in the lens focal length due to zooming is detected as lens focal length information. The detected lens focal length information is input to the shutter opening / closing speed control circuit and the trigger timing adjustment circuit, respectively. The rotation speed of the motor of the motor shutter is controlled by the output of the speed control circuit.

On the other hand, the opening / closing mechanism of the shutter is driven by this motor, the trigger switch (see FIG. 2) is activated in connection with this, and after the time t ₀ determined by the trigger timing adjustment circuit, the EE exposure control circuit An operation start signal is output to the strobe light emission timing control circuit.
The EE exposure control circuit is well-known, and subject brightness information, film sensitivity information, etc. are input, and as is well known to the strobe emission timing control circuit, distance information, GNo (guide number) information, Film sensitivity information etc. have been entered. And the proper exposure time t _E (See Fig. 2)
Then, the shutter closing magnet 23 operates to close the shutter. Further, the strobe light emission timing control circuit generates a signal for energizing the strobe trigger thyristor at the time t _F (see FIG. 2) when the shutter is opened at the aperture opening determined by the GNo information and the distance information. However, the flash is properly emitted.

As described above, according to the present invention, the opening / closing spade of the shutter is adjusted according to the change of the focal length of the lens, and the EE correction is performed by this. Next, the gist of the present invention will be described in a little more detail with reference to FIG. To do. For example, consider a case in which the FNo on the telephoto side (hereinafter, referred to as T side) is darker by one step than the wide angle side (hereinafter, referred to as W side) by switching the focal length (provided that the aperture opening diameter is the same). The shutter opening waveform W at the wide angle is shown by a thick line, but the trigger timing adjusting circuit determines the time t ₀ so that the opening start of the shutter coincides with the integration start of the EE control or the strobe control. Here, when the lens is switched to the T side, W
If the shutter is opened with the same shutter opening waveform as the side, the exposure will be under by 1 EV due to the difference in FNo.

Therefore, in the present invention, on the T side, the shutter opening speed is increased to double the opening area within the same exposure time t _E (S _E →
Since it was set to be 2S _E ), this gives the proper exposure. Further, when the shutter opening speed is increased, the time until the opening of the shutter is increased by Δt _0, so the correction is made so that t ₀ ′ = t ₀ −Δt ₀ .

Further, if the correction is made as described above, the aperture opening area at the time of stroboscopic light emission is also S _F → 2S _F , so that this can be corrected at the same time when the flashmatic mechanism is provided.

The above-mentioned changes in shutter opening speed are generally based on the standard FN.
When the nAV lens changes with the AV value (apex calculation value) with respect to o, the open area S may be changed so as to satisfy S = 2 ⁿ × S ₀ (S ₀ is the opening area at the reference FNo). .

3, 4 and 5 show an embodiment of the present invention using a motor shutter. 2 sectors that double as aperture
The drive mechanism of the program shutter 1 consisting of 1a and 1b is
As shown in FIG. 3, a reversible motor that is an electromagnetic drive source.
An output gear 12 fixed to the output shaft of 11 rotates a drive gear 14 via an idle gear 13 in the same direction as the motor 11. On the surface of the drive gear 14, a cam 15 for opening and closing the trigger switch is provided on the support shaft of the gear 14 so as to be integrated with the gear. The cam 15 is formed of a plate cam, and one of the movable contact pieces 16a, 16b of the trigger switch 16 is in pressure contact with the cam surface. Further, a cam engaging pin 17 is provided on the back surface of the gear 14.
A cam groove 14a into which b is fitted is provided. This cam groove 14
The a is formed by a gradually opening cam whose radius from the center point O of the gear 14 continuously changes. That is, the cam groove 14a is formed such that the groove width is slightly larger than the diameter of the cam engaging pin 17b, the one end portion 14d is formed to have the smallest radius, and the other end portion 14c is formed to have the largest radius. There is.
The cam groove 14a is formed between the one end 14d and the other end 14c such that the radius from the center point O gradually increases.

In addition, the above sector 1 which is a shutter blade that also serves as an aperture
The shutter drive unit for driving the opening and closing of a and 1b is arranged at the rear of the drive gear 14 and has a sector opening / closing pin 17a and the same lever that is set up at the end of one arm extending above the sector opening lever 17. The cam engaging pin 17b that is fixed to the other arm end that extends downward of 17 is the inclined groove 1c for opening and closing 1c, 1d of the sector 1a, 1b and the cam groove provided in the drive gear 14, respectively. It is designed to fit into 14a.

The sector opening lever 17 is a lever in which the other arm has an inverted "U" shape, and the fulcrum of the center part thereof is rotatable about a support shaft 19 fixed near the tip of the sector closing lever 18. It is pivotally attached.

The sector closing lever 18 is formed of a substantially linear arm member having substantially the same length as the sector opening lever 17, and the base end portion above the arm member is rotated around a support shaft 20 fixed to an immovable member. The armature 21 is rotatably pivotally mounted, and an armature 21 is swingably supported by a support shaft 18a at a tip end portion of a free end portion extending downward. To the upper left of this support shaft 18a (3rd
(In the figure), the support shaft 19 is provided. Also,
The free end of this sector closing lever 18 has a small hole for spring application.
18b is provided, and a tight coil spring 22 is applied to the small hole 18b to urge the sector closing lever 18 to the left. However, the rotation of the lever 18 due to this urging force is normally prevented by the cam engagement pin 17b of the lever 17 fitted in the cam groove of the smallest diameter portion of the cam groove 14a. The armature 21 is a small piece having a convex shape, and is attached to the lever 18 by rotatably fitting the substantially central portion of the armature 21 to the support shaft 18a. This armature
A magnet 23 having a coil 23a wound around a horizontal U-shaped core is arranged on the right side of 21.

In addition, the program shutter 1 has two sickle-shaped sectors 1 that form shutter blades that also serve as diaphragms.
a, 1b, the sectors 1a, 1b are arranged so as to face each other and overlap each other, and the bases thereof are rotatably supported by support pins 24a, 24b set up on a shutter support plate (not shown), The sector opening / closing pin 17a is inserted into a common opening of the inclined elongated holes 1c and 1d which are provided in the vicinity of the base portion and overlap each other. The exposure opening 1e is opened and closed by the movement of the sector opening / closing pin 17a.

On the other hand, a photographing optical system shown in FIG. 4 is arranged in front of the program shutter 1. This optical system has a focusing lens and a zoom lens in the lens barrel 30, and the zooming operation is performed by the lens barrel 30.
It is designed to be performed by a zoom ring 31 that rotates around the.

In the present embodiment, a detection unit that detects focal length information according to changes in the focal length is provided in association with the zoom ring 31.

That is, the projection 31a is integrally provided on the zoom ring 31, and the base of the sliding contact conductive contact 32 that constitutes the variable resistors VR ₁ and VR ₂ is fixed to the projection 31a. The focal length information detection unit is composed of two variable resistors VR ₁ and VR ₂ whose resistance values change by the rotation of the zoom ring 31, and the first contact piece 32a of the conductive contact piece 32 is a substrate. Pattern printing on 33,
Sliding on the VR ₂ resistor 34a formed by coating,
The second contact piece 32b slides on the VR ₁ resistor 34b. The third contact piece 32c is adapted to slide on the ground terminal 34c.

Then, the variable resistors VR ₁ and VR ₂ configured in this way are
The shutter opening / closing speed control circuit and the trigger timing adjusting circuit are respectively connected. FIG. 5 shows specific electric circuits of the shutter opening / closing speed control circuit 40 and the trigger timing adjusting circuit 50 to which the variable resistors VR ₁ and VR ₂ are connected, respectively.

That is, the resistance values of both variable resistors VR ₁ and VR ₂ are variable in association with the change (FNo change) of the focal length of the lens as described above, and one variable resistor VR ₁ has a fixed resistance. 41 is connected in series with the power supply voltage supply line L to form a voltage dividing circuit, and the voltage divided by the circuit is applied to one input terminal of the operational amplifier 42 of the speed control circuit 40. It has become so. Also this op amp
The output terminal of 42 is connected to the base of a transistor 43, the emitter of the transistor 43 is connected to the line L, and the collector is connected to the other input terminal of the operational amplifier 42 and the reversible driving motor 11. . The capacitor 44 connected in parallel with the motor 11 is a capacitor for absorbing back electromotive force.

The other variable resistor VR ₂ forms a series circuit with the capacitor 51 and is connected to the voltage supply line L, and the above-mentioned second time t ₀ in the trigger timing adjusting circuit 50 (second
(See the figure) to form a CR circuit. The trigger switch 16 is connected in parallel to the condenser 51 of this CR circuit.
(See FIG. 3) are connected. The connection point of this CR circuit is connected to one input terminal of the comparator 52,
The other input terminal of 52 is connected to a voltage dividing point of a voltage dividing circuit formed by connecting fixed resistors 53 and 54 in series. This voltage dividing circuit serves to generate a reference voltage for comparison of the comparator 52. The base of a transistor 55 is connected to the output terminal of the comparator 52, the emitter of the transistor 55 is grounded, and the output signal is output from the collector to the EE exposure control circuit 56 and the strobe light emission timing control circuit 57. There is.

In the shutter opening / closing speed control circuit 40 configured as described above, if the resistance value of the variable resistor VR ₁ changes due to the rotation of the zoom ring 31, the potential at the point changes and the output of the operational amplifier 42 changes. , The terminal voltage of the motor 11 changes. Therefore, the rotation speed of the motor 11 changes, and as a result, the aperture area of the diaphragm / shutter becomes S = 2 ⁿ × S ₀ as described above, and proper exposure according to the change in focal length can be obtained.

Further, when the resistance value of the variable resistor VR ₂ changes, the time t ₀ from when the trigger switch 16 is turned off to when the comparator 52 is inverted changes.
Correct t ₀ ′ = t ₀ −Δt ₀ .

Next, the operation of the shutter drive mechanism shown in FIG. 3 will be described. When the shutter release button is pressed, the magnet
23 and motor 11 are energized. Since the distance between the magnet 23 and the armature 21 is relatively large in this state, the armature 21 is not attracted to the magnet 23 and the magnet 23 is only in the excited state. When the motor 11 is energized, the output gear 12 of this motor 11
Rotates counterclockwise (hereinafter referred to as forward rotation) as indicated by an arrow (a) in FIG. Due to this normal rotation, the drive gear 14 also rotates normally via the idle gear 13. The forward rotation of the drive gear 14 causes the radius of the cam engagement pin 17b fitted in the cam groove 14d from the center point O to gradually increase, so that the pin 17b moves counterclockwise, thereby causing the sector to move. The lever 17 also rotates counterclockwise with the opening / closing pin 17a as a fulcrum. Therefore, the sector closing lever 18 pivots counterclockwise against the elastic force of the coil spring 22 about the support shaft 20 as a fulcrum via the support shaft 19, and eventually the armature 21.
Is attracted to the magnet 23 which is excited. The normal rotation of the drive gear 14 also causes the switch cam 15 to normally rotate, and the contact piece 16a of the trigger switch 16 is disengaged from the cam surface 15a, whereby the trigger switch 16 is turned on. And
A microcomputer (not shown) measures a certain time from the start of the normal rotation of the motor 11 by an internal oscillator,
When this fixed time elapses, a reverse rotation signal is output to the motor drive circuit (not shown) to reverse the rotation of the motor 11.
At this time, the sector closing lever 18 moves the armature 21
However, since the magnet 23 is attracted and held by the energized magnet 23, the sector closing lever 17 rotates clockwise about its supporting shaft 19 as a fulcrum. By this rotation, the sector opening / closing pin 17
Since a also moves in the clockwise direction, the sectors 1a and 1b start the opening operation.

On the other hand, since the trigger switch cam 15 is also reversed, the trigger switch 16 has one contact piece 16a pushed by the cam surface 15a,
It turns from on to off. From this point, the trigger timing adjustment circuit 50 (see FIG. 5) operates, and after a predetermined time (t ₀ ) the EE exposure control circuit 56 and the strobe light emission timing control circuit.
Start 57. Subsequently, exposure control is performed, and at time t _E (see FIG. 2) when an appropriate exposure value corresponding to the brightness of the subject is obtained, the magnet 23 is de-energized. Then, since the armature 21 is released from the magnet 23, the sector closing lever 18 is pulled leftward by the coil spring 22 and rotates clockwise around the support shaft 20 as a fulcrum. Therefore, since the sector opening lever 17 rotates counterclockwise about the cam engagement pin 17b as a fulcrum, the sector opening / closing pin 17a also rotates counterclockwise, and as a result,
The sectors 1a and 1b are closed. That is, proper exposure can be obtained during this period.

In the flash mode, the proper timing t _F (second
(See the figure), the flash fires and the proper exposure is obtained.

Thus, according to this embodiment, the focal length (FN
There are two resistors interlocked with the change in o), one resistor changes the shutter opening speed, and the other resistor corrects the time until the start of sector opening due to the change of the shutter opening speed. As a result, accurate EE correction can be performed according to the change in FNo.

Although the motor-driven shutter is used as the aperture / shutter that is opened / closed by the electromagnetic drive source in the above-described embodiment, it is needless to say that the shutter can be applied to a shutter having an electrically variable shutter opening speed, for example, an electromagnetic drive shutter.

[Effects of the Invention] As described above, according to the present invention, with respect to a change in the focal length (FNo) in an EE camera having two types of a telephoto-wide angle switch lens and a variable focal length lens such as a zoom lens, It is possible to provide a camera exposure control device capable of performing optimum EE correction simply by providing a simple electric circuit.

Further, the present invention can correct not only the EE correction but also the flashmatic device, if this is provided.

[Brief description of drawings]

1 and 2 are electric circuit block diagrams for explaining the basic principle of the present invention and a diagram showing a shutter opening area. FIG. 3 is a diagram showing an exposure control device for a camera showing one embodiment of the present invention. FIG. 4 is a front view of the shutter drive mechanism, FIG. 4 is a perspective view showing an example of a focal length information detection unit, and FIG. 5 is a specific electric circuit diagram of a trigger timing adjustment circuit and a shutter opening / closing speed control circuit. 1 ...... combination aperture shutter 40 ...... shuttering speed control circuit 50 ...... trigger timing adjustment circuit VR _1, VR ₂ ...... focal length information detecting unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-169135 (JP, A) JP-A-58-130328 (JP, A) JP-A-53-25433 (JP, A) JP-A-61- 162032 (JP, A) JP 62-3236 (JP, A) Actually opened 58-182923 (JP, U) Actually opened 58-103025 (JP, U)

Claims (1)

[Claims] 1. A focal length variable lens in which the open F value also changes in accordance with a change in focal length, an aperture / shutter that opens and closes by an electromagnetic drive source, and focal length information is detected in accordance with a change in focal length. And a shutter that changes the drive speed of the electromagnetic drive source so that the opening / closing speed required for the shutter opening that is determined before the operation of the shutter can be obtained corresponding to the detected focal length information. An exposure control device for a camera, comprising: an opening / closing speed control circuit.