JP2881987B2 - Auto focus camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an auto-focus camera, and more particularly to an auto-focus camera having an active-type distance measuring mechanism and capable of accurately focusing at infinity.

[Prior art]

In a conventional general auto-focus camera having an active-type distance measuring mechanism as described above, light for distance measurement emitted toward a subject is reflected from the subject and returned, and triangulation is performed. The subject distance is measured by applying the principle described above. In this distance measuring method, it is difficult to maintain the distance measuring accuracy because the reflected light becomes weaker as the subject becomes farther and the deflection of the distance measuring angle becomes smaller. For this reason, it is assumed that a subject located farther than a predetermined distance and at a position where distance measurement cannot be performed is roughly focused within the range of the depth of field, and is set by an automatic focusing mechanism corresponding to the subject position. Each position of the taking lens is set so as to focus on a subject within a range that can be measured. Therefore, even if the autofocus mechanism operates to focus on an object at infinity in landscape photography, for example, the camera will only roughly focus on the infinity position, and if the picture taken is greatly extended, it will be in focus. It is noticeable that it is sweet. As a technique for solving such inconvenience in photographing an object at infinity, for example, Japanese Patent Application Laid-Open No. 63-214726 discloses a technique in which an image is photographed at a lens position where infinity is an optimum focus position regardless of a distance measurement signal. A camera having means for setting a lens is disclosed. In this camera, an operation member for operating a means for setting the photographing lens at such a position is also provided.

[Problems to be solved by the invention]

By the way, in a camera which is a self-focusing camera as described above and which can be set by a manual operation only for an operation of focusing on an object at infinity, the photographer performs such a manual operation and forcibly performs the operation. Despite the setting to focus on infinity, the shutter release is activated by the drive of the taking lens responding to the measurement result of the distance measuring device, although the camera is not actually focused on infinity. There is a risk that so-called "out of focus" or "out of focus" photos will be created. The present invention has been conceived to solve the technical problems in the autofocus camera as described above, and its purpose is to
An auto-focus camera capable of shooting at infinity even if it has an active-type distance measuring mechanism, and when measuring at infinity, the measurement result of the distance measuring mechanism indicates that the subject at infinity is in focus at a predetermined distance. It is an object of the present invention to provide an automatic focusing camera that does not erroneously photograph a subject having a shorter subject distance.

[Means for Solving the Problems]

The autofocus camera according to the present invention is provided with the following configuration in order to solve the technical problems as described above and achieve the object. That is, active distance measuring means for measuring the distance to the subject, lens driving means for automatically adjusting and moving the position of the taking lens to focus on the distance measured by the distance measuring means, manually operated, at least An infinity setting device that operates to focus an imaging optical system including the imaging lens at an infinity distance. Reference distance setting means for setting a subject distance serving as a reference for determining whether or not the photographing lens being set is in a position for focusing a photographing optical system including the photographing lens at infinity; The distance measured by the means
Comparing means for determining whether or not the distance is greater than or equal to the distance set by the reference distance setting means in accordance with the operation of the infinity setting means; and A warning is made inoperative by determining that the distance is greater than or less than the distance, or a shutter release is permitted, and a warning is issued by determining that the measured distance is less than or less than the set distance, or a shutter is released. Warning means or release prohibiting means for prohibiting release is provided. The infinity setting means is combined with the photographing lens set at the position corresponding to the farthest object distance at the position of the photographing lens corresponding to the measurement result of the distance measuring means to focus on infinity. It may be constituted by a lens having a negative power, which forms a photographic optical system and goes in and out of the photographic lens. The reference distance setting means interlocks with the operation of the infinity setting means and changes the distance value of a switching point for determining the farthest object distance and the next distant object distance of the distance measuring means to the reference value. It may be configured as follows. The comparison reference distance setting means may be a wedge lens which enters and exits in front of the light receiving section of the distance measuring means in conjunction with the operation of the infinity setting means. Further, the lens having the negative power may be a lens barrier of the photographing lens.

[Action]

In the automatic focusing camera according to the present invention, the active distance measuring means always measures the subject distance by an operation immediately before the shutter release, and the lens driving means moves the taking lens to a predetermined position in accordance with the measurement result. set. In normal shooting, the position of the taking lens, which is determined according to the result measured by the active type distance measuring means, does not focus on the subject distance at infinity. It is possible to focus on infinity by an optical system synthesized by the means and the taking lens. However, in the case of shooting at infinity setting, if the shooting lens combined with the infinity setting means is not at an appropriate position, focusing on infinity will not be possible, so the position of the shooting lens determined by the measurement result of the distance measuring means Is appropriate, it is determined whether to give a warning, or to permit or restrict shutter release. Whether or not the position of the taking lens in the case of infinity setting shooting is appropriate can be determined by comparing the subject distance actually measured by the distance measuring means with a predetermined reference subject distance. It is set by the reference distance setting means. The set reference distance and the actual measurement distance of the distance measuring means are compared by the comparing means, and based on the result of the comparison, it is determined whether to issue a warning or to permit or restrict the shutter release. The set reference distance is a distance to a position in front of the depth of field that is in focus within the range of the permissible circle of confusion in infinity setting shooting, and when this set reference distance is equal to the distance to the front position. If the measured distance is longer than the set reference distance, the warning is deactivated or the shutter release is permitted, and if the measured distance is shorter than the set distance, a warning is issued, or the release prohibiting means restricts the shutter release. When a lens having negative power is used as the infinity setting means, it is possible to switch between normal shooting and infinity setting shooting by moving the lens in and out of the taking lens.
The taking optical system consisting of the taking lens located at the position corresponding to the longest subject distance that can correspond to the measurement result of the distance measuring means and the lens with negative power inserted in front of it is The camera is in focus. When the lens having negative power is removed from the front of the taking lens, normal shooting can be performed. In the active type distance measuring means, a plurality of light receiving elements are arranged in the light receiving section, and the subject distance is measured according to which light receiving element reflected from the subject to be measured and returned is incident on the light receiving element Therefore, there is a distance value at which the measured object distance switches between the light receiving element corresponding to the farthest object distance and the light receiving element corresponding to the next farthest object distance. The distance value becomes a switching point of the setting position of the photographing lens, and the switching point differs between the normal photographing and the infinity setting photographing. The reference distance setting means changes the distance value serving as the switching point from the setting for performing distance measurement in normal shooting to the setting for performing distance measurement in infinity setting shooting. When a wedge lens is used as the comparison reference distance setting means, the wedge lens is moved in and out of the light receiving section of the distance measuring means in conjunction with the infinity setting means, so that the infinity setting means is activated and the normal shooting is performed at infinity. Automatically switches to setting shooting. The wedge lens adjusts the refractive index and the relative positional relationship with respect to the light receiving unit, so that the distance measuring unit can adjust the distance between the light receiving element corresponding to the farthest object distance and the light receiving element corresponding to the next distant object distance. The distance value serving as the switching point can be changed to a desired value. When a lens having a negative power is used as the infinity setting means, by using this as a lens barrier, it is possible to suppress an increase in the number of parts and an increase in the size of the camera itself.

【Example】

FIG. 1 is an external view showing an embodiment of an automatic focusing camera according to the present invention. In the figure, 1 is a release button, 2 is a finder, 3 is a light emitting unit of a distance measuring device, 4 is a light receiving unit, and 5 is a strobe light emitting unit. The release button 1 is a two-stage push-in type. The details will be described later, but the distance measurement and side light are performed by the first-stage push operation, and the exposure adjustment and the focus adjustment are performed by the second-stage push operation. The shutter release is performed. On the front surface of the camera body 6, a window 7 protrudes forward at a position corresponding to the photographing lens (not shown).
A lens barrier 8 that slides to open and close the window 7 is housed therein.
The conventional lens barrier closes the window in front of the photographing lens during non-photographing to protect the photographing lens, and opens the window during photographing to enable photographing. However, the lens barrier 8 of this embodiment has a negative power. A photographing lens 9 which is set at a far-side in-focus position of an automatic focusing mechanism.
The imaging optical system combined with the converter lens 8 having the negative power is configured to focus on an infinity position, and further has an infinity setting function in addition to the conventional lens barrier function. Have. Note that a solenoid 11 is used for the photographing lens drive mechanism 10 of the automatic focusing mechanism in the camera of the present embodiment, and the photographing lens 9 is set to the far side in accordance with the ON state and the OFF state of energization of the solenoid 11. It is set at two positions, a focus position and a near focus position.
The opening / closing operation of the lens barrier 8 is linked with the operation of an on / off switch for normal shooting and an infinity shooting setting switch, and an operation knob 12 is disposed below the protruding portion. FIG. 2 is an explanatory diagram of a schematic configuration including a lens barrier operation section and a lens extension mechanism of the camera shown in FIG. 1 as viewed from above the camera body, and including their electric systems. FIG. 3 is an explanatory diagram showing the configuration of the operation unit of the lens barrier in FIG. 2 as viewed from the front side of the camera body. Each of these figures shows a state in which the barrier 8 is closed and the main power supply 13 is turned off. The lens barrier 8 is
It is linked to the main power supply 13 of the camera main switch SO ₁ which is turned on and off by operation of the operation knob 12. When the main switch SO ₁ is in the on position, the barrier 8 opens the main power supply 13 is turned on, can be performed normal automatic exposure and automatic focus photographing. The switches S ₁ and S _{2 in} FIG.
Is turned on in conjunction with the first and second presses of the release button 1. These switches S ₁ and
For S _2, in the second drawing context of the automatic exposure mechanism are shown only the automatic focusing mechanism not shown, will be described only with respect to its automatic focusing mechanism, the the switch S ₁ is to perform distance measurement the AF memory 14 for storing AF data is activated, the switch S ₂ actuates the auto-focus mechanism driving circuit 15 based on the data of the AF memory 14. With the operation knob 12, only the knob 12 can be further moved while the lens barrier 8 is closed, and the infinity setting switch SO
₂ can be turned on. This infinity setting switch S
O ₂ turns on the main power supply 13 while keeping the lens barrier 8 closed, activates the distance determination circuit 17, and activates the release lock circuit 16 according to the content of the determination. Hereinafter, detailed description will be given of the operation knob 12 and the main switch SO ₁ and infinity setting switch SO _2. The operation knob 12 is fixed to a bar member 21 that can slide left and right in the horizontal direction below the lens barrier 8, and when the operation knob 12 is moved left and right, the bar member 21 slides in the horizontal direction. A pin 23 projects from the center of the bar member 21, and a long hole 24 that fits into the pin 23 is formed in the lever member 22. The bar member 21 and the lever member 22 are connected by the engagement between the pin 23 and the elongated hole 24. The lower end of the lever member 22 is rotatably supported at the lower end thereof, has the elongated hole 24 substantially at the center, and the upper end is engaged with one end of the lens barrier 8. The lever member 22 is urged by a spring 25 so that the lever member 22 is stabilized at both folded positions of the swing motion. Therefore, by operating the operation knob 12 and sliding the bar member 21, the opening and closing operation of the window of the lens barrier 8 can be obtained together with the swing of the lever member 22.
Further, the elongated hole 24 of the lever member 22 is bent halfway, and the pin 23 of the bar member 21 is located at the bent portion of the elongated hole 24 at the closed position of the barrier 8 as shown in FIG. Allows only the bar member 21 to further slide to the left in the figure without swinging the lever member 22. When the bar member 21 slides rightward from the state of FIG. 3, the lever member 22 rotates clockwise in the figure to move the lens barrier 8 to the open position. The bar member 21 is formed with an arm portion 26 extending downward in a direction orthogonal to the bar member 21, and a switch contact 27 is attached to a tip of the arm portion 26. The bar member 21 is
The switch contact piece 27 is turned on the position of the main switch SO _1,
Off position and is configured to be stopped at three places on the position of the infinity setting switch SO _2. For on-position and off position of the main switch SO _1, the bar member at each position with the notch 28, 29 of the two locations formed at one end of the bar member 21, the click pin 30 in cooperation with engagement thereto Stabilize 21. Infinite The ON position of the distance setting switch SO _2, bar member 21 against the urging force of the auxiliary spring 31 shown in FIG. 3 from the OFF position of the main switch SO ₁
Is further slid to the left side of the drawing, at which time the click pin 30 is attached to the protrusion 32 formed at the right end of the bar member 21.
The bar member 21 can be stopped at that position by the engagement between the projection 32 and the click pin 30. In the camera of the present embodiment, the position of the photographing lens 9 set corresponding to the ON / OFF of the solenoid 11 is substantially the same as that of the subject existing in the short distance side zone within the range of an allowable circle of confusion. The first position is a second position where the focus is approximately within the range of the permissible circle of confusion with respect to the subject present in the far side zone, and the first position is a subject located at a distance of 2 m from the film surface. The second position is a position where the subject located at a distance of 4 m is in focus. The depth of field of the taking lens 9 in the first position and the second position is determined by calculating the forward scene distance d ₁ and rear depth of field distance d ₂ by the following equation. In these equations (1) and (2), the focal length f of the photographing lens 9 is 28 mm, the distance x from the film surface to the front principal point of the lens 9 is 28 mm, the F number of the lens 9 is 4.5, and the diameter of the permissible circle of confusion. 1δ is set to 0.03 mm. When the taking lens 9 is at the first position, the distance L from the film surface to the focused object is 2 m, and when the taking lens 9 is at the second position, the distance L is 4 m. When these numerical values are substituted into the above equations to calculate the depth of field in each case, the depth of field when the taking lens 9 is at the first position is about 1.5 to 3.0 m.
(Hereinafter, referred to as a near zone), and the depth of field at the second position is approximately 2.4 to 12.6 m (hereinafter, referred to as a far zone). Therefore, the switching between the first position and the second position of the photographing lens 9 is selected at approximately the center value of the zone where the near zone and the far zone overlap, and in this embodiment, about 2.
Set to 7m. In other words, as a result of distance measurement, the subject
When the lens is in the vicinity of 2.7 m, regardless of the position of the photographing lens 9, the focus is approximately within the range of the permissible circle of confusion, and when the lens is closer than that, the photographing lens 9 is set to the first position. If the position is farther than that, the second position is set. The distance x is strictly different between the first position and the second position, but the difference is negligible. In addition, the position ahead of the depth of field when the converter lens of the lens barrier 8 is inserted and focused on infinity is approximately 5.8 m in calculation, assuming that the diameter of the permissible circle of confusion is 1δ = 0.03 mm. Therefore, the above-described distance determination circuit 17
If it is determined from the result of the distance measurement that the subject is closer than about 5.8 m, the release lock circuit 16 is operated. By the way, when the diameter of the permissible circle of confusion is 1.5δ = 0.045mm,
The position in front of the depth of field is about 3.9m and the diameter of the permissible circle of confusion is 2δ.
When the distance is 0.06 mm, the distance is about 2.9 m. However, in the above equation (2), d ₂ = ∞ and the photographing lens 9 at infinity at the second position.
If the diameter of the permissible circle of confusion at that time is δ = 0.0439 mm by solving the equation in which the denominator of equation (2) is 0, the diameter of the circle of confusion can be obtained without using a converter lens. The amount of “blur” becomes smaller when the image is taken with the taking lens 9 set at the second position. In addition, as shown in FIG.
In conjunction with this, an auxiliary optical system including a wedge lens 18 which enters and exits in front of the light receiving section 4 of the distance measuring device is connected. The wedge lens 18 is located in front of the light receiving unit 4 at the same time that the lens barrier 8 is located in front of the taking lens 9. Main switch SO ₁ is when in the on position, the wedge lens 18 and the lens barrier 8 are both in the respective retracted position, auto-focus shooting is performed based on the normal distance measurement. When the infinity setting switch SO ₂ is turned on, the wedge lens 18 is located in front of the light receiving unit 4, and as shown in FIG. Refract to the near distance side. In normal shooting without the wedge lens 18 in front of the light receiving unit 4,
The reflected light from the subject in the far zone and the reflected light from the subject in the near zone are incident on separate light receiving elements, and the boundary point is set to 2.7 m. In the infinity photography in which is inserted, the refractive index and posture of the wedge lens 18 are set so that the boundary point is 5.8 m. That is, in the case of shooting at infinity, the photographic lens 9 is set at the second position for a subject at a distance of 5.8 m or more, and is set at the first position for a subject closer than 5.8 m.
Therefore, if the shutter is released when the subject is closer than 5.8 m in spite of the infinity setting shooting, the photograph becomes so-called "out of focus".
The warning circuit 35 operates to give a warning, and the release lock circuit 16 operates to prohibit shutter release. Next, the operation of the camera configured as described above will be described. Switch S ₁ is turned on by pushing the first stage of the release button 1, switch S ₂ is turned on by the second stage push. Little even, timer circuit after a predetermined (not shown) is operated time switch S ₂ is turned on after the switch S ₁ is turned on is the time difference between the pressing of the first stage and the pushing of the 2-stage It is configured so that First, in the case of a normal photographing lens barrier 8 is opened, the main switch SO ₁ is turned on position, the main power supply 13 is turned on by operating the operation knob 12. Switch S ₁ is turned on when the photographer presses the first stage of the release button 1, the AF data and the AE data is stored in the memory, is further output storage completion signal from the memory is ranging and photometry performed . Or more second-stage push in addition to pushing the first stage is being performed, or the switch S ₂ is turned on by continuing the second stage push made. When the switch S ₂ is turned on, to set the photographing lens 9 in the correct position based on the AF data stored in the memory, it performs correct exposure on the basis of the AE data. When the exposure is completed, the photographing lens 9 returns to the initial position, the film (not shown) is wound up by a predetermined amount for one frame, and a standby state for the next photographing is set. Next, a case will be described in which infinity setting photography is performed in which the object at infinity is focused with the lens barrier 8 closed. First, when set to infinite set position photographer operates the operation knob 12 manually, infinity setting switch SO ₂ is turned on. When the switch S ₁ is turned on in this state, as in the case of the ordinary photographing AF data and AE
The data is stored in the memory, and a storage completion signal is output from the memory. Further switch S ₂ is turned on, whether AF data stored in the memory is subject distance to be photographed at infinity, that is, whether farther than 5.8m is discriminated in perspective discriminating circuit 17 , the on-state switch S ₂ is accepted if the subject is sufficiently farther. Conversely, if the AF data indicates a short distance than 5.8 m even though the infinity setting switch SO ₂ is on, a warning circuit
35 is activated to give a warning and release lock circuit
16 is activated and the ON state of switch S ₂ is not accepted,
Shutter release is prohibited. Note that the warning circuit in the above embodiment may be a warning display using an LED, an LCD, or the like,
It may be a warning buzzer. In the above embodiment, both the release prohibition and the warning are performed, but it goes without saying that either one may be performed.

【The invention's effect】

As apparent from the above description, according to the present invention, the following excellent effects are exhibited. In other words, even with a lens drive method using a solenoid with an active distance measuring mechanism, it is possible to shoot with focus accurately at infinity, and even if the infinity setting is operated, If the subject distance is short, a warning is issued or the shutter release is restricted, so that a shooting mistake in shooting at infinity setting can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is an external view showing an embodiment of an autofocus camera according to the present invention, and FIG. 2 is a view showing a lens barrier operation section and a lens extension mechanism of the camera of FIG. 1 viewed from above a camera body. It is explanatory drawing of the schematic structure also including the electric system. FIG. 3 is an explanatory view showing the configuration of the operation unit of the lens barrier shown in FIG. 2 as viewed from the front side of the camera body. FIG. FIG. 4 is a diagram illustrating an optical path of distance measuring light when the distance measurement is performed. Reference numeral 3 denotes a light projecting section as a distance measuring means, 4 ... a light receiving section as a distance measuring means, 8 ... a lens having a negative power which is also used as a lens barrier as an infinity setting means, 9 ... a photographing lens. .., 10... A lens driving mechanism as lens driving means, 16... A release lock circuit as release inhibiting means, 17... A distance discrimination circuit as comparison means, 18... A wedge lens as reference distance setting means, 35. ... Warning circuit as warning means

Claims (6)

(57) [Claims] 1. An active distance measuring means (3, 4) for measuring a distance to a subject, and a position of a photographing lens (9) for focusing on the distance measured by the distance measuring means (3, 4). Lens driving means (10) for automatically adjusting and moving the lens, and at least the photographing lens (9) operated manually.
An infinity setting means (8) operable to focus an imaging optical system (8, 9) including infinity at an infinity distance, wherein the distance measurement means (3, The shooting lens (9) set according to the measurement result of 4)
Reference distance setting means (18) for setting a subject distance serving as a reference for determining whether or not the photographing optical system (8, 9) including the photographing lens (9) is at a position for focusing on infinity; The infinity setting means (8) determines whether or not the distance measured by the distance measuring means (3, 4) is greater than or less than the distance set by the reference distance setting means (18). Comparing means (17) for discriminating in accordance with the operation of (1), and the comparing means (17) discriminates that the measured distance is longer than or longer than the set distance, thereby allowing a shutter release. An autofocus camera comprising: release prohibiting means (16) for prohibiting a shutter release by determining that the distance is equal to or shorter than the set distance. 2. An active type distance measuring means (3, 4) for measuring a distance to a subject, and a position of a photographing lens (9) for focusing on the distance measured by said distance measuring means (3, 4). Lens driving means (10) for automatically adjusting and moving the lens, and at least the photographing lens (9) operated manually.
An infinity setting means (8) operable to focus an imaging optical system (8, 9) including infinity at an infinity distance, wherein the distance measurement means (3, The shooting lens (9) set according to the measurement result of 4)
Reference distance setting means (18) for setting a subject distance serving as a reference for determining whether or not the photographing optical system (8, 9) including the photographing lens (9) is at a position for focusing on infinity; The infinity setting means (8) determines whether or not the distance measured by the distance measuring means (3, 4) is greater than or less than the distance set by the reference distance setting means (18). A comparing means (17) for discriminating in accordance with the operation of (1), and a warning means (35) for giving a short distance warning by the comparing means (17) discriminating that the measured distance is equal to or less than the set distance. An autofocus camera, comprising: 3. The infinity setting means, wherein the distance measuring means (3,
The photographing optics which is synthesized with the photographing lens (9) set at the position corresponding to the farthest object distance at the position of the photographing lens (9) corresponding to the measurement result of 4) and focused on infinity 3. Autofocus according to claim 1, comprising a system (8, 9) and a lens (8) having a negative power entering and exiting the taking lens (9). camera. 4. The reference distance setting means (18) operates in conjunction with the operation of the infinity setting means (8) to operate the distance measuring means (3, 3).
4. The auto-focus camera according to claim 1, wherein a distance value of a switching point for determining the farthest object distance and the next farther object distance is changed to the reference value. 5. The comparison reference distance setting means is a wedge lens (18) which goes in and out of a light receiving section (4) of the distance measuring means in conjunction with the operation of the infinity setting means (8). The autofocus camera according to claim 4, wherein: 6. The lens (8) having a negative power,
4. The auto-focus camera according to claim 3, wherein the camera is a lens barrier of the taking lens.