JP2722435B2 - camera - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera that selectively has an autofocus function and a power focus function and has a zoom function. 2. Description of the Related Art A camera with a zoom function in which a zoom lens and a focus lens can be moved independently of each other is disclosed in, for example,
As described in JP-A-264307, it is also known that in this conventional example, the position of the image plane changes due to the movement of the zoom lens. However, nothing is said about the relationship between zooming and power focus. On the other hand, Japanese Patent Application Laid-Open No. 59-12983 describes that an auto focus and a power focus function are provided, and that these functions can be selectively switched. SUMMARY OF THE INVENTION Problems to be Solved by the Invention A compensator composed of a focus lens group driven independently of a focal length variable variator composed of a variable magnification lens group automatically corrects an image plane position based on focus detection information. The camera has the advantage of contributing to a reduction in size and weight because there is no need for a connecting cam barrel for image plane position correction, but the automatic correction based on the focus detection information is not performed at the time of power focus, and from the outside. Since the compensator is arbitrarily moved by the operation of, if the variator is moved for zooming and the position of the image plane is displaced, the correction cannot be performed and a state in which the image is out of focus may occur. Therefore, an object of the present invention is to provide a camera that eliminates such an undesirable state. Means for Solving the Problems In order to solve the above problems, the camera of the present invention includes a variator for zoom comprising a variable power lens group and an automatic focus adjustment for compensating for an image plane displacement at the time of zooming. A compensator functioning to perform, and a first driving the variator
A driving means, a second driving means for driving the compensator, a selection means for selectively selecting and setting an auto focus mode and a power focus mode, a zoom operation member for operating the first driving means, Apart from a zoom operation member, a power focus operation member operable independently of the zoom operation member for operating the second driving means in the power focus mode, When is selected, the zoom operation by the zoom operation member is prohibited. In the auto focus mode, the compensator moves based on the output of the focus detection means, and the auto focus operation is performed. At this time, if the variator is moved by operating the zoom operation member (zooming is performed), the positional relationship between the variator and the compensator changes, and the image plane position also changes, so that the subject light given to the focus detection means also changes. Accordingly, the focus detection output also changes. With this output, the compensator is further moved, and the change in the image plane position is corrected. However, in the state where the power focus mode is selected by the selection unit, even if the zoom operation member is operated, the first driving unit and the variator do not operate at all. Therefore, in the power focus mode, the second operation by the power focus operation member as the external operation means is performed.
Only the movement of the compensator via the drive means takes place. FIG. 1 is a sectional view of a main part of a video camera embodying the present invention. In FIG. 1, a photographic lens (1) includes a front lens group (3) and a variator in a cylindrical fixed cylinder (2) sequentially from the front. (4) It has a compensator (5). The front lens group (3) is fixed, and the variator (4) and the compensator (5) are movably provided as described later. The variator (4) is composed of a variable power lens group, and changes the focal length by moving the variator. Compensator (5)
Is composed of a focus lens group and operates for focus adjustment. However, at the time of zooming, it operates so as to correct the shift of the image plane position due to the movement of the variator (4). As this compensator, there has been a compensator which is configured to move by a cam mechanism linked to a variator, but in the present embodiment, a focus detection device for auto focus (hereinafter referred to as "AF") will be described later. Or is electrically driven by the operation of the power focus operation means, and is driven by drive means independent of the variator (4). Although not directly related to the present invention, accessories for zooming such as a teleconverter and a wide converter can be attached to the front end of the taking lens (1).
Detection means (6) for determining the type of the accessory is provided. The fixed cylinder (2) is also equipped with a guide rod (7) and first and second lead screws (8) (9) inside. The guide rod (7) is arranged near the inner surface of the fixed cylinder (2) along the longitudinal direction of the fixed cylinder (2), and both ends thereof are fixed. In the same manner, the first and second lead screws (8) and (9) are shown on the same straight line. (15) makes it freely rotatable. The variator (4) has a concave groove (4a) in a part thereof. The variator (4) is slidably and loosely fitted to the guide rod (7) through the concave groove, and is directed along the optical axis (10). When moving in the left-right direction (in the left-right direction of the drawing), it moves while being guided by the guide rod (7). The variator (4) has a screw portion (4b) including a screw groove on the side opposite to the side where the concave groove is provided, and the first lead screw (4) is inserted through the screw portion (4b). 8). Further, a sliding brush (11) is mounted on the variator (4).
1) slides on the contact piece of the zoom encoder (12) attached to the inner surface of the fixed cylinder (2). Similarly, the compensator (5) has a concave groove, and is slidably and loosely fitted on the guide rod (7) through the concave groove, and the other end side is a threaded portion (5b).
Screwed into the second lead screw (9). The first lead screw (8) for driving the variator is provided with a gear mechanism (1).
It is coupled to the zoom motor (14) via 3) and is rotated by the rotation of the zoom motor (14). A second lead screw (9) for driving the compensator is also connected to the AF motor (15) via a gear mechanism (not shown). The photographing lens (1) is provided with a near limit switch (16) and a far limit switch (17) for limiting the moving range of the compensator (5), as shown in the figure. The camera body (18) has a ranging prism (19) and an aperture (2
0), master lens group (21), low-pass filter (2
2) An imaging optical system consisting of an imaging CCD (23) and an aperture control meter (24), a total reflection mirror (26) mounted on a holding frame window (25), a ranging lens (27), Distance module (2
8) has a focus detection optical system and the like. The distance measuring lens (27) is fixed to the holding frame (30) by screws (29). Similarly, the distance measuring module (28) is also fixed to the screws (31) and (32).
Is fixed to the holding frame (30). Aperture (20),
Master lens group (21) and low-pass filter (22)
Is fixed in a holding cylinder (33) arranged along the optical axis (10) in the camera body (18). The CCD (23) is arranged at the rear end of the holding cylinder via a protective glass (34). The light from the subject is the front lens group (3), the variator (4),
Most of the light passes through the compensator (5), travels straight through the distance measuring prism (19), and is guided to the imaging CCD (23) through the master lens group (21) and the low-pass filter (22). On the other hand, part of the subject light that is bent at right angles by the distance measuring prism (19) passes through a total reflection mirror (26) and a distance measuring lens (27), and a distance measuring module (2
8) to reach. FIG. 2 shows a system controller (35) comprising a microcomputer housed in the camera body (18).
And a drive control configuration of the variator (4) and the compensator (5) with a focus on FIG. Here, (44) is a selection switch for selectively switching the focus adjustment between AF (autofocus) mode and manual mode (power focus mode). The system controller (3
5) control. Reference numeral (45) denotes a power focus operation switch, which includes a near switch (45A) for moving the compensator (5) to the near side and a far switch (45B) for moving the compensator (5) to the far side. Power focus is a focus adjustment method used when AF is impossible (that is, when the contrast of the subject is too low or when the subject is too dark), or when a desired focus is desired. The compensator is driven via electric means to adjust the focus. Reference numeral (36) denotes a zoom operation switch, which includes a tele switch (36A) for performing a zoom operation in a tele direction and a wide switch (36) for performing a zoom operation in a wide direction.
B) is shown. The system controller (35) is configured not to receive a zoom operation when the power focus mode is selected by the selection switch (44). This configuration can be easily realized by a logic circuit that forms a logic of a signal from the zoom operation switch (36) and a signal from the selection switch (44). As shown in FIG. 3, the distance measuring module (28) has a condenser lens (40) for focusing light passing through different pupils of a distance measuring lens (27) and an aperture mask (4).
1), consists of a re-imaging lens (42) and a CCD line sensor (43). Note that (39) indicates an imaging plane equivalent position. In FIG. 3, subject light entering the distance measuring system forms two subject images on a CCD line sensor (43) by a condenser lens (40), an aperture mask (41), and a re-imaging lens (42). The system controller (35) detects the amount and direction of deviation from the in-focus position by detecting the relative positional relationship between the two images, and drives the compensator (5) to reach the in-focus state. Close. Incidentally, such focus detection is disclosed in Japanese Patent Application Laid-Open No. 60-4914, and will not be described in detail here. Next, the operation of the present embodiment will be described. The system controller (35) first determines whether the selection switch (44) is in the AF mode or the power focus mode. In the AF mode, the focus detection calculation is performed based on the detection signal from the distance measurement module (28), and the AF motor drive circuit (38) drives the AF motor (15) using the signal of the calculation result, and the compensator ( 5) is moved to adjust the focus of the subject. At this time, when the zoom operation switch (36) is operated, the zoom motor drive circuit (3) is transmitted via the system controller (35).
7) and the zoom motor (14) are also driven, and the variator (4) moves. When the variator (4) moves, the positional relationship among the front lens group (3), the variator (4), and the compensator (5) changes, and the position of the image plane changes, which is given to the distance measuring module (28). The subject light also changes, and the focus detection calculation result also changes accordingly. Further fine-tuning of the compensator (5) is performed based on the calculation result,
A change in the image plane position due to the movement of the variator (4) is always corrected, and a focused image is obtained. In the AF mode state, the input from the power focus operation switch (45) is prohibited by the system controller (35). This is because the AF motor (15) moves and focuses on the basis of the focus detection result, so inputting a signal from the outside that causes a different operation from this movement may cause malfunction. is there. Next, an operation when the selection switch (44) is set to the power focus mode will be described. In the power focus mode, the system controller (35) prohibits input from the distance measurement module (28), prohibits AF operation, and prohibits input from the zoom operation switch (44) to prohibit zooming operation. When the near switch (45A) or the far switch (45B) of the power focus operation switch (45) is turned on in this state, the system controller (35) responds to this and the AF motor drive circuit (38)
Drives the AF motor (15) through the compensator (5)
To the near side or far side. In the above, the present invention has been described along with the embodiments,
The present invention is not limited to this embodiment, and can be freely changed and modified without departing from the spirit of the invention described in the claims. For example, a mode in which the front lens group (3) is operated as a compensator is also possible. In this case, the AF motor (15) may be changed so as to be connected to the front lens group (3). According to the present invention, when the focus compensator driven independently of the zooming variator is driven in the power focus mode, the zoom operation is prohibited, so that the image plane position cannot be compensated. There is no operation method, and an image in which the focus state is always optimized can be obtained. In addition, when zooming is performed, autofocus is performed, and a focus shift due to zooming can be automatically corrected.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a main part of a camera embodying the present invention,
FIG. 2 is a block circuit diagram, and FIG. 3 is a detailed diagram of a part of the configuration. (4)… variator, (5)… compensator,
(14) Zoom motor, (15) AF motor, (28)
… Distance measuring module, (35)… System controller, (36)… Zoom operation switch, (37)… Zoom motor drive circuit, (38)… AF motor drive circuit, (44)… Selection switch , (45) ... Power focus operation switch.

   ────────────────────────────────────────────────── ─── Continuation of front page        Panel     Referee Katsunori Ishii     Judge Akira Watanuki     Judge Yoshiyuki Kawakami                (56) References JP-A-62-19827 (JP, A)

Claims (1)

(57) [Claims] A variator for zoom comprising a variable power lens group; a compensator functioning to perform automatic focus adjustment to compensate for an image plane displacement during zooming; first driving means for driving the variator; and driving the compensator A second driving unit that performs an autofocus mode and a power focusing mode; a zoom operating member that operates the first driving unit; A power focus operation member operable independently of the zoom operation member for operating the second drive means in a focus mode, wherein the zoom operation is performed when the selection means selects the power focus mode A camera characterized in that a zoom operation by a member is prohibited.