JPS63195630A - Camera - Google Patents

Abstract

PURPOSE:To obtain an image whose in-focus state is invariably optimized by inhibiting a zooming operation when a compensator for focusing which is driven independently of a variator for zooming is driven in power focus mode. CONSTITUTION:In the power focus mode set with a selection switch 44, a system controller 35 inhibits an input from a distance measurement module 28, inhibits an automatic focusing (AF) operation, and also inhibits an input from a zoom operation switch 44 to inhibit the zooming operation, as well. When the close- distance 45A or far-distance switch 45B of a power focus operation switch 35 is turned on in this state, the system controller 35 senses it and drives an AF motor 15 through an AF motor driving circuit 38 to move a compensator to a close-distance or long-distance side. Consequently, a shift in image forma tion plane position is corrected at all times to obtain an in-focus image.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a camera that selectively has an autofocus function and a power focus function, as well as a zoom function.

Conventional technology A camera with a zoom function in which a zoom lens and a focus lens can be moved independently of each other is disclosed, for example, in Japanese Patent Laid-Open No. 61
This is known as described in Japanese Patent No. 264307, and this conventional example also describes that the position of the imaging plane changes as the zoom lens moves. However, nothing is mentioned about the relationship between zooming and power focus. On the other hand, JP-A-59-1
Publication No. 2983 describes that autofocus and power focus functions are provided and that these functions can be selectively switched.

Problems to be Solved by the Invention A compensator consisting of a focus lens group that is driven independently of a variator for focal length variation consisting of a variable magnification lens group automatically corrects the image plane position based on focus detection information. The camera has the advantage of contributing to reduction in size and weight because it does not require a connected cam tube for image plane position correction, but during power focusing, the automatic correction based on the focus detection information is not performed, Since the compensator is arbitrarily moved by an operation from the camera, if the variator moves due to zooming and the position of the imaging plane is displaced, it cannot be corrected and the situation may be out of focus.

Therefore, an object of the present invention is to provide a camera that eliminates such undesirable conditions.

Means for Solving the Problems A zoom variator comprising a variable magnification lens group, a compensator functioning as a focal point adjustment device for compensating for displacement of an imaging plane, a first driving means for driving the variator, and a first driving means for driving the variator; a second drive means for driving the compensator; a selection means for selectively setting the autofocus mode and the power focus mode; a zoom operation means for operating the first drive means; In a camera having a focus detection means for driving a second drive means and a power focus operation means for operating the second drive means in a power focus mode, a zoom operation by the zoom operation means is prohibited in the power focus mode. The configuration is as follows.

In the working autofocus mode, the compensator moves based on the output of the focus detection means, and autofocus operation is performed. At this time, when the zoom operation means is operated to move the variator (zooming), the positional relationship between the variator and the compensator changes, and the imaging plane position also changes, so the subject light given to the focus detection means also changes. , the focus detection output also changes accordingly. This output causes the compensator to further move, thereby correcting the change in the position of the imaging plane. However, when the power focus mode is selected by the selection means, the first drive means and the variator do not operate even if the zoom operation means is operated. The only movement of the compensator is via the second drive means.

Embodiment In FIG. 1, which is a cross-sectional view of the main parts of a video camera embodying the present invention, the projection lens (1) is a cylindrical fixed tube (2).
) in order from the front: front lens group (3), variator (4)
, and a compensator (5).

The front lens group (3) is fixed, and the variator (4) and compensator (5) are movably arranged as will be described later. The variator (4) consists of a variable magnification lens group, and its focal length is changed by its movement.

The compensator (5) consists of a focus lens group,
It functions for focus adjustment, but during zooming, it functions to correct the shift in the imaging plane position due to the movement of the variator (4). The second type of compensator has conventionally been configured to be moved by a cam mechanism interlocking with a variator, but in this embodiment, as will be described later, a focus detection device for autofocus (hereinafter referred to as rAFJ) is used. It is configured to be electrically driven by an output or by operation of a power focus operating means, and is driven by a driving means independent of the variator (4). Although not directly related to the present invention, the front end of the photographic lens (1) can be fitted with accessories for variable magnification, such as a teleconverter or wide converter. A detection means (6) is provided. The fixed cylinder (2) has a guide rod (7) and first and second lead screws (8) (
9) is also equipped. The guide rod (7) is a fixed cylinder (2)
It is arranged along the longitudinal direction of the fixed cylinder (2) near the inner surface of the fixed cylinder (2), and its both ends are fixed. 1st and 2nd in similar form
1J-Done screws (8) and (9) are shown on the same straight line, but in reality they are placed at different positions in the direction perpendicular to the page, and are rotatable by motors (14) and (15), which will be described later. It has become.

The variator (4) has a groove (4a) in a part thereof, and is slidably fitted loosely into the guide rod (7) through the groove, so that the variator (4) is fitted in the direction along the optical axis (10). (Left and right direction of drawing)
When moving to , it moves while being guided by a guide rod (7). The variator (4) has a threaded part (4b) including a threaded groove on the side opposite to the side where the groove is provided, and the first lead screw (4b) is inserted through this threaded part (4b). 8) is screwed together.

Furthermore, a sliding brush (11) is attached to the variator (4), and this sliding brush (11) slides on the contact piece of the zoom encoder (12) attached to the inner surface of the fixed cylinder (2). do. The compensator (5) similarly has a groove, and is slidably and loosely fitted into the guide rod (7) through the groove, and the other end is connected to the second lead screw (5b) by a threaded portion (5b). 9). The first lead oscillator (8) for driving the variator is connected to a zoom motor (14) via a gear mechanism (13) and 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 photographic lens (1) is equipped with a near limit switch (16) and a far limit switch (16) that limit the movement range of the compensator (5).
7) are provided as shown.

The camera body (18) includes a distance measuring prism (19), an aperture (
20), an imaging optical system consisting of a master lens group (21), a low-pass filter (22), a CCD for imaging (23), an aperture control meter (24), and a total internal reflection system mounted on the holding frame window (25). Mirror (26), distance measuring lens (27)
, a focus detection optical system consisting of a distance measuring module (28), etc. The distance measuring lens (27) is fixed to the holding frame (30) by a dowel (29), and similarly the distance measuring module (28) is also fixed to the holding frame (30) by screws (31) (32).
30). The diaphragm (20), the master lens group (21), and the low-pass filter (22) are fixed in a holding tube (33) arranged along the optical axis (10) within the camera body (18).

COD (23) has a protective glass (
34).

The light from the subject passes through the front lens group (3), variator (4), and compensator (5), and most of the light travels straight through the distance-measuring prism (19), and then passes through the master lens group (21),
C0D (23) for imaging passes through a low-pass filter (22)
be led to. On the other hand, a part of the subject light bent at right angles by the ranging prism (19) passes through the total reflection mirror (26) and the ranging lens (27), and reaches the ranging module (28) containing a CCD line sensor, etc. do.

FIG. 2 shows a system controller (35) consisting of a microcomputer housed in the camera body (18).
) and the structure of the drive control of the variator (4) and compensator (5) are shown in an easy-to-understand circuit diagram. Here, (44) is a selection switch for selectively switching the focus adjustment between AF (autofocus) mode and manual mode (power focus mode), and when it is off, it is the AF mode, and when it is on, it is the selection switch. The system controller (35) is controlled to enter power focus mode. (45) is a power focus operation switch, which is composed of 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 not possible (i.e. when the contrast of the subject is too low or the subject is too dark) or when you want to achieve the desired focus, and it cannot be done manually. The focus is adjusted by driving the compensator via electric means. (
Reference numeral 36) indicates a zoom operation switch, and a tele switch (36A) for zooming in the tele direction and a wide switch (36B) for zooming in the wide direction are shown. The system controller (35) is configured not to accept zoom operations when the power focus mode is selected by the selection switch (44). This configuration can be easily realized with a logic circuit that combines the signals from the zoom operation switch (36) and the selection switch (44).

As shown in FIG. 3, the distance measurement module (28) has a condenser lens (40) that focuses light that has passed through different pupils of the distance measurement lens (27), and an aperture mask (
41), re-imaging lens (42), CCD line sensor (
43). Note that (39) indicates the equivalent position of the imaging plane. In Figure 3, the subject light entering the distance measuring system is passed through the condenser lens (40) and the aperture mask (41).
), CCD line sensor (
43) Create two subject images above. The system controller (35) detects the amount and direction of deviation from the in-focus position by detecting the relative positional relationship between these two images, and drives the compensator (5) to bring it into focus. Close. Incidentally, since such focus detection is disclosed in Japanese Patent Laid-Open No. 60-4914, etc., it will not be described in detail here.

Next, the operation of this embodiment will be explained.

The system controller (35) first selects the selection switch (
44) is the AF mode or the power focus mode. In the case of AF mode, focus detection calculation is performed based on the detection signal from the ranging module (28),
The AF motor drive circuit (
38) drives the AF motor (15) and moves the compensator (5) to adjust the focus of the subject.

At this time, when the zoom operation switch (36) is operated, the zoom motor drive circuit (37) and the zoom motor (14) are also driven via the system controller (35) to move the variator (4). When the variator (4) moves, the positional relationship between the front lens group (3), the variator (4), and the compensator (5) changes, and the position of the imaging plane changes, which is applied to the distance measurement module (28). The subject light also changes, and the focus detection calculation results also change accordingly. Based on this calculation result, further compensator (5)
The camera performs fine adjustment to constantly correct changes in the position of the imaging plane due to movement of the variator (4) to obtain a focused image. Note that in the AF mode state, the system controller (35) prohibits input from the power focus operation switch (45). This is because even though the AF motor (15) moves and focuses based on the focus detection results, inputting an external signal that causes it to perform a different movement may cause malfunction. It is.

Next, the operation when the selection switch (44) is set to power focus mode will be described.

In power focus mode, the system controller (
35) prohibits input from the ranging module (28),
If you disable AF operation, Hong will press the zoom operation switch (44).
) and also prohibits zooming operations.

In this state, when the near switch (45A) or the far switch (45B) of the power focus operation switch (45) is turned on, the system controller (35) responds to this and drives the AF motor through the AF motor drive circuit (38). (I5) to move the compensator (5) to the near side or far side.

In Figure 2, the power focus operation switch (45
) and zoom operation switch (36) are provided separately, but as can be seen from the above operation description, these switches (36)
) In (45), when one mode is used, the other is not used. Therefore, one of the switches (3G) and (45) may be deleted and the remaining switch may be used to switch between the power focus mode and the zooming mode by the signal from the selection switch (44). In this case, it is possible to enjoy the advantage that the number of parts is reduced.

Although the present invention has been described above with reference to examples, the present invention is not limited to these examples. Modification is possible.

For example, it is also possible to operate the front lens group (3) as a compensator, and in this case, the AF motor (15)
What is necessary is to change it so that it is connected to the front lens group (3).

Effects of the Invention According to the present invention, when the focus compensator, which is driven independently of the zooming variator, is driven in the power focus mode, the zoom operation is prohibited, so that the imaging plane position cannot be compensated. There are no operating methods required, and you can always obtain images with the optimal focus state.

In addition, since the zoom operation means and the power focus operation means are in a mode in which one is used, the other is not used, so it is possible to adopt a configuration in which one operation means is also used, and in such a case, parts This reduces the number of points and also contributes to miniaturization.

[Brief explanation of the drawing]

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 measurement 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.

Claims (2)

[Claims] (1) A zoom variator consisting of a variable magnification lens group,
A compensator that functions as a focus adjustment for compensating for image plane displacement, a first drive means that drives the variator, a second drive means that drives the compensator, and an autofocus mode and a power focus mode. zoom operation means for operating the first drive means; focus detection means for driving the second drive means in autofocus mode; and focus detection means for driving the second drive means in autofocus mode; 1. A camera having a power focus operation means for operating a drive means, characterized in that zoom operation by the zoom operation means is prohibited in a power focus mode. (2) The camera according to claim 1, wherein the power focus operation means and the zoom operation means are constituted by a common switch.