JPH04311909A - Camera system - Google Patents

Abstract

PURPOSE:To obtain a camera system which takes adequate variable power action in focusing and precise focusing action by using a rear-focus zooming lens which can change variable power positions for a unfocused-distance subject. CONSTITUTION:When a focusing lens group 4 which consists of partial lens in a variable power section or partial lens arranged on the image surface side of the variable power section is focused by the movement along a light axis and when the variable power section is given variable power at a fixed speed in the state of focusing a finite-distance subject and at this time entered into a variable power area where the finite-distance subject is not focused, a variable power speed of the variable power section is changed in accordance with AF signals from a focus detecting means.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a camera system.
In particular, the present invention relates to a camera system that appropriately performs a focusing operation in a so-called rear focus type photographing system having a variable magnification system such as an image input device, a photographic camera, a video camera, or the like.

0002

2. Description of the Related Art A so-called rear focus type zoom lens is one of photographic systems having a variable magnification system used in photographic cameras, video cameras, and the like.

FIG. 5 shows a rear focus type photographing system SL in which a part of the lens group 104 of the relay lens behind the variable magnification system is used as a focusing lens group and is moved on the optical axis to perform focusing. 1 is a schematic diagram of main parts of a camera system. In the figure, a lens group 101 and a lens group 103 are fixed, and the lens group 102 as a variator is moved in the optical axis direction by a focal length adjusting means 112 consisting of a motor or the like to change the magnification.

Further, the lens group 104 has the role of both correcting image plane fluctuations during zooming and adjusting focus. That is, Figure 5
With this lens configuration, both when the subject distance changes and when the focal length (zoom position) of the shooting system changes,
In both cases, focusing is performed by changing the position of the focusing lens group 104 on the optical axis, so that the focal plane is positioned at a predetermined position, for example, on the image sensor surface.

FIG. 3 shows the position of the zoom lens group 102 on the horizontal axis, that is, the zoom position, in the photographing system SL of FIG. It is an explanatory diagram when position is taken and object distance is taken as a parameter. As shown in FIG. 3, the position of the focusing lens group on the optical axis (cam locus) for each object distance varies depending on the zoom position. Furthermore, due to mechanical constraints, for example, for close-range objects (curves 32 and 35), there is a region (region indicated by a dotted line) out of focus during zooming.

In FIG. 5, an object image is formed on the surface of the image sensor 105 by the photographing system SL. Image sensor 10
The signal related to the object image obtained in step 5 is amplified by an amplifier 106, passed through a high-pass filter 107, and then sent to a microcomputer 108.
I am sending it to

FIG. 4 is an explanation showing the relationship between the focus signal regarding the object image at this time, that is, the AF signal, and the position on the optical axis of the focusing lens group 104 of the photographing system, that is, the focus state (focus state). It is a diagram. In the figure, A obtained by the image sensor 105
The position on the optical axis of the lens group 104 where the F signal has the highest value is the focal position.

In FIG. 5, the microcomputer 108 is connected to the image sensor 1.
The in-focus state is determined from the AF signal obtained in step 05, and a command to drive the motor 111 is issued to the motor driver 109 for focusing. As a result, the motor 111 drives the focusing lens group 104 to focus.

In the camera system shown in FIG. 5, when the zoom drive switches 113 and 114 are pressed and turned on, the microcomputer 108 detects this and issues a command to the zoom motor driver 110 to drive the zoom motor 112. . As a result, the zoom motor 112 is connected to the zoom lens group 102.
The magnification is changed by driving the .

At this time, a position detection encoder (not shown) detects the variable power position of the lens group 102, and in accordance with the movement of the lens group 102, the focusing lens group 104 is moved along the cam trajectory shown in FIG. This corrects the focal plane that changes due to zooming.

[0011]

Generally, as shown in FIG. 3, the focusable object distance varies depending on the zoom position of the zoom system. Therefore, even if the object is at the same distance, when changing the magnification from the telephoto end to the wide-angle end after focusing on an object at a finite distance, as shown in curve 35 in FIG. Since the focusing lens group is movable up to position e2, the focus is achieved.

However, the focusing lens group becomes unable to move after passing the magnification change position e2 and reaches the magnification change position e3 due to mechanical constraints (it is fixed on the straight line 33). As a result, the image becomes out of focus.

When zooming is further performed, the focusing lens group becomes movable from the zooming position e3 to the wide-angle end e4, that is, it moves along the locus of the curve 35, so that the focusing lens group becomes movable from the zooming position e3 to the wide-angle end e4. It becomes.

When zooming is performed while focusing on an object at a finite distance as described above, if the movement of the focusing lens group is mechanically restricted and the object is out of focus, the predetermined zooming is performed. region(
In Fig. 3, the variable magnification area from point e2 to point e3) remains out of focus and continues variable magnification until it reaches the variable magnification position e3 where it can be focused. In example 3, focusing is performed along curve 35).

However, at this time, if the magnification changing speed of the magnification changing section is performed at the normal magnification changing speed, it is difficult to accurately change the magnification to the focal point e3, and in many cases, the magnification changing position e3 The problem was that the lens passed through the lens, making it impossible to focus and changing the magnification to the wide-angle end.

Incidentally, this also applies when changing the magnification from the wide-angle end to the telephoto end.

According to the present invention, when a finite-distance object is focused and magnification is changed, the amount of movement of the focusing lens group is restricted due to mechanical constraints, and the lens group becomes out of focus from a predetermined magnification change position. When changing magnification along a predetermined cam trajectory where focusing is possible from the magnification changing position where focusing is possible, controlling the magnification changing speed of the magnification changing unit causes the object to pass through the in-focus position. The purpose of the present invention is to provide a camera system that prevents this and enables accurate focusing.

[0018]

[Means for Solving the Problems] The camera system of the present invention includes a focusing lens group consisting of some lenses of a variable magnification section or at least some lenses arranged on the image plane side of the variable magnification section. It has a photographing system that performs focusing by moving on the optical axis, and a focus detection means that detects focus information of the photographing system, and changes the magnification unit at a constant speed while focusing on a finite distance object. magnification, and at this time, when the finite-distance object enters a variable magnification region where it is out of focus, the variable magnification speed of the variable magnification section is changed based on the AF signal from the focus detection means. It is a feature.

In addition, in the present invention, focusing is performed by moving a focusing lens, which is a part of the lens of the variable power unit or at least a part of the lens arranged on the image plane side of the variable power unit, on the optical axis. and a focus detection means for detecting focus information of the imaging system, and the focusing lens group moves in order to correct image plane fluctuations due to zooming of the zooming section, and has a finite When the zoom unit changes the magnification while focusing on a distance object, and the movement of the focusing lens is restricted and the lens enters the zoom range where it is out of focus, the zoom unit changes the magnification. It is characterized in that the double speed is changed based on a signal from the focus detection means.

[0020]

Embodiment FIG. 1 is a schematic diagram of a main part of Embodiment 1 of the present invention. In the figure, SL is a photographing system (photographing lens) and has a variable magnification system.

The photographing system SL according to the present invention has a rear focusing lens configuration similar to that of the conventional photographing system shown in FIG.

That is, 1 is a fixed first group, 2 is a second group for zooming (variable magnification lens group), 3 is a fixed third group, and 4 is a lens for adjusting image plane fluctuations due to zooming. A fourth group (focusing lens group) having a function of performing correction and focus adjustment, 5 is an image pickup device.

Each element of the camera system of this embodiment as a whole is substantially the same as the camera system shown in FIG.

That is, in this embodiment, an object image is formed on the surface of the image sensor 5 by the photographing system SL. Image sensor 5
A focus signal (AF signal) related to the object image obtained is amplified by an amplifier 6 and sent to a microcomputer 8 via a high-pass filter 7.

The image pickup device 7, amplifier 6, high-pass filter 7, and microcomputer 8 constitute one element of focus detection means. At this time, the focus signal related to the object image, that is, the AF
the position on the optical axis of the focusing lens group 4 of the signal and photographing system SL;
In other words, the relationship with the in-focus state is as shown in FIG. In the figure, a position 41 on the optical axis of the lens group 4 where the value AF of the AF signal obtained by the image sensor 5 becomes the highest value is the in-focus position. That is, the position 41 is the focus position where the high frequency component of the video signal increases.

The microcomputer 8 determines the in-focus state from the AF signal obtained by the image sensor 5, and issues a command to drive the focus motor 11 to the focus motor driver 9. As a result, the focus motor 11 drives the focusing lens group 4 to focus.

In the camera system of this embodiment, when the zoom drive switches 13 and 14 are pressed and turned on, the microcomputer 8 detects this and turns on the zoom motor driver 10.
A drive command for the zoom motor 12 is issued. Thereby, the zoom motor 12 drives the variable power lens group 2 to perform variable power.

At this time, the position of the variable power lens group 2 is detected by the position detection encoder 20, and the focusing lens group 4 is moved along the cam trajectory shown in FIG. 3 according to the movement of the variable power lens group 2. The focal plane (image plane) that changes due to magnification is corrected by moving the lens along the lens.

In this embodiment, as shown in FIG.
Assume that the object distance is changed from the distance to a finite distance object (object distance shown by curve 35).

Assume that the zoom position at this time is the telephoto end e1. Suppose that you change the magnification from the telephoto end to the wide-angle end. From the telephoto end e1 to the variable power position e2, the focusing lens group moves along the curve 35, resulting in focus. Magnification position e2
If the focusing lens group is moved on the trajectory shown by the dotted line of the curve 35 from to the zooming position e3, focusing is achieved.

However, due to mechanical constraints, the focusing lens group cannot be moved from the zooming position e2 to the zooming position e3. At this time, the focusing lens group is a straight line 33
It is located above. Therefore, the magnification is changed from the zooming position e2 to the zooming position e3 while remaining in an out-of-focus state.

At this time, the zooming speed of the zooming section, ie, the zooming speed of the zooming lens group 2, is changed based on the AF signal from the microcomputer 8. Specifically, if the magnification change position e3 is expressed as a point e3 below, it is possible to focus on a finite distance object at the point e3. However, if the magnification change speed at this time is fast, the lens may pass through point e3 and cannot be brought into focus. Also, if the zooming speed is made slower from the beginning, the focusing accuracy will be higher, but it will take too much time, which is not good.

Therefore, in this embodiment, the microcomputer 8 takes advantage of the property that the AF signal obtained from the image sensor 5 increases as shown in FIG.
While monitoring the focusing signal obtained from the image sensor 5, the magnification change speed is slowed down when the AF signal reaches a predetermined value (for example, the threshold level in FIG. 4).

This allows the zooming unit to be accurately positioned at the zooming position of point e3 for focusing, and then, while changing the zoom, the focusing lens group 4 is moved along the locus of the curve 35. It moves to maintain focus.

Next, the operation of this embodiment will be explained using the flowchart shown in FIG. The flowchart in FIG. 2 mainly shows a flowchart in a program executed inside the microcomputer 8.

At step 200, an AF signal is obtained. That is, an AF signal based on a high frequency component obtained from a video signal output by the image sensor 5 via an amplifier 6 and a filter 7 is taken in.

At step 201, it is determined whether or not the photographing system is in focus based on the AF signal taken in at step 200. In step 202, when it is determined in step 201 that the object is out of focus, the focusing lens group 4 is driven in the focusing direction. In step 203, the switch 13 determines whether or not a zooming operation is being performed when focus is determined in step 201.
Judgment is made from the output of 14.

In step 204, the electronic cam curve (each cam trajectory in FIG. 3) stored in the ROM of the microcomputer 8 is applied based on the positional information of the variable power lens group 2 and the focusing lens group 4 obtained from the encoders 20 and 21. Along this line, both lens groups 2 and 4 are changed in magnification at a constant speed.

In step 205, it is determined from the output from the encoder 21 whether the position of the focusing lens group 4 is at the close end. Step 206 compares the AF signal output level from the filter 7 in the current field with that in the previous field.

In step 207, it is determined whether the AF signal output from the filter 7 exceeds an AF signal threshold level, which will be described later. When the AF signal exceeds the threshold level, the variable magnification speed is made slower than the variable magnification speed set in step 204 in step 208. That is, information for duty drive for slowing down the variable magnification speed is read from the ROM of the microcomputer 8 and executed.

[0041] At this time, the above operation is performed with the magnification change speed slowed down until focus is obtained. When the image is in focus, the zooming speed is changed to the standard original speed at step 210, and the zooming operation is performed at step 203.

Next, steps 204 to 210 will be described in detail with reference to FIGS. 3 and 4. In FIG. 3, for example, it is assumed that the object distance is represented by a curve 35.

First, when zooming is performed from point e1 (telephoto end) to point e2, the closest end of the focusing lens group 4 is detected at point e2 using the output signal from the encoder 21 (step 20).
5). Since the zooming range from point a to point e2 is in focus, this corresponds to the position of point 41 in FIG. 4, and the AF signal has the highest value. Magnification is changed from point e2 toward the wide-angle end. At this time, the focusing lens group 4 cannot be moved toward close range due to mechanical constraints, and the in-focus state gradually deteriorates.

That is, as shown in FIG. 4, the level of the AF signal decreases. As the magnification is further changed and the point e3 is approached, the level of the AF signal increases.

This state is determined by the microcomputer 8 (step 206). When it is determined in step 206 that the level of the AF signal has increased, it is determined in step 207 whether or not the photographing system is near focus. This is done by determining whether or not the object is close to in-focus based on the threshold level shown in FIG. 4, and when this threshold level is exceeded, it is determined that the object is close to being in-focus. Then, when it is determined that the focus is near, the variable magnification speed is slowed down (step 208).

As a method for slowing down the speed of the zoom motor 12 in order to slow down the speed of zooming at this time, duty driving can be applied, but changing the voltage applied to the zoom motor 12 can also be used.

From the above, when the point e3 comes close to being in focus, the speed of magnification is slowed down, and the magnification is changed slowly until the magnification position of point e3 is brought into focus, so that accurate focus can be achieved at point e3. (Step 209). After the image is in focus, the variable magnification speed is returned to the original value, and the variable magnification is performed up to the wide-angle end at point e4 (step 210).

According to this method, the speed of magnification can be slowed down only near point e3, and a stable in-focus image can always be obtained outside the magnification range from point e2 to point e3 without passing through point e3. be able to.

Although this embodiment has been described with respect to changing the magnification from the telephoto end to the wide-angle end, it is similarly applicable to changing the magnification from the wide-angle end to the telephoto end.

Furthermore, instead of detecting the closest end of the focusing lens group 4 using the encoder 21, a pulse motor is used for the focus motor 11, and the motor driving pulses from the microcomputer 8 are counted, and this pulse counter is used. You can use it.

Furthermore, instead of using the AF signal to detect the vicinity of the in-focus point e3, the approximate in-focus position may be predicted from the position information of the zoom encoder 20.

[0052]

Effects of the Invention According to the present invention, within the variable power range where the movement of the focusing lens is restricted due to mechanical constraints and cannot be focused, the variable power range can be changed in an out-of-focus state. When returning to a variable magnification position where focusing is possible, as described above, changing the variable magnification speed of the variable magnification unit near the in-focus point prevents the lens from passing through the in-focus position, resulting in accurate focusing. A camera system that can obtain the state can be achieved.

[Brief explanation of drawings]

FIG. 1: Schematic diagram of main parts of Embodiment 1 of the present invention

[Figure 2] Flowchart of the operation in Figure 1

[Figure 3] An explanatory diagram of the movement trajectory of the focusing lens group at each variable power position

[Fig. 4] Explanatory diagram showing the relationship between the in-focus state and the AF signal

[Figure 5] Schematic diagram of main parts of a conventional camera system

[Explanation of symbols]

SL Photography system 2. Lens group for variable magnification 4 Focusing lens group 5 Imaging device 6 Amplifier 7 High pass filter 8. Microcomputer 9 Motor driver 10 Motor driver 11 Motor 12 Motor 13 Switch 14 Switch

Claims (4)

[Claims] Claim 1: Photography in which focusing is performed by moving a focusing lens, which is a part of a lens in a variable power unit or at least a part of a lens arranged on the image plane side of the variable power unit, on the optical axis. system and a focus detection means for detecting focus information of the photographing system, and the magnification changing section is configured to change the magnification at a constant speed while focusing on the finite distance object, and at this time, 1. A camera system characterized in that when the camera system enters a variable magnification region where the focus is out of focus, the variable magnification speed of the variable magnification section is changed based on a signal from the focus detection means. 2. An imaging system that performs focusing by moving a focusing lens consisting of a part of a lens in a variable power unit or at least a part of a lens disposed on the image plane side of the variable power unit on the optical axis. and a focus detection means for detecting focus information of the photographing system, and the focusing lens moves to correct image plane fluctuations due to zooming of the zooming unit, and focuses on an object at a finite distance. When the magnification is changed using the magnification changing section with the lens in focus, and the movement of the focusing lens is regulated and the magnification changes into an area where it is out of focus, the magnification changing speed of the magnification changing section must be changed. A camera system characterized in that the focus is changed based on a signal from the focus detection means. 3. The camera system according to claim 1, wherein the zooming speed of the zooming unit is slowed down based on the signal from the focus detection means. 4. Changing the magnification speed of the magnification changing section includes:
4. The camera system according to claim 1, wherein the detection is performed based on a signal detected near in-focus by the focus detection means.