JPH04190206A - Automatic focusing apparatus - Google Patents

Abstract

PURPOSE:To perform focusing operation with higher accuracy by relatively displacing all lens groups and a photographing means by positional errors thereof as measured from a focusing target position along the optical axis, after performance of a zooming operation. CONSTITUTION:On the basis of the output signal from a distance measuring means 15, a photographing object distance is calculated, and the position of CCD 18, as taken along the optical axis, corresponding to this object distance is calculated by operation of a system controller 16, or the position A of CCD 18 as taken along the optical axis is selected from the previously stored data. Next, the positional errors of a first lens group 1 and a second lens group 2 as taken from specific positions are sensed in accordance with the output signals from the position sensors 21, 22, whereby the system controller 16 calculates the correction value B of CCD 18 as applied along the optical axis, or selects this correction value B from the previous stored data, which correction value B is added to the CCD 18 position corresponding to the photographing object distance (A + B). Then, a motor 25 is driven via a motor drive circuit 27 to adjust CCD 18 position by means of a feed screw 24, whereby the controller 16 stops the motor 25 when a target value signal is inputted thereto from a position sensor 26.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to an improvement in an automatic focusing device disposed in a video camera, still camera, or the like.

(Background of the Invention) FIG. 4 is a diagram showing the mechanical and electrical configuration of the main parts of a conventional device of this type.
1 shows an imaging device having a charge-coupled device (charge-coupled device).

In the figure, 1 is a concave 1121st lens group that has a focusing function and a focus shift correction function during zooming, and 2 is a convex second lens group that is a variator that has a variable power function during zooming. Luns group 1. 2nd lens group 2
This constitutes a two-group zoom. Reference numeral 3 designates a holding frame that holds the first group of lenses 1 therein, and has a male helicoid portion 3a formed at one end and a gear portion 3b formed at the other end. Reference numeral 4 denotes a moving member having a female helicoid portion 4a formed on its inner periphery, and is helicoidally coupled to the holding member 3. A holding frame 6 holds the second lens group 2 inside.

8 is a fixed barrel; 9 is a zoom ring having a gear portion 9a formed at one end; the zoom ring 9 rotates around the optical axis along the outer periphery of the fixed barrel 8 without moving in the optical axis direction; It is attached to the fixed cylinder 8 in such a manner as to. 5.7 is the moving member 4. These bottles are installed in the holding frame 6, and these bottles 5
．． 7 is fitted into a rectilinear groove formed in the fixed barrel 8, and further fitted into a cam groove formed in a zoom ring 9, thereby forming a known zoom mechanism. Reference numeral 10 denotes a zoom motor having a gear 11 fixed to its shaft 10a, and the gear 11 meshes with the gear portion 9a of the zoom ring 9, thereby controlling energization of the zoom motor 10 (normal rotation and reverse rotation). Zooming is performed by this.

12 is a focusing motor having a gear 13 fixed to its shaft 12a, and the gear 13 meshes with the gear portion 3b of the holding frame 3, so that the focusing motor 1
2 is energized (normal rotation).

The holding frame 3 rotates around the optical axis by rotating the holding frame 3 (reversely), and the male helicoid part 3a of the holding frame 3 and the female helicoid part 4a of the moving member 4 are engaged, so that the holding frame 3 is moved. The 1121st member moves in the optical axis direction relative to the member 4.
Group 1 moves to perform focusing. 14 is a position sensor that detects the position of the focusing motor 12 in the rotational direction, and the focusing of the 1121st group 1 is determined based on the gear ratio of the gear 13 and the gear portion 3b of the holding frame 3 and the pitch of the helicoid portions 3a and 4a. It detects the amount of movement in time.

Reference numeral 15 denotes a distance measuring means, which measures the object distance by the principle of triangulation or by detecting reflected waves of ultrasonic waves. Reference numeral 16 denotes a system controller consisting of a microcomputer, which controls the entire imaging apparatus including the apparatus and performs various calculations. Reference numeral 17 denotes a motor drive circuit for driving the focusing motor 12. 18 is a C0D (charge coupled device) which is an image sensor. 19 is a motor drive circuit that drives the zoom motor 10 described above.

In the above configuration, when the zoom ring 9 rotates via the gear 11 by controlling the power supply to the zoom motor 10 via the motor drive circuit 19, the bin 5.7 moves into the fixed barrel 8 according to the cam groove of the zoom ring 9. The moving member 4. is displaced in the optical axis direction within the straight groove of the moving member 4. Holding frame 3. No. 1121
Group 1 and holding frame 6. The second lens group 2 is integrally displaced in the optical axis direction to perform zooming.

Next, the amount of one rotation in the rotational direction of the focusing motor 12 determined by the system controller 16 based on the object distance information calculated from the output from the distance measuring means 15 is as follows.
Alternatively, the amount of one rotation in the rotational direction of the focusing motor 12 selected from data stored in advance in the system controller 16 corresponding to the subject distance information is
When the system controller 16 outputs the signal to the motor drive circuit 17, the focusing motor 12 starts rotating.

The rotational state of this focusing motor 12 is determined by the position sensor 1.
4, and the system controller 16 accelerates the motor drive circuit 17 so that the focusing motor 12 rotates to the target position while monitoring the signal from the position sensor 14.

It will output signals for deceleration, braking, etc.

The rotational output of the focusing motor 12, which is rotationally controlled as described above, is transmitted to the holding frame 3 via the gear 13, and the holding frame 3. The lens group 1 is displaced in the optical axis direction, and focusing is performed.

By the way, in recent years, image sensors such as COD
18 has been miniaturized, and what used to be the mainstream 2/3 inch size has now been reduced to 1/2 inch size, and even 1/3 inch size.
It is becoming inch size. By achieving miniaturization in this way, the permissible diameter of the circle of confusion on the imaging surface becomes smaller, and therefore, high precision positioning in the optical axis direction is required when zooming and focusing the photographic lens as described above. be done.

In addition, lenses have been made smaller, and this has increased the focus sensitivity of each lens group, that is, the ratio of the focus movement of the imaging plane to the displacement of each lens group in the optical axis direction.
High-precision lens positioning is required. Therefore, conventional lens positioning mechanisms suffer from backlash in the drive system, backlash in the lens holding frame, and distortion of the lens holding frame during driving.

Furthermore, the expansion and contraction of the lens holding frame and lens barrel due to changes in temperature and humidity allows for highly accurate focusing.

Additionally, in order to solve the above-mentioned problems, it may be possible to provide a high-precision lens feeding mechanism, but this would lead to an increase in the size of the device, which is contradictory to realizing a more compact device. .

(Objective of the Invention) The object of the present invention is to solve the above-mentioned problems and to enable more precise focusing without providing a high-precision lens feeding mechanism that would lead to an increase in the size of the device. An object of the present invention is to provide an automatic focusing device.

(Features of the Invention) In order to achieve the above object, the present invention includes a position detecting means for detecting the position of at least one lens group with relatively high focus sensitivity in the optical axis direction, and a position detecting means for detecting the position of at least one lens group with relatively high focus sensitivity, and , a focusing operation for performing a focusing operation by relatively displacing all the lens groups held by the lens holding means and the imaging means based on the output from the position detection means and the output from the distance measuring means; After performing the zooming operation, the position detecting means detects the error between the focus target position in the optical axis direction and that is caused by, for example, rattling or loosening of the lens holding means, or expansion and contraction due to temperature, etc. The error is determined by the output of the means, and is corrected by relatively displacing all the lens groups and the imaging means by this error.

(Embodiment of the Invention) FIG. 1 is a diagram showing the mechanical and electrical configuration of main parts in an embodiment of the present invention, and the same members as in FIG. 4 are given the same numbers. Further, the lens optical system and lens barrel constitute a known zoom mechanism, as in the conventional example.

In FIG. 1, reference numeral 20 denotes a holding frame that holds the 1121st group 1 therein, and a bottle 5 is implanted therein, and unlike the conventional example, no helicoid is formed. 21 is the 1121st
A high-resolution position sensor 22 detects the position of the holding frame 20 or the bin 5 in the optical axis direction which is displaced integrally with the group 1;
This is a high-resolution position sensor that detects the position of the holding frame 6 or bottle 7 in the optical axis direction, which is displaced integrally with the lens group 2.

23 is a CCD holder to which COD 18 is fixed;
A nut portion is formed inside and engages with the feed screw 24. 25 has a feed screw 24 on its shaft 25a.
is a fixed motor, and as the motor 25 rotates, the CCD holder 23 and CCD 18 are movable in the optical axis direction. 26 is the position of the CCD holder 23;
That is, it is a high-resolution position sensor that detects the position of the CCD 18 in the optical axis direction. 27 is a motor drive circuit that drives the motor 25.

Next, the operation of the above configuration will be explained using the flowchart shown in FIG.

When the zoom motor 10 is energized and controlled via the motor drive circuit 19, zooming is performed as described above, and the 1121st lens group 1 and the second lens group 2 are driven (#
1).

At this time, if each lens group is displaced without error, the CCD
The position of 18 is uniquely determined by the output of distance measuring means 15. However, during zooming, the machining accuracy of the cam groove of the zoom ring 9, the play of the pin 5.7 in the cam groove of the zoom ring 9,
Alternatively, each lens group may be positioned with an error relative to a predetermined position due to play in the zoom ring 9, expansion and contraction due to temperature, and the like. Even if this error is several microns, if the focus sensitivity of each lens group is high, it will be magnified on the CCD 18 surface, that is, the imaging plane, and will be detected as a blur. To solve this problem, it is necessary to control the position of each lens group with high precision. There are various high-resolution position sensors such as optical and magnetic types, but in order to drive and control each lens group, a high-precision feeding mechanism is required, which increases the size of the device.

Therefore, in this embodiment, as described later, the position of each lens group is detected by high-resolution position sensors 21 and 22, and the displacement (shift) of the imaging plane relative to the error is detected by the CCD 18, the motor 25, and the position sensor 21, 22. By controlling the drive using the sensor 26 and the motor drive circuit 27, the correction is made, thereby preventing the device from becoming larger.

Next, the object distance is calculated based on the output from the distance measuring means 15 (#2), and then the CCD corresponding to the object distance is
The position A of the CCD 18 in the optical axis direction is calculated by the system controller 16, or the position A of the CCD 18 in the optical axis direction is selected from data stored in advance inside the system controller 16 (#3) Next, the position sensors 21 and 22 The output from the lun group 1. To detect the error from the predetermined position of the second lens group 2 (#4), the system controller 16
calculates the correction value B in the optical axis direction of the CCD 18, or selects the correction value B from data stored in advance inside the system controller 16 #5), and adds it to the position of the CCD 18 corresponding to the subject distance. (A+B)L (#6)
The motor 25 is driven and controlled via the motor drive circuit 27, the position of the CCD 18 is controlled by the feed screw 24, and the CCD 18 is stopped when a signal that reaches a target value is input from the position sensor 26.

Here, if each lens group has high focus sensitivity, and if each lens group is individually displaced to perform focusing operation, precise positioning on the micron order is required, but as in the above example, When a focusing operation is performed by changing the relative position of the entire photographing lens and the CCD 18, the focus sensitivity is "1", and accurate focusing can be performed without using a special mechanism.

Therefore, in this first embodiment, after detecting the position of each lens group, the CCD 18 is driven and controlled to correct the error.

FIG. 3 is a diagram showing the mechanical and electrical configuration of the main parts in a second embodiment of the present invention, and the same members as in FIGS. 1 and 4 are given the same numbers. Further, each lens group and zoom mechanism are the same as those shown in FIG.

In the first embodiment, the position of each lens group is detected after zooming as described above, and based on this result, the CC
D1B is drive-controlled to correct errors (simultaneously during focusing), but in this second embodiment, after detecting the position of each lens group, the entire photographic lens is drive-controlled to correct errors. I try to do that.

In Fig. 3, 28 is a fixed cylinder;
In the figure, the fixed barrel 8 is fixed to a fixing member within the device, but in this embodiment, the fixed barrel 28 is fixed to a holder 29, which will be described later, and in the optical axis direction by a mechanism to be described later. It is possible to move in a straight line. Reference numeral 29 is the aforementioned holder, which has a nut portion formed therein and meshes with the feed screw 31. 30 is a motor, its shaft 3
A feed screw 31 is fixed to 0a. A high-resolution position sensor 33 detects the position of the fixed barrel 18 in the optical axis direction, that is, the position of the entire lens in the optical axis direction.

32 is a motor drive circuit that drives the motor 30.

In this second embodiment, the position sensors 21, 22 are adapted to detect the position of the holding frame 20 or the bottle 5, and the holding frame 6 or the bottle 7 relative to the fixed barrel 28. Further, the focusing operation is performed by driving the entire lens optical system and adjusting the distance from the COD 18 in the optical axis direction.

Next, the operation in the above configuration will be explained.

When the zoom motor lO is energized and controlled via the motor drive circuit 19, zooming is performed in the same manner as in the first embodiment (the case of FIG. 4), and the lens group 1 and the second lens group 2
is driven.

Next, the object distance is calculated based on the output from the distance measuring means 15, and then the position of the optical system, that is, the fixed barrel 28, in the optical axis direction corresponding to the object distance is determined by the system controller 15.
The position of the fixed barrel 28 in the optical axis direction is selected by calculation or from data stored in advance inside the system controller 16. Next, based on the outputs from the position sensors 21 and 22, the first lens group 1. Detecting the error of the second lens group 2 from a predetermined position, the system controller 16 calculates a correction value of the fixed barrel 28 in the optical axis direction, or the system controller 16
A correction value is selected from internally stored data in advance, added to the position of the fixed tube 28 corresponding to the subject distance, the motor 30 is driven and controlled via the motor drive circuit 32, and the fixed tube 28 is moved by the feed screw 31. The position is controlled and stopped when a signal having a target value is input from the position sensor 33.

According to each of the above embodiments, zooming is performed by displacing each lens group, and focusing is performed by changing the distance between the lens optical system and the CCD. The position of the relatively high lens group is detected, and based on this, the lens optical system and C
By correcting the distance of the CD, it has become possible to perform more accurate focusing operations without a complicated configuration.

(Effects of the Invention) As described above, according to the present invention, the position detection means for detecting the position of at least one lens group with relatively high focus sensitivity in the optical axis direction and the zooming means after the zooming operation is completed , a focusing operation for performing a focusing operation by relatively displacing all the lens groups held by the lens holding means and the imaging means based on the output from the position detection means and the output from the distance measuring means; After performing the zooming operation, the position detecting means detects the error between the focus target position in the optical axis direction and that is caused by, for example, rattling or loosening of the lens holding means, or expansion and contraction due to temperature, etc. Since the error is determined by the output of the device and corrected by relatively displacing all lens groups and the imaging device by this error, a high-precision lens feeding mechanism is required, which would lead to an increase in the size of the device. It becomes possible to perform more accurate focusing without having to

[Brief explanation of drawings]

FIG. 1 is a mechanical and electrical configuration diagram of the main parts of an automatic focusing device showing a first embodiment of the present invention, FIG. 2 is a flowchart showing its operation, and FIG. 3 is a diagram showing a second embodiment of the present invention. FIG. 4 is a mechanical and electrical configuration diagram of the main parts of an automatic focusing device according to an embodiment. FIG. 4 is a mechanical and electrical configuration diagram of the main parts of a conventional automatic focusing device. 1... Second lens group, 2... Second lens group, 3... Holding frame, 4... Moving member,
9...zoom ring, 10...zoom motor, 12...focus motor, 15...
... Distance measuring means, 16 ... System controller, 18 ... CCD, 20 ... Holding frame, 22 ... CCD holder, 24 ...・・・・・・
Feed screw, 25...Motor, 26...
Position sensor, 27...Motor drive circuit, 28.
...Fixed barrel, 29...Holder, 30...
...Motor, 31...Feed screw, 32...
...Motor drive circuit, 33...Position sensor.

Claims (1)

[Claims] (1) A distance measuring device that measures the distance to a distance measurement target, a lens holding device that holds at least one lens group with relatively high focus sensitivity, and at least one lens group held by the lens holding device. In an automatic focusing device comprising a zooming means for performing zooming by moving in an optical axis direction, and an imaging means, a position for detecting a position in an optical axis direction of the at least one lens group having relatively high focus sensitivity. After the zooming operation by the detection means and the zooming means is completed, all the lens groups held by the lens holding means and the imaging means are detected based on the output from the position detection means and the output from the distance measurement means. 1. An automatic focusing device comprising: focusing operation execution means for performing a focusing operation by relatively displacing the camera.