JPH0774997A - Automatic focusing device for still video camera - Google Patents

Abstract

PURPOSE:To shorten time to be required for automatic focusing by detecting a direction to which a photographing lens is to be moved at the time of starting automatic focusing operation. CONSTITUTION:The 1st CCD 21 is fixed on a position separated from the photographing lens 11 by a fixed optical path length. The 2nd CCD 22 is arranged on the position having the same optical path length as that of the 1st CCD 21. At the time of executing automatic focusing, the optical path length of the 2nd CCD 22 from the lens 11 is changed, and under the state, AF signals are detected based upon output signals from the 1st and 2nd CCDs 21, 22. Since the AF signals obtained from the 1st and 2nd CCDs 21, 22 are mutually different, a moving direction for focusing the lens 11 is determined based upon the difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focus adjusting device provided in a still video camera for positioning a taking lens at a focus position.

[0002]

2. Description of the Related Art As a conventional still video camera, there is known a still video camera configured to use two image pickup devices provided for detecting an image also for automatic focus adjustment. In this automatic focus adjustment device, the in-focus state of the photographing lens is detected by the contrast method based on, for example, the light amount distribution on one screen obtained by each image sensor.
That is, the photographing lens is set at a position where the high frequency component of the light quantity change is the largest (the spatial frequency is the highest) in the light quantity distribution.

[0003]

The optical path length from the taking lens of each image pickup device is the same, and the information obtained from these image pickup devices is common. Therefore, at the start of the automatic focus adjustment operation, it is unknown whether the taking lens is in front of or behind the in-focus position. Therefore, first, the photographing lens is moved in either the front-back direction to detect the change in the output signal of the image sensor, and the direction in which the photographing lens should be moved is determined based on the detection result. Therefore, conventionally, there has been a certain limit in speeding up the automatic focusing operation.

According to the present invention, when the automatic focusing operation is started,
The purpose is to detect the direction in which the taking lens should be moved, and thereby reduce the time required for automatic focus adjustment.

[0005]

According to the present invention, there is provided an automatic focusing apparatus for a still video camera, wherein a plurality of image pickup devices and at least one of these image pickup devices are moved to change an optical path length from a taking lens. According to the output signal of the element moving means, the focus state detecting means for detecting the focus state of the photographing lens based on the output signals of the plurality of image pickup devices in the state where the optical path length is changed, and the output signal of the focus state detecting means. And a lens moving unit for moving the photographing lens in the direction of the in-focus position.

[0006]

The present invention will be described below with reference to illustrated embodiments. FIG. 1 is a block diagram of a still video camera to which an embodiment of the present invention is applied.

The system control circuit 10 is a microcomputer and controls the entire still video camera.

The taking lens 11 is driven by a motor 12 to move along the optical axis X, and the motor 12 is driven by a motor drive circuit 13. The motor drive circuit 13 is controlled by the system control circuit 10, whereby the taking lens 11 is set at the in-focus position.

The light beam that has passed through the taking lens 11 is reflected by the beam splitters 15 and 16 of the prism 14 and guided to the first and second CCDs (image pickup devices) 21 and 22, respectively. These CCDs 21 and 22 are used for the photographing lens 11 except for AF (automatic focus adjustment) operation as described later.
The optical path lengths are equal to each other. Therefore, normally, the same image obtained through the taking lens 11 is formed on the first and second CCDs 21 and 22.

The first CCD 21 is always fixed at the same position. On the other hand, the second CCD 22 is normally fixed at the same optical path length position as the first CCD 21 as described above, but during the AF, the first CCD is moved by the CCD moving mechanism 30.
The optical path length is different from that of No. 21.

The first and second CCDs 21 and 22 are driven and controlled by a CCD drive circuit (not shown), and by this control, a signal corresponding to the image formed on the CCDs 21 and 22 is correlated double sampling (CDS) circuit 23, 24
Is supplied to. The image signals input to the CDSs 23 and 24 are subjected to predetermined processing such as removal of reset noise,
The signals are converted into digital signals in the A / D converters 25 and 26 and stored in the first and second memories 27 and 28.

2 to 4 show a first example of the CCD moving mechanism 30. 2 is a perspective view of the CCD moving mechanism 30, FIG. 3 is a view of the CCD moving mechanism 30 as seen from the front surface, that is, the direction of the taking lens 11, and FIG. 4 is a view of the CCD moving mechanism 30 as seen from above.

Connection members 31 and 32 having an L-shaped cross section are attached to the upper and lower portions of the CCD 22, respectively.
A guide member 33 is fixed to the upper surface of the connecting member 32, and a guide member 34 is fixed to the lower surface of the connecting member 32. Guide member 3
The arcuate guide holes 33a and 34a are provided in the reference numerals 3 and 34, respectively.
Are formed. The center of curvature of this arc coincides with the center C of the prism 14 as shown in FIG. 3, and is on the optical axis X of the taking lens 11.

The support plate 35 is connected to a camera body (not shown), and the support plate 35 has a pair of rods 36, 3 attached thereto.
7 is fixed. These rods 36 and 37 extend perpendicularly to the surface of the support plate 35, and guide holes 33a and 34a.
Has been inserted into. Therefore, the CCD 22 has a guide hole 3
Within the range in which the rods 3a and 34a move along the rods 36 and 37, that is, according to the arc shape of the guide holes 33a and 34a, it is possible to move up and down.

The upper portion 33b of the guide member 33 is bent in the horizontal direction, a spring 38 is provided between the upper portion 33b and the camera body, and the lower surface of the connecting member 32 is supported by the upper surface of the driving member 39. ing. CCD22
Is constantly urged downward by a spring 38, and the CCD
In general, the upper end portion of the guide holes 33a and 34a of the rod 22 is the rod 3
6 and 37, that is, in the lowered position (the position shown in FIG. 2 and the position shown by the broken line in FIG. 3).

The drive member 39 is composed of a piezoelectric element and expands and contracts by supplying and blocking voltage. The application of this voltage is performed by the control circuit 41, and the voltage is not normally applied to the driving member 39. In this state, the driving member 39
Is contracted and the CCD 22 is in the lowered position. On the other hand, when a voltage is applied to the driving member 39, the driving member 39 expands, so that the CCD 22 is set in the raised position against the spring 38. The control circuit 41 is controlled by the system control circuit 10.

An AF operation using the CCD moving mechanism 30 will be described with reference to FIGS. 3, 5 and 6. Second C
The CD 22 is rotatable in an arc shape around the center of curvature C of the guide holes 33a and 34a, and is in a state parallel to the exit surface 14a of the prism 14 except the AF, and the center C
The distance between the surface of the second CCD 22 and the second CCD 22 along the horizontal line H is “D (for example, 6 mm)”.
The distance from the center C along the horizontal line H, which is inclined with respect to a, is “D + d (d is, for example, 100 μm)”. That is, during AF, the optical path length of the second CCD 22 from the taking lens 11 is, for example, 100 μm longer than the optical path length of the first CCD 21.
It is set to be long, the first CCD 21 and the second CCD
At 22, both are not in focus at the same time.

At the time of AF, the light quantity of the light beam detected by the second CCD 22 and passing through the horizontal line H and the first CCD
The light amount by the light ray corresponding to the light ray detected by 22 and passing through the horizontal line H is compared. In FIG. 6, solid lines S1 and S2 indicate the first and second CCDs 21 and 2, respectively.
2 shows the input level of the light beam to 2, that is, the light amount distribution on one horizontal scanning line located on the horizontal line H.
As will be described later, the output signals from the first and second CCDs 21 and 22 are subjected to a predetermined fine product processing in the system control circuit 10 to extract the high frequency component of the image on each CCD, and to extract each by the photographing lens 11. An AF signal indicating the focused state of the image on the CCD can be obtained. The solid line S3 and the solid line S4 are respectively the first and second CCDs 21,
22 shows the AF signal obtained from No. 22. These AF
As can be seen from the signal comparison, in this example the second C
The peak value of the AF signal from the CD 22 is higher than the peak value of the AF signal from the first CCD 21 (the image on the second CCD 22 has higher contrast), and therefore the second CC
D22 is closer to the focal point. That is, in this state, since it can be understood that the focal point is behind the first CCD 21, the photographing lens 11 is driven and the focal point becomes the first CC.
It may be controlled so as to move in the direction of D21.

FIG. 7 is a flow chart of the AF operation.
The AF operation is started by pressing the shutter button halfway. In step 101, a voltage is applied to the driving member 39, and the second CCD 22 is rotationally moved to the raised position. In step 102, the output signals of the first and second CCDs 21 and 22 are A / D converted, and in step 103, these signals are read into the memories 27 and 28. This memory 2
The signals of all pixels output from the CCDs 21 and 22 are stored in 7 and 28, and in step 104, the pixel data of the horizontal scanning line corresponding to the position of the horizontal line H (FIG. 5) is read from the memories 27 and 28. . That is, the first CCD 2
For 1, the pixel data of, for example, the 250th horizontal scanning line from the upper end is read, and for the first CCD 22, for example, the pixel data of the 252nd horizontal scanning line is read. In this way, the pixel data on the lower side of the second CCD is read out because the second CCD is read during AF.
This is because 22 is rotationally displaced upward.

In step 105, the first and second CCs
The output signals of D21 and D22 are subjected to fine product processing to obtain the AF signal. That is, the output signals of the CCDs 21 and 22 indicated by the solid lines S1 and S2 in FIG.
After being differentiated, it is integrated by taking the absolute value,
An AF signal as shown by the solid lines S3 and S4 is obtained. The CCD having a large AF signal is relatively located near the focal point at the current position of the taking lens 11.

In step 106, the first and second CCs
The moving direction of the taking lens 11 is determined based on the AF signal obtained from D21 and D22. That is, the first CCD
When the AF signal obtained from 21 is larger, the distance between the taking lens 11 and the CCD 21 in the focused state is smaller than the distance between the taking lens 11 and the CCD 21 at this time, so the taking lens 11 approaches the prism 14. It should move in the direction (direction toward the CCD 21). On the other hand, when the AF signal obtained from the second CCD 22 is larger, the taking lens 11 and the CCD 2 in the focused state
The distances 1 and 22 are the taking lens 11 and the CCD at this time.
Since it is much larger than the distance from 21, the taking lens 11
Should move in a direction away from the prism 14 (a direction away from the CCD 21). The first CCD 21
The distance between the second CCD 22 and the second CCD 22 is extremely small, and is set to be substantially equal to the depth of focus of the taking lens 11.

In step 107, the taking lens 11
Starts moving in the direction determined in step 106. In step 108, the magnitude of the AF signal obtained from the first CCD 21 is compared with the AF signal obtained in the previous loop, and when the current AF signal is larger than the previous one, the process returns to step 102 and the above-described operation is repeated. The so-called mountain climbing control is executed. Step 108
When it is determined that the AF signal obtained from the first CCD 21 has the maximum value, the taking lens 11 is considered to be at the in-focus position, and in step 109, the taking lens 1
The movement of 1 stops. Then, in step 110, the second
The CCD 22 returns to the original position, that is, the position parallel to the exit surface 14a of the prism 14, to a position optically equivalent to the first CCD 21, and the AF operation ends.

FIG. 8 is a timing chart of the AF operation. When the shutter button is pressed halfway, the CCD moving pulse changes from the OFF state to the ON state, and the voltage is applied to the driving member 39 to extend it. That is, the second CCD 22
Moves and is set at a position inclined with respect to the exit surface 14a (FIG. 3) of the prism 14. In this state, distance measurement is performed based on the signals output from the first and second CCDs 21 and 22, and the photographing lens 11 is determined according to the distance measurement result.
Can be moved to the in-focus position. When the in-focus state is obtained in this way, the CCD moving pulse changes to the OFF state, and as a result, the second CCD 22 returns to the original position.

As described above, according to this embodiment, since the optical path lengths of the first and second CCDs 21 and 22 from the taking lens 11 are different, the distance measurement information obtained from these CCDs 21 and 22 is different. . Therefore, at the start of the AF operation, it is possible to easily determine whether the taking lens 11 is in front of or behind the in-focus position. That is, the taking lens 11 can be immediately moved toward the in-focus position, and the time required for the AF operation can be shortened.

In this embodiment, the focal point is the first C
The hill climbing control operation was performed so that it would be on the CD21.
The distance between the CCD 21 and the second CCD 22 is extremely short,
If it is within the depth of focus of the taking lens 11, step 1
In 08, each AF of the first CCD 21 and the second CCD 22
When the signals become equal, it may be considered as the in-focus position and the lens driving may be stopped.

9 to 11 show the second part of the CCD moving mechanism 30.
Is an example of. 9 is a perspective view of the CCD moving mechanism 30, FIG. 10 is a view of the CCD moving mechanism 30 as seen from the front surface, that is, the direction of the taking lens 11, and FIG. 11 is a view of the CCD moving mechanism 30 as seen from above.

A connecting member 3 provided above the CCD 22
A pivot member 51 is fixed to the pivot member 1, and a rod 52 provided perpendicularly to the support plate 35 is inserted into a hole 51a formed in the pivot member 51. Therefore, the CCD 22 can swing around the rod 52.

A connecting member 3 provided under the CCD 22
A spring 53 is provided between the camera body 2 and a camera body (not shown), and a pair of driving members 39 made of a piezoelectric element is provided below the prism 14. Connecting member 32
Is urged by the spring 53 and is always in contact with the drive member 39.

Normally, no voltage is applied to the driving member 39. In this state, the driving member 39 is contracted, and the CCD 22 is in a position parallel to the emission surface 14a of the prism 14. In contrast, when a voltage is applied to the drive member 39, the drive member 39 expands and thus CC
D22 is rotationally displaced against the spring 53, and is inclined with respect to the emission surface 14a.

Other configurations and operations are the same as the above-mentioned example.

12 to 14 show a third example of the CCD moving mechanism 30. FIG. 12 shows a CCD moving mechanism 30.
FIG. 13 is a view of the CCD moving mechanism 30 as seen from the front surface, that is, the direction of the taking lens 11, and FIG. 14 is a view of the CCD moving mechanism 30 as seen from above.

Guide members 61 and 62 are fixed to the connecting members 31 and 32 provided above and below the CCD 22, respectively. The guide members 61 and 62 are provided with linear guide holes 61a and 62a, respectively. Rods 63 and 64 provided perpendicularly to the support plate 35 are inserted into these guide holes 61a and 62a. Therefore C
The CD 22 is linearly displaceable along the guide holes 61a and 62a.

A spring (not shown) is provided between the connecting members 31 and 32 and the camera body, as in the example of FIG.
Further, on the rear surface of the CCD 22, that is, the surface on the prism 14 side, four driving members 39 each composed of a piezoelectric element are arranged. These drive members 39 are located at the corners of the CCD 22, and the CCD 22 is constantly urged by the spring 53 to be in contact with each drive member 39.

No voltage is normally applied to the driving member 39. In this state, the drive member 39 is contracted, and the CCD 22 is
Located relatively close together. On the other hand, the drive member 3
When a voltage is applied to 9, the drive member 39 expands and therefore the CCD 22 displaces against the spring 53,
It is relatively separated from the emission surface 14a.

Other configurations and operations are the same as those in the above-mentioned examples, and similar effects can be obtained by the examples in FIGS. 13 to 15.

The mechanism 3 for moving the second CCD 22
The configuration of 0 is not limited to the above example, and a conventionally known configuration may be adopted.

[0037]

As described above, according to the present invention, it is possible to detect the direction in which the photographing lens should be moved at the start of the automatic focus adjustment operation, and to shorten the time required for the automatic focus adjustment. can get.

[Brief description of drawings]

FIG. 1 is a block diagram of a still video camera to which an embodiment of the present invention is applied.

FIG. 2 is a perspective view showing a first example of a CCD moving mechanism.

FIG. 3 is a front view of the CCD moving mechanism shown in FIG.

FIG. 4 is a view of the CCD moving mechanism of FIG. 2 as viewed from above.

FIG. 5 is a diagram showing movement of a second CCD by a CCD moving mechanism.

FIG. 6 is a diagram showing light amounts and AF signals detected by first and second CCDs.

FIG. 7 is a flowchart of an AF operation.

FIG. 8 is a timing chart of an AF operation.

FIG. 9 is a perspective view showing a second example of the CCD moving mechanism.

10 is a front view of the CCD moving mechanism of FIG.

11 is a view of the CCD moving mechanism of FIG. 9 as seen from above.

FIG. 12 is a perspective view showing a third example of the CCD moving mechanism.

13 is a front view of the CCD moving mechanism of FIG.

FIG. 14 is a view of the CCD moving mechanism of FIG. 12 viewed from above.

[Explanation of symbols]

 11 taking lens 21, 22 CCD (imaging device) 30 CCD moving mechanism

Claims (1)

[Claims] 1. A plurality of image pickup devices, image pickup device moving means for moving at least one of these image pickup devices to change an optical path length from a photographing lens, and a plurality of image pickup devices in a state where the optical path length is changed. Focusing state detection means for detecting the focusing state of the photographing lens based on the output signal of the element,
An automatic focus adjusting apparatus for a still video camera, comprising: a lens moving unit that moves a photographing lens in a direction of a focus position according to an output signal of the focus state detecting unit.