JP2002350712A - Automatic focusing device and image pickup device provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic focusing device capable of highly accurately focusing by preventing malfunction due to a noise, in an image signal system automatic focusing device used for a video camera and an electronic still camera, etc. SOLUTION: A focal signal is detected by a focal signal detecting part 5 from the image signal which is formed by a camera image signal processing circuit 4 after being converted to an electrical signal by an imaging device 3. A focusing lens 1d with a focusing function is moved on the optical axis of a photographic lens 1 by a lens control part 6, and the focal position of the focusing lens 1d and N focal positions including the maximum value of the focal signal detected by the focal signal detecting part 5 in the focal position of the lens 1d are obtained, and then, the central value of N focal positions is regarded as the focal position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focusing apparatus for automatically focusing an image of a subject to be photographed to an optimum focal position when adjusting the focus of a video camera, a still camera, and the like, and the automatic focusing apparatus. The present invention relates to an imaging device including the device.

[0002]

2. Description of the Related Art As an automatic focusing device (autofocus) which is an important function in an image pickup device such as a video camera, several types of automatic focusing devices have already been proposed and implemented. One of the methods, which uses the level of the focus signal obtained from the in-focus state of the video signal of the video camera (hereinafter referred to as the video signal method), is described in, for example, "Automatic Focusing of Television Camera by Mountain Climbing Servo Method". Adjustment "(" NHK Technology Research "Vol. 17, No. 1, page 21, published in 1965 by Ishida et al.) In detail.
In Japanese Patent Application No. 63-248198, a part of a photographing lens is vibrated in the optical axis direction (hereinafter referred to as an auxiliary vibration operation) in this video signal system, and a high-frequency signal component of a video signal due to the auxiliary vibration operation is generated. A method is disclosed in which the direction of a hill-climbing operation in a video signal system is determined and stopped based on a modulation component of a focus signal obtained from a level to improve responsiveness.

FIG. 12 is a graph showing the peak-shaped fluctuation of a focus signal for explaining the operation of a conventional video signal type automatic focusing apparatus using an auxiliary vibration operation. FIG.
2, the horizontal axis indicates the position of the focus adjusting lens (hereinafter, referred to as a focus position), and the vertical axis indicates the level of the focus signal obtained from the high-frequency signal component of the video signal at the focus position. In FIG. 12, assuming that the automatic focusing operation is started from a focus position F1 on the side closer to the image sensor (hereinafter, referred to as the near side), shooting is performed in the focus direction in which the level of the focus signal increases due to the hill-climbing operation and the auxiliary vibration operation. Move the focus position of a part of the lens. That is, the focus position is moved in a direction farther from the image sensor (hereinafter, referred to as a far side). Then, it is determined that the passage of the focus signal vertex at the point where the level of the focus signal has decreased by a predetermined value beyond the vertex indicating the maximum value, that is, at the focus position F3. Thereafter, the moving direction of the photographing lens is reversed to the near side, and the lens is moved to a focus position F2 at which the maximum value of the focus signal is obtained.

[0004]

However, the level of the high-frequency signal component of the focus signal includes a change due to noise in addition to a change due to the in-focus state. Therefore, in the conventional method, when the fluctuation of the level of the high-frequency signal component is small, the focus position may be shifted due to the fluctuation due to noise. In such a case, the conventional automatic focusing apparatus cannot determine the correct direction or vertex position of the peak of the level change of the high-frequency signal component, or it takes time to determine the correct direction or vertex position. Therefore, there is a problem that a situation occurs in which the optical image obtained by the image sensor stops in a blurred state.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an automatic focusing device which does not shift the focus position even when a high-frequency signal component of a focus signal changes due to noise, and an image pickup device provided with the same.

[0006]

According to the present invention, there is provided an automatic focusing apparatus comprising: a photographing lens; an image pickup device for converting a light signal of a subject image obtained through the photographing lens into an electric signal; and an image output from the image pickup device. A camera video signal processing circuit that performs predetermined signal processing on the electric signal and outputs a video signal, based on the video signal generated by the camera video signal processing circuit,
A focus signal detecting means for calculating a focus signal corresponding to a focus state of the photographing lens; a focus adjusting lens which forms a part of the photographing lens and has a focus adjusting function is moved along an optical axis of the photographing lens; And a focus state of the subject image is detected based on a change in the focus signal output from the focus signal detection means. The focus state of the subject image is detected based on the detection result. Lens control means for instructing a focus position to drive the adjustment lens, wherein the lens control means includes a focus position within a predetermined moving range of the focus adjustment lens, and the focus signal at the focus position. Are obtained, N focus positions including the maximum value of the focus signal are obtained, and the center of the N focus positions is determined. Characterized by instructing the location as the focus position.

According to this configuration, the N focus positions including the maximum value of the focus signal at the focus position of the focus adjusting lens are obtained, and the center value of the N focus positions is set as the focus position. As a result, even when the level of the high-frequency signal component of the focus signal fluctuates due to noise and the number of peaks in the focus signal is large, the center value of the N focus positions is set as the focus position, and therefore the noise is prominent due to noise. There is no point at which the summit is in focus. Therefore, it is possible to provide an automatic focusing device capable of performing accurate automatic focusing with a small shift of the focusing position due to noise.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a video camera using a preferred automatic focusing device according to the present invention will be described below with reference to the accompanying drawings.

Embodiment 1 FIG. 1 is a block diagram showing a configuration of a video camera using the automatic focusing apparatus of Embodiment 1. In FIG. 1, a zoom lens 1 which is a photographing lens
Are four lens groups 1a, 1b, 1c, 1d (each of the lens groups is shown as one convex lens or one concave lens for the sake of simplicity of explanation, but actually, a plurality of convex lenses, Alternatively, it is composed of a concave lens.) The lens group of the zoom lens 1 includes:
A focus adjustment lens 1d having a focus adjustment function is included. The optical image of the subject 2 is formed by the zoom lens 1 on the imaging surface of the imaging device 3. The optical image of the subject 2 is converted into an electric signal by the image sensor 1 and sent to the camera video signal processing circuit 4. Camera video signal processing circuit 4
Performs various kinds of signal processing on an electric signal obtained from the image sensor 3 and outputs a predetermined video signal (for example, an NTSC signal) Co.

The focus signal detector 5 calculates a focus signal VF corresponding to the focus state of the focus adjustment lens 1d from the luminance signal Y output from the camera video signal processing circuit 4 at a field cycle and outputs the result. The lens control unit 6 stores and compares the output value of the focus signal detection unit 5 corresponding to the focus position, that is, the value of the focus signal VF, while moving the focus adjustment lens 1d by the lens driving unit 7. The lens controller 6 stores N (herein, five) values including the maximum value of the focus signal VF (hereinafter referred to as maximum five focus signal points) and the focus position at that time. Hold and indicate the focus position to be moved next.

The lens driving section 7 moves the focus adjusting lens 1d to the focus position specified by the lens control section 6. The lens control unit 6 updates and stores the N (here, five) values including the maximum value of the focus signal VF at the moved focus position and the focus position at that time, Next, a focus position to be moved is designated. By repeating this, the focus signal VF and its focus position are stored and updated, a comparison operation is performed, and the focus adjustment lens 1d is moved.
The center value of the N focus positions including the maximum value of F is set as the focus position and automatic focusing is performed.

FIG. 2 is a block diagram showing a detailed configuration of the focus signal detecting section 5. As shown in FIG. In FIG. 2, the focus signal detection unit 5 includes a band amplification circuit 8, a gate unit 9, a peak detector 10
have. The band amplification circuit 8 extracts a luminance signal Y of a frequency component (high-frequency component) having a predetermined value or more from the luminance signal Y output from the camera video signal processing circuit 4, amplifies the extracted signal, and converts the output signal C into an output signal C. Output. The gate unit 9 extracts, as a gate signal CG, an output signal C corresponding to a certain range in one field (photographing screen) period of the video camera. The peak detector 10 detects the maximum value of the level of the high frequency component of the gate signal CG in each field period, and outputs this maximum value as the focus signal VF for each field cycle.

FIG. 3 is a flowchart showing the operation of the automatic focusing apparatus according to the first embodiment. That is, FIG.
Shows a procedure of a focusing operation for finding a focus position based on a focus signal VF and a focus position obtained while moving the focus adjustment lens 1d. FIG. 4 is a flowchart showing details of the operation of updating the values of the maximum five focus signals and the focus position in step S5 of FIG. FIG.
6 is a graph showing a relationship between a focus position and a focus signal in the first embodiment. In FIG. 5, the focus positions are FP1 to FP11 in order from the side closer to the image sensor 3 in FIG. The values of the focus signals at the respective focus positions FP1 to FP11 are
F11. Hereinafter, the near side of the focus position is set as the origin, that is, FP1 <FP2 <... FP10 <FP
11 will be described.

The operation of the automatic focusing apparatus according to the first embodiment will be described below with reference to FIGS. 3, 4, and 5. In FIG. 3, when the automatic focusing device starts operation, first, in step S1, the focusing lens 1d of FIG. 1 is moved to one end of a predetermined moving range of the focusing position, for example, a near end (near end).
Move to. In FIG. 5, assuming that the focus position FP1 is the near end of the predetermined movement range, the focus position FP1 is first moved to the focus position FP1, and is moved away from the image pickup device 3 from the focus position FP1 (hereinafter, referred to as a far side). While moving the focus adjusting lens 1d, five focus positions are obtained in the order of larger focus signal. Further, the five pairs of the focus signal and the focus position are stored as focus data, and the addresses of the storage of the focus data are denoted by MAX1, MAX2,.
AX5, and focus data stored as a pair with these data are MAX1 (focus signal, focus position), MAX
2 (focus signal, focus position),..., MAX5 (focus signal, focus position).

Next, in step S2 of FIG. 3, the values of the maximum five focus signals and the focus positions thereof are initialized.
That is, the focus data stored in MAX1, MAX2,... MAX5 is initialized. At this point, since only the value at the focus position FP1 is set, MAX
VF1 as the focus signal of F1 and F as the focus position
P1 is inserted, MAX1 (VF1, FP1), MAX
The focus data values after 2 are MAX2 (0, 0),
... MAX5 (0, 0).

Next, in step S3 in FIG. 3, the lens moves to the next focus position, that is, the focus position FP2 in FIG. Then, in step S4 of FIG. 3, it is determined whether the current position is at the far end of the search range of the focal point.
As shown in FIG. 5, in this example, since the focus position FP11 is set at the far end, the determination is NO, and therefore, the process proceeds to step S5 to update the focus data stored with the values of the maximum five focus signals and the focus positions. I do.

The details of the procedure of updating the focus data of the focus position and the values of the maximum five focus signals in step S5 of FIG. 3 will be described below with reference to FIG. In FIG. 4, at step S50, the current focus signal V
It is compared whether F2 is greater than the focus signal VF1 stored in MAX1, and if the condition is satisfied, the current focus data is updated and stored in MAX1, because the current value is the maximum value of the focus signal. In this case, as shown in step S55, MAX4 is changed to MAX5, and MAX3 is changed to MAX4.
,..., MAX1 to MAX2, and so on, moving the stored values from the bottom in order, leaving MAX1 open, and then storing the current focus signal VF2 and focus position FP2 in MAX1, and performing the processing in step S5. finish.

If the condition in step S50 is not satisfied, the process proceeds to step S51. If the condition is determined and satisfied, in step S56, MAX2 to MAX4 are set to M.
After shifting sequentially to AX3 to MAX5, the current focus data value is input to MAX2, and the step S5 ends. When the condition determination in step S51 is not satisfied, the process proceeds to step S52, and thereafter, in step S52, step S52.
53 and step S54. If the conditions are satisfied, the process proceeds to step S5.
7. As in steps S58 and S59, the value of the focus data after the corresponding address is shifted and the current value of the focus data is stored in the corresponding address, and step S5 ends.

When the processing in step S5 is completed in this way, the focus data stored in the focus signal values of up to five focus signals and their focus positions is updated. That is, at the current focus position FP2, the value of the focus data is MAX1 (VF2, FP2).
2), MAX2 (VF1, FP1), MAX3 (0,
0), MAX4 (0, 0) and MAX5 (0, 0).

Then, returning to step S3 in FIG. 3, the focus adjusting lens 1 in FIG.
Move d. Thus, steps S3 to S
The process of No. 5 is moved to the far end of the focus range search range, that is, the focus position FP11, and is repeated until the condition determination of step S4 is satisfied. When the position of the focusing lens 1d in FIG. 1 reaches the focus position FP11,
In step S6, the focus data stored with the focus signals of up to five focus signals and the focus positions is updated.

When the change of the focus signal in this focusing range is a mountain shape as shown in FIG. 5, the value of the focus signal is VF6 at maximum, and becomes VF7, VF5, VF8, and VF4.
Therefore, the value of the focus signal at the maximum of five focus signals and the focus data of the focus position are MAX1 (VF6,
FP6), MAX2 (VF7, FP7), MAX3 (V
F5, FP5), MAX4 (VF8, FP8), MAX
5 (VF4, FP4). When these five focus positions are arranged in order from the far side, FP8, FP7, FP6,
FP5 and FP4, and the median is FP6. Then, in step S7 in FIG. 3, the center value FP6 of the five focus positions is set as the focus position, and the focus adjustment lens 1d in FIG. 1 is moved to that position, thereby ending the automatic focusing operation.

When the fluctuation of the focus signal is a mountain shape having a single peak as shown in FIG. 5, the focusing operation can be accurately performed even by a conventional automatic focusing apparatus in which the focus signal has a maximum point. Can be implemented. However, various noises such as noise included in the video signal, movement of the subject, change in illuminance, and camera shake of the photographer are superimposed on the actual focus signal. The influence of noise is more susceptible to the gradual change of the focus signal due to the original focus position.

The focusing operation of the automatic focusing apparatus according to the first embodiment in the case where the fluctuation of the focus signal fluctuates in a sawtooth shape with noise superimposed thereon as shown in FIG. 6 will be described. FIG.
In this case, the peak of the fluctuation of the original focus signal is gentle, and the sawtooth-like noise is superimposed. In particular, a large noise is superimposed on the focus signal VF4 at the focus position FP4. Therefore, the value of the focus signal VF4 at the focus position FP4 is the maximum value. In the case of the fluctuation of the focus signal as shown in FIG. 6, in the conventional automatic focusing device, the focus is set to the focus position FP4 where the focus signal is the maximum. Therefore, the focus is shifted to a position shifted from the focus position FP6 having a high probability of being a correct focus position.

In the automatic focusing apparatus according to the first embodiment, as described above, the focus position FP1 is shifted to the focus position FP1.
The focus adjusting lens is moved to 1 to update the values of the maximum five focus signals and the focus data of the focus position. As a result, the values of the focus signal VF become VF4, VF6, VF7, VF5, and VF9 in order from the maximum value. Therefore, the stored values of the maximum five focus signals and the focus data of the focus position are MAX1 (VF4,
FP4), MAX2 (VF6, FP6), MAX3 (V
F7, FP7), MAX4 (VF5, FP5), MAX
5 (VF9, FP9). Therefore, if the focus positions are arranged in descending order of the value of the focus signal, FP9, FP
7, FP6, FP5, and FP4, the center focus position is FP6, and the focus position FP6 can be set as the focus position. In a mountain-like variation in which noise is superimposed on the focus signal as shown in FIG. 6, the focus signal value VF4 protrudes by one point, and the possibility of noise is high, and the focus position FP6 is the correct focus position. High probability.

In the operation of the automatic focusing apparatus according to the first embodiment, the focus adjusting lens 1d shown in FIG. 1 is moved and searched in the focusing range from the near end to the far end, and then the maximum value of the focus signal is 5 points. It has been described that the center value of the focus position of the value of is the focus position. However, the focus position near the center value of the focus position is set as the refocusing range, and the focus adjustment lens 1 shown in FIG.
Move d. In this manner, by detecting the values of the five focus signals near the center value of the focus position and determining the center point of the focus position as the focus position, a more accurate focus position can be obtained.

As described above, the predetermined moving range is searched, and the focus position of the focus adjusting lens 1d shown in FIG.
The focus signal at that position is extracted, N focus positions including the maximum value of the focus signal are obtained, and the median of the N focus positions is set as the focus position. By providing the lens control unit 6 of FIG. 1 that performs such a focusing operation, the automatic focusing device of the first embodiment can perform accurate automatic focusing with a small shift of the focusing position due to noise.

Embodiment 2 FIG. 7 is a flowchart showing a procedure of a focusing operation of the automatic focusing apparatus according to the second embodiment.
The configuration of the automatic focusing apparatus according to the second embodiment is the same as that of the first embodiment, and only the focusing operation is different. Therefore, the components will be described with reference to FIG. FIG. 8 is a graph showing the relationship between the focus position and the focus signal in the second embodiment. 8, the focus positions are FP1 to FP11 in order from the near side, and the focus signal levels at the respective focus positions are VF1 to VF11, respectively.

In step S71 of FIG. 7, the automatic focusing operation is started. The activation is performed when power is supplied to the automatic focusing apparatus according to the second embodiment, when an instruction to start automatic focusing is input, and when the automatic focusing operation is completed, the movement or imaging of the subject is completed. This is the case where panning of the device occurs and the automatic focusing device needs to be restarted. As a method of judging the restart, a method of detecting a sudden change in the focus signal, and a method of detecting a change in the level of the modulation component of the focus signal due to the auxiliary vibration operation disclosed in Japanese Patent Application No. 63-248198. and so on.

In step S72 of FIG. 7, the direction of the hill-climbing of the focusing operation is determined. As a method of determining the direction of the hill-climbing, a method of moving the focusing lens 1d in FIG. 1 in one direction to detect whether the level of the focus signal rises or falls, and set the rising direction as the hill-climbing direction, Japanese Patent Application No. 63-2
No. 48198 discloses a method of detecting a direction based on a modulation component of a focus signal by an auxiliary vibration operation.
In step S73, the focusing lens 1d of FIG.
In the direction determined in step S72 to start mountain climbing. Then, in step S74, the focus data to be stored is initialized.

After moving to the next focus position in step S75, it is determined in step S76 whether or not the focus signal has passed the peak of the fluctuation. As a method of determining whether or not the vehicle has passed the peak, whether the focus signal has decreased by a predetermined level or more from the maximum value, has decreased one or more times from the maximum value of the focus signal, or has continuously decreased the focus signal multiple times There is a method of determining whether the direction of the modulation component due to the auxiliary vibration operation has changed.

In the operation of the automatic focusing apparatus according to the second embodiment, the hill climbing is started in step S73 in FIG. 7, and steps S75 to S77 are sequentially and repeatedly performed.
The in-focus range is from when it is determined that the vehicle has passed the peak at 76 and the process branches to step S78. In the meantime, similarly to the operation of the automatic focusing apparatus according to the first embodiment, the focusing lens 1 shown in FIG.
The focus position of d and the focus signal at the position are extracted, the focus positions of the N focus adjustment lenses 1d including the maximum value of the focus signal are obtained, and the median of the N focus positions is determined as the focus position. And

Hereinafter, the focusing operation of the automatic focusing apparatus according to the second embodiment will be described with reference to FIG.
As shown by the broken line in FIG. 8, if the focusing operation is started from the position of the focus position FP2, since the far side is the direction in which the level of the focus signal increases, it moves in the far direction to reach the peak of the level of the focus signal. After passing through, the focus signal moves until the level of the focus signal drops by a predetermined value (α) from the maximum value. That is, the focus adjustment lens 1d of FIG. 1 is moved to the focus position FP10 to search for the focus position.

The focus adjusting lens 1d of FIG. 1 from the focus position FP2 at which the hill climbing is started to the focus position FP10 at which it is determined in step S78 that the hill has been passed.
Step S75 to Step S77 during the moving range of
Is repeated. In each case, in step S77 in FIG. 7, the focus data stored with the values of the maximum three focus signals and the focus position is updated.

If the level of the focus signal changes as shown in FIG. 8, the values of up to three focus signals at the focus position FP10 determined to have passed the peak in step S78 and the focus data at the focus position are as follows: MAX
1 (VF8, FP8), MAX2 (VF9, FP9),
MAX3 (VF7, FP7). When these three focus positions are arranged in order from the far side, FP9, FP8, FP
7 and the median is FP8. Then, in step S79 in FIG. 7, the focus adjustment lens 1d in FIG. 1 is moved to the focus position FP8, and a series of automatic focusing operations is completed.

Embodiment 3 FIG. 9 is a flowchart showing a procedure of a focusing operation of the automatic focusing apparatus according to the third embodiment.
The configuration of the automatic focusing device according to the third embodiment is the same as that of the second embodiment, and only the focusing operation is different. Therefore, the same steps as those in the second embodiment are denoted by the same reference numerals, and the components will be described with reference to FIG. FIG. 10 is a graph showing the relationship between the focus position and the focus signal in the third embodiment. In FIG. 10, the focus position is set to F in order from the near side.
P1 to FP11, and the focus signal levels at the respective focus positions are VF1 to VF11, respectively. As shown in FIG. 9, in the focusing operation of the third embodiment, as a method of determining whether or not the camera has passed the mountain in step S80, the current focus position is set to the maximum of N focus positions of the focus signal up to that point. A method is used in which it is determined whether the vehicle has passed a predetermined distance β or more from the median. Hereinafter, description will be made assuming that N is 3, and β is, for example, 0.02 mm.

In FIG. 10, the focusing lens 1 shown in FIG.
When d is started from the focus position FP2 and moved so as to climb a mountain in the far direction, a maximum of three central focus positions up to that point at each focus position are shown as center positions. And at each focus position,
The difference between the center position and the current position up to that point is shown as the difference between the current position and the center position. That is, the condition of step S80 in FIG. 9 is satisfied when the focus adjustment lens 1d in FIG. 1 is moved to the focus position FP10 in FIG. The three focus positions (N = 3) at that time are FP8, FP9, and FP10. The focus position FP10 is apart from the focus position FP8 indicating the maximum value of the focus signal VF by 0.02 mm in the far direction. Thus, it was determined at the focus position FP10 that the vehicle passed the mountain. At this time, the maximum focus position of the focus signal is FP8.
Will be the focal point.

As described with reference to FIG. 6 in the first embodiment,
Various noises such as noise included in the video signal, movement of the subject, change in illuminance, and camera shake of the photographer are superimposed on the actual focus signal. The influence of the noise is more susceptible as the peak of the fluctuation of the original focus signal becomes gentler.

For example, as shown in FIG. 11, the focusing operation of the automatic focusing apparatus according to the third embodiment in the case where noise is superimposed on the focus signal and the focus signal fluctuates in a saw-tooth shape will be described. FIG. 11 shows a change state of the focus signal in a case where the peak of the change of the original focus signal is gentle and the sawtooth noise is superimposed. In particular, in FIG. 11, the focus position FP
4, a large noise is superimposed on the focus signal VF4.

In the conventional automatic focusing device, when the focusing operation is started from the focus position FP2 and the hill is climbed in the far direction, the focus signal VF5 at the next focus position FP5 is smaller than the focus signal VF4 at the focus position FP4. The direction of climbing is reversed because it is falling. Next, focus position F
At P4, if noise is also superimposed, the focus signal VF
Since 4 is the maximum value, the focus position FP4 is set as the focus position. If the noise is not superimposed when the hill-climbing direction is reversed and comes again to the focus position PF4, the focus signal at that position is smaller than the focus signal at the focus position FP5, so that the focus position FP4 is set as the focus position. Never. However, in this case, the focusing operation causes a series of unstable movements of reversing once more and moving in the far direction.

However, in the third embodiment, when the focusing operation is started from the focus position FP2 and the hill is climbed in the far direction as indicated by the broken line, a maximum of three central positions and the current position up to the point of the focus position FP5 are obtained. Is 1, which is smaller than the predetermined value β of 2, so that there is no erroneous inversion. The focus adjustment lens 1d of FIG.
When it reaches 11, the difference between the center position and the current position becomes 2 for the first time, and is equal to or more than the predetermined value β, so that the focus position FP9 is inverted to be the focus position as shown by the upper broken line. Can be.

[0041]

As described above in detail in the embodiments,
The automatic focusing device of the present invention has the following effects. That is, the focus position of the focus adjustment lens and the focus signal at that position are extracted, and N focus positions including the focus position indicating the maximum value of the focus signal are obtained, and the median value of the N focus positions is obtained. Is the in-focus position. Therefore, even when the focus signal is maximized at a position other than the focus position due to the superposition of noise, the focus position can be accurately obtained except for a discontinuous change in the focus signal.

As a result, the focus can be accurately adjusted by matching the focus position of the focusing lens with the focus position. By applying this automatic focusing device to an electronic still camera or a video camera, accurate automatic focusing with few malfunctions due to noise can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an automatic focusing apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a focus signal detection unit of the automatic focusing apparatus according to the first embodiment of the present invention.

FIG. 3 is a flowchart illustrating the operation of the automatic focusing apparatus according to the first embodiment.

FIG. 4 is a flowchart showing an operation of updating the values of up to five focus signals and the focus position in step S5 in the operation of the automatic focusing apparatus according to the first embodiment;

FIG. 5 is a graph showing a relationship between a focus position and a focus signal in the automatic focusing apparatus according to the first embodiment.

FIG. 6 is a graph showing a relationship between a focus position and a focus signal on which noise is superimposed in the automatic focusing apparatus according to the first embodiment.

FIG. 7 is a flowchart illustrating the operation of the automatic focusing apparatus according to the second embodiment.

FIG. 8 is a graph showing a relationship between a focus position and a focus signal in the automatic focusing apparatus according to the second embodiment.

FIG. 9 is a flowchart illustrating the operation of the automatic focusing apparatus according to the third embodiment.

FIG. 10 is a graph illustrating a relationship between a focus position and a focus signal in the automatic focusing apparatus according to the third embodiment.

FIG. 11 is a graph illustrating a relationship between a focus position and a focus signal on which noise is superimposed in the automatic focusing apparatus according to the third embodiment.

FIG. 12 is a graph showing a relationship between a focus position and a focus signal in a conventional automatic focusing device.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 photographing lens 1a, 1b, 1c lens group 1d focus adjusting lens 2 subject 3 image pickup device 4 camera video signal processing circuit 5 focus signal detection unit 6 lens control unit 7 lens driving unit 8 band amplification circuit 9 gate unit 10 peak detector S1 to S7, S50 to S60, S71 to S80 Step

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/232 G03B 3/00 A F term (Reference) 2H011 AA03 BA31 BB04 CA19 CA21 2H044 DA01 DC02 DE06 2H051 AA08 BA47 CE08 CE14 CE16 DA18 DA26 FA48 FA76 5C022 AA11 AA13 AB28 AB29 AB44 AC74

Claims (5)

[Claims] An imaging device for converting an optical signal of a subject image obtained through the imaging lens into an electric signal; performing a predetermined signal processing on the electric signal output from the imaging device to output a video signal A camera video signal processing circuit, a focus signal detection unit that calculates a focus signal corresponding to a focus state of the shooting lens based on the video signal generated by the camera video signal processing circuit, and a part of the shooting lens. A focus adjustment lens having a focus adjustment function is moved along the optical axis of the photographing lens to perform focus adjustment; and a lens drive unit configured to perform focus adjustment, and a change in the focus signal output from the focus signal detection unit. The focus state of the subject image is detected, and the focus adjusting lens should be driven with respect to the lens driving unit based on the detection result. A lens control unit that instructs a focus position, wherein the lens control unit positions the focus adjustment lens within a predetermined movement range of the focus adjustment lens (hereinafter, referred to as a focus position), and the focus thereof. Extracting the focus signal at a position, obtaining N focus positions including the maximum value of the focus signal, and designating a center position of the N focus positions as the focus position. Focusing device. 2. The method according to claim 1, wherein the lens control unit adjusts a focus position (hereinafter, referred to as a focusing operation).
Starting position judging means for judging the starting position of the focus signal; moving direction judging means for judging the moving direction of the focus adjusting lens in which the level of the focus signal rises; and a focus position (hereinafter referred to as focus) where the focus signal becomes maximum. A maximum value passage determining means for determining that the signal has passed the peak of the signal, from the position activated based on the determination of the activation position determining means to the point of passing the peak of the focus signal. 2. The automatic focusing apparatus according to claim 1, wherein the in-focus position is obtained in a range of movement of the focus position. 3. The lens control means extracts the focus position and the focus signal at the focus position, and performs a focusing operation while obtaining N focus positions including the maximum value of the focus signal level. 3. The automatic focusing device according to claim 2, wherein the passage of the focus signal through a peak is determined based on a distance between a current focus position and a median of the N focus positions. 4. The automatic focusing apparatus according to claim 1, wherein said N is in a range of 3 to 9. 5. An image pickup apparatus comprising the automatic focusing device according to claim 1. Description: