JP2003032521A - Camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a camera that stops sequential display of through-images when a focus evaluation value is decreased more than a prescribed value and executes sequential display of through-images when the focus evaluation value is increased more than the prescribed value. SOLUTION: The AF digital camera includes an imaging lens 1, a solid-state imaging device 2, an analog signal processing circuit 3, an analog/digital converter 4, a digital signal processing circuit 5, a memory 6, a digital/analog converter 7, a liquid crystal display monitor 8, a compression/uncompression circuit 9, an external storage means 10, a control circuit 12, a motor 16, a focus control mechanism 17, and a CPU 19. When the focus evaluation value is decreased and reaches a value lower than the prescribed value, the CPU 19 throws only a switch SW1 (Figure 3) in the memory 6 to a position of other buffer. When the focus evaluation value is increased and reaches a value higher than the prescribed value, the CPU 19 throws the switch SW1 (Figure 3) and a switch SW2 (Figure 3) in the memory 6 to a position of the other buffer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an autofocus camera equipped with a monitor display device.

[0002]

2. Description of the Related Art There is known a focus detecting device for a camera which picks up an image of a subject using an image pickup device such as a CCD and detects an adjustment state of a focus position by a photographing lens based on an image pickup signal output from the image pickup device. There is. Among them, the focus detection method called the hill climbing method is the data of the high frequency component of the frequency of the image pickup signal while moving the photographing lens back and forth with respect to the focus position, that is, the focus position is set so as to maximize the focus evaluation value. To detect. Using this method, the in-focus position is detected from the image pickup signals corresponding to the multiple focus detection areas prepared in advance in the image pickup area, and the detection position that is the closest to the camera among the plurality of detection results is detected. There is a focus detection algorithm in which is the in-focus position of the camera. Since the subject closest to the camera is likely to be the main subject, if the photographing lens is driven to the in-focus position indicating the closest subject, the probability of focusing on the main subject increases.

[0003]

However, in the autofocus camera which performs focus detection by the above-mentioned algorithm, it is necessary to always search for the closest subject. Therefore, even when the taking lens is in focus, the taking lens is once moved from the in-focus position, and a focus position that maximizes the focus evaluation value is searched for in another focus detection area in the imaging area. At this time, if an image based on the image pickup signal output from the image pickup device is displayed on the monitor display device of the camera, the image out of focus is displayed on the monitor by moving the taking lens from the in-focus position. People who are looking at the display device will feel uncomfortable. In particular, when the focus evaluation value changes greatly, such as when the camera is panned or the subject moves, this is likely to cause a problem.

It is an object of the present invention to provide a camera that prohibits updating of an image displayed on the display device of the camera according to a focus evaluation value indicating the focus state of the taking lens.

[0005]

FIG. 1 showing an embodiment.
The present invention will be described in association with. (1) A camera according to a first aspect of the present invention is an image pickup device 2 for picking up a subject image through a taking lens 1, and an evaluation value calculation circuit for calculating a focus evaluation value using an image pickup signal output from the image pickup device 2. 19, a drive signal output circuit 19 for outputting a drive signal for driving the photographing lens 1 to a focus position so as to maximize the focus evaluation value calculated by the evaluation value calculation circuit 19, and different time points depending on the image sensor 2. According to the focus evaluation value calculated by the storage circuit 6 for storing the image pickup signals picked up in
By providing the read circuit 19 for reading the image pickup signal at the old time stored in the storage circuit 6 and the display device 8 for sequentially updating and displaying the image generated from the image pickup signal read by the read circuit 19, Achieve the purpose. (2) The invention according to claim 2 includes an image pickup device 2 for picking up a subject image through the taking lens 1, and an evaluation value calculation circuit 19 for calculating a focus evaluation value using an image pickup signal output from the image pickup device 2. A drive signal output circuit 19 that outputs a drive signal for driving the taking lens 1 to the in-focus position so that the focus evaluation value calculated by the evaluation value calculation circuit 19 is maximized.
A storage circuit 6 for storing image pickup signals picked up by the image pickup element 2 at different times, and an evaluation value calculation circuit 1
In accordance with the focus evaluation value calculated by 9, the reading circuit 19 that reads the old-time image pickup signal stored in the storage circuit 6, and the image generated from the image pickup signal read by the reading circuit 19 are sequentially updated. The above-described object is achieved by including the display device 8 for displaying. (3) The invention according to claim 3 is the camera according to claim 2, wherein the readout circuit 19 reads out the image pickup signal at an old time point from the storage circuit 6 when the focus evaluation value is equal to or less than a predetermined value. Characterize. (4) The invention according to claim 4 is the camera according to claim 2, wherein the readout circuit 19 reads out the image pickup signal at an old time point from the storage circuit 6 when the focus evaluation value decreases with time. It is characterized by (5) A camera according to a fifth aspect of the present invention is an evaluation value calculation circuit for calculating a focus evaluation value using an image pickup device 2 for picking up a subject image through the taking lens 1 and an image pickup signal output from the image pickup device 2. 19, a drive signal output circuit 19 for outputting a drive signal for driving the photographing lens 1 to the in-focus position so as to maximize the focus evaluation value calculated by the evaluation value calculation circuit 19, and is output from the image pickup element 2. A memory circuit 6 for sequentially storing the image pickup signals to be stored in different memory areas, and a memory circuit 6
And a read circuit 19 for reading the image pickup signal stored in the time series, and a read circuit 19 for prohibiting the read circuit 19 from reading a new image pickup signal according to the focus evaluation value calculated by the evaluation value calculation circuit 19. The above-described object is achieved by including the control circuit 19 and the display device 8 that sequentially updates and displays the image generated from the image pickup signal read by the reading circuit 19. (6) The invention according to claim 6 is characterized in that, in the camera according to claim 5, the read control circuit 19 prohibits reading of a new image pickup signal when the focus evaluation value is equal to or less than a predetermined value. To do. (7) The invention according to claim 7 is the camera according to claim 5, wherein the readout control circuit 19 prohibits the readout of a new image pickup signal when the focus evaluation value decreases with time. Characterize. (8) The invention according to claim 8 is the camera according to claim 6 or 7, wherein the taking lens 1 is a zoom lens, and a zoom operation signal for changing an angle of view of the taking zoom lens 1 is detected. The read control circuit 19 is further characterized in that the read control circuit 19 prohibits the reading of a new image pickup signal when the operation signal detection circuit 19 detects the operation signal.

In the section of means for solving the above-mentioned problems, the present invention is limited to the embodiments although it is associated with the drawings of the embodiments in order to explain the present invention in an easy-to-understand manner. is not.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an AF (autofocus) digital camera according to an embodiment of the present invention. In FIG. 1, the digital camera includes a taking lens 1, a solid-state image sensor 2, an analog signal processing circuit 3, an A / D converter 4, and a digital signal processing circuit 5.
, A memory 6, a D / A converter 7, a liquid crystal monitor 8,
It has a compression / decompression circuit 9, an AE / AWB processing circuit 11, a control circuit 12, a bandpass filter 13, an integration circuit 14, an AF calculation circuit 15, a motor 16, and a focus control mechanism 17. Of these, AE
The / AWB processing circuit 11, the bandpass filter 13, the integrating circuit 14, and the AF calculation circuit 15 are configured in the CPU 19. The external storage medium 10 is attached to and detached from the digital camera.

The taking lens 1 has a focus lens (not shown) for adjusting the focal position so that the subject image passing through the lens is formed on the image pickup surface of the solid-state image pickup device 2 and the focal length of the taking lens 1. And a zoom lens (not shown) to be changed. The solid-state image sensor 2 is, for example, a CCD, and accumulates a signal charge for each pixel according to the intensity of light of a subject image formed on the imaging surface. A timing signal is supplied from the control circuit 12 to the solid-state image sensor 2. The signal charge accumulated in the solid-state image pickup device 2 is swept out by the timing signal and sent to the analog signal processing circuit 3 as an image pickup signal. The solid-state image sensor 2 may use a MOS sensor or a CID instead of the CCD.

The analog signal processing circuit 3 has a CDS clamp circuit, a gain adjusting circuit, etc., and performs analog processing such as noise removal and gain control on the image pickup signal output from the solid-state image pickup device 2. , A /
Output to the D converter 4. The A / D converter 4 converts an analog signal into a digital signal and outputs the converted image data to the digital signal processing circuit 5.

The digital signal processing circuit 5 includes signal processing circuits such as a gain control circuit, an AE integration circuit, a luminance signal generation circuit, and a color difference signal generation circuit. The digital signal processing circuit 5 performs image processing such as contour compensation and gamma correction on the image data after digital conversion. The image data subjected to the image processing is once stored in the memory 6, then read from the memory 6 and sent to the compression / decompression circuit 9. The compression / decompression circuit 9 compresses the image data captured by the solid-state image sensor 2 after the release operation of the AF digital camera and stored in the memory 6 in a predetermined compression format (for example, JPEG system) to compress a CF memory card or the like. In the external storage medium 10. Compression / decompression circuit 9
The data compression rate at the time of compression is appropriately selected from 1/4 compression, 1/8 compression, 1/16 compression, and the like. The compression / decompression circuit 9 also performs a decompression process for reading and decompressing the data compressed and recorded in the external storage medium 10.

On the other hand, the image data once stored in the memory 6 is read from the memory 6 and sent to the D / A converter 7. The D / A converter 7 converts the digital image data into an analog video signal, and outputs the converted analog signal to the liquid crystal monitor 8. The liquid crystal monitor 8 displays an image based on a video signal. As a result, the subject image captured by the solid-state image sensor 2 is displayed on the liquid crystal monitor 8. The subject image displayed on the liquid crystal monitor 8 includes a through image that sequentially updates and displays the subject image repeatedly captured by the solid-state image sensor 2 before the release operation of the AF digital camera, and a solid image after the release operation of the AF digital camera. There is a freeze image in which a subject image captured by the image sensor 2 is displayed for a predetermined time.

When the data recorded in the external storage medium 10 is expanded by the compression / decompression circuit 9 and stored in the memory 6, the D / A converter 7 outputs the image data after the expansion processing from the memory 6. Read out and convert to analog video signal. As a result, the external storage medium 10 is displayed on the liquid crystal monitor 8.
An image based on the compressed data recorded in is displayed.

The control circuit 12 includes a solid-state image sensor 2
In addition to generating and transmitting the timing signal, the control signal for the analog signal processing circuit 3 is transmitted. CPU19
Is connected to the control circuit 12, the digital signal processing circuit 5, the memory 6, etc., and is used for focus detection (AF), photometry (AE), white balance adjustment (AW) of the digital camera.
Various calculations such as B) and sequence control of camera operation are performed. Various operation signals are input to the CPU 19 from a release switch (not shown) or the like.

The focus detection processing performed by the above-mentioned digital camera will be described. The image pickup signal output corresponding to each pixel of the solid-state image pickup device 2 has a different signal level according to the intensity of light incident on each pixel. CPU19
Of the image data output from the solid-state image sensor 2 and subjected to the above-described signal processing and stored in the memory 6
The focus detection data is read by designating a predetermined address where the data is stored. A high-frequency component is extracted from the focus detection data read from the memory 6, and a focus evaluation value is calculated. Specifically, the focus detection data is passed through a bandpass filter 13 to extract a desired frequency component of the image data, and the integration circuit 14 integrates the absolute values of the extracted signals to obtain a focus evaluation value. .

FIG. 2 is a diagram showing an example of the relationship between the position of a focus lens (not shown) in the taking lens 1 and the focus evaluation value. In FIG. 2, the horizontal axis is the position of the focus lens, and the vertical axis is the focus evaluation value. The lens position P that maximizes the focus evaluation value is the focus position of the focus lens.

The AF calculation circuit 15 focuses so as to maximize the calculated focus evaluation value, that is, to maximize the contrast by eliminating the blurring of the edge of the subject image captured by the solid-state image sensor 2. The lens drive signal is output to the motor 16. When the motor 16 rotates, the focus control mechanism 17 moves the focus lens forward and backward in the optical axis direction. The AF calculation circuit 15 drives the focus lens in the infinity direction in FIG. 2 to drive the focus lens in the ∞ direction when the focus evaluation value decreases. Further, the AF calculation circuit 15 drives the focus lens in the infinity direction when the focus evaluation value decreases by driving the focus lens in the ∞ direction. That is, the focus lens is alternately driven in the close-up direction and the ∞ direction with the position (focus position P) at which the focus evaluation value is maximized.

The focus detection processing by the focus detection device of the autofocus camera described above is called a hill climbing method. In the hill-climbing focus detection process, when the autofocus camera is set to the continuous autofocus mode in which the focus detection process is always performed, the focus evaluation value is obtained from the image data repeatedly captured by the solid-state image sensor 2. The focus lens is constantly driven according to the result of the calculation. When the AF digital camera is displaying a through image on the liquid crystal monitor 8, when the focus lens is driven, the focus state of the through images sequentially displayed changes.

The present invention is characterized by the operation when the AF digital camera displays a through image on the liquid crystal monitor 8 and is set to the continuous autofocus mode. Specifically, when the AF digital camera is panned or the subject moves, the sequential updating of the subject image displayed on the liquid crystal monitor 8 is stopped according to the state of change in the calculated focus evaluation value.

A buffer area provided in the memory 6 for displaying a through image will be described with reference to FIG. In FIG. 3, the buffer area includes four storage area buffers A to D and a switch SW1.
And a switch SW2. The buffers A to D respectively store at least one frame of image data. The switch SW1 is a digital signal processing unit 5
Image data input from the
The input is switched to any one of the above. Further, the switch SW2 is switched to selectively output the image data stored in the buffers A to D to the D / A converter 7. The switches SW1 and SW2 are shown for the sake of convenience, and are actually switched by the address designated by the CPU 19.

When the calculated focus evaluation value is larger than a predetermined threshold value, the CPU 19 alternately switches the buffer A and the buffer B. That is, the CPU 19
When the solid-state image sensor 2 outputs an image signal for one frame, the solid-state image sensor 2 stores the image data of the image signal in the storage area of the buffer A, and the solid-state image sensor 2 outputs an image signal for the next one frame. Then, the image data based on the image signal is stored in the storage area of the buffer B.
When the image signal for the next one frame is further output by the solid-state image sensor 2, the CPU 19 overwrites and stores the image data of the image signal in the storage area of the buffer A. In this way, the CPU 19 switches the switch SW1 in synchronization with the vertical synchronization signal input to the solid-state image sensor 2, that is, the signal indicating the timing for each frame.

On the other hand, the CPU 19 switches the switch SW2 in synchronization with the vertical synchronizing signal to alternately read out the image data stored in the buffer A and the image data stored in the buffer B. As a result, the image data stored in the buffer A or the buffer B is sequentially read in time series from the previously stored image data. The read image data is sent to the D / A converter 7. As a result, the subject image repeatedly captured by the solid-state image sensor 2 is sequentially updated and displayed on the liquid crystal monitor 8.

The processing performed by the CPU 19 when the focus evaluation value changes will be described with reference to the flowchart of FIG. The process of FIG. 4 is repeated in synchronization with the vertical synchronizing signal when the AF digital camera displays a through image on the liquid crystal monitor 8 and is set to the continuous autofocus mode. Step # 20
In 1, the CPU 19 determines whether the focus evaluation value has decreased. When the focus evaluation value calculated is decreased, for example, when the focus lens (not shown) is driven closer to the focus position P in FIG.
If the affirmative determination is made in step 201, the process proceeds to step # 202, and if the calculated focus evaluation value has not decreased, step # 20
When 1 is negatively determined, the process proceeds to step # 206.

In step # 202, the CPU 19
Determines whether the focus evaluation value is less than or equal to the predetermined value STh.
When the calculated focus evaluation value is less than or equal to the predetermined value STh, the CPU 19 makes an affirmative decision in step # 202 to determine in step # 202.
If the focus evaluation value is not equal to or smaller than the predetermined value STh, the process proceeds to step 203, where a negative determination is made in step # 202 and step # 206.
Proceed to. In step # 203, the CPU 19 determines whether the switching of the switch SW1 and the switch SW2 is prohibited. When the switching of the switches SW1 and SW2 is not prohibited, the determination in step # 203 is negative and the process proceeds to step # 204. When the switching of the switches SW1 and SW2 is prohibited, the determination in step # 203 is positive. The process according to FIG. 4 ends.

In step # 204, the CPU 19
Switches only the switch SW1 to the buffer A side and proceeds to step # 205. In step # 205, C
The PU 19 prohibits the switching of the switch SW1 and the switch SW2 and ends the process in FIG.

Now, the processes of steps # 201 to # 205 described above will be described with reference to FIG. 5 showing changes in the focus evaluation value. In FIG. 5, the horizontal axis represents time,
The vertical axis represents the focus evaluation value. The focus evaluation value is calculated at each of the times t1, t2, ..., T5. At time t1, the focus evaluation value VF1 is larger than the predetermined value STh. Therefore, the CPU 19 switches the switches SW1 and SW2 to the buffer B side between the times t1 and t2.

At time t2, the focus evaluation value VF
2 is smaller than the focus evaluation value VF1 and decreased. Also,
Focus evaluation value VF2 <predetermined value STh holds. CPU1
When the switching of the switches SW1 and SW2 is not prohibited, the switch 9 switches only the switch SW1 to the buffer A side between the times t2 and t3, and leaves the switch SW2 on the buffer B side. As a result, the image data captured by the solid-state image sensor 2 after this point is repeatedly overwritten and stored in the buffer A, and the image data of the previous frame captured by the solid-state image sensor 2 is stored in the buffer B. Are repeatedly read from and are continuously displayed on the liquid crystal monitor 8. That is, the refresh rate at which the video displayed on the liquid crystal monitor 8 is updated is slower than the frame rate at which the solid-state image sensor 2 captures an image.

Since the focus evaluation values VF3 to VF5 calculated at the times t3 to t5 in FIG. 5 are lower than the predetermined value STh, the object image picked up by the solid-state image pickup device 2 at these times has a blurred edge and a contrast. Is low,
It is likely that the subject is out of focus. At this time, time t2
Since the subject image that has already been captured at the point of time is kept displayed on the liquid crystal monitor 8, it is possible to prevent the subject image that is out of focus from being displayed.

On the other hand, a case where a negative determination is made in step # 201 described above will be described. In this case, the focus lens (not shown) in FIG.
This is the case when the calculated focus evaluation value increases, such as when the focus evaluation value is driven toward. In step # 206, the CP
U19 permits the switching of the switches SW1 and SW2 and proceeds to step # 207. Step # 2
At 07, the CPU 19 switches only the switch SW1 to the other buffer side and proceeds to step # 208. In step # 208, the CPU 19 switches the switch SW1 and the switch SW2 and ends the processing shown in FIG.

The above-mentioned step # 207 will be supplemented. For example, after switching the switch SW1 from the buffer B to the buffer A side (the switch SW2 remains on the buffer B side), one frame of image data captured by the solid-state image sensor 2 is stored in the buffer A. At this point, what is displayed on the liquid crystal monitor 8 is a video image based on the image data stored in the buffer B.

The step # 208 will be supplemented. The switches SW1 and SW2 are switched to the buffer B side (since the switch SW2 remains on the buffer B side,
Actually, only the switch SW1 is switched)
The image data for the next one frame captured by the solid-state image sensor 2 is stored in the buffer B. As a result, an image based on the image data stored in the buffer B is displayed on the liquid crystal monitor 8. At this point, the buffer A has a liquid crystal monitor 8
The image data captured one frame before the video displayed in is left. That is, the image data of one frame before is stored in the other buffer different from the buffer in which the image data displayed on the liquid crystal monitor 8 is stored.

Now, the processes of steps # 206 to # 208 described above will be described with reference to FIG. 6 showing changes in the focus evaluation value. In FIG. 6, the horizontal axis represents time,
The vertical axis represents the focus evaluation value. Times t11, t12, ..., T
At each time point of 15, the focus evaluation value is calculated. For example, at time t12, the focus evaluation value VF12
Is smaller than the predetermined value STh. However, the focus evaluation value VF1
2 is larger than the focus evaluation value VF11, and therefore increases.
Therefore, the CPU 19 switches the switches SW1 and SW2 to the other buffer side (buffer A side in this case) between the times t12 and t13. Similarly after time t13, the switches SW1 and SW2 are switched to the other buffer side.

The image data picked up by the solid-state image pickup device 2 is alternately stored in the buffer A and the buffer B as long as the focus evaluation value is increased, even if the focus evaluation value is equal to or less than the predetermined value STh. Like As a result, the image of the latest frame of image data captured by the solid-state image sensor 2 is sequentially updated and displayed on the liquid crystal monitor 8. That is,
The refresh rate at which the image displayed on the liquid crystal monitor 8 is updated is set to be the same as the frame rate at which the solid-state image sensor 2 captures an image. As a result, it is possible to confirm that the subject image gradually updated on the liquid crystal monitor 8 gradually becomes in focus as the focus evaluation value increases.

In the above description, the buffer A is stored in the memory 6.
~ Four buffers D are provided, and a through image is displayed on the liquid crystal monitor 8 using the buffers A and B. The number of buffers is not limited to four and may be at least two or more.

According to the embodiment described above, the following operational effects can be obtained. (1) Buffer A as a plurality of storage areas in the memory 6,
The buffer B is provided so that the image data of each frame captured by the solid-state image sensor 2 is alternately stored in the buffer A and the buffer B in order. As a result, the data can be read from the buffer B while the data is being written to the buffer A, and the data can be read from the buffer A while the data is being written to the buffer B. Therefore, as compared with the case where only one buffer is provided, The data read rate can be increased. That is, the frame rate of the image data captured by the solid-state image sensor 2 and recorded in the memory 6 can be made equal to the frame rate of the image data read from the memory 6. (2) When the focus evaluation value VF2 is smaller than the focus evaluation value VF1 and the focus evaluation value VF2 <the predetermined value STh is satisfied, if the switching of the switches SW1 and SW2 is not prohibited, only the switch SW1 is used for the other buffer. The switch SW2 is switched to the side (the buffer A side in the example of FIG. 5) and the switch SW2 is left as it is (the buffer B side in the example of FIG. 5). As a result, the image data picked up by the solid-state image sensor 2 after this point is stored in the other buffer side (see
In this example, the image data of the previous frame captured by the solid-state image sensor 2 is repeatedly overwritten and stored in the buffer A side (in the example of FIG. 5). Then, it is repeatedly read from the buffer B) and continuously displayed on the liquid crystal monitor 8. (3) When the focus evaluation value VF12 exceeds the focus evaluation value VF11, the switches SW1 and SW2 are switched to the other buffer side (buffer A side in the example of FIG. 6). As a result, the image data picked up by the solid-state image pickup device 2 is stored in the buffer A if the focus evaluation value increases.
And the buffer B are alternately stored, and the image of the latest frame image data captured by the solid-state image sensor 2 is sequentially updated and displayed on the liquid crystal monitor 8.

In the above description, the case where the AF digital camera performs the hill-climbing focus detection process and constantly drives the focus lens in the close-up direction and the infinity direction with the focus position P sandwiched therebetween has been described. Alternatively, the present invention can be applied to the focus detection operation for driving the focus lens only when the calculated focus evaluation value changes by a predetermined value or more. In this case, when the focus lens is not driven, the buffer A and the buffer B are alternately switched so that the subject image is sequentially updated and displayed on the liquid crystal monitor 8. On the other hand, when the focus lens is driven, an image based on the image data of the previous frame stored in the buffer A or the buffer B is displayed on the liquid crystal monitor 8 according to the change in the focus evaluation value described above. By sequentially updating and displaying the subject image on the liquid crystal monitor 8 when the focus lens is not driven, a new subject image can be displayed on the liquid crystal monitor 8 immediately when the camera is panned. Improves responsiveness when changing the composition of the camera. It should be noted that the determination as to whether or not the focus lens is driven may be performed before step # 201 in the flowchart of FIG. 4 described above.

Further, it is detected whether or not the zoom operation for changing the angle of view by the zoom lens is performed, and when the zoom operation is performed, the buffer A and the buffer A are irrelevant regardless of the calculated focus evaluation value. Alternatively, the image of the subject may be sequentially updated and displayed on the liquid crystal monitor 8 by alternately switching between the buffer B and the image. Generally, when the angle of view changes, the focus evaluation value changes. Therefore, when the previous frame image is displayed on the liquid crystal monitor 8 according to the focus evaluation value, the zoom operation of the subject image whose angle of view has been changed during the zoom operation ends. It disappears until you do. Therefore, when the zoom operation is detected and the subject image is sequentially updated and displayed on the liquid crystal monitor 8, a new subject image whose angle of view is being changed is immediately displayed on the liquid crystal monitor 8. Therefore, the angle of view of the camera is changed. Time response is improved.

In the above description, the AF digital still camera is taken as an example, but any camera having a hill-climbing focus detection device and an electronic viewfinder for displaying a monitor image may be a video camera or a silver salt. The present invention can be applied to cameras and the like.

The correspondence between each component in the claims and each component in the embodiment of the invention will be described. The solid-state image sensor 2 is an image sensor, the CPU 19 is an evaluation value calculation circuit, a drive signal output circuit, The read circuit, the read control circuit, and the operation signal detection circuit, the memory 6 as a storage circuit, the liquid crystal monitor 8 as a display device, the image data as an image pickup signal, and the image data of the previous frame as an image pickup signal at an old time, The buffers correspond to the storage areas, respectively.

[0039]

As described in detail above, the present invention has the following effects. (1) In the camera according to the first aspect of the present invention, the photographing lens is driven to the in-focus position so that the focus evaluation value calculated from the image pickup signal is maximized, and the focus evaluation value calculated using the image pickup signal. Accordingly, the image generated from the image pickup signal is prevented from being sequentially updated and displayed on the display device. As a result, for example, when the focus evaluation value decreases, images that are out of focus are not displayed successively, and it is possible to prevent a person looking at the display device from feeling uncomfortable. (2) In the camera according to the second aspect of the present invention, the photographing lens is driven to the in-focus position so as to maximize the focus evaluation value calculated from the image pickup signal, and the image pickup signals at different times are stored in the storage circuit. To do. According to the focus evaluation value calculated using the image pickup signal, the image pickup signal at the old time point is read from the memory circuit for display on the display device. As a result, for example, when the focus evaluation value is decreased, the image before the focus is shifted is displayed, so that it is possible to prevent a person looking at the display device from feeling uncomfortable. (3) In the camera according to the fifth aspect, the photographing lens is driven to the in-focus position so as to maximize the focus evaluation value calculated from the image pickup signal, and the image pickup signal is sequentially stored in another storage area of the storage circuit. Remember. According to the focus evaluation value calculated using the image pickup signal, the reading of the image pickup signal from the storage circuit in time series for displaying on the display device is stopped. As a result, for example, when the focus evaluation value decreases, an image that is out of focus is not newly displayed.
It is possible to prevent a person looking at the display device from feeling uncomfortable.

[Brief description of drawings]

FIG. 1 is a block diagram of an AF (autofocus) digital camera according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a relationship between a focus lens position of a photographing lens and a focus evaluation value.

FIG. 3 is a diagram illustrating a buffer area provided in a memory.

FIG. 4 is a flowchart illustrating a process performed by a CPU when a focus evaluation value changes.

FIG. 5 is a diagram showing a change in focus evaluation value.

FIG. 6 is a diagram showing a change in focus evaluation value.

[Explanation of symbols]

1 ... Shooting lens, 2 ... Solid-state image sensor, 3 ... Analog signal processing circuit, 4 ... A / D
Conversion circuit, 5 ... Digital signal processing circuit, 6 ...
Memory, 7 ... D / A converter, 8 ... Liquid crystal monitor, 9 ... Compression / decompression circuit, 10 ...
External storage medium, 11 ... AE / AWB processing circuit,
12 ... Control circuit, 13 ... Bandpass filter,
14 ... Accumulation circuit, 15 ... AF arithmetic circuit,
16 ... Motor, 17 ... Focus control mechanism, 19 ... CPU

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 5/232 G02B 7/11 D // H04N 101: 00 G03B 3/00 AF term (reference) 2H011 AA03 BA31 BB04 CA01 DA05 2H051 AA00 BA47 DB01 FA48 FA61 GA03 GA12 2H102 AB11 5C022 AA13 AB29 AB66 AC03 AC69 AC74

Claims (8)

[Claims] 1. An image pickup device for picking up a subject image through a taking lens, an evaluation value calculation circuit for calculating a focus evaluation value by using an image pickup signal output from the image pickup device, and calculation by the evaluation value calculation circuit. A drive signal output circuit that outputs a drive signal that drives the photographing lens to a focus position so as to maximize the focus evaluation value, and an image that is generated from the image pickup signal that is output from the image pickup device is sequentially updated and displayed. A camera comprising: a display device; and a display control circuit that causes the display device to prohibit update display according to a focus evaluation value calculated by the evaluation value calculation circuit. 2. An image pickup device for picking up a subject image through a photographing lens, an evaluation value calculation circuit for calculating a focus evaluation value using an image pickup signal output from the image pickup device, and a calculation for the evaluation value calculation circuit. A drive signal output circuit that outputs a drive signal that drives the photographing lens to a focus position so as to maximize a focus evaluation value; and a storage circuit that stores image pickup signals that are picked up by the image pickup device at different times. Generated from the image pickup signal read by the read circuit, which reads the old-time image pickup signal stored in the storage circuit according to the focus evaluation value calculated by the evaluation value calculation circuit. A camera comprising: a display device that sequentially updates and displays images. 3. The camera according to claim 2, wherein the readout circuit reads out an image pickup signal at an old time point from the storage circuit when the focus evaluation value is a predetermined value or less. 4. The camera according to claim 2, wherein the readout circuit reads out an image pickup signal at an old time point from the storage circuit when the focus evaluation value decreases with time. . 5. An image pickup device for picking up a subject image through a taking lens, an evaluation value calculation circuit for calculating a focus evaluation value by using an image pickup signal output from the image pickup device, and calculation by the evaluation value calculation circuit. A drive signal output circuit that outputs a drive signal that drives the photographing lens to the in-focus position so as to maximize the focus evaluation value, and a memory that sequentially stores the image signals output from the image sensor in different storage areas. A circuit, a read circuit for reading the image pickup signal stored in the storage circuit in time series, and a new image pickup signal for the read circuit according to the focus evaluation value calculated by the evaluation value calculation circuit. A camera comprising a read control circuit for prohibiting read, and a display device for sequentially updating and displaying an image generated from an image pickup signal read by the read circuit. 6. The camera according to claim 5, wherein the read control circuit prohibits reading of a new image pickup signal when the focus evaluation value is equal to or less than a predetermined value. 7. The camera according to claim 5, wherein the readout control circuit prohibits the readout of a new image pickup signal when the focus evaluation value decreases with time. 8. The camera according to claim 6, wherein the taking lens is a zoom lens, and further comprises an operation signal detecting circuit for detecting a zoom operation signal for changing an angle of view of the taking zoom lens. The read control circuit prohibits the reading of a new image pickup signal when the operation signal is detected by the operation signal detection circuit.