JPH0943493A - Lens driving device and imaging device - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To maintain an in-focus state of a subject during a zoom operation at the time of image pickup by a slow shutter. A zoom speed is variably controlled by a lens driver 4 moving and controlling a position of a zoom lens 2 based on a control signal from a lens driving circuit 11 according to an input shutter speed. Further, the CCD 5 controlled by the CCD driver 7 based on the control signal generated from the timing generator 10 according to the shutter speed.
The video signal for each field processed by the camera signal processing circuit 6 after being picked up by the
It is stored and read in the video memory 9 controlled by the memory controller 12 based on the control signal from 0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens driving device having a mechanism for performing a zooming operation on an object imaged by an imaging device whose exposure time is controllable, and an imaging device using this lens driving device.

[0002]

2. Description of the Related Art At present, many image pickup apparatuses, such as video cameras and camcorders, perform a zoom operation and a focus operation by a structure having a zoom lens and a focus lens inside a lens block section.

In this zoom operation, the depth of field varies depending on the position of the zoom lens between the wide angle (wide) and the telephoto (tele). In particular,
If the zoom lens is on the wide-angle side, the depth of field will be deeper,
If it is on the telephoto side, the depth of field will be shallow. Here, having a deep depth of field means that the in-focus state is easily maintained even if the subject moves a little forward or backward from the point of focusing on the subject, that is, focusing. A shallow depth of field means that it is difficult to maintain a focused state.

The focus lens provided inside the lens block portion is called an inner focus lens. As a focusing operation for focusing on a subject using the inner focus lens, a so-called autofocus method is often used in which the focusing operation is automatically performed using an output obtained by detecting a video signal of an image of the subject. This auto-focus method is called a hill-climbing servo method and controls a motor that drives a focus lens to detect one field of a high-frequency component of a luminance signal in a video signal of a subject as a focus evaluation value. There is a method in which the focus evaluation value is constantly compared with the focus evaluation value one field before and the motor is continuously vibrated minutely so as to obtain the maximum value.

When the subject is moved to the out-of-focus state after the motor is stopped in the in-focus state and the focus operation is performed again, generally, the focus evaluation value is used to drive the motor. Determine the restart timing. That is, the focus evaluation value at the time of reaching the in-focus state is stored, the focus evaluation value is always calculated even after focusing, and this focus evaluation value is compared with the stored focus evaluation value in advance. If it falls below the set threshold value, it is determined that the subject has moved, and the focus operation is restarted.

In the above-mentioned autofocus system, the operation of correcting the focus position so as to always maintain the in-focus state with respect to the subject according to the zoom position and the distance to the subject is called a zoom tracking operation.

When an image of an object is picked up by an image pickup apparatus having the above-mentioned lens block section, for example, a solid-state image pickup element is used as an image pickup device for receiving light from the object.
Specifically, interline CCD (Charge Coupled D
In many cases, the light from the subject is received by using evice), the received light amount is converted into an electric signal, and the video signal for each field is output using the field blanking period. The video signal is, for example, NTSC system or P, which is used for color television broadcasting, in which a luminance signal Y and two color difference signals RY and BY are multiplexed.
This is an AL standard color television signal.

Here, since one field of the NTSC color television signal is 1/60 second, the shutter speed when the NTSC system color television signal is imaged for each field is 1 in the image pickup apparatus. /
It will be 60 seconds. This 1/60 second speed is the standard shutter speed.

When the image pickup device is provided with an electronic shutter function, with a high-speed shutter, the accumulation time of the signal charges from once outputting all the signal charges of the light receiving portion of the CCD to starting the transfer is 1/60. It is shorter than a second and the excess charge is discarded. Specifically, as shown in FIG. 4, the shutter is released every field F ₁ , F ₂ , ..., F ₈ , that is, every 1/60 second, and one field shown in A of FIG. When the video data for each is received as light by the CCD and stored, a storage signal shown in B of FIG. 4 is obtained. This accumulated signal is converted into a video signal shown in C of FIG. 4 and outputted when the light of the video data of the next field delayed by one field is accumulated in the CCD. By performing this operation for each field, continuous video signals can be obtained. At this time, the autofocus operation is performed by obtaining the focus evaluation value used for the autofocus operation from the video signal for each field.

Further, the shutter is released at a speed slower than the standard shutter speed, and C is continuously applied for a plurality of field times.
After the light is received by the light receiving portion of the CD and accumulated, the signal charge is transferred to increase the area of the light receiving portion of the CCD, and the sensitivity to the subject can be increased without using a large-diameter lens. The exposure at this time is called multiple exposure or multi-field accumulation exposure, and the shutter speed slower than the standard shutter speed is called slow shutter.

For example, when the shutter speed is a slow shutter of 1/30 second, the light of the video data for each field shown in A of FIG. 5 is changed to 2 as shown in B of FIG.
The CCD receives the field time and stores it. The accumulated light is converted into a video signal with a delay of two field times and output, as shown in C of FIG. As a result, only one field of video signal can be obtained for every two fields, so that the video signal of the first field is stored in the memory or the like and the video signal of the first field is output as the video signal of the second field. . That is, a video signal for one field is output for a time period of two fields, and the video signal is updated every two fields. At this time, the focus evaluation value used for the autofocus operation can be obtained only for every two fields as well as the video signal, so that the autofocus operation is also performed every two fields, and the autofocus operation becomes slow.

As described above, the slower the shutter speed, the longer the accumulation time of the video data. Therefore, the period for obtaining the video signal becomes longer and the autofocus operation becomes slower.

[0013]

By the way, as described above, since the autofocus operation becomes slow when the image is taken by the slow shutter, when the zoom operation is performed at the time of the image taken by the slow shutter, the zoom operation, specifically, the above-mentioned operation is performed. It becomes difficult to maintain the in-focus state by the zoom tracking operation of. As a result, when the zoom operation is performed during the slow shutter operation, the focus on the subject, that is, the so-called focus is likely to shift. This focus shift is caused by a slower shutter speed, that is, a longer multiple exposure time, or
The faster the zooming speed is, the more easily the focus evaluation value for the autofocusing operation cannot be obtained, so that the focus evaluation value easily occurs.

Therefore, in view of the above situation, the present invention provides a lens driving device capable of maintaining the in-focus state of a subject during a zoom operation at the time of imaging by a slow shutter, and an imaging device using this lens driving device. It is a thing.

[0015]

A lens driving apparatus according to the present invention controls the position of the zoom lens by the zoom lens driving means so as to variably control the moving speed of the zoom lens according to an exposure control signal from the input means. By controlling the movement by the control means, the subject is focused during the zoom operation.

Further, the image pickup apparatus according to the present invention controls the control of moving the position of the zoom lens by the zoom lens driving means so as to variably control the moving speed of the zoom lens according to the exposure control signal from the input means. While doing by means,
By subjecting the pixel signal from the image pickup means to signal processing and outputting the pixel signal, the subject is focused in the zoom operation during image pickup by the slow shutter.

[0017]

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 schematic block diagram of an image pickup apparatus according to the present invention.

The lens driving device according to the present invention inputs a lens driver 4 which is a zoom lens driving means for moving the position of the zoom lens 2 for varying the depth of field, and an exposure control signal for controlling the exposure time of a subject. And an input terminal 14 which is an input means for controlling the lens driver 4 which controls the lens driver 4 so as to variably control the moving speed of the zoom lens 2 in accordance with an exposure control signal from the input terminal 14. 11 and 11.

Further, as shown in FIG. 1, the image pickup device according to the present invention is a lens driving device including the above-mentioned means, which receives light from the subject and converts it into pixel signals. It comprises a certain CCD 5 and a camera signal processing circuit 6 which is a signal processing means for processing a pixel signal from the CCD 5 and outputting a video signal.

Next, the operation of the image pickup apparatus shown in FIG. 1 will be described.

In the image pickup apparatus of FIG. 1, a zoom instruction signal is input from the zoom switch 13 to the lens drive circuit 11 during a zoom operation for picking up an image of a subject. At this time, an exposure control signal for controlling the exposure time of the subject is input to the input terminal 14, and this exposure control signal is sent to the lens drive circuit 11 and the timing generator 10. Here, the exposure control signal is specifically a signal indicating the shutter speed, and is input by manually operating an operation button or the like, or automatically switched according to a luminance signal at the time of image capturing or the like. To do.

In the lens drive circuit 11, when the zoom instruction signal is input, the movement amount of the zoom lens 2 is generated so as to control the movement speed of the zoom lens 2 based on the exposure control signal. The amount of movement of the zoom lens 2 is sent to the lens driver 4.

Here, in order not to shift the focus of the subject during the zoom operation, an upper limit value of the moving speed of the zoom lens 2, so-called zoom speed is set, and the zoom lens 2 is moved at a zoom speed faster than the set upper limit value. A movement amount of the zoom lens 2 for variably controlling the zoom speed so as not to drive the zoom lens 2 is generated. Specifically, as shown in FIG. 2, the zoom speed when the shutter speed is higher than the standard shutter speed of 1/60 seconds is set as the upper limit value S. Then, the zoom speed when the shutter speed is slower than 1/60 seconds is set in advance. The movement amount of the zoom lens 2 sent to the lens driver 4 is generated so that the zoom lens 2 is moved at the zoom speed based on the exposure control signal.
In the lens driver 4, the position of the zoom lens 2 is movement-controlled by controlling the driving of a motor or the like (not shown) based on the movement amount of the zoom lens 2 to adjust the depth of field.

When the subject is imaged by controlling the zoom speed, the timing generator 10 sends a CCD drive timing signal based on the exposure control signal to the CCD driver 7. The CCD driver 7 is the above CCD
A CCD (Charge Coupled Device) 5 which is a solid-state image pickup device which is an image pickup device based on a drive timing signal.
Drive control.

The light from the object to be imaged is imaged and received by the light receiving portion of the CCD 5 through the zoom lens 2 and the focus lens 3 inside the lens block portion 1. The amount of light received and detected by the CCD 5 is converted into an electric signal and output to the camera signal processing circuit 6.

The camera signal processing circuit 6 generates a video signal by performing signal processing using the input electric signal. This video signal is a standard color television signal of the NTSC system or the PAL system in which a luminance signal Y and two color difference signals RY and BY are used, which is used for color television broadcasting, for example. .

The luminance signal of the video signal generated by the camera signal processing circuit 6 is sent to the autofocus detector 8 (hereinafter referred to as AF detector 8) to evaluate the focus during the autofocus operation. A value is generated. The focus evaluation value during the operation of the autofocus lens is sent to the lens drive circuit 11.

In this lens drive circuit 11, by performing autofocus calculation using the focus evaluation value sent, the amount of movement of the focus lens 3 for controlling the moving speed of the focus lens 3 during the autofocus operation is determined. It is generated and sent to the lens driver 4. The lens driver 4 controls the drive of a motor or the like (not shown) based on the amount of movement of the focus lens 3 to control the movement of the position of the focus lens 3 so as to automatically focus on the subject.

The signal-processed video signal is stored in the video memory 9 which is drive-controlled by the memory controller 12 for each field. A memory drive timing signal based on the exposure control signal is sent from the timing generator 10 to the memory controller 12, and the memory controller 12 stores the video signal for each field using the memory drive timing signal. The video memory 9 is controlled as follows. This video memory 9
The video signal for each field stored in is read out according to the shutter speed and output to the outside.

In addition to setting the upper limit value of the zoom speed, a zoom speed coefficient corresponding to the shutter speed is set,
The zoom speed may be variably controlled at a speed obtained by multiplying the zoom speed by the zoom speed coefficient. Specifically, as shown in FIG. 3, the shutter speed is 1 / the standard shutter speed.
When the zoom speed coefficient is faster than 60 seconds, the upper limit of 1.
Set to 0. Then, the zoom speed coefficient when the shutter speed is slower than 1/60 seconds is set in advance. The zoom speed is calculated by using the zoom speed coefficient based on the exposure control signal, and the position of the zoom lens 2 is controlled to be moved by the zoom speed, so that the focus shift of the subject during the zoom operation can be avoided. .

[0032]

As is apparent from the above description, the lens driving device according to the present invention is such that the zoom lens driving means variably controls the moving speed of the zoom lens according to the exposure control signal from the input means. By performing the control for moving the position of the zoom lens by the control means, it is possible to focus on the subject during the zoom operation, and thus it is possible to avoid the focus shift of the subject during the zoom operation.

Further, the image pickup apparatus according to the present invention controls the control for moving the position of the zoom lens by the zoom lens driving means so as to variably control the moving speed of the zoom lens according to the exposure control signal from the input means. While doing by means,
By subjecting the pixel signal from the image pickup means to signal processing and outputting, it is possible to focus on the subject in the zoom operation during image pickup with the slow shutter.
It is possible to avoid the focus shift of the subject during the zoom operation.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a lens driving device according to the present invention.

FIG. 2 is a diagram showing a relationship between a shutter speed and a zoom speed.

FIG. 3 is a diagram showing a relationship between a shutter speed and a zoom speed coefficient.

FIG. 4 is a diagram showing timings of capturing and outputting a video signal at a standard shutter speed.

FIG. 5 is a diagram showing timing of image pickup and output of a video signal at a slow shutter speed.

[Explanation of symbols]

 1 lens block section 2 zoom lens 3 focus lens 4 lens driver 5 CCD 6 camera signal processing circuit 7 CCD driver 8 AF detector 9 video memory 10 timing generator 11 lens drive circuit 12 memory controller 13 zoom switch 14 input terminal

Claims (2)

[Claims] 1. A zoom lens drive means for moving a position of a zoom lens for varying a depth of field, an input means for inputting an exposure control signal for controlling an exposure time of a subject, and an exposure control signal from the input means. And a control means for controlling the zoom lens driving means so as to variably control the moving speed of the zoom lens. 2. A zoom lens drive means for moving a position of a zoom lens for varying a depth of field, an input means for inputting an exposure control signal for controlling an exposure time of a subject, and an exposure control signal from the input means. In accordance with the above, the control means for controlling the zoom lens driving means so as to variably control the moving speed of the zoom lens, the image pickup means for receiving light from the subject and converting it into pixel signals, and the image pickup means And a signal processing means for processing the pixel signal of (1) and outputting a video signal.