JP2004286780A - Digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital camera capable of increasing the autofocusing speed by shortening the photographing time lag from the completion of movement of a focus lens to the execution of next processing in the case of autofocusing processing. <P>SOLUTION: The digital camera is provided with a CCD, a focus lens, a focus driving part. a clock signal supply part for generating a clock signal having one frequency selected from a plurality of frequencies, and a driving signal generation part which generates a vertical synchronizing signal with a period proportional to the clock signal generated by the clock signal supply part, and the frequency of the clock signal generated by the clock signal supply part is changed when the focus lens is moved to reach a prescribed position when photographing. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital camera having an autofocus function for adjusting a focal position of a subject image by moving a focus lens during photographing.
[0002]
[Prior art]
In recent years, digital cameras equipped with an image sensor such as a CCD (Charge Coupled Device) have come to be widely used as photographing apparatuses. A digital camera has a lens unit that includes a focus lens, zoom lens, aperture, filter unit, and a drive system that moves the lens, a CCD that receives a subject image and outputs the signal, and a signal that processes the signal from the CCD. A general configuration includes a processing system, a liquid crystal display (LCD) display unit, a power supply system, and a control system that controls the operation of each component.
[0003]
When shooting with a digital camera, for example, when taking a still image, shooting conditions such as focus, aperture, and shutter speed greatly affect the shooting result. Among these, with regard to focusing, a digital camera is equipped with an autofocus function, so that shooting failures are reduced and a good image can be obtained.
[0004]
This autofocus function can be divided into the following two methods according to the subject image focusing method.
That is, in the first method, the contrast of the subject image is monitored by the photographing CCD while the focus lens is physically moved continuously in the optical axis direction, and the focus lens having the highest contrast in the moving range. Is determined as the position where the subject image is focused on the CCD, that is, the focus position of the focus lens, which is called a contrast detection method or CCD autofocus (CCDAF).
[0005]
The operation content of the contrast detection method will be described with reference to the timing chart shown in FIG. FIG. 6 shows, in a time series, the operation contents from the start of focus processing by pressing the first release to exposure before capturing an image of a subject in a general contrast detection type digital camera. Here, the operation content of the hill-climbing scan single method in which the output of the distance measuring sensor does not act on a series of autofocus processes will be described.
The hill-climbing scan is to continuously move the focus lens in the optical axis direction within the movable range of the focus lens while monitoring the contrast of the subject image in order to obtain the focus position of the focus lens. .
[0006]
(S81) The first release button for operating the autofocus function is pressed, and a first release signal is generated.
(S82) The focus lens moves to the hill-climbing scan start position by the first release signal.
(S83) After the movement of the focus lens to the hill-climbing scan start position is completed, the CCD enters a state of monitoring the contrast of the subject image from the optical system (CCDAF), and the focus lens starts moving from the hill-climbing scan start position.
(S84) A second release button for photographing is pressed, and a second release signal is generated.
(S85) The focus lens moves to the final position in the movable range.
(S86) The position of the focus lens where the contrast of the subject image is highest within the range of the hill-climbing scan is determined as the focus position of the focus lens.
(S87) The focus lens moves to the in-focus position.
(S88) After the movement of the focus lens to the in-focus position is completed, a subject image capturing process through the optical system is started, and the subject image is exposed onto the CCD.
[0007]
The generation of the second release signal is not necessarily at the position in the drawing, and it may be established at an arbitrary position from the generation of the first release signal to the start of the capturing process. Although the case of the hill-climbing scan single method has been described with reference to FIG. 6, the operation content regarding the hill-climbing scan is the same as that described above even in the case of the hybrid autofocus method.
[0008]
The second method of the autofocus function is a method of measuring the distance to the subject with a distance measuring sensor and obtaining the in-focus position of the focus lens based on the measurement result, such as a phase difference detection method.
[0009]
The operation content of this method will be described with reference to the timing chart shown in FIG. FIG. 7 shows the operation contents in time series from the start of focus processing by pressing the first release to exposure before capturing an image of a subject in a general phase difference detection type digital camera. The operation content will be described below.
[0010]
(S91) The first release button for operating the autofocus function is pressed, and a first release signal is generated.
(S92) Based on the first release signal, the distance measuring sensor unit calculates the distance to the subject based on the sensor measurement result, and the calculation result is determined as the focus position of the focus lens.
(S93) The focus lens moves to the in-focus position.
(S94) The second release button for photographing is pressed, and a second release signal is generated.
(S95) After the movement of the focus lens to the in-focus position is completed, the subject image capturing process through the optical system is started, and the subject image is exposed onto the CCD.
[0011]
The generation of the second release signal is not necessarily at the position in the figure, and it may be established at an arbitrary position from the generation of the first release signal to the start of the capturing process.
[0012]
Recently, a hybrid autofocus function that combines the autofocus functions of the above two methods to perform fine adjustment by a hill-climbing scan method after rough adjustment by, for example, a distance measurement sensor unit (distance information calculation unit of the distance measurement sensor and the image processing unit). There is also a camera that can easily focus on a desired subject part (see, for example, Patent Document 1).
[0013]
[Patent Document 1]
JP 2002-31328 A (paragraphs [0031] to [0032], FIG. 6)
[0014]
[Problems to be solved by the invention]
However, in any of the above-described autofocus functions, a wasteful waiting time (shooting time lag) called VD wait occurs between the time when the movement of the focus lens is completed and the next processing is performed. There was a problem that hindered the speeding up of the system. The VD wait is a waiting time during which no processing is performed due to a mixture of a synchronous system and an asynchronous system for a vertical synchronization signal (VD) in processing related to an imaging system such as autofocus. It is.
[0015]
For example, in the case of the contrast detection method shown in FIG. 6, the VD waiting time t91 occurs between the time when the focus lens is completely moved to the hill-climbing scan start position and the time when the hill-climbing scan is started. Furthermore, a VD waiting time t92 has occurred between the completion of the movement of the focus lens to the in-focus position and the start of the capture process.
[0016]
Further, in the case of the phase difference detection method of FIG. 7, a VD waiting time t93 occurs between the time when the focus lens is moved to the in-focus position and the time when the capturing process is started.
[0017]
The present invention has been made in view of the above-described problems in the prior art, and shortens the shooting time lag from the completion of the movement of the focus lens during the autofocus process until the next process is performed, and the autofocus. An object of the present invention is to provide a digital camera capable of increasing the speed.
[0018]
[Means for Solving the Problems]
The inventors of the present invention are that the synchronization system and the asynchronous system to the vertical synchronization signal (VD) are mixed, that is, the movement of the focus lens to the hill-climbing scan start position (VD asynchronous) and the start of the hill-climbing scan (VD synchronization). Paying attention to the fact that there is a wasteful waiting time due to mixing and mixing of the focus lens to the in-focus position (VD asynchronous) and the start of image capture (VD synchronization), the vertical synchronization signal (VD) is From the viewpoint of adjustment, intensive studies have been made and the present invention has been made.
[0019]
In other words, a digital camera according to the first aspect of the present invention provided to solve the above problem includes an imaging device, a focus lens for forming a subject image on the imaging device, and moving the focus lens in the optical axis direction. A focus driving unit that adjusts the focal position of the subject image, a clock signal supply unit that generates a clock signal having one frequency selected from a plurality of frequencies as a reference clock signal, a trigger that is driven by the imaging device, A synchronization signal generation unit that generates a synchronization signal with a period proportional to the reference clock signal, and the frequency of the reference clock signal is changed when the focus lens is moved and reaches a predetermined position during photographing. It is characterized by.
[0020]
According to the first aspect of the present invention, it is possible to adjust the waiting time from the completion of the movement of the focus lens in the autofocus process until the next process is performed, and the autofocus speed can be increased. Become.
Note that, for example, a vertical synchronization signal (VD) corresponds to the synchronization signal serving as a trigger for driving the image sensor.
[0021]
According to a second aspect of the present invention, there is provided a digital camera according to the second aspect of the present invention. The digital camera according to the first aspect of the present invention is configured so that the focus lens is continuously moved so that the imaging element has a high contrast of the subject image. In order to perform a hill-climbing scan for searching for a position, the frequency of the reference clock signal increases when the focus lens is moved to reach a hill-climbing scan start position.
[0022]
According to the second aspect of the present invention, the photographing time lag between the time when the focus lens is moved to the hill-climbing scan start position and the time when the hill-climbing scan is started can be shortened. High speed is possible.
[0023]
According to a third aspect of the present invention, there is provided a digital camera according to a third aspect of the present invention, wherein the frequency of the reference clock signal is reached when the focus lens is moved and reaches a focus position of a subject image. Is increased.
[0024]
According to the invention of claim 3, the photographing time lag is shortened from the completion of the movement of the focus lens to the in-focus position until the capturing process is started, the start of exposure can be accelerated, and the speed of autofocus can be increased. It becomes possible.
[0025]
According to a fourth aspect of the present invention, there is provided a digital camera according to a fourth aspect of the present invention, wherein an imaging device, a focus lens that forms a subject image on the imaging device, and the focus lens are moved in the optical axis direction. A focus drive unit that adjusts the focal position of the subject image, a clock signal supply unit that generates a clock signal having one frequency selected from a plurality of frequencies as a reference clock signal, and synchronization that serves as a trigger for driving the image sensor And a synchronization signal generator for generating a signal in a cycle proportional to the reference clock signal, and the frequency of the reference clock signal is changed when the focus lens starts moving during photographing.
[0026]
According to the invention of claim 4, by adjusting the moving time of the focus lens to a predetermined position, the photographing time lag is shortened, and the speed of autofocus can be increased.
[0027]
According to a fifth aspect of the present invention, there is provided a digital camera according to a fifth aspect of the present invention, wherein the focus driving means is a pulse motor, and the focus lens is moved from a movement start position to a predetermined position. The moving time is calculated from the pulse rate of the pulse motor, and the frequency of the reference clock signal is changed so that the period of the synchronization signal approximates the calculated moving time.
[0028]
According to the fifth aspect of the present invention, it is possible to adjust the movement time of the focus lens to a predetermined position in accordance with the actual situation, effectively reducing the photographing time lag and increasing the speed of autofocus. The period of the synchronization signal after the frequency change of the reference clock signal is preferably slightly longer than the movement time from the focus lens movement start position calculated from the pulse rate of the pulse motor to the predetermined position.
[0029]
According to a sixth aspect of the present invention, there is provided the digital camera according to the sixth aspect of the present invention, wherein the movement of the focus lens continuously moves the focus lens so that the image sensor is a subject image. Is a movement up to a hill-climbing scan start position for searching for a hill-climbing scan to search for the position of a high-contrast focus lens, and the frequency of the reference clock signal is such that the period of the synchronization signal approximates the calculated movement time It is characterized by becoming smaller.
[0030]
According to the sixth aspect of the present invention, the photographing time lag between the time when the focus lens is moved to the hill-climbing scan start position and the time when the hill-climbing scan is started can be shortened, and the start of the hill-climbing scan can be made faster. High speed is possible. Furthermore, by reducing the frequency of the reference clock signal, it is possible to reduce the power consumption as compared with the prior art.
[0031]
According to a seventh aspect of the present invention, there is provided the digital camera according to the seventh aspect of the present invention, wherein the movement of the focus lens is a movement to the in-focus position of the subject image, and the calculated movement is performed. The frequency of the reference clock signal is reduced so that the period of the synchronization signal approximates the time.
[0032]
According to the seventh aspect of the present invention, the photographing time lag is shortened from the completion of the movement of the focus lens to the in-focus position until the capturing process is started, the start of exposure can be made earlier, and the speed of autofocus can be increased. It becomes possible. Furthermore, by reducing the frequency of the reference clock signal, it is possible to reduce the power consumption as compared with the prior art.
[0033]
The digital camera according to an eighth aspect of the present invention provided to solve the above-described problem is the digital camera according to the first to seventh aspects of the present invention, wherein the frequency of the reference clock signal is changed before the reference clock signal is changed. An image picked up in the synchronization signal period is continuously output to the image display unit.
[0034]
According to the eighth aspect of the present invention, the image output to the display system during the period in which the frequency of the reference clock signal is switched continues to be output as the image before switching, so that the image update rate generated by the change in the frequency of the reference clock signal is not affected. A normal image can be displayed while avoiding displaying an image disturbed by the alignment. The image display unit is a monitor display unit built in the digital camera or an external monitor display device connected to the digital camera.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a configuration of an embodiment of a digital camera according to the present invention will be described with reference to the drawings. In addition, what is shown below illustrates embodiment and is not limited to this.
FIG. 1 is a block diagram showing a basic configuration of a digital camera according to the present invention.
The digital camera shown in FIG.
(1) Ranging sensor 100
(2) Optical system: an aperture shutter 101, a lens unit 102 having a focus lens and a zoom lens, an operation of the aperture and shutter, and an optical system drive unit 110 that moves the focus lens and the zoom lens in the optical axis direction.
(3) Image pickup unit: CCD 103 which is an aspect of the image sensor, CDS A / D 104 which samples and digitizes the output signal of CCD 103, timing generator 105 which is an aspect of the synchronization signal generation part which drives CCD 103, timing A clock generator 106 which is an embodiment of a clock signal supply unit that sends a reference clock signal to the generator 105
(4) An image processing unit 107 that performs predetermined signal processing on the image data received from the CDS / A / D 104.
(5) Image display unit: an optical system, an imaging unit, a liquid crystal display (LCD) 108 for displaying an image output via the image processing unit 107, and an external monitor connection jack 109 for connecting to an external monitor
(6) Memory unit; an image data buffer memory 111 that temporarily stores captured image data, an image data recording unit 113 that records captured image data, a program for storing a control program for the CPU 112, and the like Memory 114
(7) Control unit: CPU 112, operation switch 115 having a release button for transmitting the first release signal and the second release signal.
(8) Power supply unit 116 that supplies power to each unit in the digital camera
It has.
[0036]
The distance measuring sensor 100 is a sensor unit for obtaining distance information between a digital camera and a subject, and may be either an active method or a passive method. The output result of the distance measuring sensor 100 is calculated by a distance information calculating unit included in the image processing unit 107 to obtain distance information. Furthermore, the focus position of the focus lens is obtained from the information as necessary. In the case of phase difference detection type autofocus, based on the obtained focus position information, the focus lens movement is instructed to the optical system drive unit 110 via the CPU 112, and the focus lens moves to the focus position. .
[0037]
The optical system drive unit 110 drives the aperture shutter 101 and the focus lens and zoom lens of the lens unit 102 to set shooting conditions and the like. In particular, the optical system drive unit 110 includes a pulse motor that is one mode of the focus drive unit for moving the focus lens and a driver that drives the motor. The lens is moved within the entire range movable in the optical axis direction, and the focus lens is moved in the optical axis direction to a predetermined position or in-focus position at the time of monitoring or capturing a recorded image.
[0038]
The clock generator 106 generates a clock signal having one frequency selected from a plurality of frequencies, and transmits the clock signal having the frequency to the timing generator 105 as a reference clock signal. Note that the same type of function as the clock generator 106 may be provided in the timing generator 105.
[0039]
The timing generator 105 generates a horizontal synchronizing signal (HD) and a vertical synchronizing signal (VD) which is a synchronizing signal that is a trigger for driving the CCD. Further, counting is performed based on the reference clock signal received from the clock generator 106, and the period of the horizontal synchronizing signal (HD) is set based on the counter value. Next, the period of the vertical synchronizing signal (VD) is set based on the counter value of the horizontal synchronizing signal (HD). Each counter value can be adjusted.
[0040]
The CCD 103, the CDS / A / D 104, and the image processing unit 107 receive the pulse signal of the vertical synchronization signal (VD) set by the timing generator 105 as a drive trigger. For example, in a hill-climbing scan, the hill-climbing scan is started in response to the first pulse signal after the focus lens reaches the hill-climbing scan start position. Also, the image capturing process is started upon receiving the first pulse signal after the focus lens reaches the in-focus position. The image sensor may be a CMOS sensor in addition to the CCD 103.
[0041]
On an external monitor connected to a liquid crystal display (LCD) 108 and an external monitor connection jack 109, an OSD image, a monitoring image, a thumbnail image at the time of taking a still image, a playback image of a recorded image, and the like are displayed. The image display unit may be organic electroluminescence (EL) instead of the LCD.
[0042]
The frequency of the reference clock signal is changed according to an instruction from the image processing unit 107 at a predetermined timing. The predetermined timing is, for example, when the focus lens reaches the hill-climbing scan start position, when the focus lens starts moving to the hill-climbing scan start position, when the focus lens reaches the in-focus position, and when the focus lens is in focus For example, when to start moving to a position. When the frequency of the reference clock signal is changed, the timing generator 105 changes the period of the horizontal synchronizing signal (HD) and the vertical synchronizing signal (VD) correspondingly.
[0043]
Next, a first embodiment of the digital camera according to the present invention will be described with reference to a timing chart shown in FIG. FIG. 2 shows the operation contents in time series from the start of focus processing by pressing the first release to exposure before capturing an image of a subject in a hill-climbing scan single-system autofocus digital camera.
[0044]
(S11) The first release button for operating the autofocus function is pressed, and a first release signal is generated. Here, the output of the distance measuring sensor does not affect the subsequent series of autofocus processes.
[0045]
(S12) In response to the first release signal, the focus lens starts to move to the hill-climbing scan start position. Here, in the clock generator 106, a period (clock switching valid period) in which the reference clock signal can be changed from the frequency CLK1 to another frequency from the start of the movement to immediately before the start of the hill-climbing scan.
(S13) The focus lens completes the movement to the hill-climbing scan start position. Upon detecting the completion of the movement of the focus lens, the image processing unit 107 instructs the clock generator 106 to change the frequency of the reference clock signal.
(S14) The clock generator 106 changes the frequency of the reference clock signal from CLK1 to CLK2 having a higher frequency than CLK1.
(S15) In the timing generator 105, the period of the vertical synchronizing signal (VD) is changed from VD1 to VD2, which is shorter than VD1, in response to the change of the reference clock signal to the frequency CLK2.
(S16) Since the cycle of the vertical synchronizing signal (VD) becomes shorter than usual, the pulse signal is generated earlier than in the case of the cycle VD1. Therefore, the VD waiting time becomes t1, and the VD waiting time is shorter than the VD waiting time t91 in the case of the constant cycle VD1 shown in FIG. Note that the clock switching valid period ends immediately after the generation of the pulse signal, the frequency of the reference clock signal returns to CLK1, and accordingly, the cycle of the thrust synchronizing signal (VD) also returns to VD1.
[0046]
(S17) The hill-climbing scan is started by the first pulse signal of the vertical synchronization signal (VD) after the movement of the focus lens to the hill-climbing scan start position is completed. That is, the CCD is in a state of monitoring the contrast of the subject image from the optical system (CCDAF), and the focus lens starts moving from the hill-climbing scan start position.
(S18) A second release button for photographing is pressed, and a second release signal is generated.
(S19) The focus lens moves to the final position in the movable range.
(S1a) The position of the focus lens where the contrast of the subject image is highest within the range of the hill-climbing scan is determined as the focus position of the focus lens.
[0047]
(S1b) The focus lens starts moving to the in-focus position. Here, in the clock generator 106, the clock switching valid period is from the start of the movement to immediately before the start of the capturing process.
(S1c) The focus lens completes moving to the in-focus position. Upon detecting the completion of the movement of the focus lens, the image processing unit 107 instructs the clock generator 106 to change the frequency of the reference clock signal.
(S1d) The clock generator 106 changes the frequency of the reference clock signal from CLK1 to CLK3 having a higher frequency than CLK1.
(S1e) In the timing generator 105, the period of the vertical synchronizing signal (VD) is changed from VD1 to VD3 having a shorter period than VD1 in response to the change of the reference clock signal to the frequency CLK3.
(S1f) Since the period of the vertical synchronizing signal (VD) becomes shorter than usual, the generation of the pulse signal occurs earlier than in the case of the period VD1. Therefore, the VD waiting time becomes t2, which is shorter than the VD waiting time t92 in the case of the constant cycle VD1 shown in FIG. Note that the clock switching valid period ends immediately after the generation of the pulse signal, the frequency of the reference clock signal returns to CLK1, and accordingly, the cycle of the thrust synchronizing signal (VD) also returns to VD1.
[0048]
(S1g) The subject image capturing process through the optical system is started by the first pulse signal of the vertical synchronizing signal (VD) after the movement of the focus lens to the in-focus position is completed, and the subject image is exposed onto the CCD. .
[0049]
In the first embodiment, the VD wait time is shortened by switching the frequency of the reference clock signal from CLK1 to CLK2 immediately after the focus lens moves to the hill-climbing scan start position (VD2 <VD1, t1). <T91). Further, immediately after the focus lens is moved to the in-focus position, the frequency of the reference clock signal is switched from CLK1 to CLK3, so that the waiting time for VD is shortened (VD3 <VD1, t2 <t92). By this sequence, the effect of speeding up autofocus can be obtained.
[0050]
The external monitor connected to the LCD 108 and the external monitor connection jack 109 outputs the image before the frequency change during the period when the frequency of the reference clock signal is switched, that is, during the above steps s14 to s16 and s1e to s1f. It is good to continue. As a result, it is possible to avoid displaying an image that is disturbed due to a mismatch with the image update rate generated by the change in the frequency of the reference clock signal.
[0051]
In FIG. 2, the first switching timing of the frequency of the reference clock signal is set after the focus lens movement to the hill-climbing scan start position is completed (step s13). It may be the timing of s12). In addition, the second switching timing of the frequency of the reference clock signal is after completion of the movement of the focus lens to the in-focus position (step s1c), but as the timing at the start of the movement of the focus lens to the in-focus position (step s1b). Also good.
[0052]
However, the frequency switching timing is preferably the timing shown in FIG. 2 for both the first timing and the second timing in terms of reducing the load on the power supply unit 116 of the digital camera. A sequence in which the frequency of the reference clock signal with a large load on the power supply unit 116 increases and a pulse motor driving sequence for moving the focus lens with a large load on the power supply unit 116 overlap, and a transient voltage drop occurs. This is because it can be avoided that the digital camera tends to end automatically.
[0053]
Next, a second embodiment of the digital camera according to the present invention will be described with reference to a timing chart shown in FIG. FIG. 3 shows the operation contents in time series from the start of the focus process by pressing the first release to the exposure before capturing the image of the subject in the hill-climbing scan single-system autofocus digital camera as in FIG.
[0054]
(S21) A first release button for operating the autofocus function is pressed, and a first release signal is generated. Here, the output of the distance measuring sensor does not affect the subsequent series of autofocus processes.
[0055]
(S22) In response to the first release signal, the focus lens starts to move to the hill-climbing scan start position.
(S23) At the time when the first vertical synchronizing signal (VD) pulse signal is generated after the focus lens starts moving to the hill-climbing scan start position, the image processing unit 107 sends the frequency of the reference clock signal to the clock generator 106. Direct change.
(S24) The clock generator 106 changes the frequency of the reference clock signal from CLK1 to CLK4 having a smaller frequency than CLK1.
This frequency CLK4 is calculated from the pulse rate of the pulse motor that moves the focus lens with respect to the distance from the focus lens movement start position (current position) to the hill-climbing scan start position, and is vertically synchronized with the calculated movement time. The period of the pulse signal of the signal (VD) is required to approximate. Specifically, after changing the frequency of the reference clock signal, the remaining time obtained by subtracting the time from the focus lens movement time to the time when the pulse signal of the first vertical synchronization signal (VD) is generated from the movement time of the focus lens is subtracted. The frequency is determined so that one cycle of the pulse signal of the vertical synchronizing signal (VD) is the same or slightly larger.
(S25) In the timing generator 105, the period of the vertical synchronization signal (VD) is changed from VD1 to VD4 having a longer period than VD1 in response to the change of the reference clock signal to the frequency CLK4.
(S26) Since the period of the vertical synchronizing signal (VD) becomes longer than usual, the generation of the pulse signal becomes slower than in the case of the period VD1.
(S27) The movement of the focus lens is completed at the hill-climbing scan start position, and a pulse signal of the vertical synchronization signal (VD) is generated immediately after that. As a result, the VD waiting time is significantly shortened compared to the VD waiting time t91 in the case of the constant cycle VD1 shown in FIG. Note that the clock switching valid period ends immediately after the generation of the pulse signal, the frequency of the reference clock signal returns to CLK1, and accordingly, the cycle of the thrust synchronizing signal (VD) also returns to VD1.
[0056]
(S28) The hill-climbing scan is started by the first pulse signal of the vertical synchronization signal (VD) after the movement of the focus lens to the hill-climbing scan start position is completed.
(S29) A second release button for photographing is pressed, and a second release signal is generated.
(S2a) The focus lens moves to the final position in the movable range.
(S2b) The position of the focus lens where the contrast of the subject image is highest within the range of the hill-climbing scan is determined as the focus position of the focus lens.
[0057]
(S2c) The focus lens starts moving to the in-focus position.
(S2d) The image processing unit 107 changes the frequency of the reference clock signal to the clock generator 106 when the pulse signal of the first vertical synchronization signal (VD) is generated after the focus lens starts moving to the in-focus position. Instruct.
(S2e) The clock generator 106 changes the frequency of the reference clock signal from CLK1 to CLK5 having a smaller frequency than CLK1. The method for obtaining the frequency CLK5 is the same as the method for obtaining the frequency CLK4 in step s24.
(S2f) In the timing generator 105, the period of the vertical synchronizing signal (VD) is changed from VD1 to VD5 having a longer period than VD1 in response to the change of the reference clock signal to the frequency CLK5.
(S2g) Since the period of the vertical synchronizing signal (VD) becomes longer than usual, the generation of the pulse signal becomes slower than in the case of the period VD1.
(S2h) The movement of the focus lens at the in-focus position is completed, and a pulse signal of the vertical synchronization signal (VD) is generated immediately after that. As a result, the VD waiting time is significantly shortened compared to the VD waiting time t92 in the case of the constant cycle VD1 shown in FIG. Note that the clock switching valid period ends immediately after the generation of the pulse signal, the frequency of the reference clock signal returns to CLK1, and accordingly, the cycle of the thrust synchronizing signal (VD) also returns to VD1.
[0058]
(S2i) The object image capturing process through the optical system is started by the first pulse signal of the vertical synchronizing signal (VD) after the movement of the focus lens to the in-focus position is completed, and the object image is exposed onto the CCD. .
[0059]
In the second embodiment, when the focus lens movement period to the hill-climbing scan start position has a low period of the vertical synchronization signal (VD), the vertical synchronization signal is switched by switching the frequency of the reference clock signal from CLK1 to CLK4. (VD4> VD1) is realized by delaying the low period of (VD) immediately after the movement of the focus lens is completed (VD4> VD1). Further, when the focus lens movement period to the in-focus position has a low period of the vertical synchronization signal (VD), the low period of the vertical synchronization signal (VD) is delayed by switching the frequency of the reference clock signal from CLK1 to CLK5. Thus, the waiting time for VD is shortened (VD5> VD1). With this sequence, the frequency of the reference clock signal becomes small (low speed) when the pulse motor is driven to move the focus lens with a heavy load with respect to the power supply unit 116, so that the auto sustain speed and the power supply sustainability can be improved. An effect is obtained.
[0060]
The external monitor connected to the LCD 108 and the external monitor connection jack 109 outputs the image before the frequency change during the period when the frequency of the reference clock signal is switched, that is, during the above steps s24 to s27 and s2e to s2h. It is good to continue. As a result, it is possible to avoid displaying an image that is disturbed due to a mismatch with the image update rate that occurs due to a change in the frequency of the reference clock signal.
[0061]
Next, a third embodiment of the digital camera according to the present invention will be described with reference to a timing chart shown in FIG. FIG. 4 shows the operation contents in time series from the start of focus processing by pressing the first release to exposure before capturing an image of a subject in a phase difference detection type autofocus digital camera.
[0062]
(S31) The first release button for operating the autofocus function is pressed, and a first release signal is generated.
(S32) Based on the first release signal, the distance measuring sensor 100 calculates the distance to the subject based on the sensor measurement result, and the calculation result is determined as the focus position of the focus lens.
(S33) The focus lens starts moving to the in-focus position determined in step s32.
(S34) The second release button for photographing is pressed, and a second release signal is generated.
(S35) The focus lens completes moving to the in-focus position. Upon detecting the completion of the movement of the focus lens, the image processing unit 107 instructs the clock generator 106 to change the frequency of the reference clock signal.
(S36) The clock generator 106 changes the frequency of the reference clock signal from CLK1 to CLK6 having a higher frequency than CLK1.
(S37) In the timing generator 105, the period of the vertical synchronizing signal (VD) is changed from VD1 to VD6 having a shorter period than VD1 in response to the change of the reference clock signal to the frequency CLK6.
(S38) Since the cycle of the vertical synchronizing signal (VD) becomes shorter than usual, the generation of the pulse signal occurs earlier than in the case of the cycle VD1. Therefore, the VD waiting time becomes t3, which is shorter than the VD waiting time t93 in the case of the constant cycle VD1 shown in FIG. Note that the clock switching valid period ends immediately after the generation of the pulse signal, the frequency of the reference clock signal returns to CLK1, and accordingly, the cycle of the thrust synchronizing signal (VD) also returns to VD1.
(S39) The object image capturing process through the optical system is started by the first pulse signal of the vertical synchronizing signal (VD) after the movement of the focus lens to the in-focus position is completed, and the object image is exposed onto the CCD. .
[0063]
In the third embodiment, the VD wait time is shortened by switching the frequency of the reference clock signal from CLK1 to CLK6 immediately after the focus lens moves to the in-focus position (VD6 <VD1, t3 < t93). By this sequence, the effect of speeding up autofocus can be obtained.
[0064]
Since the frequency of the reference clock signal is switched within the period from when the focus lens is moved to the in-focus position and the capturing process is started, the external monitor connected to the LCD 108 or the external monitor connection jack 109 has a frequency before the frequency switch. It is advisable to keep outputting images. Specifically, it may be performed within the period from the operation of step s33 to step s38. As a result, it is possible to avoid displaying an image that is disturbed due to a mismatch with the image update rate that occurs due to a change in the frequency of the reference clock signal.
[0065]
In FIG. 4, the frequency switching timing of the reference clock signal is set after the focus lens movement to the in-focus position is completed (step s35). However, the timing when the focus lens movement to the in-focus position is started (step s33) is also possible. Good.
[0066]
However, the frequency switching timing is preferably the timing shown in FIG. 4 in terms of reducing the load on the power supply unit 116 of the digital camera. A sequence in which the frequency of the reference clock signal with a large load on the power supply unit 116 increases and a pulse motor driving sequence for moving the focus lens with a large load on the power supply unit 116 overlap, and a transient voltage drop occurs. This is because it can be avoided that the digital camera tends to end automatically.
[0067]
Next, a fourth embodiment of the digital camera according to the present invention will be described with reference to a timing chart shown in FIG. FIG. 5 shows the operation contents in time series from the start of the focus processing by pressing the first release to the exposure before capturing the subject image in the phase difference detection type autofocus digital camera as in FIG.
[0068]
(S41) The first release button for operating the autofocus function is pressed, and a first release signal is generated.
(S42) Based on the first release signal, the distance measuring sensor 100 calculates the distance to the subject based on the sensor measurement result, and the calculation result is determined as the focus position of the focus lens.
(S43) The focus lens starts moving to the in-focus position determined in step s42.
(S44) At the time when the first vertical synchronizing signal (VD) pulse signal is generated after the focus lens starts moving to the in-focus position, the image processing unit 107 changes the frequency of the reference clock signal to the clock generator 106. Instruct.
(S45) The clock generator 106 changes the frequency of the reference clock signal from CLK1 to CLK7 having a smaller frequency than CLK1.
This frequency CLK7 is calculated from the pulse rate of the pulse motor that moves the focus lens with respect to the distance from the focus lens movement start position (current position) to the in-focus position, and the vertical synchronization signal is added to the calculated movement time. The period of the (VD) pulse signal is required to be approximated. Specifically, after changing the frequency of the reference clock signal, the remaining time obtained by subtracting the time from the focus lens movement time to the time when the pulse signal of the first vertical synchronization signal (VD) is generated from the movement time of the focus lens is subtracted. The frequency is determined so that one cycle of the pulse signal of the vertical synchronizing signal (VD) is the same or slightly larger.
(S46) In the timing generator 105, the period of the vertical synchronization signal (VD) is changed from VD1 to VD5 having a longer period than VD1 in response to the change of the reference clock signal to the frequency CLK5.
(S47) Since the period of the vertical synchronizing signal (VD) becomes longer than usual, the generation of the pulse signal is delayed as compared with the case of the period VD1.
(S48) The second release button for photographing is pressed, and a second release signal is generated.
(S49) The movement of the focus lens is completed at the in-focus position, and a pulse signal of the vertical synchronizing signal (VD) is generated immediately after that. As a result, the VD waiting time is significantly shortened compared to the VD waiting time t93 in the case of the constant cycle VD1 shown in FIG. Note that the clock switching valid period ends immediately after the generation of the pulse signal, the frequency of the reference clock signal returns to CLK1, and accordingly, the cycle of the thrust synchronizing signal (VD) also returns to VD1.
(S4a) The subject image capturing process through the optical system is started by the first pulse signal of the vertical synchronizing signal (VD) after the movement of the focus lens to the in-focus position is completed, and the subject image is exposed onto the CCD. .
[0069]
In the fourth embodiment, when the focus lens movement period to the in-focus position has a Low period of the vertical synchronization signal (VD), the frequency of the reference clock signal is switched from CLK1 to CLK7 to change the vertical synchronization signal ( (VD7> VD1) is realized by delaying the Low period of (VD). As a result, the effect of improving the power supply sustainability as well as increasing the speed of autofocus can be obtained.
[0070]
Since the frequency of the reference clock signal is switched within the period from when the focus lens is moved to the in-focus position and the capturing process is started, the external monitor connected to the LCD 108 or the external monitor connection jack 109 has a frequency before the frequency switch. It is advisable to keep outputting images. In detail, it is good to implement before the operation | movement of the said step s43 within the period from the operation | movement of step s42 to step s49. As a result, it is possible to avoid displaying an image that is disturbed due to a mismatch with the image update rate that occurs due to a change in the frequency of the reference clock signal.
[0071]
【The invention's effect】
As described above, according to the first aspect of the present invention, by adjusting the waiting time from the completion of the movement of the focus lens during the autofocus process until the next process is performed, High speed can be realized.
According to the second aspect of the present invention, it is possible to speed up the start of the hill-climbing scan by shortening the photographing time lag between the completion of the movement of the focus lens to the hill-climbing scan start position and the start of the hill-climbing scan. it can.
According to the third aspect of the present invention, it is possible to speed up the start of exposure by shortening the photographing time lag from the completion of the movement of the focus lens to the in-focus position until the capturing process is started.
According to the invention of claim 4, the photographing time lag can be shortened by adjusting the movement time of the focus lens to a predetermined position.
According to the fifth aspect of the present invention, the photographing time lag can be effectively shortened by adjusting the movement time of the focus lens to the predetermined position according to the actual situation.
According to the sixth aspect of the present invention, the imaging time lag from when the focus lens is completely moved to the hill-climbing scan start position to when the hill-climbing scan is started is shortened, and the hill-climbing scan can be started earlier. Furthermore, by reducing the frequency of the clock signal, it is possible to reduce power consumption as compared with the prior art.
According to the seventh aspect of the present invention, the photographing time lag is shortened from the completion of the movement of the focus lens to the in-focus position until the capturing process is started, so that the exposure can be started earlier. Furthermore, by reducing the frequency of the clock signal, it is possible to reduce power consumption as compared with the prior art.
According to the eighth aspect of the present invention, the image output to the display system during the period in which the frequency of the clock signal is switched is continued to be output before switching, so that the image update rate caused by the change in the frequency of the clock signal is not affected. A normal image can be displayed by avoiding displaying an image disturbed by the alignment.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a digital camera according to the present invention.
FIG. 2 is a timing chart showing the first embodiment of the digital camera according to the present invention.
FIG. 3 is a timing chart showing a second embodiment of the digital camera according to the present invention.
FIG. 4 is a timing chart showing a third embodiment of the digital camera according to the present invention.
FIG. 5 is a timing chart showing a fourth embodiment of the digital camera according to the present invention.
FIG. 6 is a timing chart relating to autofocus in a conventional digital camera of a contrast detection method.
FIG. 7 is a timing chart relating to autofocus in a conventional digital camera using a phase difference detection method.
[Explanation of symbols]
100 Ranging sensor
101 Aperture / Shutter
102 Lens unit
103 CCD
104 CDS / A / D
105 Timing generator
106 Clock generator
107 Image processing unit
108 LCD (Liquid Crystal Display)
109 External monitor connection jack
110 Optical system drive unit
111 Image data buffer memory
112 CPU
113 Image data recording unit
114 Program memory
115 Operation switch
116 Power supply

Claims (8)

An image sensor, a focus lens that forms a subject image on the image sensor, a focus drive unit that adjusts the focus position of the subject image by moving the focus lens in the optical axis direction, and a plurality of frequencies A clock signal supply unit that generates a clock signal having one frequency as a reference clock signal, and a synchronization signal generation unit that generates a synchronization signal that is a trigger to be driven by the imaging device in a cycle proportional to the reference clock signal. ,
A digital camera, wherein the frequency of the reference clock signal is changed when the focus lens is moved to reach a predetermined position during photographing. When the focus lens is moved to reach a hill-climbing scan start position in order to perform a hill-climbing scan in which the focus lens is continuously moved and the image sensor searches for the position of the focus lens with a high contrast of the subject image, The digital camera according to claim 1, wherein the frequency of the reference clock signal is increased. The digital camera according to claim 1, wherein the frequency of the reference clock signal increases when the focus lens is moved to reach a focus position of a subject image. An image sensor, a focus lens that forms a subject image on the image sensor, a focus drive unit that adjusts the focus position of the subject image by moving the focus lens in the optical axis direction, and a plurality of frequencies A clock signal supply unit that generates a clock signal having one frequency as a reference clock signal, and a synchronization signal generation unit that generates a synchronization signal that is a trigger to be driven by the imaging device in a cycle proportional to the reference clock signal. ,
A digital camera, wherein the frequency of the reference clock signal is changed when the focus lens starts to move during photographing. The focus driving means is a pulse motor;
The movement time from the movement start position of the focus lens to a predetermined position is calculated from the pulse rate of the pulse motor, and the frequency of the reference clock signal is changed so that the period of the synchronization signal approximates the calculated movement time. The digital camera according to claim 4. The movement of the focus lens is a movement to a hill-climbing scan start position for continuously moving the focus lens and performing a hill-climbing scan in which the imaging device searches for the position of the focus lens with a high contrast of the subject image. 6. The digital camera according to claim 5, wherein the frequency of the reference clock signal is reduced so that the period of the synchronization signal approximates the calculated movement time. The movement of the focus lens is movement to an in-focus position of a subject image, and the frequency of the reference clock signal is reduced so that the period of the synchronization signal approximates the calculated movement time. 5. The digital camera according to 5. 8. When the frequency of the reference clock signal is changed, the image picked up in the synchronization signal period before the reference clock signal is changed is continuously output to the image display unit. A digital camera according to one.

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