JPH0620267B2 - Mountain climbing type autofocus device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects a so-called focus voltage, which is higher than a high-frequency component of a video signal, in a better focus condition, and detects a peak point of the focus voltage to perform focusing. Regarding the mountain climbing type autofocus device that performs the focusing operation of the lens,
In particular, the present invention relates to an autofocus device that drives the focusing lens with a pulse motor.

2. Description of the Related Art As a mountain climbing type autofocus device in which a focusing lens is driven by a pulse motor, there is a device disclosed in Japanese Patent Laid-Open No. 59-66274.

The driving concept of the pulse motor in this device is characterized in that its driving cycle is synchronized with the cycle of generating the video signal, specifically, the cycle of the vertical synchronizing signal.

In other words, the number of drive pulses included in the detection period of the differential voltage is the same by performing the drive timing of the pulse motor in synchronization with the timing at which the focus voltage is updated.

Therefore, the focusing operation in the above proposed apparatus will be briefly described below with reference to the operation state example diagram of FIG. 4 based on the vertical synchronizing signal.

FIG. 4 is a schematic waveform diagram showing one operation state when a focusing operation is performed on an object at an arbitrary position within the shooting screen. FIG. 4 (a) is a vertical synchronization signal, and FIG. 4 (b) is an image. Signal, Figure (c) is the screen gate signal for setting the above arbitrary locations,
(d) is the focus voltage at an arbitrary position determined by the screen gate signal, and (e) is the focus voltage confirmed to use the focus voltage shown in (d) in the pulse motor drive control. The confirmation timing signal, (f) in the figure shows the drive timing pulse of the pulse motor, respectively. As is clear from FIG. 4, in this example, the focus voltage is reset by the vertical synchronizing signal, and the drive timing pulse of the pulse motor is output at a half cycle of the vertical synchronizing signal, and the pulse motor is driven accordingly. It is designed to be done.

Now, movement of the focusing lens is started by the pulse motor driven at the driving timing as shown in FIG. 4 (f), and for example, the movement direction is the movement toward the focusing position. Then, the focus voltage gradually rises as shown in FIG.

The value of the focus voltage is confirmed at the timing shown in FIG. 4 (e), and is compared with the previous confirmation contents by the drive control means of the pulse motor. In the case of this example, since the focus voltage is increasing, the pulse motor is driven by the drive control means as it is, that is, in the same direction.

When the focusing lens further moves and exceeds the in-focus position, the focus voltage drops as indicated by X in FIG. 4 (d).

This decrease in the focus voltage is detected by comparing the confirmation content of the timing signal Y of FIG. 4 (e) with the confirmation content of the previous timing signal Y-1, and as a result, the driving direction of the pulse motor thereafter is the same as the previous one. It will be controlled in the opposite direction.

That is, the pulse motor is driven in the opposite direction from the drive timing signal Z in FIG. 4 (f).

When the pulse motor is rotated in the reverse direction, the focus voltage will increase again, but in such a case, the focusing lens has already reached the vicinity of the focus position, so it should immediately drop beyond the focus position again. Therefore, the pulse motor eventually reverses the reverse rotation operation due to the focus voltage drop detection within a short time.

Therefore, by detecting the repetitive operation as described above or by detecting the decrease of the focus voltage in the timing signal Y, the pulse is generated so that the focusing lens is positioned at the position where the peak of the focus voltage up to that point is obtained. When the motor is driven, the focusing operation on the arbitrary subject is completed.

Problems to be Solved by the Invention The above-described operation is a basic focusing operation in the autofocus device disclosed in Japanese Patent Laid-Open No. 59-66274. However, in the above device, a video camera or the like is used. No consideration is given to the accumulation action of the image pickup tube that forms the video signal, and this accumulation action causes a problem.

The inconvenience will be described below, but before that, the accumulation action of the image pickup tube will be briefly described.

An image pickup tube currently used in a video camera or the like has a storage capacity C for every pixel. Therefore, the incident light is converted into a current according to the light intensity by the photoelectric effect, and is accumulated as electric charge in the storage capacitor C for a certain period of time, that is, the incident light is integrated over the period of time. The SN ratio is increased by the accumulation effect.
The fixed time is usually called the accumulation period.

The charges stored in the storage capacitor C are discharged at once by scanning with an electron beam in each storage period, and are taken out as an output signal.

The extracted output signal is then converted into a video signal by the camera device and used for the focusing operation as described above.

The outline of the principle of converting the image formation supplied to the image pickup tube into a video signal has been briefly described above. However, even when a solid-state image pickup device such as a CCD is used, there is a difference in structure and the like, but the accumulation as described above. Needless to say, the action is similarly performed to improve the SN ratio.

Now, regarding the inconvenience caused by the influence of the above-described accumulation action on the focusing operation, the focus voltage and the focusing lens position described in FIG. Consider the relationship shown in FIG. 5 and the relationship between the characteristic and the amount of high frequency components of the video signal.

The signals shown in FIGS. 5 (a), (b), (f), (g), and (h) are the fourth signals.
Vertical sync signals shown in Figures (a), (f), (c), (d), and (e), pulse motor drive timing signals, screen gate signals, focus voltage, and focus voltage confirmation timing signals are shown. . FIG. 7C is a position characteristic diagram showing the position of the focusing lens driven by the pulse motor driven by the timing signal shown in FIG.

Further, FIG. 5 (d) is a schematic diagram showing an actual focusing state in the image pickup tube with the movement of the focusing lens as shown in FIG. 5 (c), and FIG. 6 is a schematic diagram showing a state of a high frequency component amount obtained by integrating a high frequency component included in a video signal according to a change in image forming state due to movement of a focusing lens.

The storage period by the storage capacitor C described above is illustrated in FIG. 5 assuming that the cycle T of the vertical synchronizing signal is the same for convenience of description.

Regarding the relationship between the signals and the like shown in FIG. 5, first, looking at the focus voltage which is the basis of the focusing operation described in FIG. 4, it is said that the characteristics shown in FIG. 5 (g) are obtained. That is, the fact that the characteristic of the amount of high frequency components contained in the video signal must be the characteristic as shown in FIG. 5 (e) means that the screen gate signal shown in FIG. It is also clear from the focus voltage confirmation timing signal.

However, since the amount of the high frequency component shown in FIG. 5 (e) is obtained based on the video signal output through the above-mentioned accumulation action, its peak state Q is supplied to the image pickup tube. The image formation will be delayed from the timing when the image is actually focused.

That is, the actual focus state of the image supplied to the image pickup tube is obtained by T / 2 earlier than the peak state Q of the high frequency component amount as shown by P in FIG. 5 (d). It is needless to say that the period T / 2 is determined because the video signal period is T and the driving timing of the focusing lens is the period T / 2.

On the other hand, considering the relationship as described above centering on the position of the focusing lens shown in FIG. 5 (c), the focusing lens position at which the above-mentioned focused state P of the image formation is obtained is of course O. Will be shown. That is, for a subject for which the characteristics of the high frequency components or the focus voltage as shown in FIGS. 5 (e) and 5 (g) are obtained, the position indicated by O in FIG. 5 (c) is focused. It is the focal point of the lens.

However, in reality, as described with reference to FIG. 4, the decrease in the focus voltage is detected by the focus voltage confirmation timing signal Y, and the drive timing signal Z of the pulse motor is reversed until the pulse motor is reversed. The focusing lens moves to the position R as shown in FIG.

That is, in the mountain climbing type autofocus device,
Due to the accumulation action of the image pickup tube, the drop detection of the focus voltage is inevitably delayed, and as shown in FIG.
In the case of an example of the apparatus proposed in Japanese Patent No. 6274, that is, an apparatus for driving at a period of T / 2 synchronized with the period T of the vertical synchronizing signal of the pulse motor, the focusing lens drives the pulse motor drive pulse from the focus position O. The signal would overrun by four.

As a result, the image is slightly blurred again after being brought into the in-focus state, which is very unsightly.

Although not described in the previous description, considering the characteristics of the screen gate signal and the focus voltage confirmation timing signal shown in FIGS. 5 (f) and 5 (h), the characteristics shown in FIG. 5 (g) are obtained. The characteristic of the focus voltage, that is, the level of the focus voltage is different from that in FIG. 5 (e), but the characteristic that the decrease of the focus voltage can be detected by the confirmation timing signal Y is shown in FIG. It can also be obtained by the characteristic of the amount of high frequency components as shown in, and in such a case, the focused state of the image formation supplied to the image pickup tube is as shown by the broken line in FIG. The focus state is P ', which is delayed as compared with the above description.

Therefore, it goes without saying that the focusing position of the focusing lens is O ', which is different from O in the previous case. In such a case, the overrun amount of the focusing lens is three drive pulse signals from the in-focus position O ′, which is 1 compared to the previous case.
Although the number is reduced by the number, the unsightlyness of the photographed image due to overrun exists in any case.

Further, the number of drive pulse signals that may cause the focusing lens to overrun is 2 for the above-mentioned three or four when the drive pulse signal period shown in FIG. 5 is an example of T / 2. Although it is a species, it is also clear that by setting the above period to T / 3 or T / 4, various kinds of overrun states will occur.

The present invention has been made in consideration of the delay in detecting the decrease in the focus voltage due to the accumulation action of the image pickup tube as described above, and minimizes the movement of the focusing lens in the "blurred" direction, which makes the captured image unsightly. It is an object of the present invention to provide an autofocus device with improved height.

Means for Solving the Problems In a mountain climbing type autofocus device for driving a focusing lens according to the present invention with a pulse motor, the drive pulse signal for driving the pulse motor is supplied to check the focus voltage and end the increase / decrease detection operation. The number of the driving pulses is set to be ₀ in synchronization with the driving pulse, the period is t ₀ , the focus voltage confirmation and increase / decrease detection operation period is t ₁ , the idle period in which the focus voltage is not detected is t ₂ , period t ₃ when the supply of the signal for driving the pulse motor _actually, if any integer and the a, {(a-1) t 0 + t 3} ÷ 2 + t 1 <t 2/2 the condition is satisfied The control unit is configured to have a maximum integer A or less.

Operation Since the mountain climbing type autofocus device according to the present invention has the above-mentioned configuration, the pulse motor for moving the focusing lens is activated in synchronization with the end of the detection operation of the increase / decrease of the focus voltage, and its driving The number of drive pulse signals for performing the focus adjustment is set in consideration of its own period and the pause period of the focus voltage detection operation. Therefore, the focusing lens must move intensively after the focus voltage increase / decrease detection operation is completed. become.

As a result, it becomes possible to detect the fluctuation of the focus voltage quickly, minimize the effect of the accumulation effect of the image pickup tube, etc., and the amount of overrun from the focus position of the focusing lens, that is, in the blur direction. The amount of movement can be minimized.

Embodiment FIG. 1 is a block diagram showing the construction of an embodiment of a mountain climbing type autofocus device according to the present invention. In the figure, reference numeral 1 denotes a known lens device including a focusing lens 1a and the like, which is mounted on a camera device 2 which outputs a video signal. Reference numeral 3 denotes a known focus voltage detecting means for detecting and outputting a focus voltage from a high frequency component in a predetermined screen area of a video signal obtained from the camera device 2.

Reference numeral 4 is a well-known differential circuit that detects an increase / decrease in the focus voltage output from the focus voltage detection means 3 and outputs an increase / decrease signal indicating increase / decrease / invariance of the focus voltage. Reference numeral 5 indicates the focusing lens 1a in the lens apparatus 1. The pulse motor to move is shown.

Reference numeral 6 denotes a motor driving means, which supplies a pulse signal having a predetermined cycle including a shortest cycle capable of driving the pulse motor 5 as a drive pulse signal for driving the motor in forward and reverse directions, and from the oscillation circuit 7. And a motor drive circuit 8 for driving the motor 5 forward and backward based on the drive pulse signal.

Reference numeral 9 denotes a motor drive control means, which starts its operation by receiving an increase / decrease signal from the difference circuit 4 and outputs a direction signal indicating a drive direction of the motor 5 based on the increase / decrease signal.
Further, it detects the end of the increase / decrease detection operation of the difference circuit 4 and outputs a start signal for starting the driving of the motor 5, and supplies the start signals to the motor drive circuit 8 and the oscillation circuit 7 of the motor drive means 6, respectively.

Reference numeral 10 is a setting means, which is to be driven until the next operation of the focus voltage detection means 3 is started.
Drive amount is set on the basis of the maximum number signal supplied from the calculating means 13 described later. The setting content of the setting means 10 is of course the number of drive pulse signals, and the number itself is less than or equal to the maximum number indicated by the maximum number signal.

Reference numeral 11 is a counting means for counting the number of drive pulse signals supplied to the motor 5 from the oscillation circuit 7 of the motor drive means 6 through the motor drive circuit 8 and reset by the start signal, and 12 is a comparison means. The number of pulse signals set by the setting means 10 and the number of pulse signals counted by the counting means 11 are compared, and when the two coincide, the operation of the oscillation circuit 7 is stopped, that is, the motor driving means 6 performs the above operation. A coincidence signal for stopping the driving of the motor 5 is output.

Reference numeral 13 denotes a calculation means, which is oscillation period information of the oscillation circuit 7, operation pause period information from the current operation end time of the focus voltage detection means 3 to the next operation start time, and the difference circuit 4
From the operation end time of the difference circuit 4 to the operation start time of the next focus voltage detecting means 3 by receiving the operation period information and the information on the period during which the pulse motor 5 is actually driven by the supply of the drive pulse signal. Half of the period from the rise of the first signal of the drive pulse signal supplied to the drive pulse to the stop of the drive of the pulse motor 5 by the last signal ends the operation of this time more than the half of the operation rest period. The maximum number of drive pulse signals that satisfy the condition on the time point side is calculated, and the maximum number signal indicating the calculated maximum number is output to the setting means 10. Note that the above-mentioned reference numeral 6
It goes without saying that each of the configurations shown by 13 corresponds to the above-mentioned control means for controlling the start and supply of the driving pulse signal to the pulse motor 5.

The operation of the present embodiment having the above-mentioned structure will be described below with reference to the schematic waveform diagram of FIG.

Now, when the image signal of the image formed through the lens device 1 as shown in FIG. 2 (b) is output from the camera device 2 based on the vertical synchronizing signal shown in FIG. 2 (a). The focus voltage detecting means 3 detects and outputs the focus voltage from the high frequency component in the predetermined area of the photographing screen defined by the screen gate signal shown in FIG. 2 (c).

The focus voltage is confirmed by the difference circuit 4 on the basis of the focus voltage confirmation timing signal shown in FIG. 2 (e), and the contents of the previous confirmation are compared. An increase / decrease signal indicating increase, decrease, or no change in the focus voltage will be output.

Needless to say, the above operation is the same as that of the conventional device.

When the difference circuit 4 outputs the increase / decrease signal, the motor drive control means 9 starts the operation, outputs the direction signal, and ends the operation of the difference circuit 4, that is, the output of the timing signal of FIG. 2 (e). It detects and outputs a start signal and supplies it to the motor drive means 6.

Therefore, the oscillator circuit 7 and the motor drive circuit 8 of the motor drive means 6 operate, and the pulse signal output from the oscillator circuit 7 to the pulse motor 5 is synchronized with the end of the signal in FIG. 2 (e). It will be supplied as a drive pulse signal via 8.

At the same time, the pulse signal of the oscillation circuit 7 supplied to the pulse motor 5 is counted by the counting means 11, and the counted content is supplied to the comparison means 12.

On the other hand, the comparing means 12 has the calculating means 13 as described above.
The number of drive pulse signals equal to or less than the maximum number indicated by the maximum number signal output by is set by the setting means 10 and supplied.

The maximum number calculated by the calculating means 13 will be described.

2 (f), (g), and FIG.
As shown in (e) and (c), the period of the drive pulse signal output from the oscillation circuit 7 and supplied to the pulse motor 5 via the motor drive circuit 8 is t ₀ , the operating period of the difference circuit 4, that is, The focus voltage confirmation and comparison period is t ₁ , and the focus voltage detection means 3
Is an idle period during which the operation is not performed, that is, t ₂ is a non-output period of the screen gate signal, t ₃ is a period in which the pulse motor 5 is actually driven based on the supply of the drive pulse signal, and A is an arbitrary integer, The maximum number in the present invention can be described by the following formula. That is, mean that the maximum number of the above in the present invention _{{(A-1) t 0} + t 3} ÷ 2 + t 1 <t 2 / largest integer A 2 The condition is satisfied.

Further detailed in the illustrated example, FIG. 2 (f), (g), (e), (c)
From the relationship of the above-mentioned intervals of t ₀ , t ₁ , t _{2 shown} in FIG.
For example, t ₀ = 2 _msec , t ₁ = 2 _msec , t ₂ = 1
Considering 0 _msec and t ₃ = 1 _msec , the above equation becomes {(A-1) × 2 + 1} ÷ 2 + 2 <10/2, and when deformed, A <3.5. Therefore A <
The maximum integer for which 3.5 holds is 3 and therefore, Fig. 2
In the case of the interval relations shown in (f), (g), (e), and (c), the set number of drive pulse signals by the setting means 10 is 3, which is the maximum number, and 2, 1, 1. It becomes an individual. In other words, a device in which the number of drive pulse signals supplied is up to 3 is the mountain climbing type autofocus device of this embodiment.

By the way, the reason why the number of drive pulse signals is limited by the above equation is the result of considering the characteristic of the amount of high frequency components described later, and it will be briefly described as follows.

That is, the amount of high-frequency components of the video signal for obtaining the focus voltage due to the accumulation action of the image pickup tube described above is obtained by delaying the accumulation period from the actual image formation state, but as described above. When the number of drive pulse signals is limited by the equation, the characteristic of the high frequency component amount, which will be described later, indicating the fluctuation state of the image formation by the limited number of drive pulse signals is always measured immediately after the supply of the drive pulse signals. This is because it can be used as a reference for the focus voltage detection operation, and the delay due to the above-described accumulation action can be minimized.

In other words, by setting the number of drive pulse signals limited by the equation as described above, the focusing lens 1a is intensively moved immediately after the operation of the differential circuit 4 is ended, and as a result, , The change in the amount of high frequency components appears earlier than in the conventional device, and in addition, the next focus voltage detection operation is based on the change in the amount of high frequency components that appears earlier based on the concentrated movement. In the present invention, the drop in the focus voltage can be detected quickly.

Now, assuming that the number set by the setting means 10 is two, which is equal to or less than the maximum number of three, when the counting means 11 counts two pulse signals. Then, the coincidence signal for stopping the operation of the oscillation circuit 7 and stopping the driving of the pulse motor 5 is output.

Therefore, the drive pulse signals supplied to the pulse motor 5 are concentrated and output immediately after the end point of the signal shown in FIG. 2 (e), as shown in FIG. 2 (f), for example.
Of course, the pulse motor 5 is driven according to the characteristics shown in FIG. 2 (f).

When the pulse motor 5 is driven, the focusing lens 1a also moves. Therefore, the focus voltage also fluctuates, and if the focus voltage has a magnitude relationship as shown in FIG. 2 (d), the timing signal I shown in FIG. By confirming the focus voltage H in (4), the motor drive control means 7 outputs a direction signal for reversing the drive direction of the pulse motor 5, and supplies it to the motor drive circuit 8 of the motor drive means 6.

Therefore, the motor drive means 6 drives the pulse motor 5 in the reverse direction from the drive pulse signal J shown in FIG. 2 to Z described in FIG.

Similarly to the conventional device described above, the driving of the pulse motor 5 is stopped at the time when the focusing lens 1a moves to the position where the focus voltage has reached the peak until then, so that a series of focusing is performed. The operation will end.

Now, here, the focus voltages of magnitude relations as shown in FIG. 2 (d) are obtained, and the focusing lens position and focusing in the mountain climbing type autofocus device according to the present invention when the above operation is performed Let's look at the relationship between the actual focus state characteristics of the image and the amount of high-frequency components.

First, regarding the position of the focusing lens 1a, in the focusing lens 1a of the present invention, as described above, the pulse motor 5 is driven by the drive pulse signal as shown in FIG. 2 (f), Since the movement will be concentrated immediately after the end of the focus voltage confirmation timing signal shown in FIG. 2 (e), the position may be concentrated in a short time or displaced for a while. It changes based on the characteristics as shown in FIG.

Next, the actual focus state characteristics of the image supplied to the image pickup tube are
Now, since the focus voltage having the magnitude relation as shown in FIG. 2 (d) can be obtained, and the characteristic of the amount of high frequency components is limited to two types as described later, the movement of the focusing lens 1a described above is performed. The characteristic is as shown by the solid line or the broken line in FIG.

Next, regarding the characteristics of the amount of high frequency components, a focus voltage having a magnitude relationship as shown in FIG. 2 (d) is obtained, and this focus voltage shows the amount of high frequency components in FIG. 2 (c). Considering that it is obtained by performing integration or peak hold in the screen gate signal output period, FIG.
Only two types shown in (i) with a solid line or a broken line can be considered.

This means that the characteristic of FIG. 2 (h) can be regarded as corresponding to the high frequency component of the video signal, so that the amount of high frequency component at an arbitrary time point is the characteristic of the characteristic of FIG. It is obvious from the above-mentioned amount that is integrated during the accumulation period T.

That is, the high frequency component amount M ₁ in FIG.
The characteristic from L ₁ point in (h) to L ₂ point before the period T can be regarded as an integrated amount, and the characteristic of FIG. 2 (h) shows the focus shown in FIG. 2 (g). Lens position, that is, Fig. 2
Considering that it corresponds to the drive pulse signal characteristic shown in (f) and the characteristic of the screen gate signal shown in FIG. 2 (c), the focus voltage of magnitude relationship as shown in FIG. 2 (d) is The characteristics of the amount of high frequency components that can be output can be considered only in the case of the two types shown in FIG. 2 (i). In other words, the above-mentioned arithmetic means 1
When the number of pulse signals that is larger than the maximum number calculated by 3 is supplied, the focus voltage at the timing indicated by H _-1 in FIG. It cannot be done.

Therefore, in the present invention as well, when the focus voltage as shown in FIG. 2 (d) is generated, the three relationships shown in (g), (h) and (i) of FIG. The state and the focusing lens position at that time are L, L'or K, K _{+ 1} , respectively, due to the accumulation action, rather than the peak state M or M'of the high frequency component amount.
As shown in (4), like the conventional device, it precedes.

However, the preceding state has a difference from the conventional device because the drive pulse signal for driving the pulse motor 5 is regulated as described above, that is, it is moved within the interval for detecting the focus voltage. Although the focus voltage in the state of moving a large amount is delayed, it can always be detected by the next detection operation. Therefore, in the example shown in FIG. 2, the focus position K of the focusing lens 1a or The mountain climbing type autofocus device according to the present invention has the following features in the driving state from K ₊₁ to the reverse rotation by the driving pulse signal indicated by J in FIG. 2 (f).

That is, as is clear from the relationship between FIGS. 2 (f) and 2 (g), the drive pulse signal J has a focus position K in the case where the amount of high-frequency components is a solid line or K _{+ in} the case of a broken line. _The 4th and 3rd pulse signals from the signal set to ₁ respectively.

Therefore, in comparison with the conventional device described with reference to FIG. 4, the focusing lens 1a has the drive pulse signal 1 in both the examples shown by the solid line and the broken line.
The reverse operation will be started earlier by the number of pieces. In other words, in the case of the autofocus device according to the present invention, the overrun from the in-focus position of the focusing lens 1a can be reduced by one drive pulse signal as compared with the conventional device.

As a result, the amount of "blurring" after passing the in-focus position is smaller than that in the conventional apparatus, and the uncomfortableness of the captured image can be improved.

The climbing type autofocus device according to the present invention has been described above based on the embodiment shown in FIG.
Considering the number of drive pulse signals for driving the pulse motor 5 in the setting means 10, the above-mentioned arithmetic means 1
It is needless to say that a more preferable device can be obtained by controlling the focus state depending on whether the focus state is close to or far from the focus position or by the set focal length of the lens device 1 in addition to the maximum number by 3.

Considering the example described above, for example, the focus voltage level information indicating the in-focus state is shown by the focus voltage detection means 3, and the focal length information is shown by the broken line in FIG. As described above, when the in-focus state is largely deviated from the in-focus state, the setting number is set to three, and as the in-focus state is approached, two or one is sequentially developed or set. By considering the development in which the set number is increased as the focal length is shorter, independently or in association with each other, the driving characteristic of the focusing lens 1a to the in-focus position is less in the "blurred" state of the captured image. It can be a property.

In view of the above-mentioned concept of the maximum number, for example, a development in which the number of drive pulse signals to be supplied to the pulse motor 5 in advance is limited to the maximum number described above is also conceivable as another embodiment.

That is, as shown in FIG. 3, the control means 14 for controlling the drive start and the number of supply of the drive pulse signal to the pulse motor 5 to control the drive of the pulse motor 5 includes the above-mentioned motor drive control means 9 and Only a predetermined number of pulse signals satisfying the above-mentioned maximum number of conditional expressions for driving the pulse motor in a predetermined direction by supplying a start signal and a direction signal from the motor drive control means 9 are output as drive pulse signals. An embodiment constituted by the motor drive means 15 is also conceivable.

By doing so, the respective units shown by reference numerals 10, 11, 12, and 13 can be omitted, and therefore, although the number control or the like according to the in-focus state cannot be performed, the device configuration can be simplified, that is, In some cases, it may be possible to provide a device that can be considered more practical.

The mountain climbing type autofocus device using the pulse motor as the drive source of the focusing lens according to the present invention drives the pulse motor from the end of the operation of the differential circuit to the start of the next focus voltage detection operation. Since it is concentrated on the period, the delay of the detection of the high frequency component amount of the video signal due to the accumulation action is minimized, that is, the fluctuation of the high frequency component amount due to the concentrated driving is always detected immediately after the concentrated driving. Therefore, the drop of the focus voltage can be detected quickly, the overrun from the in-focus position of the focusing lens can be minimized, the blur amount from the in-focus state can be reduced, and the captured image is unsightly. It has the effect of improving the quality.

[Brief description of drawings]

FIG. 1 is a block diagram of one embodiment of a mountain climbing type autofocus device according to the present invention, FIG. 2 is a schematic waveform diagram for explaining the operation of the embodiment shown in FIG. 1, and FIG. 3 is the present invention. FIG. 4 is a block diagram of another embodiment of the present invention, and FIGS. 4 and 5 are schematic waveform diagrams for explaining the operation of the conventional apparatus. 1 ... Lens device, 2 ... Camera device, 3 ... Focus voltage detection means, 4 ... Difference circuit, 5 ... Pulse motor, 6 ...
... motor drive means, 7 ... oscillation circuit, 8 ... motor drive circuit, 9 ... motor drive control means, 10 ... setting means,
11 ... Counting means, 12 ... Comparison means, 13 ... Calculation means, 14 ... Control means, 15 ... Motor drive means.

Claims (3)

[Claims] 1. A focusing lens is detected by detecting a focus voltage from a high frequency component in a predetermined screen area of a video signal output from a camera device upon receiving an image formed by a mounted lens device, and confirming and detecting increase or decrease of the focus voltage. The drive of the pulse motor, which is the drive source, is controlled to move the focusing lens in a predetermined direction, and when the peak value of the focus voltage is obtained, the drive of the pulse motor is stopped to In the mountain climbing type autofocus device that stops the movement, the supply of the drive pulse signal for driving the pulse motor is started in synchronization with the confirmation of the focus voltage and the end of the increase / decrease detection operation, and the number of supply is set to the drive number. The period of the pulse signal is t ₀ , the focus voltage confirmation and increase / decrease detection operation period is t ₁ , and the pause period in which the focus voltage is not detected is t _2. , Period _{t 3} when the pulse motor by the supply of the drive pulse signal is actually driven, if any integer and the A, becomes _{{(A-1) t 0} + t 3} ÷ 2 + t 1 <t 2/2 A mountain climbing type autofocus device comprising control means for making the maximum integer A or less that satisfies the conditional expression. 2. The motor driving means having an oscillating circuit for outputting a synchronous pulse signal including a shortest period capable of driving the pulse motor as a driving pulse signal for driving the pulse motor forward and reverse, and a focus voltage. Of the motor drive means in synchronization with the direction signal for instructing the drive direction of the pulse motor and the end of the confirmation and increase / decrease detection operation. The motor drive control means for outputting a start signal to start the motor drive means and the pulse motor between the end time of the confirmation and increase / decrease detection operation and the start time of the next focus voltage detection operation. Setting means for setting the number of drive pulse signals to be supplied to an arbitrary number less than or equal to the maximum number based on the supplied maximum number signal; Is reset by, the counting means for counting the number of drive signals supplied from the motor driving means to the pulse motor and the setting content by the setting means and the counting content by the counting means are compared, and when both are coincident, a comparing means for stopping the supply of the drive pulse signal to the pulse motor by the motor driving means, condition _{{(a-1) t 0} + t 3} ÷ 2 + t 1 < maximum integer allowed to establish t _2/2 The mountain climbing type autofocus according to claim 1, further comprising: an arithmetic unit that calculates A as the maximum number, outputs a maximum number signal corresponding to the maximum integer A, and supplies the maximum number signal to the setting unit. apparatus. 3. A motor drive that receives a detection output of an increase / decrease in a focus voltage, starts operation, and generates a direction signal that determines a drive direction of a pulse motor and a start signal that starts the drive of the pulse motor. Oscillation for outputting a number of pulse signals having a predetermined period equal to or longer than the shortest period capable of driving the pulse motor as a drive pulse signal for rotating the pulse motor forward and backward in advance, the number being equal to or less than a maximum integer A that satisfies the conditional expression in advance. The mountain climbing type autofocus device according to claim 1, comprising a circuit and a motor drive circuit that drives the pulse motor according to a pulse signal output from the oscillation circuit.