JP3296688B2 - Auto focus video camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera and an electronic still camera having an automatic focusing function.

[0002]

2. Description of the Related Art Conventionally, in an automatic focusing device used for an imaging device such as a video camera, a method of using a video signal itself obtained from an imaging device for evaluating a focus control state has been awarded. Such a method has many excellent features such as essentially no parallax and accurate focusing even when the depth of field is small or the subject is located at a distant place. are doing. Moreover, according to this method, there is no need to separately provide a special sensor for autofocus, and the mechanism is extremely simple.

As an example of such a focus control method using a video signal, a control method called a so-called hill-climbing servo method has been conventionally known. An auto-focusing device using the hill-climbing servo system is described in, for example, Japanese Patent Application Laid-Open No. Sho 63-215268 (H04N5 / 232). Set the integral value of the field period to 1
The focus evaluation value is detected for each field, and this focus evaluation value is constantly compared with that of one field before, and the focus lens position is continuously displaced minutely so that the focus evaluation value always takes the maximum value. Is to be detected and held.

In the prior art, as a means for changing a relative position of a lens with respect to an image pickup element in an optical axis direction, a motor such as a stepping motor or a DC motor, and a rotational force obtained by driving the motor are used to change the lens or the image pickup element. And a driving force transmitting mechanism that converts the driving force into a driving force for linear movement, it is difficult to reduce the size and weight of the mechanism, and power consumption becomes a problem.

Therefore, by displacing the lens or the image pickup device with a linear motor, the size and weight of the mechanism can be reduced, and the power consumption can be further reduced. FIG. 4 illustrates a case where a linear motor is used as the driving source.

In FIG. 4, a focus adjusting device of a video camera is configured to adjust a focus by moving an image pickup element in a direction of an optical axis by a voice coil motor. In the following description, the CCD 2 and the CCD are integrated. The member which is displaced in the direction is a movable portion.

The operation will be described more specifically.
The image formed by is photoelectrically converted by the CCD 2,
The imaging output is converted into a video signal by the imaging circuit 3, amplified to a predetermined level by the amplification circuit 4, supplied to the recording system of the VTR, and input to the focus evaluation value generation circuit 5.

As shown in FIG. 17, a focus evaluation value generating circuit 5 includes a high-pass filter (HPF) 5a for extracting a high frequency component of a video signal, an A / D converter 5b for converting the output of the HPF 5a into a digital value. , A gate circuit 5c for passing only the value in the focus area set at the center of the screen in the A / D conversion output, and a digital integrator 5d for digitally integrating the gate output over one field period. The output of the evaluation value generation circuit 5 is
The digital integrated value of the high frequency component of the video signal over one field period is output to the arithmetic unit 6 and the memory 50 at the subsequent stage as a focus evaluation value.

The arithmetic unit 6 generates a drive signal of a voltage level m as an initial state to displace the CCD 2 in one direction on the optical axis, and stores the latest focus evaluation value from the focus evaluation value generation circuit 5 and the memory 50. The in-focus state of the imaging screen is determined by comparing the stored focus evaluation value one field before, and if the latest focus evaluation value is larger, it is determined that there is a focus position in the current moving direction. The drive signal of the voltage level m is continuously output. Conversely, if the focus evaluation value one field before is larger, the drive signal is determined to be moving away from the focus position and the voltage level of the drive signal is changed from m. instead of n
By reversing the transition direction of D2, the CCD 2 is brought to the in-focus position where the focus evaluation value becomes the maximum.

Note that the CCD 2 moves in the direction in which the focus evaluation value increases.
When the focus evaluation value decreases due to excessive movement of the focus position at which the focus evaluation value becomes the maximum, the moving direction of the CCD 2 is reversed, and the operation signal is returned to the position where the maximum value is obtained. Emits.

A focus evaluation value one field before the latest field is stored in the memory 50. When the comparison operation in the arithmetic unit 6 is completed, the latest focus evaluation value obtained from the focus evaluation value generation circuit 5 is used. The stored contents are updated.

A voice coil motor 53, which is a driving source of a movable portion including the CCD 2, is a type of linear motor and has a structure as shown in FIGS. 5 and 14 (a cross-sectional view taken along the line CC 'in FIG. 5). Basically, it has the same structural principle as a round speaker. That is, four center yokes 23 each having a U-shaped cross section are fixed to the yoke fixing portion 90a of the fixing base 90 of the camera unit of the video camera along four sides of a square. A permanent magnet 24 having one magnetic pole is fixed to the inner surface of the yoke 23. A shaft mounting plate 91 is fixed to the camera unit in parallel with the yoke fixing portion 90a. One end of two guide shafts 51a and 51b extending in the optical axis direction is connected to the mounting plate 91. The end is connected to the yoke fixing part 60a.

Further, lenses 81 and 82 are fixed between the center yoke 23 and the opening 90e of the fixed base 90.

On the other hand, a movable rectangular tube bobbin 22 having a conductive wire wound as a drive coil (voice coil) 20 is fixed so as to protrude along the optical axis so as to face each of the permanent magnets 24. A base 52 is disposed in the unit, and fitting holes 52a, 52b are provided on a diagonal line of the movable base 52.
Is formed, and the movable base 52 is supported so as to be able to advance and retreat in the optical axis direction in the camera unit by fitting the guide shafts 51a and 51b into the fitting holes 52a and 52b, respectively. An opening 52c for allowing incident light to pass therethrough is provided at the front of the movable base 52 (closer to the lens).
Are formed, and the CCD 2 is fixed to the rear part (the side farther from the lens). Reference numerals 83, 84, and 85 denote optical filters, such as infrared cut filters and optical LPFs, respectively, disposed in front of the CCD in a normal video camera. Incident light passing through the lenses 81 and 82 passes through the opening 52c. The light passes through the optical filters 83, 84, 85 to reach the CCD 2 and is imaged on the CCD.

When a current flows through the drive coil 20, the drive coil 20, the bobbin 22, the movable base 52, and the CCD 2
Are moved by the guide shafts 51a and 51b as the movable part 60 and move integrally in the optical axis direction indicated by the arrow.

Here, the drive signal to the voice coil motor 53 has the following characteristics. That is, in the voice coil motor 53, the driving direction of the bobbin 22 changes according to the direction of the current flowing through the driving coil 20, and the driving speed changes according to the magnitude of the current. Therefore, in order to drive and control the voice coil motor 53 by the output of the arithmetic unit 6, a constant reference voltage VR is applied to one of the drive coils 20 as shown in FIG.
EF is applied, and the driving voltage VD, which is the voltage of the driving signal from the arithmetic unit 6, is applied to the other, and the direction and magnitude of the current may be changed according to the magnitude relationship of VD with respect to VREF.

By the way, in the example shown in FIG. 4, only the coil 20 is shown for simplification,
The other parts of 3 are not shown.

[0018]

However, as described above, a linear motor is used as a drive source for a CCD,
The automatic focusing apparatus of the type in which the focal point is adjusted by moving the focal point in the direction of the optical axis has the following disadvantages.

That is, this drawback is a problem in that a driving load is generated on the movable portion due to various factors, and the load often changes in accordance with the position of the movable portion 60. Therefore, under such conditions, the state of the external force applied to the movable part 60 including the CCD 2 greatly differs depending on the position of the movable part. As a result, even if the same drive signal is applied, the movable part 60 operates in the same manner at all positions. It becomes difficult to make it.

This phenomenon will be described in detail with reference to FIGS. 6, 7 and 8. FIG. 6 shows a case where the movable unit 60 is held in a horizontal state. In this state, as shown in FIG. 7A, as the drive signal, for example, the drive voltage V whose direction is switched at regular time intervals with an absolute value equal to the reference voltage VREF.
When D is added, thrusts Ftl and Ftr having the same magnitude in the leftward and rightward directions in the horizontal direction and differing in directions by 180 ° are applied. Assuming that no driving load acts on the movable part 60, only the thrusts acting in the displacement direction of the movable part 60 are present. Therefore, the position of the movable part changes symmetrically as shown in FIG. 7B. . Note that the vertical axis in FIGS. 7B and 8B indicates the distance from the reference position P0 shown in FIG.

Here, the driving load acting on the movable portion will be considered. In FIG. 5, the CCD 2 fixed to the movable section 60 has a lead section 70 for inputting and outputting signals to and from the outside.
Since the lead 70 is made of a magnetic material, it receives an attractive force Fmg leftward from the permanent magnet 24. A cable 71 is attached to the movable portion 60 via a lead portion 70 for receiving and supplying a signal to the CCD 2. The cable 71 is usually formed of a flexible printed circuit board having elasticity. Cable 71 as shown
When the cable 71 is connected to the right side of D2 and bent so as to be fixed to the upper surface of the fixed base 90 through the opening 90d formed in the fixed base 90, the elastic force Fk of the cable 71 is obtained. Occurs to the left. Therefore, when the voice coil motor 53, the movable unit 60, and the cable 71 are arranged as shown in FIG. 5, a driving load (Fmg + Fk) acts on the movable unit 60 to the left.

FIG. 8 shows the same driving voltage V in FIG.
D is applied. In the displacement direction of the movable part 60, a driving load (Fmg + Fk) acts in addition to the thrusts Ftl and Ftr, and as a result, the combined force (Ftl + Fmg +
Fk) and the synthetic force (Ftr-Fmg-F
k) will work. Therefore, the amount of movement to the left in a certain time is larger than when no load is applied, and conversely, the amount of movement to the right is smaller, and the position of the movable part is shifted to the left as shown in FIG. become.

[0023]

SUMMARY OF THE INVENTION The present invention is directed to a linear motor for displacing an image sensor in a direction of an optical axis with respect to a lens, and a focus control for supplying a drive signal to the linear motor so that the image sensor moves toward a focus position. Means, a load calculating means for calculating a load amount of a driving load acting on the image sensor in the optical axis direction, and a level correcting means for correcting a level of the driving signal in accordance with the load amount. An image pickup device position detecting means for detecting a position of the device in the optical axis direction is provided, and a load amount is calculated based on a calculation formula set in advance as a function of the position.

Further, there are provided position predicting means for predicting a position at which the image sensor reaches after a predetermined time by the driving force of the linear motor, and comparing means for comparing the output of the image sensor position detecting means with the output of the position predicting means. It is characterized in that the load amount is calculated on the basis of this.

The driving load is a magnetic force generated between a magnetic body disposed on the image sensor and a magnet constituting the linear motor, or a signal for transmitting and receiving signals between the image sensor and a signal processing circuit board fixed in the cabinet. It is based on the elastic force of a cable having elasticity.

[0026] Further, a plurality of factors for generating a driving load are arranged in a direction in which the loads cancel each other, thereby reducing the amount of load. More specifically, the magnetic force is reduced by the cable. A cable is connected to the image sensor so as to cancel by an elastic force.

[0027]

Since the present invention is constructed as described above, even if a load is applied to the movable part by a magnetic attraction between the CCD and the linear motor or an elastic force of a cable connected to the CCD, these loads are applied. The linear motor is driven so as to remove it, and the movable part operates in the same manner as when there is no load.

Also, by devising the arrangement of the load factors,
The load of the suction force and the load of the elastic force cancel each other, and the load finally acting on the movable portion can be reduced.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. In addition, the same reference numerals are given to the same portions as those of the above-described conventional technology, and the description is omitted. FIG. 1 is a circuit block diagram of an automatic focusing apparatus for a video camera according to a first embodiment.

A driving signal for displacing the CCD 2 by a predetermined amount in the direction in which the focus evaluation value increases from the arithmetic unit 6 is input to the position prediction circuit 31. Before describing the position prediction operation in the position prediction circuit 31, the relationship between the drive signal level and the amount of movement of the movable unit 60 will be described.

When the difference between the drive voltage VD and the reference voltage VREF is large and a large amount of current flows through the drive coil 20, the thrust of the voice coil motor 53 increases, and the amount of movement per unit time increases.

If the relationship between the drive voltage and the amount of movement is obtained in advance theoretically or experimentally, the position of the movable section after a unit time can be predicted according to the drive signal level. That is, in the voice coil motor 53, since the drive voltage and the position of the movable part after a unit time are in a proportional relationship, the predicted position Pp after a certain time with respect to the drive voltage VD can be known as shown in FIG.

In the position prediction circuit 31, in this manner,
Based on the input drive voltage VD, the position Pp of the movable unit 60 after a predetermined time t has elapsed is predicted. The predicted position Pp thus predicted is input to the memory 32 and held until a predetermined time t elapses. When the predetermined time t elapses, the predicted position Pp stored in the memory 32 is input to the arithmetic circuit 33.

On the other hand, a position detector 30 for detecting the actual position of the movable unit 60 in the optical axis direction is attached near the movable unit 60 along the movement path. Actual position (actually measured position) detected by
Pr is input to the arithmetic circuit 33.

In the arithmetic circuit 33, the driving voltage V
The position of the movable unit 60 immediately before the predetermined time is set by D is input to the position detector 30 as the initial position Vi, and the movement amount Kp of the movable unit predicted by receiving data on the predicted position Pp becomes Kp = | Pp. −Pi |. Similarly, by receiving data on the actual measurement position Pr, the actual movement amount Kr is calculated as Kr = | Pr-Pi |. When the predicted value Kp and the actually measured value Kr of the movement amount are calculated in this way, the difference between them, that is, Dpr = Kr-Kp = |
Pr−Pi | − | Pp−Pi | is calculated as the difference in the movement amount.

The position detector 30 is, specifically, an LED 97 mounted on the bottom surface of the movable base 52 of the movable portion 60 and an optical sensor 98 fixed to the bottom inner surface of the fixed base 90 so as to face the LED 97. And LE
The position of the movable part 60 in the optical axis direction can be detected by irradiating the light from the D 97 to the position of the optical sensor 98.

Dpr calculated in this way is used as a value corresponding to the driving load in the optical axis direction as a bias determination circuit 3 in the subsequent stage.
6 is input.

Here, the relationship between the difference Dpr and the driving load will be described. Now, assuming that the difference Dpr in the movement amount is almost zero as shown in FIG. 10, since Pp = Pr, it is considered that no load acts on the movable part 60. FIG.
In FIGS. 0 to 12, the initial position corresponds to the position of the movable unit 60 before a fixed time t, and the measured position is the actual position of the movable unit 60 from the initial position by the drive signal from the arithmetic unit 6 after the fixed time t has elapsed. The position corresponds to the actual position when the displacement is completed (the distance from the initial position is referred to as an actually measured position Pr), and the predicted position is the position prediction circuit 3 when the movable unit 60 is at the initial position.
1 corresponds to a position predicted to be located after a predetermined time t (a distance from the initial position is referred to as a predicted position Pp).

Next, assuming that the difference Dpr is positive, the actual movement amount Kr> the predicted movement amount Kp, so that the thrust and the driving load of the voice coil motor act in the same direction as shown in FIG. It is thought that there is. Further, if the difference Dpr between the predicted position Pp and the actually measured position Pr is negative,
Since Kp> Kr, it is considered that the thrust and the driving load of the voice coil motor act in opposite directions as shown in FIG. Also, the absolute value of the difference between the movement amounts | Dpr | = | Kr−
It is considered that the drive load increases as Kp | increases. By determining the magnitude relationship and difference between the predicted position and the actually measured position in this way, it is possible to estimate the state of the drive load acting on the movable unit 60.

The bias determination circuit 36 generates a correction signal according to the value of the difference Dpr, and corrects the drive signal by superimposing the voltage of the correction signal on the drive signal output from the arithmetic unit 6. FIG. 13 shows the operation of correcting the drive signal.

In the bias determination circuit 36, the input difference D
A correction signal Vc, which is a DC voltage signal, is output according to pr. This bias determination circuit 36, as shown in FIG.
The purpose of the present invention is to modify the drive signal in order to solve the problem that the amount of movement of the movable unit 60 is different even if the drive signal output from the arithmetic unit 6 is the same depending on the moving direction due to the influence of the drive load. Specifically, the reference voltage V
The correction voltage V is obtained by adding a voltage value proportional to the difference Dpr to REF.
c, in other words, Vc = VREF + a × Dpr
The correction voltage Vc as shown in FIG.
The correction signal Vc is superimposed on the drive signal VD by the adder 38 to generate a new drive signal VD1.
Here, a is a coefficient (positive value), and the optimum value is selected in advance by an experiment.

For example, when the movable part 60 is moved in the same direction as the direction in which the driving load is applied as shown in FIG. 11, Dpr is a positive value, and therefore, the correction voltage Vc as shown in FIG. Becomes higher than the reference voltage VREF as the driving load increases, and this level is higher than the driving signal VD.
13C, the driving signal VD1 is level-shifted relatively upward with respect to the reference signal VREF as shown in FIG. 13C, and the potential difference applied to both ends of the coil 20 when moving to the right is large. As a result, the moving amount of the movable portion 60 overcomes the action of the driving load and increases, and conversely, the potential difference when moving to the left decreases, and the moving amount decreases by suppressing the action of the driving load. Voltage of the drive signal of the heater 6
When D is the same, the same moving amount as in the state without the driving load can be secured.

As a result, the drive signal VD includes the reference voltage VRE.
A bias is applied to F, and a displacement equivalent to that at the time of no load is given to the movable unit 60 without causing a difference between the leftward movement amount and the rightward movement amount due to the driving load acting on the movable unit 60. be able to. In FIG. 13, the voltage level of the drive signal from the arithmetic unit 6 is changed to the reference voltage VR as shown in FIG.
The level is periodically changed with respect to the EF, but this is merely for the purpose of explaining the correction operation. During the actual focusing operation, the focus evaluation value tends to increase and the lens is moved in one direction. During this time, a drive signal of a certain level is output from the arithmetic unit 6, and when the moving direction is changed, the level becomes a polarity opposite to the reference level VREF.

The fixed time t is equal to one field period (1 /
60SEC), and during a period in which a certain driving voltage VD determined based on a focus evaluation value in a certain field is output from the arithmetic unit 6, the bias determination for this driving voltage is completed. Further, the bias determination operation may be performed a plurality of times in one field period.

In this embodiment, the method of detecting the driving load and correcting the moving amount when the movable section 60 is in the active state has been described. However, even when the movable section 60 is stopped, the predicted position is equal to the initial position. Accordingly, when a driving load is applied, the same operation as when there is no load, that is, a stationary operation at a fixed position can be realized.

In the above embodiment, the case where the direction of the drive load of the attraction force by the magnetic force between the permanent magnet and the lead portion is the same as the direction of the drive load of the elastic force of the cable has been described. By acting so as to cancel each other, it is possible to minimize the above-described correction operation. Therefore, as a second embodiment, as shown in FIG. 2, if the cable 71 is bent to the left from the connection portion side with the CCD 2 and pulled out so as to be fixed on the upper surface of the fixed base 90,
The driving loads Fmg and Fk work in opposite directions by 180 °, and as a result, the resultant force (Fmg + Fk) can be significantly reduced as compared with the case where the driving loads work in the same direction.

Also, if the cable 71 is pulled straight out upward to avoid bending as much as possible, or if the material of the cable 71 itself is selected to have a weak elasticity, the driving load due to the elastic force of the cable 71 is reduced as much as possible. As a result, only the driving load due to the suction force needs to be considered. In this case, the position detector 3
By substituting the position data from 0 into a predetermined calculation formula to calculate the driving load due to the attraction force, and applying a bias to the driving signal as much as possible to cancel this load, it is also possible to realize a driving load measure. it can. Such a configuration will be described below as a third embodiment.

Here, the relationship between the position of the movable portion 60 in the optical axis direction and the driving load due to the attractive force generated between the permanent magnet 24 and the lead portion 70 will be described with reference to FIGS. First, for the sake of simplicity, attention is focused on one of the four permanent magnets 24. As shown in FIG. 15, a point at which a magnetic force acts on the permanent magnet 24 is defined as a middle point A in the optical axis direction. Part 70
The point at which the magnetic force acts on is defined as the midpoint B in the direction (vertical direction) perpendicular to the optical axis direction, and the attraction force generated between the permanent magnet 24 and the lead portion 70 is generated between AB.

FIG. 1 shows the positional relationship between points A and B.
6. In FIG. 16, the distance d between the point A and the optical axis, that is, the distance between the permanent magnet 24 and the optical axis and the position P0 in the optical axis direction of the point A are set in advance when designing the camera unit. Let L, A be the distance in the optical axis direction between points AB.
The distance between B and r is the angle, and the angle between the line connecting AB and the optical axis is θ
Further, assuming that the magnetic permeability of the air in which the camera unit exists is μ, the magnetic pole strength of the permanent magnet 24 is m1, and the magnetic pole strength of the magnetized lead 70 is m2, the point B is directed toward the point A. The acting force F can be calculated as Equation 1 according to Coulomb's law.

[0050]

(Equation 1)

As is apparent from FIG. 16, the distances d and L correspond to the lengths of the two sides of the right triangle, respectively, so that Equation 2 holds.

[0052]

(Equation 2)

The driving load of the movable unit 60 corresponds to the component F × cos θ of the force F in the optical axis direction. By substituting Equations 1 and 2 into this equation, Equation 3 is derived.

[0054]

(Equation 3)

Further, since the four permanent magnets 24 are provided, the component of the force acting on the lead portion 70 in the optical axis direction is four times the formula (3). Become like

[0056]

(Equation 4)

In equation (4), all values other than the distance L are preset values at the time of design, and only the distance L becomes a variable as the movable section 60 moves in the optical axis direction. In other words, if the distance L is detected, the driving load Fm is calculated from Equation 4.

In the above-described calculation formula, only the middle point B on the optical axis is focused on the lead portion 70 of the CCD 2, but actually there are a plurality of lead portions 70, and the same calculation is performed for each lead portion. However, even if the midpoint B is calculated as an average position, no significant difference occurs.

The third embodiment shown in FIG. 3 will be described based on the above. In FIG. 3, a position detector 130 having the same configuration as that of the position detector 30 of FIG. 1 is provided. In this position detector 130, the position of the lead 70 of the CCD 2 in the optical axis direction is accurately determined. FIG. 15
As is clear, the LE fixed to the movable base 52
D197 is arranged on a straight line perpendicular to the optical axis where the lead part 70 exists.

The lead 70 from the position detector 130
Is input to the load calculation circuit 34, and a distance P is calculated by subtracting a preset position P0 of the point A in the optical axis direction from the position Pl, that is, L = P1−P0. The driving load amount Fm is calculated by substituting the value of the distance L into Expression 4, and is input to the bias determination circuit 136.

The bias to be applied is prepared in advance in the bias determination circuit 136 in accordance with the drive load amount by experiment. Therefore, when the drive load amount is input from the load calculation circuit 34, the necessary bias is determined. The correction signal Vc is applied as a bias to the drive signal VD by the adder 38.

[0062]

As described above, according to the present invention, the influence of the driving load inevitably generated in the auto-focus device of the type in which the CCD is moved in the optical axis direction by the linear motor to perform the focus adjustment is suppressed, Can be operated in the same manner as when no load is applied, so that the problem that the moving amount of the CCD moving per unit time varies depending on the moving direction can be solved.

Further, by simply detecting the position of the CCD in the optical axis direction, it is possible to easily calculate the drive addition amount, and it is possible to suppress the influence of the drive load with an extremely simple configuration.

Further, even when there are a plurality of driving load generation factors, by devising the arrangement, the driving loads cancel each other out, and the load finally acting on the CCD can be minimized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a camera unit according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a third embodiment of the present invention.

FIG. 4 is a block diagram of a conventional example.

FIG. 5 is a structural explanatory view of a camera unit according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating a thrust generated when the movable unit is held in a horizontal state.

7 is a diagram illustrating a positional relationship between a drive signal and a movable unit in the case of FIG. 6;

FIG. 8 is a diagram illustrating a positional relationship between a drive signal and a movable unit when an external force acts on the movable unit.

FIG. 9 is a diagram showing a positional relationship between a driving voltage and a movable unit according to the first embodiment of the present invention.

FIG. 10 is a diagram illustrating a relationship between a predicted position and a measured position when a driving load does not act on a movable unit according to the first embodiment of the present invention.

FIG. 11 is a diagram illustrating a relationship between a predicted position and a measured position when the movable unit is moved in the same direction as the driving load according to the first embodiment of the present invention.

FIG. 12 is a diagram illustrating a relationship between a predicted position and a measured position when the movable unit is moved in a direction opposite to the driving load, according to the first embodiment of the present invention.

FIG. 13 is a timing chart when a drive signal is modified according to the first embodiment of the present invention.

FIG. 14 is a structural explanatory view of the voice coil motor according to the first embodiment of the present invention.

FIG. 15 is a structural explanatory view of a camera unit according to a third embodiment of the present invention.

FIG. 16 is a diagram illustrating a driving load due to a suction force according to the third embodiment of the present invention.

FIG. 17 is a main part block diagram of the first embodiment of the present invention.

[Explanation of symbols]

 81 Lens 2 CCD 53 Voice coil motor 52 Movable base 6 Calculator 30 Position detector 130 Position detector 31 Position prediction circuit 33 Calculation circuit 36 Bias determination circuit 24 Permanent magnet 70 Lead unit 71 Cable

Claims (1)

(57) [Claims] An imaging device that photoelectrically converts light incident through a lens; a linear motor that displaces the imaging device in an optical axis direction with respect to the lens; and an imaging device that moves toward an in-focus position. Focus control means for supplying a drive signal to the linear motor; image sensor position detecting means for detecting the position of the image sensor in the optical axis direction; and a position at which the image sensor reaches after a predetermined time by the driving force of the linear motor A position predicting means for predicting the output of the image sensor, a comparing means for comparing the output of the image sensor position detecting means with the output of the position predicting means, and a level correcting means for correcting the level of the drive signal according to the output of the comparing means. Focus video camera.