JPH04331907A - Lens position controller - Google Patents

Abstract

PURPOSE:To offer the lens position controller which obtain high positioning precision even when a position detecting means which easily causes output variation depending upon the circumferential state and hardly performs precise control over a lens position is used although various lens position detecting means are used for the lens position controller mounted on a camera, etc. CONSTITUTION:The lens position controller is provided with 1st and 2nd correction data memories 13 and 16 as storage means stored with characteristics of at least one of a lens moving means and a lens position detecting means and while at least one of the output of the position detecting means and a control signal supplied to the lens moving means is corrected according to the characteristics, the lens moving means is controlled by a CPU 7. Consequently, even if the output of a lens position detection device varies to contain an error, the error exerts no adverse influence and invariably high-accuracy lens position control becomes possible.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens position control device for an imaging optical system in a silver halide photographic camera, a still video camera, a video camera, etc.

0002

2. Description of the Related Art Conventionally, there have been various types of lens position detection means for lens position control devices, such as optical type and electric type. Optical types include photointerrupters, photocouplers, etc. In addition, electric types include potentiometer, capacitance type,
There are grayscale etc.

0003

[Problems to be Solved by the Invention] In the conventional lens position detection means, it is difficult to
Its characteristics change depending on manufacturing conditions and other factors.

[0004] In a photointerrupter and a gray scale, the characteristics change depending on the change in shape. In the electrocapacitive type, the dielectric constant between the electrodes changes depending on temperature and humidity, and the characteristics change because the shape of the electrodes and the spacing between the electrodes differ depending on the manufacturing state. Further, potentiometers and photocouplers also change depending on the environment, and the characteristics of output changes depending on position also change depending on manufacturing conditions.

On the other hand, imaging optical systems in recent years have tended to become smaller, and higher precision is now required for lens position control.

However, when conventional lens position detection means are used to control the lens position, the characteristics of the position detection means change due to the reasons described above, so there is a drawback that the accuracy of stopping the lens cannot be increased. .

The present invention has been made in view of the above problem, and it is possible to achieve high precision lens positioning without changing the configuration of the conventional device, and in particular, without being influenced by changes in characteristics due to the manufacturing state of the position detection means. The purpose is to provide a control device.

[0008]

[Means for Solving the Problems] The lens position control device of the present invention includes means for storing the characteristics of at least one of the lens moving means and the lens position detecting means, and the output of the position detecting means and the lens Since the lens moving means is controlled while at least one of the control signals given to the moving means is corrected according to the characteristics, even if the output of the position detecting means includes an error, a highly accurate lens can be maintained. Position control becomes possible.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a video camera will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a variator that moves in the optical axis direction to perform a magnification change action. When the zoom switch 2 is pressed, a signal is sent to the zoom motor driver 3, which drives the zoom motor 4. to move in the direction of the optical axis. 5
is an automatic focusing device that detects the value of a high frequency component of a signal from an imaging member 6 such as a CCD and outputs a focus signal. C
The PU 7 sends a signal to the focus motor driver 9 and drives the focus motor 10 in order to move the focus lens 8 so that the focus signal becomes the maximum value.

Reference numeral 11 denotes a zoom encoder, in which a contactor that moves together with the variator 1 changes the point of contact with an electrical resistor, thereby changing the resistance value between the terminals. A zoom encoder reading circuit 12 detects the voltage change due to the resistance value change.
, the CPU 7 detects the first correction data memory 1
3 to detect the position of the variator 1. 1
4 is a focus encoder, and a focus lens 8
A first electrode is provided on the outside of the focus lens holding frame that moves with the lens, a second electrode is provided on the inside of the fixed lens barrel, and the facing area of the first electrode and the second electrode is changed. , the capacitance between the first and second electrodes changes. The electric capacitance is read by a focus encoder circuit 1
5, the CPU detects it by the second correction data memory 16.
The position of the focus lens 8 is detected by comparing the contents.

FIG. 2 shows an enlarged view of a portion of the focus encoder 14. A lens frame 101 holds a lens (not shown) inside and is movable in the optical axis direction, and a first electrode 103 is formed on the outside thereof. 103
is a fixed lens barrel, and a second electrode 104 is formed inside thereof. FIG. 3 is a diagram showing characteristics when an encoder like the one shown in FIG. 2 is actually manufactured. The horizontal axis represents the focus lens position, and the vertical axis represents the output level of the position signal. The design value or desired output characteristic is as shown by the broken line A, but the actual output characteristic is as shown by the solid line B due to variations in electrode shape, electrode spacing, etc. due to manufacturing errors.

Therefore, in the present invention, the difference between the broken line A and the solid line B in FIG. By calculating in , the accurate focus lens position can be determined. ROM that stores data
If a large number of correction data cannot be stored due to the small capacity of the first correction data memory 13, several reference positions of the focus lens are determined as the contents of the first correction data memory 13, and the difference between the broken line A and the solid line B at the reference positions is calculated. Said first correction data memory 1
3, and the CPU 7 calculates correction data at positions between the reference positions by interpolation calculation. Alternatively, an arithmetic expression or constant for calculating the difference between the broken line A and the solid line B may be stored as correction data in the correction data memory 16, and the CPU 7 may calculate the correction data.

FIG. 4 shows an enlarged view of the zoom encoder 11. 151 is a resistor, and when the contact 152 moves in the optical axis direction together with the variator 1, the voltage applied from a DC power source (not shown) between the terminals 153 and 154 is divided and output to the terminal 155. do. Figure 5 shows
The characteristics of the resistance value between the terminal 153 and the terminal 155 and the variator position are shown. The horizontal axis shows the variator position, and the vertical axis shows the resistance value between the terminals 153 and 155, respectively. The design value or desired output characteristic is as shown by the broken line A', but the actual resistance value is as shown by the solid line B' due to variations in the resistivity distribution of the resistor due to manufacturing errors.

Therefore, in the present invention, the broken line A' in FIG.
The difference between and the solid line B' is stored in advance as correction data in the first correction data memory 13, and the CPU 7 calculates the resistance value at the design value from the output of the zoom encoder, thereby obtaining an accurate resistance value. Accurate variator position is now required. ROM that stores data
If a large number of correction data cannot be stored due to the small capacity of the first correction data memory 13, several reference positions of the variator are determined as the contents of the first correction data memory 13, and the broken line A' and the solid line B' at the reference positions are The difference between the reference positions may be stored in the first correction data memory 13, and the CPU 7 may calculate correction data at positions between the reference positions by interpolation. Alternatively, an arithmetic expression or constant for calculating the difference between the broken line A' and the solid line B' may be stored as correction data in the second correction data memory 16, and the CPU 7 may calculate the correction data.

With the above configuration, the lens position can be detected accurately, so that highly accurate lens position control can be performed. Note that the focus encoder and variator encoder may have opposite configurations,
Further, the present invention is not limited to a focus lens and a variator, and may be used for other movable lenses.

FIG. 6 shows a second embodiment of the present invention in which a photocoupler is used as the position detection device. In addition,
Components labeled with the same numbers as in FIG. 1 indicate the same functions as the components in FIG. Reference numeral 201 denotes a position sensing detector (hereinafter referred to as PSD), which detects the position of the spot light incident on the light receiving surface and outputs the detected position. 202 is a slit that moves together with the movable lens, and allows infrared light from the infrared light emitting diode 203 to enter the PSD 201 at a position proportional to the movable lens. When the CPU 7 outputs a signal to the motor driver 205, the motor 206 is driven, and the movable lens 207 moves in the optical axis direction. The PSD output reading circuit 204 converts the signal from the PSD 201 into the position of the movable lens 207 and outputs it to the CPU 7. C.P.
U7 compares and calculates the data stored in the correction data 208 and the output of the PSD output reading circuit 204 to detect the position of the movable lens 207.

FIG. 7 shows the PSD 201. When the spot light 251 enters the light-receiving surface 252, photoelectrons are generated inside the PSD, a photocurrent flows, and the terminals 253 and 25
Voltage appears at 4. A power source (not shown) is connected to the terminal 255.

However, when the slit 202 of the PSD 201 and the infrared light emitting diode 203 are actually combined, there will be a difference between the position of the movable lens and the output of the PSD 201 due to their positional relationship and variations in the characteristics of the PSD 201. arise.

FIG. 8 is a diagram showing the characteristics when a position detection device as shown in FIG. 7 is actually manufactured. The horizontal axis indicates the movable lens position, and the vertical axis indicates the output level of the position signal. The design value or desired output characteristic is the characteristic as shown by the broken line A'', but the actual output characteristic depends on the positional relationship between these and the PSD 201 when the PSD 201, slit 202, and infrared light emitting diode 203 are combined. Due to variations in characteristics, the position of the movable lens and PSD2
There is a difference between the output and the output of 01, as shown by the solid line B''.

Therefore, in the present invention, the broken line A″ in FIG.
The accurate movable lens position can be determined by storing the difference between B'' and the solid line B'' in the correction data memory in advance as correction data, and calculating the movable lens position at the design value from the output of the position detection device in the CPU 7. If the capacity of the ROM for storing data is small and it is not possible to store a large number of correction data, set several reference positions of the movable lens as the contents of the correction data memory.
The difference between the broken line A'' and the solid line B'' at the reference position may be stored in the correction data memory, and the CPU 7 may calculate correction data at a position between the reference positions by interpolation. Further, an arithmetic expression or a constant for calculating the difference between the broken line A'' and the solid line B'' may be stored as correction data in the correction data memory, and the correction data may be calculated in the CPU 7, which constitutes the present invention. correction data memory 13,
16, 208 is due to variations in characteristics due to manufacturing conditions in the position detection means for detecting the position of movable lenses such as focus lenses and variators, and variations in the positions and characteristics of the constituent members that constitute the position detection means. Any information for correcting the difference between the output of the position detection means and the position of the movable lens may be used.

FIG. 9 is a block diagram showing a third embodiment in which the present invention is applied to a rear focus zoom lens. Components labeled with the same numbers as in FIG. 1 are the same as those in FIG. be. 301 is the main switch,
When the main switch 301 is closed, the power-on reset circuit 302 is activated and various initial setting operations are performed. 303 is a first group lens, and 304 is a second group lens, each of which moves in opposite directions in the optical axis direction to perform a magnification change action. 305 is a zoom lens, which outputs the detected position of the second group lens 304 to the zoom encoder reading circuit 12;
outputs the information to the CPU. 306 is a fixed third group lens, and 307 is a fourth group lens which is a focus lens. A focus encoder 308 outputs the detected position of the fourth group lens 307 to the focus encoder reading circuit 13, and the focus encoder reading circuit 13 outputs the information to the CPU 7. The area data memory 309 includes the zoom encoder output circuit 12
Predetermined area division data is stored for each output of the focus encoder output circuit 13. The speed data memory 310 stores information regarding the driving speed of the focus lens, which is predetermined for the above-mentioned area. Correction data memory 31
1 stores information regarding correction of the zoom encoder 305 and the focus encoder 308.

When the zoom switch 2 is pressed, the CPU detects the pressed zoom direction and outputs information to the zoom motor drive 3 to drive the zoom motor 4 in that direction to perform magnification change. However, in the optical system according to the present invention, when magnification is changed for the same subject, focus cannot be maintained unless the focus lens 307 is moved during the magnification change. An example is shown in FIG. 10(a). The horizontal axis is the second group lens position, the vertical axis is the fourth group lens position, and the curve shows the focusing locus of the focus lens 307 at the illustrated subject distance. Therefore, during zooming, the variator position and the focus lens position are divided into blocks, and within the same block, the same focus lens speed is read out to control the focus lens 307. An example is shown in FIG. 10(b). During zooming, the CPU outputs a signal to the focus motor drive 9 so as to drive the focus lens 307 at a focus lens drive speed corresponding to the block. With this configuration, it is possible to maintain focus even during zooming. Also, during zooming, the focus lens position relative to the variator position stored in advance may be read out.
The focus lens may be controlled by a signal output from the automatic focusing device 5, or the focus lens position to be moved may be determined by calculating the focus lens position relative to the variator position stored in advance during zooming. often,
Any configuration that can maintain focus during zooming may be used. When performing the above-described control, detection of the focus lens position and the variator position becomes an important element.

FIG. 2 shows an enlarged view of a portion of the focus encoder 308. 101 is a lens frame which holds a lens (not shown) inside and is movable in the optical axis direction;
A first electrode 103 is formed on the outside thereof. 10
3 is a fixed lens barrel, and a second electrode 104 is formed inside thereof. FIG. 3 is a diagram showing characteristics when an encoder like the one shown in FIG. 2 is actually manufactured. The horizontal axis represents the focus lens position, and the vertical axis represents the output level of the position signal. The design value or desired output characteristic is as shown by the broken line A, but the actual output characteristic is as shown by the solid line B due to variations in electrode shape, electrode spacing, etc. due to manufacturing errors.

Therefore, in the present invention, the difference between the broken line A and the solid line B in FIG. By doing this, accurate focus lens position can be determined. When the capacity of the ROM for storing data is small and it is not possible to store a large number of correction data, several reference positions of the focus lens are determined as the contents of the correction data memory 311, and a broken line A and a solid line B at the reference positions are set. The difference between the two reference positions may be stored in the correction data memory 311, and the CPU 7 may perform interpolation to calculate correction data at positions between the reference positions. Alternatively, an arithmetic expression or constant for calculating the difference between the broken line A and the solid line B may be stored as correction data in the correction data memory 311, and the CPU 7 may calculate the correction data.

FIG. 4 shows an enlarged view of the zoom encoder 305. 151 is a resistor, and when the contact 152 moves in the optical axis direction together with the variator 1, the voltage applied from a DC power source (not shown) between the terminals 153 and 154 is divided and output to the terminal 155. do. FIG. 5 shows the characteristics of the resistance value between the terminals 153 and 155 and the variator position. The horizontal axis shows the variator position, and the vertical axis shows the resistance value between the terminals 153 and 155, respectively. The design value or desired output characteristic is as shown by the broken line A', but the actual resistance value is as shown by the solid line B' due to variations in the resistivity distribution of the resistor due to manufacturing errors. , the difference between the broken line A' and the solid line B' in FIG. By determining the resistance value, the accurate position of the variator can be determined. When the capacity of the ROM for storing data is small and it is not possible to store a large number of correction data, several reference positions of the variator are determined as the contents of the correction data memory 311, and the broken line A' and the solid line B at the reference positions are set. ' is stored in the correction data memory 311, and the difference between CP and
In U7, correction data at positions between the reference positions may be calculated by interpolation calculation. Further, an arithmetic expression and constants for calculating the difference between the broken line A' and the solid line B' are stored as correction data in the correction data memory 311, and the CPU 7
The correction data may be calculated in .

Furthermore, there is also a method of increasing the accuracy of lens position detection in accordance with the position sensitivity of the fourth group lens. In the optical system according to the present invention, the positional sensitivity of the fourth group lens to focus movement changes depending on the focal length and object distance. The position sensitivity changes as shown in FIG. 11, for example. In such a case, if the detection accuracy of the fourth group lens position is changed in accordance with the second group lens position in the same way as the fourth group lens position sensitivity, the fourth group lens position sensitivity is high in the fourth group lens position. Since the focus movement due to the movement of the fourth group lens is large, the focus movement can be kept small by detecting the position of the fourth group lens with high precision in a place where the sensitivity of the fourth group lens is high, and focus detection by an automatic focusing device is possible. This has the effect of reducing focus movement during zooming, and minimizing focus movement when changing magnification. As a method of performing high-precision correction, when several reference positions of the variator are determined as the contents of the correction data memory 311, the number of reference positions is increased in areas where the fourth group lens position sensitivity is high, and the correction data is Store it in memory, 311,
The CPU 7 may calculate correction data at positions between the reference positions by interpolation calculation. In addition, when the arithmetic expressions and constants for calculating the difference are stored as correction data in the correction data memory 311, when the correction data is calculated in the CPU 7, the correction can be made with high precision in areas where the fourth group lens position sensitivity is high. Arithmetic expressions and constants that can be used may be stored in the correction data memory 311.

Furthermore, there is also a method of increasing the detection accuracy of the position of the fourth group lens according to the width of the depth of focus. In general, focus accuracy is small at the wide-angle end and large at the telephoto end, wide when the aperture is stopped down, and narrow when the aperture is opened. In a place where the depth of focus is narrow, the size of the circle of confusion is larger than in a place with a wide depth of focus when the moving distance of the fourth group lens from the in-focus position is the same, and the focus shift due to the movement of the fourth group lens is big. Therefore, by detecting the position of the fourth group lens with high precision at a narrow depth of focus, it is possible to suppress the focal shift to a small value, which can reduce the focal shift during focus detection by an automatic focusing device, which is caused by zooming. This has the effect of keeping focus movement to a minimum. As a method of performing high-precision correction, when several reference positions of the variator are determined as the contents of the correction data memory 311, the number of reference positions is increased when the depth of focus is narrow.
11, and the CPU 7 calculates correction data at positions between the reference positions by interpolation calculation. In addition, when storing an arithmetic expression or constant for calculating a difference in the correction data memory 311 as correction data, C
When calculating the correction data in the PU 7, the correction data memory 311 may store arithmetic expressions and constants that allow highly accurate correction in areas where the depth of focus is narrow. Furthermore, during zooming, if the variator position and focus lens position are divided into blocks, and the same focus lens speed is read out within the same block to control the focus lens 307, Block division as shown in FIG. 12 may be performed, or another block division may be performed.

The optical system constituting the present invention is not limited to a rear focus zoom; any optical system may be used as long as the positional sensitivity of the focus lens changes as the magnification changes; It can also be applied to so-called front lens focus optical systems that perform focusing by moving the closest lens group. When the present invention is applied to an optical system with a front lens focus, there is an advantage that the position sensitivity of the focus lens increases on the telephoto side where the depth of focus is narrow, which is convenient. Further, the lens group that performs the correction is not limited to the focus lens, but may be any lens group that moves.

[0030]

[Effects of the Invention] As described above, according to the present invention, the conventional lens position control device can be controlled without making any major changes.
Highly accurate lens position control can be performed.

[Brief explanation of drawings]

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

FIG. 2 is a perspective view of a position detection device using capacitance.

FIG. 3 is a diagram showing the characteristics of a position detection device using capacitance.

FIG. 4 is a perspective view of a position detection device using a potentiometer.

FIG. 5 is a diagram showing the characteristics of a position detection device using a potentiometer.

FIG. 6 is a block diagram showing a second embodiment of the present invention.

FIG. 7 is a perspective view of a position detection device using a photocoupler.

[Figure 8] Diagram showing the characteristics of a position detection device using a photocoupler

FIG. 9 shows blocks showing a third embodiment of the present invention.

FIG. 10(a) is a diagram showing a movement locus of the fourth lens group as the magnification changes. (b) is a diagram illustrating block division when controlling the fourth group lens during zooming.

FIG. 11 is a diagram showing changes in the positional sensitivity of the fourth lens group as the magnification changes.

FIG. 12 is a diagram illustrating another block division when controlling the fourth group lens due to zooming.

[Explanation of symbols]

1... Variator 8...
Focus lens 11...Zum encoder
12...Zoom encoder reading circuit 13...First correction data 14...Focus encoder 15...Focus encoder reading circuit 16...Second correction data 201...PSD202...Slit 203...Infrared light emitting diode 204...PSD output reading circuit 208...Correction data 3
03...Variator 304...Second group lens (variator) 305...Zoom encoder (potentiometer type encoder) 307...Fourth group lens (focus lens) 308...Focus encoder (capacitance type encoder) 309...Area data 310...
Speed data 311...correction data

Claims (1)

[Claims] 1. A lens position control device for an optical system having a lens that moves in the optical axis direction, comprising: a moving means for moving the lens by electromechanical conversion; a position detecting means for detecting the position of the lens; A storage means for storing information regarding the characteristics of one or both of the moving means and the position detection means, and the output result of the position detection means and the stored contents of the storage means are compared, and the position of the lens is determined. A lens position control device characterized by comprising: calculation means for calculating.