JPH0765882B2 - Position detector and lens device using the detector - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detector for detecting a lens position using a resistor, a moving body, a slider, an amplifier and an attenuator, and a lens using the position detector. Regarding the device.

2. Description of the Related Art A resistor provided on a substrate as one of conventional position detecting means, a movable body moving in parallel on the resistive body and a resistor having a voltage applied to both ends thereof, and the movable body mounted on the movable body, the resistive body There is a method of detecting the lens position by using a position detection device equipped with a slider that slides on the top and extracts a voltage. The above operation will be described with reference to FIG.

FIG. 5 is a block diagram of a conventional position detector. In FIG. 5, 35 is a substrate, 36 is a resistor installed on the substrate, 37 is a moving body that moves in parallel on the resistor 36, and 38 is 36.
Slider for sliding voltage on the resistor of and taking out voltage, 39
Is an output terminal, 40 and 41 are terminals for applying a voltage, and 42 is a power source.

If a voltage of E [V] is applied to both ends of the resistor 36 and the slider slides continuously from point a to point b on the resistor,
The potential O [V] at point a and the potential at point b can be expressed as E [V]. Therefore, assuming that there is no error in the resistance value of the resistor at the distance x (m) from the point a of the slider when the output voltage e [V] smaller than E [V] which is not negative is output, Can be expressed as However, the distance between point a and point b is X
(M).

However, the position information actually extracted from the resistor is an analog voltage, and this position information is often A / D converted and processed with a digital value. Therefore, the resolution of the position detector is limited by the resolution of the A / D converter. That is, when the position output is an analog value and the position information is converted to a digital value, the conventional position detector
There is a problem that it is not possible to achieve a resolution higher than that limited by the resolution of the A / D converter.

The present invention solves the above-mentioned problems and provides a position detector capable of realizing higher resolution.

Means for Solving the Problems In order to solve the above problems, the position detector of the present invention is
At least one resistor formed on the substrate and having a voltage applied to both ends, a moving body that moves in parallel to the resistor, and a slider that is mounted on the resistor and slides on the resistor. An output terminal for taking out a voltage attached to the slider, an analog-digital (A / D) converter for converting the voltage taken out from the output terminal into digital data, and an output terminal taken out from the output terminal, A gain adjustment circuit that amplifies and attenuates the voltage input to the A / D converter,
The gain adjustment circuit changes the amplification factor in each of a plurality of sections on the resistor.

Function The present invention is a position detector using one resistor having the above-described configuration, and the position detection resolution detects the output voltage.
While limited by the resolution of the A / D converter, the output voltage extracted from the slider is amplified and attenuated within a certain range of the resistor position detection range, and It is possible to adjust the input voltage and improve the position detection resolution in the gain adjustment range.

Examples Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, 1 is a substrate for mounting a resistor, 2 is a resistor for extracting position information of a position detection range, 3 is a moving body which moves in parallel on the resistor, and 4 is the resistor. A slider mounted on the body for detecting the position detection range on the resistor, 5 is an output terminal for outputting the voltage taken out from the slider, and 6 and 7 are a voltage across the resistor. Terminals provided for applying voltage, 8 and 9 are power supplies for applying voltage to terminals 6 and 7, 10 is a circuit for adjusting the gain of the voltage extracted from the output terminal 5, and 11 and 12 are outputs, respectively. It is an A / D converter for converting the voltage taken out at the terminal 5 and the voltage amplified and attenuated by the voltage gain adjusting circuit into digital data. It should be noted that one A / D converter may be used if the input can be freely switched.

In FIG. 1, it is assumed that the position detection range is from point a to point b, the distance is X (m), the potential at point a is Ea [V], and the potential at point b is Eb [V]. Adjust the power supplies 8 and 9 as follows. At this time, Eb [V] is made larger than Ea [V], and Ea [V] and Eb [V] are made equal to the lower limit input reference voltage and the upper limit input reference voltage of the A / D converter, respectively. When the position information is converted to digital and considered, the resolution P ₁ (m) of the position detector is P ₁ = X / 2 ⁿ (m) ...... ( ^{where the} number of bits of the A / D converter is ⁿ 2)

From a point X (m) away from point a (point c), L
Points farther away from (m) and (L <X) (d points)
First, the output potential Ec [V] at the point c is The output potential Ed [V] at the point d is It is represented by. Therefore, the voltage gain adjustment circuit
Further, Ed [V] is set so that the potential of [V] becomes Ea [V].
The voltage gain adjustment is performed so that the potential of the output voltage becomes Eb [V] and that the output voltage changes linearly from the point c to the point d. If the moving body 3 slides from point a to point b,
The voltage extracted from the output terminal 5 is converted to digital data by the A / D converter 11 between the points c and d and between the points d and b, and the output voltage of the voltage gain adjusting circuit 10 is converted between the points c and d. A / D converter 1
I think that it will be converted to digital data in 2. FIG. 2 shows the output voltage characteristic 13 of the output terminal 5 and the output voltage characteristic 14 of the voltage gain adjusting circuit. At this time, between point c and point d (distance L
The position detection resolution P ₂ (m) of (m)) becomes P ₂ = L / 2 ⁿ (m) (5), which is the position detection resolution between points a and c and between points d and d. Compared with L / X times, the position detection resolution can be improved.

As a second embodiment, a lens device using the position detector of the present invention will be described.

A lens device includes a zoom function, and in the past, a focusing method by moving a frontmost lens group of a zoom lens has been mainstream, but in recent years, a focusing method by moving a lens group other than the frontmost lens group or a part of the lens group or an imaging element. A focusing method by moving the lens, that is, a rear focus method has come out. However, in the rear focus method, a shift in the image forming position occurs due to a change in the focal length of the zoom lens due to zooming, and correction is necessary. Since this correction using a mechanical cam is extremely complicated, it can be obtained, for example, from a zoom position detecting means for detecting the position of the lens group used for zooming and a focusing position detecting means for detecting the position of the focusing system. The locus of movement of the focusing system is calculated from the position information, and the displacement of the position of the focusing system is corrected according to the locus (Japanese Patent Application No. 61-73542).

FIG. 6 shows the relationship between the zoom position and the position movement amount of the focusing system. The ratio of the position movement amount of the focusing lens system to the change of the zoom position is larger on the telephoto side than on the wide angle side (for example, see Japanese Patent Laid-Open No. 57-4018).

Therefore, since the ratio of the amount of movement of the focusing system to the change of the zoom position is small on the wide-angle side, the resolution of the conventional position detector is sufficient for detecting the zoom position, but on the telephoto side, the amount of change of the focusing system is large. Therefore, high resolution is required for zoom position detection. That is, a high-resolution position detector is required.

FIG. 3 is a configuration diagram of a lens device using the position detector of the present invention, and FIG. 4 is a voltage output characteristic diagram. 15 in FIG.
Is a zoom lens, 16 is a focusing lens, 17 is a substrate for mounting a resistor, 18 is a resistor for extracting position information of a position detection range, and 19 is a moving body that moves in parallel on the resistor. , 20 is a slider that is mounted on the resistor and slides in a position detection range on the resistor, 21 is an output terminal that outputs the voltage extracted from the slider, 22, 2
3 is a terminal provided to apply a voltage to both ends of the resistor, 24 and 25 are power supplies for applying a voltage to the terminals 22 and 23, 26 is a gain adjusting circuit for the voltage extracted from the output terminal, 27 Reference numerals 28, 29 denote resistors constituting the voltage gain adjusting circuit 26 and an operational amplifier, 30 a power supply for applying a voltage to the voltage gain adjusting circuit 26, 31 and 32 a voltage taken out from the output terminal 21, and a voltage gain adjusting It is an A / D converter that digitally converts the output voltage of the circuit 26.

Further, the position detection range X on the resistor is set to (m), and the range on the telephoto side that requires position detection with high zoom resolution in the position detection range on the resistor is set to x (m) (x <X / 2 ),
Wide angle end point to a point of the end point the point b on the telephoto side, the starting point of the range of the telephoto side and point c, the power supply voltage of 24 analog - to the lower limit reference voltage of the digital converter (= V _B [V]) Equal to 25,3
The power supply voltage of 0 is equal to the upper limit input reference voltage (= V _T [V]) of the analog-digital converter, and the ratio of the resistance values of the resistors 27 and 28 in the voltage gain adjusting circuit 26 is (X−x): x
And With the configuration shown in FIG. 3, the position detection resolution P _W (m) of the zoom lens on the wide-angle side is an analog-digital converter.
If the number of bits of 37 is n, the distance X (m) is divided into 2 ^{n, and} thus P _W = X / 2 ⁿ (m) (6) The output voltage Vc [V] of the voltage gain adjustment circuit 26 at the point c is Vc = V _B [V] (7) The output voltage Vb [V] of the voltage gain adjustment circuit 26 at the point b
Is Vb = V _T [V] (8) If the linearity of the resistance value of the resistor 18 is sufficiently ensured, the output of the voltage gain adjusting circuit 26 between the point c and the point b The voltage becomes linear. Therefore, the position detection resolution P _T (m) of the zoom lens between the points c and b divides the distance X (m) into 2 ^{n, and} therefore P _T = X / 2 ⁿ (m) (9) , The zoom lens position detection resolution can be increased by x / X times as compared with other parts. FIG. 4 shows the output voltage characteristic 33 extracted at the output terminal 21 and the output voltage characteristic 34 of the voltage gain adjusting circuit.

EFFECTS OF THE INVENTION As described above, according to the present invention, at least one resistor having a voltage applied to both ends formed on a substrate, a moving body that moves in parallel to the resistor, and a moving body A slider that is mounted and slides on the resistor to extract a voltage, an output terminal attached to the slider, and an A / D converter that converts the voltage extracted from the output terminal into digital data. Equipped with A / in the range where high resolution is required
By adjusting the output voltage taken from the output terminal so that the range of the voltage input to the D converter becomes equal to the dynamic range of the A / D converter, an expensive A / D converter with a large number of bits can be obtained. It is possible to partially realize the high resolution of the position detection without using it.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of a position detecting device according to an embodiment of the present invention, FIG. 2 is an output characteristic diagram of a position detector in FIG. 1,
FIG. 3 is a block diagram of a lens device using the position detector according to the present invention, FIG. 4 is an output characteristic diagram of the position detector in FIG. 3, and FIG. 5 is a block diagram of a position detector in a conventional example.
FIG. 6 is a characteristic diagram showing the relationship between the zoom position and the amount of movement of the focusing system lens in the lens device. 1,17,35 …… Board, 2,18,36 …… Resistor, 3,19,37 …… Moveable body, 4,20,38 …… Slider, 5,21,39 …… Output terminal, 6,7,
22,23,40,41 …… Voltage application terminal, 8,9,24,25,30,42 …… Power supply, 10,26 …… Voltage gain adjustment circuit, 11,12,31,32 …… A / D
Converter, 15 …… Zoom lens, 16 …… Focusing system lens, 27,28 …… Resistor, 29 …… Op-amp.

Front page continuation (72) Inventor Keizo Ishiguro 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP-A-2-254301 (JP, A)

Claims (3)

[Claims] 1. A at least one resistor formed on a substrate and having a voltage applied to both ends thereof, a moving body that moves in parallel to the resistor, and a resistor mounted on the resistor and sliding on the resistor. A moving slider, an output terminal for extracting a voltage attached to the slider, an analog-digital (A / D) converter for converting the voltage extracted from the output terminal into digital data, and the output A / D taken out from the terminal
A position detector comprising: a gain adjusting circuit for amplifying and attenuating a voltage input to the converter, wherein the gain adjusting circuit changes an amplification factor in each of a plurality of sections on the resistor. 2. A lens device using the position detector according to claim 1. 3. The lens apparatus according to claim 2, wherein at least one resistor has the gain adjusting circuit according to claim 1 on the telephoto side of the zoom position.