JPH08122608A - Lens moving amount detecting device - Google Patents

Abstract

PURPOSE: To provide a compact lens moving amount detecting device capable of precisely detecting the moving amount of a lens in a camera. CONSTITUTION: A reflection member 12 having a triangle-wavy cross-section is attached to a movable lens 10 and irradiated with light by using an LED 14. At this time, the light emitted from the LED 14 is reflected in two directions by two kinds of facial directions of the reflection member 12. The light reflected in two directions is detected by photodiodes 18A and 18B provided in the respective reflecting directions. When a differential signal for showing the difference between the voltage signals obtained by these two photodiodes 18A and 18B is detected from the output of a differential amplifier 22, the moving amount of the lens can be detected by the voltage value of the differential signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens moving amount detecting device, and more particularly to a lens moving amount detecting device for optically detecting a lens moving amount.

[0002]

2. Description of the Related Art When performing focus adjustment or the like with an autofocus device such as a video camera or a still camera, the focus lens is moved to a lens position corresponding to a measured distance, or a movement corresponding to a detected defocus amount. The focus lens is moved by the amount. Therefore, when the focus adjustment is performed by the autofocus device, it is necessary to detect the moving position and the moving amount of the focus lens.

Conventionally, the position of the lens is detected by printing a code such as a binary code on a supporting frame of the lens and reading the code electrically with a brush or the like.

[0004]

However, in the conventional method of reading a code with a brush or the like, there is a problem that load is applied to the motor due to sliding resistance and the operability is not good. The present invention has been made in view of the above circumstances, and an object thereof is to provide a lens movement amount detection device that optically detects the lens movement amount with high accuracy.

[0005]

In order to achieve the above-mentioned object, the present invention is a triangular wave having a constant pitch, which is attached to a movable lens and in which first reflecting surfaces and second reflecting surfaces are alternately formed. A reflecting member having an upper cross section, a light emitting unit for irradiating light on the first and second reflecting surfaces of the reflecting member that moves with the movement of the lens, and a first member of the reflecting member emitted from the light emitting unit. Detect the light reflected by the reflective surface of 1,
A first light detecting means for converting into a voltage signal; a second light detecting means for detecting light emitted from the light emitting means and reflected by a second reflecting surface of the reflecting member; and converting into a voltage signal, Comparing the voltage signals output from the first and second photodetecting means and outputting a voltage signal indicating the difference between them, and detecting the lens movement amount based on the voltage signal output from the comparing means. And a detection means.

Further, in a lens movement amount detecting device which moves in the optical axis direction by a rotating lead screw,
Light emitting means for irradiating the first screw surface and the second screw surface of the lead screw adjacent to each other with light, and light emitted from the light emitting means and reflected by the first screw surface of the lead screw. Detecting the light and converting it into a voltage signal, and a second light that detects the light emitted from the light emitting means and reflected by the second screw surface of the lead screw and converts it into a voltage signal. Detecting means and the first
And comparing means for comparing the voltage signals output from the second light detecting means, and outputting a voltage signal indicating the difference, and detecting means for detecting the lens movement amount based on the voltage signal output from the comparing means. It is characterized by having and.

[0007]

According to the present invention, the light emitting means fixed to the camera body is mounted on a reflecting member having a triangular wave-shaped cross section in which first and second reflecting surfaces are alternately formed and attached to a movable lens. Irradiate light from. Then, the light reflected from the first or second reflecting surface of the reflecting member that moves with the movement of the lens is detected by the first or second light detecting means,
These reflected lights are converted into voltage signals. Subsequently, the difference signal indicating the difference between the two voltage signals obtained from the first or second light detection means is detected by the comparison means, and the movement amount of the lens is detected by the detection means from this difference signal.

Further, instead of the reflecting member, a screw thread of a lead screw is used, and the reflection of light from the first screw surface and the second screw surface adjacent to each other of the screw thread is detected to detect the lens. The amount of movement is detected.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a lens movement amount detecting device according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a configuration diagram of a zoom lens device to which a lens movement amount detection device according to the present invention is applied.

As shown in the figure, a focus lens 10 is arranged in front of the lens barrel 100 of the zoom lens device, and a variable power lens 10 is arranged behind the focus lens 10.
2, the correction lens 104 and the relay lens 106 are sequentially arranged. The focus lens 10 is held by a support frame 43, and the support frame 43 is fixed via a pin 45 so as to be interlockable with a connecting portion 44. The connecting portion 44 is screwed into the lead screw 42, and is moved in the optical axis direction by the lead screw 42 rotated by the rotation motor 40. Therefore, the focus lens 10 is moved by the rotary motor 40 in the optical axis direction via the connecting portion 44 (moves left and right in the drawing).

Further, the variable power lens 102 and the correction lens 1
Reference numeral 04 is guided by a cam cylinder (not shown) so as to have a predetermined positional relationship, and moves in the optical axis direction. FIG. 2 is a configuration diagram showing a lens movement amount detection device. As shown in the figure, the focus lens 10 shown in FIG. 1 is provided with a light reflecting member 12 having a triangular wave-shaped cross section with a constant pitch P. Actually, a part of the connecting portion 44 or the support frame 43 arranged in the focus lens 10 serves as the light reflecting member 12.

A light emitting diode (LED) is provided on the upper surface side where the triangular wave-shaped peaks and valleys are formed with respect to the light reflecting member 12.
14 is fixedly arranged on the lens barrel 100 of FIG.
The ED 14 illuminates the triangular wave surface of the light reflecting member 12 from the front by the drive control of the LED driving unit 16. LED
The light emitted from 14 is reflected by the triangular wave surface of the light reflecting member 12 and detected by the photodiodes 18A and 18B. That is, there are two types of surface directions of the triangular wave surface of the light reflecting member 12, that is, a right slope surface and a left slope surface, as shown in FIG.
The light reflected by either surface (the light beam emitted from the LED 14 is divided by the two kinds of surfaces) is the photodiode 18A or 18A depending on the surface direction of the reflecting surface.
It is detected by either B.

The light detected by the photodiodes 18A and 18B is converted into a voltage signal proportional to the intensity of light, amplified by the amplifiers 20A and 20B, and then output to the input terminal of the differential amplifier 22. The differential amplifier 22 amplifies the voltage signal of the difference between the voltage signals output from the amplifiers 20A and 20B, and outputs this voltage signal to the other terminal of the comparator 24 whose one terminal is connected to the ground level. . At the same time, 8-bit A /
Output to the D converter 26.

FIG. 3 shows a circuit embodiment of a lens movement amount detecting device. As shown in the figure, conversion of an optical signal into a voltage signal is performed by photoelectric conversion circuit blocks 19A and 19B including photodiodes 18A and 18B. That is, the photodiodes 18A and 18B convert the incident light into a current signal proportional to the light intensity, and the diodes 17A and 17B of the feedback circuit convert the current signal into a voltage signal. Further, the amplifiers 20A and 20B are respectively O
It is an inverting amplifier composed of P amplifiers A ₃ and A ₄ .

When the voltage signal output from the differential amplifier 22 is input to the comparator 24 and the A / D converter 26,
The comparator 24 compares the voltage signal output from the differential amplifier 22 with the ground level, outputs a predetermined voltage when the voltage signal output from the differential amplifier 22 is higher than the ground level, and lower than the ground level. In that case, the output voltage is set to zero. Also, the A / D converter 26 converts the voltage signal output from the differential amplifier 22 into an 8-bit digital signal.

The signals output from the comparator 24 and the A / D converter 26 are input to a control unit (not shown). The control unit detects the amount of movement of the focus lens 10 based on these signals. That is, the control unit controls the focus lens 10
The number of repetitions of the output signal of the comparator 24, which is periodically repeated for each movement amount of the pitch P of the triangular wavefront of the light reflecting member 12 in accordance with the movement of the focus lens 10, is performed with the accuracy of the pitch P. The moving amount of the focus lens 10 is detected with a precision of 1/255 of the pitch P from the digital value of the output signal of the A / D converter 26 (8 bits). The details will be described later.

When detecting the absolute position of the focus lens 10, the amount of movement of the focus lens 10 from the reference position is detected. The reference position of the focus lens 10 is detected by the light blocking plate 46 and the photo interrupter 47 attached to the connecting portion 44 of FIG. When the stop position of the focus lens 10 is unknown, such as immediately after turning on the power of the camera, the focus lens 10 is appropriately moved to move the photo interrupter 47.
The light-shielding plate 46 is detected by, and the position of the focus lens 10 at the time of detecting this light-shielding plate 46 is set as the reference position.

As described above, the control unit outputs a drive signal to the rotary motor 40 for moving the focus lens 10 and sequentially detects the position or the movement amount of the focus lens 10, and the focus lens 10 has a predetermined position. When it reaches, the movement of the focus lens 10, that is, the driving of the rotation motor 40 is stopped. Next, as the focus lens 10 moves, the comparator 24, A
The state of the signal output from the / D converter 26 will be described.

FIG. 4 is an explanatory view showing the positional relationship between the position of the LED 14 and the triangular wave-shaped surface, and characteristic positions of the LED 14 with respect to the triangular wave-shaped surface are shown by a to e. a and e
Is the maximum point of the triangular wave, c is the minimum point of the triangular wave, and b and d are the midpoints of the maximum point and the minimum point of the triangular wave. In FIG. 5, the focus lens 10 moves to the left in the drawing of FIG.
5 shows output signals at the output terminals 1 to 2 shown in FIG. 2 when the light irradiation position of the ED 14 changes relative to the triangular wave surface in the direction from a to e shown in FIG.

The horizontal axis of FIG. 5 indicates the position of the LED 14, and the positions corresponding to the positions a to e of FIG. 4 are indicated by the same reference numerals on the horizontal axis. Further, the output signal shown in FIG. 5 represents the case where the diameter of the light emitted from the LED 14 is about one half of the pitch P of the upper surface of the triangular wave shown in FIG.
First, the state of the output signal from the output terminal will be described.

As shown in FIG. 5, when the LED 14 is located at "a", L is set by the two directions of the triangular wave surface.
The light emitted from the ED 14 is reflected in exactly different directions by half, and is detected by the photodiodes 18A and 18B with the same light intensity. Therefore, the output voltage of the output terminal becomes equal, and the voltage difference between the two output terminals is 0, so the output voltage of the output terminal is 0.

As the position of the LED 14 moves from a to b, the light reflected by the right slope of the triangular wave surface increases among the light emitted from the LED 14 and is detected by the photodiode 18B. Light becomes stronger. Therefore, the output voltage at the output terminal increases.
On the other hand, since the light reflected by the left slope of the triangular wave surface decreases, the output voltage at the output terminal decreases.

When the LED 14 comes to be located at b,
All of the irradiation light comes to be reflected by the right slope of the triangular wave surface, and is not reflected by the left slope. Therefore, the output voltage becomes maximum at the output terminal, and the output voltage becomes 0V which is the minimum at the output terminal. At the output terminal, the output voltage increases from the position a to the position b as shown in FIG. 5, and reaches the maximum value at b.

Subsequently, when the position of the LED 14 moves from b to c, the light reflected by the left slope of the triangular wave surface increases and the light reflected by the right slope decreases. . Therefore, the output voltage at the output terminal is 0V.
The voltage at the output terminal decreases from the maximum value. At the position of c, the intensity of light reflected by both slopes becomes equal, and the output voltages of the output terminal and the output terminal become equal.

The output voltage of the output terminal is LED1.
4 decreases from the maximum value while moving from b to c, and becomes 0 V when the output voltage of the output terminal becomes equal to that of the output terminal at c. After that, the position of the LED 14 changes from c to e.
In the case of moving to, the reflected light from the right slope of the triangular wave surface becomes maximum at b, and the reflection by the left slope becomes maximum at d, and the output terminal outputs the maximum voltage at d. On the other hand, the output voltage of the output terminal becomes 0 at d. Further, the output terminal outputs a voltage obtained by making the output voltage at b negative.

That is, when the LED 14 is located in the middle of the slope of the triangular wave surface, the output voltage of the output terminal and the output voltage becomes the minimum or maximum value, and when it is located in the middle of the right slope, the minimum value and output at the output terminal. Take the maximum value at the terminal. On the left slope, the output terminal has the maximum value,
The terminal takes the minimum value. Accordingly, the output terminal takes the maximum value on the right slope and the minimum value on the left slope. This is not limited to the case where the diameter of the light beam emitted from the LED 14 is about ½ of the pitch P on the upper surface of the triangular wave as described above, and is valid when the diameter is smaller than ½ of the pitch P.

Next, the output signal at the output terminal will be described. Since the output voltage of the output terminal is higher than the ground level when the LED 14 is located between a and c, a predetermined voltage is output from the output terminal. On the other hand, between c and e, the output voltage of the output terminal is lower than the ground level, and the output voltage of the output terminal is 0.

The output terminal converts the output voltage of the output terminal into an 8-bit digital signal from the minimum value to the maximum value. That is, b at which the output voltage of the output terminal becomes maximum
255 is output at the position of 0, 0 is output at the position of d that is the minimum, and 128 is output at the positions of a, c, and e where the output voltage of the output terminal is 0. As described above, the output terminal outputs the voltage signal which changes with the movement of the distance of ½ of the pitch P of the triangular wave-shaped surface, and the output terminal outputs the distance of ½ of the pitch P by 8 An 8-bit digital signal when subdivided into bits is output.

Therefore, the control unit (not shown) controls the movement of the lens in units of the pitch P of the triangular wave surface based on the output signal of the output terminal when the lens is largely moved, and the output terminal when the lens position is finely adjusted. The movement is controlled in units of P / 255 when the pitch P is subdivided into 8 bits based on the output signal of As shown in FIG. 1, in the case where the lens is moved by the lead screw 42, etc., instead of the light reflecting member in the above embodiment, as shown in FIG.
Two screw faces may be used. Since the threaded surface of the lead screw 42 apparently moves back and forth as the lead screw 42 rotates (that is, the lens moves), the LED 14 irradiates the threaded surface with the reflected light from the two threaded surfaces having different inclinations. Are the photodiodes 18A and 1
8B to detect.

[0030]

As described above, according to the lens movement amount detecting apparatus of the present invention, the reflecting member having two kinds of reflecting surfaces that move with the movement of the lens is irradiated with light, and the reflecting member By detecting the light reflected from the reflecting surfaces of two kinds by the two light detecting means and comparing the intensities of these lights, a small and highly accurate lens movement amount detecting device can be mounted on a camera or the like.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a zoom lens device to which a lens movement amount detection device according to the present invention is applied.

FIG. 2 is a configuration diagram showing a lens movement amount detection device according to the present invention.

3 is a circuit diagram showing a circuit configuration of the lens movement amount detection device shown in FIG.

FIG. 4 is an explanatory diagram illustrating a positional relationship between the light reflecting member and the LEDs illustrated in FIG.

5 is an explanatory diagram showing output signals at output terminals 1 to 3 shown in FIG. 2;

FIG. 6 is a configuration diagram showing another embodiment of the lens movement amount detection device according to the present invention.

[Explanation of symbols]

 10 ... Lens 12 ... Light reflection member 14 ... LED 18A, 18B ... Photodiode 20A, 20B ... Amplifier 22 ... Differential amplifier 24 ... Comparator 26 ... A / D converter 40 ... Rotation motor 42 ... Lead screw

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G03B 13/34 G03B 3/10

Claims (3)

[Claims] 1. A first lens attached to a movable lens.
A reflecting member having a triangular-wave cross section with a constant pitch in which the reflecting surface and the second reflecting surface are alternately formed; and the first reflecting member that moves with the movement of the lens.
And light emitting means for irradiating the second reflecting surface with light, and first light detecting means for detecting the light emitted from the light emitting means and reflected by the first reflecting surface of the reflecting member, and converting it into a voltage signal. , Second light detecting means for detecting the light emitted from the light emitting means and reflected by the second reflecting surface of the reflecting member and converting it into a voltage signal, and output from the first and second light detecting means. Comparing the voltage signals, and outputting a voltage signal indicating the difference between the voltage signals, and a detecting means for detecting the lens movement amount based on the voltage signal output from the comparing means. Lens movement amount detector. 2. A lens movement amount detection device that moves in the optical axis direction by a rotating lead screw, wherein light is applied to a first screw surface and a second screw surface of the lead screw which are adjacent to each other. A light emitting means, a first light detecting means for detecting light emitted from the light emitting means and reflected by the first screw surface of the lead screw, and converting the light into a voltage signal; and the lead screw emitted from the light emitting means. Second light detecting means for detecting the light reflected by the second screw surface and converting it to a voltage signal, and comparing the voltage signals output from the first and second light detecting means, and the difference And a detection unit that detects the lens movement amount based on the voltage signal output from the comparison unit. Place. 3. The detecting means binarizes the voltage signal output from the comparing means to output a pulse signal indicating lens movement at constant pitches, and the voltage signal output from the comparing means. The lens movement amount detection device according to claim 1 or 2, further comprising: an A / D converter that performs A / D conversion and outputs a digital signal of a plurality of bits obtained by subdividing a fixed pitch.