JPH0251020A - Position detector - Google Patents

Abstract

PURPOSE:To always accurately detect the position of an object by providing first and second pattern plates outputting an unequal dividing pulse and an equal dividing pulse in connection with the movement of a body and detecting the absolute position from the pulse ration of both pulses. CONSTITUTION:When a motor 10 is driven for focus matching, a helicoid 18 is rotated and a lens 21 is moved in an optical axial direction and a disc 1' is rotated. By this mechanism, the light and shade pattern of a reflecting plate 2 is detected by a photocoupler 4 to generate a pulse. The reflecting plate 2 has an equal divided pattern and the pulse P2 is formed in the number proportional to the quantity of rotation of the helicoid 18. A reflecting plate 1 is revolved at the driving time of the lens and a pattern change is detected by a photocoupler 3 to generate a pulse. This pulse becomes a pulse P3 having the width predetermined corresponding to the position of the lens because the reflecting plate 1 is in an unequally divided pattern and directly connected to the helicoid 18. That is, the pulse P2 shows a definite width t1 and the pulse P3 shows the width corresponding to the position of the lens and, therefore, an absolute position t2/t1 is calculated by a comparator circuit 9 to be detected by a computer 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a position detection device, and particularly to a position detection device capable of detecting the phase of a rotating body.

[Conventional technology]

Conventionally, as a method for detecting the moving position (absolute position) of an object, a pulse plate having a pattern shown in Fig. 8 is rotated once within the entire movement area of the object, and light is applied to the pulse plate to detect reflection or transmission. Absolute encoders that count the brightness and darkness of light are known. As another rotary plate encoder, a position detection method using a linear plate shown in FIG. 9 is known.

In FIG. 9, a conductive part and an insulating part are provided in the pattern, and the terminal 6
By comparing the voltages from 1 to 64 and assuming 1 when 61, 62, 63 is ON and O when OFF, the position can be determined from 8 combinations from (000) to (1°1, l). It becomes.

The conventional position reading methods described above include optical type and brush type. The optical type receives reflected or transmitted light and converts it into a pulse signal depending on the amount of light, while the brush type has a pattern with a conductive part and an insulating part and reads the voltage with a contact. The problem with the optical type is that as the number of divisions increases, the light emitting/receiving means circuit for reading becomes larger and the space becomes larger. For example, 128
If division is necessary, seven sets of elements are required. On the other hand, in the case of a brush type, in addition to space, it is vulnerable to water and noise.

There were problems such as lack of durability.

[Means for solving problems]

The present invention was made in view of the above-mentioned matters, and includes first and second pattern plates that are displaced relative to the reader in conjunction with the movement of an object, and the first pattern plate has pattern plates arranged at equal intervals. Patterns are placed on the pattern board for plan 2, patterns at uneven intervals are placed on the pattern board for plan 2, and the changes in the first and second patterns are read respectively, and the pattern changes on the first pattern board and the patterns on the second pattern board are read. It is an object of the present invention to provide a position detecting device that calculates a ratio with respect to a pattern change and calculates the absolute position of an object from the ratio value.

〔Example〕

FIG. 1 is a block diagram of a signal processing system in an example in which the present invention is implemented in an autofocus photographing device. 16 receives the subject light image through a photographing lens (not shown) and corrects the out-of-focus (
Defocus M) In the focus detection unit that detects, the detection result in this unit is converted into a digital signal by the A/D converter 15 and transmitted to the microcomputer 14. The computer 14 transmits a pulse t-t corresponding to the amount of movement of the focus lens for transitioning from the amount of out-of-focus to the in-focus state to the microcomputer 12 on the lens side. The computer 12 drives the motor l via the drive circuit for the number of pulses input through the above communication.
A focus lens (
(shooting lens). Reference numeral 1 denotes a reflecting plate divided into uneven parts as shown in FIG. 3, which is divided densely when the focus lens is located on the infinity side and sparsely divided when the focus lens is located on the close side. Reference numeral 2 denotes an equally divided reflecting plate shown in FIG. 3 and 4 correspond to the reflectors 1 and 2, respectively, and are photocouplers having light emitting parts 5 and 7 and light receiving parts 6 and 8. The photocouplers convert the brightness and darkness of the reflected light from the reflectors 1 and 2 into digital signals. (pulse) and communicated to the computer 12 via the comparison circuit 9.

The microcomputer 12 stops driving the motor when the number of pulses generated from the coupler 4 becomes equal to the number of pulses communicated from the computer 14 on the camera side.

Comparison circuit 9 calculates the pitch ratio of the signals of couplers 3 and 4 and communicates it to computer 12 .

The lens ROM 13 stores data corresponding to the signal pitch ratio and the focus lens position or object distance, and the microcomputer 12 recognizes the focus lens position. Note that A indicates a lens device and B indicates a camera body.

FIG. 2 is a configuration diagram showing the arrangement of the lens device A in the lens barrel.

A gear 17 is linked to the motor 10, and when the motor rotates by 1°, the recoid 18 is rotated to a fixed position via the gear 17. As the helicoid 18 rotates, the lens barrel 19 holding the focus lens 21 moves on the optical axis.

The helicoid 18 is coupled with a disc l having reflectors shown in FIGS. 3 and 4 attached to the front and back sides, and the helicoid 18
Rotates according to the rotation of. The helicoid 18 allows the lens to move from close range to infinity in less than one rotation.

22 is a fixed group of the photographing lens, 23 is a holding portion, and 24 is a main body.

Next, the operation of the present invention shown in FIG. 1 and FIG.
This will be explained using the program flow shown in the figure.

It is assumed that the program is built into the computer 14.

The program starts by pressing a release button (not shown).

In this program, in step 1, communication between the lens device A and the camera body B is performed.

Through this communication, the computer 14 has the lens ROM 1.
Data within 3 is input. At this time, lens constants (coefficient values indicating the relationship between defocus 1 and the amount of lens movement), etc. are input to the computer 14.

In step 2, the focus detection unit 16 sensor (CO
Image signals are accumulated for the image received by an image signal accumulation sensor such as D, and in step 3, the accumulated image signals are read out and AD converted.

The AD-converted image signal is input to the computer 14, a defocus amount d is calculated in step 4, and the defocus amount d and a constant value d are calculated in step 5. A comparison is made in size. If it is determined in this comparison that dl<Idol, the process moves to step 6, where a display means (not shown) is operated to display an in-focus display, and then the process returns to step 2, where the above-described operations are repeated.

Further, when it is determined in step 5 that ldl>1aolξ, the process moves to step 7, and the lens drive amount for focusing is determined based on the defocus amount d and the lens constant input via communication. In step 8, the number of pulses corresponding to the lens drive amount is communicated to the computer 12, and the motor IO is driven by the drive circuit. Motor 1
0 is driven, the helicoid 18 rotates, the lens 21 moves in the optical axis direction, and the disk 1- also rotates at a ratio of I to l due to the rotation of the helicoid.

With this, the light and dark pattern of the reflection plate 2 is detected by the fort coupler 4, and a pulse is generated from the fort coupler 4. Since this reflecting plate 2 has an equally divided pattern, a number of pulses proportional to the amount of rotation of the helicoid 18 are formed, and the pulses are detected by the computer 12. When the computer 12 detects that the number of pulses input from the coupler 4 matches the number of pulses input to the computer 12 according to the amount of lens drive, the drive of the motor 10 is stopped. Through the above operations, the lens is driven in accordance with the detected defocus amount, and the lens is driven to the in-focus position. After this, the step moves to 2 and the above operation is repeated.

When the lens is driven, the reflection plate 1 also rotates, and a pattern change due to this rotation is detected by the coupler 3 and a pulse is output. Since the pulse from the coupler 3 has an unevenly divided pattern on the reflection plate 1 and is directly connected to the helicoid 18, it indicates a predetermined pulse depending on the position of the lens.

On the other hand, since the pulse from the force blur 4 is constant in relation to the lens position, the absolute position of the l-nons can be detected by determining the ratio of the pulses from the coupler 3 and the coupler 4 in the comparator circuit 9.

That is, as shown in FIG. 6, the pulse P2 from the coupler 4
shows a constant width t1 regardless of the lens position, and the pulse P3 from the coupler 3 shows a pulse width t2 corresponding to the lens position. Therefore, - represents the absolute position of the lens.

FIG. 7 is a circuit diagram showing the configuration of the comparator circuit 9 shown in FIG.
), A2 is an AND gate, C1 and C2 are counters M, and M2 is a memory D1 is a divider. The counter C1 is a counter that inputs a count value into the memory M every time the clock pulse P1 in FIG. 6 finishes counting the clock pulse between the counter I and Lt1 during the pulse T1 of the pulse P2 in FIG. - side counter C2 is the 6th
This counter counts the clock P1 during t2 during the pulse P3 shown in the figure, and inputs the count value to the memory M2 every time the clock pulse count ends during t2. Therefore, the temperature information will be transmitted to the computer 12.

As described above, in the above embodiment, it is possible to detect the absolute position of the lens moved by autofocus.

〔Effect of the invention〕

As described above, in the present invention, the first and second pattern plates are provided that output unequally divided pulses and equally divided pulses in conjunction with the movement of the object, and the absolute position of the object is detected from the ratio of these pulses. , - The absolute position can be detected in multiple divisions using a set of readers. Further, since the position is determined by the pulse ratio as described above, even if the rotational speed of the motor (the moving speed of the object) changes, the position is always normalized and the position can be detected accurately.

In the second embodiment, an optical reflection type is shown, but a transmission type that receives transmitted light or a method of reading the pattern using a brush may also be used.

Further, although unequal division from dense to sparse is shown, pitches may be given in the order of dense and sparse, and position detection may be performed by comparing the rotation direction and the previous output value.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a camera system having a position detection device according to the present invention, FIG. 2 is a block diagram showing the configuration of the lens device shown in FIG. 1, and FIG. FIG. 4 is a configuration diagram showing the configuration of the reflecting plate 1 shown in the first diagram. FIG. 5 is a program flow diagram for explaining the operation of the camera system shown in the first diagram. FIG. 7 is a waveform diagram for explaining the present invention in detail, and FIG.
A circuit diagram showing the configuration of the illustrated comparison circuit 9, and FIGS. 8 and 9 are configuration diagrams showing the configuration of a conventional position detection device.

Claims (1)

[Claims] first and second pattern plates that are displaced relative to the pattern reader in conjunction with movement of the object;
A detection circuit is provided for detecting a ratio of pattern changes read by the reader of the pattern board, and detects the position of an object according to the ratio information of the pattern changes, and also arranges the first pattern board in an equally spaced pattern. A position detection device characterized in that the second pattern plate is set in a non-uniformly spaced pattern.