JPH0432562Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a detector for detecting the position of a moving object such as a head used in a disk device such as a CD player or a video disk player.

2. Description of the Related Art Conventionally used head position detectors include those shown in FIGS. 4 and 5, for example.

A head 10, which is provided in the disk device A and moves linearly in the radial direction r of the disk, has a rack 11 on its side wall. Further, a pinion 22 that meshes with the rack 11 described above is fixed to a rotating shaft 21 of a variable resistor 20 fixed to the disk device A.

Therefore, when the head 10 moves in the radial direction r of the disk, the rotating shaft 21 of the variable resistor 20 rotates accordingly, changing its resistance value. The resistance value of this variable resistor 20 is input to a detection circuit (not shown) to detect the moving position of the head 10.

Problems to be Solved by the Invention However, in the above-mentioned head position detector, the mechanical rotational resistance of the rotating shaft 21
There have been problems in that the smooth displacement of the variable resistor 20 is disturbed and the accuracy of position detection is reduced due to electrical noise generated by the slider in the variable resistor 20.

Purpose of the invention This invention was made in view of the above-mentioned problems, and it is an object of the present invention to provide a moving position detector that can accurately detect the position of a moving object without interfering with the movement of the moving object. With the goal.

Means for Solving the Problems In order to achieve the above object, this invention uses a unidirectional lens that has the effect of diffusing a certain amount of parallel light flux emitted from a light source in one direction, and and a photoelectric conversion element that receives a part of the light flux diffused by the light beam, one of which is provided on a moving body that moves in a straight line, and the other is arranged so that it moves away from and approaches one as the moving body moves, It is characterized in that the moving position of the moving body is detected from the output of a photoelectric conversion element that changes with the movement of the moving body.

Function Since the position detector of this invention has the above-mentioned configuration, by detecting a part of the light beam diffused in one direction with the photoelectric conversion element, it is possible to detect the difference between the unidirectional lens and the photoelectric conversion element. The distance of the vehicle can be measured, and the moving position of the moving body can be detected from the measurement results.

The present invention will be described below with reference to the drawings.
The figure shows a first embodiment of the invention.

The disk device B includes a head 3 that records information on the disk or reads recorded information.
0 is set. This head 30 can be moved linearly in the radial directions r ₁ and r ₂ of the disk by a moving means (not shown) such as a DC linear motor.

Further, the fixed part B ₁ of the disk device B is provided with a light source 40 that emits a parallel light beam toward the head 30 and a cylindrical lens 41 that diffuses the parallel light beam only in one axis direction. A photodetector 42 is provided as a photoelectric conversion element that receives part of the light beam diffused by the cylindrical lens 41.

With such a configuration, when the head 30 moves in the radial direction _r1 of the disk, the cylindrical lens 41 and the photodetector 42 move away from each other, and the amount of light received by the photodetector 41 gradually decreases, while the head 30 moves in the radial direction r1 of the disk. When moving in the radial direction r ₂ , the cylindrical lens 41 and the photodetector 42 approach each other and the photodetector 4
2, the amount of light received increases gradually.

FIG. 2 shows a second embodiment of this invention.

In this example, the light source 40 that emits a parallel light beam in the moving direction of the head 30 is connected to the fixed part B ₁ of the disk device B.
A cylindrical lens 41 is provided on the head 30 to diffuse the light beam emitted from the light source 40. And cylindrical lens 41
A photodetector 42 as a photoelectric conversion element that receives the light beam diffused by the disk device B
It is provided in the fixed part _B1 of.

Even with this configuration, the cylindrical lens 41 and the photodetector 42 move away from and approach each other as the head 30 moves, so the amount of light received by the photodetector 42 can be changed as the head 30 moves.

Next, the principle of operation of the head position detector of the above embodiment will be explained with reference to FIG.

The parallel light beam emitted from the light source 40 passes through the cylindrical lens 41 and is diffused only in one axis direction at an angle of θ rad. Here, the total amount of light emitted from the cylindrical lens 41 is
P ₀ , the distance from the diffused focal point f to the photodetector 42 is R, and the amount of light received by the photodetector 42 is P, the relationship expressed as P∝P ₀ /Rθ holds true.

Further, when the photoelectric conversion coefficient of the photodetector 42 is G and the output current from the photodetector 42 is I, the relationship I∝GP ₀ /Rθ holds true.

Since the photoelectric conversion coefficient G, the light amount P ₀ and the diffusion angle θ are constant, the distance R from the diffusion focus f to the photodetector 42 can be determined by detecting the current I, and from this value the position of the head 30 can be determined. can be detected.

Note that when a cylindrical lens is used as the lens for diffusing the parallel light beam as in the above embodiment, the amount of light received by the photoelectric conversion element is inversely proportional to the distance between the lens and the photoelectric conversion element.
Since the output of the photoelectric conversion element changes slowly, accurate distance measurement can be performed over the entire movement range of the head.

Effects As explained above, the position detector for a moving object of this invention uses light as a detection means and eliminates mechanical contact with the moving object, so it does not interfere with the displacement of the moving object as in the past. , the position signal does not contain electrical or mechanical noise. In addition, since a unidirectional lens was used as a means of diffusing light,
An output that is inversely proportional to the distance can be obtained from the photoelectric conversion element, and the position can be accurately detected over a large movement range.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the head position detector according to this invention, FIG. 2 is a block diagram showing the second embodiment, and FIG. 3 is an explanatory diagram showing the operating principle of this invention. FIG. 4 is a plan view showing a conventional head position detector, and FIG. 5 is a side view of FIG. 4. B...Disk device, 30...Head, 40...
... light source, 41 ... cylindrical lens (lens), 42 ... photodetector (photoelectric conversion element), r ₁ , r ₂ ... radial direction of the disk.

Claims (1)

[Claims for Utility Model Registration] A unidirectional lens that has the effect of diffusing a certain amount of parallel light flux emitted from a light source in one direction, and a photoelectric conversion element that receives a part of the light flux diffused by the lens. one of them is provided on a movable body that moves in a straight line, and the other is arranged so as to move away from and approach the one as the movable body moves, and the photoelectric conversion element changes as the movable body moves. A moving position detector for a moving body, characterized in that the moving position of the moving body is detected from the output of the moving body.