KR20000025881A - Device and method for location measurement using optical pickup - Google Patents

Abstract

PURPOSE: A device for location measurement using optical pickup and the method are provided to measure exactly the location and height of an object, measuring the location of an object lens. CONSTITUTION: A light source(21) generates light. A collimate lens(23) makes light radiated from light source horizontal light. A beam splitter(25) is installed to separate incident light and reflecting light at a part of the collimate lens(23). An object lens(27) projects light sequentially passing through the beam splitter(25) into an object(P) to be measured. A condenser lens(29) condenses reflecting light, separated from incident light and polarized through the beam splitter(25). A first light receiving part(31) picks up light passing through the condenser lens(29). A light emitting component(35) is fixed at part of a move means(33). A second light receiving part(37) is installed with a distance from the light emitting component(35).

Description

Position measuring device and method using optical pickup

The present invention relates to a position measuring apparatus and a position measuring method using an optical pickup.

In general, a compact disc player includes a light pick up device that detects the light returned from the disc after the laser light is incident on the disc surface, and an optical transmission device for radially moving the optical pickup device. .

In the optical pickup apparatus applied to the compact disc player, as shown in Fig. 1, the laser light emitted from the laser 1 becomes parallel light while passing through the collimate lens 3, and the parallel light After the light is collected from the objective lens 9 through the beam splitter 5 and the quarter wave tube 7, the reflected light is reflected on the reflective surface of the disk 11, and the reflected light is again reflected by the objective lens ( 9), and then through a quarter wave tube (7), and then 90 degrees in the beam splitter (5), the photodiode through the condenser lens (13) and the cylindrical lens (15) Photo diode 17 is reached to convert the light of the focus detection, track detection, and disk recording signals into an electrical signal.

The three-beam optical pickup apparatus using three laser beams by dividing the laser beam is provided with a diffraction grating 19 between the laser 1 and the collimated lens 3.

Due to the high-speed development of the modern electronic industry, high-performance, high-integration and shortened products are developed and produced in large quantities. The production process of these products basically requires a high-precision position measuring device for the assembly and performance testing of parts, but in the conventional industrial measurement, it requires a lot of facilities, effort and cost due to expensive parts purchase and high precision assembly. Attempts have been made to apply an optical pickup device applied to the compact disc player to industrial measurement.

However, there is a problem in that the optical pickup device applied to the compact disc player is applied to industrial measurement as it is.

That is, the optical pickup device applied to the conventional compact disc player also performs the focus detection and the track detection. However, in order to measure the position of the object in the industrial measurement, the problem of measuring the position of the objective lens also remains.

Accordingly, the present invention has been made to solve the above problems, and an object of the present invention is to provide a position measuring apparatus and method using an optical pickup to accurately measure the position and height of the object to be measured by measuring the position of the objective lens It is.

1 is a system diagram showing an optical pickup apparatus applied to a compact disc player;

2 is a system diagram showing a position measuring device using an optical pickup according to the present invention;

3 is a conceptual diagram illustrating a quadrant photodiode as a first light receiving unit of FIG. 2;

4 is a conceptual diagram illustrating a PSD that is a second light receiving unit of FIG. 2;

FIG. 5 is a schematic perspective view illustrating a tetra lateral type PSD as the second light receiving unit of FIG. 2;

6 to 8 are functional diagrams of the position measuring device using the optical pickup according to the present invention.

<Explanation of symbols for the main parts of the drawings>

21: light source 23: collimated lens

25: beam splitter 27: objective lens

29: condenser lens 31: first light receiver

33: moving means 35: light emitting element

37: second light receiving unit

The position measuring apparatus using the optical pickup according to the present invention includes a light source for generating light, a collimating lens for making the light emitted from the light source into parallel light, and a beam provided on one side of the collimating lens to separate incident light and reflected light. A splitter, an objective lens that projects light passing through the collimator lens and the beam splitter sequentially, onto an object to be measured, and collects reflected light that is polarized and separated from the incident light while passing through the beam splitter after being reflected from the object A position measuring device using an optical pickup having a condenser lens, a first light receiving portion for picking up light passing through the condenser lens, and a moving means for moving the objective lens,

The light emitting device is attached to one side of the moving unit, and the second light receiving unit is installed at a predetermined distance from the light emitting device so as to receive the light emitted from the light emitting device.

The light emitting device is the microchip LED or the electroluminescent device (EL).

The first light receiving unit is a photo diode, and a quadrant photodiode is preferable.

Wherein the second light receiving unit is a PSD (Position Sensitive Detector) or a photo diode (Photo Diode), the PSD is preferably a two-dimensional PSD that forms four output terminals, the port diode is a four-segment photodiode desirable.

As the PSD, a tetra-lateral type PSD may be used.

The Tetra-Lateral type PSD has four output terminals on four sides of the P layer of the PN junction layer, and photocurrent is output from four incident points through a uniformly distributed resistance layer. The output current is formed by the terminal.

In the position measuring method using the optical pickup according to the present invention, the light from the light source passes through the collimator lens to make parallel light, and then reflects the light reflected on the object to be measured through the beam splitter and the objective lens to reflect the reflected light. By passing through the objective lens and the beam splitter again, passing the condenser lens and detecting it at the first light receiving unit, and moving the objective lens to the moving unit to detect light emitted from the light emitting element attached to the moving unit at the second light receiving unit. It is characterized by finding the position of the object to be.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

As shown in Fig. 2, the position measuring apparatus using the optical pickup includes a light source 21 for generating light, a collimating lens 23 for making the light emitted from the light source 21 into parallel light, incident light and reflected light. To the object (P) to measure the light sequentially passed through the beam splitter 25 installed on one side of the collimating lens 23, the collimating lens 23 and the beam splitter 25 to separate the An objective lens 27 for projecting, a condenser lens 29 for condensing the reflected light polarized by being separated from the incident light while passing through the beam splitter 25 after being reflected from the object P; and the condenser lens 29 And a first light receiving portion 31 for picking up light passing through.

In addition, the objective lens 27 is installed to be movable by the moving means 33, the light emitting element 35 is attached to one side of the moving means 33, and the light emitting element 35 The second light receiving unit 37 is provided at a predetermined distance from the light emitting element 35 so as to receive light.

The light source 21 is preferably a laser for generating a laser beam, preferably a laser diode called a compact, lightweight and inexpensive semiconductor laser.

Since the laser diode is a semiconductor device, the light output increases when the temperature decreases, and the light output decreases when the temperature rises. Therefore, a laser output servo circuit (not shown) is coupled to the laser diode to continuously monitor the output of the laser and monitor the drive current to control the drive current. This laser output server circuit is provided with an inverting amplifier and a buffer to maintain a constant laser light intensity, and is a circuit applied to a known CD player.

The collimating lens 23 is a convex lens for converting divergent light emitted from the light source 21 into parallel light.

The beam splitter 25 is two oblique prisms arranged obliquely, and a polarizer is coated on one side of the prism in one direction, and the light component parallel to the incident surface is a polarizer on the slope. It is shielded by 90 degrees and reflected horizontally, and the light component perpendicular | vertical to an incident surface is going straight ahead.

The objective lens 27 is a convex lens that collects the light passing through the beam splitter 25 and reflects the light to the object, and makes the light reflected from the object into parallel light and passes the light to the beam splitter 25. .

A quarter wave tube (not shown) is disposed between the objective lens 27 and the beam splitter 25. The quarter-wave tube uses birefringence to change linearly polarized light into circularly polarized light, and conversely, a plate made of quartz is used as an optical component that converts circularly polarized light into linearly polarized light. .

The linearly polarized light that has passed through the beam splitter 25 becomes circularly polarized light while passing through the 1/4 wavelength tube, is reflected from the object P, and comes out in the opposite direction as it enters the object P. The direction of rotation is reversed. Therefore, the reflected light from the object P becomes a polarized wave of a reversely rotating circle and changes into linearly polarized light while passing through the 1/4 wavelength tube again. The polarization plane rotates 90 degrees with respect to the incident light. As a result, the polarization plane of the light passing through the beam splitter 25 is formed to be 90 degrees different from the incident light and the reflected light.

The condenser lens 29 is a convex lens that collects light.

The first light receiving unit 31 is a light-receiving element using a photovoltaic effect, which is a known photo diode, and a quadrant photodiode.

As shown in FIG. 3, the four-segment photodiode is arranged with four photodiodes 41, 42, 43, 44 based on the center of the circle, and each photodiode has a differential amplifier (Amp) ( 45) is connected to the optical signal output structure. At this time, the photodiodes disposed diagonally to each other are connected to the differential amplifier 45 by the same input line. That is, the photodiodes 41 and 43 and the photodiodes 42 and 44 are input to different input lines.

The differential amplifier 45 is coupled with a detection circuit (not shown) for sensing this output signal.

The moving unit 33 may wind a coil around the objective lens 27 to receive an output signal of the first light receiver 31, such as a voice coil of a speaker, to move the objective lens ( VCM). This voice coil motor is similar to the voice coil motor of a CD player.

The light emitting device 35 is formed of a chip LED or an electroluminescent device (EL), and a power supply circuit (not shown) is coupled to the light emitting device.

The chip LED is manufactured in the form of a known LED chip.

The electroluminescent device (EL) is a device that emits energy, that is, light that is generated when electrons move from the ground state to the lower energy level when energy is applied to an alloy of zinc and tin, manganese, etc. There are various types such as injection type EL and intrinsic EL which emit light by an electric field.

The second light receiver 37 is a position sensitive detector (PSD) or a photo diode, and may be a tetra-lateral type PSD or a four-part photodiode. The distance between the light emitting element 35 and the second light receiving portion 37 is reduced as much as possible to reduce the divergence of the light emitted from the light emitting element 35.

The four-segment photodiode of the second light-receiving portion 37 has the same structure as the four-segment photodiode of the first light-receiving portion 31.

As shown in Fig. 4, the PSD is an optical sensor capable of detecting the position of light in a spot shape, and basically a PN in which a P layer 52 and an N layer 54 are joined to convert incident light into an electrical signal. A semiconductor having a junction surface, and output terminals 56 and 58 bonded to the edge of the P layer 52 for outputting an electrical signal.

As shown in Fig. 5, the tetra-lateral type PSD has four output terminals 56, 58 and 66 on four sides of the P layer 52 of the PN junction layer. 68) and the photocurrent forms an output current with four output terminals from the incidence point position through a uniformly distributed resistance layer.

A differential amplifier or an output terminal of the second light receiver 37 is coupled to a light receiver circuit (not shown) for amplifying and calculating a weak signal to be input to a microcomputer or a computer.

In the position measuring device according to the present invention configured as described above, the position measurement of the object is measured by the following method.

That is, as shown in FIG. 2, when the position measuring device is installed so that the objective lens is positioned under the object P to be measured, and the operation switch is turned on, the laser light emitted from the laser of the light source 21 is turned on. Is parallel light passing through the collimate lens 23, and the parallel light is rotated 90 degrees in the beam splitter 25 and the objective lens (not shown) through a 1/4 wavelength tube (not shown). After the light is collected at 27, the light is reflected at the reflective surface of the object P, and the reflected light is converted into parallel light again through the objective lens 27, and then through the quarter wave tube, and then the beam splitter 25 ) And the condensing lens 29 reach the four-segment photodiode of the first light-receiving portion 31.

In this case, as shown in FIGS. 6 to 8, the image formed on the four-segment photodiode of the first light receiver 31 is different depending on the distance between the object P and the objective lens 27. ) Output is different.

That is, if the distance between the object P and the objective lens 27 is appropriate, the light path shown in the image side view of FIG. 6 proceeds to the circular path B1 at the center of the quadrant photodiode, whereby a differential amplifier ( 45) becomes 0, and if the distance between the object P and the objective lens 27 is too close, it proceeds to the optical path shown in the upper side drawing of Fig. 7, and the elliptical image in the longitudinal direction of the quadrant photodiode (B2) is formed, the output of the differential amplifier 45 becomes +, and if the distance between the object (P) and the objective lens 27 is too far, it proceeds to the optical path shown in the upper side figure of Fig. 8 divided into four photodiode An elliptical phase B3 is formed in the transverse direction of and the output of the differential amplifier 45 becomes-.

When the focus is not in focus as in FIGS. 7 and 8, the output of the differential amplifier 45 is transmitted to the voice coil motor VCM, which is the moving means 33, and as the moving means 33 moves, FIG. 6. This ensures that the image forms exactly in the center of the quadrant photodiode.

At this time, since the light emitting element 35 attached to the moving means 33 moves, the image formed on the second light receiving portion 37 is different, and thus, when the image is exactly formed at the focus of the first light receiving portion, the second light receiving portion 37 By using a microcomputer or a computer to process the signal output by the image bound to the PSD of), it is possible to accurately measure the position and height of the object (P).

Positioning by the PSD of the second light receiving portion 37 is performed as follows.

As shown in Fig. 4, when light enters the light-receiving surface 72 constituted by the PN junction surface, it appears as positive charges in the P layer 52 in the vicinity of the incident in the semiconductor, and negative charges in the N layer 54. . The uneven distribution of + charges in the P layer 52 causes charge transfer in the P layer 52, and at a distance from the point of incidence to the output terminals 56 and 58 at both ends of the P layer 52. The output is inversely proportional to the current.

here,

I ₁ = current at the first output terminal

I ₂ = current at the second output terminal

I ₀ = total current (I ₁ + I ₂ )

L = length between terminals

x = distance from the center between both terminals to the incidence position

Therefore, the incident position x can be obtained by the following equation.

The above equation shows a simple equation for obtaining the incidence position on one axis, and the incidence position can be simply obtained on the two axes according to the above basic principle.

That is, the incident position in the Y-axis direction in the Tetra-Lateral type PSD of Fig. 5 is obtained similarly to "Equation 2".

As the incident position is detected, the position and height of the object can be accurately known.

According to the position measuring device and method according to the present invention, the optical focusing principle makes it possible to accurately focus the first light-receiving unit and to measure the position of the objective lens in this state, thereby accurately positioning the position and height of the object to be measured. You can measure it.

Claims (7)

A light source for generating light, a collimator lens for making the light emitted from the light source into parallel light, a beam splitter provided on one side of the collimator lens to separate incident light and reflected light, and the collimator lens and the beam splitter An objective lens for projecting the light passing through to the object to be measured, a condensing lens for reflecting the reflected light separated from the incident light while passing through the beam splitter after being reflected from the object, and the light passing through the condensing lens In the position measuring apparatus using the optical pickup having a first light receiving unit for picking up the optical lens and a moving means for moving the objective lens, A light emitting device is attached to one side of the moving unit, and the second light receiving unit is provided at a predetermined distance from the light emitting device so as to receive the light emitted from the light emitting device. The method of claim 1, The light emitting device is a position measuring device using an optical pickup, characterized in that the chip (Chip) LED. The method of claim 1, The light emitting device is an electroluminescent device (Electro luminescence: EL) position measuring apparatus using an optical pickup, characterized in that. The method of claim 1, The second light receiving unit is a photodiode (Position Diode) or Position Sensitive Detector (PSD), characterized in that the position measurement device using the optical pickup. The method of claim 4, wherein The photodiode (Photo Diode) is a position measuring device using an optical pickup, characterized in that the four-segment photodiode The method of claim 4, wherein The PSD has four output terminals on four sides of the P layer of the PN junction layer, and the photocurrent is a two-dimensional PSD that forms an output current from the position of incidence to four output terminals through a uniformly distributed resistance layer. Position measuring device using an optical pickup, characterized in that the. The light from the light source is passed through the collimating lens to make parallel light, and then the light is reflected back to the object to be measured through the beam splitter and the objective lens, and the reflected light is passed back through the objective lens and the beam splitter. Optical pickup, characterized in that the position of the object to be measured by passing through the first light-receiving unit, the objective lens is moved to the motor to detect the light emitted from the light emitting element attached to the motor by the second light-receiving unit Position measurement method using.