JP2856356B2 - Optical information reader - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical information reading apparatus for reading information recorded on an optical recording medium such as an optical card, a compact disk, and a video disk.

[Conventional technology]

Conventionally, various types of optical information reading apparatuses have been proposed. For example, Japanese Patent Application Laid-Open No. 56-83849 discloses that light from a light source is projected on an optical recording medium through a collimator lens, a beam splitter, and an objective lens. There is disclosed an apparatus in which the reflected light is received by a photodetector via an objective lens, a beam splitter, and a converging lens to read information.

[Problems to be solved by the invention]

In the conventional optical information reading device described above,
By arranging the light source at the focal position of the collimator lens, the light from the light source is converted into a parallel light beam by the collimator lens, and the parallel light beam is converged by the objective lens and projected onto the optical recording medium, and the reflected light is received. Based on the output of the detector, information recorded on the recording medium is read, and a tracking error signal for causing the read light to follow a track and a focus error signal for positioning the focal position of the objective lens on the recording medium. I'm trying to get

As described above, in the conventional optical information reading apparatus, since the light from the light source is projected as a parallel light beam onto the recording medium at the focal position by the objective lens, the spot of the reading light on the recording medium is Is extremely small. For this reason, there is a problem that an accurate tracking error signal or a focus error signal cannot be obtained depending on a reading position, and information cannot be accurately read due to a minute deviation of a track. In addition, when the width of one track is large as in an optical card, it is difficult to read information accurately.

The present invention has been made in view of such a conventional problem, and provides an optical information reading apparatus appropriately configured to always accurately read information recorded on an optical recording medium. Aim.

[Means and actions for solving the problem]

In order to achieve the above object, in the optical information reading apparatus of the present invention, a light source for emitting a light beam and an optical recording medium having a plurality of information tracks are irradiated with the light beam from the light source in a defocused state. Irradiating means; and detecting means for receiving reflected light of the defocused light beam from the optical recording medium and detecting information and a servo signal.

Further, an information reading light source irradiated with divergent light from a light emitting point, a beam splitter located at a position for receiving the divergent light, and performing at least one of reflection and transmission of incident light, and light from the beam splitter. The objective lens converges and radiates toward a recording medium on which information is recorded in a track shape, and guides light reflected by the recording medium to the beam splitter, and the recording medium reflected or transmitted by the beam splitter. In a position to receive the reflected light of
An optical information reading apparatus comprising: a converging lens for converging incident light; and a photodetector for receiving the light converged by the converging lens and generating a signal representing information recorded on the recording medium. In the above, a collimator lens is provided on an optical path connecting the light source and the beam splitter, and a focal position of the lens is arranged at a position shifted from a light emitting point of the light source, and light from the light source is diverged light or convergent light. So that the recording medium is irradiated in a defocused state, and the light detector receives reflected light of the divergent light or converged light irradiated in the defocused state on the recording medium, and performs tracking. An error signal or a focus error signal is generated.

〔Example〕

FIG. 1 shows the configuration of an optical system according to an embodiment of the present invention. In this embodiment, information recorded on an optical card 1 is read. Light read from a semiconductor laser 2 is converged on the optical card 1 via a collimator lens 3, an aperture 4, a beam splitter 5, and an objective lens 6. The light is projected, and the reflected light is received by a photodetector 8 via an objective lens 6, a beam splitter 5, and a converging lens 7. The semiconductor laser 2, the collimator lens 3, the aperture 4, the beam splitter 5, the converging lens 7, and the photodetector 8 are respectively held in a lens frame 9 and fixed to a base of an optical pickup in an optical card reader as described later. The objective lens 6 is held by a holder 10, and the holder 10 is supported on the base of the optical pickup so as to be displaceable in the optical axis direction of the objective lens 6 and in a direction orthogonal to the track of the optical card 1. The optical axis of the reading light is the optical card 1
So that it is perpendicular to

FIG. 2 shows an example of the configuration of the optical card 1. As shown in FIG.
The optical card 1 has two recording areas 11a and 11b formed on one surface thereof so that the information can be read by inserting the optical card reader into the optical card reader with the front and back reversed. In order to detect the relative position between the area and the reading position in the optical card reader, each of the recording areas 11a, 11
Position detection marks 12a and 12b are formed corresponding to b.
In each of the recording areas 11a and 11b, a number of tracks are formed extending in the direction of insertion into the optical card reader, and seek sections 13a and 13b in which track numbers and the like are recorded at both ends of these tracks. , 14a; 14b, and data portions 15a, 15b in which required information is recorded between the seek portions. Each track has one recording area in FIG.
2 divided into almost equal intervals to show the track 16 of 11a
It has 0 lines, and for 10 lines counted from the top, for a clock generation consisting of a black pattern at equal intervals formed over the seek portion 13a, the data portion 15a and the seek portion 13b,
It has a clock pattern 17 for focus error detection and tracking error detection. In addition, seek unit 13a,
13b, a tracking number 18 is formed with the first, third to fifth and 15 to 19th lines, and a track number pattern indicating a track number for identifying a track is formed here, and a second, sixth to eighth , 12 to 14 and 20 lines, a pattern recognition unit 19 is formed, and a fixed recognition pattern common to each track for recognizing a track number pattern is formed here. In this example, the recognition pattern is such that the second, eighth, twelfth, and twenty lines are white (binary data “1”), and the sixth, seventh, thirteenth, and fourteenth lines are black (binary data “0”). The track number pattern of the track number 18 is read when this recognition pattern is read. This recognition pattern exists only in each track 16, and the same pattern does not exist over two tracks.

Further, in the data section 15a, each track 16 is provided with a plurality of frames 20, and a frame number 21 is formed between adjacent frames and between the seek sections 13a, 13b and the frame 20. A frame number pattern for confirming each frame is formed. Also,
A black frame synchronization line 22 for obtaining a frame synchronization signal is formed on the twentieth line in each frame. In this manner, in this example, the first to eighth lines above the clock pattern 17 and the 12th to 19th lines below constitute a byte consisting of 8 bits, and these data are synchronized with the black clock pattern 17. They are read at the same time. The track in the other recording area 11b is formed similarly.

In this embodiment, a desired track is sought by moving an optical pickup in a direction orthogonal to a track of the optical card 1 and reading a seek portion, and information recorded in a data portion of the track is transferred to the optical card 1. Move in the track direction and read.

FIG. 4 shows an example of the configuration of the photodetector 8 shown in FIG. 1 when reading the optical card 1 having the track format shown in FIG. The photodetector 8 includes light receiving regions 25-1 to 25-17 arranged in the width direction of the track corresponding to lines 1 to 8 and 12 to 20 of the track, respectively.
And four pairs of clock generating light receiving areas 26-1 to 26-8 which are symmetrical with respect to the arrangement direction of these light receiving areas and are arranged in the track direction corresponding to the clock pattern 17, similarly to the light receiving areas 25-1 to 25-8. -17, two pairs of focus and tracking light receiving regions 27-1 to 27-4 arranged in the track width direction so as to be able to receive images of a plurality of clock patterns 17, respectively. .

Thus, in the seek operation of the track,
While moving the optical pickup in the direction perpendicular to the track in the seek section 13a, 13b, 14a or 14b, based on the output of the light receiving areas 25-1 to 25-17 of the photodetector 8, namely, the light receiving area 25-2, At the time when 25-6 to 25-11 and 25-17 detect a predetermined recognition pattern, the light receiving areas 25-1, 25
-3 to 25-5, 25-12 to 25-15 and 25-16 detect the track number pattern and seek a desired track. If the track number pattern is read when the recognition pattern is detected in this way, only one recognition pattern exists in each track 16 as described above, and the recognition pattern does not exist over two tracks. Therefore, the track number can be reliably recognized.

In reading data in the data section 15a or 15b, the optical card 1 is moved in the track direction,
Based on the difference between the sum of the outputs of the light receiving areas 26-1, 26-3, 26-5, 26-7 and the sum of the outputs of the light receiving areas 26-2, 26-4, 26-6, 26-8. In synchronization with the obtained clock signal, the light receiving areas 27-1,
A tracking error signal is detected from the difference between the sum of the outputs of 27-3 and the sum of the outputs of the light receiving areas 27-2 and 27-4, and based on this, a tracking servo is performed so that the reading light follows the track. The focus error signal is detected from the difference between the sum of the outputs of the light receiving areas 26-1 to 26-8 and the sum of the outputs of the light receiving areas 27-1 to 27-4. While performing focus servo so as to be positioned on the optical card 1, the light receiving area 25-1 is controlled under the control of the frame synchronization signal obtained from the output of the light receiving area 25-17.
Read the output of ~ 25-16 to reproduce the data.

For this reason, in this embodiment, the semiconductor laser 2 in FIG. 1 is adjusted so that the major axis direction of the reading light having an elliptical cross section emitted from the semiconductor laser 2 is the width direction of the track of the optical card 1. The lens 4 is mounted on the lens frame 9 such that the light emitting point 2a is located slightly before the focal position 3a with respect to the collimator lens 3, and the aperture 4 is detected in the short-axis direction of the reading light having an elliptical cross section. The portions corresponding to the light receiving areas 27-1, 27-2 and 27-3, 27-4 of the device 8 are arranged symmetrically so as to shield light, respectively. In this way, the reading light transmitted through the collimator lens 3 becomes slightly divergent light, and the light flux converges ahead of the focal position 6a of the objective lens 6. Therefore, the reading light is radiated on the optical card 1 in a defocused state, and the irradiation area is large enough to illuminate the track of the optical card 1.

FIGS. 5A, 5B and 5C respectively show the light spot states of reading on the optical card 1 projected on the photodetector 8 in this embodiment. The illuminance is equal to the illuminance near the front end of the corresponding light-shielding portion 4a. FIG. 5A shows a focused state in which the focal position 6a of the objective lens 6 is on the optical card 1. When the optical card 1 is displaced downward in FIG. As shown in FIG. 5C, when the irradiation area of the reading light is reduced, and when the reading light is displaced upward to be in the back focus state, the irradiation area of the reading light is increased as shown in FIG. 5C. Therefore, in the focused state shown in FIG. 5A, the difference between the sum of the outputs of the light receiving areas 26-1 to 26-8 of the photodetector 8 and the sum of the outputs of the light receiving areas 27-1 to 27-4 is If it is set to be zero, the front focus state shown in FIG.
Since a focus error signal having a different polarity from the back focus state shown in FIG. C is obtained, by performing a focus servo that displaces the objective lens 6 in the optical axis direction so that the focus error signal becomes zero based on this, Information can always be read in the focused state shown in FIG. 5A. When the optical card 1 is separated from the objective lens 6 and the front focus state advances, the irradiation area of the reading light gradually increases,
The polarity of the focus error signal is inverted, and a focus error signal similar to that in the back focus state is output. The focus servo is performed in a direction in which the objective lens 6 moves away from the optical card 1 so that focus adjustment cannot be performed. Such a defect,
When the focus error signal indicates the rising direction while the objective lens 6 is at the rising limit, for example, the
In the case where the digital signal corresponding to the focus error signal from the U or the like is A / D converted and driven, when the digital value exceeds a certain value, the signal for lowering the objective lens 6 until the focus error signal is reversed. Can be effectively solved by forcibly giving a focus search and performing a focus search.

FIGS. 6A and 6B are a side view and a perspective view showing the overall configuration of an optical pickup having the optical system shown in FIG. The lens frame 9 to which the semiconductor laser 2, the collimator lens 3, the aperture 4, the beam splitter 5, the converging lens 7, and the photodetector 8 shown in FIG. 1 are mounted is fixed to a base 31 made of a magnetic material. The holder 10 for holding the objective lens 6 is provided in the optical axis direction (focus direction) of the objective lens 6.
And a support portion 33 provided on the base 31 via four wires 32 so as to be displaceable in a direction (tracking direction) orthogonal to the focus direction and orthogonal to the track of the optical card.
To support. A focus coil 34 for driving the objective lens 6 in the focus direction is mounted on the side of the holder 10 opposite to the tracking direction integrally with the holder 10, and is integrated with the holder 10 on the outer periphery of the focus coil 34. A tracking coil 35 for driving the objective lens 6 in the tracking direction is mounted. As shown in FIG. 7, for example, these tracking coils 35 are constituted by printed coils formed by printing on a flexible substrate 36.
The lands that connect the ends of the focus coil 34 to the focus coil 34 and the tracking coil 35
These wires 32
Lands and the like for connecting one end of each of them are formed.

The base 31 is provided with yokes 37 so as to penetrate into the pair of focus coils 34, respectively.
The permanent magnets 38 are fixedly opposed to each other via the focus coil 34 and the tracking coil 35. In this way, a magnetic flux is generated across the focus coil 34 and the tracking coil 35 on both sides of the holder 10, and the magnetic flux is compared with the focus error signal and the tracking error signal supplied by the focus coil 34 and the tracking coil 35, respectively. Focus servo and tracking servo are performed by electromagnetic action, and a focus search is performed by supplying a required signal to the focus coil.

Further, in order to move the base 31 in the track arrangement direction of the optical card so that a desired track can be sought, a protrusion 31a is formed at one end of the base 31 and the pins 41 are formed.
The leaf spring 42 is fixed, and the projecting portion 31a and the leaf spring 42 are slidably engaged with the guide member 43 so as to sandwich the guide member 43 which is fixedly provided extending in the track arrangement direction. . Also, the other end of the base 31 is provided with a rotatable screw screw extending in the track arrangement direction.
A projecting portion 31b projecting upward from the screw screw 44 and a receiving portion 31c projecting downward are formed so as to sandwich the screw 44, and a leaf spring 46 is attached to the projecting portion 31b via a screw 45, and both ends of the leaf spring 46 are provided. The pins 47 are respectively attached to the portions so as to engage with the screw grooves of the screw screws 44. A lubricating sheet 48 is interposed between the receiving portion 31c and the screw screw 44 so that the base 31 can easily move in the axial direction of the screw screw 44. The screw 44 is connected to the output shaft of the motor 50 via a worm gear 49.

In this way, the motor 50 is driven to
By rotating 44, the optical pickup is moved in the arrangement direction of the tracks of the optical card.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications or changes can be made. For example, in the above-described embodiment, the optical card is read. However, the present invention is not limited to the optical card, and can be applied to reading of various optical recording media, and the track configuration uses a corresponding photodetector. Can be dealt with more easily. For example, when a track is formed by a row of pits such as a compact disk or a video disk, a recording medium 51 and a photodetector 52 are shown in FIG.
As described above, the reading light 53 having an elliptical cross section emitted from the semiconductor laser is illuminated in a defocused state on the recording medium 51 so that the major axis thereof is in the track direction. In addition, the photodetector 52 that receives the reflected light from the recording medium 51 is separated from each other in the track direction so as to correspond to the track to be read and has two light receiving areas 54-1 and 54-2 for reading information. A plurality of pits at both edges corresponding to the track to be read and the adjacent track
Two light receiving areas 5 for tracking facing each other over 51a
5-1 and 55-2, and three light receiving areas 56-1 to 56-3 for focusing extending in the track direction corresponding to between the tracks.
Information is read based on the outputs of the light receiving areas 54-1 and 54-2, and a tracking error signal is detected based on the output difference between the light receiving areas 55-1 and 55-2.
The focus error signal is detected based on the difference between the sum of the outputs of 56-1 and 56-3 and the output of the light receiving area 56-2. Even when the track is formed by a single row of pits, by irradiating the reading light in a defocused state, the focus error signal and the tracking error signal can always be detected stably, and the information can be always accurately obtained. Can be read.

Further, in the above-described embodiment, the reading light from the semiconductor laser 2 is transmitted by the beam splitter 5 and guided to the optical card 1, and the reflected light from the optical card 1 is reflected and guided to the photodetector 8. However, the positional relationship between the semiconductor laser 2 and the collimator lens 3 and the converging lens 7 and the photodetector 8 is reversed, and the reading light from the semiconductor laser 2 is reflected by the beam splitter 5 to guide the light to the card 1. The reflected light from the optical card 1 may be transmitted through the beam splitter 5 and guided to the photodetector 8. Further, a beam splitter 5 having a polarizing film may be used, so that return light does not enter the semiconductor laser 2 so that the light beam can be used effectively. In addition, the stop 4 can be provided in an arbitrary optical path, and can be omitted. Further, in the above-described embodiment, the elliptical sectional shape of the reading light emitted from the semiconductor laser is effectively used by using the semiconductor laser. However, the shape of the reading light applied to the recording medium is circular. Therefore, light emitted from the semiconductor laser may be shaped into a circle by a prism or the like, or a light source other than the semiconductor laser may be used. Furthermore, in the above-described embodiment, the reading light is irradiated onto the optical card 1 in a defocused state by arranging the semiconductor laser 2 such that the light emitting point 2a is located before the focal position 3a of the collimator lens 3. However, the semiconductor laser 2 is arranged so that the light emitting point 2a is located behind the focal position 3a of the collimator lens 3, and the optical card 1 is similarly defocused.
Can be illuminated.

〔The invention's effect〕

As described above, according to the present invention, since the recording medium is irradiated with the defocused light beam on the recording medium, the illuminated area on the recording medium can be enlarged, and therefore recording can be performed regardless of the track width. The information signal on the medium can always be read accurately, and the servo signal of the tracking error signal or the focus error signal can always be detected stably.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an optical system according to an embodiment of the present invention. FIG. 2 is a plan view showing an example of the configuration of the optical card shown in FIG. 1. FIG. FIG. 4 is a diagram showing an example of the photodetector shown in FIG. 1, and FIGS. 5A, 5B and 5C are reading on an optical card projected on the photodetector in FIG. 6A and 6B are side views and a perspective view, respectively, showing the configuration of an example of an optical pickup having the optical system shown in FIG. 1, and FIGS. 6A and 6B are FIGS. FIG. 8 is a diagram showing an example of the tracking coil shown in FIG. 8, and FIG. 8 is a diagram for explaining a modification of the present invention. DESCRIPTION OF SYMBOLS 1 ... Optical card, 2 ... Semiconductor laser 3 ... Collimator lens, 4 ... Stop 5 ... Beam splitter, 6 ... Objective lens 7 ... Convergent lens, 8 ... Photodetector

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Claims (2)

(57) [Claims] A light source for emitting a light beam; an irradiating means for irradiating the optical recording medium having a plurality of information tracks with a light beam from the light source in a defocused state; Detecting means for receiving reflected light from the optical recording medium and detecting an information signal and a servo signal; 2. An information reading light source from which a divergent light is emitted from a light emitting point; a beam splitter located at a position for receiving the divergent light, and performing at least one of reflection and transmission of incident light; The objective lens guides the light reflected by the recording medium to the beam splitter, and the light is reflected or transmitted by the beam splitter. A converging lens located at a position for receiving the reflected light from the recording medium and converging the incident light; and receiving the light converged by the converging lens and generating a signal representing information recorded on the recording medium. An optical information reading apparatus including a photodetector, wherein a collimator lens is provided on an optical path connecting the light source and the beam splitter, and a focal point of the lens is provided. A light source from the light source, the light source emits light from the light source as divergent light or convergent light, and the recording medium is irradiated in a defocused state. An optical reading device configured to receive a divergent light or a convergent light irradiated in the defocused state and reflected from the recording medium and generate a tracking error signal or a focus error signal.