JPH01303637A - Optical information reader - Google Patents

Abstract

PURPOSE:To always obtain a correct servo signal by providing a cylindrical lens in the light path between a light emitting diode and a recording medium and irradiating so that a reading light can become an elliptical shape with a track width direction as a long axis on a recording medium. CONSTITUTION:The reading light from a light emitting diode 1 is irradiated through a first cylindrical lens 2 with a short focus distance having a lens action in a paper surface and a second cylindrical lens 3 with a long focus distance having a lens action in the paper surface vertical direction onto an optical card 4. Spot irradiation is executed to the elliptical shape with the track width direction as a long axis, so as to incline from the track direction and illuminate sufficiently the track and the image is image-formed through an objective lens 5 onto a light detector 6. Thus, since a mark image with a small blurring can be formed on the light detector 6, a servo signal can be always detected with a high accuracy and the information can be always surely read.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical information reading device for reading information recorded on an optical recording medium such as an optical card, a compact disc, or a video disc.

[Conventional technology]

Various types of optical information reading devices have been proposed in the past, and the present applicant also proposed, for example, in Japanese Patent Laid-Open No. 62-275325, a method in which light from a light emitting diode passes through an objective lens onto an optical card having a guide track and is tilted from the track direction. The image is received by a photodetector, and the data is read while performing servo control to correct the relative positional deviation between the objective lens and the optical card using the guide track image. 63-7533 discloses that an optical card having a clock pattern in the track direction is irradiated with light from a light emitting diode obliquely from the track direction through an objective lens in the same manner as described above, and the image is received by a photodetector to generate a clock. We have proposed a device that reads data while performing servo control to correct relative positional deviation between the objective lens and the optical card using a pattern image.

[Problem to be Solved by the Invention] However, in the above-mentioned conventional optical information reading device, the light from the light emitting diode is irradiated obliquely from the track direction so as to form a circular shape on the optical card using the objective lens. As a result, the mark image of the guide track and clock pattern formed on the photodetector becomes blurred at the periphery in the track direction, making it impossible to obtain accurate servo signals and making it difficult to always read information reliably. The problem is that it can't be done.

The present invention has been made by focusing on such conventional problems, and provides an optical information reading device that is appropriately configured so that accurate servo signals can always be obtained and therefore information can always be read reliably. The purpose is to

[Means and effects for solving the problem] In order to achieve the above object, in the present invention, a spot of reading light from a light emitting diode is irradiated onto a recording medium having a predetermined mark in the track direction at an angle from the track direction, In an optical information reading device, the image is received by a photodetector and information is read while performing servo control to correct relative positional deviation between the reading light and the recording medium based on the image of the mark. A cylindrical lens is provided in the optical path between the light emitting diode and the recording medium, so that the reading light is irradiated onto the recording medium in an elliptical shape with the long axis in the track width direction.

〔Example〕

FIG. 1 shows the configuration of an optical system according to an embodiment of the present invention. In this embodiment, reading light from a light emitting diode 1 is transmitted through a first cylindrical lens 2 having a short focal length and a second cylindrical lens having a long focal length and having a lens effect in the direction perpendicular to the plane of the paper. A spot is irradiated onto the optical card 4 through a cylindrical lens 3 in an elliptical shape whose major axis is in the track width direction so as to be tilted from the track direction and the long axis is in the track width direction. An image is formed on the detector 6.

FIG. 2 shows the configuration of an example of the optical card 4. As shown in FIG. This optical card 4 has two parts on its surface so that it can be inserted into an optical card reader equipped with an optical pickup having an optical system shown in FIG.
recording areas 11a.

In addition, position detection marks 12a and 12b are formed corresponding to each recording area 11a and llb in order to detect the relative position between the recording area to be read and the reading position on the optical card reader. .

Further, a large number of tracks are formed in each of the recording areas 11a and llb 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; 14
data portions 15a and 15b in which required information is recorded are formed between the seek portions. Each track has 19 lines divided at approximately equal intervals, as shown in the track 16 of one recording area 11a in FIG. , a clock pattern 17 for clock generation consisting of equally spaced black patterns formed over the data section 15a and the seek section 13b. Also, a seek section 13a.

A track number pattern representing a track number is formed on the track 13b, and a fixed recognition pattern common to each track for recognizing this track number pattern is also formed.

Further, in the data section 15a, each track 16 is provided with a plurality of frames 18, and each frame is recognized between adjacent frames and between the seek sections 13a, 13b and the adjacent frame 18. A frame number pattern has been created for this purpose. In this way, in this example, the first to
The 8th line and the 12th to 19th lines below each constitute a byte of 8 bits, and these data are read simultaneously in synchronization with the black clock pattern 17. Tracks in the other recording area 11b are similarly formed.

FIG. 4 shows an example of the configuration of the photodetector 6 shown in FIG. 1 when reading the optical card 4 having the formats 1 to 1 shown in FIG. 3.

The photodetector 6 includes tracks 1 to 8 lines and 12 to
Light receiving areas 25-1 to 25-16 for reading data are arranged in the width direction of the track corresponding to each of the 19 lines, and are arranged symmetrically with respect to the arrangement direction of these light receiving areas and corresponding to the clock pattern 17. Three pairs of light receiving regions 26-1 to 26-6 for clock generation are arranged and provided in the track direction. Similarly, the light receiving areas 25-1 to 25-1
6, and spaced apart in the track width direction so as to receive the images of the plurality of clock patterns 17, respectively.
7-1 to 27-4 are provided.

In this embodiment, as described above, the reading light from the light emitting diode 1 is directed onto the optical card 4 by the first and second cylindrical lenses 2 and 3 so that it is tilted from the track direction and the long axis is in the track width direction. Irradiate in an elliptical shape.

Therefore, an elliptical spot image as shown by reference numeral 28 in FIG. 4 is formed on the photodetector 6. Here, the spot image 28 is a spot image 2 formed when the track is converged and illuminated in a circular shape by an objective lens.
Since the width in the track direction is smaller than that in the spot image 29, the amount of blur in the peripheral portion in the track direction is smaller in the spot image 28 than in the spot image 29.

In the above configuration, when the optical card 4 is displaced in its normal direction, the spot image 28 formed on the photodetector 6 is
In the figure, the light receiving areas 27-1, 27-
The ratio of the clock pattern images formed on the clock patterns 2, 27-3, and 27-4 changes. Therefore, the sum of the outputs of light receiving areas 27-1 and 27-2 and the output of light receiving area 2
7-3 and the sum of the outputs of 27-4 is detected, and based on the difference output, it is determined based on the difference output when the optical card 4 is at a predetermined position with respect to the first and second cylindrical lenses 2.3. A varying focus error signal can be obtained. Furthermore, when the optical card 4 is displaced in a direction perpendicular to the track,
The spot image 28 formed on the photodetector 6 is shifted in the vertical direction in FIG. 4, and the formation position of the clock pattern image with respect to the light receiving areas 27-1 to 27-4 changes. Therefore, if the difference between the sum of the outputs of the light-receiving areas 27-1 and 27-3 and the sum of the outputs of the light-receiving areas 27-2 and 27-4 is detected, the clock pattern image is determined from the difference output.
It is possible to obtain a tracking error signal that changes based on the positions evenly located on 7-1 to 27-4.

As described above, in this embodiment, in the track seek operation, the optical pickup having the optical system shown in FIG.
While moving in the direction perpendicular to the track at b,
When a predetermined recognition pattern is detected based on the outputs of the light receiving areas 25-1 to 25-16 of the photodetector 6, a track number pattern is detected and a desired track is sought.

Furthermore, when reading data in the data section 15a or 15b, while moving the optical card 4 in the track direction, the light receiving areas 26-1, 26-3, and 26-
The sum of the outputs of 5 and 26-2, 26-4 and 26-6
A clock signal is obtained based on the difference between the sum of the outputs of , and in synchronization with this clock signal, the optical system shown in FIG. A focus that is located at a predetermined position relative to the optical card 4 and displaces the entire optical system in the focus direction, which is the normal direction of the optical card 4, and in the tracking direction, which is perpendicular to the track, so that the reading light accurately follows the desired track. While performing servo and tracking servo, the outputs of the light receiving areas 25-1 to 25-16 are read and data is reproduced.

According to this embodiment, since the amount of blur in the clock pattern image formed on the photodetector 6 can be extremely small, the focus error signal and the tracking error signal can always be detected with high precision, and therefore information can always be read reliably. be able to. Note that the ratio of the short axis and long axis of the spot image 28 formed on the photodetector 6 is set to, for example, 1:1 so that the amount of blur in the clock pattern image is small and a sufficient number of clock pattern images can be obtained. 3 to l: Set within the range of 1.5.

FIG. 5 shows the configuration of an optical system according to another embodiment of the invention. In this embodiment, the reading light from the light emitting diode 1 is transmitted to the first . The image is incident on the prism 31 through the second cylindrical lens 2.3, reflected diagonally downward at the prism 31 and irradiated onto the optical card 4, and the image is incident on the reflection mirror 32 via the objective lens 5. The photodetector 6 is reflected by the reflecting mirror 32 in a substantially horizontal direction.
The other configuration is the first one.
This is similar to the example. With this configuration, the height of the optical system in the normal direction of the optical card 4 can be reduced.
The entire device can be made thinner. Furthermore, since the angle formed by the optical axes of the reading light incident on the optical card 4 and the reflected light can be easily set to an acute angle (for example, 30" to 40 degrees), the image of the track can be more clearly displayed on the photodetector 6. Therefore, focus error signals and tracking error signals can be detected with higher precision, and information can always be read accurately.

Note that this invention is not limited only to the embodiments described above, and numerous modifications and changes are possible. For example, in the above embodiment, two cylindrical lenses were used to shape the reading light from the light emitting diode into an elliptical shape, but it could be shaped into an ellipse by using a colinota lens and one cylindrical lens, or by adding a converging lens. It is also possible to configure the beam to be shaped into a shape. In addition, the servo signal detected from the mark formed on the recording medium may be either a focus error signal or a tracking error signal, and the recording medium is not limited to an optical card, but also other optical disks such as optical disks and magneto-optical disks. It can also be effectively applied when using a type recording medium.

〔Effect of the invention〕

As described above, according to the present invention, a mark image with less blur can be formed on the photodetector, so that servo signals can always be detected with high precision, and therefore information can always be read reliably.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an optical system according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of the optical card shown in FIG. 1, and FIG. 3 is a diagram showing an example of its track format. FIG. 4 is a diagram showing the configuration of an example of the photodetector shown in FIG. 1, and FIG. 5 is a diagram showing the configuration of an optical system of another embodiment of the present invention. 1... Light emitting diode 2... First cylindrical lens 3... Second cylindrical lens 4... Optical card 5... Objective lens 6...
・Photodetector 16...Track 17...Clock pattern 28...Spot image 31...Prism 32...Reflection mirror Fig. 1 Fig. 2

Claims (1)

[Claims] 1. A spot of reading light from a light emitting diode is irradiated onto a recording medium having a predetermined mark in the track direction at an angle from the track direction, the image is received by a photodetector, and the reading is performed based on the image of the mark. In an optical information reading device that reads information while performing servo control to correct relative positional deviation between light and a recording medium, a cylindrical lens is provided in an optical path between the light emitting diode and the recording medium, An optical information reading device characterized in that the reading light is configured to irradiate the recording medium in an elliptical shape with the long axis in the track width direction.