JPS62275325A - Information reading method for optical card - Google Patents

Abstract

PURPOSE:To read information with high accuracy by shifting a lens and/or detector from a focused position by a prescribed amount accordant with the difference in heights of a prerecorded part and a write part and letting a head part focus approximately on the write part to read the information on the write part. CONSTITUTION:Ahead part 10 is displaced by piezoelectric elements 11 and 12 so that the outputs of differential amplifiers 21a and 21b are set at zero based on the outputs of comparators 22a and 22b. Thus the focus and tracking controls are given to the plane of a prerecord part 2. When these controls are through, the prescribed focus correction value is supplied to a D/A converter 24a from an arithmetic circuit 23 to focus a head part 10 approximately to a write part 3. Thus the output signal B is obtained from a light receiving area 18e in response to a pattern A of the part 3. Then the output signal C is obtained from a comparator 22c which gives waveform shaping to the signal B. The supply of the focus correction value DELTAi is cut off (D) for a short time synchronously with the rise of the output signal of the comparator 22c. Thus the tracking and focus controls are carried out on the plane of the part 2 while the supply of the value DELTAi is cut off.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] This invention relates to a method of reading information recorded on an optical card.

[Conventional technology]

Conventionally, as a method for reading information from an optical card, a method has been proposed that uses a pickup with a structure similar to that of a compact disc pickup, and uses this to read the information recorded on the optical card while performing tracking and focus adjustment. ing.

[Problem that the invention seeks to solve]

The above-described conventional information reading method is effective when the pre-record section for tracking in the optical card and the write section on which information is recorded are substantially on the same plane. However, as shown in a plan view in FIG. 6A and a cross-sectional view in FIG.
If it is formed below point a, when the pre-record section 2 is focused, the light section 3 will be out of focus, and when the light section 3 is focused, there will be a shift of focus for tracking, etc. There is a problem in that the focus on the record section 2 is shifted and the information cannot be read accurately. On the right, a transparent body 4 is adhered to the surface of the optical card 1.

This invention has been made with attention to such problems, and provides an information reading method for optical cards that can always accurately read information from optical cards in which the heights of the pre-record section and the write section are different. The purpose is to provide.

[Means and effects for solving the problem] In order to achieve the above object, the present invention projects illumination light in a spot shape onto an optical card having a pre-recording section and a light section having different heights. The reflected light from the pre-recording section is made incident on the detector through the lens, and while tracking and focus adjustment are performed using the reflected light from the pre-recording section, the lens and/or the detector is connected to the pre-recording section and the light section from the focus adjustment position. The information is optically read from the reflected light from the light section by displacing the light section by a predetermined amount corresponding to the difference in height between the light sections.

〔Example〕

FIG. 1 shows the configuration of an example of an information recording/reproducing apparatus for an optical card embodying the present invention. The head section 10 is conveyed in the direction shown by the arrow a through the focusing piezoelectric element 11 and the tracking piezoelectric element 12, and the direction perpendicular to the optical card 1 shown in FIGS. The optical card 1 is supported by a fixing member 13 so as to be movable in a direction perpendicular to the transport direction a of the optical card 1, that is, a direction perpendicular to the extending direction of the pre-recorded section 2 in the optical card 1.

The head section 10 includes a light emitting diode 14 and an illumination lens 1.
5, objective lens 16, half mirror 17, detector 1
8 and a laser diode 19. During reproduction, the light from the light emitting diode 14 is irradiated onto the optical card 1 in a spot shape by the illumination lens 15, and the reflected light from the optical card 1 is transmitted to the objective lens 16 and the half mirror 17. The output light of the radar diode 19 is modulated by the information to be recorded, and the half mirror 17 and the objective lens 16 are illuminated. The image is then projected onto the optical card 1.

As shown in a plan view in FIG. 2, the detector 18 has two light receiving areas 18a and 18b for focus control, two light receiving areas 18c and 18d for tracking control, and one light receiving area for information reading. It has a total of five light receiving areas including the light receiving area 18e. These light receiving areas 18a to 18
e is the light receiving area 18a with respect to the light receiving area 18e.

18b and the light receiving areas 18c and 18d are symmetrical, and when tracking and focusing on the pre-recording section 20 surface are performed correctly, the detector 18
For the light beam 14a incident on the light receiving areas 18a, 1
8c and the light receiving areas 18b and 18d respectively correspond to the adjacent pre-record section 2 as shown by virtual lines, and the light receiving areas 18a and 18b and 18G and 186 each receive the same amount of reflected light, and the tracking is performed in one direction. When the shift occurs in one direction, the amount of light incident on the light receiving area 18c decreases and that on the light receiving area 18d increases.On the other hand, when the shift shifts in the other direction, the relationship is reversed, and the focus shifts in one direction. When the light receiving area 18a shifts, the amount of light incident on the light receiving area 18a decreases, and the amount of light incident on the light receiving area 18b increases, and on the other hand, when the light shifts in the other direction, the relationship is reversed.

FIG. 3 shows a block diagram of the control circuit in this embodiment. The outputs of the light receiving regions 18a, 18b are supplied to a differential amplifier 21a via amplifiers 20a, 20b, and the output thereof is supplied to an arithmetic control circuit 23 via a comparator 22a. Similarly, the outputs of the light receiving regions 18c and 18d are sent to a differential amplifier 21 via amplifiers 20c and 20d.
b, and its output is supplied to the arithmetic control circuit 23 via the comparator 22b. Further, the output of the light receiving region 18e is supplied to the arithmetic control circuit 23 via the amplifier 20e and the comparator 22C.

The arithmetic control circuit 23 calculates the focus shift based on the output of the comparator 22a, and sends a signal corresponding to the shift to the focusing piezoelectric element 11 via the D/^ converter 24a.
The tracking deviation is calculated based on the output of the comparator 22b, and a signal corresponding to the deviation is sent to the tracking piezoelectric element 12 via the D/A converter 24b.
supply to. Further, the output of the comparator 22c is appropriately processed and outputted to the output terminal 25 as an information signal. In this embodiment, the head portion 10 is displaced via the piezoelectric element 11 based on the output of the comparator 22a, and the objective lens 1
6 focused on the surface of the pre-record section 2,
A predetermined amount of focus correction is supplied to the 0/A converter 24a, thereby displacing the head portion 10 by a predetermined amount via the piezoelectric element 11 to focus the objective lens 16 almost on the light portion 3, and correcting the focus. Focusing and tracking control on the surface of the pre-record section 2 is performed by turning the amount on and off based on the output of the comparator 22C.

The operation of this embodiment will be explained below.

First, based on the outputs of the comparators 22a and 22b, the outputs of the differential amplifiers 21a and 21b are set to zero.
The head section 10 is displaced by the piezoelectric elements 11 and 12 to perform focus and tracking control on the surface of the pre-record section 2. After this control is completed, a predetermined amount of focus correction is supplied from the arithmetic control circuit 23 to the D/A converter 24a, thereby causing the head section 10 to substantially focus on the light section 3.

In this way, an output signal as shown in FIG. 4 is obtained from the light receiving area 18e according to the pattern of the light section 3 shown in FIG.
2C outputs an output signal as shown in FIG. 4C.

In this embodiment, in synchronization with the rise of the output signal of the comparator 22C, the supply of the focus correction amount Ai is turned off for a short time as shown in the fourth diagram, and during that period, tracking and focus control are performed on the pre-record section 20 surface. After that, the focus correction amount li is supplied, and the output signal of the comparator 22C is taken in as information for the light section 3 while the head section IO is in a calm state. In this way, while performing focus and tracking control on the surface of the pre-record section 2 in synchronization with the rise of the output signal of the comparator 22c corresponding to the pattern of the light section 3, the focus position is corrected by the focus correction amount Al. to almost focus on the light section 3 and read the information.

Note that this invention is not limited only to the embodiments described above, and numerous modifications and changes are possible. For example, in the embodiment described above, the head portion 10 is
Although the displacement in the focus and tracking directions is carried out using an actuator such as a spring or a near motor used in conventional compact disc players, the displacement can also be carried out using an actuator using a spring or a near motor. Further, in the above-described embodiment, the entire head section 10 is displaced by the focus correction amount, but the objective lens 16 and/or the detector 18 are
0, and the objective lens 16 and/or
Alternatively, it is also possible to perform focus correction by displacing the detector 18 in the optical axis direction. Furthermore, instead of displacing the objective lens 16 and/or the detector 18, the detector 18 is moved as shown in FIG. An optical path length correction member 26 having a protruding portion corresponding to the light receiving area 18e may be provided on the front surface, or the light receiving surface of the light receiving area 18e corresponding to the light portion 3 of the detector 18 may be fixed to a pre-recorded portion as shown in FIG. It is also possible to correct the focus shift due to the difference in height between the pre-record section 2 and the light section 3 by making it protrude beyond the light-receiving surface of the light-receiving area 1g&-186 corresponding to the pre-record section 2 and the light section 3.

〔Effect of the invention〕

As described above, according to the present invention, while focusing and tracking is performed in the pre-record section, the lens and/or detector is moved from the focus position by a predetermined amount according to the difference in height between the pre-record section and the light section. Since the light section is displaced to almost focus on the light section and the information on the light section is read in that state, the information can always be read accurately.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an example of an information recording/reproducing device for an optical card embodying the present invention, FIG. 2 is a plan view of the detector shown in FIG. 1, and FIG. A block diagram of the control circuit, FIGS. 4A to 4D are diagrams showing its operation, FIGS. 5A and B are diagrams each showing a modification of the present invention, and FIGS. FIG. 3 is a plan view and a cross-sectional view of main parts of the card. 1... Optical card 1a... Reference surface 2... Pre-record section 3... Light section 4... Transparent body
10... Head parts 11, 12... Piezoelectric
13...Fixing member 14...Light emitting diode 15.
...Illumination lens 16...Objective lens 17...
Half mirror 18...Detector 18a-18
e... Light receiving area 19... Laser diodes 20a to 20e... Amplifiers 21a, 21b... Working amplifiers 22a to 22C... Comparator 23... Arithmetic control circuits 24a, 24b - D/A converter 25... Output terminal 26... Optical path length correction member Figure 1 Figure 2 Figure 5 A

Claims (1)

[Claims] 1. Illumination light is projected in a spot on an optical card having a pre-record section and a light section of different heights, and the reflected light from the optical card is incident on a detector via a lens to reflect the light from the pre-record section. While performing tracking and focus adjustment using light, the lens and/or detector is displaced from the focus adjustment position by a predetermined amount according to the difference in height between the pre-record section and the light section, and the reflected light from the light section is reflected. A method for reading information from an optical card, characterized by optically reading information from an optical card.