JPS5850630A - Signal detector in optical information reader - Google Patents

Abstract

PURPOSE:To obtain a focus error signal accurately and easily by making reflected light incident to three photodetectors arrayed in a bit direction. CONSTITUTION:A photodetector 11 consists of three detectors 11a-11c, which are arrayed in a bit 7 direction. The differential output of the photodetectors 11a and 11b by the light spot 13 when an optical pickup and an optical disc are at an adequate spacing is a focus error signal. An information signal is obtained by the total sum of the three photodetectors 11a-11c. A tracking error signal is obtained by bisecting the photodetectors 11a and 11c by the straight line in the bit direction, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a focus control signal and information signal detection device for an optical information reading device.
For example, as shown in FIGS. 1, 2(a) and 2(b), two photoelectric elements 1 whose joints are perpendicular to the tracking direction
′, 2′ are irradiated with a reflected beam 8′ from the information medium,
The center of the irradiation spot 4' of this reflected beam 8' is shifted from the junction 5', and the reflected beam is on the optical path side of the photoelectric element 1' which receives a larger amount of light among the photoelectric elements 1' and 2'. A light-shielding plate 6' is provided in the section, and by changing the gap between the information medium and the focusing lens, the diameter of the irradiation spot on the information medium changes from 7' to 7'', and accordingly, the photoelectric elements 1', Utilizing that the irradiation spot on 2' changes from 4' to 4'', the difference in the amount of light received by the two photoelectric elements 1' and 2' is detected, and this detection signal is used to detect the gap between the information medium and the focusing lens. There are things that try to control it. This method has a simple structure and easy focus control detection, but when detecting the information signal, a part of the reflected beam 8' is cut off by the light shielding plate 6', so as shown in FIG. As shown in a) and (b), the end of the bit 8' forming the information track (the left end or right end in the figure varies depending on the width and shallowness K of the bit) 8'
There is a drawback that a cannot be detected reliably and an accurate information reproduction signal cannot be detected.

In view of the above points, it is an object of the present invention to provide a signal detection device in an optical information reading device that can accurately and easily detect information signals and focus control signals.

Preferred embodiments of the present invention will be described below with reference to the drawings.

A light beam 2 emitted from a light source 1 passes through a lens 3, a polarizing beam splitter 4, a quarter-wave plate 5, and a focusing lens 6, and the focusing lens 6 converts the light beam into an information track 7 in a known manner. The formed information medium 8 is irradiated as an irradiation spot 9.

The reflected beam 10 that has irradiated the information medium 8 passes through the converging lens 6 and quarter-wave plate 5 again, and enters the photodetecting element 11 via the lens 12 at the polarizing beam splitter 4 . In this embodiment, the photodetecting element 11 is composed of eight photoelectric elements 11aqllbqlie whose bonding direction is perpendicular to the □tracking direction X.
The center 0 of the irradiation spot 18 on the photodetector element ll of 0 is located at the center photoelectric element ltb among the photoelectric elements. Therefore, the focus of the irradiation spot 9 of the light beam 2 on the information medium 8 is controlled by the focusing lens 9 on the information medium 8.
This can be thought of as a gap between the beams, and can therefore be determined by the change in the diameter of the irradiation spot 18 of the reflected beam IO on the photodetector element LL, as shown in FIG. Therefore, in the present invention, the difference output of the amount of light received between the photoelectric element 111) in the center and the photoelectric element 11a arranged on the left side is detected, and the output of the irradiation spot 18 when the irradiation spot 9 is in proper focus with respect to the information medium 8 is detected. Focus control is performed by using the difference output between the photoelectric elements 11a and llb as a reference. Furthermore, an information reproduction signal is obtained from the change in the total amount of light received by the entire photodetector element 11, that is, the photoelectric elements 111L, llb, and 11C.

Therefore, compared to the conventional light shielding plate, a part of the reflected beam 1G is not cut off, and the entire reflected beam 1G is used as the irradiation spot 18 on the photodetector element '11.
Since the light is incident on the information track, the starting and ending ends of the pits 7 forming the information track can be reliably detected, and an accurate information reproduction signal can be obtained.

In the above embodiment, the irradiation spot 9 is
Although the tracking signal cannot be detected, the photodetecting element 11 is, for example, six photoelectric elements 1 connected parallel to the tracking direction through the center of the irradiation spot 18.
4a%14b, 14as 146s 14es 14
f, and a focus control signal is sent to the photoelectric elements 14a and 14.
(Detection is made from the difference signal obtained by subtracting the sum of the amounts of light received by the photoelectric elements 14b and 14e from the sum of the amounts of light received by l, and bit 7
Due to this positional deviation, the positional deviation of the irradiation spot 9 of the light beam 2 with respect to the bit 7 on which the irradiation spot 9 is located
Since the ratio of the reflected portion generated between the irradiation spot 9 and other portions changes compared to when the irradiation spot 9 is located at the proper position, the amount of light of the reflected beam 1o changes, and this is reflected by the photoelectric elements 14a and 1.
From the sum of the amounts of light received by 4b and 14c, photoelectron 14. d and 1
It is detected as the difference in the amount of received light obtained by subtracting the sum of the amounts of received light at 4θ and 14f, and the change in the difference in the amount of received light at the center is used as a tracking signal. The information reproduction signal is transmitted to photoelectric elements 14a and 14b.

It is detected as a change in the total amount of light received by 14c, 14d, 14@, and 14f.

Further, the number of charging elements constituting the photodetecting element may be at least eight so that the bonding direction is orthogonal to the tracking direction, and any number may be within the range of the technical idea stated in the claims. For example, there is no particular meaning in limiting the number of photoelectric elements.

Since the present invention is configured as described above, the focus control signal is obtained from the difference output of the amount of light received by the central photoelectric element and the photoelectric elements placed evenly therebetween, and the information signal is obtained from the sum of the amounts of light received by the photodetecting elements. When detecting the information signal, the detection effect of the non-point control signal does not have an adverse effect, and the information signal and the focus control signal can be accurately and easily detected.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the configuration near the conventional photodetector element, Figure 2 (a), Figure 2 (1)), Figure 8 (a), Figure 8 (b).
is an explanatory diagram of a conventional example that stylistically represents the relationship among pits, irradiation spots, photodetecting elements, etc., Figure 4 is a partially enlarged view of an information medium, and Figure 5 is an explanatory diagram showing an example of an optical system. 6 and 7 are diagrams showing the relationship between the photodetecting element and the irradiation spot of the reflected beam. 21 Light beam, 6. Focusing lens, 8. Information medium, 1
G...Reflected beam, 11...Photodetection element, 111% 1
111% 110% 14a%141), 100% 1
4 (IS1413% 14fe*photoelectric element, X... tracking direction. Patent applicant Mansei Kogyo Co., Ltd. Figure 4 Figure 6 Figure 5

Claims (1)

[Claims] 1. Irradiate the information medium with a light beam through a focusing lens, irradiate the reflected beam from the information medium onto a photodetection element, and connect the photodetection element with at least eight photoelectric elements whose bonding direction is perpendicular to the tracking direction. The center of the irradiation spot diameter of the reflected beam on the photodetecting element is located at the center photoelectric element, and the photoelectric element disposed on one side of the center photoelectric element. A signal detection device in an optical information reading device that controls a gap deviation between the information medium and the focusing lens based on a differential output of the amount of light received by the photodetecting elements, and obtains an information signal from the sum of the amounts of light received by the photodetecting elements.