JPS5928252A - Optical device for optical information - Google Patents

Abstract

PURPOSE:To increase the detecting width and at the same time to improve the detecting accuracy, by providing a pair of reflectors having light transmitting parts between a light source and an optical device to detect both reflected light and transmitted light as well as a focus shift and a tracking shift, respectively. CONSTITUTION:Each of reflectors 12 and 13 has a reflecting part and light transmitting part 22. A projection pattern is circular on a surface rectangular to an optical axis and has a shape equal to the section a luminous flux 10a. When an image forming surface 15 is set at a proper position 15a, detectors 17 and 19 detect no light. However only, the detector 17 detects the light at a position 15b and only the detector 19 does at a position 15c, respectively. Then the light made incident to a detecting surface 30 of detectors 17 and 19 respectively is detected through a photoelectric conversion. The surface 30 is divided into two surfaces 31 and 32 along a center line 33 to detect also a tracking shift. In other words, a tracking shift is detected from the error between detecting signals of surfaces 31 and 32.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an optical device for reading or writing information onto an information carrier such as a video disc, and in particular to tracking position and focal position f? Regarding the original information optical device for obtaining accurate information.

Technical Background and Problems of the Invention Various methods are known for this type of tracking detection or focus detection. According to the most common astigmatism method, increasing the detection accuracy narrows the detection range, and if the detection range is exceeded, a detection error occurs. In this case, a cylindrical lens is used, but when used for this type of detection, the aperture angle becomes large and the range of use is limited. Furthermore, other methods often suffer from the disadvantage of requiring high precision in the components and their assembly.

Purpose and Summary of the Invention The present invention has been made in an attempt to eliminate the drawbacks of the prior art as described above, and provides an optical information optical device that can increase the detection width and improve the detection accuracy with a simple configuration. The purpose is to provide

To achieve this objective, according to the invention, a light source;
an optical device that condenses and images the light from the light source on a predetermined imaging surface, and a detector that detects the light from the imaging surface,
In the optical information optical device, it is determined based on the output of the detector whether or not the optical device focuses on a predetermined position on the image forming plane. At least two pairs of reflecting mirrors each having a light transmitting portion having a shape equal to the cross section of the light beam in the section are provided coaxially, and the reflected light from one of the reflecting mirrors and the transmitted light from the other are detected by the detector, respectively. , one or both of a relative focus shift and a tracking shift of the optical device on the imaging plane are detected.

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

FIG. 1 shows an embodiment of the invention.

According to the figure, a light source 10, an optical lens 11, ring-shaped reflecting mirrors 12 and 13, an optical lens 14, an imaging surface 15, optical lenses 16 and 18, and photodetectors 17 and 19 are shown.

That is, the optical lens 11 is arranged so that the position of the light source 10 becomes a focal point on the front optical axis of the light source 10. Therefore, the light beam transmitted through the lens 11 forms a parallel light beam 1 (la). Ring-shaped reflecting mirrors 12 and 13 are sequentially arranged in this light beam IQ&.

The reflecting mirrors 12 and 13 are as shown in Figure 2), and are formed by forming a reflective portion 21 of aluminum or chromium on a flat glass surface 20 by vapor deposition or the like. This reflective portion 21 is ring-shaped and has a light transmitting portion 22 in the center. The reflecting portion 21 and therefore the light transmitting portion 22 have an oval shape, and when the reflecting mirrors 12 and 13 are tilted at a required angle with respect to the optical axis, the light is projected onto a virtual plane perpendicular to the optical axis. The fi 12 and fi 13 are formed to have a circular shape as shown in FIG. 2(b).

That is, a shadow 211 of the reflective portion 2] and an image 22''ii of the light transmitting portion 22 are obtained on the virtual surface.

An optical lens 16 and a photodetector 17 are placed on the right side of the reflecting mirror 12.
is arranged, and the light reflected by the reflecting mirror 12 is sent to the detector 1.
7 to be detected. An optical lens 18 and a photodetector 19 are arranged on the right side of the reflecting mirror 13, and the detector 19 detects the light that has passed through the reflecting mirror 13. Further, an optical lens 14 is provided on the left side of the reflecting mirror 13.
and an imaging plane 15 are arranged.

These optical devices are arranged so that the image plane 15 is in focus when it is at a proper position 15a. That is, in this state, the parallel light beam 10aij of the light source 10 passes through the transparent part of the reflecting mirror 12, is reflected by the reflecting mirror 13, and maintains the parallel light beam,
The image is focused on an imaging plane 15 via a lens 14.

In addition to the breakage, the reflecting mirrors 12 and 13 are constructed to satisfy the following requirements. That is, the image forming surface 15 is at its proper position 15 & a position 15b slightly closer to the lens 14
When K is present, the light beam from the light source 10 is reflected by the reflecting surface 15 and then slightly spreads to become a light beam 10'b. At this time, this light flux] Obij is sequentially reflected by the reflecting mirrors 13 and 12 and enters the detector 17 via the optical lens 16.

Conversely, when the imaging plane 15 is at a position 150 slightly farther from the lens 14 than its proper position 15a, the light source 10
After being reflected by the reflecting surface 15, the luminous flux from the light beam dries up and becomes a diminished luminous flux 10C. At this time, this luminous flux 100 is reflected by the reflecting mirror 1
3 and passes through the optical lens 18 to the detector 19
incident on the

As is clear from the above, the imaging plane 15 is located at the appropriate position 15a.
, the detectors 17 and 19 do not detect any light, but when the imaging plane 15 comes to position 15b, only the detector 17 detects light, and when the imaging plane 15 comes to position 150, the detector 17 detects no light. Only 19 detects the light.The position tsa of the image forming surface 15, 151), 15c is relative to the optical device, and the absolute position of the image forming surface 15 does not necessarily change. is not an issue.

In this way, the defocus of the optical device can be detected, in which case the detection surfaces of the detectors 17 and 19 are, for example, as shown by the surface 30 in FIG.
The presence or absence of light incident on the sensor is detected by photoelectric conversion. However, as shown in Figure (b), the detection surfaces of the detectors 17 and 19 are divided into two surfaces 31 and 32 with the center line 33 being the diameter.
In this case, tracking deviation can also be detected.

For example, assuming that the image plane 15 is a video disk having bits, the light quantity distribution in each case of tracking is as shown in FIG. That is, assuming that all of the incident light beam is reflected on the image forming surface, the distribution of light intensity 1 centered on optical axis 0 is as shown by curve 40, and for example, from the bit when there is no track deviation on a video disc. The reflection (light information) is as shown by a curve 41, and the light distribution from the imaging plane 15 when there is a track deviation is as shown by a curve 42.
It is shown as follows.

Therefore, the photodetectors 17 and 19 are formed by being divided into two parts as shown in FIG. Keep at °C as shown. By doing so, the two detection surfaces 31 and 32 of the detector are uniformly irradiated when there is no tracking deviation, and when there is tracking deviation, one of the detection surfaces 31 and 32 is strongly irradiated.

In this case, the necessary optical information can be obtained by electrically connecting the photodetectors 17 and 19 as shown in FIG. and D. Here, the detection elements A, B, and C.

The output signal of D is also A, B, 0. If it is expressed as D,
The output A of the detector 17 serves as an input to one of the adders 51 and 54, and the output B serves as an input to one of the adders 51 and 55. Further, the output 0 of the detector 19 becomes an input to one of the adders 52 and 54, and the output 0 becomes an input to one of the adders 52 and 55. The outputs of the adders 51 and 52 are sent to the subtracter 53
The outputs of the adders 54 and 55 are subtracted by the subtracter 56 to become the tracking signal T representing the tracking shift. Therefore, the focus signal f8 is as follows: f8=( A+B)-(0+D), and the I racking signal T3 is Ta-(A+(3)(B+D)).

As can be seen from this, when there is neither focus shift nor tracking shift, fa −= Ts = D. Also, if the defocus is on the front side, f5>0, Ta = 0, and if the defocus is on the rear side, fs < 0, Ts = 0.
becomes.

Further, when there is only a tracking deviation, Ta takes a positive or negative value, and when there is both a focus deviation and a tracking deviation, the signals fa and T.

Both of them take either positive or negative values, and it is possible to extract what kind of focus shift and tracking shift exists with respect to the proper position 15a between the optical device and the imaging plane. By using this signal fg r Ta k and correcting the relative relationship between the optical device and the imaging plane by a known method, it is possible to accurately track the optical device with respect to the imaging plane.

FIG. 6 shows another embodiment of the present invention, in which a half mirror 60 is installed in front of the ring-shaped reflecting mirror 12, and the reflected light is detected by a detector 62 via a lens 61. There is. In this figure, the same reference numerals as in FIG. 1 indicate the same objects.

According to this embodiment, a signal indicating that the object is in focus can be separately extracted by the detector 62.

Effects of the Invention With the above configuration, the area of defocus that can be detected is very large, the signal spread is large, detection errors are small even with simple signal processing, and focus detection and tracking detection are possible. It is possible to provide an optical information optical device that can simultaneously perform

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Figs. 2 and 3 are block diagrams showing main parts of the embodiment of Fig. 1, and Fig. 4 is a light distribution diagram showing the distribution of reflected light in an optical device. The figure on the right, Figure 5 is the first
FIG. 6 is a system diagram of an electric circuit applicable to the embodiment shown in the figure, and is a configuration diagram showing another embodiment of the present invention. 10... Light source, 11, 14, 16, 18...
Optical lens, 12, 13... ring-shaped reflector, 15
...Image plane, 17, 19...Photodetector, 21...
・Reflection part, 22...Transmission or passing part. Applicant's agent Kiyoshi Inomata (11) To Fumi

Claims (1)

[Claims] 1. A light source, an optical device that condenses and images light from the light source on a predetermined image forming surface, and a detector that detects the light from the image forming surface; In the optical information optical device, it is determined based on the output of the detector whether or not the device focuses on a predetermined position on the image forming plane, wherein a section between the light source and the optical device is provided with a section between the light source and the optical device. At least two pairs of reflecting mirrors each having a light transmitting portion having a shape equal to the cross section of the light beam are provided coaxially, and the reflected light from one of the reflecting mirrors and the transmitted light from the other are detected by the detector, respectively. An optical information optical device configured to detect one or both of a relative focal shift and a tracking shift of the optical device on an imaging plane. 2. In the device according to claim 1, the detector is divided into two detection elements, and the optical axis of the reflected light from the image forming surface is on the dividing line when there is no tracking deviation. Optical information optical device consisting of.