JPH0469825A - Photodetector - Google Patents

Abstract

PURPOSE:To simplify the constitution of a prism by arranging a total reflection film on a semiconductor substrate and totally reflecting light to lead it to an optical sensor. CONSTITUTION:Exit light 7a radiated from the light emission point of a semiconductor laser 5 is reflected by a half mirror 6a and is condensed on a disk 9. Reflected light 7d reflected by the disk 9 is transmitted through the half mirror 6a, and only a semicircular luminous flux of reflected light 7b is not reflected by a total reflection film 14 and is made incident on a photodetector 3a. The other semicircular luminous flux is reflected by the total reflection film 14 and is made incident on a photodetector 3b. The total reflection film 14 divides the luminous flux into halves to lead transmitted light and reflected light to photodetectors 3a and 3b.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical head for optically recording, reproducing and erasing information, such as an optical tisf device.

BACKGROUND OF THE INVENTION In recent years, as optical disk devices have become smaller, faster, and cheaper, they have rapidly become smaller, have simpler configurations, and lower prices of parts.

Fig. 7 shows the Japanese Patent Application Laid-Open No. 64-33 as an optical disk device that realizes miniaturization, simplification of structure, and lower cost of parts.
735 shows a perspective view of the optical head proposed in No. 735.

In FIG. 7, l indicates the optical head device as a whole, and a first photodetector 3 consisting of a light receiving element such as a PIN diode for detecting the reflected light from the TiSF 9 is mounted on a rectangular semiconductor substrate 2 made of silicon or the like. form. The first photodetector 3 consists of two sets of light receiving elements 3a and 3b, each of which is divided into three parts. Furthermore, a second photodetector 4 is formed on the semiconductor substrate 2 to detect the amount of light from the semiconductor laser 5 serving as the light source. A semiconductor laser 5 is fixed to a semiconductor substrate 21 between the first and second photodetectors 3.4 with a solder layer 11. The top of the semiconductor substrate 2 is covered with a protective layer. The prism 6 having a trapezoidal cross section is fixed to the protection N10 on the first photodetecting element 3 with an adhesive or the like. A half mirror 6a formed on the surface of the prism 6 facing the light emitting point of the semiconductor laser 5 is a semi-transparent reflective surface, and the lower surface 6a is a semi-transparent reflective surface.
In b, the portion facing the light-receiving element 3a is a semi-transmissive film, the other portions are a fully-transmissive film, and the upper surface 6C is a total-reflective surface.

In the above-described configuration, the outgoing light 7a emitted from the light emitting point of the semiconductor laser 5 is reflected by the half mirror 6a of the prism 6, and the incident light 7b enters the objective lens 8 and is focused onto the disk 9. The reflected light reflected by the disk 9 passes through the half mirror 6a of the prism 6, enters the light receiving element 3a of the first photodetector 3, and is reflected by the reflected light 7.
The light d is reflected by the prism 6c and is incident on the light receiving element 3b, where the reproduction of the recorded signal, the focus error signal, and the tracking error signal, which are the information on the disk 9, are detected.

The second photodetector 4 receives the rear emitted light 7C emitted from the opposite light emitting point of the semiconductor laser 5, and controls the power of the emitted light 7a of the semiconductor laser 5.

Such a conventional optical head has a detailed configuration shown in FIG. 8, which is a partially enlarged view of the optical head shown in FIG. 7 mentioned above.

A prism 6 is placed on the protection N10 formed on the semiconductor substrate 2.
is fixed with adhesive N12.

On the lower surface 61) of the prism 6 in contact with the protective layer IO, a multilayer light semi-transparent film 13 of about IO to 2ON is formed by vacuum evaporation or the like on a portion corresponding to the light receiving element 3a.

The reflected light 7d that has passed through the half-mirror part 6a of the prism 6 and entered the prism 6 travels straight through the prism 6 and enters the multilayer light semi-transmissive film 13, and approximately half of the amount of the incident light is reflected by the multilayer light. The light passes through the semi-transparent film 13, and then the adhesive p
The light passes through M12 and the protective layer IO and reaches the light receiving element 3a.

The remaining reflected light 7b is reflected inside the prism 6 by the multilayer light transmissive film 13, is further reflected again at the upper surface 6C of the prism 6, and is transmitted through the adhesive ff112 and the protective layer 10 to the light receiving element 3b. reach. That is,
The multilayer light semi-transmissive film 13 divides the amount of reflected light 7d from the disk that is incident on the prism 6 into approximately half of the light receiving element 3a and the light receiving element 3b.

Therefore, the multilayer light semi-transmissive film 13 formed on the lower surface 6C of the prism 6 is located at a position facing the light receiving element 3a, and
It is necessary to form it accurately so that it does not protrude into the adjacent light receiving element 3b1.

Problems to be Solved by the Invention However, in manufacturing the prism 6, a multilayer light semi-transparent film 13 is formed by stacking a large number of several types of thin films by vacuum evaporation. Further, in order to form the multilayer light-year transparent film 13 only at a position facing the light receiving element 3a during vapor deposition, a mask vapor deposition method is used. That is, a metal mask is pressed against the prism 6 so that the vapor is deposited only on the necessary locations. In this mask vapor deposition, the accuracy of the film formation position deteriorates depending on the alignment accuracy between the mask and the prism 6 and the pressing contact state.

The optical head shown in FIG. 7 is small, and accordingly, the prism 6 is also extremely small, and the positional accuracy for forming the multilayer light semi-transparent film 13 is required to be about 20071 m.

As described above, forming an optical head by forming the present multilayer light semi-transmissive film 13 is difficult due to the reduction in yield due to the cost of vapor deposition of the multilayer film, poor positional accuracy of film formation, variation in reflectance and transmittance accuracy, etc. However, it has the disadvantage that it becomes expensive.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the problems of the conventional optical head described above, and an object of the present invention is to provide a photodetector using a total reflection film that can be used in an optical head.

Means for Solving the Problems The present invention as claimed in claim 1 provides an optical sensor provided on a semiconductor substrate to detect light, a total reflection film formed on the semiconductor substrate, and a state covering the total reflection film. a protective film formed on the semiconductor substrate and a prism disposed on the north side of the semiconductor substrate, the total reflection film totally reflects the incident light and passes it through the prism to the optical sensor. This is a photodetector characterized in that it leads to

The present invention according to claim 2 is the invention according to claim I, in which the total reflection film blocks part of the incident light and reflects it toward the prism, and allows the remaining light to pass through as it is, thereby: The photodetector according to claim 1, characterized in that the photodetector guides light to at least two photosensors provided on the semiconductor substrate.

In the present invention, the incident light is totally reflected by the total reflection film and guided to the optical sensor via the prism.

Furthermore, the present invention places such a total reflection film at a position where it can block part of the incident light, thereby reflecting part of the light and allowing the remaining light to pass through as is. . Then, the light is detected by an optical sensor formed at the end where the divided light is guided.

EXAMPLE Below, an example of the present invention will be explained with reference to drawings. Fig. 1 shows an example of an optical head according to the present invention.
A partially enlarged view of FIG. 1 is shown in cross section, and FIG. 3 shows the relationship between the light detecting means and the substrate on the light detecting means.

In the figure, reference numeral 1 denotes an overall light output/isolation device, and a photodetector 3 as an example of an optical sensor detects reflected light from a disk 9 on a rectangular semiconductor substrate 2 made of silicon or the like.
is formed. An example is a PIN diode.

This photodetector 3 consists of a light receiving element 3a and a light receiving element 3b. Note that a protective film such as 5i02 is formed on the light receiving element. As shown in FIG. 2, these light receiving elements 3a and 3b
A total reflection film 14 made of aluminum or the like is formed between them and on the semiconductor substrate 2 with a protective layer IO in between. Total reflection film 1
4 can be formed from aluminum, which is a constituent material of the PIN diode, during manufacture of the PIN diode. Furthermore, since the total reflection film 14 is a single layer deposited, a highly accurate pattern can be easily obtained by etching.

Further, as shown in FIG. 1, a photodetector 4 is formed on the semiconductor substrate 2 as an example of another photosensor for detecting the amount of light from a semiconductor laser 5 serving as a light source. A semiconductor laser 5 is fixed to the semiconductor substrate 2 between these photodetectors 3 and 4 by soldering [11]. As shown in FIG. 2, the top of the semiconductor substrate 2 is protected by N
covered by 10. The prism 6 having a trapezoidal cross section is fixed to the protection N10 on the photodetecting element 3 with adhesive or the like.

The half mirror 6a, which is the surface of the prism 6 facing the light emitting point of the semiconductor laser 50, is a semi-transparent reflective surface, and the lower surface 6b is made of a glass material that is completely transparent, and does not require any film formation. . The upper surface 6C is a total reflection surface.

In the above-described configuration, the outgoing light 7a emitted from the light emitting point of the semiconductor laser 5 is reflected by the half mirror 6a of the prism 6, and the incident light 7b enters the objective lens 8 and is focused onto the disk 9. Reflected light 7d reflected by the disk 9
passes through the half mirror 6a of the prism 6, and
The light is emitted from the lower surface 6b and passes through the adhesive 12 and the protective layer 10.

Further, only the approximately semicircular half of the reflected light 7b is not reflected by the total reflection film 14 and is incident on the light receiving element 1-3a. On the other hand, the remaining semicircular cane beam of the reflected light 7d is reflected by the total reflection film 14, further reflected by the prism 6C, and is reflected by the light receiving element 3.
incident on b. FIG. 3 is a plan view showing the situation.

That is, the tree total reflection film 14 spatially divides the luminous flux into approximately half, thereby approximately halving the amount of light and guiding the transmitted light and reflected light to the respective light receiving elements 3a and 3b. To detect the information on the disc 9, for example, if it is a CD, to reproduce the signal, use the photodetector 3.
The focus error signal is detected as shown in FIG. 3, and the signal shown in FIG. 4 is obtained. The tracking error signal is detected by the far field method using the light receiving element 3a or
It is obtained by differential operation of cells on both sides of 3b. 100 is a differential amplifier. Note that the photodetector 4 receives the rear emitted light 7d emitted from the light emitting point on the opposite side of the semiconductor laser 5, and controls the power of the emitted light 7a of the semiconductor laser 5.

Next, another embodiment will be described.

FIG. 5 shows a perspective view of an optical head according to a second embodiment of the present invention.

In this embodiment, for the optical head shown in FIG. 1 of the present invention,
The arrangement of the total reflection film is changed, so that even if a positional shift occurs between the spot and the photodetector in the traveling direction of the reflected light 7d (in the direction of arrow 15), there will be no detection error.

That is, the reflected light 7d reflected by the disk 9 is transmitted through the half mirror 6a of the prism 6, and is transmitted through the lower surface 6 of the prism 6.
The light is emitted from b and passes through the adhesive 12 and the protective layer 10.

The total reflection film 14 is arranged so as to cut half of the light spot in the direction of the arrow 15. Therefore, half of the light passes through and enters the light receiving element 3a, and the remaining half of the light is reflected by the total reflection film 14 and enters the light receiving element 3b. FIG. 6 shows the positional relationship between the photodetector 3 and the light spot.

Other configurations and operations are similar to the embodiment shown in FIG. 1.2. Detection of disc information is the same as described above, but focus position detection is performed by the configuration shown in FIG. 6.

In the above embodiments, only the case where the light beam is split by the total reflection film on the semiconductor substrate and guided to the photodetector is described. Alternative configurations of photodetectors are also encompassed by the present invention.

Note that the photodetector according to the present invention is applicable not only to optical heads but also to other products.

Effects of the Invention As is clear from the above description, according to the present invention as claimed in claim 1, a total reflection film is disposed on the semiconductor substrate E, and the total reflection is guided to the optical sensor. The configuration can be simplified and manufacturing can be facilitated. Therefore, by using this photodetector, an inexpensive optical head can be provided.

Furthermore, according to the present invention as claimed in claim 20, there is no reduction in yield due to the vapor deposition cost of multilayer semi-reflective films, poor positional accuracy of film formation, variations in reflectance/transmittance accuracy, etc., as in the prior art. We can provide photodetectors. Therefore, by using this photodetector, an inexpensive optical head can be provided.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an optical head according to a first embodiment of the present invention, FIG. 2 is an enlarged sectional view of the same portion, and FIG. 3 is a schematic diagram showing the relationship between a photodetector and a spot in the first embodiment. FIG. 4 is a graph showing the characteristics of the focus error signal of the first embodiment, and FIG.
The figure is a perspective view of an optical head according to a second embodiment of the present invention, FIG. 6 is a schematic plan view showing the relationship between a photodetector and a spot in the second embodiment, and FIG. 7 is a diagram of a conventional optical head. The perspective view and FIG. 8 are enlarged cross-sectional views of the same portion. 2... Semiconductor substrate, 3.4... Photodetector, 3a, 3
b... Optical sensor, 5... Semiconductor laser, 6... Prism, 8... Objective lens, 14... Total reflection film.

Claims (1)

[Claims] (1) An optical sensor provided on a semiconductor substrate to detect light, a total reflection film formed on the semiconductor substrate, and a protective film formed on the semiconductor substrate in a state covering the total reflection film. , a prism disposed on the semiconductor substrate, and the total reflection film totally reflects the incident light and guides it to the optical sensor via the prism. vessel. (2) The total reflection film blocks part of the incident light and reflects it toward the prism,
2. The photodetector according to claim 1, wherein the remaining light is allowed to pass through, thereby guiding the light to at least two photosensors provided on the semiconductor substrate.