JPS61233703A - Lens for linear light source and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a lens which converts a spot light source to linear light by forming the same or a different material with or from a base plate made of a transparent material regularly on the base plate in a striped pattern which differ in synchronism between two X and Y directions. CONSTITUTION:A lens plate 21 is formed by injecting a material 211 which causes variation in the transmissivity of light into a transparent base plate and the pitch of the striped pattern decreases gradually to the outside. When the (x)-directional pitch is made smaller than the (y)-directional pitch, the light from the spot light source on the left-hand side L1 of the lens plate 21 is converged linearly as shown L2 on the right-hand side. The substrate 21 is made of a glass material and the injected material 211 is metallic ions of Ag, etc. The glass base plate which is heated below its fusion point is dipped in fused salt such as silver nitrate to mask the glass base plate except an area where implantation is performed, and an electric field is applied between the base plate and fused salt to implant metallic ions except into the mask. Then, the mask is removed to form a refractive index distribution in the transparent plate.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a lens device that converts a point light source into linear light, and relates to a lens suitable for a linear light source of a FAX or an optical head of an optical disk device. Relating to a manufacturing method.

[Background of the invention]

Conventional structures for obtaining linear light sources include those using straight tube fluorescent lamps and LED arrays as an alternative to this. In addition, recently, line-shaped light sources for FAX machines that form a Fresnel lens array on the output side of an LED array have been sold, which shortens the optical path length.
Efforts are being made to downsize. However, these methods cannot be said to be sufficient in terms of efficiency and cost performance, and the idea of erasing bit information by shaping the intensity distribution of the laser beam of an optical disk device into an elliptical shape and irradiating it onto the recording medium is unique. This method was proposed by 1988-68844 et al., and is attracting attention as a method that allows information to be written while erasing it. However, in the known lens, the means for shaping the illuminance into an ellipse is not necessarily simple, the optical system becomes complicated, and it is not easy to create an arbitrary beam shape.

[Purpose of the invention]

Our goal is to provide the following.

It is in.

[Summary of the invention]

The principle of the present invention will be explained using FIGS. 1 and 2.

In the figure, numeral 21 is a lens plate made by giving a refractive index distribution to a transparent plate to form a periodic striped pattern, and for example, the pitch of the striped pattern becomes gradually smaller on the outside.

Also, if the pitch in the X direction is made denser than in the X direction, the point light source on the left side L1 of the lens plate 21 will be
It condenses light into a line like L2 on the side. The detailed diagram is shown in Figure 1 (
C) In FIG. 1 (C) shown in (D), a substance 211 that changes the transmittance of light is injected into a transparent substrate 21. For example, the substrate 21 is a glass material, and the injected substance 211 is a metal such as Ag. It is an ion. These impurity ions are produced by immersing a glass substrate heated to a temperature below the melting point in a molten salt such as silver chloride, masking the glass substrate except for the region to be implanted, and creating an electric field between the substrate and the molten salt. After this, implant metal ions into parts other than the mask by giving.

By removing the mask, a refractive index distribution can be created in the transparent plate. The pitch of the impurity implanted portions is made to be different in the horizontal and vertical directions, but the regularity of gradually decreasing toward the outside is the same.

That is, by setting the vertical and horizontal dimensions of the rectangular button formed at the center to different values, a linear light condensing function with two focal points can be obtained as shown in FIG. 1(A). In the explanation, we explained the side that forms the refractive index distribution in the glass substrate, but
A lens with a binary m: cross-sectional shape can also be made by coating a plastic film on a transparent substrate and removing a portion of it.

Figure 1 CD) shows an example of this; for example, PHMA
A thin film 212 of (polymethyl methacrylate) is formed on a transparent substrate 21 by a photolithography process, and the regularity of the repeating pitch is the same as the example shown in FIG. 1(C). An example of this process is (1) A few drops of liquid PMMA are placed on the glass substrate 21, and a spinner is used to coat the entire surface to a thickness of about 1 μm. (2) After that, prebaking is performed, and (3) exposure is performed through a separately prepared shadow mask having the required repetition pitch. The black part of the shadow mask does not allow light to pass through, so no change occurs in Pt4MA, but the light that passes through the transparent part of the mask crosslinks the PHMA molecules and strengthens the molecular structure of this part. Therefore.

When the material is immersed in an aromatic organic solvent and developed, only the exposed pattern remains. (4) Furthermore, a binary-shaped micro Fresnel lens with a plastic film can be fabricated by one or more processes of post-baking at a slightly higher temperature to strengthen the remaining parts. The principle of lens action will be explained. This can be understood from the diffraction phenomenon of the Fresnel zone plate shown in FIG. 2(A). The Fresnel zone plate, whose plan view is shown in FIG. 2A, is designed such that the diameter Rn of the nth band is given by the following equation.

RnshindingnLFゞ...(1) where n: natural number λ; wavelength of light F: focal point of the lens In this case, since the striped pattern is concentric, the +1st-order diffracted light is at the right focus of the lens plate 21. The light is focused on F, but in Fig. 1 (
In the case of A), it is sufficient to repeatedly form the twist from the center of the nth line of the rectangular striped pattern at a period that satisfies the relationship of equation (1).Furthermore, the focal length in the X direction and the >F
, linear light elongated in the X direction can be obtained as diffracted light.

However, as shown in Figure 2 (A), it is not possible to focus all the first-order and zero-order light to the focal point by diffraction alone, so the cross-sectional shape of one ring zone is shown in Figure 2 (A). A triangular blaze shape as shown in FIG. 2(B) has higher light collection efficiency than a rectangular shape, so this may be used.

By using this Fresnel lens, a planar microlens with high dimensional accuracy is attached to a lens plate over a light emitting diode (or laser diode) 22 through a space or a transparent material 210 as shown in FIG. 1(B). 21, it is possible to realize a compact linear light source by mounting it on the metal case 25 of the heat sink.

The specific dimensions of the lens shown in FIG. 1(E) are shown below.

(1) From the focal point in the X direction F, = 20m (2) From the focal point in the X direction F, = 4 cabinets (3) Overall dimension 2 wm
2 + m (4) From the center of the nth stripe in the X direction: X, 112.55 (μm) in ijζ7 is the light source length of 660 nm.

(5) Pitch of outermost line in X direction: 0.6 (μm) X direction: 1.3 (μm) (6) Number of lines in X direction = 75 lines, 8377 lines in By adopting the arrangement shown in (E), it is possible to expand the light emitting source within 2 m into a linear light beam with a width of 8 m.

[Embodiments of the invention]

An embodiment of the present invention will be described below.

A schematic configuration when the lens plate of the present invention is applied to a fax machine is shown in FIGS. Figure 4 shows a reading method using a photodiode array 1 with a close-contact structure that minimizes the optical path length.
There is one light source. In both cases, the lens 21 of the present invention is LE.
By simply providing a point light source such as D in front of the person, linear light can be effectively irradiated onto the document 20, and the information written thereon can be read by a photodiode array as the amount of reflected light. The detailed structure and functions are explained next.

In the 5th rM an embodiment of the invention is shown.

In the figure, a transparent substrate 1 is placed facing an R document 20.
0, the main surface of the transparent substrate 1o on the original 20 side is coated with a light-shielding film 6 obtained by vapor-depositing Cr or the like, and a window 6A is formed in a part thereof by, for example, a selective etching method. has been done. A transparent insulating film 5 made of, for example, Sin, formed by CVD or the like is deposited on the light shielding film 6, including the window 6A.

Further, on the upper surface of this transparent insulating film 5, an electrode 8 on which, for example, An, etc. is vapor-deposited is formed, a photodiode 1 is placed on one end of this electrode 8, and the other end is formed by rolling in one direction. has been done. The photodiode 1 is made of a semiconductor material having a PN junction, and is covered with an insulating film (for example, S
in, ). Further, a transparent conductive material made of ITO, for example, is deposited on the light irradiation part of the photodiode 1 to form an electrode 7, and this electrode 7 is formed to extend in the opposite direction to the electrode 8. There is. In this way, the photosensor section consisting of the photodiode 1 and the electrodes 7 and 8 connected thereto is connected to the fifth @(B).
As shown in the plan view, a large number of electrodes 7 and 8 are arranged in parallel in a direction perpendicular to the direction in which they extend. Then, a transparent substrate 31 made of glass or a transparent resin material is formed to cover each photodiode 1 with the other ends (electrode extraction parts) of the electrodes 7 and 8 exposed, and the original 820 A lens 3 is formed on each photodiode 1 on the main surface of the side.

This lens 3 has a focal length that matches the thickness of the transparent substrate 31, and is formed by photolithography used in semiconductor manufacturing processes. That is, for example, a mask is formed using a photoresist film except for only the lens formation region, and Th or As ions are diffused toward the transparent substrate 31 from the affected area of this mask. Then, the Th or Ag ions are transferred to the transparent substrate 3.
Since the material having a refractive index different from the refractive index of 1 is diffused and formed in the concentric pattern explained in FIG. 2, a lens array 3 is constructed corresponding to each sensor 1 as shown in FIG. . There is no light on the back side of the transparent substrate 10! 2 is arranged, and its arrangement is set so that the light from the light source passes through the window 6A of the shielding film 6, irradiates the 1° surface of the document, and irradiates the photodiode 1 through the lens 3. The light irradiated onto the document surface only needs to cover the size of the sensor 1, and it is desirable that the intensity is high.In order to achieve these conditions with as few light sources as possible, the line of the present invention shown in Fig. 1 is used. It is preferable to use shaped light.

In Fig. 5 (O), there is one L at each twice the sensor pitch p.
An example of arranging EDs is illustrated, but if the light emission speed of the LED is high, one light source for every 3 to 5 LEDs is placed in the bifocal lens 211.
, 212, it is possible to irradiate the entire paper width as linear light on principle 20. At this time, it is desirable to consider the position of the LED light source so that the focus is in the window 6A''rsx direction, but it is only necessary to form the shape and dimensions of the light shielding film within the required range. Since the projected light is effectively projected as linear light over the entire width of the reading line of the original 10, the reflected light is focused by the lens 3 onto the upper surface of the corresponding photodiode 1.The output of the photodiode 1 The voltage is output in response to the image written on the original 10, and is transmitted to a signal processing section (not shown).

FIG. 6 shows another embodiment of the image sensor according to the present invention, and shows a structure in which a Fresnel lens array is formed on the back side of a transparent substrate 10. The same reference numerals as in FIG. 3 indicate the same materials. With this structure, the microlens array 3 can be manufactured regardless of the surface on which the photosensor array 1 is provided, so there is no restriction to consider matching in the manufacturing process of the two, and the thickness of the transparent substrate 10 can be adjusted from the focal point of the lens 3. The Fresnel lens 3 can be made according to the
Based on the principle shown in the figure, a transparent optical thin film (approximately 1 μm thick) is coated with an annular pitch on the outer periphery using an electron beam lithography system.
It is manufactured by micromachining to about 1 μm.

The Fresnel axial array may have a planar shape corresponding to the photodiode 1 as shown in FIG. 7 (B), but even if it has a mutually wrapped shape as shown in FIG. 7, it will still have a light condensing effect. has been experimentally confirmed. This method using a planar microlens array is advantageous in terms of optical path length and F-number compared to the rod lens array structure described above in FIG. 1, and has the advantage that a small and bright image sensor can be obtained. In addition, the single-piece structure can be mass-produced using a semiconductor process, which is advantageous in terms of accuracy, variation, and cost.

Moreover, as another method, on the glass substrate 31.

Circular films made of, for example, synthetic resin are sequentially deposited with decreasing diameters by photolithography, and then the deposited synthetic resin bodies are heated and melted.

l The flow may be used to form a semi-convex lens, and the light source 2 can be used in the same way in any of the embodiments.

Since the lens 21 can be constructed on a transparent substrate using a semiconductor microfabrication process, the focal length can be made as small as, for example, 0.1 to 5 m, and the patch between each diode 1 can be made as small as 125 μm.
The optical path length can be reduced to 0.2 to 10μ compared to the conventional 1.
It becomes possible to approach the completely contact type shown in the example, and it is promising as a small light source for FAX.

Next, a case where the present invention is applied to an optical disk lens will be explained.

An optical disk device is an optical system composed of many lenses, and the lenses are mainly composed of glass. In addition, many of the lenses have a lens drive mechanism because it is necessary to automatically adjust the focus.

A typical example of such an optical system is a thin film lens device, which was described in the magazine "Hitachi Hyoron J, August 19g 4th issue, etc.," and the substrate 2 is a thin plate made of a building material such as glass, and the main part is located in the center. At the periphery of the lens 52, two small lenses 59 for track detection and two small lenses 58 for information detection are arranged.These lenses are microfabricated using the same photolithography technique as explained in FIG. For example, the diameter of the main lens 52 is 2 mm, and the diameter of the detection lens 58. A thin plate piezoelectric element 54, 56 is attached on top of it.The light from the laser diode enters from the top to the small lens 58, 59, but the intensity is near the periphery of the Gaussian distribution. Compared to this, the light intensity incident on the main lens 52 is extremely strong and the information bits 91 on the disk 9 are
The spot diameter is narrowed down to the diffraction limit to have sufficient power to write. In addition, an embodiment is shown in FIG. 8(B) for erasing the information bit 91 detected by the detection lens 58. A circular lens 521 mainly takes in light, and another circular lens 58 takes in low-intensity light emitted from the laser, irradiates it onto the disk surface 9, and reads out the read light 910. It generates writing light 920 and erasing light 930. Information bits are irradiated with such a rectangular bea for a required period of time to be erased. Materials that utilize phase transformation generally have a longer erasing time than writing time, so it is necessary to make the light spot follow the information bits on the disk and irradiate it for the required time.

If the lens of the present invention is used for such a recording material, a circular or rectangular beam can be easily produced, and therefore it is suitable for use as a light beam.

FIG. 9 shows a conceptual diagram of frequency characteristics of tracking or focus control for explaining one of the effects of FIG. 8 of the present invention.

In the figure, Fl is the frequency characteristic for conventional optical head control, and FN is the frequency characteristic for the optical head of the present invention.

Since the optical head of the present invention can be made lighter in weight than the conventional one, the strength of the spring for controlling the position of the lens can also be weakened, so that the response range can be expanded. Therefore, predetermined control can be performed at a higher speed than in the past, so that it is possible to increase the speed and improve the S/N in recording on a disk and reproducing signals.

Therefore, according to this embodiment, the optical lens device can be easily constructed.
It can be configured to be small. In addition, the focus and trajectory can be easily adjusted, and higher frequency characteristics can be obtained compared to conventional ones. Furthermore, a multifunctional lens device having writing, erasing, trajectory, and information detection functions can be realized on a single substrate.

Furthermore, according to this embodiment, linear light can be efficiently obtained by providing a small flat lens in front of the point light source.
A bright, compact linear light source can be obtained.

(2) Since an elliptical beam of arbitrary oblateness can be created as a light source for an optical disc, an effective light source for an erasable optical disc head can be created.

〔Effect of the invention〕

As explained above, according to the invention of the present invention, one point light source can be expanded into a linear light source over a wide range.

According to the invention of cylinder 2, the structure is simple and can be downsized.

[Brief explanation of the drawings] Figure 1 is a diagram explaining the principle and structure of the present invention, Figure 2 is a diagram explaining the principle of a Fresnel zone plate (lens), and Figure 3 is an approximate diagram of using the present invention in a FAX light source. Figure 4 is another rough diagram using the present invention as a FAX light source, and Figure 5 is a schematic diagram using the present invention as a FAX light source.
A detailed view of the case where it is used as an AX light source, FIG. 6 shows that the present invention is an FA.
FIG. 7 is a diagram showing another embodiment of the Fresnel lens; FIG. 8 is a diagram showing an example in which the present invention is applied to an optical head lens; FIG. 9 is a detailed diagram of another case using an X light source; It is a characteristic diagram of the lens same as the above. 2...Transparent substrate, 21...Lens.

Claims (1)

[Claims] 1. A linear light source characterized in that a substrate made of a transparent material is regularly formed with different synchronous striped patterns in two directions, X and Y, using the same or different material as the substrate. lens. 2. In invention X-Y described in claim 1,
A lens for a linear light source characterized by a regularly formed striped pattern to create a difference in focus in two directions. 3. A substrate made of a transparent material. Periodic groups (or ridges) formed on the substrate create a striped pattern and light rays from a point light source (or spherical light source) placed on one side of the substrate are directed to the other side. A method for manufacturing a lens for a linear light source, characterized in that the striped pattern is regularly formed so as to convert the light into linear light.