JP2008298874A - Reflection prism, optical pickup, and method for manufacturing reflection prism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve the suppression of aberration generated by a reflection film of a reflection prism having an incident face, a reflection film face and an emission face. <P>SOLUTION: The reflection prism has the incident face 2 on which light is incident, the reflection film face 4 in which a reflection film R is formed, and the emission face 3 being a face in which light incident from the incident face 2 is reflected toward the reflection film face 4 and light reflected on the reflection film face 4 is emitted. The emission face 3 and the reflection film face 4 are optical planes, and the inclination of a recess or a projection of the emission face 3 is in a reverse direction to the inclination of a recess or a projection of the reflection film face 4. Thereby the aberration generated on the reflection film face 4 can be suppressed by the action of film stress of the reflection film R. In addition, the suppression of the aberration can be achieved further by making the incident face 2 and the emission face 3 the optical face having the same recess or projection inclination. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a reflecting prism for changing an optical path, an optical pickup using the reflecting prism, and a reflecting prism manufacturing method for manufacturing the reflecting prism.

  Optical systems such as optical pickups and liquid crystal projectors are composed of various optical components, and one of the components is a reflecting prism for changing the optical path. In general, a triangular prism having a right-angled isosceles triangle is used as the reflecting prism, and the inclined surface of the triangular prism is used as a reflecting surface. Many of the reflective surfaces are formed with a reflective film, and reflect light incident on the reflective film.

  At this time, since the reflecting film exerts a film stress that warps concavely or convexly with respect to the surface of the prism, astigmatism and power (the focal point shifts and the spot image deteriorates in the light reflected by the reflecting surface. Aberrations). Astigmatism and power (these aberrations are hereinafter simply referred to as aberrations) are caused by the flatness of the surface. Although the reflective film varies depending on the type of film, it has an internal stress, and the internal stress affects the flatness of the reflective film surface. Therefore, aberrations are inevitably generated on the reflective film surface.

  In particular, due to the recent demand for compact optical systems, thinner reflective prisms have been required. As a thin reflective prism, the incident surface on which light is incident, the reflective film surface on which the reflective film is formed, the light incident from the incident surface is reflected toward the reflective film surface, and the light reflected by the reflective film surface is reflected. There is a reflecting prism configured to have an exit surface that emits light. In this reflecting prism, the angle formed between the incident surface and the reflecting film surface is an obtuse angle, and the angle formed between the reflecting film surface and the emitting surface and the angle formed between the incident surface and the emitting surface are acute angles. Since the angle formed between the reflecting film surface and the emitting surface is an obtuse angle, the reflecting prism as a whole can be made thin. Accordingly, even in this thin reflecting prism, since the reflecting film surface is formed, aberration is generated in the light reflected by the reflecting film surface due to the film stress of the reflecting film.

Patent Document 1 discloses an optical multilayer filter that improves the influence of film stress caused by a reflective film. Patent Document 1 discloses that a warp caused by a film stress of a dielectric multilayer film formed on a glass substrate is returned to the warp by forming a dielectric single layer film on the opposite surface of the dielectric multilayer film of the glass substrate. ing.
JP-A-2005-43755

  The optical multilayer filter of Patent Document 1 uses a dielectric single layer film in order to correct deformation due to film stress generated on a flat substrate. This dielectric single-layer film is used to correct the deformation of the substrate, and is essentially an unnecessary film in order to exhibit the function of the optical element. For example, when a dielectric single layer film for correcting deformation of the substrate is formed on the exit surface (or incident surface) which is a surface other than the reflective surface of the reflective prism, the dielectric single layer film is reflected by the reflective prism. It is essentially not necessary for the function. At this time, light is transmitted through the dielectric single-layer film. However, light is transmitted through the dielectric single-layer film, thereby affecting light. As one of the effects, as described in Patent Document 1, when light passes through the dielectric single layer film, ripples occur in the transmittance, and it becomes impossible to obtain good optical characteristics. There is. In Patent Document 1, the ripple is kept in a very small range, but by forming an unnecessary film to essentially exhibit the function of the optical element, some effect is exerted on the light, resulting in optical It affects the characteristics.

  In addition, when a dielectric single layer film for correcting the shape is formed, there is a problem that an essentially unnecessary film is required and the cost increases accordingly.

  Therefore, an object of the present invention is to suppress aberrations caused by the reflection film of the reflection prism without using a film.

  In order to solve the above problems, a reflecting prism according to claim 1 of the present invention includes an incident surface on which light is incident, a reflecting film surface on which a reflecting film is formed, and light incident from the incident surface. A reflecting prism having an exit surface that is a surface that reflects toward the surface and emits light reflected by the reflective film surface, wherein the exit surface and the reflective film surface are optical planes, The concave or convex tendency of the exit surface is set in a direction opposite to the concave or convex tendency of the reflective film surface.

  The reflection film surface is an optical flat surface having a tendency of being concave or convex mainly due to the influence of the film stress of the reflection film, and aberration is generated in the light reflected by the reflection film surface. Therefore, aberration can be suppressed by making the exit surface an optical flat surface having a tendency of unevenness in the opposite direction to the tendency of the reflection film surface to be concave or convex. In other words, aberration can be suppressed without using a film for correcting the shape of the substrate by making the exit surface an optical flat surface having a tendency of being concave or convex. The optical plane is not an ideal plane (ideal plane having a flatness of 0), but is a plane having a tendency of being slightly concave or convex. In addition, the aberration here refers to astigmatism, power, and the like, and does not include spherical aberration.

  When one surface of the transparent member is polished, it cannot be an ideal plane, and even if the polishing accuracy is increased, it tends to be slightly concave or convex. Therefore, by actively utilizing the tendency of the micro unevenness, an emission surface that forms an optical plane having a tendency in the opposite direction of the film stress of the reflective film is formed. In order to form an optical plane, plane polishing such as polishing or lapping can be applied. For example, an optical plane can be formed by polishing the surface of the transparent member using a polishing jig such as a lap. And in order to control the unevenness | corrugation of an optical plane actively, an unevenness | corrugation is given to a wrap. In order to form an optical plane having a concave tendency, a convex one is used for the wrap, and in order to form an optical plane having a convex tendency, a concave one is used. Thereby, the tendency of the unevenness of the optical plane can be positively controlled.

  The reflecting prism according to claim 2 of the present invention is characterized in that, in the reflecting prism according to claim 1, the entrance surface is an optical plane having the same concave or convex tendency as the exit surface.

  Aberration caused by the film stress of the reflective film can be suppressed by making the exit surface an optical plane having a concave or convex tendency, but the incident surface has the same concave or convex tendency as the exit surface. By setting the target plane, aberration can be further suppressed.

  A reflecting prism according to a third aspect of the present invention is the reflecting prism according to the first aspect, characterized in that an angle formed by the reflecting film surface and the incident surface is an obtuse angle.

  Increasing the angle formed between the reflecting film surface and the incident surface can reduce the thickness of the reflecting prism, thereby satisfying the demand for downsizing the entire optical system. Therefore, the reflecting prism can be made thinner by making the angle between the reflecting film surface and the incident surface an obtuse angle.

  An optical pickup according to a fourth aspect of the present invention has the reflecting prism according to any one of the first to third aspects. In addition to the optical pickup, the above-described reflecting prism can be applied to a projection display device such as a liquid crystal projector and an imaging device such as a digital camera.

  According to a fifth aspect of the present invention, there is provided a reflecting prism manufacturing method, wherein an incident surface on which light is incident, a reflecting film surface on which a reflecting film is formed, and light incident from the incident surface is reflected toward the reflecting film surface. And a reflecting prism having a light emitting surface that emits light reflected by the reflecting film surface, wherein the reflecting film is formed on one surface of the transparent member, and has a tendency to be concave or convex. After forming the reflective film surface to be an optical flat surface, when the reflective film surface is an optical flat surface having a concave tendency, an output surface to be an optical flat surface having a convex tendency is formed. When the reflective film surface is an optical flat surface having a convex tendency, an output surface is formed so as to be an optical flat surface having a concave tendency.

  Since a large aberration occurs on the reflecting film surface due to the film stress of the reflecting film, the reflecting film surface is first formed, and then the optical surface has a tendency to have a concave or convex exit surface corresponding to the film stress on the reflecting film surface. By using a plane, aberration can be efficiently suppressed. At this time, the emission surface is formed on an optical plane having a tendency of being concave or convex in the direction opposite to the film stress of the reflective film.

  The reflecting prism manufacturing method according to claim 6 of the present invention is the reflecting prism manufacturing method according to claim 5, wherein an incident surface is formed so as to be an optical flat surface having the same concave or convex tendency as the exit surface. It is characterized by that.

  As described above, it is possible to manufacture a reflecting prism that further suppresses aberration by making the incident surface an optical flat surface having the same concave or convex tendency as the output surface.

  According to a seventh aspect of the present invention, there is provided a reflecting prism manufacturing method, wherein an incident surface on which light is incident, a reflecting film surface on which a reflecting film is formed, and light incident from the incident surface is reflected toward the reflecting film surface. And a reflecting prism for manufacturing a triangular prism-shaped reflecting prism having an obtuse angle between the incident surface and the reflecting film surface, and an emitting surface that emits light reflected by the reflecting film surface. A manufacturing method comprising: forming a reflective film having a film stress acting in a concave or convex direction on one surface of a flat transparent member; and a transparent member on which the reflective film is formed. A cutting process for generating a strip member by cutting into a strip shape, and polishing the strip member cut in the cutting process so that the angle formed between the polished surface and the reflective film surface becomes an acute angle. A first polishing step for performing polishing, and a short time after the first polishing step. A second polishing step for polishing the member, and polishing so that an angle formed between the polished surface and the reflective film surface is an obtuse angle, and in the first polishing step, Polishing is performed so that the polished surface becomes an optical flat surface having a tendency of concave or convex in the direction opposite to the film stress of the reflective film.

  As a specific manufacturing method for manufacturing the reflecting prism, for example, a manufacturing method as in claim 7 can be applied. The manufacturing method of claim 7 is a method for manufacturing a large number of reflecting prisms at a time, and a plurality of reflecting prisms are manufactured from a flat transparent member. At this time, the reflection film is formed on the transparent member constituting the plurality of reflection prisms in the reflection film formation step. The reflective prism of the present invention can be manufactured even if a reflective film is individually formed on the reflective prism. In this case, a plurality of reflecting prisms are arranged inside the vapor deposition apparatus for forming the reflective film to deposit the vapor deposition material. At this time, the reflective film may adhere not only to the reflective film surface but also to a part of the incident surface and the outgoing surface. In the present invention, since the reflective film is formed on the transparent member constituting the plurality of reflective prisms, the above-described problem does not occur.

  The reflecting prism manufacturing method according to an eighth aspect of the present invention is the reflecting prism manufacturing method according to the seventh aspect, wherein in the second polishing step, the polished surface is a concave or concave portion in the first polishing step. It is characterized by polishing so as to be an optical plane having the same tendency as the convex tendency.

  As described above, it is preferable that the incident surface is an optical plane having the same concave or convex tendency as the output surface. Therefore, in the second polishing step, polishing is performed so that the optical surface has the same concave or convex tendency as in the first polishing step.

  In the above-described reflecting prism, when light is reflected, the phase difference is changed even if it is reflected once, and further, since the reflection is performed twice, an unacceptable change in phase difference occurs. Therefore, a phase adjusting member can be formed on the exit surface. As the retardation adjusting member, for example, a retardation film or a birefringent member having a predetermined thickness can be applied. By forming the phase difference adjusting member, even if a change occurs in the phase difference when the light is emitted from the reflecting prism, the phase difference can be adjusted. When a retardation film is used as the retardation adjustment member, it is preferable to use a film having a small film stress.

  In the present invention, the exit surface of a thin reflective prism having an entrance surface, an exit surface, and a reflective film surface is formed without using a film for suppressing aberrations. By using an optical plane having a convex tendency, it is possible to suppress aberrations that occur on the reflective film surface.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Although not shown, for example, in the case of an optical pickup, an objective lens is disposed after the reflecting prism 1 (on the optical path of light emitted from the reflecting prism 1). When aberration occurs in the reflecting prism 1, the objective lens is out of focus or blurred, causing a problem such as deterioration of the spot image. Hereinafter, suppression of aberration generated in the reflecting prism 1 will be described.

  As shown in FIG. 1, the reflecting prism 1 of the present invention has an entrance surface 2, an exit surface 3, and a reflective film surface 4. A reflective film R is formed on the reflective film surface 4. As the reflective film R, for example, a dielectric multilayer film using titanium oxide or a dielectric multilayer film using tantalum oxide can be applied. The angle formed between the incident surface 2 and the reflecting film surface 4 is an obtuse angle, and the angle formed between the incident surface 2 and the emitting surface 3 and the angle formed between the emitting surface 3 and the reflecting film surface 4 are acute angles. Yes.

  The incident surface 2 is a surface on which light is incident. Further, the incident surface 2 is inclined with respect to the light traveling direction. Therefore, the light incident from the incident surface 2 is refracted and travels toward the exit surface 3.

  The exit surface 3 is a surface that reflects the light incident from the entrance surface 2 and emits the light reflected by the reflective film surface 4. The light incident from the incident surface 2 is reflected at the exit surface 3 for the first time. No reflection film is formed on the exit surface 3, and the light is reflected by the incident angle of light and the refractive index difference (the refractive index difference between the refractive index of the reflecting prism 1 and the refractive index of air). . When the reflecting prism 1 is applied to the optical pickup, the optical path needs to be changed by 90 degrees in the reflecting prism 1, and as shown in FIG. It is orthogonal to the optical path when exiting from the surface 3.

  The reflection film surface 4 is a surface that further reflects the light reflected on the output surface 3 for the first time by the second time. On the reflection film surface 4, the light is reflected toward the emission surface 3 by the action of the reflection film R.

  The entrance surface 2, the exit surface 3 and the reflection film surface 4 are all optically flat. The reflection film surface 4 is a surface on which the reflection film R is formed, but cannot be an ideal plane, and is an optical plane that tends to be concave or convex mainly due to the film stress of the reflection film R. Become. Since the reflective film surface 4 is an optical flat surface having a tendency of being concave or convex, aberration occurs in the light reflected by the reflective film surface 4. Therefore, the aberration can be suppressed by making the exit surface 3 an optical plane having a tendency opposite to the unevenness of the reflective film surface 4.

  Here, in order to make the emission surface 3 an optical flat surface having an unevenness, the surface of the emission surface 3 is polished. When performing this planar polishing, the exit surface 3 is polished in accordance with the tendency of the unevenness of the reflective film surface 4. For example, when a dielectric multilayer film using titanium oxide is applied to the reflective film R, the film stress acts concavely, so the reflective film surface 4 becomes an optical plane having a concave tendency. In this case, planar polishing is performed so that the emission surface 3 becomes an optical plane having a convex tendency. On the other hand, when a film containing tantalum oxide as a main component is used as the reflective film R, the film stress acts convexly, so that the reflective film surface 4 becomes an optical plane having a convex tendency. In this case, planar polishing is performed so that the emission surface 3 becomes an optical plane having a concave tendency.

  Basically, if the optical plane of the exit surface 3 has a concave or convex tendency as described above, the light aberration can be improved. However, the entrance surface 2 has the same concave or convex shape as the exit surface 3. By using an optical plane having a tendency, the aberration can be further improved.

  Further, as shown in FIG. 1, a retardation film 6 as a phase difference adjusting member is formed on the emission surface 3. Since the light emitted from the emission surface 3 has a phase difference, a phase difference film 6 is formed on the emission surface 3 in order to correct this phase difference. The retardation film 6 is formed as an antireflection film having a retardation function. Thereby, the shift | offset | difference of a phase difference can be eliminated. Note that the use of a material having a small film stress for the retardation film 6 can avoid the influence of aberration caused by the influence of this film.

  Next, a manufacturing method of the reflecting prism 1 will be described based on the flowchart of FIG. As shown in FIG. 3, a reflective film R is formed on one surface 10R of the flat transparent member 10 (step S1: film forming process). In order to form the reflective film R, the transparent member 10 is disposed on the upper part of the vapor deposition apparatus (not shown), the vapor deposition material is evaporated from the vapor deposition source 20 disposed on the lower part, and the reflective film R is formed on one surface 10R of the transparent member 10. Is deposited. Here, a dielectric multilayer film using titanium oxide as the material of the reflective film R is applied. For this reason, the film stress of the reflective film R acts in the concave direction, and the concave stress acts on the one surface 10 </ b> R of the transparent member 10.

  Next, the transparent member 10 on which the reflective film R is formed is cut into strips along the cutting plane indicated by broken lines in the drawing to obtain a plurality of strip members 11 shown in FIG. S2: Cutting step). In this cutting step, the transparent member 10 is cut so that the cross section of the strip member 11 is rectangular. At this time, the reflecting film forming surface 11R of the strip member 11 becomes an optical plane having a concave tendency due to the action of the film stress.

  As shown in FIG. 4B, the first fixing jig 23 is disposed on the fixing plane 22, and the strip member 11 is attached to the first fixing jig 23 with an adhesive or the like. The first fixing jig 23 is provided with a first inclined surface 23S, and the angle formed between the first inclined surface 23S and the horizontal direction is an acute angle. When the strip member 11 is fixed to the first fixing jig 23, the reflecting film forming surface 11R and the first inclined surface 23S are fixed. In this state, the strip member 11 is planarly polished using a concave polishing jig (a polishing jig such as a wrap having a concave surface to obtain an optical flat surface having a slight convexity) (step). S3: First polishing step). In the polishing in the first polishing step, polishing is performed up to the position of the one-dot chain line in the drawing, and polishing is performed so that the first polished surface 11A and the reflective film forming surface 11R that have been polished are at an acute angle. . At this time, since the flat polishing is performed using the concave polishing jig 24, the first polishing surface 11A is an optical flat surface having a convex tendency. That is, the first polished surface 11A has a convex tendency opposite to the concave direction of the film stress on which the reflective film R acts.

  Next, as shown in FIG. 5A, the second fixing jig 26 is disposed on the fixing plane 22, and the strip member 11 that has undergone the first polishing step is fixed to the second fixing jig 26. . The second fixing jig 26 is provided with a second inclined surface 26S, and the angle formed between the second inclined surface 26S and the horizontal direction is an acute angle. When the strip member 11 is fixed to the second fixing jig 26, the first polishing surface 11A is fixed to the second inclined surface 26S. In this state, the strip member 11 is planarly polished using the concave polishing jig 24 (step S4: second polishing step). In the polishing in the second polishing step, the polishing is performed up to the position of the one-dot chain line in the drawing, and the polishing is performed so that the second polished surface 11B and the reflective film forming surface 11R that have been polished have an obtuse angle. . At this time, since the planar polishing is performed using the concave polishing jig 24, the second polishing surface 11B is an optical plane having a convex tendency. That is, the second polished surface 11B has a convex tendency opposite to the concave direction of the film stress on which the reflective film R acts.

  And what was obtained through the 2nd grinding | polishing process becomes the strip member 11 as shown in FIG.5 (b). The strip member 11 after the second polishing step finally becomes the reflecting prism 1. Among the strip members 11, the reflecting film forming surface 11 </ b> R constitutes the reflecting film surface 4, the first polishing surface 11 </ b> A constitutes the emission surface 3, and the second polishing surface 11 </ b> B constitutes the incident surface 2. In addition, since the strip member 11 of FIG.5 (b) is an elongate member, this may be cut | disconnected and you may make it obtain the some compact reflective prism 1. FIG.

It is a figure explaining a reflective prism. It is a flowchart explaining the flow of the manufacturing method of a reflecting prism. It is a figure explaining the film-forming process among the manufacturing methods of a reflecting prism. It is a figure explaining a cutting process and the 1st grinding | polishing process among the manufacturing methods of a reflective prism. It is a figure explaining the 2nd grinding | polishing process and the reflective prism finally obtained among the manufacturing methods of a reflective prism.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reflection prism 2 Incident surface 3 Outgoing surface 4 Reflective film surface 6 Retardation film

Claims (8)

An incident surface on which light is incident; a reflective film surface on which a reflective film is formed; and a surface that reflects light incident from the incident surface toward the reflective film surface and emits light reflected by the reflective film surface A reflecting prism having an exit surface,
The exit surface and the reflective film surface are optical planes,
A reflecting prism having a concave or convex tendency on the exit surface in a direction opposite to the concave or convex tendency on the reflecting film surface.   The reflecting prism according to claim 1, wherein the incident surface is an optical flat surface having the same concave or convex tendency as the output surface.   2. The reflecting prism according to claim 1, wherein an angle formed between the reflecting film surface and the incident surface is an obtuse angle.   An optical pickup having the reflecting prism according to any one of claims 1 to 3. An incident surface on which light is incident; a reflective film surface on which a reflective film is formed; and a surface that reflects light incident from the incident surface toward the reflective film surface and emits light reflected by the reflective film surface A method of manufacturing a reflecting prism having a certain exit surface,
After forming the reflective film on one surface of the transparent member and forming the reflective film surface to be an optical plane having a tendency of being concave or convex,
When the reflective film surface is an optical plane with a tendency to be concave, an output surface is formed to be an optical plane with a tendency to be convex, and when the reflective film surface is an optical plane with a tendency to be convex, A method of manufacturing a reflecting prism, comprising forming an exit surface that is an optical flat surface having a concave tendency.   6. The method of manufacturing a reflecting prism according to claim 5, wherein an incident surface is formed so as to be an optical flat surface having the same concave or convex tendency as the output surface. An incident surface on which light is incident; a reflective film surface on which a reflective film is formed; and a surface that reflects light incident from the incident surface toward the reflective film surface and emits light reflected by the reflective film surface A reflecting prism manufacturing method for manufacturing a triangular prism-shaped reflecting prism having an obtuse angle with the incident surface and the reflecting film surface,
A film forming step of forming the reflective film having a film stress acting in a concave or convex direction on one surface of a flat transparent member;
A cutting step of generating a strip member by cutting the transparent member on which the reflective film is formed into a strip shape;
A first polishing step of polishing the strip member cut in the cutting step, and polishing so that an angle formed between the polished surface and the reflective film surface is an acute angle;
A second polishing step of polishing the strip member that has undergone the first polishing step, and polishing so that the angle formed between the polished surface and the reflective film surface is an obtuse angle; ,
In the first polishing step, the polished surface is polished so as to be an optical plane having a tendency of being concave or convex in the direction opposite to the film stress of the reflective film. A method of manufacturing a reflecting prism.   In the second polishing step, the polished surface is polished so as to be an optical plane having the same tendency as the concave or convex tendency of the first polishing step. The manufacturing method of the reflecting prism of description.

Images