JP2007328191A - Optical element and optical device - Google Patents

Abstract

An optical element capable of reducing molding time and manufacturing cost is provided.
A prism has a first surface, a second surface, and a reflecting surface. The wavefront aberration value y of the reflecting surface 13 is in a relationship of x / y> 2 with respect to the wavefront aberration value x of the smaller wavefront aberration value of the first surface 11 and the second surface 12, and x Is 0 <x ≦ λ / 4, and y is 0 <y ≦ λ / 10 (λ is the wavelength of light emitted from the He—Ne laser).
[Selection] Figure 2

Description

  The present invention relates to an optical element and an optical device. In particular, the present invention relates to an optical element having an entrance surface, an exit surface, and a reflection surface, and relates to an optical device including the optical element.

  In recent years, optical elements having a high refractive index have been demanded as optical elements such as lenses and prisms mounted on various optical devices (for example, DSC, DVC, mobile phone cameras, projection TVs).

  Conventionally, the optical element is molded using a polishing method, an injection molding method, a press molding method, or the like. The polishing method is a method of molding an optical element by polishing a glass optical element material. The injection molding method is a method in which an optical resin is injected into a molding die to mold an optical element. In the press molding method, first, an optical element material is supplied into a mold, and then the optical element material is heated and heated, and then the heated and heated optical element material is pressurized using a pressing mold. Then, the optical element is molded, and then the molded optical element is cooled.

  When the polishing method is compared with the press molding method, it is difficult to mold an optical element having a curved optical functional surface because the optical element is molded by polishing the optical element material. In the molding method, an optical element having a complicated shape such as an aspheric lens can be molded by devising the shape of the mold. Also, comparing the injection method with the press molding method, the injection molding method does not mold glass optical elements because it molds optical elements by injecting optical resin into a molding die, but press molding. In the method, a glass optical element can be formed by using a glass optical element material. Therefore, if the press molding method is used, it is possible to mold an optical element that is rich in variations in shape and excellent in heat shrinkability and brightness as compared with the case where a polishing method or an injection molding method is used.

  However, as described above, the press molding method involves a cooling process for cooling the molded optical element, so that heat shrinkage occurs in the entire optical element similar to the outer shape of the optical element, and sink marks are partially generated in the optical element. Will occur. For this reason, when molding an optical element made of a curved surface such as a lens by using a press molding method, the optical element is molded by using a pressing die corrected in accordance with the following method.

  The method of correcting the stamping die is to first mold an optical element using a stamping die that has been machined according to the design value, and then to form errors that occur between the desired optical element and the molded optical element. In other words, a correction process is performed to obtain (that corresponds to the contraction amount of the molded optical element), and to correct the shape of the error to the pressing die.

  On the other hand, when molding an optical element consisting of a plurality of optical function planes using the press molding method, if the occurrence of sink marks can be prevented, the optical function surface is flat even if thermal shrinkage occurs, so There is no need for correction processing. However, in the case of an optical element having a large thickness difference such as a prism, it is difficult to mold the optical element while suppressing the occurrence of sink marks. Therefore, it is necessary to correct the pressing surface of the pressing die from a flat surface to a non-planar surface according to sink marks. Since the correction processing of the pressing mold requires a high level of technology, the manufacturing yield of the optical element is often deteriorated, and methods for correcting the pressing mold more simply have been studied.

For example, Patent Document 1 discloses that the correction process of the pressing die can be simplified by devising the cooling process in the press molding method. The press molding method disclosed in this document cools the upper mold and the lower mold with different cooling gradients. As a result, sink marks are generated only on one surface of the optical element. Therefore, only one surface of the pressing die needs to be corrected and the correction processing of the pressing die can be simplified.
JP 7-69651 A

  However, even if the optical element is molded using the method disclosed in Patent Document 1, it is necessary to perform correction processing of the pressing die, and the number of molding steps of the optical element increases. As a result, it is difficult to reduce the molding time of the optical element and reduce the manufacturing cost of the optical element.

  The present invention has been made in view of this point, and an object of the present invention is to provide an optical element capable of reducing the molding time and the manufacturing cost. Moreover, it is providing the optical apparatus provided with such an optical element.

  The optical element of the present invention includes an entrance surface, an exit surface, and a reflection surface, and is formed such that light incident substantially perpendicular to the entrance surface is reflected by the reflection surface and emitted from the exit surface. The wavefront aberration value y of the reflecting surface has a relationship of x / y> 2 with respect to the smaller wavefront aberration value x of the wavefront aberration value of the incident surface and the wavefront aberration value of the exit surface, and the incident surface The smaller wavefront aberration value x of the wavefront aberration value and the wavefront aberration value of the exit surface is 0 <x ≦ λ / 4, and the wavefront aberration value y of the reflection surface is 0 <y ≦ λ / 10. Yes (λ is the wavelength of light emitted from the He—Ne laser).

  In such a configuration, the wavefront aberration value of the reflecting surface is λ / 10 or less. Therefore, the optical element has an optical performance that is excellent enough to be mounted on an optical device.

  In addition, the wavefront aberration value of the entrance surface and the wavefront aberration value of the exit surface are larger than the wavefront aberration value of the reflection surface. Therefore, the optical element can be formed without performing correction for making the wavefront aberration values of the entrance surface, the exit surface, and the reflection surface substantially the same.

  The optical device of the present invention includes an entrance surface, an exit surface, and a reflection surface, and is formed so that light incident substantially perpendicular to the entrance surface is reflected by the reflection surface and emitted from the exit surface. The optical element is disposed on the optical path. In this optical element, the wavefront aberration value y of the reflecting surface is in a relationship of x / y> 2 with respect to the smaller wavefront aberration value x of the wavefront aberration value of the incident surface and the wavefront aberration value of the exit surface, The smaller one of the wavefront aberration value of the surface and the wavefront aberration value of the exit surface is 0 <x ≦ λ / 4, and the wavefront aberration value y of the reflection surface is 0 <y ≦ λ / 10. (Λ is the wavelength of the emitted light from the He—Ne laser).

  In the present invention, it can be molded in a short time and at a low cost.

(Embodiment 1)
In the first embodiment, a prism having a substantially triangular prism shape is taken as an example of the optical element, an imaging device is taken as an example of the optical device, and the configuration of the imaging device 100 and the configuration of the prism 10 are described with reference to FIGS. And the manufacturing method of the prism 10 is shown. FIG. 1 is a schematic diagram illustrating an arrangement configuration of an optical system of the imaging apparatus 100. A two-dot broken line in FIG. 1 indicates an optical axis, and an arrow in FIG. 1 indicates a traveling direction of light. FIG. 2 is a schematic diagram of the prism 10 of the present embodiment, FIG. 2A is a perspective view of the prism 10, and FIG. 2B is a diagram illustrating the function of the prism 10. FIG. 3 is a schematic diagram showing a configuration of the manufacturing apparatus 9 for the prism 10.

  First, the configuration of the imaging apparatus 100 will be described with reference to FIG.

  The imaging apparatus 100 is, for example, a DSC, DVC, mobile phone camera, projection TV, or the like, and includes a light receiving element such as an imaging element and an imaging optical system. The imaging optical system is an optical system that projects an optical image of a subject on a light receiving surface of a light receiving element. Specifically, as shown in FIG. 1, the first lens sequentially in the direction from the subject side toward the light receiving element S side. The group G1, the prism 10, the second lens group G2, and the third lens group G3 are arranged.

  In the imaging apparatus 100, light (mainly visible light) is incident on the first surface 11 of the prism 10 after being incident on the first lens group G1 from the subject side. The light incident from the first surface 11 is totally reflected by the reflection surface 13, bent 90 degrees, and emitted from the second surface 12. The light emitted from the second surface 12 passes through the second lens group G2, is condensed by the third lens group G3, is incident on the image sensor S, and is converted into an electrical signal. Note that visible light is an electromagnetic wave in a wavelength range that is perceived as light by human eyes, and is an electromagnetic wave of 360 to 400 nm or more and 760 to 830 nm or less, although there are individual differences.

  Next, the prism 10 is shown using FIG.

  The prism 10 is made of glass having a refractive index of 1.65 or more with respect to d-line (the wavelength of output light of a sodium lamp, 589.0 nm or 589.6 nm). Therefore, the optical total length of the optical system including the prism 10 can be shortened, and thus the size of the device including the optical system can be reduced. If visible light is incident on the prism 10, the visible light is totally reflected by a reflection surface 13 described later. The total reflection is to reflect with a reflectance of 90% or more, preferably with a reflectance of 95% or more, and more preferably with a reflectance of 97% or more.

  Further, as shown in FIG. 2A, the prism 10 is formed in a triangular prism shape having a substantially right triangle as a bottom surface, and includes a first surface 11, a second surface 12, a reflective surface 13, and a third surface 14. have. The first surface 11, the second surface 12, and the third surface 14 are each outside the side surface of the triangular prism.

  The first surface 11 and the second surface 12 are surfaces orthogonal to each other and are the incident surface or the exit surface of the prism 10. That is, if the first surface 11 is the incident surface, the second surface 12 is the outgoing surface, and if the second surface 12 is the incident surface, the first surface 11 is the outgoing surface.

  The reflecting surface 13 is the inside of the side surface having the largest area, and as shown in FIG. 2B, for example, the light incident on the first surface 11 is transmitted through the prism and reflected by the reflecting surface 13. The light exits from the second surface 12.

  The first surface 11, the second surface 12, and the reflecting surface 13 each have the following wavefront aberration values. Of the wavefront aberration value of the first surface 11 and the wavefront aberration value of the second surface 12, where x is the smaller wavefront aberration value and y is the wavefront aberration value of the reflecting surface 13, x and y are x / y> X is preferably 0 <x ≦ λ / 4, and y is preferably 0 <y ≦ λ / 10. Note that λ is the wavelength of output light from the He—Ne laser.

  Here, the wavefront aberration is a difference between an ideal wavefront and an actual wavefront, and is a value obtained by calculating an rms (Root Mean Square) value for the entire wavefront and dividing it by the wavelength of light. is there. The wavefront aberration is generally measured using a wavefront aberration measuring method described in JIS standard number JISC5935.

  In such a prism 10, the wavefront aberration value y of the reflecting surface 13 is 0 <y ≦ λ / 10. Therefore, the prism 10 has substantially the same optical performance as a prism formed using a corrected mold. Specifically, the prism 10 can reflect light without giving aberration to the incident wavefront.

  The wavefront aberration value y of the reflecting surface 13 is smaller than the wavefront aberration value of the first surface 11 and the wavefront aberration value of the second surface 12. Therefore, when the prism 10 is molded, as described later, the wavefront aberration value of the reflecting surface 13 may be made smaller than the wavefront aberration values of the first surface 11 and the second surface 12, and the corrected mold is processed. The wavefront aberration values of all optical surfaces may not be set to substantially the same value. As a result, as will be described later, the prism 10 does not have to be molded using a mold that has been subjected to correction processing, as compared to a prism that has been molded using a mold that has been subjected to correction processing. The molding time can be shortened and the molding cost can be reduced.

  Then, the manufacturing method of the prism 10 is shown using FIG.

  First, the manufacturing apparatus 9 shown in FIG. 3 is prepared. Specifically, first, the lower mold (push mold) 3 is placed in a cylindrical body (trunk mold) 4. At this time, the lower mold 3 to be used has a prism forming surface portion 3 a having a wavefront aberration value of λ / 4 or less, and the lower mold 3 is placed in the body 4 by arranging the prism forming surface portion 3 a upward. Next, the middle mold (push mold) 2 is placed on the lower mold 3. At this time, the middle mold 2 to be used has a prism forming surface portion 2 a having a wavefront aberration value of λ / 4 or less, and the middle mold 2 is placed in the body 4 without bringing the prism forming surface portion 2 a into contact with the inner wall of the body 4 and the lower mold 3. Put in. Thus, when the inside is seen from above the body 4, the prism molding surface portion 2 a of the middle mold 2 and the prism molding surface portion 3 a of the lower mold 3 can be seen.

  Next, the prism material 5 is prepared. Specifically, the material is glass having a refractive index with respect to d-line of 1.65 or more. In addition, the shape is not particularly limited, but if it is similar to the shape of the prism after molding, the amount of heat energy and heating time in the subsequent heating process can be reduced, and as a result, sink marks etc. are suppressed to the maximum. Since the prism can be formed, it is preferably substantially cylindrical, and more preferably substantially triangular.

  Subsequently, the prepared prism material 5 is placed in the body 4 of the manufacturing apparatus 9, and the upper die (push die) 1 is placed on the prism material 5. At this time, the upper die 1 to be used has a prism forming surface portion 1a having a wavefront aberration value of λ / 10 or less, and the upper die 1 is placed in the body 4 with the prism forming surface portion 1a facing downward. As a result, the prism forming surface portions 1 a, 2 a, and 3 a come into contact with the surface of the prism material 5.

  Subsequently, by using the upper heater block 6 installed on the upper mold 1 and the lower heater block 7 installed below the lower mold 3, the prism material 5 is heated to near the softening point temperature. Soften.

  Subsequently, pressure is applied to the upper mold 1 to press the prism material 5, and the prism forming surface portion 1 a of the upper mold 1 is transferred to the prism material 5. As described above, when the upper mold 1 is transferred to the prism material 5, transfer to the prism material 5 can be enhanced as compared with the case where the middle mold 2 and the lower mold 3 are transferred to the prism material 5. Thereby, the wavefront aberration value of the reflecting surface 13 of the prism 10 can be surely made λ / 10 or less.

  Then, the prism material 5 is cooled to near room temperature using the upper and lower heater blocks 6 and 7. At this time, it is preferable that the glass is gradually cooled to a temperature slightly lower than the glass softening point temperature and then rapidly cooled to around room temperature. Thereby, the prism 10 can be shape | molded.

  Below, the effect which the prism 10 in this embodiment show | plays is put together.

  The prism 10 is a prism having substantially the same optical performance as a prism molded using a mold subjected to correction processing, and can shorten the molding time and the molding cost, and can also reduce the DSC. It can be mounted on optical devices such as DVC, mobile phone cameras and projection TVs. Furthermore, the mounted optical device can be reduced in size.

  Further, since the reflecting surface 13 of the prism 10 is formed using a pressing die (upper die 1) that pressurizes the prism material 5, the wavefront aberration value can be surely made λ / 10 or less.

  Further, since the prism 10 is formed by using the press molding method, not only the prism having the shape shown in FIG. 2A but also various shapes of prisms can be formed.

(Embodiment 2)
In the second embodiment, the configuration of the prism 20 will be described with reference to FIG. FIG. 4 is a diagram schematically showing an end face of the prism 20 in the present embodiment.

  The prism 20 of the present embodiment is different from the prism 10 of the first embodiment in the following points. That is, the prism 20 is made of a resin having a refractive index with respect to the d line of 1.6 or more, and a reflective film 21 (for example, an aluminum film or a dielectric film) is formed on the third surface 14 of the prism 20. Yes. As described above, even if the prism is made of a resin having a refractive index with respect to the d line of 1.60 or more, if the reflective film 21 is formed on the third surface 14, the visible light can be totally reflected by the reflective surface 13. . Therefore, the prism 20 has substantially the same effect as the prism 10 of the first embodiment.

  In general, resin prisms are lighter than glass prisms. Therefore, it is preferable to mount the prism 20 of the present embodiment on an apparatus such as an imaging apparatus that is required to be lightweight. On the other hand, glass prisms are generally superior in heat shrinkability compared to resin prisms, and visible light can be totally reflected on a reflecting surface without forming a reflective film. Therefore, it is preferable to mount the prism 10 of the first embodiment on an apparatus such as an imaging apparatus that is required to have optical performance and low cost. As described above, the prism 10 of the first embodiment and the prism 20 of the present embodiment may be properly used according to the conditions required for the apparatus.

(Embodiment 3)
In the third embodiment, an illuminating device is taken as an example of an optical device, and the case where the prism 10 of the first embodiment is mounted on the illuminating device 200 is shown using FIG. FIG. 5 is a schematic diagram showing an arrangement configuration of the optical system of the illumination device 200. The two-dot broken line in FIG. 5 indicates the optical axis, and the arrow in FIG. 5 indicates the traveling direction of the light.

  The illumination device 200 is a single-lens reflex camera or the like, and includes a light source and an illumination optical system. The illumination optical system is an optical system that irradiates an object to be illuminated with light emitted from a light source. Specifically, as shown in FIG. 5, the illumination optical system sequentially in the direction from the light source L side toward the object to be illuminated. The first lens group G1, the second lens group G2, the prism 10, and the third lens group G3 are arranged.

  The light is emitted from the light source L, collimated by the first lens group G1, passes through the second lens group G2, and then enters the second surface 12 of the prism 10. The light incident on the second surface 12 is totally reflected by the reflecting surface 13, bent 90 degrees, and emitted from the first surface 11. The light emitted from the first surface 11 passes through the third lens group G3 and is emitted to the outside of the illumination device 200.

(Other embodiments)
The above-described Embodiment 1, 2, or 3 may have the following configuration.

  The prism has a triangular prism shape whose bottom surface is a substantially right triangle, but it is of course not limited to this shape. The wavefront aberration value y of the reflecting surface of the prism may be x / y> 2 with respect to the smaller wavefront aberration value x of the wavefront aberration value of the incident surface and the wavefront aberration value of the output surface, and x is 0 <x. ≦ λ / 4 and y may satisfy 0 <y ≦ λ / 10.

  The imaging device and the illumination device each have the glass prism of Embodiment 1 mounted thereon, but the resin prism of Embodiment 2 may be mounted.

  An antireflection film may be formed on the first surface and the second surface. Thereby, for example, light is preferably incident on the prism from the first surface with little reflection on the first surface and exits from the second surface with little reflection on the second surface.

In this example, the wavefront aberration values of the entrance surface, the exit surface, and the reflection surface of the prism were optimized. In addition, an optimized prism forming method was studied.
<Example 1>
In Example 1, the wavefront aberration value of the reflecting surface of the prism, the wavefront aberration value of the incident surface, and the wavefront aberration value of the exit surface were optimized.
-Optimization method-
First, the wavefront aberration value of the reflecting surface of the prism described in the first embodiment is the value described in Table 1, and the wavefront aberration value of the entrance surface and the wavefront aberration value of the exit surface are the values described in Table 2. (No. 1 prism to No. 6 prism) were prepared.

  Next, when the output light (633 nm) from the He-Ne laser is incident on each prism using an aberration measuring apparatus for reflected wavefront (GPI-xp manufactured by Zygo), the reflected light is reflected on the reflecting surface of each prism. The aberration of the reflected wavefront, the aberration of the reflected wavefront reflected by the incident surface of each prism, and the aberration of the reflected wavefront reflected by the exit surface of each prism were measured.

Subsequently, based on the resolution measurement method of the digital camera of the camera image equipment industry standard CIPADC-003-2003, the reflected wavefront measured by visual observation is observed to examine whether each prism can be mounted on a digital camera or the like. did.
-Result-
Table 1 shows the experimental results related to the optimization of the wavefront aberration value of the reflecting surface, and Table 2 shows the experimental results related to the optimization of the wavefront aberration values of the entrance surface and the exit surface. In Table 1, “X” indicates that the prism is not usable, “◯” indicates that the prism is usable, and “◎” indicates that the prism is very good. Further, Δ indicates that it can be used as a prism but is not in a preferable state.

  As shown in Table 1, it was found that the wavefront aberration value of the reflecting surface is preferably λ / 10 or less, and a smaller value is preferable.

  As shown in Table 2, it was found that the wavefront aberration values of the entrance surface and the exit surface are preferably λ / 4 or less, more preferably λ / 5 or less, and smaller values are more preferable.

From the above, a favorable projection evaluation could be obtained with a prism having a wavefront aberration value of the reflection surface of λ / 10 or less and a wavefront aberration value of the entrance surface and the exit surface of λ / 5 or less. Therefore, it can be said that the relationship between the wavefront aberration value x of the entrance surface and the exit surface and the wavefront aberration value y of the reflection surface is preferably x / y> 2.
<Example 2>
In Example 2, a method of forming a prism evaluated as good in Example 1 was studied using a glass prism material.

  A prism was formed using the manufacturing apparatus shown in FIG. Specifically, first, as the upper mold, an upper mold processed so that the wavefront aberration value of the prism molding surface portion is λ / 10 or less is used, and as the middle mold and the lower mold, the wavefront aberration value of the prism molding surface section is λ / Medium and lower molds processed to 4 or less were used. Further, as the prism material, a cylindrical molding material whose side surface is processed into a mirror surface (manufactured by Sumita Optical Glass Co., Ltd., K-VC78 (nd: 1.66910, Tg: 520 ° C., At: 556 ° C.)) is used. It was.

  Next, as shown in FIG. 3, the prism material was sandwiched between the middle mold, the lower mold, and the upper mold and accommodated in the body, and the temperature was raised to about 520 ° C. over 5 minutes. Then, pressure was supplied to the softened prism material by pushing down the upper mold, and the upper prism element forming surface portion was transferred to the prism material surface.

  Subsequently, the heater part of the lower heater block is gradually cooled to around 510 ° C. over 8 minutes, the heater part of the upper heater block is gradually cooled down to around 510 ° C. over 12 minutes, and then the upper and lower heaters The block heater was turned off and cooled rapidly to room temperature.

  Subsequently, the mold was taken out from the body of the manufacturing apparatus, the mold was disassembled, and the prism was removed. As a result, it was possible to obtain a triangular prism-like prism having a substantially right-angled isosceles triangle as a bottom surface (the equilateral side of the bottom surface is 10 mm, the hypotenuse of the bottom surface is 14 mm, and the height is 15 mm).

Then, according to the wavefront aberration measuring method described in JIS standard number JISC5935, the wavefront aberration values of the entrance surface, the exit surface, and the reflection surface were measured. Then, the wavefront aberration value of the reflecting surface was λ / 10 or less, and the wavefront aberration values of the entrance surface and the exit surface were λ / 4 or less.
<Example 3>
In Example 3, a method of forming a prism evaluated as good in Example 1 using a resin prism material was studied.

  A prism was molded using the manufacturing apparatus shown in FIG. 3 and the upper mold, middle mold, and lower mold described in Example 1 above. As the prism material, a cylindrically processed molding material (manufactured by Osaka Gas Chemical Co., Ltd., OKP4 (nd: 1.613, Tg: 124 ° C.)) was used.

  Next, as shown in FIG. 3, the prism material was sandwiched between the middle mold, the lower mold, and the upper mold and accommodated in the body, and the temperature was raised to 150 ° C. Then, pressure was supplied to the prism material softened by pressing the upper die down to perform pressure molding.

  Subsequently, the heater portion of the lower heater block was gradually cooled to 114 ° C. in 10 minutes, and then the energization of the heater portions of the upper and lower heater blocks was stopped and rapidly cooled to room temperature.

  Subsequently, the mold was taken out from the manufacturing apparatus, the mold was disassembled, and the prism was taken out. As a result, it was possible to obtain a triangular prism having a bottom surface with a substantially right-angled isosceles triangle (the equilateral side of the bottom surface is 9 mm, the hypotenuse of the bottom surface is 12 mm, and the height is 15 mm).

  Then, according to the wavefront aberration measuring method described in JIS standard number JISC5935, the wavefront aberration values of the entrance surface, the exit surface, and the reflection surface were measured. Then, the wavefront aberration value of the reflecting surface was λ / 10 or less, and the wavefront aberration values of the entrance surface and the exit surface were λ / 4 or less.

  From the results of Example 2 and the present example, the upper mold in which the wavefront aberration value of the prism molding surface portion is processed to λ / 10 or less, the middle mold in which the wavefront aberration value of the prism molding surface portion is processed to λ / 4 or less, and By using the lower mold, it was possible to mold the prism evaluated as good in Example 1 even when a resin prism material was used.

  As described above, the present invention is useful for an optical element and an optical device including the optical element, and particularly useful for a prism and an optical device including the prism.

FIG. 3 is a schematic diagram illustrating an arrangement configuration of an optical system of the imaging apparatus according to the first embodiment. FIG. 4 is a schematic diagram of a prism in the first and third embodiments. FIG. 3 is a waist cross-sectional view of the prism molding apparatus. FIG. 6 is a schematic diagram of an end face of a prism in the second embodiment. FIG. 6 is a schematic diagram illustrating an arrangement configuration of an optical system of an illumination device according to a third embodiment.

Explanation of symbols

5 Prism material (optical element material)
10 Prism (optical element)
11 First surface (incident surface or outgoing surface)
12 Second surface (outgoing surface or incident surface)
13 Reflecting surface 14 Third surface 100 Imaging device (optical device)
200 Illumination device (optical device)

Claims (8)

An incident surface, an emission surface, and a reflection surface are provided, and light that is incident substantially perpendicular to the incident surface is reflected by the reflection surface and emitted from the emission surface,
The wavefront aberration value y of the reflecting surface has a relationship of x / y> 2 with respect to the smaller wavefront aberration value x of the wavefront aberration value of the incident surface and the wavefront aberration value of the exit surface,
The smaller wavefront aberration value x of the wavefront aberration value of the incident surface and the wavefront aberration value of the exit surface is 0 <x ≦ λ / 4,
The optical element characterized in that the wavefront aberration value y of the reflecting surface is 0 <y ≦ λ / 10 (λ is a wavelength of light emitted from a He—Ne laser).   The incident surface and the reflecting surface form a predetermined angle so that visible light incident from the incident surface into the optical element is totally reflected by the reflecting surface. The optical element described.   The optical element according to claim 1, which is made of glass.   The optical element according to claim 1, wherein a refractive index with respect to d-line is 1.6 or more. A prism having a substantially triangular prism shape with the incident surface, the exit surface and the reflecting surface as side surfaces;
The optical element according to claim 1, wherein a reflection film having a characteristic of reflecting the incident light is formed on the reflection surface. An optical element having an entrance surface, an exit surface, and a reflection surface, and formed so that light incident substantially perpendicular to the entrance surface is reflected by the reflection surface and is emitted from the exit surface. An optical device disposed on the optical path,
The optical element is
The wavefront aberration value y of the reflecting surface is in a relationship of x / y> 2 with respect to the smaller wavefront aberration value x of the wavefront aberration value of the entrance surface and the wavefront aberration value of the exit surface,
The smaller wavefront aberration value x of the wavefront aberration value of the incident surface and the wavefront aberration value of the exit surface is 0 <x ≦ λ / 4,
The optical apparatus is characterized in that the wavefront aberration value y of the reflecting surface is 0 <y ≦ λ / 10 (λ is a wavelength of light emitted from a He—Ne laser). A light receiving element;
An imaging optical system that forms an optical image of a subject on a light receiving surface of the light receiving element;
The optical device according to claim 6, wherein the optical element is disposed on an optical path of the imaging optical system. A light source;
An illumination optical system that irradiates an object to be illuminated with illumination light emitted from the light source;
The optical device according to claim 6, wherein the optical element is disposed on an optical path of the illumination optical system.

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