JP2004075516A - Translucent ceramic, optical component and optical device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a translucent ceramic free from the occurrence of birefringence and having excellent optical characteristics, and an optical device using the same. <P>SOLUTION: The translucent ceramic has a composition which is expressed by a general formula, Ba(Zr<SB>x</SB>Zn<SB>y</SB>Ta<SB>z</SB>)<SB>v</SB>O<SB>w</SB>(where, x+y+z=1; 0.01≤x≤0.06; 0.29≤y≤0.36; 0.58≤z≤0.7; 1<v≤1.05; (w) is an optional number) and in which (x), (y) and (z) in the general formula are in a region surrounded by a quadrangle ABCD in a ternary diagram expressed by Figure 1. The translucent ceramic has the refractive index of ≥2.0 and ≥20% linear transmissivity and does not cause the birefringence. The translucent ceramic is used as a collimating lens, a half mirror, an objective lens, a condenser lens or the like in an optical pickup. <P>COPYRIGHT: (C)2004,JPO

Description

【００３１】
表１に示す試料のうち、高い直線透過率が得られた試料１４について、紫外から赤外の波長帯（λ＝２００〜９００ｎｍ）における直線透過率を測定した。この測定結果を図２に示す。同図から、試料１４はλ＝４００〜９００ｎｍの波長領域において高い透過率を示すことが分かる。
【００３２】
また、試料１４について、λ＝６３３ｎｍにおけるＴＥモードおよびＴＭモードでの屈折率を測定した結果を表２に示す。表２において、ＴＥモードおよびＴＭモードでの屈折率が同じ値であることから、複屈折が生じていないことが分かる。
【００３３】
【表２】

【００３４】
ここで、試料１４の直線透過率は７５．４％であり、屈折率は２．１３１であった。一般に、直線透過率の測定においては、空気中から試料に対して垂直に光が入射する。このため、例えば、屈折率（ｎ）が２．１３１である場合、Ｆｒｅｓｎｅｌの法則より、試料表面での反射率と裏面での反射率の合計は２４．４％となる。よって、屈折率が２．１３１である試料の直線透過率の理論最大値は、７５．６％となる。試料１４において、直線透過率は７５．４％であるから、理論値に対する相対透過率は約９９．７％となる。これは、焼結体内部での透過損失がほとんどないことを示している。したがって、試料１４の表面に反射防止膜（ＡＲ膜＝Ａｎｔｉ−Ｒｅｆｌｅｃｔｉｏｎ膜）を形成すれば、得られる直線透過率をほぼ理論値とすることができる。このように、本発明の組成を有する透光性セラミックスは、光学素子として利用可能な優れた特性を有するものである。
【００３５】
また、試料１４に対して、比較例として、鋳込み成形による２インチ角の成形体を１５５０℃で焼成して焼結体を得た。表３は、この試料１４と比較例の直線透過率および屈折率を対比したものである。表３において、両者の直線透過率および屈折率は、互いに同等の値である。このように、本発明の組成を有する透光性セラミックスによれば、成形法に関わらず高い直線透過率および屈折率が得られることが分かる。
【００３６】
【表３】

【００３７】
図１は、本発明の透光性セラミックスの組成である一般式Ｂａ（Ｚｒ_ｘＺｎ_ｙＴａ_ｚ）_ｖＯ_ｗ（但し、ｗは任意の数）におけるｘ、ｙ、ｚの組成範囲を示す三元図である。
【００３８】
同図において、Ａ，Ｂ，Ｃ，Ｄの各点を結んだ多角形ＡＢＣＤで囲まれた領域が、本発明の透光性セラミックスの組成範囲である。この組成を有する焼結体は、直線透過率が２０％以上となり、屈折率は２．１前後の高い値となる。さらに、Ｅ，Ｆ，Ｇ，Ｈの各点を結んだ四角形ＥＦＧＨで囲まれた領域の組成を有する焼結体では、直線透過率が５０％以上となり、屈折率は同じく２．１前後の高い値となる。
【００３９】
また、表１における試料番号の一部を図１上に示した。図１において、試料番号に＊印を付したものは、表１においても同じ印が付された、本発明の範囲外の試料である。
【００４０】
【実施例２】
この実施例２は、一般式Ｂａ（Ｚｒ_ｘＺｎ_ｙＴａ_ｚ）_ｖＯ_ｗで表され、この一般式のｘ，ｙ，ｚが図１に示す三元図における各点Ｅ，Ｆ，Ｇ，Ｈを結んだ四角形ＥＦＧＨで囲まれた領域内にある組成を有する主成分に、微量の酸化物を添加したものである。ここでは、微量の酸化物を添加することにより、直線透過率および屈折率を変化させた。
【００４１】
主成分としては、実施例１における表１の試料１４を用いた。実施例１と同様に、高純度のＢａＣＯ_３，ＳｎＯ_２，ＺｒＯ_２，ＭｇＣＯ_３およびＴａ_２Ｏ_５を準備した。表１の試料１４と同じ組成が得られるように、各原料を秤量した。また、微量の酸化物として、Ａｌ_２Ｏ_３，Ｙ_２Ｏ_３，ＣｕＯ，ＴｉＯ_２，Ｇａ_２Ｏ_３，ＷＯ_３，Ｌａ_２Ｏ_３，Ｓｍ_２Ｏ_３，Ｅｕ_２Ｏ_３，Ｎｄ_２Ｏ_３，Ｇｄ_２Ｏ_３，Ｄｙ_２Ｏ_３，Ｈｏ_２Ｏ_３，Ｙｂ_２Ｏ_３，Ｅｒ_２Ｏ_３，Ｌｉ_２ＣＯ_３，ＢａＴｉＯ_３を準備し、主成分に対する添加量が表４、表５のとおりになるように秤量した。なお、Ｌｉ_２ＣＯ_３については、Ｌｉ_２Ｏに換算した添加量となっている。このように秤量した主成分原料および添加物原料を混合した。そして、実施例１と同じ要領で仮焼、粉砕、焼成したものを鏡面加工して透光性セラミックスの試料を得た。
【００４２】
上記試料のそれぞれについて、可視光領域（λ＝６３３ｎｍ）における直線透過率および屈折率を測定した。この測定結果を表４、用５に示す。表４、表５において、試料番号に＊印を付したものは本発明の範囲外のものであり、いずれも直線透過率が２０％未満のものである。
【００４３】
【表４】

【００４４】
【表５】

【００４５】
表４、表５と表１の各値を比較すると、各酸化物の添加量に応じて直線透過率および屈折率が増減することが分かる。ここで、一般に、光学部品においては、用途に応じて特性が細分化されており、屈折率については、小数点以下第５位の値までの精度が要求されることが多い。表１と表４、表５とで、屈折率は、小数点以下第３位において異なる値となっており、光学部品として明確に異なる特性を有するものと言える。
【００４６】
このように、酸化物の添加の有無を選択したり、添加量を調整したりすることにより、光学部品としての用途に応じて異なる特性の透光性セラミックスを得ることができる。
【００４７】
また、表４の試料７および表５の試料９２について、それぞれ、λ＝６３３ｎｍにおけるＴＥモードおよびＴＭモードでの屈折率を測定した結果を表６に示す。表６において、ＴＥモードおよびＴＭモードでの屈折率が同じ値であることから、複屈折が生じていないことが分かる。
【００４８】
【表６】

【００４９】
【実施例３】
上述のように、実施例１，２にかかる透光性セラミックスは、直線透過率および屈折率において高い値を示し、複屈折も生じないため、光学部品への利用が望める。例えば、図３示すような両凸レンズ１０、または両凹レンズ１１、あるいは光路長調整板１２、さらには球状レンズ１３等の素材として好適である。
【００５０】
このような光学部品を搭載した光学素子として、光ピックアップを例に取り、説明する。
【００５１】
光ピックアップは、図４に示すように、コンパクトディスクやミニディスクといった記録媒体１に対して、コヒーレントな光であるレーザ光を照射し、その反射光から記録媒体１に記録された情報を再生するものである。
【００５２】
このような光ピックアップにおいては、光源としての半導体レーザ素子５からのレーザ光を平行光に変換するコリメータレンズ４が設けられ、その平行光の光路上にハーフミラー３が設けられている。このハーフミラー３は、コリメータレンズ４からの入射光は通して直進させるが、記録媒体１からの反射光については、反射光の進行方向を例えば約９０度の反射により変更するものである。
【００５３】
また、光ピックアップには、ハーフミラー３からの入射光を記録媒体１の記録面上に集光するための対物レンズ２が設けられている。この対物レンズ２は、記録媒体１からの反射光を効率よくハーフミラー３に対して出射するものでもある。反射光が入射されたハーフミラー３では、反射により位相が変化することで、上記反射光の進行方向が変更される。
【００５４】
さらに、光ピックアップには、変更された反射光を集光するための集光レンズ６が設けられている。そして、反射光の集光位置に、反射光から情報を再生するための受光素子７が設けられている。
【００５５】
このように構成される光ピックアップにおいて、対物レンズ２の素材として、本発明にかかる透光性セラミックスを用いることができる。この透光性セラミックスは屈折率が大きいため、光ピックアップの小型化や薄型化が可能であり、開口を増加させることができる。
【００５６】
なお、本実施例においては、本発明の透光性セラミックスを対物レンズ２に用いた場合について説明したが、他の光学部品、例えば、コリメータレンズ４または集光レンズ６、あるいはハーフミラー３に用いることもできる。
【００５７】
また、本発明は、上記実施例に限定されるものではなく、特許請求の範囲内で適宜、変更を加えることができる。例えば、原料の形態は酸化物もしくは炭酸塩に限定されるものではなく、焼結体とした段階で所望の特性が得られる原料であればよい。また、焼成雰囲気について、上記実施例の約９８％という酸素濃度の値は、使用した実験設備の条件下において最も好ましい値である。この条件下においては、９０％以上の酸素濃度が確保できれば、所望の特性を備えた焼結体が得られる。
【００５８】
【発明の効果】
本発明の透光性セラミックスは、常誘電体であり、かつ多結晶体であるため、複屈折を生じない。したがって、レンズ等の光学部品に容易に適用できる。
【００５９】
また、本発明の透光性セラミックスは、２０％以上さらには５０％以上の高い直線透過率と２．０以上の高い屈折率を有する。このため、比較的小さな外形寸法で所望の光学特性を発揮することができる。
【００６０】
また、本発明の透光性セラミックスは、主成分に対して酸化物を添加することにより、光学部品としての用途に応じて、直線透過率および屈折率を変化させることが可能である。
【００６１】
また、本発明の光学素子においては、上述の高い光学特性を有する透光性セラミックスが光学部品として用いられているため、光学素子の小型化、薄型化を実現することができる。
【図面の簡単な説明】
【図１】本発明の透光性セラミックスの組成範囲を示す三元図である。
【図２】本発明の透光性セラミックスの直線透過率を示すグラフである。
【図３】本発明の透光性セラミックスからなる光学部品の説明図であり、（ａ）は両凸レンズを示し、（ｂ）は両凹レンズを示し、（ｃ）は光路長調整板を示し、（ｄ）は球状レンズを示す。
【図４】本発明の透光性セラミックスからなる光学部品を搭載した光学素子の一実施例（光ピックアップ）を示す説明図である。
【符号の説明】
２　　対物レンズ（光学部品）
１０　　両凸レンズ（光学部品）
１１　　両凹レンズ（光学部品）
１２　　光路長調整板（光学部品）
１３　　球状レンズ（光学部品）[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a translucent ceramic which is a paraelectric having a high refractive index and a high light transmittance and is useful as an optical component, and an optical element using the same.
[0002]
[Prior art]
Conventionally, as a material of an optical component mounted on an optical element such as an optical pickup, glass or plastic, or niobate, as described in JP-A-5-107467 and JP-A-9-245364, for example, has been used. A single crystal such as lithium (LiNbO ₃ ) is used.
[0003]
Glass and plastic are used for optical components such as lenses because of their high light transmittance and easy processing into a desired shape. In addition, a single crystal of LiNbO ₃ is used for an optical component such as an optical waveguide by utilizing its electrochemical characteristics and birefringence. Optical elements such as optical pickups using such optical components are required to be further reduced in size and thickness. (For example, see Patent Documents 1 and 2.)
[0004]
[Patent Document 1]
JP-A-5-107467 (all pages, all drawings)
[Patent Document 2]
JP-A-7-244856 (Claim 6, paragraph number 0024)
[0005]
[Problems to be solved by the invention]
Since the above-mentioned conventional glass and plastic have a refractive index of less than 1.9, there is a limit to miniaturization and thinning of optical components and optical elements using them. Further, plastic has a hygroscopic property, and further, has a low refractive index and generates birefringence, so that there is a problem in efficiently transmitting and condensing incident light. Furthermore, although a single crystal such as LiNbO ₃ has a high refractive index (n = 2.3), it generates birefringence, so that it cannot be used for an optical component such as a lens, and its use is limited.
[0006]
In view of the above, an object of the present invention is to provide a translucent ceramic having excellent optical characteristics that does not cause birefringence, and an optical element using the same.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the first invention of the present application is directed to a general formula Ba (Zr _x Zn _y T _az ) _v O _w (where x + y + z = 1, 0.01 ≦ x ≦ 0.06, 0.29 ≦ y ≦ 0.36, 0.58 ≦ z ≦ 0.7, 1 <v ≦ 1.05, w is an arbitrary number), and x, y, and z of the general formula are three In the original diagram, each point A (0.06, 0.36, 0.58), B (0.01, 0.36, 0.63), C (0.01, 0.29, 0.7) , D (0.06, 0.29, 0.65). A translucent ceramic having a composition within a region surrounded by a square ABCD.
[0008]
Further, the second invention of the present invention is the translucent ceramic according to the first invention, which has a refractive index of 2.0 or more and a linear transmittance of 20% or more.
[0009]
Further, the third invention of the present invention is directed to the general formula Ba (Zr _x Zn _y T _az ) _v O _w (where x + y + z = 1, 0.02 ≦ x ≦ 0.05, 0.3 ≦ y ≦ 0.35) 0.6 ≦ z ≦ 0.68, 1 <v ≦ 1.05, w is an arbitrary number), and x, y, and z in the general formula are each point in the ternary diagram shown in FIG. E (0.05, 0.35, 0.6), F (0.02, 0.35, 0.63), G (0.02, 0.3, 0.68), H (0.05 , 0.3, 0.65) is a translucent ceramic characterized by having a composition within a region surrounded by a square EFGH.
[0010]
Further, the fourth invention is the translucent ceramic according to the third invention, wherein the refractive index is 2.0 or more and the linear transmittance is 50% or more.
[0011]
Also, in the fifth invention according to the third invention, in the third invention, Al ₂ O ₃ , Y ₂ O ₃ , CuO, TiO ₂ , Ga ₂ O ₃ , WO ₃ , La ₂ O ₃ are added to the main components. , Sm ₂ O ₃ , Eu ₂ O ₃ , Nd ₂ O ₃ , Gd ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Yb ₂ O ₃ , Er ₂ O ₃ Is 1% by mol or less.
[0012]
The sixth invention of the present invention is the translucent ceramic according to the third invention, wherein Li ₂ O or BaTiO ₃ is added in an amount of 2 mol% or less to the main component.
[0013]
A seventh invention of the present application is the translucent ceramic according to any one of the first to sixth inventions, which is a paraelectric substance and is a polycrystal.
[0014]
Further, an eighth aspect of the present invention is an optical component comprising the translucent ceramic according to any one of the first to seventh aspects of the present invention.
[0015]
A ninth aspect of the present invention is an optical element including the optical component according to the eighth aspect of the present invention.
[0016]
Here, the paraelectric substance has a property that the permittivity does not change even when an electric field is applied. Since the translucent ceramic of the present invention is a paraelectric and polycrystalline, it does not cause birefringence. Therefore, it can be easily applied to optical components such as lenses.
[0017]
The translucent ceramic of the present invention has a high linear transmittance of 20% or more or 50% or more and a high refractive index of 2.0 or more. Therefore, desired optical characteristics can be exhibited with relatively small external dimensions.
[0018]
The translucent ceramic of the present invention can change the linear transmittance and the refractive index according to the use as an optical component by adding an oxide to the main component.
[0019]
Further, in the optical element of the present invention, since the above-described translucent ceramics having high optical characteristics is used as an optical component, the optical element can be reduced in size and thickness.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
[0021]
Embodiment 1
The procedure for producing the translucent ceramic of the present invention will be described.
[0022]
First, high-purity BaCO ₃ , ZrO ₂ , ZnO and Ta ₂ O ₅ were prepared as raw materials. Then, each raw material is weighed so as to obtain each sample shown in Table 1 represented by the general formula Ba (Zr _x Zn _y T _az ) _v O _w (w is an arbitrary number), and is weighed with a ball mill for 16 hours. Wet mixed. After drying this mixture, it was calcined at 1200 ° C. for 3 hours to obtain a calcined product. After calcination, the value of w was almost 3.
[0023]
The calcined product was put into a ball mill together with water and an organic binder, and wet-pulverized for 16 hours. For example, ethyl cellulose is used as the organic binder. Other than ethylcellulose, it has a function as a binder for a ceramic molded body, and reacts with oxygen in the atmosphere at about 500 ° C. before reaching a sintering temperature in a sintering step, for example. Any substance that can be converted to disappear can be used as an organic binder.
[0024]
After the above-mentioned pulverized material is dried, it is granulated through a 50-mesh net (sieve), and the obtained powder is pressed at a pressure of 2000 kg / cm ² , thereby forming a disk-shaped product having a diameter of 30 mm and a thickness of 2 mm. Got a body.
[0025]
Next, the compact was embedded in the same composition powder. Here, the powder of the same composition is obtained by calcining and pulverizing a raw material prepared to have the same composition as the above-mentioned molded body. With this same composition powder, it is possible to suppress volatilization of volatile components in the above-mentioned molded product during firing. The powder of the same composition preferably has the same composition as that of the above-mentioned molded body, but may not have the exact same composition as long as the powder has the same composition. Further, it is not always necessary to provide a light-transmitting property.
[0026]
The molded body embedded in the powder having the same composition was placed in a firing furnace, heated in an air atmosphere, and debindered. Subsequently, oxygen was injected into the furnace while increasing the temperature, and at a maximum temperature of 1550 ° C., the oxygen concentration in the firing atmosphere was increased to about 98%. While maintaining the firing temperature and the oxygen concentration, the molded product was fired for 10 hours to obtain a sintered body. The total pressure during firing was 1 atm or less.
[0027]
The sintered body thus obtained was mirror-finished and finished in a disk shape having a thickness of 0.4 mm to obtain a light-transmitting ceramic sample.
[0028]
For each of the above samples, the linear transmittance and the refractive index in the visible light region (λ = 633 nm) were measured. For the measurement of the linear transmittance, a spectrophotometer (UV-200S) manufactured by Shimadzu was used. For the measurement of the refractive index, a prism coupler (MODEL2010) manufactured by Metricon was used.
[0029]
Table 1 shows the measurement results of the linear transmittance and the refractive index described above. In Table 1, samples marked with an asterisk (*) are out of the scope of the present invention, and are all unsintered or have a linear transmittance of less than 20%.
[0030]
[Table 1]

[0031]
Among the samples shown in Table 1, the linear transmittance in the ultraviolet to infrared wavelength band ([lambda] = 200 to 900 nm) was measured for the sample 14 having a high linear transmittance. FIG. 2 shows the measurement results. From the figure, it can be seen that the sample 14 shows a high transmittance in the wavelength range of λ = 400 to 900 nm.
[0032]
Table 2 shows the measurement results of the refractive index of the sample 14 in the TE mode and the TM mode at λ = 633 nm. In Table 2, since the refractive indices in the TE mode and the TM mode have the same value, it can be seen that no birefringence has occurred.
[0033]
[Table 2]

[0034]
Here, the linear transmittance of Sample 14 was 75.4%, and the refractive index was 2.131. Generally, in the measurement of linear transmittance, light is perpendicularly incident on a sample from the air. Therefore, for example, when the refractive index (n) is 2.131, the total of the reflectance on the sample surface and the reflectance on the back surface is 24.4% according to Fresnel's law. Therefore, the theoretical maximum value of the linear transmittance of the sample having the refractive index of 2.131 is 75.6%. In sample 14, the linear transmittance is 75.4%, and the relative transmittance to the theoretical value is about 99.7%. This indicates that there is almost no transmission loss inside the sintered body. Therefore, if an anti-reflection film (AR film = Anti-Reflection film) is formed on the surface of the sample 14, the obtained linear transmittance can be made almost a theoretical value. Thus, the translucent ceramic having the composition of the present invention has excellent characteristics that can be used as an optical element.
[0035]
As a comparative example, a 2 inch square molded body was cast at 1550 ° C. on the sample 14 by casting to obtain a sintered body. Table 3 compares the linear transmittance and the refractive index of the sample 14 with the comparative example. In Table 3, the linear transmittance and the refractive index of both are the same value. Thus, according to the translucent ceramic having the composition of the present invention, it is understood that a high linear transmittance and a high refractive index can be obtained regardless of the molding method.
[0036]
[Table 3]

[0037]
FIG. 1 shows the composition ranges of x, y, and z in the general formula Ba (Zr _x Zn _y T _az ) _v O _w (where w is an arbitrary number), which is the composition of the translucent ceramic of the present invention. It is an original figure.
[0038]
In the drawing, a region surrounded by a polygon ABCD connecting points A, B, C, and D is a composition range of the translucent ceramic of the present invention. The sintered body having this composition has a linear transmittance of 20% or more and a refractive index of about 2.1. Furthermore, in a sintered body having a composition in a region surrounded by a square EFGH connecting points E, F, G, and H, the linear transmittance is 50% or more, and the refractive index is as high as about 2.1. Value.
[0039]
Some of the sample numbers in Table 1 are shown in FIG. In FIG. 1, those marked with an asterisk (*) in the sample number are samples out of the scope of the present invention, which are also marked in Table 1 with the same mark.
[0040]
Embodiment 2
Example 2 is represented by the general formula Ba (Zr _x Zn _y T _az ) _v O _w , where x, y, and z of the general formula are points E, F, G, and G in the ternary diagram shown in FIG. A small amount of oxide is added to a main component having a composition in a region surrounded by a square EFGH connecting H. Here, the linear transmittance and the refractive index were changed by adding a small amount of oxide.
[0041]
Sample 14 in Table 1 in Example 1 was used as a main component. As in Example 1, high purity BaCO ₃ , SnO ₂ , ZrO ₂ , MgCO ₃ and Ta ₂ O ₅ were prepared. Each raw material was weighed so as to obtain the same composition as Sample 14 in Table 1. Further, as a trace amount of oxide, Al ₂ O ₃ , Y ₂ O ₃ , CuO, TiO ₂ , Ga ₂ O ₃ , WO ₃ , La ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Nd ₂ O ₃ , Gd ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Yb ₂ O ₃ , Er ₂ O ₃ , Li ₂ CO ₃ , and BaTiO ₃ were prepared, and the added amount to the main component was as shown in Tables 4 and 5. Was weighed so that Note that the _Li 2 CO _3, has a amount in terms of Li ₂ O. The thus weighed main component raw materials and additive raw materials were mixed. Then, the calcined, pulverized, and calcined material was mirror-finished in the same manner as in Example 1 to obtain a translucent ceramic sample.
[0042]
For each of the above samples, the linear transmittance and the refractive index in the visible light region (λ = 633 nm) were measured. The measurement results are shown in Table 4 and Item 5. In Tables 4 and 5, samples marked with an asterisk (*) are out of the scope of the present invention, and all have a linear transmittance of less than 20%.
[0043]
[Table 4]

[0044]
[Table 5]

[0045]
Comparison of the values in Tables 4 and 5 with Table 1 shows that the linear transmittance and the refractive index increase and decrease according to the amount of each oxide added. Here, in general, the characteristics of an optical component are subdivided according to the application, and the refractive index is often required to have an accuracy up to the fifth decimal place. In Table 1, Table 4, and Table 5, the refractive index has different values at the third decimal place, and it can be said that the optical components have clearly different characteristics.
[0046]
As described above, by selecting the presence or absence of addition of an oxide or adjusting the addition amount, a translucent ceramic having different characteristics depending on the use as an optical component can be obtained.
[0047]
Table 6 shows the results of measuring the refractive index in the TE mode and the TM mode at λ = 633 nm for Sample 7 in Table 4 and Sample 92 in Table 5, respectively. In Table 6, since the refractive index is the same in the TE mode and the TM mode, it can be seen that no birefringence occurs.
[0048]
[Table 6]

[0049]
Embodiment 3
As described above, the translucent ceramics according to Examples 1 and 2 exhibit high values of the linear transmittance and the refractive index and do not cause birefringence, and thus can be used for optical components. For example, it is suitable as a material for a biconvex lens 10, a biconcave lens 11, an optical path length adjusting plate 12, and a spherical lens 13 as shown in FIG.
[0050]
As an optical element having such optical components mounted thereon, an optical pickup will be described as an example.
[0051]
As shown in FIG. 4, the optical pickup irradiates a recording medium 1 such as a compact disk or a mini disk with a laser beam, which is coherent light, and reproduces information recorded on the recording medium 1 from the reflected light. Things.
[0052]
In such an optical pickup, a collimator lens 4 for converting laser light from a semiconductor laser element 5 as a light source into parallel light is provided, and a half mirror 3 is provided on an optical path of the parallel light. The half mirror 3 allows the incident light from the collimator lens 4 to pass therethrough and travels straight, but the reflected light from the recording medium 1 changes the traveling direction of the reflected light by, for example, reflection at about 90 degrees.
[0053]
Further, the optical pickup is provided with an objective lens 2 for converging incident light from the half mirror 3 on the recording surface of the recording medium 1. The objective lens 2 also efficiently emits reflected light from the recording medium 1 to the half mirror 3. In the half mirror 3 on which the reflected light is incident, the traveling direction of the reflected light is changed by changing the phase by reflection.
[0054]
Further, the optical pickup is provided with a condenser lens 6 for collecting the changed reflected light. A light receiving element 7 for reproducing information from the reflected light is provided at a position where the reflected light is collected.
[0055]
In the optical pickup configured as described above, the translucent ceramic according to the present invention can be used as a material of the objective lens 2. Since this translucent ceramic has a large refractive index, the size and thickness of the optical pickup can be reduced, and the aperture can be increased.
[0056]
In this embodiment, the case where the translucent ceramic of the present invention is used for the objective lens 2 has been described, but it is used for another optical component, for example, the collimator lens 4 or the condenser lens 6 or the half mirror 3. You can also.
[0057]
Further, the present invention is not limited to the above-described embodiment, and can be appropriately modified within the scope of the claims. For example, the form of the raw material is not limited to oxides or carbonates, but may be any raw material that can obtain desired characteristics at the stage of forming a sintered body. As for the firing atmosphere, the value of the oxygen concentration of about 98% in the above embodiment is the most preferable value under the conditions of the experimental equipment used. Under these conditions, if an oxygen concentration of 90% or more can be secured, a sintered body having desired characteristics can be obtained.
[0058]
【The invention's effect】
Since the translucent ceramic of the present invention is a paraelectric and polycrystalline, it does not cause birefringence. Therefore, it can be easily applied to optical components such as lenses.
[0059]
Further, the translucent ceramic of the present invention has a high linear transmittance of 20% or more, more preferably 50% or more, and a high refractive index of 2.0 or more. Therefore, desired optical characteristics can be exhibited with relatively small external dimensions.
[0060]
The translucent ceramic of the present invention can change the linear transmittance and the refractive index according to the use as an optical component by adding an oxide to the main component.
[0061]
Further, in the optical element of the present invention, since the above-described translucent ceramics having high optical characteristics is used as an optical component, the optical element can be reduced in size and thickness.
[Brief description of the drawings]
FIG. 1 is a ternary diagram showing a composition range of a translucent ceramic of the present invention.
FIG. 2 is a graph showing the linear transmittance of the translucent ceramic of the present invention.
3A and 3B are explanatory diagrams of an optical component made of the translucent ceramic of the present invention, wherein FIG. 3A shows a biconvex lens, FIG. 3B shows a biconcave lens, and FIG. 3C shows an optical path length adjusting plate; (D) shows a spherical lens.
FIG. 4 is an explanatory view showing an embodiment (optical pickup) of an optical element on which an optical component made of a translucent ceramic of the present invention is mounted.
[Explanation of symbols]
2 Objective lens (optical parts)
10 Biconvex lenses (optical components)
11 Biconcave lens (optical parts)
12 Optical path length adjustment plate (optical component)
13. Spherical lens (optical parts)

Claims (9)

General formula Ba (Zr _x Zn _y T _az ) _v O _w (however, x + y + z = 1, 0.01 ≦ x ≦ 0.06, 0.29 ≦ y ≦ 0.36, 0.58 ≦ z ≦ 0.7 , 1 <v ≦ 1.05, w is an arbitrary number).
In the ternary diagram shown in FIG. 1, x, y, and z of the general formula are points A (0.06, 0.36, 0.58),
B (0.01, 0.36, 0.63),
C (0.01, 0.29, 0.7),
D (0.06, 0.29, 0.65)
A translucent ceramic characterized in that it has, as a main component, a composition in a region surrounded by a square ABCD connecting. The translucent ceramic according to claim 1, wherein the refractive index is 2.0 or more and the linear transmittance is 20% or more. General formula Ba (Zr _x Zn _y T _az ) _v O _w (however, x + y + z = 1, 0.02 ≦ x ≦ 0.05, 0.3 ≦ y ≦ 0.35, 0.6 ≦ z ≦ 0.68) , 1 <v ≦ 1.05, w is an arbitrary number).
In the ternary diagram shown in FIG. 1, x, y, and z of the general formula are points E (0.05, 0.35, 0.6),
F (0.02,0.35,0.63),
G (0.02, 0.3, 0.68),
H (0.05, 0.3, 0.65)
A translucent ceramic characterized by comprising, as a main component, a composition in a region surrounded by a square EFGH connecting the EFGHs. The translucent ceramic according to claim 3, wherein the refractive index is 2.0 or more and the linear transmittance is 50% or more. With respect to the main component, Al ₂ O ₃ , Y ₂ O ₃ , CuO, TiO ₂ , Ga ₂ O ₃ , WO ₃ , La ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Nd ₂ O ₃ , At least one oxide selected from Gd ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Yb ₂ O ₃ and Er ₂ O ₃ is added in an amount of 1 mol% or less. 4. The translucent ceramic according to 3. 4. The translucent ceramic according to claim 3, wherein Li ₂ O or BaTiO ₃ is added to the main component in an amount of ₂ mol% or less. 5. The translucent ceramic according to any one of claims 1 to 6, which is a paraelectric and polycrystalline. An optical component comprising the translucent ceramic according to claim 1. An optical element comprising the optical component according to claim 8 mounted thereon.

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