JP3713022B2 - projector - Google Patents

Description

【００９９】
【表２】

【０１００】
前記式（１）、（２）の各変数の値、及び式（１）、（２）の値は、下記の通りである。
【０１０１】
α０＝２．３×１０^-5
α１＝１．０×１０^-4
Ｌ＝５０ｍｍ
ｆ＝３７．０８ｍｍ
｜（α１―α０）／α０｜＝３．３５
Ｌ×α−６．８×１０^-5×ｆ＝１．８１×１０^-3
レンズ３２ｂ、３２ｃ、３３ｃ、３３ｄ、３３ｇ、３３ｉは、異常分散ガラスであり、屈折率の温度依存係数（Δｎ／ΔＴ）が負で、温度に対するパワーの変化が大きい。図８において、ズームレンズを構成する各レンズの温度上昇によって、フォーカス位置が図面に向かって右方向に移動する。本実施例の広角端の状態では、温度変化１度に対してフォーカス位置は、０．００６８ｍｍ移動する。
【０１０２】
ここで、レンズ枠３５、３６、３７、固定筒３０、及びカム環３４は、アルミニウムで形成されている。補正筒３８は樹脂で形成されており、例えばナイロン６６、ポリアセタールである。ナイロン６６の線膨張係数は１．０×１０^-4であり、ポリアセタールの線膨張係数は８．５×１０^-5である。これらの値は、アルミニウムの線膨張係数の２．３×１０^-5に対して４倍程度であり、温度上昇による単位長さ当たりの伸びも４倍程度となる。
【０１０３】
本実施例では、補正筒３８はナイロン６６で形成しており、線膨張係数α１は１．０×１０^-4であり、長さＬは５０ｍｍである。このため、温度上昇１度に対して、補正筒５１はα１×Ｌ＝０．００５ｍｍ伸びることになる。したがって、前記のフォーカス位置の変動量０．００６８ｍｍは、０．００５ｍｍ分だけ補正され、残存するフォーカス位置の温度１度当たりの変動量は、０．００１８ｍｍ／度となる。
【０１０４】
本実施例のセットでは、電源投入後においてレンズの温度は常温から１５度上昇する。例えば、周囲温度２０度で電源を投入すると、レンズ温度は２０度から３５度まで１５度上昇する。このため、使用時においては、温度上昇によるフォーカス位置の変動量は、０．００１８ｍｍ／度×１５度＝０．０２７ｍｍとなり、この値はセットの許容範囲内となる。すなわち、本実施例では、温度変化によるフォーカス位置の変動を小さく抑えることができ、良好な画質を維持できる。
【０１０５】
（実施の形態７）
図９は、本発明の実施の形態７に係るプロジェクタの構成図である。図９において、４０は前記実施の形態で示したレンズ鏡筒、４１は光学像を形成する空間光変調素子、４２は凹面鏡付き光源である。４３は投写された映像のフォーカス面である。本実施の形態によれば光源４２により照明される空間光変調素子４１に形成された光学像は、レンズ鏡筒４０の投写レンズによってフォーカス面４３に拡大投写される。
【０１０６】
レンズ鏡筒４０の投写レンズに前記実施の形態で示したレンズを用いることによって、温度変化によってフォーカス面４３の光軸方向の移動が少なく、温度が変化しても良好な画面が得られるプロジェクタが得られる。
【０１０７】
なお、本発明に係るレンズ鏡筒は、温度変化に対するフォーカス位置の変動を抑えることができ、ズームレンズにも対応できるので、プロジェクタに限らず、画像情報をフィルム、ＣＣＤ等の撮像手段面上に形成するビデオカメラ、フィルムカメラ、デジタルカメラ等の光学機器にも有用である。
【０１０８】
（実施の形態８）
図１０は、実施の形態８に係るプロジェクタの構成図である。図１０において、５０は筐体、５１は前記実施の形態で示したレンズ鏡筒、５２は光学像を形成する空間光変調素子、５３は凹面鏡付き光源である。５４は排気ファンであり、５５は排気口である。
【０１０９】
光源５３により照明される空間光変調素子５２に形成された光学像は、レンズ鏡筒５１の投写レンズによって、開口５６を経て筐体５０の外部のフォーカス面（図示せず）に拡大投写される。筐体５０内の空気は、排気ファン５４により、排気口５５を経て排気されることになる。
【０１１０】
レンズ鏡筒５１は、前記実施の形態で示したレンズ鏡筒であり、図１の構成では、温度上昇に対するズームレンズ２０自身のフォーカス位置変動を、補正筒６の光軸方向の熱膨張を利用して、フォーカス位置変動を打ち消すように、ズームレンズ２０を変位させるというものである。このため、温度補正を有効に作用させるためには、ズームレンズ２０の温度と補正筒６の温度との温度差ができるだけ小さいことが望ましい。例えば、ズームレンズ２０の温度に比べ、補正筒６の温度が低いと、補正筒６の光軸方向の熱膨張が小さく、フォーカス位置変動を打ち消すだけの変位をズームレンズ２０に与えられないことも起こり得る。
【０１１１】
より、具体的には、レンズ鏡筒５１を筐体５０から突き出して外部に露出させた場合は、筐体５０内の温度上昇を受け易い後側（筐体５０側）のレンズに比べ、外部の雰囲気の影響を受け易い前側のレンズや補正筒は、温度が低くなる。この場合は、レンズの温度と補正筒の温度との温度差が大きくなり、温度補正効果を有効に発揮させることができない。
【０１１２】
本実施の形態では、レンズ鏡筒５１は、筐体５０内に配置しているので、レンズ鏡筒５１を筐体５０の外に露出させた場合に比べ、レンズの温度と補正筒の温度との温度差を小さくでき、温度補正効果を有効に発揮させることができる。レンズの温度と補正筒の温度との温度差はできるだけ小さいことが理想的であるが、筐体５０内の光源５３や電源回路の配置、出力等により、筐体５０内においても、温度分布が生じることになる。このため、レンズ鏡筒５１のレンズのうち、光源５３に近い後部側の部分と、補正筒との温度差は３度以内となることが好ましい。
【０１１３】
（実施の形態９）
図１１は、実施の形態９に係るプロジェクタの構成図である。図１０と同一構成のものは、同一番号を付している。本実施の形態は、切換え弁５８を備えており、切換え弁５８の開閉により、排気口５９の開閉が可能である。図１０は、切換え弁５９が排気口５９を閉じた状態を示している。また、風路５７が形成されており、光源５３により温度上昇した空気を、排気ファン５４により、レンズ鏡筒５１に導くようにしている。
【０１１４】
ここで、電源投入により、筐体５０内は温度上昇することになるが、レンズの熱容量は大きく、レンズが熱的に安定するまでには、数時間要する場合もある。したがって、フォーカス位置変動が補正され画像が安定するまでは、レンズが熱的安定状態に至るまで待つ必要がある。本実施の形態は、この待ち時間を短縮させるものである。
【０１１５】
図１１の状態では、排気ファン５４からの高温空気は、風路５７を経て鏡筒５１に吹き付けられることになる。このため、鏡筒５１を強制的に加熱でき、レンズが熱的安定状態に至る時間を短縮することができる。レンズが所定温度に達すれば、切換え弁５８を開いて、排気ファン５４からの高温空気は、排気口５９から排気する。
【０１１６】
切換え弁５８の切換えのタイミングは、電源投入から所定時間経過後に切換え弁５８を開く時間制御でもよく、レンズに温度センサを設け温度が設定値になれば、切換え弁５８を開く温度制御でもよい。また、レンズにヒータを埋め込んで、レンズを直接加熱しながら温度制御してもよい。
【０１１７】
（実施の形態１０）
図１２は、実施の形態１０に係るプロジェクタの構成図である。図１０と同一構成のものは、同一番号を付している。本図の構成は、レンズ交換式のプロジェクタを前提としたものである。筐体５０は、レンズのフォーカス機構６０を備えている。フォーカス機構６０は、レンズ鏡筒６１とは別個に独立して設けたものである。フォーカス機構６０により、レンズ鏡筒６１を光軸方向（矢印ａ方向）に移動させることができる。
【０１１８】
フォーカス機構は、レンズ鏡筒に組み込んで設けることもできるが、この場合は、構造が複雑になり、温度補正機構との両立が困難となる。また、レンズ交換式のプロジェクタでは、交換レンズ毎にフォーカス機構を設けていなければならず、コスト面で不利になる。
【０１１９】
これに対して、本実施の形態は、フォーカス機構６０とレンズ鏡筒６１とが別個独立になっているので、フォーカス機構と温度補正機構との両立が容易になる。また、筐体５０にフォーカス機構を設けているので、各交換レンズには、フォーカス機構は不要であり、コスト面でも有利になる。
【０１２０】
また、プロジェクタには、レンズ鏡筒６１を上下、左右に移動させるシフト機構があるので、フォーカス機構はこれに追加すれば容易に設けることができる。
【０１２１】
【発明の効果】
以上のように、本発明のプロジェクタによれば、プロジェクタ内部の照明系によるプロジェクタ内部の温度変化、及び周囲温度の変化に対してフォーカス位置が変動せず、温度変化に関係なく、尖鋭な像が得られ、しかも温度補正効果を有効に発揮させることができる。
【図面の簡単な説明】
【図１】本発明の実施の形態１に係るレンズ鏡筒の断面図
【図２】図１に示したレンズ鏡筒を光軸方向に分解したときの斜視図
【図３】比較例に係るレンズ鏡筒の断面図
【図４】本発明の実施の形態３に係るレンズ鏡筒の断面図
【図５】本発明の実施の形態４に係るレンズ鏡筒の構成図
【図６】本発明の実施の形態５に係るレンズ鏡筒の構成図
【図７】本発明の実施の形態６に係るレンズ鏡筒の構成図
【図８】本発明の実施例１に係るレンズ鏡筒の構成図
【図９】本発明の実施の形態７に係るプロジェクタの構成図
【図１０】本発明の実施の形態８に係るプロジェクタの構成図
【図１１】本発明の実施の形態９に係るプロジェクタの構成図
【図１２】本発明の実施の形態１０に係るプロジェクタの構成図
【符号の説明】
１，２ レンズ、
４ 固定筒
４ａ 直線溝
５，１８ カム環
５ａ，５ｂ カム溝
６，１１，１３ 補正筒
７，８ レンズ枠
７ａ，８ａ 突起
１２ 矯正筒
１４，１５ 締付け筒
２２ ズーム環
５０ 筐体
５１，６１ レンズ鏡筒
５３ 光源
５８ 切換え弁
５９ 排気口[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a projector that enlarges and projects image information of a spatial modulation element on a screen, and more particularly to a projector including a lens barrel having a temperature correction mechanism.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an optical apparatus, a lens and a lens barrel are made of a material with little temperature dependence in order to make a focus position stable with respect to a temperature change without being changed. When plastic is used as a lens material to reduce costs and form an aspherical surface, to stabilize the focus position, the power of the plastic lens can be reduced, or the plastic can be placed in a position that is less affected by temperature changes. It is necessary to dispose the lens or to cancel out the influence of the temperature change with a plurality of plastic lenses.
[0003]
In addition, a product that performs focus adjustment at the start of operation and does not perform focus adjustment thereafter requires temperature characteristics that do not move the focus with respect to temperature changes. For example, the focus of the projector lens is adjusted immediately after the set is turned on, and the focus is not adjusted thereafter. On the other hand, the temperature of the lens rises due to heat from the illumination system inside the set.
[0004]
As a temperature correction type optical apparatus that corrects the variation of the focal position with respect to a temperature change, for example, there is a temperature correction type optical apparatus proposed in Patent Document 1 below. In this temperature correction type optical device, the optical design is devised so as to cancel out the change in the length due to the linear expansion coefficient of the lens barrel material and the change in the focus position of the lens.
[0005]
Further, as a photographing apparatus having a temperature compensation function, there is a photographing apparatus having a temperature compensation function proposed in Patent Document 2 below. This photographing apparatus divides an optical system into two parts by a main body barrel having different linear expansion coefficients, and changes the focus position generated in the lens system by changing the distance between the two divided optical systems depending on the temperature. Is made smaller by changing the lens interval.
[0006]
Further, a temperature-corrected projection television integrated lens is proposed in Patent Document 3 below. In this projection television set lens, the focus position does not fluctuate by changing the interval of a part of the optical system corresponding to the temperature change by using a bar member so as to correct the temperature change. .
[0007]
[Patent Document 1]
JP-A-6-130267
[0008]
[Patent Document 2]
JP-A-6-186466
[0009]
[Patent Document 3]
JP-T-2002-544537
[0010]
[Problems to be solved by the invention]
However, the temperature correction optical device described in Patent Document 1 is effective for a simple optical system such as a collimator, requires a long back focus, and corrects chromatic aberration at a high level. The degree of freedom in lens design is insufficient, making it difficult to design.
[0011]
In addition, since the photographing apparatus described in Patent Document 2 changes the interval of the optical system divided into two parts, it is necessary to perform an optical design so that the aberration does not change, requires a long back focus, and reduces chromatic aberration. For a lens that is to be corrected at a high level, the degree of freedom in designing the lens is insufficient, making it difficult to design. For this reason, the technique described in Patent Document 2 has not provided an effective means for a zoom lens in which a plurality of lens groups move on the optical axis.
In the projection television set lens described in Patent Document 3, since the bar member determines the position of the optical system, it is difficult to suppress the inclination of the optical system to an allowable level or less. Because the optical system interval fluctuates, it is necessary to carry out optical design so that aberrations do not fluctuate. For lenses that require long back focus and correct chromatic aberration at a high level, lens design The degree of freedom is insufficient and the design becomes difficult.
[0012]
For this reason, each of the above-mentioned patent documents does not provide means for temperature correction effective for a zoom lens in which a plurality of lens groups move on the optical axis.
[0013]
Here, a glass lens having a positive power has a reduced power and an increased focal length due to the influence of the inherent linear expansion coefficient (α) of the glass with respect to an increase in temperature. Also, the temperature changes (Δn / ΔT) of the intrinsic refractive index of the glass with respect to the temperature rise, that is, the power changes due to the influence of the refractive index change per unit temperature, and the focal length changes. . In general optical glass, the temperature dependence (Δn / ΔT) of the refractive index has a positive sign, and as the temperature increases, the power increases and the focal length decreases. In this case, the influence of the linear expansion coefficient (α) and the temperature dependence of the refractive index (Δn / ΔT) cancels, and the change in power due to temperature is reduced. Furthermore, in the combination lens, since a lens having a positive power and a lens having a negative power are used in combination, the power change with respect to a temperature change is further reduced. For this reason, the focus variation caused by the interval change due to the linear expansion coefficient of the material constituting the lens barrel becomes more problematic than the focus position variation due to the temperature of the lens itself.
[0014]
On the other hand, in an optical system using plastic as a lens material, the linear expansion coefficient (α) of plastic is larger than that of glass, and the temperature dependency (Δn / ΔT) of the refractive index is negative and the value is negative. Because of its large size compared to glass, focus position fluctuations due to temperature have always been a major problem.
[0015]
In addition, a projector using a reflective spatial modulation element requires a long back focus in order to introduce illumination light and use RGB three-color spatial modulation elements. In order to obtain a long back focus, the lens has a reverse telephoto configuration. That is, a concave lens is predominantly used on the side where the conjugate distance of the lens is long, that is, the screen side, and a positive lens having a large power is predominantly used on the side where the conjugate distance of the lens is short, ie, the spatial modulation element side. Since positive lenses are used at higher axial rays than lenses with short back focus, the effect of positive power is strong. Further, since the curvature of field becomes excessive due to the influence of the concave power, a lens having a low refractive index is often used as the positive lens.
[0016]
When used as a projector lens, telecentricity and small chromatic aberration are required. In the reverse telephoto configuration, the positive lens group on the short conjugate distance side of the lens has a low refractive index, a large Abbe number, and anomalous dispersion characteristics. It is preferable that the glass is made of glass. However, glass with anomalous dispersion characteristics has a relatively large linear expansion coefficient (α), and the sign of temperature dependence of refractive index (Δn / ΔT) is negative as opposed to general optical glass, and the temperature dependence of power. Is big.
[0017]
Therefore, (1) where the on-axis light is high, (2) glass with high positive power, and (3) temperature dependence of the power is high, the focus position fluctuates due to unacceptable temperature as a set. It will happen.
[0018]
In a system using plastic lenses, a material with a large linear expansion coefficient (α) (plastic material) is used for the lens barrel, and the temperature dependence of the focus position of the plastic lens is offset by the temperature dependence of the lens barrel length. Has been done.
However, the above configuration is limited to a simple configuration with a fixed focus. It could not be configured with a zoom lens with a complicated configuration.
[0019]
Since the lens is positioned with a resin component having a large linear expansion coefficient (α), the tilt accuracy with respect to the optical axis required by the zoom lens cannot be maintained. In some cases, the resin focus mechanism and zoom mechanism are not compatible with temperature changes.
[0020]
In the system that adjusts the focus just before use or the system that has an autofocus mechanism, there was no problem even if the focus position fluctuated with temperature.
In projectors, the focus is adjusted immediately after the power is turned on, and after that, the temperature inside the set rises rapidly after the power is turned on due to a powerful lamp and illumination system. .
[0021]
As described above, in an optical system formed of a lens having a long back focus and a small chromatic aberration, it is a new major problem to suppress a change in the focus position with respect to a temperature change.
[0022]
Furthermore, ensuring the prevention of fluctuations in the focus position, shortening the time to stabilize the focus position, and simplifying the lens barrel are also major issues.
[0023]
SUMMARY An advantage of some aspects of the invention is to provide a projector including a lens barrel that can more effectively and reliably prevent a change in focus position with respect to a temperature change.
[0024]
[Means for Solving the Problems]
  In order to achieve the above object, a projector according to the present invention is a projector including a light source and a lens barrel that projects an optical image, and the lens barrel has a focal length of a lens corresponding to a temperature change. The lens barrel is disposed in a housing, and the lens barrel engages with a lens, a lens frame that holds the lens, and the lens frame, A cam ring that determines a position of the lens frame in the optical axis direction, a fixed cylinder that is fixed to the set body, a fixed cylinder that is rotatably engaged with the fixed cylinder around the optical axis, and is fixed to the cam ring; A correction cylinder for determining the position in the optical axis direction, the coefficient of linear expansion of the cam ring and the correction cylinder are different, and in response to a dimensional variation in the optical axis direction due to a temperature change of the correction cylinder, Cam ring in the optical axis directionAnd in the direction to cancel the movement of the focus position due to the temperature change of the lensIt is possible to move.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
  According to the projector of the present invention, the temperature difference between the lens and the lens barrel portion that holds the lens in the lens barrel can be reduced, and the temperature correction effect can be effectively exhibited.In addition, the fluctuation of the focus position of the lens itself with respect to the temperature change is canceled out by the correction mechanism of the lens barrel, so that the change in the optical performance can be suppressed even if the temperature of the lens changes. In other words, the position of the lens on the optical axis can be changed with respect to the temperature change of the lens, and a lens with a small focus position change with respect to the temperature can be obtained.
[0026]
In the projector according to the aspect of the invention, the housing further includes an exhaust port and a switching valve that switches opening and closing of the exhaust port,
Air in the housing is guided to the lens barrel in a state where the switching valve closes the exhaust port, and air in the housing is exhausted in a state where the switching valve opens the exhaust port. Is preferred. According to this configuration, the lens barrel can be forcibly heated, the time for the lens to reach a thermally stable state can be shortened, and the focus adjustment time can be shortened.
[0027]
In addition, it is preferable that a focus adjustment mechanism for adjusting the focus of the lens of the lens barrel is further provided, and the focus adjustment mechanism is disposed in the housing independently of the lens barrel. According to this configuration, since the focus mechanism and the lens barrel are independent of each other, it is easy to achieve both the focus mechanism and the temperature correction mechanism. In addition, since the housing is provided with a focus mechanism, each interchangeable lens does not require a focus mechanism, which is advantageous in terms of cost.
[0029]
  Further, a zoom lens is configured by a lens group held in each of the plurality of lens frames, a cam groove is formed in the cam ring, a linear groove is formed in the fixed cylinder, and the plurality of the Each lens frame is engaged with the cam groove and the linear groove,correctionTube and saidcorrectionEach lens group held by each lens frame moves separately in the direction of the optical axis by the rotation of the cam ring fixed to the cylinder around the optical axis, and when rotating around the optical axis, the cam ring And it is preferable that the said fixed cylinder is being fixed to the optical axis direction. According to this configuration, a zoom lens temperature correction mechanism can be realized.
[0030]
Further, the positions of the plurality of lens frames on the optical axis are determined by the cam ring, and the plurality of lens frames are integrated in response to the dimensional variation in the optical axis direction due to the temperature change of the correction cylinder. Thus, it is preferable to displace in the optical axis direction. According to this configuration, the position of the entire lens group changes as the temperature changes, and the distance between the lens groups does not change, so that it is possible to achieve good focus characteristics, and to distinguish between fixed focus lenses and zoom lenses. Temperature compensation function can be realized.
[0031]
Further, it is preferable that a correction cylinder fitted to the outer periphery of the correction cylinder is further provided, and the linear expansion coefficient of the correction cylinder is smaller than the linear expansion coefficient of the correction cylinder. According to this configuration, the correction cylinder suppresses the radial expansion of the correction cylinder and acts to extend the correction cylinder in the length direction, so that the length of the correction cylinder can be reduced to ensure the extension in the length direction. The lens barrel can be downsized
Further, it is preferable that the correction cylinder and the cam ring are fixed by screwing screws formed on the correction cylinder and the cam ring. According to this configuration, the extension of the correction cylinder due to the temperature change of the lens can be reliably interlocked with the movement of the lens.
[0032]
In addition, a tightening tube is further provided before and after the correction tube in the optical axis direction,
The correction cylinder and the respective fastening cylinders are fixed by screwing screws formed on the correction cylinder and the respective fastening cylinders,
The linear expansion coefficient of each tightening cylinder is substantially the same as the linear expansion coefficient of the cam ring,
The fastening cylinder on the front side and the cam ring are fixed,
It is preferable that the rear fastening cylinder and the fixed cylinder are engaged, and the rear fastening cylinder is rotatable around the optical axis while being fixed in the optical axis direction. According to this configuration, since the linear expansion coefficient of the correction cylinder and the clamping cylinder can be made the same, it is possible to prevent a change in the fitting state between the fixed cylinder and the clamping cylinder due to a temperature change. For this reason, the extension of the correction cylinder due to the temperature change can be linked to the lens more reliably.
[0033]
The front side fastening cylinder and the cam ring are further provided with a fastening member, and the front side fastening cylinder and the fastening member are each formed with a tapered surface, and the tapered surfaces are brought into contact with each other. In this state, it is preferable that the tightening member is fixed to the cam ring by screw tightening. According to this configuration, the cam ring and the fastening cylinder always receive a pulling force, and the coupling state can be maintained even with respect to a temperature change.
[0034]
In addition, a zoom ring that can rotate around the optical axis from the outside is mounted on the outer peripheral surface of the correction cylinder, and the zoom ring and the cam are transmitted so that the force in the rotation direction of the zoom ring is transmitted to the cam ring. An engagement portion with the ring is preferably formed. According to this configuration, since the external force is directly applied to the cam ring, the force applied to the correction cylinder can be suppressed, and the coupling between the correction cylinder and the cam ring becomes uncertain due to the difference in linear expansion coefficient. Even in this case, the cam ring can be reliably rotated. Further, since the force is directly applied to the cam ring, the zoom operation is ensured.
[0035]
In the configuration including the zoom ring, it is preferable that the engaging portion is an engagement of a hole formed in the zoom ring and a protrusion formed in the cam ring. According to this configuration, the engaging portion can be formed with a simple structure.
[0036]
The lens preferably includes a lens made of glass having an Abbe number of 70 or more. According to this configuration, a lens having a long back focus and small chromatic aberration can be obtained. In this case, the glass having an Abbe number of 70 or more has a large linear expansion coefficient (α) and a negative temperature dependency of the refractive index (Δn / ΔT), and the lens itself has a large variation in focus position with respect to the temperature. Since the configuration of the lens barrel of the present invention is provided, fluctuations in the focus position with respect to temperature changes can be suppressed as the entire lens barrel.
[0037]
The lens preferably includes a lens made of glass having a refractive index of 1.5 or less. According to this configuration, a lens having a long back focus and a small curvature of field can be obtained. In this case, the glass having a refractive index of 1.5 or less has a large linear expansion coefficient (α) and a negative temperature dependency (Δn / ΔT) of the refractive index, and the variation of the focus position of the lens itself with respect to the temperature increases. Since the configuration of the lens barrel of the present invention is provided, the entire lens barrel can suppress the variation of the focus position with respect to the temperature change.
[0038]
The lens preferably includes a lens made of glass having a negative temperature dependency coefficient of refractive index. According to this configuration, a lens having a long back focus can be obtained. In this case, the temperature dependence (Δn / ΔT) of the refractive index is negative, and the lens itself has a large variation in the focus position with respect to the temperature. However, since the lens barrel of the present invention is provided, As a whole lens barrel, it is possible to suppress fluctuations in the focus position with respect to temperature changes.
[0039]
Further, if the linear expansion coefficient of the fixed cylinder and the cam ring is α0, and the linear expansion coefficient of the correction cylinder is α1,
1.5 <| (α1-α0) / α0 |
It is preferable to satisfy this relationship. According to this configuration, a change in the focus position due to a temperature change can be suppressed while suppressing the length of the correction cylinder.
[0040]
Further, when the focal length of the entire lens system at normal temperature is f (mm), the length of the correction cylinder is L (mm), and the linear expansion coefficient of the correction cylinder is α,
1 × 10^-3<L × α−6.8 × 10^-Five× f <5 × 10^-3
It is preferable to satisfy this relationship. According to this configuration, the back focus is long, the chromatic aberration is well corrected, and the change in the focus position due to the temperature change can be suppressed.
[0041]
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0042]
(Embodiment 1)
FIG. 1 is a cross-sectional view showing a configuration of a lens barrel according to an embodiment of the present invention. FIG. 2 is a perspective view when the lens barrel shown in FIG. 1 is disassembled in the optical axis direction. Hereinafter, a specific description will be given with reference to FIGS.
[0043]
Although FIG. 1 illustrates an imaging optical system that forms an image of a distant object on an imaging surface as a model, the following description can also be applied to an optical system of a projector. Further, although the zoom optical system having two lens groups has been described, for example, a zoom optical system having three or more groups of three groups or four groups may be used.
[0044]
As shown in FIG. 1, the cam ring 5 is arranged so as to surround the outer peripheral surface of the fixed cylinder 4, and the correction cylinder 6 is arranged so as to surround the outer peripheral surface of the cam ring 5. A zoom lens 20 composed of the lens group 1 and the lens group 2 is arranged on the inner peripheral surface side of the fixed cylinder 4. The lens frame 7 fixes the lens group 1, and the lens frame 8 fixes the lens group 2. The imaging surface of the zoom lens 20 is the imaging surface 3. The fixed cylinder 4 is fixed to the set body 9.
[0045]
As shown in FIGS. 1 and 2, the lens frames 7 and 8 are each provided with three (two in the drawing) projections 7a and 8a so that the circumferential direction is equally divided into three. The fixed cylinder 4 is formed with three straight grooves 4a (two in the drawing) that are three through holes so that the circumferential direction is equally divided into three. The cam ring 5 is formed with three cam grooves 5a (two in the figure) that are through holes and two cam grooves 5b (two in the figure) that are through holes.
[0046]
The three protrusions 7 a integrated with the lens frame 7 are engaged with the linear groove 4 a of the fixed cylinder 4 and the cam groove 5 a of the cam ring 5, respectively. Further, the three protrusions 8 a integral with the lens frame 8 are engaged with the linear groove 4 a of the fixed cylinder 4 and the cam groove 5 b of the cam ring 5, respectively. That is, each protrusion 7a, 7b is engaged with a separate cam groove 5a, 5b.
[0047]
Since the lens frames 7 and 8 are fixed by the fixed cylinder 4 and the cam ring 5, the tilt accuracy of the lens frames 7 and 8 can be suppressed within an allowable limit. Further, since the outer peripheral surface of the fixed cylinder 4 is inserted on the inner peripheral surface side of the cam ring 5, the inclination accuracy of the cam ring 5 can be suppressed within an allowable limit. That is, if the fixed cylinder 4 and the cam ring 5 are formed of a metal material and the machining accuracy is ensured, the correction cylinder 6 has a low machining accuracy or the entire length of the correction cylinder 6 due to uneven temperature in the correction cylinder 6. Even when the elongation is not uniform, the tilt accuracy of the lens can be maintained.
[0048]
It is the cam ring 5 that determines the distance on the optical axis between the lens group 1 and the lens group 2. That is, as described above, the protrusion 7a and the cam groove 5a are engaged, and the protrusion 8a and the cam groove 5b are engaged, whereby the distance on the optical axis between the lens group 1 and the lens group 2 is determined. .
[0049]
It is the correction cylinder 6 that determines the position of the cam ring 5 on the optical axis. A screw 10 is formed at one end of the correction cylinder 6 and the cam ring 5, and the cam ring 5 is fixed to the correction cylinder 6 by screwing of the screw 10. The other end of the correction cylinder 6 is engaged with the groove portion 4a of the fixed cylinder 4 and is fixed in the optical axis direction.
[0050]
An initial focus adjustment is performed by moving the fixed cylinder 4 back and forth in the optical axis direction by a focus mechanism (not shown) on the set main body 9 side, and the focus position coincides with the imaging surface 3.
[0051]
Further, the zoom operation can be performed by rotating the correction cylinder 6 from the outside. By rotating the correction cylinder 6, the cam ring 5 fixed thereto is also rotated. As a result, the lens frames 7 and 8 move to a position where the end of the cam groove of the cam ring 5 and the linear groove of the fixed cylinder 4 coincide, and the lenses 1 and 2 move on the optical axis. Will change the focal length.
[0052]
FIG. 3 shows a configuration diagram of a lens barrel according to a comparative example. In the lens barrel according to the present embodiment shown in FIG. 1, the cam ring 5 is not fixed in the optical axis direction with respect to the fixed cylinder 4, whereas in the configuration of the comparative example shown in FIG. The cam ring 105 is fixed to the fixed cylinder 104 in the optical axis direction.
[0053]
More specifically, in the configuration according to the comparative example of FIG. 3, the cam ring 105 is disposed so as to be sandwiched between the protruding portion 104 a and the protruding portion 104 b that protrude in an annular shape with respect to the outer peripheral surface of the fixed cylinder 104. Yes. For this reason, the cam ring 105 is restricted in position in the optical axis direction with respect to the fixed cylinder 104 both before and after in the optical axis direction, and cannot move in the optical axis direction. The cam ring 105 can be rotated in the rotation direction around the optical axis, and the zoom operation is performed by rotating the cam ring 105 from the outside. During zoom operation, the lens frames 107 and 108 move to a position where the end of the cam groove of the cam ring 105 and the linear groove of the fixed cylinder 104 coincide with each other, and the lenses 101 and 102 move along the optical axis. The focal length of the zoom lens can be changed.
[0054]
Next, the description returns to FIG. When the temperature rises, the focus position of the zoom lens 20 moves in a direction away from the zoom lens 20 with respect to the initial imaging surface. This movement is because the lens power decreases due to the effects of the linear expansion coefficient (α) of the lenses constituting the lens group 1 and the lens group 2 and the temperature dependence (Δn / ΔT) of the refractive index.
[0055]
Due to the thermal expansion due to the temperature rise, the entire length of the correction cylinder 6 in the optical axis direction is extended. Since one end of the correction cylinder 6 is engaged with the groove 4a of the fixed cylinder 4, in this case, of the both ends of the correction cylinder 6 in the optical axis direction, the side opposite to the imaging surface (the opposite side to the imaging surface 3 side). The end of is moved in the direction opposite to the imaging surface. Since the end of the correction cylinder 6 on the side opposite to the imaging surface is fixed to the cam ring 5 by the screw 10, the cam ring 5 is also integrated with the correction cylinder 6 and moves in the direction opposite to the imaging plane. The lens frames 7 and 8 connected to the cam ring 5 via the projections 7a and 7b move in the direction opposite to the imaging surface while maintaining the distance between them. Since the lens groups 1 and 2 are fixed to the lens frames 7 and 8, respectively, the lens groups 1 and 2 move in the direction opposite to the imaging surface while maintaining the distance between them. This action is the same as that when the focus is adjusted, and the focus position of the zoom lens moves in the direction opposite to the imaging surface by the amount of movement of the lens groups 1 and 2.
[0056]
That is, an effect of moving the focus position in a direction away from the zoom lens 20 from the initial imaging surface due to the influence of the linear expansion coefficient (α) of the lens and the temperature dependence (Δn / ΔT) of the refractive index, and the lens groups 1 and 2. However, the action of moving in the direction opposite to the imaging surface while maintaining the distance between the two cancels each other, and the focus position is fixed on the imaging surface 3.
[0057]
In the present embodiment, as described above, the interval between the lens groups 1 and 2 of the zoom lens 20 is determined by the cam ring 5, so that the accuracy of the lens group interval can be maintained. Further, the cam ring 5 moves in the optical axis direction integrally with the correction cylinder 6 due to the temperature rise. However, since the distance between the lens groups is kept constant, what are the constraints on the optical design of the lens? Don't be.
[0058]
As described above, since the focus adjustment moves the entire lens system back and forth on the optical axis, there is little performance deterioration due to the focus. The automatic temperature correction mechanism also has the same effect as the focus, that is, the entire lens system moves integrally with the cam ring 5 in the optical axis direction, so that there is little performance deterioration. The user adjusts the focus in the initial stage of use, and thereafter, the initial focus accuracy is automatically maintained by the automatic temperature correction mechanism.
[0059]
Here, in order for the correction cylinder 6 to exert a temperature correction action, the correction cylinder 6 needs a predetermined correction amount (expansion amount) due to a temperature rise. The correction amount is determined by the product of the length of the correction cylinder 6 and the linear expansion coefficient of the material forming the correction cylinder 6. If the length of the correction cylinder 6 is increased, the correction amount can be ensured, but the length of the correction cylinder 6 is limited by the total length of the lens and the lens barrel configuration. For this reason, it is necessary to increase the linear expansion coefficient in order to ensure the correction amount. In the present embodiment, the linear expansion coefficient of the material of the correction cylinder 6 can be increased as follows.
[0060]
As described above, the tilt accuracy of the lens frames 7 and 8 is determined by the fixed cylinder 4 and the cam ring 5. Accordingly, even when the processing accuracy of the correction cylinder 6 is low, or even when the overall length of the correction cylinder 6 is not uniform due to uneven temperature in the correction cylinder 6, the lens tilt accuracy is ensured. .
[0061]
For this reason, if the fixed cylinder 4 and the cam ring 5 are formed of a metal material and the accuracy is ensured, the correction cylinder 6 can be formed of a resin material whose processing accuracy is inferior to that of the metal material. That is, the degree of freedom in selecting the material of the correction cylinder 6 is increased, and the correction cylinder 6 can be formed of a resin material having a large linear expansion coefficient, so that a predetermined amount of expansion can be obtained.
[0062]
On the other hand, the configuration of the lens barrel according to the comparative example of FIG. 3 does not have a configuration corresponding to the correction cylinder 6 having a large thermal expansion coefficient, and even if the correction cylinder 6 is added to the cam ring 105, the cam ring 105 The position in the optical axis direction is restricted with respect to the fixed cylinder 104 both before and after in the optical axis direction, and cannot move in the optical axis direction.
[0063]
As described above, in the present embodiment, the cam ring 5 is not fixed to the fixed cylinder 4 in the optical axis direction, but the cam ring 5 is fixed to the fixed cylinder 4 at one end in the optical axis direction. The zoom mechanism and the temperature correction mechanism are compatible with each other.
[0064]
In the present embodiment, as described above, the correction cylinder 6 and the cam ring 5 are fixed by screwing of the screws 10. As a result, the correction cylinder 6 and the cam ring 5 are integrally moved on the optical axis, and the extension of the correction cylinder 6 due to the temperature change can be reliably linked to the movement of the lenses 1 and 2. That is, since the linear expansion coefficient is different between the correction cylinder 6 and the cam ring 5, the fitting state changes depending on the temperature, but the contact area can be reduced by fitting the correction cylinder 6 and the cam ring 5 with screws. It can be increased, and a change in the coupling state between the correction cylinder 6 and the cam ring 5 due to temperature change can be prevented.
[0065]
(Embodiment 2)
The second embodiment relates to the relationship between the linear expansion coefficients of the fixed cylinder 4, the cam ring 5, and the correction cylinder 6, the focal length of the entire lens system, and the length of the correction cylinder 6 in the configuration described in the first embodiment. And the relationship between the linear expansion coefficients of the correction cylinder 6.
[0066]
When the linear expansion coefficient of the fixed cylinder 4 and the cam ring 5 is α0 and the linear expansion coefficient of the correction cylinder 6 is α1, it is preferable that the following expression (1) is satisfied.
[0067]
Formula (1) 1.5 <| (α1-α0) / α0 |
Expression (1) defines the relationship between the linear expansion coefficient α0 of the material of the fixed cylinder 4 and the cam ring 5 constituting the lens barrel body and the linear expansion positive number α1 of the material constituting the correction cylinder 6. . By satisfying Expression (1), the total length of the correction cylinder 6 can be suppressed, and the lens barrel can be downsized. If the lower limit is exceeded, it is necessary to increase the total length of the correction cylinder 6 in order to obtain a necessary correction amount, which is disadvantageous for downsizing the lens barrel.
[0068]
A large lower limit criterion is advantageous for downsizing the lens barrel, and preferably satisfies the relationship of the following expression (2).
[0069]
Formula (2) 3.0 <| (α1-α0) / α0 |
In order to realize a smaller lens barrel, it is advantageous in realizing a smaller lens barrel if α1 which is the linear expansion coefficient of the correction cylinder 6 is set to a large value in the above formulas (1) and (2). It becomes. In order to make α1 a large value, the correction cylinder 6 may be made of a resin material. The resin material is disadvantageous compared to the metal material in terms of processing accuracy. However, as described above, since the lens frames 7 and 8 are fixed to the fixed cylinder 4 and the cam ring 5, the tilt accuracy is ensured. This point is not particularly disadvantageous.
[0070]
Further, the length of the correction cylinder 6 is L (mm), the linear expansion coefficient of the material constituting the correction cylinder 6 is α, and the focal length of the entire lens system at normal temperature, that is, the temperature before the temperature rise (for example, 20 degrees) is f ( mm), it is preferable to satisfy the relationship of the following formula (3).
[0071]
Formula (3) 1 × 10^-3<L × α−6.8 × 10^-Five× f <5 × 10^-3
Expression (2) defines the correction amount by the correction cylinder 6 by the focal length of the entire lens system. Expression (2) is a necessary condition for a lens having a long back focus and a high level of chromatic aberration.
[0072]
When the lower limit of Expression (2) is exceeded, focus correction is insufficient for temperature changes, and in the case of a projector, the focus position on the screen surface changes in a direction away from the lens as the temperature rises. When the upper limit is exceeded, the focus correction becomes excessive with respect to the temperature change, and in the case of the projector, the focus position on the screen surface changes in a direction approaching the lens as the temperature rises.
[0073]
(Embodiment 3)
FIG. 4 is a configuration diagram of a lens barrel according to the third embodiment. Components having the same configuration as in FIG. In the configuration of FIG. 4, the cylindrical correction cylinder 12 is disposed so as to be fitted to the outer periphery of the correction cylinder 12. The materials of the correction cylinder 12 and the correction cylinder 11 are selected so that the linear expansion coefficient of the correction cylinder 12 is smaller than the linear expansion coefficient of the correction cylinder 11.
[0074]
Here, the correction amount of the correction cylinder 11 with respect to the temperature change is affected by the linear expansion coefficient of the correction cylinder 11 and the length of the correction cylinder. For this reason, when the correction effect is increased, a material having a large linear expansion coefficient is selected. However, the coefficient of linear expansion is a material-specific characteristic and cannot be selected over a wide range. The length of the correction cylinder 11 is also limited by the physical size of the lens body. In the present embodiment, the correction cylinder 12 is fitted to the outer periphery of the correction cylinder 11, so that the correction effect can be secured even if the length of the correction cylinder 11 is shortened, and the lens barrel is reduced in size. That's it.
[0075]
In the configuration of FIG. 4, the temperature of the correction cylinder 11 and the correction cylinder 12 increases as the ambient temperature increases. As the temperature rises, the correction cylinder 11 and the correction cylinder 12 also expand. Expansion includes radial expansion and optical axis expansion. In the configuration of FIG. 4, the linear expansion coefficient of the correction cylinder 12 is smaller than the linear expansion coefficient of the correction cylinder 11, so that a compressive force is applied to the inner correction cylinder 11 to restrict radial expansion. The correction cylinder 11 expands in the optical axis direction by the amount that the expansion in the radial direction is restricted. That is, the elongation in the optical axis direction with respect to the temperature rise of the correction cylinder 11 is increased by the provision of the correction cylinder 12. For this reason, even if the correction cylinder 11 has a shorter distance, the correction cylinder 12 can compensate for the extension in the optical axis direction, and the lens barrel can be downsized.
[0076]
(Embodiment 4)
FIG. 5 shows a configuration diagram of a lens barrel according to the fourth embodiment. Components having the same configuration as in FIG. Clamping cylinders 14 and 15 are arranged before and after the correction cylinder 13 in the optical axis direction. Threaded portions 16 and 17 are formed at both ends of the correction cylinder 13 and the fastening cylinders 14 and 15. The fastening cylinders 14 and 15 are coupled to both ends of the correction cylinder 13 by screwing the threaded portions 16 and 17.
[0077]
The linear expansion coefficients of the fastening cylinders 14 and 15 are substantially the same as the linear expansion coefficients of the cam ring 18 and the fixed cylinder 4. For example, if the cam ring 18 and the fixed cylinder 4 are made of aluminum, the fastening cylinders 14 and 15 are also made of aluminum. In this case, since the correction cylinder 13 is a resin member having a large linear expansion coefficient, for example, the correction cylinder 13 has a larger linear expansion coefficient than the fastening cylinders 14 and 15.
[0078]
The front clamping cylinder 14 is further coupled to a cam ring 18. Together with the rotation of the correction cylinder 13 around the optical axis, the rear fastening ring 15 rotates around the optical axis with respect to the fixed cylinder 4 in a state of being fixed in the optical axis direction. Since the correction cylinder 13 and the fastening cylinders 14 and 15 having different linear expansion coefficients are screwed together with screws, the contact area is large, and the state of being securely coupled to expansion and contraction is maintained. Moreover, since the correction | amendment cylinder 13 and the fastening cylinders 14 and 15 can be couple | bonded by the clamping | tightening by rotation, an assembly is also easy.
[0079]
Since the linear expansion coefficients of the fastening cylinder 15 and the fixed cylinder 4 are substantially the same, even if the temperature rises, the fitting state of the groove 4a of the fastening cylinder 15 and the fixed cylinder 4 can be prevented. , And can be rotated with respect to the fixed cylinder 4 while being fixed in the optical axis direction.
[0080]
Further, since the linear expansion coefficients of the fastening cylinder 14 and the cam ring 18 are substantially the same, it is possible to prevent the fitting state of the fastening cylinder 14 and the cam ring 18 from changing even if the temperature rises. For this reason, the correction cylinder 13 and the cam ring 18 can move together on the optical axis, and the extension of the correction cylinder 13 due to a temperature change can be reliably interlocked with the lens, and the temperature correction mechanism can be effectively operated. Can do.
[0081]
(Embodiment 5)
The fifth embodiment is an embodiment relating to the coupling between the fastening cylinder 14 and the cam ring 18 in the fourth embodiment. FIG. 6 shows an enlarged view of a connecting portion between the fastening cylinder 14 and the cam ring 18. The fastening cylinder 14 is formed with a tapered portion 14a. The fastening member 19 is a member formed by cutting out from a cylindrical member. The tightening member 19 is formed in a fan shape when viewed from the optical axis direction. A taper portion 19 a is formed on the inner peripheral side of the tightening member 19.
[0082]
In the state of FIG. 6, at one end side of the fastening member 19, the tapered portion 19 a is in contact with the tapered portion 14 a of the fastening cylinder 14, and the other end side is engaged with the groove 18 a of the cam ring 18. By tightening the screw 21 to the cam ring 18, the tightening cylinder 14 can be pulled toward the tip 18 b side of the cam ring 18, and the tightening cylinder 14 can be pressed against the wall surface 18 c of the cam ring 18. The ring 18 can be securely bonded.
[0083]
Further, if the number of the fastening members 19 is increased, the fastening cylinder 14 and the cam ring 18 can be more securely coupled. For example, if the fastening members 19 are arranged in a place that divides the circumferential direction of the fastening cylinder 14 into three equal parts, The fastening cylinder 14 and the cam ring 18 can be reliably coupled without inclination.
[0084]
Normally, when the tightening member and the cam ring are fixed with screws, screw holes are arranged in the tightening member, but due to the looseness of the screws, rattling occurs due to the difference between the screw hole and the outer diameter of the screw. The extension of the correction cylinder cannot be linked to the cam ring by the amount of sticking. In the present embodiment, the taper portion 19a of the tightening member 19 and the taper portion 14a of the tightening tube 14 are in pressure contact with each other, so that the cam ring 18 and the tightening tube 14 always receive a pulling force, and the temperature changes. Even in this case, the coupled state can be maintained.
[0085]
(Embodiment 6)
FIG. 7 shows a configuration diagram of a lens barrel according to the sixth embodiment. The configuration of this figure is a configuration in which a zoom ring 22 is added to the outer periphery of the correction cylinder 13 in the configuration of FIG. 7A is a longitudinal sectional view of the lens barrel according to the present embodiment, and FIG. 7B is a plan view of the main part of the zoom ring 22.
[0086]
The cam ring 18 is formed with a protrusion 18a protruding in the radial direction. A long hole 13 a is formed in the correction cylinder 13, and a long hole 22 a is formed in the zoom ring 22. The protrusion 18a is located at a position corresponding to the long hole 13a and the long hole 22a. The diameter of the long hole 13a and the long hole 22a is larger than the diameter of the protrusion 18a. Further, the zoom ring 22 is only attached to the correction cylinder 13, and the zoom ring 22 and the correction cylinder 13 are not in close contact with or joined to each other.
[0087]
When the zoom ring 22 is rotated from the outside around the optical axis, the protrusion 18a of the cam ring 18 comes into contact with the inner peripheral surface of the elongated hole 22a of the zoom ring 22, and the cam ring 18 is moved while the zoom ring 22 pushes the protrusion 18a. It is rotated around the optical axis (see FIG. 2B). In this case, the correction cylinder 13 also rotates around the optical axis together with the rotation of the cam ring 18.
[0088]
According to the present embodiment, since the external force is directly applied to the cam ring 18, it is possible to suppress the force applied to the correction cylinder 13 and to suppress the loosening of the screws in the threaded portions 16 and 17. Further, even when the coupling between the correction cylinder 13 and the cam ring 18 becomes uncertain due to the difference in the linear expansion coefficient, the cam ring 18 can be reliably rotated. Further, since a force is directly applied to the cam ring 18, the zoom operation is ensured.
[0089]
The zoom ring is not limited to manual operation, and may be rotated by driving with an electric motor. Further, the example in which the zoom ring 22 is attached to the configuration shown in FIG. 5 has been described. However, the present invention is not limited to this, and the zoom ring may be attached to the configuration shown in FIG.
[0090]
Hereinafter, the present invention will be described more specifically with reference to examples.
[0091]
Example 1
FIG. 8 is a configuration diagram of the lens barrel according to the first embodiment. The lens barrel shown in the figure includes a zoom lens having a three-group configuration, and the state shown in the figure shows the wide-angle end. The lens barrel in this figure has a zoom lens with a three-group configuration, but the basic configuration and operation are the same as those of the lens barrel with the zoom lens with a two-group configuration shown in FIGS. is there,
The first lens group is formed by the lenses 31 a and 31 b held by the lens frame 35, and the second lens group is formed by the lenses 32 a, 32 b, 32 c, 32 d and 32 e held by the lens frame 36, and the lens frame 37 is The held lenses 33a, 33b, 33c, 33d, 33e, 33f, 33g, 33h, and 33i form a third lens group. Reference numeral 38 denotes a glass block such as a prism.
[0092]
The lens frames 35, 36, and 37 are inserted in the inner periphery of the fixed cylinder 30 and can move on the optical axis. A straight groove is formed in the fixed cylinder 30, and projections 35 a, 36 a, and 37 a attached to the lens frames 35, 36, and 37 are engaged with the straight groove, and the lens frames 35, 36, and 37 are optically coupled to the fixed cylinder 30. Restricts rotation around the axis.
[0093]
A cam groove is formed in the cam ring 34, and protrusions 35a, 36a, 37a attached to the lens frames 35, 36, 37 are engaged with the cam groove. As a result, the respective intervals at the respective zoom positions of the lens frames 35, 36, and 37 are maintained.
[0094]
Since the correction cylinder 38 is engaged with the groove 30a of the fixed cylinder 30, the correction cylinder 38 is fixed in the optical axis direction. On the other hand, since the cam ring 34 is coupled to the correction cylinder 38 at the tip, the cam ring 34 is also fixed in the optical axis direction.
[0095]
In the zoom operation, the cam ring 34 is rotated by rotating the correction cylinder 38 around the optical axis, and the lens frames 35, 36, and 37 are moved in the optical axis direction. As a result, the first lens group, the second lens group, and the third lens group held in the lens frames 35, 36, and 37 are moved to change the focal length, and the zoom mechanism operates.
[0096]
The zoom lens according to Example 1 has F at the wide-angle end._NO= 2.5, focal length f = 37.08 (mm), half angle of view = 24.2 ° zoom lens, specific numerical values are shown in Table 1 and zoom data are shown in Table 2. In Table 1, ri (mm) is the radius of curvature of each lens surface, and di (mm) is the lens thickness or the inter-lens spacing. In FIG. 8, variable intervals d4, d14, and d33 are shown as representatives.
[0097]
Ni is the refractive index of each lens at the d-line, and νi is the Abbe number of each lens at the d-line. In the example of FIG. 8, r1 to r4 are a first lens group, r5 to r14 are a second lens group, r15 to r33 are a third lens group, and r19 is a stop.
[0098]
[Table 1]

[0099]
[Table 2]

[0100]
The values of the variables in the expressions (1) and (2) and the values of the expressions (1) and (2) are as follows.
[0101]
α0 = 2.3 × 10^-Five
α1 = 1.0 × 10^-Four
L = 50mm
f = 37.08mm
| (Α1-α0) /α0|=3.35
L × α−6.8 × 10^-Five× f = 1.81 × 10^-3
The lenses 32b, 32c, 33c, 33d, 33g, and 33i are anomalous dispersion glass, and the temperature dependency coefficient (Δn / ΔT) of the refractive index is negative, and the change in power with respect to temperature is large. In FIG. 8, the focus position moves to the right in the drawing as the temperature of each lens constituting the zoom lens rises. In the wide-angle end state of this embodiment, the focus position moves 0.0068 mm with respect to a temperature change of 1 degree.
[0102]
Here, the lens frames 35, 36, 37, the fixed cylinder 30, and the cam ring 34 are made of aluminum. The correction cylinder 38 is made of resin, for example, nylon 66 or polyacetal. The linear expansion coefficient of nylon 66 is 1.0 × 10^-FourAnd the linear expansion coefficient of polyacetal is 8.5 × 10^-FiveIt is. These values are 2.3 × 10 of the linear expansion coefficient of aluminum.^-FiveThe elongation per unit length due to temperature rise is also about 4 times.
[0103]
In this embodiment, the correction cylinder 38 is made of nylon 66, and the linear expansion coefficient α1 is 1.0 × 10.^-FourAnd the length L is 50 mm. For this reason, the correction cylinder 51 extends by α1 × L = 0.005 mm with respect to a temperature rise of 1 degree. Therefore, the fluctuation amount of the focus position of 0.0068 mm is corrected by 0.005 mm, and the fluctuation amount of the remaining focus position per degree of temperature is 0.0018 mm / degree.
[0104]
In the set of this example, the temperature of the lens rises by 15 degrees from room temperature after the power is turned on. For example, when the power is turned on at an ambient temperature of 20 degrees, the lens temperature increases by 15 degrees from 20 degrees to 35 degrees. Therefore, at the time of use, the fluctuation amount of the focus position due to the temperature rise is 0.0018 mm / degree × 15 degrees = 0.027 mm, and this value is within the set allowable range. In other words, in the present embodiment, the fluctuation of the focus position due to the temperature change can be suppressed to a small level, and good image quality can be maintained.
[0105]
(Embodiment 7)
FIG. 9 is a configuration diagram of a projector according to Embodiment 7 of the present invention. In FIG. 9, reference numeral 40 denotes the lens barrel shown in the above embodiment, 41 denotes a spatial light modulator for forming an optical image, and 42 denotes a light source with a concave mirror. Reference numeral 43 denotes a focus plane of the projected image. According to the present embodiment, the optical image formed on the spatial light modulator 41 illuminated by the light source 42 is enlarged and projected onto the focus surface 43 by the projection lens of the lens barrel 40.
[0106]
By using the lens shown in the above embodiment as the projection lens of the lens barrel 40, there is a projector that can move the focus surface 43 in the optical axis direction with a change in temperature and obtain a good screen even when the temperature changes. can get.
[0107]
The lens barrel according to the present invention can suppress a change in the focus position with respect to a temperature change and can also be applied to a zoom lens. It is also useful for optical devices such as video cameras, film cameras, and digital cameras.
[0108]
(Embodiment 8)
FIG. 10 is a configuration diagram of a projector according to the eighth embodiment. In FIG. 10, 50 is a housing, 51 is the lens barrel shown in the above embodiment, 52 is a spatial light modulator for forming an optical image, and 53 is a light source with a concave mirror. 54 is an exhaust fan, and 55 is an exhaust port.
[0109]
The optical image formed on the spatial light modulation element 52 illuminated by the light source 53 is enlarged and projected onto a focus surface (not shown) outside the housing 50 through the opening 56 by the projection lens of the lens barrel 51. . The air in the housing 50 is exhausted by the exhaust fan 54 through the exhaust port 55.
[0110]
The lens barrel 51 is the lens barrel shown in the above embodiment, and in the configuration of FIG. 1, the fluctuation of the focus position of the zoom lens 20 itself with respect to the temperature rise is utilized by the thermal expansion in the optical axis direction of the correction barrel 6. Then, the zoom lens 20 is displaced so as to cancel the focus position fluctuation. For this reason, in order to effectively perform the temperature correction, it is desirable that the temperature difference between the temperature of the zoom lens 20 and the temperature of the correction cylinder 6 is as small as possible. For example, when the temperature of the correction cylinder 6 is lower than the temperature of the zoom lens 20, the thermal expansion of the correction cylinder 6 in the optical axis direction is small, and the zoom lens 20 may not be displaced enough to cancel the focus position fluctuation. Can happen.
[0111]
More specifically, when the lens barrel 51 protrudes from the casing 50 and is exposed to the outside, the lens barrel 51 is external as compared to the rear lens (the casing 50 side) that is susceptible to a temperature rise in the casing 50. The temperature of the front lens and the correction cylinder, which are easily affected by the atmosphere, is low. In this case, the temperature difference between the temperature of the lens and the temperature of the correction cylinder becomes large, and the temperature correction effect cannot be exhibited effectively.
[0112]
In the present embodiment, since the lens barrel 51 is disposed in the housing 50, the lens temperature and the correction tube temperature are compared with the case where the lens barrel 51 is exposed outside the housing 50. The temperature difference can be reduced, and the temperature correction effect can be effectively exhibited. Ideally, the temperature difference between the temperature of the lens and the temperature of the correction cylinder is as small as possible. However, due to the arrangement and output of the light source 53 and the power supply circuit in the housing 50, the temperature distribution is also present in the housing 50. Will occur. For this reason, it is preferable that the temperature difference between the rear portion close to the light source 53 in the lens barrel 51 and the correction tube is within 3 degrees.
[0113]
(Embodiment 9)
FIG. 11 is a configuration diagram of a projector according to the ninth embodiment. The same components as those in FIG. 10 are denoted by the same reference numerals. The present embodiment includes a switching valve 58, and the exhaust port 59 can be opened and closed by opening and closing the switching valve 58. FIG. 10 shows a state in which the switching valve 59 closes the exhaust port 59. An air passage 57 is formed so that the air whose temperature has been raised by the light source 53 is guided to the lens barrel 51 by the exhaust fan 54.
[0114]
Here, when the power is turned on, the temperature in the housing 50 rises, but the heat capacity of the lens is large, and it may take several hours for the lens to be thermally stabilized. Therefore, it is necessary to wait until the lens reaches a thermally stable state until the focus position variation is corrected and the image is stabilized. In the present embodiment, this waiting time is shortened.
[0115]
In the state of FIG. 11, the high-temperature air from the exhaust fan 54 is blown to the lens barrel 51 through the air passage 57. For this reason, the lens barrel 51 can be forcibly heated, and the time required for the lens to reach a thermally stable state can be shortened. When the lens reaches a predetermined temperature, the switching valve 58 is opened, and the high-temperature air from the exhaust fan 54 is exhausted from the exhaust port 59.
[0116]
The switching timing of the switching valve 58 may be a time control for opening the switching valve 58 after elapse of a predetermined time from turning on the power, or a temperature control for opening the switching valve 58 if a temperature sensor is provided in the lens and the temperature reaches a set value. Further, a temperature may be controlled while a lens is directly heated by embedding a heater in the lens.
[0117]
(Embodiment 10)
FIG. 12 is a configuration diagram of a projector according to the tenth embodiment. The same components as those in FIG. 10 are given the same numbers. The configuration in this figure is based on a projector with interchangeable lenses. The housing 50 includes a lens focusing mechanism 60. The focus mechanism 60 is provided separately from the lens barrel 61 and independently. By the focus mechanism 60, the lens barrel 61 can be moved in the optical axis direction (arrow a direction).
[0118]
The focus mechanism can be provided by being incorporated in the lens barrel. However, in this case, the structure becomes complicated and it is difficult to achieve compatibility with the temperature correction mechanism. Further, in an interchangeable lens projector, a focus mechanism must be provided for each interchangeable lens, which is disadvantageous in terms of cost.
[0119]
On the other hand, in this embodiment, since the focus mechanism 60 and the lens barrel 61 are separately independent, it is easy to achieve both the focus mechanism and the temperature correction mechanism. Further, since the housing 50 is provided with a focus mechanism, each interchangeable lens does not require a focus mechanism, which is advantageous in terms of cost.
[0120]
Further, since the projector has a shift mechanism for moving the lens barrel 61 up and down, left and right, the focus mechanism can be easily provided by adding to this.
[0121]
【The invention's effect】
As described above, according to the projector of the present invention, the focus position does not fluctuate with respect to the temperature change inside the projector due to the illumination system inside the projector and the change in ambient temperature, and a sharp image can be obtained regardless of the temperature change. In addition, the temperature correction effect can be effectively exhibited.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a lens barrel according to Embodiment 1 of the present invention.
FIG. 2 is a perspective view when the lens barrel shown in FIG. 1 is disassembled in the optical axis direction.
FIG. 3 is a cross-sectional view of a lens barrel according to a comparative example.
FIG. 4 is a cross-sectional view of a lens barrel according to Embodiment 3 of the present invention.
FIG. 5 is a configuration diagram of a lens barrel according to Embodiment 4 of the present invention.
FIG. 6 is a configuration diagram of a lens barrel according to a fifth embodiment of the present invention.
FIG. 7 is a configuration diagram of a lens barrel according to Embodiment 6 of the present invention.
FIG. 8 is a configuration diagram of a lens barrel according to Embodiment 1 of the invention.
FIG. 9 is a configuration diagram of a projector according to a seventh embodiment of the invention.
FIG. 10 is a configuration diagram of a projector according to an eighth embodiment of the invention.
FIG. 11 is a configuration diagram of a projector according to a ninth embodiment of the invention.
FIG. 12 is a configuration diagram of a projector according to a tenth embodiment of the invention.
[Explanation of symbols]
1, 2 lenses,
4 Fixed cylinder
4a Straight groove
5,18 Cam ring
5a, 5b Cam groove
6, 11, 13 Correction cylinder
7,8 Lens frame
7a, 8a protrusion
12 Correction cylinder
14,15 Clamping cylinder
22 Zoom ring
50 cases
51, 61 Lens barrel
53 Light source
58 selector valve
59 Exhaust vent

Claims (6)

A projector comprising a light source and a lens barrel that projects an optical image,
The lens barrel includes a temperature correction mechanism that corrects the focal length of the lens in response to a temperature change,
The lens barrel is disposed in a housing,
The lens barrel is
A lens, a lens frame that holds the lens, a cam ring that engages with the lens frame and determines a position in the optical axis direction of the lens frame, a fixed cylinder that is fixed to the set body, and a rotation around the fixed cylinder and the optical axis And a correction cylinder fixed to the cam ring and determining the position of the cam ring in the optical axis direction,
The cam ring and the correction cylinder have different linear expansion coefficients, and the cam ring corresponds to the optical axis direction variation due to the temperature change of the correction cylinder, and the cam ring depends on the temperature change of the lens. A projector capable of moving in a direction to cancel the movement of the focus position . The housing further includes an exhaust port and a switching valve that switches between opening and closing the exhaust port,
The air in the housing is guided to the lens barrel in a state where the switching valve closes the exhaust port, and the air in the housing is exhausted in a state in which the switching valve opens the exhaust port. Item 14. The projector according to Item 1.   The projector according to claim 1, further comprising a focus adjustment mechanism that adjusts a focus of the lens of the lens barrel, wherein the focus adjustment mechanism is disposed in the housing independently of the lens barrel. A zoom lens is configured with a lens group held in each of the plurality of lens frames,
A cam groove is formed in the cam ring, a linear groove is formed in the fixed cylinder, and each of the plurality of lens frames is engaged with the cam groove and the linear groove,
The lens groups held by the lens frames are individually moved in the optical axis direction by rotation around the optical axis of the correction ring and the cam ring fixed to the correction cylinder,
The projector according to claim 1, wherein the cam ring and the fixed cylinder are fixed in an optical axis direction during rotation around the optical axis.   Each of the plurality of lens frames has a position on the optical axis determined by a cam ring, and the plurality of lens frames are integrated in response to a dimensional variation in the optical axis direction due to a temperature change of the correction cylinder. The projector according to claim 4, wherein the projector is displaced in the optical axis direction.   The projector according to claim 1, further comprising a correction cylinder fitted to an outer periphery of the correction cylinder, wherein the linear expansion coefficient of the correction cylinder is smaller than the linear expansion coefficient of the correction cylinder.

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