JP2004264570A - Projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projector capable of more reliably suppressing the fluctuation of a focal position due to changes in temperatures. <P>SOLUTION: The projector is provided with a light source 53 and a lens barrel 51 for projecting an optical image. The lens barrel 51 is provided with a temperature compensating mechanism of correcting the focal distance of a lens in accordance with the changes in temperatures, and is arranged in a housing. Thus, as for the lens barrel 51, the temperature difference between the lens and the lens barrel part for holding the lens can be reduced, and the projector can effectively exhibit the temperature compensating effect. <P>COPYRIGHT: (C)2004,JPO&NCIPI

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]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a projector for enlarging and projecting image information of a spatial modulation element on a screen, and more particularly to a projector provided with a lens barrel having a temperature correction mechanism.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an optical device, a lens and a lens barrel are made of a material having little temperature dependency in order to stabilize a focus position without a change with respect to a temperature change. When using plastic as a lens material to reduce costs and form an aspheric surface, in order to stabilize the focus position, reduce the power of the plastic lens or use a plastic It is necessary to dispose the lens or to use a plurality of plastic lenses to offset the effect of the temperature change.
[0003]
Further, a product that performs focus adjustment at the start of operation and does not perform focus adjustment thereafter requires a temperature characteristic that the focus does not move particularly in response to a temperature change. For example, the focus of the lens for the projector is adjusted immediately after the set is turned on, and thereafter, the focus is not adjusted. On the other hand, the temperature of the lens rises due to heat from the illumination system inside the set.
[0004]
As a temperature-correcting optical device that corrects a change in the focal position with respect to a temperature change, for example, there is a temperature-correcting optical device proposed in Patent Document 1 below. In this temperature correction type optical device, an optical design is devised so as to cancel a change in length due to a linear expansion coefficient of a lens barrel material and a change in a focus position of a lens.
[0005]
Further, as an imaging device having a temperature compensation function, there is an imaging device having a temperature compensation function proposed in Patent Document 2 below. In this photographing apparatus, the optical system is divided into two parts by main body barrels having different linear expansion coefficients, and the distance between the divided optical systems is changed depending on the temperature, so that the focus position generated in the lens system is changed. Is reduced by changing the lens interval.
[0006]
Further, a temperature-corrected lens for a projection television is proposed in Patent Document 3 below. In this projection television assembly lens, the focus position is not changed by changing the interval of a part of the optical system according to the temperature change by using a bar member so as to compensate for the temperature change. .
[0007]
[Patent Document 1]
JP-A-6-130267
[0008]
[Patent Document 2]
JP-A-6-186466
[0009]
[Patent Document 3]
JP 2002-544537 A
[0010]
[Problems to be solved by the invention]
However, the temperature correction type optical device described in Patent Document 1 is effective for a simple optical system such as a collimator, and requires a long back focus, and is not suitable for a lens that attempts to correct chromatic aberration at a high level. However, the degree of freedom in designing the lens is insufficient, and the design becomes difficult.
[0011]
Further, the photographing device described in Patent Document 2 needs to carry out an optical design so that the aberration does not fluctuate because the interval between the optical systems divided into two fluctuates, 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 lens design is insufficient, and design becomes difficult. For this reason, the technique described in Patent Literature 2 does not provide effective means for a zoom lens in which a plurality of lens groups move on the optical axis.
Further, in the projection television integrated 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 easily allowable level or less. Since the distance between the optical systems fluctuates, it is necessary to design the optical system so that the aberration does not fluctuate. For a lens that requires a long back focus and attempts to correct chromatic aberration at a high level, the lens design is required. The above flexibility is insufficient, and the design becomes difficult.
[0012]
For this reason, each of the above-mentioned patent documents does not provide effective temperature correction means 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 small power and a large focal length due to the influence of a specific linear expansion coefficient (α) of the glass with respect to a rise in temperature. Further, 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 change in the refractive index per unit temperature, and the focal length changes. . In general optical glass, the temperature dependence of the refractive index (Δn / ΔT) has a positive sign, and the power increases and the focal length decreases with increasing temperature. In this case, the effects of the linear expansion coefficient (α) and the temperature dependence of the refractive index (Δn / ΔT) cancel each other, and the change in power due to temperature is reduced. Further, in the assembled lens, since a lens having a positive power and a lens having a negative power are used in combination, a change in power with respect to a temperature change is further reduced. For this reason, the focus variation caused by the change in the interval due to the linear expansion coefficient of the material constituting the lens barrel has become a problem, rather than the variation in the focus position due to the temperature of the lens itself.
[0014]
On the other hand, in an optical system using plastic as a lens material, the coefficient of linear expansion (α) of plastic is larger than that of glass, and the sign of temperature dependence (Δn / ΔT) of the refractive index is negative and the value is negative. Due to the size being larger than glass, the fluctuation of the focus position due to temperature is always a big problem.
[0015]
Further, in a projector using a reflection type spatial modulation element, a long back focus is required for a lens in order to introduce illumination light and use a RGB three-color spatial modulation element. 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, that is, the spatial modulation element side. Since the positive lens is used in a position where the on-axis ray is high as compared with a lens having a short back focus, the effect of the positive power is strong. Further, since the curvature of field becomes excessive due to 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 type configuration, the refractive index is low, the Abbe number is large, and the extraordinary dispersion characteristics are low for the positive lens group on the short side of the conjugate distance of the lens. It is preferable to use a glass having However, glass having anomalous dispersion characteristics has a relatively large coefficient of linear expansion (α), and the sign of the temperature dependence of the refractive index (Δn / ΔT) is negative as opposed to general optical glass, and the temperature dependence of the power. Is big.
[0017]
Therefore, (1) where the on-axis ray is high, (2) glass having a large positive power and (3) high temperature dependence of power is used. Will wake up.
[0018]
In a system using a plastic lens, use a material (plastic material) with a large linear expansion coefficient (α) for the lens barrel, and offset the temperature dependence of the focus position of the plastic lens with the temperature dependence of the length of the lens barrel. Has been done.
However, the above configuration is limited to a simple configuration with a fixed focus. A zoom lens having a complicated configuration could not be configured.
[0019]
Since the positioning of the lens is performed using 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 focus mechanism and the zoom mechanism using resin for the temperature change are not compatible.
[0020]
There was no problem even if the focus position fluctuated with respect to temperature in a system that adjusts the focus immediately before use or a system with an autofocus mechanism.
In a projector, the focus is adjusted immediately after the power is turned on, and since it is not adjusted thereafter, and the temperature inside the set rises rapidly after the power is turned on due to the powerful lamp and illumination system, the focus fluctuation with respect to the temperature change of the lens becomes a big problem. .
[0021]
As described above, in an optical system formed of a lens having a long back focus and a small chromatic aberration, suppressing a change in a focus position with respect to a temperature change is a new major problem.
[0022]
Further, securing the prevention of fluctuation of the focus position, shortening the time required to stabilize the focus position, and simplifying the lens barrel are also important issues.
[0023]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a projector including a lens barrel that can more effectively and reliably prevent a change in a 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,
The lens barrel includes a temperature correction mechanism that corrects a focal length of the lens in response to a temperature change,
The lens barrel is disposed in a housing.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
ADVANTAGE OF THE INVENTION According to the projector of this invention, the temperature difference between a lens and the lens-barrel holding this can be made small among lens barrels, and a temperature correction effect can be exhibited effectively.
[0026]
In the projector according to the aspect of the invention, the casing may further include an exhaust port, and a switching valve configured to switch 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 required for the lens to reach a thermally stable state can be reduced, and the time for focus adjustment can be reduced.
[0027]
Further, it is preferable that the apparatus further comprises a focus adjustment mechanism for adjusting a focus of the lens of the lens barrel, and the focus adjustment mechanism is arranged on the housing independently of the lens barrel. According to this configuration, since the focus mechanism and the lens barrel are separate and independent, it is easy to achieve both the focus mechanism and the temperature correction mechanism. In addition, since the focus mechanism is provided in the housing, each interchangeable lens does not require a focus mechanism, which is advantageous in terms of cost.
[0028]
Further, the lens barrel is
A lens, a lens frame that holds the lens, a cam ring that engages with the lens frame and determines the position of the lens frame in the optical axis direction, a fixed cylinder that is fixed to the set body, and the fixed cylinder that engages with the fixed cylinder. 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 preferably have different coefficients of linear expansion, and the cam ring is preferably movable in the optical axis direction in response to a dimensional change in the optical axis direction due to a temperature change of the correction cylinder. . According to this configuration, the change in the focus position of the lens itself with respect to the temperature change can be canceled by the correction mechanism of the lens barrel, and the change in the optical performance can be suppressed even when the temperature of the lens changes. That is, the position on the optical axis of the lens can be changed with respect to a change in the temperature of the lens, and a lens with a small focus position change with respect to the temperature can be obtained.
[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 straight groove is formed in the fixed cylinder, and each of the plurality of lens frames is engaged with the cam groove and the straight groove.
By the rotation of the fixed cylinder and the cam ring fixed to the fixed cylinder around the optical axis, the lens groups held by the lens frames individually move in the optical axis direction,
When rotating around the optical axis, it is preferable that the cam ring and the fixed cylinder are fixed in the optical axis direction. According to this configuration, a temperature correction mechanism of the zoom lens can be realized.
[0030]
Further, the positions of the plurality of lens frames on the optical axis are determined by a cam ring, and the plurality of lens frames are integrally formed in response to a dimensional change in the optical axis direction due to a temperature change of the correction cylinder. It is preferable to displace in the optical axis direction. According to this configuration, since the positions of all the lens units change integrally with respect to the temperature change and the distance between the lens units does not change, good focus characteristics can be realized, and the fixed focus lens and the zoom lens can be distinguished. And a temperature correction function can be realized.
[0031]
Preferably, the correction cylinder further includes a correction cylinder fitted to an outer periphery of the correction cylinder, and a linear expansion coefficient of the correction cylinder is preferably smaller than a linear expansion coefficient of the correction cylinder. According to this configuration, the correction cylinder suppresses radial expansion of the correction cylinder and acts to extend the correction cylinder in the length direction. Therefore, the length of the correction cylinder can be reduced to secure the elongation in the length direction. , Miniaturization of lens barrel
In addition, it is preferable that the correction cylinder and the cam ring are fixed by screwing a screw 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 linked to the movement of the lens.
[0032]
Further, before and after in the optical axis direction of the correction cylinder, further provided with a tightening cylinder,
The correction cylinder and the tightening cylinders are fixed by screwing of the screws formed on the correction cylinder and the tightening cylinders,
The linear expansion coefficient of each of the tightening cylinders is substantially the same as the linear expansion coefficient of the cam ring,
The tightening cylinder and the cam ring on the front side are fixed,
It is preferable that the rear-side tightening cylinder and the fixed cylinder are engaged with each other, and the rear-side tightening cylinder is rotatable around the optical axis while being fixed in the optical axis direction. According to this configuration, the linear expansion coefficient between the correction cylinder and the tightening cylinder can be made the same, so that a change in the fitting state between the fixed cylinder and the tightening cylinder due to a temperature change can be prevented. For this reason, the extension of the correction cylinder due to the temperature change can be more reliably linked to the lens.
[0033]
Further, the apparatus further includes a tightening member for fixing the front-side tightening cylinder and the cam ring, wherein the front-side tightening cylinder and the tightening 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 tightening a screw. According to this configuration, the cam ring and the tightening cylinder always receive a pulling force, so that the coupled state can be maintained even when the temperature changes.
[0034]
A zoom ring rotatable 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 arranged so that a force in the rotation direction of the zoom ring is transmitted to the cam ring. It is preferable that an engagement portion with the ring is formed. According to this configuration, since an 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 a difference in linear expansion coefficient. Even in this case, the cam ring can be reliably rotated. Further, since a 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 formed by engaging a hole formed in the zoom ring with a projection formed on the cam ring. According to this configuration, the engaging portion can be formed with a simple structure.
[0036]
Preferably, the lens 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 a small chromatic aberration can be obtained. In this case, glass having an Abbe number of 70 or more has a large linear expansion coefficient (α) and a negative temperature dependence of the refractive index (Δn / ΔT), and the focus position of the lens itself greatly changes with temperature. Since the lens barrel of the present invention has the configuration, it is possible to suppress a change in the focus position with respect to a temperature change as a whole of the lens barrel.
[0037]
Preferably, the lens 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 field curvature can be obtained. In this case, 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 focus position of the lens itself greatly changes with temperature. In addition, since the lens barrel of the present invention has the configuration of the lens barrel, it is possible to suppress a change in the focus position with respect to a temperature change as a whole of the lens barrel.
[0038]
Further, it is preferable that the lens includes a lens made of glass having a negative temperature dependence coefficient of refractive index. According to this configuration, a lens having a long back focus can be obtained. In this case, the temperature dependence of the refractive index (Δn / ΔT) is negative, and the focus position of the lens itself fluctuates greatly with respect to the temperature. However, since the lens itself has the configuration of the lens barrel of the present invention, The fluctuation of the focus position with respect to the temperature change can be suppressed for the entire lens barrel.
[0039]
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 |
Is preferably satisfied. According to this configuration, a change in the focus position due to a temperature change can be suppressed while the length of the correction cylinder is suppressed.
[0040]
Further, if the focal length of the entire lens system at room 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^-5× f <5 × 10^-3
Is preferably satisfied. According to this configuration, the back focus is long, the chromatic aberration is well corrected, and the change of the focus position due to the temperature change is suppressed.
[0041]
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0042]
(Embodiment 1)
FIG. 1 is a 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]
FIG. 1 illustrates an imaging optical system that forms an image of a distant object on an imaging surface as a model, but the following description can also be applied to an optical system of a projector. Although the zoom optical system has two lens groups, the zoom optical system may include, for example, three or four zoom optical systems.
[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 a lens group 1 and a 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 provided with three (two in the illustration) projections 7a and 8a, respectively, so as to divide the circumferential direction into three equal parts. The fixed cylinder 4 is formed with three straight grooves 4a (two shown in the figure) as three through holes so as to divide the circumferential direction into three equal parts. Further, the cam ring 5 is formed with three cam grooves 5a (two shown), which are three through holes, and three cam grooves 5b (two shown), which are three through holes.
[0046]
The three projections 7a integral with the lens frame 7 are engaged with the straight groove 4a of the fixed cylinder 4 and the cam groove 5a of the cam ring 5, respectively. The three projections 8a integral with the lens frame 8 are engaged with the straight groove 4a of the fixed cylinder 4 and the cam groove 5b of the cam ring 5, respectively. That is, the projections 7a and 7b are engaged with the separate cam grooves 5a and 5b, respectively.
[0047]
Since the lens frames 7 and 8 are fixed by the fixed cylinder 4 and the cam ring 5, the inclination 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 to within an allowable limit. That is, if the fixed cylinder 4 and the cam ring 5 are formed of a metal material and the processing accuracy is ensured, the processing accuracy of the correction cylinder 6 is low, 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 inclination accuracy of the lens can be maintained.
[0048]
It is the cam ring 5 that determines the distance between the lens groups 1 and 2 on the optical axis. That is, as described above, the protrusion 7a engages with the cam groove 5a, and the protrusion 8a engages with the cam groove 5b, so that the distance between the lens group 1 and the lens group 2 on the optical axis 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 the screw 10. The other end of the correction barrel 6 is engaged with the groove 4a of the fixed barrel 4, and is fixed in the optical axis direction.
[0050]
By moving the fixed cylinder 4 back and forth in the optical axis direction by a focus mechanism (not shown) on the set body 9 side, initial focus adjustment is performed, 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 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, the lenses 1 and 2 move on the optical axis, and the zoom lens moves to a position where the end of the cam groove of the cam ring 5 and the straight groove of the fixed cylinder 4 coincide with each other. Will change.
[0052]
Here, 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 to the fixed barrel 4 in the optical axis direction, whereas in the configuration of the comparative example shown in FIG. A cam ring 105 is fixed to the fixed barrel 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 projecting portion 104 a and the projecting portion 104 b projecting annularly with respect to the outer peripheral surface of the fixed cylinder 104. I have. For this reason, the position of the cam ring 105 in the optical axis direction with respect to the fixed cylinder 104 in both the front and rear directions in the optical axis direction is restricted, and the cam ring 105 cannot move in the optical axis direction. The cam ring 105 is rotatable in a rotation direction around the optical axis, and performs a zoom operation by rotating the cam ring 105 from outside. During the 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 straight groove of the fixed cylinder 104 coincide with each other, and accordingly the lenses 101 and 102 move on the optical axis. To change the focal length of the zoom lens.
[0054]
Next, the description returns to FIG. When the temperature rises, the focus position of the zoom lens 20 moves away from the zoom lens 20 with respect to the initial imaging plane. This movement is because the power of the lens decreases due to the effects of the linear expansion coefficient (α) of the lenses constituting the lens groups 1 and 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 barrel 6 is engaged with the groove 4a of the fixed barrel 4, in this case, of the two ends of the correction barrel 6 in the optical axis direction, the side opposite to the imaging surface (the side opposite to the imaging surface 3 side). Moves in the direction opposite to the imaging plane. Since the end portion of the correction cylinder 6 on the side opposite to the imaging surface is fixed to the cam ring 5 with the screw 10, the cam ring 5 also moves in the direction opposite to the imaging surface together with the correction cylinder 6. The lens frames 7, 8 connected to the cam ring 5 via the projections 7a, 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 operation is the same as the operation of adjusting the focus, and the focus position of the zoom lens moves in the direction opposite to the imaging plane by the amount that the lens groups 1 and 2 have moved.
[0056]
That is, the effect that the focus position moves in the 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 of the refractive index (Δn / ΔT); And the action of moving in the direction opposite to the imaging surface while maintaining the distance therebetween cancels each other, so that the focus position is fixed on the imaging surface 3.
[0057]
In the present embodiment, as described above, since the interval between the lens groups 1 and 2 of the zoom lens 20 is determined by the cam ring 5, 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 maintained at a constant distance, there is a constraint in the optical design of the lens. No.
[0058]
As described above, since the focus adjustment moves the entire lens system back and forth on the optical axis, performance degradation due to focus is small. The automatic temperature correction mechanism also has the same effect as the focus, that is, the entire lens system moves in the optical axis direction integrally with the cam ring 5, so that the performance deterioration is small. The user adjusts the focus in the early 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 exhibit the 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 coefficient of linear expansion of the material forming the correction cylinder 6. If the length of the correction barrel 6 is increased, the correction amount can be secured, but the length of the correction barrel 6 is limited by the overall length of the lens and the lens barrel configuration. For this reason, it is necessary to increase the linear expansion coefficient to secure the correction amount. In the present embodiment, it is possible to increase the linear expansion coefficient of the material of the correction cylinder 6 as described below.
[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. Therefore, even when the processing accuracy of the correction cylinder 6 is low, or when the entire length of the correction cylinder 6 is non-uniformly elongated due to non-uniform temperature in the correction cylinder 6, the inclination accuracy of the lens can be 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 secured, the correction cylinder 6 can be formed of a resin material having a lower processing accuracy than 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, in the configuration of the lens barrel according to the comparative example of FIG. 3 described above, there is no 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, In the optical axis direction, the position in the optical axis direction with respect to the fixed cylinder 104 is regulated 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, and the cam ring 5 is fixed to the fixed cylinder 4 at one end in the optical axis direction. To achieve both a zoom mechanism and a temperature correction mechanism.
[0064]
In the present embodiment, as described above, the correction cylinder 6 and the cam ring 5 are fixed by screwing the screws 10 together. Accordingly, the correction cylinder 6 and the cam ring 5 move integrally on the optical axis, and the extension of the correction cylinder 6 due to a 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. However, the fitting area is changed by fitting the correction cylinder 6 and the cam ring 5 with screws. This can prevent the change in the coupling state between the correction cylinder 6 and the cam ring 5 due to the temperature change.
[0065]
(Embodiment 2)
In the second embodiment, the configuration described in the first embodiment relates to the relationship between the linear expansion coefficient 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. And the linear expansion coefficient of the correction cylinder 6.
[0066]
Assuming that 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 |
Equation (1) defines the relationship between the linear expansion coefficient α0 of the material of the fixed barrel 4 and the cam ring 5 constituting the lens barrel body and the positive linear expansion α1 of the material of the correction barrel 6. . By satisfying the expression (1), the total length of the correction barrel 6 can be reduced, and the size of the lens barrel can be reduced. If the lower limit is exceeded, it is necessary to increase the overall length of the correction barrel 6 in order to obtain a necessary correction amount, which is disadvantageous for downsizing the lens barrel.
[0068]
When the lower limit value is large, it is advantageous for downsizing of the lens barrel, and it is preferable that the following expression (2) is satisfied.
[0069]
Formula (2) 3.0 <| (α1−α0) / α0 |
In order to realize a smaller lens barrel, it is advantageous to realize a smaller lens barrel by setting α1 which is the linear expansion coefficient of the correction barrel 6 to a large value in the above equations (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 in terms of processing accuracy as compared with the metal material. However, as described above, since the lens frames 7 and 8 are fixed to the fixed cylinder 4 and the cam ring 5, the inclination accuracy is secured. This is not particularly disadvantageous.
[0070]
The length of the correction cylinder 6 is L (mm), the coefficient of linear expansion of the material forming 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 following expression (3).
[0071]
Formula (3) 1 × 10^-3<L × α−6.8 × 10^-5× f <5 × 10^-3
Equation (2) defines the correction amount by the correction cylinder 6 based on the focal length of the entire lens system. Equation (2) is a condition necessary for a lens having a long back focus and satisfying chromatic aberration at a high level.
[0072]
If the lower limit of the expression (2) is exceeded, the correction of the focus for the temperature change is insufficient, 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. If the temperature exceeds the upper limit, the focus is excessively corrected for the temperature change, and in the case of a projector, the focus position on the screen surface changes in a direction approaching the lens as the temperature rises.
[0073]
(Embodiment 3)
FIG. 4 shows a configuration diagram of a lens barrel according to the third embodiment. Components having the same configuration as in FIG. 1 are denoted by the same reference numerals and description thereof is omitted. In the configuration of FIG. 4, the cylindrical correction cylinder 12 is arranged so as to fit on the outer circumference of the correction cylinder 12. Each material of the correction cylinder 12 and the correction cylinder 11 is 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. Therefore, when increasing the correction effect, a material having a large linear expansion coefficient is selected. However, the coefficient of linear expansion is a characteristic inherent to the material and cannot be selected over a wide range. The length of the correction cylinder 11 is also limited due to restrictions on the physical size of the lens body. In the present embodiment, the correction barrel 12 is fitted to the outer circumference of the correction barrel 11 so that the correction effect can be secured even if the length of the correction barrel 11 is shortened, and the lens barrel is downsized. That is.
[0075]
In the configuration shown in FIG. 4, the temperatures of the correction cylinder 11 and the correction cylinder 12 increase as the ambient temperature increases. As the temperature increases, the correction cylinder 11 and the correction cylinder 12 also expand. The expansion includes radial expansion and optical axis expansion. In the configuration of FIG. 4, since the linear expansion coefficient of the correction cylinder 12 is smaller than the linear expansion coefficient of the correction cylinder 11, a compressive force is applied to the inner correction cylinder 11, so that radial expansion is restricted. The correction cylinder 11 expands in the optical axis direction by an amount corresponding to the restriction on the radial expansion. That is, the extension of the correction cylinder 11 in the optical axis direction with respect to the temperature rise is increased by the provision of the correction cylinder 12. For this reason, even if the correction cylinder 11 has a shorter distance, the expansion in the optical axis direction can be compensated for by the correction cylinder 12, 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. 1 are denoted by the same reference numerals and description thereof is omitted. Tightening 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 tightening cylinders 14 and 15. The fastening cylinders 14 and 15 are connected to both ends of the correction cylinder 13 by screwing the threaded portions 16 and 17 together.
[0077]
The linear expansion coefficients of the tightening 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, 15 are also made of aluminum. In this case, since the correction cylinder 13 is, for example, a resin member having a large linear expansion coefficient, the correction cylinder 13 has a larger linear expansion coefficient than the fastening cylinders 14 and 15.
[0078]
The front tightening cylinder 14 is further connected to a cam ring 18. Together with the rotation of the correction barrel 13 around the optical axis, the rear tightening ring 15 rotates around the optical axis with respect to the fixed barrel 4 while being fixed in the optical axis direction. Since the correction cylinder 13 and the tightening 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 connected to expansion and contraction is maintained. In addition, since the coupling between the correction cylinder 13 and the clamping cylinders 14 and 15 can be performed by tightening by rotation, assembly is easy.
[0079]
Since the linear expansion coefficients of the tightening cylinder 15 and the fixed cylinder 4 are substantially the same, even if the temperature rises, a change in the fitting state of the groove 4a of the tightening cylinder 15 and the fixed cylinder 4 can be prevented. It 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 tightening cylinder 14 and the cam ring 18 are substantially the same, a change in the fitting state of the tightening cylinder 14 and the cam ring 18 can be prevented even when the temperature rises. For this reason, the correction cylinder 13 and the cam ring 18 can move integrally on the optical axis, the expansion of the correction cylinder 13 due to a temperature change can be reliably linked to the lens, and the temperature correction mechanism can be effectively operated. Can be.
[0081]
(Embodiment 5)
The fifth embodiment is an embodiment relating to the connection between the tightening cylinder 14 and the cam ring 18 in the fourth embodiment. FIG. 6 is an enlarged view of a connecting portion between the tightening cylinder 14 and the cam ring 18. The tightening cylinder 14 is formed with a tapered portion 14a. The fastening member 19 is a member cut out from a cylindrical member. The fastening member 19 is formed in a fan shape when viewed from the optical axis direction. A tapered portion 19 a is formed on the inner peripheral side of the fastening member 19.
[0082]
In the state of FIG. 6, one end of the tightening member 19 has a tapered portion 19 a in contact with the tapered portion 14 a of the tightening cylinder 14, and the other end 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 into 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, and the tightening cylinder 14 and the cam The ring 18 can be securely bonded.
[0083]
Further, if the number of the tightening members 19 is increased, the connection between the tightening cylinder 14 and the cam ring 18 becomes more reliable. For example, if the tightening members 19 are arranged at a place where the circumferential direction of the tightening cylinder 14 is divided into three equal parts, The tightening cylinder 14 and the cam ring 18 can be securely connected without inclination.
[0084]
Normally, when the tightening member and the cam ring are fixed with a screw, a screw hole is arranged in the tightening member, but looseness of the screw causes rattling due to a difference between the screw hole and the screw outer diameter. The extension of the correction cylinder cannot be linked to the cam ring by the amount of the attachment. In the present embodiment, the cam ring 18 and the tightening cylinder 14 always receive a pulling force due to the taper 19a of the tightening member 19 and the taper 14a of the tightening cylinder 14 being pressed against each other. Even in this case, the connected state can be maintained.
[0085]
(Embodiment 6)
FIG. 7 shows a configuration diagram of a lens barrel according to Embodiment 6. The configuration of this drawing 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. FIG. 7A is a longitudinal sectional view of the lens barrel according to the present embodiment, and FIG. 7B is a plan view of a main part of the zoom ring 22.
[0086]
The cam ring 18 has a projection 18a projecting in the radial direction. The correction cylinder 13 has an elongated hole 13a, and the zoom ring 22 has an elongated hole 22a. The projection 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 projection 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 or joined.
[0087]
When the zoom ring 22 is rotated from the outside around the optical axis, the projection 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 zoom ring 22 pushes the projection 18a while pressing the cam ring 18. It is rotated around the optical axis (see FIG. 2B). In this case, the correction cylinder 13 also rotates around the optical axis integrally with the rotation of the cam ring 18.
[0088]
According to the present embodiment, since an external force is directly applied to the cam ring 18, the force applied to the correction cylinder 13 can be suppressed, and the loosening of the threaded portions 16, 17 can be suppressed. Further, even when the coupling between the correction cylinder 13 and the cam ring 18 becomes uncertain due to a difference in linear expansion coefficient, the cam ring 18 can be surely rotated. Further, since a force is directly applied to the cam ring 18, the zoom operation is ensured.
[0089]
The zoom ring may be rotated not only manually but also by driving with an electric motor. In addition, the example in which the zoom ring 22 is mounted on the configuration illustrated in FIG. 5 has been described. However, the configuration is not limited to this, and the zoom ring may be mounted on the configuration illustrated 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 this figure includes a three-group zoom lens, and the state in this figure shows the wide-angle end. Although the lens barrel of this figure includes a three-group zoom lens, the basic configuration and operation are the same as those of the lens barrel including the two-group zoom lens shown in FIGS. is there,
A first lens group is formed by the lenses 31a and 31b held by the lens frame 35, and a second lens group is formed by the lenses 32a, 32b, 32c, 32d, and 32e held by the lens frame 36. The held lenses 33a, 33b, 33c, 33d, 33e, 33f, 33g, 33h, and 33i form a third lens group. 38 is a glass block such as a prism.
[0092]
The lens frames 35, 36, and 37 are mounted on the inner periphery of the fixed cylinder 30, and can move on the optical axis. A straight groove is formed in the fixed barrel 30, and the projections 35 a, 36 a, 37 a attached to the lens frames 35, 36, 37 fit into the straight groove, and the lens frames 35, 36, 37 are illuminated with respect to the fixed barrel 30. Restricts rotation around the axis.
[0093]
A cam groove is formed in the cam ring 34, and projections 35a, 36a, and 37a attached to the lens frames 35, 36, and 37 are engaged with the cam groove. As a result, the respective intervals of the lens frames 35, 36, and 37 at the respective zoom positions 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 connected to the correction cylinder 38 at the distal end, 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 by the lens frames 35, 36, and 37 respectively move to change the focal length, and the zoom mechanism operates.
[0096]
The zoom lens according to the first embodiment has a wide-angle F_NO= 2.5, focal length f = 37.08 (mm), half angle of view = 24.2 °, 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 distance between lenses. FIG. 8 shows the variable intervals d4, d14, and d33 as representatives.
[0097]
Also, 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 first lens groups, r5 to r14 are second lens groups, r15 to r33 are third lens groups, 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 in the expressions (1) and (2) are as follows.
[0101]
α0 = 2.3 × 10^-5
α1 = 1.0 × 10^-4
L = 50mm
f = 37.08 mm
| (Α1−α0) /α0|=3.35
L × α-6.8 × 10^-5× f = 1.81 × 10^-3
The lenses 32b, 32c, 33c, 33d, 33g, and 33i are anomalous dispersion glass, have a negative temperature-dependent coefficient of refractive index (Δn / ΔT), and have a large power change with temperature. In FIG. 8, the focus position moves rightward as viewed in the drawing due to the temperature rise of each lens constituting the zoom lens. In the state at the wide-angle end in the present embodiment, the focus position moves by 0.0068 mm for a temperature change of 1 degree.
[0102]
Here, the lens frames 35, 36, 37, the fixed cylinder 30, and the cam ring 34 are formed of aluminum. The correction cylinder 38 is formed of a resin, for example, nylon 66 or polyacetal. The coefficient of linear expansion of nylon 66 is 1.0 × 10^-4And the linear expansion coefficient of polyacetal is 8.5 × 10^-5It is. These values are 2.3 × 10 times the linear expansion coefficient of aluminum.^-5, And the elongation per unit length due to the temperature rise is also about four times.
[0103]
In this embodiment, the correction cylinder 38 is formed of nylon 66, and the linear expansion coefficient α1 is 1.0 × 10^-4And the length L is 50 mm. Therefore, for one degree of temperature rise, the correction cylinder 51 is extended by α1 × L = 0.005 mm. 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 1 degree of temperature is 0.0018 mm / degree.
[0104]
In the set of this embodiment, the temperature of the lens rises by 15 degrees from normal 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, during use, the fluctuation amount of the focus position due to the temperature rise is 0.0018 mm / degree × 15 degrees = 0.027 mm, which is within the allowable range of the set. That is, in the present embodiment, a change in the focus position due to a temperature change can be suppressed to a small value, 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 described 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 surface 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 on the focus surface 43 by the projection lens of the lens barrel 40.
[0106]
By using the lens described in the above embodiment as the projection lens of the lens barrel 40, there is a projector in which the movement of the focus surface 43 in the optical axis direction due to the temperature change is small, and a good screen can be obtained even when the temperature changes. can get.
[0107]
It should be noted that the lens barrel according to the present invention can suppress the change of the focus position with respect to the temperature change, and can correspond to the zoom lens. It is also useful for forming 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 modulator 52 illuminated by the light source 53 is enlarged and projected by the projection lens of the lens barrel 51 onto a focus surface (not shown) outside the housing 50 via the opening 56. . 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 described in the above embodiment. In the configuration of FIG. 1, a change in the focus position of the zoom lens 20 itself due to a temperature rise is used, and a thermal expansion of the correction barrel 6 in the optical axis direction is used. Then, the zoom lens 20 is displaced so as to cancel the focus position fluctuation. Therefore, in order to make the temperature correction work effectively, 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 displacement sufficient to cancel the focus position fluctuation may not be given to the zoom lens 20. It can happen.
[0111]
More specifically, when the lens barrel 51 protrudes from the housing 50 and is exposed to the outside, the lens barrel 51 is more externally exposed than the rear (housing 50 side) lens which is susceptible to a temperature rise in the housing 50. The temperature of the front lens and the correction cylinder, which are easily affected by the atmosphere, becomes 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 effectively exhibited.
[0112]
In the present embodiment, since the lens barrel 51 is disposed inside the housing 50, the temperature of the lens and the temperature of the correction barrel are lower than when the lens barrel 51 is exposed outside the housing 50. 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, output, and the like of the light source 53 and the power supply circuit in the housing 50, the temperature distribution can be reduced even in the housing 50. Will happen. For this reason, it is preferable that the temperature difference between the portion of the lens of the lens barrel 51 on the rear side near the light source 53 and the correction barrel be within 3 degrees.
[0113]
(Embodiment 9)
FIG. 11 is a configuration diagram of a projector according to the ninth embodiment. Components having the same configuration as in FIG. 10 are denoted by the same reference numerals. In the present embodiment, the switching valve 58 is provided, 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. Further, an air passage 57 is formed, and air whose temperature is increased 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 inside the housing 50 rises, but the heat capacity of the lens is large, and it may take several hours until the lens is thermally stabilized. Therefore, it is necessary to wait until the lens reaches a thermally stable state until the focus position fluctuation is corrected and the image is stabilized. In the present embodiment, the waiting time is reduced.
[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 reduced. 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 time control for opening the switching valve 58 after a predetermined time has elapsed since power-on, or temperature control for opening the switching valve 58 when a temperature sensor is provided on the lens and the temperature reaches a set value. Further, a heater may be embedded in the lens, and the temperature may be controlled while directly heating the lens.
[0117]
(Embodiment 10)
FIG. 12 is a configuration diagram of a projector according to the tenth embodiment. Components having the same configuration as in FIG. 10 are denoted by the same reference numerals. The configuration in this figure is based on the assumption that a lens-interchangeable projector is used. The housing 50 has a lens focusing mechanism 60. The focus mechanism 60 is provided separately and independently of the lens barrel 61. By the focus mechanism 60, the lens barrel 61 can be moved in the optical axis direction (the direction of arrow a).
[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 a lens-interchangeable projector, a focus mechanism must be provided for each interchangeable lens, which is disadvantageous in terms of cost.
[0119]
On the other hand, in the present embodiment, since the focus mechanism 60 and the lens barrel 61 are separate and independent, it is easy to achieve both the focus mechanism and the temperature correction mechanism. In addition, since a focusing mechanism is provided in the housing 50, no focusing mechanism is required for each interchangeable lens, 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 and left and right, a focus mechanism can be easily provided by adding it to the shift mechanism.
[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 changes in the temperature inside the projector due to the illumination system inside the projector and changes in the ambient temperature, and a sharp image is obtained regardless of the temperature change. Thus, the temperature correction effect can be effectively exhibited.
[Brief description of the drawings]
FIG. 1 is a 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 an optical axis direction.
FIG. 3 is a sectional view of a lens barrel according to a comparative example.
FIG. 4 is a 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 Embodiment 5 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 the first embodiment of the present invention.
FIG. 9 is a configuration diagram of a projector according to a seventh embodiment of the present invention.
FIG. 10 is a configuration diagram of a projector according to Embodiment 8 of the present invention.
FIG. 11 is a configuration diagram of a projector according to a ninth embodiment of the present invention.
FIG. 12 is a configuration diagram of a projector according to a tenth embodiment of the present invention.
[Explanation of symbols]
1,2 lens,
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 straightening cylinder
14,15 Tightening cylinder
22 Zoom ring
50 case
51, 61 lens barrel
53 light source
58 Switching valve
59 Exhaust port

Claims (7)

A projector including a light source and a lens barrel that projects an optical image,
The lens barrel includes a temperature correction mechanism that corrects a focal length of the lens in response to a temperature change,
The projector, wherein the lens barrel is disposed inside a housing. The housing further includes an exhaust port, and a switching valve for switching between opening and closing of 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 where the switching valve opens the exhaust port. Item 2. The projector according to Item 1. 2. The projector according to claim 1, further comprising a focus adjustment mechanism for adjusting a focus of the lens of the lens barrel, wherein the focus adjustment mechanism is arranged on the housing independently of the lens barrel. 3. The lens barrel is
A lens, a lens frame that holds the lens, a cam ring that engages with the lens frame and determines the position of the lens frame in the optical axis direction, a fixed cylinder that is fixed to the set body, and the fixed cylinder that engages with the fixed cylinder. And a correction cylinder fixed to the cam ring and determining the position of the cam ring in the optical axis direction,
2. The cam ring and the correction cylinder have different coefficients of linear expansion, and the cam ring is movable in the optical axis direction in response to a dimensional change in the optical axis direction due to a temperature change of the correction cylinder. 4. The projector according to any one of items 1 to 3. A plurality of the lens frames, a zoom lens is configured by a lens group held respectively,
A cam groove is formed in the cam ring, a straight groove is formed in the fixed cylinder, and each of the plurality of lens frames is engaged with the cam groove and the straight groove.
By the rotation of the fixed cylinder and the cam ring fixed to the fixed cylinder around the optical axis, the lens groups held by the lens frames individually move in the optical axis direction,
The projector according to claim 4, wherein the cam ring and the fixed cylinder are fixed in the optical axis direction during rotation about the optical axis. A position on the optical axis of each of the plurality of lens frames is determined by a cam ring. The projector according to claim 5, wherein the projector is displaced in the optical axis direction. The projector according to claim 4, further comprising a correction cylinder fitted to an outer periphery of the correction cylinder, wherein a linear expansion coefficient of the correction cylinder is smaller than a linear expansion coefficient of the correction cylinder.

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