JPWO2012070286A1 - Lens unit - Google Patents

Abstract

A lens barrel of a conventional lens unit is magnetized, magnetic particles adhere to the lens barrel, and magnetic particles are brought into an electronic device or the like by incorporating the lens unit, and the performance of the electronic device is deteriorated. The lens barrel is made non-magnetic, and the difference in thermal expansion coefficient between the lens barrel and the lens is 20 × 10 −7 / ° C. or less, so that the lens performance is prevented from being deteriorated and damaged, and the cylindrical mirror is prevented. Provided is a lens unit that greatly reduces particles adhering to a cylinder.

Description

  The present invention relates to a lens unit in which a lens barrel and a lens used as optical components are integrated in electronic devices such as mobile products and projectors, optical communication devices, and the like.

  A lens unit 6 with a lens barrel shown in FIG. 14 is widely used as an optical component in electronic devices such as mobile products and projectors, optical communication devices, and the like. A lens unit 6 with a lens barrel described in Patent Document 1 as a prior art is composed of a lens barrel 7, a lens 8, and a low melting point glass 9 that joins the lens barrel 7 and the lens 8.

As the material of the lens barrel 7, austenitic stainless steel SUS304, SUS316, SUS321 having a thermal expansion coefficient higher by at least 20 × 10 ⁻⁷ / ° C. than the thermal expansion coefficient of the lens 8 is used.

  Further, a low melting point glass 9 containing lead oxide is used, which is harmful to the human body and at the same time pollutes the environment.

Further, in the conventional technique in which the lens barrel 7 and the lens 8 are joined by the low melting point glass 9, a defect in the manufacturing process related to the low melting point glass 9 and a defect in the low melting point glass 9 itself have occurred. For example, as described in Patent Document 2, the low-melting glass 9 containing lead oxide may be denatured in water or in a high-temperature and high-humidity environment. The modified low melting point glass 9 is easy to peel off, and peels off and adheres to the lens 8 and the optical fiber to reduce the amount of transmitted light.

JP-A-8-313779 JP 2007-192990 A

Tokyo Astronomical Observatory "Science Chronology", November 30, 1983, Maruzen P Product 25 (441)

In the manufacturing method in which the lens unit is manufactured using only the cylindrical lens barrel and the lens without using the low melting point glass 9 containing lead oxide, the processing temperature is increased because lead-free glass is used as the material of the lens. Therefore, when the cylindrical lens barrel is formed of a metal having a thermal expansion coefficient that is at least 20 × 10 ⁻⁷ / ° C. higher than the thermal expansion coefficient of the lens as in the prior art, a large stress is generated in the lens. Degradation of performance due to birefringence, etc. and breakage such as cracks occurred.

In the prior art described in Patent Document 1, austenitic stainless steel SUS304 and SUS321 are used as the material of the lens barrel 7. However, it is known that the stainless steel undergoes martensitic transformation and is magnetized when cold working (cutting, cold heading, etc.) is performed.

Therefore, the lens barrel 7 is magnetized during the cutting process, and magnetic particles adhere to the lens barrel 7 in the subsequent process. And the magnetic particles are brought into electronic devices and optical communication devices, etc., and drop off due to vibrations when carrying electronic devices etc. or motors that move within the devices, and adhere to optical components and degrade optical performance. was there.

  An object of the present invention is to provide a lens unit that prevents deterioration and breakage of a lens and significantly reduces particles adhering to a cylindrical barrel.

The lens unit of the present invention comprises a cylindrical lens barrel and a lens fixed to the inner peripheral surface of the cylindrical lens barrel, and the fixing is performed by melting the lens at a softening point or higher and solidifying at a normal temperature. The cylindrical lens barrel is a non-magnetic material, the difference in thermal expansion coefficient between the cylindrical lens barrel and the lens is 20 × 10 ⁻⁷ / ° C. or less, and the cylindrical mirror The thermal expansion coefficient of the lens is smaller than that of the tube.

  In such an embodiment, since the cylindrical lens barrel is made of a non-magnetic material, it is not magnetized during the cutting process, so that magnetic particles adhering to the cylindrical lens barrel in the subsequent process are greatly reduced. Can be reduced.

  In such an embodiment, since the stress applied to the lens is sufficiently small, the lens does not deteriorate in performance due to birefringence or the like, and is not damaged due to a crack or the like.

Therefore, according to the present invention, it is possible to provide a lens unit that prevents performance deterioration and breakage of the lens and significantly reduces particles adhering to the cylindrical lens barrel.

It is preferable that the cylindrical lens barrel is titanium or a titanium alloy.
In such an aspect, the cylindrical barrel is a non-magnetic material, and the difference in thermal expansion coefficient between the cylindrical barrel and the lens is 20 × 10 ⁻⁷ / ° C. or less, The thermal expansion coefficient of the lens is smaller than that of the cylindrical lens barrel.

It is preferable that the cylindrical lens barrel and the lens are hermetically bonded.
With such an aspect, it is possible to manufacture an electronic component that requires hermetic sealing and attach it to the casing of an electronic device or optical communication device that requires hermetic sealing.

The cylindrical barrel is preferably cylindrical.
According to such an aspect, the stress that the cylindrical lens barrel fastens the lens becomes uniform along the surface where the cylindrical lens barrel and the lens are in contact with each other. Problems such as cracks and cracks are less likely to occur in the lens.

The lens is preferably an aspheric lens.
Since the aspheric lens suppresses spherical aberration, the image surface of an electronic device such as a projector is sharpened, and the coupling efficiency of the optical communication device is improved.

It is preferable that an outer diameter of a portion of the cylindrical barrel that is in contact with the lens is ^20.5 times or less of an outer diameter of the lens.
According to this aspect, since the stress that holds and tightens the lens by the cylindrical lens barrel can be reduced, it is difficult for the lens to have a defect such as a crack or a crack.

  According to the present invention, since the cylindrical lens barrel is made of a non-magnetic material, it is not magnetized at the time of cutting, so that magnetic particles adhering to the cylindrical lens barrel in the subsequent process are greatly reduced. it can.

According to the present invention, since the stress applied to the lens is sufficiently small, the lens does not deteriorate its performance and does not break due to cracks or the like.

Therefore, according to the present invention, it is possible to provide a lens unit that prevents performance deterioration and breakage of the lens and significantly reduces particles adhering to the cylindrical barrel.

1 is a schematic plan view showing a lens unit with a nonmagnetic lens barrel according to a first embodiment as viewed from the upper surface side. It is the cross-sectional schematic cut | disconnected along the II-II line | wire in FIG. 1 of the lens unit with a nonmagnetic lens barrel which is 1st embodiment. It is explanatory drawing of the manufacturing method of the lens unit with a nonmagnetic lens-barrel which is 1st embodiment. It is a schematic diagram which shows the 1st application example which mounted the lens unit with a nonmagnetic lens-barrel which is 1st embodiment in the projector. It is a schematic diagram which shows the 2nd application example which mounted the lens unit with a nonmagnetic lens barrel which is 1st embodiment in the transmission / reception module for optical communications. It is explanatory drawing for calculating the stress which arises when temperature changes. It is a graph which shows the relationship between the stress weighted on the lens in 1st embodiment, and the outer diameter of a lens-barrel. 6 is a schematic plan view showing a first modification of the lens unit with a nonmagnetic lens barrel according to the first embodiment as viewed from above. FIG. 9 is a first modified example of the lens unit with a nonmagnetic lens barrel according to the first embodiment, and is a schematic cross-sectional view cut along line IX-IX in FIG. 8. 6 is a schematic plan view showing a second modification of the lens unit with a nonmagnetic lens barrel according to the first embodiment as viewed from above. 11 is a second modification of the lens unit with a nonmagnetic lens barrel according to the first embodiment, and is a schematic cross-sectional view cut along the line XI-XI in FIG. 10. 6 is a schematic plan view illustrating a third modification of the lens unit with a nonmagnetic lens barrel according to the first embodiment as viewed from above. It is a 3rd modification of the lens unit with a nonmagnetic lens barrel which is 1st embodiment, and is the cross-sectional schematic cut | disconnected along the XIII-XIII line | wire in FIG. It is the cross-sectional schematic of the lens unit with a lens-barrel comprised from the lens-barrel which is a prior art, a lens, and low melting glass. It is explanatory drawing which shows a mode that the lens barrel of the lens unit with a lens barrel which is a prior art was magnetized, and the magnetic partition adhered.

1 and 2 show a lens unit 1 with a nonmagnetic lens barrel according to a first embodiment to which the present invention is applied. The nonmagnetic lens barrel 2 has a cylindrical shape and is made of nonmagnetic titanium. An aspheric lens 3 is provided inside the nonmagnetic lens barrel 2.

In the present invention, a substance having an absolute value of magnetic susceptibility of 5 × 10 ⁻⁶ cm ³ / g or less is made nonmagnetic.

In the first embodiment, the material of the nonmagnetic lens barrel 2 is titanium, but is not limited thereto. A substance having an absolute value of magnetic susceptibility of 5 × 10 ⁻⁶ cm ³ / g or less can be selected. Titanium, bismuth, thallium, tungsten, tantalum, tin, aluminum, chromium, magnesium, gallium, niobium, zirconium, strontium, molybdenum, iridium, osmium, rhenium, gold, platinum, zinc, silver, copper, or two or more metals It can also be selected from an alloy made of the above, the metal, and an alloy added with impurities. It can also be selected from non-magnetic stainless steel. Further, the metal and the alloy have a difference in thermal expansion coefficient from the lens of 20 × 10 ⁻⁷ / ° C. or less, have a larger thermal expansion coefficient than the lens, and have a melting point larger than the softening point of the lens. is necessary.

From the data published at the present time, the difference in thermal expansion coefficient between the non-magnetic substance and the lens type of the lens is 20 × 10 ⁻⁷ / ° C. or less, and the thermal expansion coefficient is larger than that of the lens. As shown in Table 1, the combinations satisfying that the melting point is larger than the softening point of the lens are as follows. Made of copper and K-PKF80, K-GFK70, K-GFK68, chrome or titanium glass types made by Sumita Optical Glass Co., Ltd., and L-BAL35 or Sumita Optical Glass made by Ohara Co., Ltd. It is a combination of K-PBK40 and K-VC89 which are glass types, SUS305, SUS316 or SUS316L which is non-magnetic and K-CaFK95, K-PG325 and K-PG375 which are glass types made by Sumita Optical Glass Co., Ltd.

  In the first embodiment, the aspherical lens 3 and the cylindrical nonmagnetic lens barrel 2 are provided. However, the shape of the lens may be other than an aspherical surface, and the cylindrical lens barrel may have a shape other than the cylindrical shape. is there.

The manufacturing method of the lens unit 1 with a nonmagnetic lens barrel according to the first embodiment will be described with reference to FIG. First, the non-magnetic lens barrel 2 is manufactured by forming through holes in the non-magnetic material by cutting (a). The non-magnetic lens barrel 2 is installed in a press device, and the lens material 30 is inserted from the opening and placed on the lower mold 33 (b), and heated by the heater 31 to a temperature above the softening point of the lens material 30 (c). Next, the shape of the optical function surface forming portion is transferred to the lens material 30 by pressing the lens material 30 with the upper mold 32 and the lower mold 33 having the optical function surface forming portion (d). The aspherical lens 3 and the nonmagnetic lens barrel 2 are integrated, and an optical function surface is formed at the same time. Next, a plurality of lens units 1 with a non-magnetic lens barrel are installed in the film forming apparatus 34, and an optical functional film is formed on both sides of the optical functional surface by heating the film forming source 35 (e). As the material of the optical function film, a material for forming an antireflection film such as magnesium fluoride or silicon dioxide is used.

  The thermal expansion coefficient of the nonmagnetic lens barrel 2 is selected to be larger than the thermal expansion coefficient of the aspherical lens 3. After the aspherical lens 3 is integrally formed with the nonmagnetic lens barrel 2 by press molding, the nonmagnetic lens barrel 2 contracts more than the aspherical lens 3 in the cooling process from the softening point of the lens material 30 to the normal temperature. Therefore, the aspherical lens 3 is fastened to the nonmagnetic lens barrel 2 and is firmly and airtightly fixed.

In the first embodiment, the aspherical lens 3 is directly and firmly fixed to the nonmagnetic lens barrel 2 without using an adhesive layer such as low melting point glass.

  FIG. 4 is a schematic diagram illustrating a first application example in which the lens unit 1 with a nonmagnetic lens barrel according to the first embodiment is mounted on a projector 100 that is an image display device. The light from the lamp 101 is collected by the lens unit 1 with a nonmagnetic lens barrel, passes through the color wheel 102 that is color-coded by three colors rotated by the motor 102a, and is again collected by the lens unit 1 with a nonmagnetic lens barrel. The light is reflected by the optical semiconductor 103 provided with hundreds of thousands to millions of mirrors that move independently, and is projected onto the screen by the projection lens 104.

By the way, it is generally known that a magnetic metal and its metal scrap are magnetized by metal processing. This is considered that the temperature of the metal and the metal scrap exceeds the Curie temperature due to heat generated in metal processing, and is magnetized by a leakage magnetic field from the drive motor or the like, geomagnetism, or the like.

It is known that austenitic stainless steel with a low Ni content undergoes martensitic transformation and becomes magnetized when cold working (cutting, cold heading, etc.) is performed. This magnetization is affected in relation to the chemical composition and the cold work rate. Therefore, some austenitic stainless steels SUS304 and SUS321 with a low Ni content undergo martensitic transformation and become magnetized with the amount of processing.

In the first embodiment according to the present invention, the nonmagnetic column 2 is made of titanium, so that it is nonmagnetic and is not magnetized by cold working or the like.

  The lens barrel 7 formed from austenitic stainless steel SUS304 and SUS321 described in Patent Document 1 is magnetized during cutting, and as shown in FIG. 15, the magnetic particles 202 adhere to the lens barrel 7 in the subsequent process, and the mirror When the cylinder-equipped lens unit 6 is mounted on the projector 100, the magnetic particles 202 may be brought into the housing of the projector 100.

The magnetic particles 202 attached to the lens barrel 7 drop off from the lens barrel 7 and adhere to the surfaces of the lens 8, the projection lens 104, and the like due to the carrying, handling, and vibration generated by the motor 102a.

  Further, as shown in FIG. 4, there is a motor 102a in the vicinity of the lens unit 1 with a nonmagnetic lens barrel, and the leakage magnetic field from the permanent magnet is always applied to the lens unit 1 with a nonmagnetic lens barrel. . In the case of the magnetized lens barrel 7 according to the prior art, the magnetic field 202 is demagnetized by the leakage magnetic field, the adhesion force of the magnetic particles 202 to the lens barrel 7 is weakened, and the magnetic particles 202 are likely to adhere to the surface of the lens 8 or the projection lens 104. Become.

  If the motor 102a is shielded, the problem is reduced, but this is contrary to miniaturization. In other words, the lens unit 1 with a non-magnetic lens barrel is suitable for miniaturization because it can prevent the above problems without shielding.

As described above, if the magnetic particles 202 adhere to the surface of the aspherical lens 3, the projection lens 104, or the like, an image defect occurs in the projector 100 that is an image display device, which is a problem. However, according to the present invention, since the lens unit 1 with a non-magnetic lens barrel includes the non-magnetic lens barrel 2 that is not magnetized, the magnetic particles 202 and the like are attached to the non-magnetic lens barrel 2 according to the prior art. Compared to a significant reduction.

Therefore, according to the present invention, by providing the non-magnetic lens barrel 2, it is possible to provide a lens unit that greatly reduces the adhesion of the magnetic part 202 to the cylindrical lens barrel. Bringing magnetic particles 202 into communication equipment and the like has been greatly reduced.

Further, the color wheel 102 shown in FIG. 4 as the first application example is equipped with a magnetic sensor for detecting a rotation angle and a magnetic sensor for a brushless motor. The brushless motor is used from the request of high performance and long life because the motor 102a rotates at a high speed, and the brushless motor is equipped with a magnetic sensor for detecting the rotation angle.

When the lens unit 6 with the lens barrel is mounted on the projector 100, the magnetized magnetic field from the lens barrel 7 acts on the sensitive surface of the magnetic sensor to generate an output voltage. This output voltage becomes an error in the rotation angle, and the high-precision control of the color wheel 102 is impaired. As a result, the demand for high brightness and high image quality for the projector 100 is impaired.

According to the present invention, since the lens unit 1 with a nonmagnetic lens barrel is not magnetized, an output voltage that causes an error is not generated from the magnetic sensor. Therefore, the color wheel 102 can be controlled with high accuracy, and the projector 100 with high brightness and high image quality can be provided.

Although the example of the projector 100 which is an image display device has been described as the first application example, it is not limited to the projector 100. For example, in recent years, lens units with a lens barrel have begun to be used in products that are easy to carry such as mobile products and microprojectors that are miniaturized by using a high-intensity semiconductor laser as a light source. The present invention is effective even when applied to these products.

As a micro projector, for example, three primary colors of laser light are converted into vertical one-dimensional illumination light by an illumination lens, and this one-dimensional illumination light is diffracted by a fine MEMS (Micro Electro-Mechanical Systems) device to form a one-dimensional image. In some cases, only the diffracted light of this one-dimensional image is collected through a projection lens, and is scanned in the horizontal direction by a scanning mirror to project a two-dimensional image onto a screen.

  In recent years, the demand for optical communication networks is increasing in order to exchange a large amount of information at high speed. FIG. 5 shows a second application example in which the lens unit 1 with a nonmagnetic lens barrel according to the first embodiment is mounted on a transmission / reception module 300 in such optical communication.

The light emitted from the laser diode 303 which is a light emitting element is collected by the lens unit 1 with a non-magnetic lens barrel, enters the optical fiber 301 through the multiplexing filter 302, and the light emitted from the optical fiber 301 is The light is reflected by the multiplexing filter 302, collected by the lens unit 1 with a non-magnetic lens barrel, and enters a photodiode 304 that is a light receiving element.

As in the first application example, when the lens unit 6 with the lens barrel is mounted on the transmission / reception module 300, the magnetic particles 202 and the like attached to the lens barrel 7 due to vibrations generated in the transmission / reception module 300 are mirrored. It is conceivable that the lens falls off the cylinder 7 and adheres to the surface of the lens 8 or the multiplexing filter 302. As a result, the light intensity deteriorates, and when the magnetic particles 202 are large, it causes a failure in which light is not transmitted and received.

According to the present invention, the magnetic particles 202 adhering to the non-magnetic lens barrel 2 can be greatly reduced, so that the light intensity generated by mounting the lens unit 6 with the lens barrel on the transmission / reception module 300 which is an optical communication device is deteriorated. In addition, when the magnetic particles 202 are large, the problem that light is not transmitted / received can be greatly reduced.

According to the present invention, by the manufacturing method described above, for example, as shown in FIG. 1, a lens unit 1 with a nonmagnetic lens barrel integrated with only a nonmagnetic lens barrel 2 and an aspherical lens 3 is obtained. However, in the prior art, as shown in FIG. 14, the lens unit 6 with the lens barrel is composed of the lens barrel 7, the lens 8, and the low melting point glass 9.

  Moreover, as described in Patent Document 2, the low-melting glass 9 containing lead oxide is vulnerable to moisture, changes as time passes, and fine cracks enter the surface. Further, the low melting point glass 9 is peeled off by a fine crack. The peeled low-melting glass 9 adheres to the lens 8 and becomes white turbid because fine cracks are formed on the surface thereof, thereby inhibiting the transparency of the lens 8. In addition, the lens bonding strength is reduced by peeling, and in a severe case, the lens 8 may even fall off.

  According to the present invention, since the low-melting glass 9 is not included, there is no problem in the manufacturing process related to the low-melting glass 9 or in the low-melting glass 9 itself.

In the prior art described in Patent Document 1, the lens 8 and the lens barrel 7 having a slightly larger inner diameter than the lens 8 and the low melting glass 9 are heated and heated to 450 ° C. at which the low melting glass 9 melts, The glass 9 was fixed by cooling into the normal temperature after flowing into the gap between the lens barrel 7 and the lens 8 and filling it. At this time, the thermal expansion coefficient of the low-melting glass 9 is made smaller than that of the lens barrel 7 and larger than that of the lens 8, thereby relieving stress on the lens 8 due to contraction of the lens barrel 7.

  According to the present invention, the lens unit 1 with a nonmagnetic lens barrel is formed only by the nonmagnetic lens barrel 2 and the aspherical lens 3 as shown in FIG. 1, for example, without using low melting point glass containing lead. . Therefore, in the manufacturing method described above shown in FIG. 3, it is necessary to heat the lens material 30 to the softening point. In the first embodiment, lead-free glass (manufactured by OHARA INC .: L-BAL35) is used as the lens material 30, and the softening point thereof is 619 ° C.

In the first embodiment, lead-free glass (manufactured by OHARA, Inc .: L-BAL35) is used as the lens material 30, but is not limited thereto. It is possible to use lead-free glass having a difference in coefficient of thermal expansion from that of the cylindrical lens barrel of 20 × 10 ⁻⁷ / ° C. or less and a coefficient of thermal expansion smaller than that of the cylindrical lens barrel.

Compared with the prior art described in Patent Document 1, the manufacturing method of the present invention has a higher temperature. Therefore, when the cylindrical lens barrel is formed of a material having a thermal expansion coefficient that is at least 20 × 10 ⁻⁷ / ° C. higher than the thermal expansion coefficient of the lens as in the prior art described in Patent Document 1, the lens As a result, a large stress was generated on the surface, resulting in performance degradation due to birefringence and the like, and breakage such as cracks.

Therefore, according to the present invention, the difference in thermal expansion coefficient between the cylindrical barrel and the lens is 20 × 10 ⁻⁷ / ° C. or less, and the thermal expansion coefficient of the lens from the cylindrical barrel. Needed to be small. This will be described below.

  In the configuration of the column 50 that is the lens and the cylinder 51 that is the cylindrical barrel shown in FIG. 6, the column 50 and the cylinder 51 are loaded when cooled from the softening point of the column 50 to the normal temperature (25 ° C.). Calculate the stress to be applied. Here, in order to simplify the calculation, the lens is the cylinder 50 and the cylindrical barrel is the cylinder 51, but it is considered that there is no practical problem. Where α = coefficient of thermal expansion, T = softening point−25, σ = stress, E = Young's modulus, subscript 1 means a cylinder, subscript 2 means a cylinder. The subscript z means the z-axis direction, and the subscript r means the r-axis direction. L is the length of the column 50 and the cylinder 51 in the z-axis direction, D1 is the outer diameter of the column 50, and D2 is the outer diameter of the cylinder 51.

In the z-axis direction, the contraction length due to heat = L × α × T, the contraction length due to stress = L × σ / E, and the contraction length of the cylinder 50 and the cylinder 51 is the same, so L × (α1 × T + σ1z / E1) = L × (α2 × T + σ2z / E2) (1)
Since the external force is not weighted,
S1 * [sigma] 1z + S2 * [sigma] 2z = 0 (2) where S1 = the cross-sectional area of the cylinder 50 and S2 = the cross-sectional area of the cylinder 50.
From equations (1) and (2), σ1z = S2 × E1 × E2 × (α2−α1) × T / (S1 × E1 + S2 × E2) (3) σ2z = −S1 × E1 × E2 × (α2−α1) XT / (S1 * E1 + S2 * E2) (4)

About r-axis direction, shrinkage length due to heat = D1 × α × T, shrinkage length due to stress = D1 × σ
/ E, and the contraction length of the outer diameter of the cylinder 50 and the inner diameter of the cylinder 51 is the same,
D1 × (α1 × T + σ1r / E1) = D1 × (α2 × T + σ2r / E2) (5)
Since the external force is not weighted,
π × D1 × L × (σ1r + σ2r) = 0 (6) From equations (5) and (6), σ1r = E1 × E2 × (α2−α1) × T / (E1 + E2) (7)
σ2r = −E1 × E2 × (α2−α1) × T / (E1 + E2) (8)
It is obtained.

In the first embodiment, the stress σ1z and the stress σ1r applied to the cylinder 50 that is the lens are calculated. The cylinder 50 is made of lead-free glass (manufactured by OHARA, Inc .: L-BAL35), and the cylinder 51 is made of titanium. The softening point of L-BAL35 is 619 ° C., and T = 619 ° C.-25 ° C. (ordinary temperature) = 594 ° C. ^{α1 = 81 × 10 -7 / ℃} , a ^{α2 = 84 × 10 -7 /℃,E1=10.08×10 10} N / m 2, E2 = 10.63 × 10 10 N / m 2. Further, D1 = 0.0038 m, D2 = 0.005 m, S1 = π x (D1 / 2) x (D1 / 2), S2 = π x (D2 / 2) x (D2 / 2)-π x (D1 / 2) × (D1 / 2). Substituting these values into Equations (3) and (7) and calculating,
σ1z = 7.8 × 10 ⁶ N / m ²
σ1r = 9.2 × 10 ⁶ N / m ²
It is obtained.

However, when austenitic stainless steel SUS304 is used for the cylinder 51 as in the prior art described in Patent Document 1, α2 = 184 × 10 ⁻⁷ / ° C. and E2 = 19.3 × 10 ¹⁰ N / m ² . , Others are calculated using the above values,
σ1z = 3.6 × 10 ⁸ N / m ²
σ1r = 4.1 × 10 ⁸ N / m ²
It is obtained.

Therefore, compared with the case where the cylinder 51 is formed of titanium as in the present invention, when the austenitic stainless steel SUS304 described in Patent Document 1 is formed, the stress applied to the column 50 is almost 100 times larger, and the first In the aspherical lens 3 according to the embodiment, the performance deterioration, breakage such as a crack occurred.

Non-Patent Document 1 shows the tensile strength that is the maximum tensile stress immediately before breaking. The tensile strength is also referred to as mechanical strength, and is described as mechanical strength in the present invention. According to this non-patent document 1, the mechanical strength of the glass is 3 × 10 ^{7 to} 9 × 10 ⁷ N / m ² . The stress σ1z and the stress σ1r in Embodiment 1 of the present invention are less than the mechanical strength of the glass. However, when the austenitic stainless steel SUS304 described in Patent Document 1 is used, the mechanical strength is exceeded.

Incidentally, the ^{α2 = 81 × 10 -7 / ℃} ( same as L-BAL35) + 20 × 10 -7 /℃,E2=10.63×10 10 N / m 2 ( same as titanium) and the other first When calculating using the numerical values of the embodiment,
σ1z = 5.2 × 10 ⁷ N / m ²
σ1r = 6.2 × 10 ⁷ N / m ²
It becomes. This value is almost the same as the mechanical strength of glass.

Thus, the difference in thermal expansion coefficient between the cylindrical barrel and the lens is 20 × 10 ⁻⁷ / ° C. or less, and the thermal expansion coefficient of the lens is made smaller than that of the cylindrical barrel. Thus, the lens could be firmly fixed to the cylindrical lens barrel, and the stress applied to the lens could be made substantially lower than the mechanical strength of the glass.

As can be seen from Equation (3), when the cross-sectional area S2 of the cylindrical lens barrel is reduced, the stress σ1z applied to the lens in the z-axis direction is reduced. Therefore, it is effective to reduce the cross-sectional area S2 of the cylindrical barrel in order to prevent the lens from being damaged by being stressed more than the mechanical strength.

  On the other hand, the stress σ1r applied to the lens in the r-axis direction does not depend on the shape but depends on the thermal expansion coefficient, Young's modulus, and softening point. Therefore, in order to reduce the stress σ1r applied to the lens in the r-axis direction, it is necessary to appropriately select materials for the lens and the cylindrical lens barrel.

FIG. 7 shows the relationship between the stress applied to the lens and the outer diameter of the cylindrical lens barrel by substituting the numerical values in the first embodiment into the expressions (3) and (7). Indicated. However, α1 = 81 × 10 ⁻⁷ / ° C., α2 = 84 × 10 ⁻⁷ / ° C., T = softening point−25 = 614-25 = 594 ° C., E1 = 10.008 × 10 ¹⁰ N / m ² , E2 = 10.63 × 10 ¹⁰ N / m ² , and since D1 = 3.8 × 10 ⁻³ m, S1 = 1.13 × 10 ⁻⁵ m ² .

Referring to FIG. 7, the stress σ1r determined by the material of the lens and the cylindrical lens barrel is constant at 9.2 × 10 ⁶ N / m ^2, and as the outer diameter of the cylindrical lens barrel decreases. The stress σ1z becomes small. That is, the material of the lens and the cylindrical barrel is appropriately selected to reduce the stress σ1r, and the shape of the cylindrical barrel is σ1z ≦ σ1r (9)
Since the stress applied to the lens can be reduced, the destruction of the lens due to the stress generated by cooling from the softening point to the normal temperature (25 ° C.) can be suppressed. In this case, the stress applied to the cylindrical barrel is increased, but the cylindrical barrel has a higher mechanical strength than the lens, and the increased stress is applied to the cylindrical mirror. This is preferable because the tube is deformed to relieve the stress applied to the lens.

Substituting Equation (3) and Equation (7) into Equation (9), dividing both sides by E1 × E2 × (α2−α1) × T,
S2 / (S1 × E1 + S2 × E2) ≦ 1 / (E1 + E2)
And when both sides are organized,
S2 ≦ S1
It becomes. next,
S1 = π × (D1 / 2) × (D1 / 2), S2 = π × (D2 / 2) × (D2 / 2) −π ×
Since (D1 / 2) × (D1 / 2),
D2 ≦ 2 ^0.5 × D1 (10)
Get. Therefore, the outer diameter of said tubular barrel (D2), it is appropriate to choose less than the value that is 2 ^{to 0.5} times the outer diameter (D1) of the lens.

As described above, in order to reduce the stress generated by cooling from the softening point to the normal temperature (25 ° C.), the outer diameter of the cylindrical lens barrel that is in contact with the lens may be reduced. Moreover, in order to make it easy to handle with a tool or the like, it is preferable that a protruding portion is provided and the outer diameter of the cylindrical lens barrel is large. Modified examples for achieving both of these are shown in schematic plan views in FIGS. 8, 10, and 12, and in schematic cross sections in FIGS. In these modified examples, the outer diameter of the portion in contact with the lens is small with respect to the cylindrical lens barrel, and the large outer diameter is provided in the other portions.

DESCRIPTION OF SYMBOLS 1 Lens unit with a nonmagnetic lens barrel 2 Nonmagnetic lens barrel 3 Aspherical lens 6 Lens unit with lens barrel 7 Lens barrel 8 Lens 9 Low melting point glass 30 Lens material 31 Heater 32 Upper mold 33 Lower mold 34 Film formation apparatus 35 Film formation Source 50 Cylinder 51 Cylinder 100 Projector 101 Lamp 102 Color wheel 102a Motor 103 Optical semiconductor 104 Projection lens 202 Magnetic particle 300 Transmission / reception module 301 Optical fiber 302 Combined filter 303 Laser diode 304 Photo diode

Claims (6)

A cylindrical barrel,
A lens fixed to the inner peripheral surface of the cylindrical barrel;
Consists of
The fixing is performed by melting the lens at a softening point or higher and solidifying at a normal temperature.
The cylindrical barrel is a non-magnetic material;
The difference in thermal expansion coefficient between the cylindrical lens barrel and the lens is 20 × 10 ⁻⁷ / ° C. or less, the thermal expansion coefficient of the lens is smaller than that of the cylindrical lens barrel,
Lens unit characterized by The lens unit according to claim 1, wherein the cylindrical barrel is titanium or a titanium alloy. The lens unit according to claim 1, wherein the cylindrical barrel and the lens are airtightly joined. The lens unit according to any one of claims 1 to 3, wherein the cylindrical barrel is cylindrical. The lens unit according to any one of claims 1 to 4, wherein the lens is an aspheric lens. 6. The lens unit according to claim 1, wherein an outer diameter of a portion of the cylindrical lens barrel that is in contact with the lens is ^20.5 times or less of an outer diameter of the lens.

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