JP2005164703A - Rod lens and rod lens array - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rod lens and a rod lens array with a filter function without causing deterioration in resolution, and to provide the rod lens array which is excellent in color property and resolution even in use of the rod lens where chromatic aberration exists in some extent. <P>SOLUTION: Regarding the rod lens whose refractive index continuously reduces from the center axis toward the outer circumference, the rod lens is provided with a 1st light absorbing layer containing light absorber for absorbing light of each wavelength, R, G, B in a part within a prescribed extent of ≤100μm from the position on the outer circumferential surface to the center axis, and a 2nd light absorbing layer containing light absorber for absorbing light of one or two wavelengths out of wavelengths R, G and B in an area including the center axis. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rod lens and a rod lens array used as an optical transmission body such as a light focusing rod-shaped lens, an image sensor, a printer, and a display.

  A rod lens is a cylindrical lens having a refractive index distribution in which the refractive index continuously decreases from the center toward the outer periphery. In general, both end faces thereof are parallel planes perpendicular to the central axis. It is mirror-polished and used alone as a microlens. In addition, a large number of rod lenses are arranged and bonded and fixed between two substrates in one or more rows so that the central axes of the rod lenses are substantially parallel to each other. It is widely used for various scanners such as hand scanners, parts for image sensors in copying machines and facsimile machines, writing devices such as LED printers, and the like. Furthermore, a rod lens plate (hereinafter referred to as “lens plate”) in which a large number of rod lenses are two-dimensionally arranged and fixed is an optical component such as a display or an optical element of a two-dimensional image sensor such as a fingerprint sensor. It is used as a part.

  Rod lenses include those made of glass and plastic, and are manufactured by known manufacturing methods such as an ion exchange method and a monomer interdiffusion method, respectively. In any of the manufacturing methods, an irregular portion whose refractive index distribution deviates from a desired distribution is formed on the outer peripheral portion of the manufactured rod lens. In order to suppress the deterioration of the optical characteristics due to the irregular portion, for example, in a glass rod lens, the irregular portion formed on the outer peripheral portion is roughened by hydrofluoric acid treatment or the like, and then the black resin is coated and transmitted. It has been done to cut the light. Further, in a plastic rod lens, as disclosed in JP-A-9-127353 (Patent Document 1), a dye is added to the outer peripheral portion with an irregular refractive index distribution to cut the transmitted light. Has been done.

  On the other hand, in recent years, with the widespread use of high-resolution color scanners, there is an increasing demand for rod lenses having good color characteristics such as resolution and chromatic aberration at each wavelength of red, green, and blue (R, G, B). Among the color characteristics of the rod lens, chromatic aberration is caused by the wavelength dependence of the refractive index of the material constituting the rod lens. In general, since the wavelength dispersion of the refractive index of the material in the center of the rod lens is large, the conjugate length Tc is greater at the red (R) wavelength than at the rod lens conjugate length Tc at the green (G) wavelength. Becomes longer, and the conjugate length Tc becomes shorter at the wavelength of blue (B). For this reason, in a rod lens having a large chromatic aberration, when the set position of the optical system is adjusted to the conjugate length Tc of G, the R and B wavelengths are blurred and the resolution is lowered. There is.

A rod lens having a large chromatic aberration means a lens in which the difference in the period length of light transmitted by the rod lens varies greatly depending on the wavelength, and the chromatic aberration (ΔP) is expressed by the following equation (1).

(Here, P (R), P (B), and P (G) are the period lengths for the C line, D line, and F line, respectively.)
In order to improve such chromatic aberration, it is conceivable to change the material system constituting the rod lens so as to reduce the difference in conjugate length Tc at each wavelength of R, G, B of the rod lens. There are limited combinations of materials that can be reduced, especially for plastic rod lenses.

Further, as a method for improving the color characteristics of a lens array using a rod lens having a certain degree of chromatic aberration, Japanese Patent Application Laid-Open No. 10-130033 (Patent Document 2) and Japanese Patent Application Laid-Open No. 10-221558 (Patent Document 3). As disclosed, by using a plurality of types of rod lenses that transmit only light of a specific wavelength, and adjusting the conjugate length Tc of the rod lens at the transmission wavelength of each rod lens, the chromatic aberration of the lens array is improved. A method has been proposed.
JP-A-9-127353 Japanese Patent Laid-Open No. 10-13003 JP-A-10-221558

  However, in the methods described in Patent Document 2 and Patent Document 3, although chromatic aberration as a lens array is improved to some extent, flare light caused by an irregular portion of the refractive index distribution at the outer peripheral portion, crosstalk between rod lenses, and the like. There was a problem of a decrease in resolution.

  Accordingly, an object of the present invention is to provide a rod lens and a rod lens array having a filter function of a specific wavelength without causing a decrease in resolution due to flare light or crosstalk light, and to provide a rod lens having a certain degree of chromatic aberration. It is to provide a rod lens array having excellent color characteristics and resolution even when used.

  That is, the rod lens of the present invention is a rod lens in which the refractive index continuously decreases from the central axis toward the outer periphery, and in a predetermined range within 100 μm from the position of the outer peripheral surface toward the central axis. It has a first light absorption layer containing a light absorber that absorbs light of each wavelength of R, G, and B, and has one or two wavelengths of each of R, G, and B wavelengths in a region including the central axis. It has the 2nd light absorption layer containing the light absorber which absorbs light, It is characterized by the above-mentioned.

  The rod lens array of the present invention includes a rod lens array in which a plurality of rod lenses as described above are arrayed and fixed between two substrates so that the central axes of the rod lenses are substantially parallel to each other. At least one row is provided. Furthermore, in the rod lens array of the present invention, a plurality of rod lenses of two specific types of rod lenses are arranged and fixed so that the central axes of the rod lenses are substantially parallel to each other between the two substrates. At least one rod lens array is provided.

  The present invention provides a first light-absorbing layer containing a light absorbing agent that absorbs light of each wavelength of R, G, and B in an outer peripheral portion having an irregular refractive index distribution, and R, G, and B in a region including a central axis By forming the second light absorption layer containing a light absorber that absorbs light of a specific wavelength among the wavelengths, the resolution at each wavelength of R, G, and B is improved, and light of a specific wavelength is received. It is possible to provide a rod lens and a lens array having a filter function that cuts almost.

  In addition, the present invention can block flare light and crosstalk between rod lenses by the first light absorption layer, provide a high-resolution rod lens, and at each wavelength of R, G, and B Since the difference in conjugate length Tc can be made smaller than the conjugate length Tc of each rod lens, a lens array having excellent color characteristics can be provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

The rod lens of the present invention is a cylindrical lens having a refractive index distribution in which the refractive index continuously decreases from the center toward the outer periphery. As the refractive index distribution, when the radius of the rod lens is r in a cross section perpendicular to the central axis of the rod lens, the refractive index distribution in the range of 0.3r to 0.7r at least from the central axis toward the outer periphery is as follows. It is preferable to approximate a quadratic curve distribution defined by the following formula (2).

(Where n ₀ is the refractive index (central refractive index) at the central axis of the rod lens, L is the distance from the central axis of the rod lens (0 ≦ L ≦ r), and g is the refractive index of the rod lens. (It is a distribution constant, and n (L) is a refractive index at a position of a distance L from the central axis of the rod lens.)
The radius r of the rod lens of the present invention is not particularly limited, but the radius r is preferably small from the viewpoint of compacting the optical system, and the radius r is preferably large from the viewpoint of handling when processing the rod lens. . For this reason, the radius r of the rod lens is preferably in the range of 0.05 to 1 mm, more preferably in the range of 0.1 to 0.5 mm.

Further, the refractive index distribution constant g of the rod lens is not particularly limited, but is 0.2 to 3 mm ⁻¹ from the viewpoint of compacting the optical system, ensuring the working distance of the optical system, and handling. More preferably, it is the range of 0.5-2 mm < ^-1 >.

  As shown in FIG. 1, the rod lens of the present invention has R, G, and B in a predetermined range within 100 μm from the position of the outer peripheral surface toward the central axis in a cross section perpendicular to the central axis 2 of the rod lens 1. It has the 1st light absorption layer 3 containing the light absorber which absorbs the light of a wavelength, It is characterized by the above-mentioned. By forming the first light absorption layer 3 on the outer periphery of the rod lens 1 in this way, the refractive index distribution formed on the outer periphery of the rod lens 1 is reduced without reducing the amount of light emitted from the rod lens 1. It is possible to provide a high-resolution rod lens 1 by preventing flare light caused by irregular portions and crosstalk between rod lenses when a lens array is used.

  In the present invention, from the position of the outer peripheral surface of the rod lens 1 together with the first light absorption layer 3 for the purpose of preventing crosstalk due to external light including near infrared light entering the device from the outside. You may form the layer containing the light absorber which absorbs near-infrared light (for example, the wavelength of the range of 700-1000 nm) in the part of the predetermined range within 100 micrometers toward the central axis 2. FIG. In this case, a light absorber that absorbs near-infrared light can also be contained in the first light absorption layer 3.

  Furthermore, in the rod lens 1 of the present invention, it is preferable that the first light absorption layer 3 is formed in a region including at least the outer peripheral surface, so that flare light and crosstalk between the rod lenses are formed. Can be more effectively prevented.

  In the present invention, the first light absorbing layer 3 and the region including the central axis 2 of the rod lens 1 include a light absorber that absorbs light of a specific wavelength among R, G, and B wavelengths. It is necessary to form the second light absorption layer 4. By forming the second light absorption layer 4 as described above, it is possible to provide the rod lens 1 having a filter function of transmitting only a specific wavelength among the R, G, and B wavelengths.

  The second light absorption layer 4 includes the central axis 2 of the rod lens 1 and is formed in a region up to the end on the central axis side of the first light absorption layer 3 formed on the outer periphery of the rod lens 1. Preferably it is. That is, as shown in FIG. 1, it is preferable that the first light absorption layer 3 and the second light absorption layer 4 are formed continuously. Thus, the area | region which does not contain a light absorber in the area | region from the central axis 2 of a rod lens 1 to an outer peripheral part by forming the 1st light absorption layer 3 and the 2nd light absorption layer 4 continuously. Therefore, unnecessary light incident from the end face of the rod lens 1 is not transmitted, and the resolution is not reduced by unnecessary light.

  In the present invention, the R, G, and B wavelengths are the R wavelength, G wavelength, and B wavelength of an optical system such as an LED that is used, and usually from the R, G, and B LEDs. It is a wavelength corresponding to light to be emitted. These R, G, and B wavelengths are preferably in the ranges of 600 to 680 nm, 500 to 590 nm, and 430 to 490 nm, respectively. By setting each wavelength of R, G, and B within these ranges, each of R, G, and B is used in a lens array that uses two or more rod lenses having a second light absorption layer that absorbs a specific wavelength. The resolution for each wavelength can be increased, and a color image can be read, written, displayed and the like without blurring of the image.

  In the rod lens of the present invention, the light transmittance at the R wavelength is 5 times or more of the light transmittance at the B wavelength, or the light transmittance at the B wavelength is 5 times or more of the light transmittance at the R wavelength. It is preferable that By configuring in this way, in the lens array that can efficiently cut the light of the wavelength of R or B, and uses two or more rod lenses having a second light absorption layer that absorbs a specific wavelength, The resolution for each of the R, G, and B wavelengths can be increased, and a color image that does not blur the image can be read, written, displayed, and the like.

  In the present invention, it is preferable that the first light absorption layer and the second light absorption layer have a substantially uniform light absorber, and the concentration of the light absorber is as uniform as possible in each layer. It is preferable because good resolution can be obtained and a desired effect can be obtained by using a relatively small amount of a light diffusing agent. In this case, it is preferable that the light absorber is uniformly dispersed or bonded in the material constituting the rod lens.

Moreover, it is preferable to make content in each light absorption layer of a light absorber into the range of 0.001-10 mass%, More preferably, it is the range of 0.001-1 mass%. This is because if the content of the light absorber is less than 0.001% by mass, light having a specific wavelength cannot be sufficiently absorbed and a desired effect tends not to be exhibited. If the content exceeds 50%, the intensity of ultraviolet rays, etc., when the rod lens is photocured is reduced by scattering and absorption, and the strong elongation characteristics of the rod lens are reduced, and the dissolved state in the rod lens material stock solution is reduced. This is because clogging of the filter and ejection failure from the nozzle tend to occur.
In the present invention, the light absorption amount of each wavelength of the first light absorption layer and the second light absorption layer is preferably 20% or less.

  As the light absorber used in the rod lens of the present invention, various dyes, pigments, pigments and the like that can absorb light having a wavelength used in an optical system in which the rod lens is used can be used. These light absorbers are preferably light absorbers that absorb only a specific wavelength region, and two or more types of light absorbers having different wavelengths to be absorbed can be used in combination as necessary.

  The light absorber used in the present invention is not particularly limited as long as it can absorb light of a desired wavelength, but as a typical light absorber, for example, light of R wavelength can be used. Absorbing light absorbers include Kayset Blue ACR manufactured by Nippon Kayaku Co., Ltd., Blue 4G manufactured by Mitsubishi Chemical Co., Ltd., and as light absorbing agents absorbing light of G wavelength, Kayset Red G manufactured by Nippon Kayaku Co., Ltd., Nippon Kayaku Co., Ltd. Kayset Red 130 manufactured by Nippon Kayaku Co., Ltd., such as Kayset Red 130 manufactured by Nippon Kayaku Co., Ltd., and Kasset Yellow 2G manufactured by Nippon Kayaku Co., Ltd. Kayaset Orange G, Nippon Kayaku Co., Ltd., Kayase Yellow AG, Nippon Kayaku Co., Ltd. Examples of light absorbers that absorb near infrared light such as et Yellow EG, MS Yellow HD-180 manufactured by Mitsui Toatsu Dye Co., Ltd. include Kayasorb CY-10 manufactured by Nippon Kayaku Co., Ltd., and these light absorbers Can be used alone or in combination. One or more light absorbers that absorb light of R wavelength, light absorbers that absorb light of G wavelength, and light absorbers that absorb light of B wavelength are selected and used in combination. By doing so, a first light absorption layer that absorbs light of each wavelength of R, G, and B can be formed.

  The rod lens of the present invention may be made of glass or plastic, but from the viewpoint of lightening optical components, safety at breakage or breakage, ease of processing, etc. Preferably there is.

Next, as a method for manufacturing the rod lens of the present invention, a method for manufacturing a plastic rod lens by a monomer interdiffusion method will be described.
First, N uncured materials having a refractive index n after curing satisfying n ₁ > n ₂ >...> _{N N} (N ≧ 3) are gradually decreased from the center toward the outer periphery. In such an arrangement, it is shaped into an uncured laminated body (hereinafter referred to as “filamentous body”) that is concentrically laminated, and adjacent so that the refractive index distribution between each layer of the filamentous body is continuous. While performing the interdiffusion treatment of the materials between the layers or after the mutual diffusion treatment, the filamentous body is cured to obtain a rod lens raw yarn. If necessary, relaxation treatment may be performed after the obtained rod lens raw yarn is heated and stretched. The rod lens yarn produced in this way is appropriately cut into a predetermined size to obtain a rod lens. In the rod lens of the present invention, it is preferable to uniformly dissolve or disperse a light absorber such as a dye appropriately set in advance on the uncured product. Thus, each uncured material to which the light absorber is added forms a light absorption layer in which the concentration of the light absorber is uniform.

  As the material constituting the uncured material, a radical polymerizable vinyl monomer, or a composition comprising a radical polymerizable vinyl monomer and a polymer soluble in the monomer can be used. .

  Specific examples of the radical polymerizable vinyl monomer include methyl methacrylate (n = 1.49), styrene (n = 1.59), chlorostyrene (n = 1.61), vinyl acetate (n = 1.47). 2,2,3,3-tetrafluoropropyl (meth) acrylate, 2,2,3,3,4,4,5,5-octafluoropentyl (meth) acrylate, 2,2,3,4,4 , Fluorinated alkyl (meth) acrylates such as 2,4-hexafluorobutyl (meth) acrylate and 2,2,2-trifluoroethyl (meth) acrylate (n = 1.37 to 1.44), refractive index 1.43 ~ 1.62 (meth) acrylates such as ethyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, hydroxyalkyl (meth) acrylate, alkylene glycol (meth) acrylate, trimethylo Other diethylene glycol bisallyl carbonates such as rupropanedi or tri (meth) acrylate, pentaerythritol di, tri or tetra (meth) acrylate, diglycerin tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, fluorinated alkylene glycol poly (Meth) acrylate etc. are mentioned.

  In order to easily adjust the viscosity of the uncured material when forming the filament from these uncured materials, and to have a continuous refractive index distribution from the center to the outer periphery of the filament, The material is preferably composed of a vinyl monomer and a soluble polymer.

  The polymer that can be used here needs to have good compatibility with the polymer produced from the radical polymerizable vinyl monomer, for example, polymethyl methacrylate (n = 1.49), polymethyl methacrylate copolymer ( n = 1.47-1.50), poly-4-methylpentene-1 (n = 1.46), ethylene / vinyl acetate copolymer (n = 1.46-1.50), polycarbonate (n = 1) .50 to 1.57), polyvinylidene fluoride (n = 1.42), vinylidene fluoride / tetrafluoroethylene copolymer (n = 1.42 to 1.46), vinylidene fluoride / tetrafluoroethylene / hexa Examples thereof include a fluoropropene copolymer (n = 1.40 to 1.46) and a polyfluorinated alkyl (meth) acrylate polymer.

  In order to adjust the viscosity, it is preferable to use a polymer having the same refractive index in each layer because a plastic optical transmission body having a continuous refractive index distribution from the center toward the outer periphery can be obtained. In particular, polymethylmethacrylate is excellent in transparency and has a high refractive index, so that it is suitable as a polymer for use in preparing the gradient index optical transmission body of the present invention.

  In order to cure the filament formed from the uncured material, a heat curing catalyst or a photocuring catalyst is added to the uncured material, and heat treatment and / or photocuring treatment is performed. As the thermosetting catalyst, a peroxide-based or azo-based catalyst or the like is used. Photocuring catalysts include benzophenone, benzoin alkyl ether, 4'-isopropyl-2-hydroxy-2-methylpropiophenone, 1-hydroxycyclohexyl phenyl ketone, benzylmethyl ketal, 2,2-diethoxyacetophenone, chlorothioxanthone, thioxanthone Compounds, benzophenone compounds, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, N-methyldiethanolamine, triethylamine and the like.

  The photocuring treatment can be performed by irradiating an uncured material containing a photocatalyst with ultraviolet rays from the surroundings. Examples of the light source used for the photocuring treatment include a carbon arc lamp that generates light having a wavelength of 150 to 600 nm, a high-pressure mercury lamp, a medium-pressure mercury lamp, a low-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a chemical lamp, a xenon lamp, and a laser beam. Further, these light sources may be used in appropriate combination in order to increase the polymerization rate.

The thermosetting treatment is performed by heat-treating an uncured material containing a thermosetting catalyst by a heat treatment in a curing processing section such as a heating furnace controlled at a constant temperature for a predetermined time. It may be performed continuously. Moreover, the heating and stretching step and the relaxation step may be performed continuously or may be performed separately for each step.
The rod lens yarn thus obtained may be continuously cut to a desired length, or may be cut after being wound on a bobbin or the like.

Next, the lens array of the present invention will be described.
As shown in FIG. 2, the lens array of the present invention has two substrates 5 so that the optical axes of the rod lenses 7 and 8 of the present invention are parallel to each other. Arranged in one or more rows in between. An adhesive 6 or the like is used for fixing the rod lenses 7 and 8 and the substrate 5. The adjacent rod lenses 7 and 8 may be in close contact with each other, or may be arranged with a certain gap. Further, in the case of a lens array in which the same kind of rod lenses are stacked and arranged in two or more stages, it is preferable that they are arranged in a stacked manner so that the gap between the rod lenses is minimized.

  In the lens array of this invention, you may comprise using the 2 or more types of rod lens which has the 2nd light absorption layer which absorbs the light of a specific wavelength. In this case, the rod lens formed with the second light absorption layer containing the light absorber that absorbs the light having the wavelength B, and the second light absorption layer containing the light absorber that absorbs the light having the wavelength R It is preferable to use two or more types of rod lenses including a rod lens formed with a difference in the light to be transmitted for each rod lens because the resolution for each wavelength of R, G, and B can be improved. .

  In particular, the rod lens when the light transmittance at the R wavelength is 5 times or more of the light transmittance at the B wavelength, and the rod lens when the light transmittance at the B wavelength is 5 times or more the light transmittance at the R wavelength. It is preferable to include. By using such two types of rod lenses, light of R or B wavelength can be efficiently cut, and two or more types of rod lenses having a second light absorption layer that absorbs a specific wavelength are used. In the lens array, the resolution for each of the R, G, and B wavelengths can be increased, and a color image that does not blur the image can be read, written, displayed, and the like.

  In the present invention, when the lens array is composed of two types of rod lenses, as shown in FIG. 2, a rod lens 7 having a second light absorption layer containing a light absorber that absorbs light having a wavelength of B is formed. A rod lens 8 having a second light absorption layer containing a light absorber that absorbs light of R wavelength (the light amount transmittance of R wavelength is not less than 5 times the light transmittance of B wavelength). It is preferable that the light amount transmittance at the B wavelength is at least five times the light amount transmittance at the R wavelength. By constructing a lens array with such two types of rod lenses 7 and 8, light transmitted by the rod lens 7 (transmits light of R wavelength) and the rod lens 8 (transmits light of B wavelength). This is preferable because the resolution for each wavelength of R, G, and B can be improved. In this case, since the G wavelength light is a wavelength between the R wavelength and the B wavelength, either one or both of the rod lens 7 and the rod lens 8 are transmitted.

  Of these two types of rod lenses, it is preferable that the transmittance of light of the G wavelength of one rod lens is 5 times or more of the other, because the color characteristics can be improved. In this case, the transmission wavelength of one lens is R, G (or B, G), and the transmission wavelength of the other lens is B (or R).

  In this way, even when two types of rod lenses are included, each rod lens length is usually processed so as to be constant. For this reason, it is preferable that the conjugate lengths Tc of the two types of lenses at the R, G, and B wavelengths are substantially the same. That is, the refractive index distribution constant g at the average wavelength (intermediate wavelength) of R and G (or G and B) of one rod lens and the refractive index at the wavelength of B (or R) of the other rod lens. It is preferable that the distribution constant g is substantially the same. By combining the refractive index distribution constants g in this way, the conjugate length Tc for each wavelength of R, G, and B of the lens array can be made substantially the same, and color characteristics are good even if a rod lens with large chromatic aberration is used. A lens array can be obtained.

  In the lens array of the present invention, the arrangement pattern of the rod lenses when two or more kinds of the rod lenses of the present invention are used is not particularly limited, but when the diameters of the rod lenses are greatly different, the rods having different diameters in the same row If there is a lens, the arrangement will be disturbed and the resolution and color characteristics will be reduced.Therefore, each rod lens array is formed only with the same type of rod lens, and a plurality of types are periodically arranged for each rod lens array. It is preferable to arrange the rod lens rows so as to be repeated. In this case, the arrangement pattern between the rod lens rows need not be stacked. On the other hand, when the diameters of the rod lenses are substantially the same, a plurality of types of rod lenses may be periodically repeated within one rod lens array. In such a case, the arrangement pattern between the rod lens rows is preferably stacked.

  The substrate constituting the lens array of the present invention may have a flat plate shape, or may have a U-shaped or V-shaped groove for arranging and storing rod lenses at regular intervals. Although the material of a board | substrate is not specifically limited, It is preferable that it is a material easy to process in the process of producing a lens array. As the material for the substrate, various thermoplastic resins, various thermosetting resins, and the like are preferable, and acrylic resins, ABS resins, polyimide resins, liquid crystal polymers, epoxy resins, and the like are particularly preferable. Further, as the base material and reinforcing material of the substrate, fibers or paper may be used, or a release agent, a dye, a pigment, or the like may be added to the substrate.

  The lens array of the present invention can be manufactured, for example, by the following method. First, the rod lenses cut to a certain length are fixed so that the rod lenses are in close contact with each other between the two substrates so that the central axes of the rod lenses are arranged substantially in parallel. In this state, an adhesive containing a light-shielding agent such as carbon black is injected into the gap formed between the rod lenses and between the rod lens and the substrate and cured. Then, this lens array is cut into a desired length, and the end surface is mirrored by a method such as cutting with a diamond blade.

  Since the lens array of the present invention uses a rod lens having a filter function in which a second light absorption layer is formed on each rod lens, it can absorb light of an unnecessary wavelength and has a high resolution. It becomes an array. Further, in the lens array using the two or more types of rod lenses in which the second light absorption layers having different wavelengths to be absorbed according to the present invention are formed, the conjugate length Tc at each of the R, G, and B wavelengths can be substantially matched. , R, G, B Lens array with excellent resolution and high color characteristics for each wavelength. Furthermore, since the lens array of the present invention uses a rod lens in which a first light absorption layer that absorbs light of each wavelength of R, G, and B is formed on the outer peripheral portion, resolution by flare light and crosstalk light is used. Thus, a high-performance lens array excellent in color characteristics with high resolution for each wavelength of R, G, and B is obtained.

Hereinafter, the present invention will be described specifically by way of examples.
In the examples, the refractive index distribution was measured by a known method using an Interfaco interference microscope manufactured by Carl Zeiss.

＜実施例１＞ In addition, the resolution is measured by making light from a light source incident on a grating having a spatial frequency of 4 (line pair / mm, Lp / mm), a rod lens polished on both ends perpendicular to the optical axis, and a lens array through the grating pattern. The lattice image is read by a CCD line sensor installed on the image plane, the maximum (imax) and minimum (imin) of the measured light intensity are measured, and MTF (Moderation Transfer Function) is calculated by the following equation (3). Asked. Here, the spatial frequency indicates a combination of white lines and black lines as one line, and indicates how many combinations of these lines are provided within a width of 1 mm.

<Example 1>

Polymethyl methacrylate ([η] = 0.40, measured in MEK at 25 ° C., the same polymethyl methacrylate was used in the following Examples and Comparative Examples) 47 parts by mass, tricyclo [5 .2.1.0 ^2,6 ] 30 parts by mass of decanyl methacrylate, 23 parts by mass of methyl methacrylate, 0.25 part by mass of 1-hydroxycyclohexyl phenyl ketone and 0.1 part by mass of hydroquinone were heated and kneaded at 70 ° C. A single layer forming stock solution was obtained.

50 parts by mass of polymethyl methacrylate, 10 parts by mass of tricyclo [5.2.1.0 ^2,6 ] decanyl methacrylate, 40 parts by mass of methyl methacrylate, 0.25 parts by mass of 1-hydroxycyclohexyl phenyl ketone and 0.1 part by mass of hydroquinone The part was heated and kneaded at 70 ° C. to obtain a second layer forming stock solution.
50 parts by mass of polymethyl methacrylate, 10 parts by mass of 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, 40 parts by mass of methyl methacrylate, 0.25 parts by mass of 1-hydroxycyclohexyl phenyl ketone, hydroquinone 0.1 parts by mass was heated and kneaded at 70 ° C. to obtain a third layer forming stock solution.

50 parts by mass of polymethyl methacrylate, 10 parts by mass of 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, 40 parts by mass of methyl methacrylate, 0.25 parts by mass of 1-hydroxycyclohexyl phenyl ketone, hydroquinone 0.1 parts by mass was heated and kneaded at 70 ° C. to obtain a fourth layer forming stock solution.
42 parts by mass of polymethyl methacrylate, 18 parts by mass of methyl methacrylate, 40 parts by mass of 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, 0.25 parts by mass of 1-hydroxycyclohexyl phenyl ketone, hydroquinone 0.1 parts by mass was heated and kneaded at 70 ° C. to obtain a fifth layer forming stock solution.

  In addition, the dye Blue 4G (Mitsubishi Chemical Co., Ltd., maximum absorption wavelength 676 nm) 0.006 mass% was added to each undiluted solution for the first layer, the second layer, and the third layer before heating and kneading. . Further, the dye Blue ACR (manufactured by Nippon Kayaku Co., Ltd., maximum absorption wavelength: 616 nm, 576 nm) 0.12% by mass in the respective stock solutions for the fourth layer and the fifth layer before heating and kneading, dye MS Yellow HD-180 (Mitsui Dye, maximum absorption wavelength 433 nm) 0.10% by mass, Dye MS Magenta HM-1450 (Mitsui Dye, maximum absorption wavelength 520 nm) 0.08% by mass, Dye Blue 4G 0.012 mass % Was added.

  These five types of stock solutions were sequentially arranged from the center so that the refractive index after curing was lowered, and were simultaneously extruded from a concentric five-layer composite prevention nozzle. The temperature of the composite spinning nozzle was 54 ° C. The ejection ratio of each layer is converted into the ratio of the thickness of each layer in the radial direction of the lens (the radius in the first layer). First layer / 2nd layer / 3rd layer / 4th layer / 5th layer = 18/50/26/5/1.

Next, the filaments extruded from the composite spinning nozzle are taken up by a nip roller (300 cm / min), passed through a 30 cm-long interdiffusion treatment section, and subsequently 18 chemical lamps of 120 cm in length and 40 W in the central axis. The filamentous body is passed over the center of the first curing processing section (first light irradiation section) arranged at equal intervals around the periphery, and then three 2 kW high-pressure mercury lamps are arranged at equal intervals around the central axis. The filamentous body was passed through the center of the second curing treatment section (second light irradiation section) thus cured. The nitrogen flow rate in the interdiffusion treatment part was 72 L / min. The radius of the obtained lens yarn was 0.24 mm.
The lens yarn was stretched 2.2 times in an atmosphere of 135 ° C., and subjected to relaxation treatment so that the relaxation rate was 10/11 in an atmosphere of 150 ° C.

The obtained rod lens has a radius of 0.172 mm, a center refractive index of 1.497, and a refractive index distribution approximately approximated to the above formula (1) in the range of 0.2r to 0.9r from the central axis toward the outer periphery. The refractive index distribution constant g was 0.837 mm ⁻¹ at a wavelength of 525 nm. In addition, a black layer in which the dye is present approximately uniformly in a thickness of about 10 μm from the outer peripheral surface of the rod lens toward the center, and a dye in a range of about 162 μm in the radial direction including the center axis toward the outer periphery. A blue layer was formed. There were no areas without dye in the lens.

The obtained rod lens was cut with a diamond blade so that both end surfaces thereof were mirror surfaces with a surface perpendicular to the central axis to a lens length of 4.4 mm. This rod lens had conjugate lengths Tc of 10.46 mm, 10.15 mm, and 9.84 mm at R, G, and B wavelengths of 630 nm, 525 nm, and 470 nm, respectively, and the difference in conjugate length Tc was 0.6 mm. Further, this rod lens hardly transmitted light having a wavelength of 630 nm (R), and the light amount transmittance at a wavelength of 470 nm (B) was 5 times or more than the light amount transmittance at a wavelength of 630 nm (R).
<Example 2>

  660 rod lenses before mirror cutting obtained in Example 1 were arranged in parallel in a row between two phenolic resin substrates (thickness 0.5 mm), and an adhesive (carbon black 2) was placed in the gap between them. Somar Epiform with added mass%) was filled, and the adhesive between the lens and between the lens and the substrate was cured. Thereafter, both end faces were cut and mirror-cut with a diamond blade in the same manner as in Example 1 to produce an A4 size (width 227 mm) rod lens array with a lens length of 4.4 mm. This rod lens array had Tc of 10.46 mm, 10.15 mm, and 9.84 mm at R, G, and B wavelengths of 630 nm, 525 nm, and 470 nm, respectively, and the difference in conjugate length Tc was 0.62 mm.

The MTF at 12 Lp / mm measured with this rod lens array fixed at Tc = 10.0 mm was 77.1% at a wavelength of 470 nm and 77.3% at a wavelength of 525 nm. At a wavelength of 630 nm, the amount of transmitted light was small (most of the light was absorbed by the dye in the lens), so measurement was not possible. In this rod lens array, flare light and crosstalk light were hardly observed at wavelengths of 470 nm and 525 nm.
<Example 3>

  In each undiluted solution for the first layer, the second layer, and the third layer before heating and kneading, 0.014% by mass of dye HM-1450 and 0 of dye HD-180 are used instead of the dye Blue 4G. A rod lens was obtained in the same manner as in Example 1 except that 0.003 mass% was added and the radius of the rod lens was changed to 0.170 mm.

The obtained rod lens has a radius of 0.170 mm, a center refractive index of 1.497, and a refractive index distribution approximated by the equation (1) in the range of 0.2r to 0.9r from the central axis toward the outer periphery, and is 525 nm. The refractive index distribution constant g was 0.846 mm ⁻¹ at the wavelength of. In addition, a black layer in which the dye is present approximately uniformly in a thickness of about 10 μm from the outer peripheral surface of the rod lens toward the center, and a dye in a range of about 160 μm in the radial direction including the center axis toward the outer periphery. A red layer was formed. There were no areas without dye in the lens.

The obtained rod lens was cut with a diamond blade so that both end surfaces thereof were mirror surfaces with a surface perpendicular to the central axis to a lens length of 4.4 mm. This rod lens had conjugate lengths Tc of 10.00 mm, 9.72 mm, and 9.44 mm at R, G, and B wavelengths of 630 nm, 525 nm, and 470 nm, and the difference in conjugate length Tc was 0.56 mm. This rod lens hardly transmits light having a wavelength of 470 nm (B) and a wavelength of 525 nm (G), and the light amount transmittance at a wavelength of 630 nm (R) was more than five times the light amount transmittance at a wavelength of 470 nm (B). .
<Example 4>

  A rod lens array of A4 size (width 227 mm) having a lens length of 4.4 mm was manufactured in the same manner as in Example 2 using the 667 rod lenses before mirror cutting obtained in Example 3. This rod lens array had Tc of 10.00 mm, 9.72 mm, and 9.44 mm at R, G, and B wavelengths of 630 nm, 525 nm, and 470 nm, respectively, and the difference in conjugate length Tc was 0.56 mm.

The MTF at 12 Lp / mm measured with this rod lens array fixed at Tc = 10.0 mm was 76.3% at a wavelength of 630 nm. Light with wavelengths of 525 nm and 470 nm could not be measured because the amount of transmitted light was small (light was almost absorbed by the dye in the lens). In this rod lens array, flare light and crosstalk light were hardly observed at a wavelength of 630 nm.
<Example 5>

  Using the 660 rod lenses before mirror cutting obtained in Example 1 and the 659 rod lenses before mirror cutting obtained in Example 3, a rod lens having two rod lens rows in the following procedure An array was made. First, the lenses of Example 1 are arranged in parallel in a single row on an arrangement jig to form a first-stage rod lens row, and the rod lenses of Example 3 are arranged so as to be stacked thereon. A second-stage rod lens array is formed. These rod lens arrays are sequentially transferred to a phenol resin substrate (thickness 0.5 mm) using an adhesive or the like so that the stacked state is maintained, and finally two phenol resin substrates are used. A sandwiching body in which two stages of rod lens arrays are stacked in a stack is produced. In the same manner as in Example 2, the gap is filled with an adhesive (an epiform manufactured by Somar with 2% by mass of carbon black), and the adhesive between the lenses and between the lens and the substrate is cured. Thereafter, both end faces were cut and mirror-cut with a diamond blade in the same manner as in Example 1 to produce an A4 size (width 227 mm) rod lens array with a lens length of 4.4 mm.

  In this rod lens array, the first-stage rod lens array hardly transmits light with a wavelength of 630 nm (R), and the second-stage rod lens array has light with a wavelength of 470 nm (B) and a wavelength of 525 nm (G). Almost did not penetrate. In this rod lens array, Tc at R, G, and B wavelengths of 630 nm, 525 nm, and 470 nm were 10.00 mm, 10.15 mm, and 9.84 mm, respectively, and the difference in conjugate length Tc was 0.31 mm.

The MTF at 12 Lp / mm measured with this rod lens array fixed at Tc = 10.0 mm was 75.4%, 76.2%, 76.7 at R, G, B wavelengths of 630 nm, 525 nm, and 470 nm, respectively. 0%. In this rod lens array, almost no flare light or crosstalk light was observed at R, G, and B wavelengths of 630 nm, 525 nm, and 470 nm.
<Comparative Example 1>

Example 1 except that no dye is added to the whole stock solution in each stock solution for the first layer, the second layer, and the third layer before heating and kneading, and the radius of the rod lens is 0.171 mm. In the same manner, a rod lens was obtained.
The obtained rod lens has a radius of 0.171 mm, a central refractive index of 1.497, and a refractive index distribution approximated by the formula (1) in the range of 0.2r to 0.9r from the central axis toward the outer periphery, and is 525 nm. The refractive index distribution constant g at a wavelength of 0.840 mm ⁻¹ was 0.840 mm ⁻¹ . In addition, a black layer in which the dye was almost uniformly formed in a thickness of about 10 μm from the outer peripheral surface of the rod lens toward the center portion was formed, and no dye was present in other areas in the lens.

The obtained rod lens was cut with a diamond blade so that both end surfaces thereof were mirror surfaces with a surface perpendicular to the central axis to a lens length of 4.4 mm. This rod lens had conjugate lengths Tc of 10.30 mm, 10.00 mm, and 9.70 mm at R, G, and B wavelengths of 630 nm, 525 nm, and 470 nm, respectively, and the difference in conjugate length Tc was 0.6 mm. This rod lens transmitted light with wavelengths of 630 nm, 525 nm, and 470 nm of R, G, and B well, and the light transmittance at wavelengths of 470 nm (B) and 630 nm (R) was comparable.
<Comparative example 2>

  A rod lens array of A4 size (width 227 mm) having a lens length of 4.4 mm was manufactured in the same manner as in Example 2 by using 664 rod lenses before mirror cutting obtained in Comparative Example 1. In this rod lens array, Tc at R, G, and B wavelengths of 630 nm, 525 nm, and 470 nm were 10.30 mm, 10.00 mm, and 9.70 mm, respectively, and the difference in conjugate length Tc was 0.6 mm.

The MTF at 12 Lp / mm measured with this rod lens array fixed at Tc = 10.0 mm was 64.1%, 76.3%, and 65.R at R, G, and B wavelengths of 630 nm, 525 nm, and 470 nm, respectively. The color characteristics were not good. In this rod lens array, almost no flare light or crosstalk light was observed at R, G, and B wavelengths of 630 nm, 525 nm, and 470 nm.
<Example 6>

For first layer formation, 52 parts by mass of polymethyl methacrylate, 35 parts by mass of benzyl methacrylate, 13 parts by mass of methyl methacrylate, 0.25 parts by mass of 1-hydroxycyclohexyl phenyl ketone and 0.1 part by mass of hydroquinone are heated and kneaded at 70 ° C. The stock solution was used.
48 parts by weight of polymethyl methacrylate, 10 parts by weight of benzyl methacrylate, 35 parts by weight of methyl methacrylate, 7 parts by weight of 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, 0-hydroxyhydroxyphenyl ketone 1 25 parts by mass and 0.1 part by mass of hydroquinone were heated and kneaded at 70 ° C. to obtain a second layer forming stock solution.

47 parts by mass of polymethyl methacrylate, 30 parts by mass of methyl methacrylate, 23 parts by mass of 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, 0.25 parts by mass of 1-hydroxycyclohexyl phenyl ketone, hydroquinone 0.1 parts by mass was heated and kneaded at 70 ° C. to obtain a third layer forming stock solution.
40 parts by weight of polymethyl methacrylate, 18 parts by weight of methyl methacrylate, 42 parts by weight of 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, 0.25 parts by weight of 1-hydroxycyclohexyl phenyl ketone, hydroquinone 0.1 parts by mass was heated and kneaded at 70 ° C. to obtain a fourth layer forming stock solution. 37 parts by mass of polymethyl methacrylate, 4 parts by mass of methyl methacrylate, 59 parts by mass of 2,2,3,3,4,4,5,5-octafluoropentyl methacrylate, 0.25 parts by mass of 1-hydroxycyclohexyl phenyl ketone, hydroquinone 0.1 parts by mass was heated and kneaded at 70 ° C. to obtain a fifth layer forming stock solution.

  In addition, 0.014 mass% of dye HM-1450 and 0.003 mass% of dye HD-180 were added with respect to the whole undiluted | stock solution in each undiluted | stock solution for 1st layers and 2nd layers before heat-kneading. In addition, in each undiluted solution for the third layer, the fourth layer, and the fifth layer before heating and kneading, 0.12% by mass of dye Blue ACR, 0.10% by mass of dye HD-180, and dye 0.08 mass% of HM-1450 and 0.012 mass% of dye Blue 4G were added.

  These five types of stock solutions were sequentially arranged from the center so that the refractive index after curing was lowered, and were simultaneously extruded from a concentric five-layer composite prevention nozzle. The temperature of the composite spinning nozzle was 40 ° C. The ejection ratio of each layer is converted into the ratio of the thickness of each layer in the radial direction of the lens (the radius in the first layer). First layer / 2nd layer / 3rd layer / 4th layer / 5th layer = 35/38/20/6/1. Next, in the same manner as in Example 1, a mutual diffusion treatment and a curing treatment were performed while taking up with a nip roller to obtain a rod lens.

The obtained rod lens has a radius of 0.314 mm, a central refractive index of 1.513, and a refractive index distribution approximated by the formula (1) in the range of 0.2r to 0.8r from the central axis toward the outer periphery, and is 525 nm. The refractive index distribution constant g was 0.851 mm ⁻¹ at the wavelength of. In addition, a black layer in which the dye is present approximately uniformly in a thickness of approximately 85 μm from the outer peripheral surface of the rod lens toward the center, and a dye in a range of approximately 229 μm in the radial direction including the central axis toward the outer periphery. A red layer was formed. There were no areas without dye in the lens.

The obtained rod lens was cut with a diamond blade so that both end surfaces thereof were mirror surfaces with a surface perpendicular to the central axis to a lens length of 4.4 mm. The conjugate lengths Tc of the rod lens at R, G, and B wavelengths of 630 nm, 525 nm, and 470 nm were 10.00 mm, 9.38 mm, and 8.91 mm, and the difference between the conjugate lengths Tc was 1.09 mm. This rod lens hardly transmits light having a wavelength of 470 nm (B) and a wavelength of 525 nm (G), and the light amount transmittance at a wavelength of 630 nm (R) was more than five times the light amount transmittance at a wavelength of 470 nm (B). .
<Example 7>

  A rod lens array of A4 size (width 227 mm) having a lens length of 4.4 mm was manufactured in the same manner as in Example 2 using the 362 rod lenses before mirror cutting obtained in Example 6. This rod lens array had Tc of 10.00 mm, 9.38 mm, and 8.91 mm at R, G, and B wavelengths of 630 nm, 525 nm, and 470 nm, respectively, and the difference in conjugate length Tc was 1.09 mm.

The MTF at 12 Lp / mm measured with this rod lens array fixed at Tc = 10.0 mm was 75.8% at a wavelength of 630 nm. At wavelengths of 525 nm and 470 nm, the amount of transmitted light was small (most of the light was absorbed by the dye in the lens) and measurement was not possible. In this rod lens array, flare light and crosstalk light were hardly observed at a wavelength of 630 nm.
<Example 8>

  Using the 660 rod lenses before mirror cutting obtained in Example 1 and the 362 rod lenses before mirror cutting obtained in Example 6, a rod lens having two rod lens rows in the following procedure An array was made. First, a phenolic resin substrate (thickness 0.5 mm) in which the lenses of Example 1 are arranged in parallel in a row on an arrangement jig and a moisture-curing hot melt adhesive (Sdyne 9607M manufactured by Sekisdyne Co., Ltd.) is applied. And a lens array bonded to one substrate was produced.

  Similarly, the lens array of Example 6 bonded to one substrate is manufactured. These two sets of lens rows are bonded to one substrate, the same adhesive is applied to one lens row, and the other lens rows are bonded together and bonded and cured. At this time, the first and second stage rod lenses are aligned so that the optical axes thereof are parallel to each other. In addition, it cannot be piled up because the lens diameter is different. Thereafter, both end faces were cut and mirror-cut with a diamond blade in the same manner as in Example 1 to produce an A4 size (width 227 mm) rod lens array with a lens length of 4.4 mm.

  In this rod lens array, the first-stage rod lens array hardly transmits light with a wavelength of 630 nm (R), and the second-stage rod lens array has light with a wavelength of 470 nm (B) and a wavelength of 525 nm (G). Almost did not penetrate. In this rod lens array, Tc at R, G, and B wavelengths of 630 nm, 525 nm, and 470 nm were 10.00 mm, 10.15 mm, and 9.84 mm, respectively, and the difference in conjugate length Tc was 0.31 mm.

The MTF at 12 Lp / mm measured with the rod lens array fixed at Tc = 10.0 mm was 75.4%, 75.8%, 75.75 at R, G, B wavelengths of 630 nm, 525 nm, and 470 nm, respectively. It was 6%. In this rod lens array, almost no flare light or crosstalk light was observed at R, G, and B wavelengths of 630 nm, 525 nm, and 470 nm.
<Comparative Example 3>

A rod lens was obtained in the same manner as in Example 1 except that no dye was added to the stock solutions for the fourth layer and the fifth layer before heating and kneading.
The obtained rod lens has a radius of 0.172 mm, a center refractive index of 1.497, and a refractive index distribution approximated by the formula (1) in the range of 0.2r to 0.9r from the central axis toward the outer periphery, and is 525 nm. The refractive index distribution constant g was 0.837 mm ⁻¹ at the wavelength of. In addition, a transparent layer in which the dye does not exist in a thickness of about 10 μm from the outer peripheral surface of the rod lens toward the center, and a dye uniformly exists in a range of about 162 μm in the radial direction including the center axis toward the outer periphery. A blue layer was formed.

The obtained rod lens was cut with a diamond blade so that both end surfaces thereof were mirror surfaces with a surface perpendicular to the central axis to a lens length of 4.4 mm. The conjugate lengths Tc of the rod lens at wavelengths of 630 nm, 525 nm, and 470 nm were 10.45 mm, 10.15 mm, and 9.85 mm, and the difference between the conjugate lengths Tc was 0.6 mm. Further, this rod lens hardly transmitted light having a wavelength of 630 nm (R), and the light amount transmittance at a wavelength of 470 nm (B) was 5 times or more than the light amount transmittance at a wavelength of 630 nm (R).
<Comparative example 4>

  A rod lens array of A4 size (width 227 mm) having a lens length of 4.4 mm was manufactured in the same manner as in Example 2 using 660 rod lenses obtained in Comparative Example 3. In this rod lens array, Tc at R, G, and B wavelengths of 630 nm, 525 nm, and 470 nm were 10.46 mm, 10.15 mm, and 9.84 mm, respectively, and the difference in conjugate length Tc was 0.62 mm.

  The MTF at 12 Lp / mm measured with this rod lens array fixed at Tc = 10.0 mm was 55.8% at a wavelength of 470 nm and 56.4% at a wavelength of 525 nm, which was low due to the influence of crosstalk light and flare light. . At a wavelength of 630 nm, the amount of transmitted light was small (most of the light was absorbed by the dye in the lens) and measurement was not possible.

It is sectional drawing perpendicular | vertical to the central axis of the rod lens of this invention. It is a schematic block diagram of the rod lens array of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rod lens 2 Center axis 3 1st light absorption layer 4 2nd light absorption layer 5 Board | substrate 6 Adhesive layer 7 Rod lens which absorbs the light of the wavelength of R 8 Rod lens which absorbs the light of the wavelength of G and B

Claims (8)

  A rod lens having a refractive index that continuously decreases from the central axis toward the outer peripheral portion, and light of each wavelength of R, G, and B in a predetermined range within 100 μm from the position of the outer peripheral surface toward the central axis. A first light absorption layer including a light absorber that absorbs light, and a light absorber that absorbs light of one or two wavelengths of R, G, and B in a region including the central axis. A rod lens comprising a second light absorption layer.   The rod lens according to claim 1, wherein the first light absorption layer and the second light absorption layer are continuously formed.   3. The rod lens according to claim 1, wherein each of the R, G, and B wavelengths is in a range of 600 to 680 nm, 500 to 590 nm, and 430 to 490 nm, respectively.   4. The rod lens according to claim 3, wherein the second light absorption layer has a light amount transmittance at a wavelength of R that is five times or more a light amount transmittance at a wavelength of B. 5.   4. The rod lens according to claim 3, wherein the second light absorption layer has a light amount transmittance at a wavelength of B of 5 times or more than a light amount transmittance at a wavelength of R. 5.   A rod lens array in which a plurality of rod lenses according to any one of claims 1 to 5 are arranged and fixed so that the central axes of the rod lenses are substantially parallel to each other between two substrates. A rod lens array comprising one row.   A rod lens array in which a plurality of rod lenses according to claim 4 and a plurality of rod lenses according to claim 5 are arranged and fixed between two substrates so that the central axes of the rod lenses are substantially parallel to each other. A rod lens array comprising at least one row.   The rod lens according to claim 4 is arranged and fixed in at least one row of the rod lens rows, and the rod lens according to claim 5 is arranged and fixed in at least one row of the rod lens rows. The rod lens array according to claim 7.

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