JPH10123670A - Film unit with lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the transmissivity, reduce the flare ratio, and minimize the ghost to improve the imaging performance by setting the number of surfaces having no reflection preventing coating to a specified number or less in a structure having a plurality of lenses or more. SOLUTION: A film unit with lens 10 has a film cartridge 11 on the left side seen from the front, an unexposed film on the right side, a finder on the upper side, and a stroboscopic window on the right upper side. The stroboscope is switchable. A photographing lens L is formed of two lenses, and the first surface S1 of the first lens L1 has a meniscus non-spherical surface in which the convex surface is turned to an object side. A fine pattern by a tool is often produced in the formation of a non-spherical lens metal mold, which often forms a zonal uniform image in backlight. When the reflection preventing coating is applied to the non-spherical surface, an unsightly ghost can be made inconspicuous. The reflection preventing coating is executed to the first surface S1 of the lens L1 with a multilayer of five layers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a lens-equipped film unit which has a photographic lens, is loaded with a film before assembling, and winds up the film for each photographing.

[0002]

2. Description of the Related Art A film unit with a lens is a camera having a photographic lens, a film is loaded in advance at the time of assembling, and the film is wound up for each photographing.

Conventionally, a photographic lens in this film unit with a lens is a simple photographic optical system composed of one lens.

However, a film unit with a lens having a large print size, for example, a post card type, a relatively large panorama size, etc., has become popular. Therefore, a high-precision imaging lens having a high imaging performance has been demanded so as to be suitable for a print size having a high enlargement ratio.

[0005] For this reason, a film unit with a lens having a good image forming performance by correcting the aberration of each lens by forming the photographing lens of the film unit with a lens into two lenses is known.

[0006]

However, the above-mentioned 2
In the case of a taking lens having a single lens configuration, there is a problem that the transmittance T decreases due to reflection on the lens surface and the flare ratio r, which is the ratio of flare to transmitted light, increases as the number of lens components increases. Here, the transmittance T of the conventionally used photographing lens and the flare ratio r with respect to the transmitted light are roughly calculated as shown in Table 1 below. However, this is a value for incident light near the optical axis, and is an approximate value for an acrylic resin (having a refractive index of about 1.49).

[0007]

[Table 1]

As shown in Table 1 above, as the lens configuration of the taking lens increases, the transmittance T decreases and the flare ratio r increases. For this reason, various performances of the photographing lens are reduced. In addition, when the lens configuration of the photographing lens is increased, in addition to the above, for example, it is difficult to obtain good image quality due to the appearance of ghost due to reflection between lens surfaces in shooting in a backlight against a strong light source such as the sun or in a semi-backlit state. Become.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a photographing lens having a high transmittance, a low flare ratio r, a small number of ghosts, and a good imaging performance.
It is to provide a film unit with a lens.

[0010]

In order to solve the above-mentioned problems and to achieve the object, a film unit with a lens according to the present invention has a photographic lens, and a film is previously loaded at the time of assembly. In addition, in a film unit with a lens that winds a film every time a photograph is taken, the photographing lens has a lens configuration of two or more, and the photographing lens has three or less surfaces on which the antireflection coating is not provided. I do.

The reflectance of the lens surface provided with the anti-reflection coating can be set to 1% or less in the visible light range, and the reflection on the surface provided with the anti-reflection coating can be ignored. For example, when there are three refraction surfaces not coated with an anti-reflection coating made of an acrylic resin (having a refractive index of 1.49), the transmittance T is 88.8% as shown in Table 2 below. On the other hand, the flare ratio r that reaches the image surface by reflection through the lens surfaces not coated with an anti-reflection coating is 0.44% as shown in Table 2 above. If the number of lens surfaces without anti-reflection coating is three or less, the flare ratio r can be 0.5% or less, so that the transmittance T of the photographing lens is good, the flare ratio r is low, the ghost is small,
A lens-fitted film unit with good imaging performance.

In the film unit with a lens according to the second aspect of the present invention, the antireflection coating is provided on the first side from the object side.
The first lens is attached to the object side surface of the lens, and the first lens is made of a plastic material.

In the film unit with a lens according to the third aspect of the present invention, the antireflection coating has a single-layer film or a three-layer coating.
It is characterized by being a multilayer film of any one of the five layers.

According to a fourth aspect of the present invention, there is provided a film unit with a lens, wherein the single-layer film of the antireflection coating is a normal-temperature coat. As the room temperature coating, for example, the substance of the film is applied or sprayed in the air, and then the film is coated using a chemical reaction, ultraviolet light or the like.

According to a fifth aspect of the invention, there is provided a film unit with a lens, wherein the taking lens is at least one aspherical lens.

According to a sixth aspect of the present invention, in the film unit with a lens, the photographing lens is made of at least one plastic material.

The lens-equipped film unit according to the present invention is characterized in that when the photographic lens has an F number of F _NO , the conditional expression (1) of 8 ≦ F _NO ≦ 16 is satisfied.

Conditional expression (1) is an optimum F-number value when the lens configuration is two or more and the above-described antireflection coating is performed, and is smaller than the lower limit of conditional expression (1). When the depth of focus of the photographing lens becomes shallower, for example, in the case of a fixed focus lens, the allowable closest distance of the subject becomes longer. When the shutter speed is a fixed first speed, for example, the brightness range of the photographable subject becomes narrow. In addition, it is not preferable because it is affected by so-called light diffraction and affects the focus.

In the film unit with a lens according to the present invention, when the film unit with a lens is a strobe mechanism and a guide number is G _N , 7 ≦ G _N ≦ 11.
The condition (2) is satisfied.

Conditional expression (2) indicates that the lens configuration has two or more lenses.
In addition, when the above-mentioned anti-reflection coating is performed with the optimum strobe guide number, and is less than the lower limit value of the conditional expression (2), the irradiation distance of the strobe light becomes short.
When the value exceeds the upper limit of conditional expression (2), the size of the strobe tube and condenser of the strobe becomes large, and there is a problem that the camera becomes large.

As used herein, the antireflection coating refers to a process of applying a thin dielectric film to the surface of the taking lens in order to reduce the surface reflection of the taking lens and increase the light transmitted through the taking lens system.

The plastic material means an optical material such as an acrylic resin of a transparent plastic used for the taking lens.

The F number is a value obtained by quantifying the brightness and aperture value of the photographing lens. If F _NO is the F number, f is the focal length, and D is the effective aperture of the lens, F _NO = f /
D means the one represented by the relation.

The guide number G _N is a value that practically indicates the light quantity of the photographic flash light source. G _N is the guide number, F _NO is the F number of the proper exposure, and d is the irradiation distance (m). Then, it means that represented by G _N = F _NO × d.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a film unit with a lens according to the present invention will be described with reference to the drawings.

The "transmittance T" used in the description of the embodiment means that the light flux entering the lens is represented by t1 and the light flux transmitted therethrough is represented by t2, and is represented by a transmittance T = t2 / t1.
Further, “flare V” is a ratio of a light beam reaching a screen due to reflection twice or four times between surfaces with respect to an incident light beam, and “flare ratio r” is a flare light beam relative to a transmitted light beam. And the ratio of the transmittance T to the flare V, that is, r = V / T. Further, the “T number” is a number in which the transmittance T of the lens is taken into account, and is a value indicating how much the F number of the image of the taking lens corresponds to the F number having the transmittance T of 100%. _NO = F√ (100
/ Transmittance T (%)).

(Embodiment 1) This embodiment is an embodiment including three surfaces of a photographic lens which are not coated with an antireflection coating. As a comparative example, a description will be given in comparison with an example in which the entire surface of the photographing lens is not coated with an anti-reflection coating. FIG. 1 is a sectional view (a) of an optical axis and a front view (b) of a film unit with a lens according to the present invention, and FIG. 2 is an optical sectional view of a two-piece photographing lens according to the present invention. Is the flare and flare ratio r of the anti-reflective coating
FIG.

In FIG. 1, a film unit 10 with a lens
There is a film cartridge 11 on the left side when viewed from the front and an unexposed film 12 on the right side. Further, there is a finder 13 on the upper side and a flash window 14 on the upper right side. The strobe can be switched.

The taking lens L has a two-lens configuration, and the first lens L1 has a meniscus aspherical surface with the first surface S1 facing the object side convex surface. The aspherical surface may have a fine pattern formed by a tool when the lens mold is formed, and may result in a non-uniform image in the form of an annular zone at the time of backlight. In particular, if you apply an anti-reflection coating on the aspherical surface,
Unsightly ghosts can be made less noticeable. Here, Table 2 shows the lens configuration, optical material, and coating surface of the taking lens.

[0030]

[Table 2]

Next, as the anti-reflection coating, a five-layer anti-reflection coating shown in Table 3 is applied to the first surface S1.

[0032]

[Table 3]

In Table 3, the mixture indicates a mixture of zirconium oxide and titanium oxide, and the layer numbers are given from the lens side. With an anti-reflective coating,
In addition to improving the transmittance T of the lens and the flare ratio r,
In the case of a plastic material, static electricity can be prevented and scattered light due to dust can be prevented.

As shown in Table 2 above, in the comparison of the transmittance T, the embodiment is superior to the comparative example, and the flare ratio r of the embodiment is superior to the comparative example.

Here, the calculation of the transmittance T and the flare ratio r in the embodiment of Table 2 will be described with reference to FIG. In the figure, R1, R2, and R3 are reflection surfaces of the taking lens L that are not coated with an anti-reflection coating. Assuming that the refractive index of the surface without the anti-reflection coating is n, the refractive index of the lens material is R = ｛(n−1) / (n +
1)｝ ² , and the transmittance T is T = 1−R = 1 − ｛(n−
1) / (n + 1)｝ ² (absorption is negligible). Therefore, the antireflection uncoated refracting surface is 3
If there are surfaces, it is considered that only three reflection surfaces are present. here,
Assuming that the lens material is acrylic, the refractive index n = 1.49, the reflectance and the transmittance on each surface are R = 0.0387, T = 0.
9613. Therefore, the transmittance of the entire lens system T is represented by T ^3, the T ³ = 0.888. Also, the light reflected on the second or third surface reaches the screen by an even number of times of reflection and becomes a flare. Assuming that the flare V is reflected twice, V = (2T ³ + T ⁵ ) R ² = 0.004 = 0.
4%, and the flare ratio r is r = V / T ³ = (2
+ T ² ) R ² = 0.0044 = 0.44%.

According to the present invention, there is provided a film unit with a lens having a good photographing lens having a good transmittance T and a small flare ratio r.

As another example, the F number is represented by F _NO =
Assuming that all the lens surfaces are coated with an anti-reflection coating, the transmittance T is approximately 100%, the T number is T _NO = F _NO , and T _NO = 8. Here, as compared with the case where the antireflection coating is not performed by two constituent lenses with the same F number, the transmittance T is 85 = 4% as shown in Table 1 described above. When the F number is F _NO = 8, the T number is T _NO = 8.7.
Becomes Therefore, in the case of the first shutter speed, the appropriate subject luminance range is narrowed.

As another example, if the anti-reflection coating is applied to all the lens surfaces by the strobe mechanism, if the guide number is G _N = 9, and if the film sensitivity is ISO800, the arrival of the strobe light The distance is 2.7
m, and a slight underexposure can be corrected at the time of printing. Therefore, in practice, the strobe light reaches up to 3 m, which is sufficient for general photographing. For comparison, the same guide number G
_{If N} = 9 and no anti-reflection coating is applied to all surfaces, the T number of the photographing lens becomes 10.3, and the reach of the strobe light is short, 2.5 m. Further, the size of the external appearance of the film unit with a lens will be described. In the case of a strobe having a guide number of G _N = 9, a strobe having a capacitor of about 100 μF can be used. This capacitor has a diameter of φ = 10 and a length of 37.5 m
m. This time, the guide number is G _N
= 10.8 strobe 150μF capacitor has diameter φ
15 gives a length of 37.5 mm. The diameter can be reduced by 5 mm, and the size of the camera body can be reduced.

(Embodiment 2) This embodiment is an embodiment in which all surfaces of a two-element photographic lens are coated with a multilayer antireflection coating. As a comparative example, a description will be given in comparison with an example in which the entire surface of the taking lens is not coated with an anti-reflection coating. FIG. 4 is a spectral transmittance curve of the taking lens when a multilayer antireflection coating is applied. Table 4 shows the lens configuration, the optical material, the coating surface, the transmittance T, and the flare ratio r at this time.

[0040]

[Table 4]

Table 3 shows the medium and film thickness of the multilayer antireflection coating. In this case, the spectral transmittance of the photographing lens is as shown in FIG.
When the transmittance T of nm is used, the F number 9.5 of the photographing lens becomes 9.6 in the T number. The flare ratio r is 0.01%.

As shown in Table 4, in the comparison of the transmittance T, the example is superior to the comparative example, and the flare ratio r to the transmittance is also superior in the example compared to the comparative example. According to the present invention, a lens-equipped film unit having a good photographing lens having a good transmittance T and a small flare ratio r is provided.

(Embodiment 3) This embodiment is an embodiment in which all surfaces of a two-element photographic lens are coated with a single-layer anti-reflection coating. As a comparative example, a description will be given in comparison with an example in which the entire surface of the taking lens is not coated with an anti-reflection coating. FIG. 5 is a spectral transmittance curve of the taking lens when a single-layer antireflection coating is applied. Table 5 shows the lens configuration of the taking lens, the optical material, the coating surface, and the transmittance T and the flare ratio r at this time.

[0044]

[Table 5]

FIG. 5 shows a spectral transmittance curve of the photographing lens in this case. In addition, a wavelength of 546 nm
Using the transmittance T of F, the F number of the taking lens becomes F _NO =
The T number is 9.8 compared to 9.5.

Table 6 shows the medium and film thickness of the single-layer antireflection coating.

[0047]

[Table 6]

The antireflection coating may be applied in air at room temperature. The change in reflectivity due to the change in the film thickness of the anti-reflection coating is relatively small, and the effective diameter of the lens is small in the filmed lens of the lens, so the change in reflectivity is not noticeable even if the film thickness is uneven. . Therefore, it is easy to control the film thickness, and even without using a vacuum evaporation apparatus or the like, even if the material that forms the film is applied or sprayed in air, and then the film is formed using a chemical reaction, ultraviolet light, or the like. good.

As shown in Table 5, in the comparison of the transmittance T, the example is superior to the comparative example, and the flare ratio r to the transmittance is also superior in the example compared to the comparative example. ADVANTAGE OF THE INVENTION According to this invention, it becomes a film unit with a lens which has a favorable transmittance | permeability and a favorable imaging lens with a small flare ratio r.

(Embodiment 4) This embodiment is an embodiment in which the photographic lens has two surfaces which are not coated with an antireflection coating. In addition, as a comparative example, all the surfaces of the photographing lens are
This is a comparative example in the case where an antireflection coating is not provided. Table 7 shows the lens configuration, optical material, coating surface, transmittance T and flare ratio r of the taking lens.

[0051]

[Table 7]

As shown in Table 7, in the comparison of the transmittance T, the example is superior to the comparative example, and the flare ratio r with respect to the transmittance is also superior in the example compared to the comparative example. According to the present invention, a lens-equipped film unit having a good photographing lens having a good transmittance T and a small flare ratio r is provided.

[0053]

According to the above configuration, the following effects can be obtained.

According to a first aspect of the present invention, there is provided a film unit with a lens having a photographing lens, in which a film is loaded in advance at the time of assembling, and the film is wound up for each photographing, wherein the photographing lens has two or more lenses. The surface where the anti-reflection coating is not applied to the taking lens is 3
Since it is equal to or less than the surface, a film unit with a lens having a high transmittance of the taking lens, a low flare ratio r, a small number of ghosts, and a good imaging performance is obtained.

According to the second aspect of the present invention, the anti-reflection coating is applied to the object side surface of the first lens from the object side, and the first lens is made of a plastic material. It prevents electricity, prevents scratches on the lens, prevents ghosting due to dust, and hardly causes dust.

According to the third aspect of the present invention, the antireflection coating is a single-layer film or a multilayer film of any one of three to five layers. The rate is good, and the antireflection coating is hard to peel off.

According to the fourth aspect of the present invention, since the single-layer film of the antireflection coating is a normal temperature coat, the cost can be easily reduced.

According to the fifth aspect of the present invention, since the photographing lens is at least one aspherical lens, aberration correction of the lens is improved.

According to the invention of claim 6, since the taking lens is made of at least one plastic material, the cost can be reduced.

According to the seventh aspect of the present invention, the F-number of the photographic lens satisfies the condition of 8 ≦ F _NO ≦ 16 when the F-number is F _NO , so that the F-number is optimal for a film unit with a lens.

According to an eighth aspect of the present invention, when the film unit with a lens has a built-in strobe and the guide number is G _N , the condition of 7 ≦ G _N ≦ 11 is satisfied. Becomes

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a film unit with a lens according to the present invention.

FIG. 2 is an optical cross-sectional view of a two-piece photographing lens according to the present invention.

FIG. 3 is an explanatory diagram of a flare and a flare ratio of an antireflection coating.

FIG. 4 is a spectral transmittance curve of a photographic lens when a multilayer antireflection coating is applied.

FIG. 5 is a spectral transmittance curve of a taking lens when a single-layer antireflection coating is applied.

[Explanation of symbols]

Reference Signs List 10 Film unit with lens 11 Film cartridge 12 Unexposed film 13 Viewfinder 14 Strobe window 15 Condenser 16 Shutter 18 Aperture F _NO F number L Shooting lens L1 First lens L2 Second lens G _N guide number S1 1 surface S2 2 surface S3 3 Surface S4 4 Surface T Transmittance

Claims (8)

[Claims] 1. A film unit having a photographic lens, in which a film is loaded in advance at the time of assembling and a film is wound up for each photographing, wherein the photographic lens has two or more lenses and is reflected by the photographic lens. A film unit with a lens, wherein three or less surfaces are not coated for prevention. 2. The film with a lens according to claim 1, wherein the antireflection coating is applied to the object side surface of the first lens from the object side, and the first lens is made of a plastic material. unit. 3. The antireflection coating is a single-layer film,
The film unit with a lens according to claim 1, wherein the film unit is a multilayer film of any one of three to five layers. 4. The method according to claim 3, wherein the single-layer film of the antireflection coating is a coating at room temperature.
The film unit with a lens according to 1. 5. The lens-fitted film unit according to claim 1, wherein the taking lens has at least one aspherical surface. 6. The lens-fitted film unit according to claim 1, wherein said taking lens is made of at least one plastic material. 7. The lens-equipped film unit according to claim 1, wherein the photographic lens satisfies a conditional expression of 8 ≦ F _NO ≦ 16 when an F number is F _NO . 8. comprising the lens-fitted film unit is flash mechanism, when the guide number of the strobe and G _N, according to 6 claim 1, characterized by satisfying the condition of 7 ≦ G _N ≦ 11 Film unit with lens.