JP2000066090A - Photographing lens for fixed focus type camera and fixed focus type camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain sufficient exposure for a subject having low luminance at low cost by making the open F-number of a photographing lens satisfy a specified condition. SOLUTION: This photographing lens is constituted of two lens components and a diaphragm, and satisfies 5.6<F0<8 when it is assumed that the open F-number of the photographing lens is F0. A photographic image plane frame 24 exists nearly in the center of a main body 10, and an unexposed film chamber 22 is arranged on either side and an exposed film chamber 23 is arranged on the other side while putting the frame 24 in between. The photographing lens 11A exists nearly in the center of the main body, and a shutter 19 is provided on the frame 24 side of the lens. A 2nd diaphragm plate AP2 is provided between the lens 11A and the shutter 19, and apertures AP21 and AP22 are provided on the plate AP2. A 1st diaphragm plate AP1 is installed between two lenses of the lens 11A. The lens 11A is a plastic lens constituted so that the refractive index of two lens components on a d-line is <=1.6, for example.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photographing lens for a fixed-focus camera and a fixed-focus camera, and more particularly to a simple and low-cost photographing lens for a fixed-focus camera and a simple and low-cost film unit with a lens. For a fixed focus camera at a price.

[0002]

2. Description of the Related Art In a conventional fixed focus camera, a bright camera having an open F-number of about 5.6 or less is constituted by three or more lenses, and is constituted by a lower cost two-lens construction. This is used in a film unit with a lens and the like. For example, as shown in the examples of JP-A-7-333494 or JP-A-6-258574, the open F number is 8 or more. .

[0003]

In the above conventional example, in a fixed focus camera having an open F-number of 8 or more, even if a high sensitivity film having an ISO sensitivity of 400 to 800 is used, there is no fear of camera shake. At low shutter speeds, we couldn't get enough exposure in the shade, at sunset, or indoors. Also, when a strobe light is used in combination, sufficient exposure can be obtained for a subject at a short distance, but the exposure of a subject at a long distance such as a background is too small, resulting in a photograph completely different from an actual visual impression.

On the other hand, a lens having a bright open F-number is composed of three or more lenses, so that in addition to an increase in material cost, an error in assembling becomes large,
Alternatively, adjustment is required, and when the number of lenses constituting the lens is reduced from two to three, there is a problem that the camera becomes extremely compact or the lens becomes large, and the camera is not compact.

SUMMARY OF THE INVENTION An object of the present invention is to provide a photographing lens for a fixed-focus camera, which is capable of providing a low-cost, low-brightness subject and sufficient exposure even for a low-brightness subject. It is another object of the present invention to provide a fixed focus camera that can obtain sufficient exposure even for a low-cost subject with low luminance using the photographing lens.

[0006]

The above object can be achieved by the following (Solution 1) or (Solution 2).

[0007] (SOLUTION 1) photographing lens for fixed focus camera of the present invention is made of a diaphragm and two lens components, and, when the open F-number of the taking lens and the F _o, the following conditional expression Make a configuration that satisfies you.

5.6 <F _o <8 (1) More preferably, when the half angle of view of the photographing lens is ω and the focal length of the photographing lens is f, the following conditional expression is satisfied. I do.

5 <f / (F _o · tan ω) <7 (2) Alternatively, more preferably, the spherical aberration of a marginal ray having an F-number of F of the photographing lens is set to SA (F),
When half of the length of the shooting screen in the long side direction is set to y _L , the configuration satisfies the following conditional expression.

[0010] _{-0.072y L <SA (F o /0.7)<-0.024y} L (3) More preferably, the focal length of the first lens component nearest to the object side of the imaging lens is f ₁ At this time, the configuration is such that the following conditional expression is satisfied.

0.4 <f / f ₁ <0.8 (4) Alternatively, more preferably, the first lens component closest to the object side of the taking lens is a positive meniscus lens having a convex surface facing the object side. Assuming that the radius of curvature of the object-side refracting surface of the first lens component is r ₁ and the focal length of the taking lens is f, the following conditional expression is satisfied.

0.12 <r ₁ /f<0.23 (5) Alternatively, more preferably, the first lens component closest to the object side of the taking lens is a positive meniscus lens having a convex surface facing the object side, At least one of the two refracting surfaces of the first lens component has an aspheric surface, and the first lens component has a first F at a height at which a marginal ray having an open F-number passes through each surface.
Assuming that the amount of aspherical displacement of the surface and the second surface is Δx ₁ and Δx ₂ and the focal length of the photographic lens is f, the following conditional expression is satisfied.

However, each aspherical displacement amount defines a displacement facing the image plane as positive.

-0.0004 <(Δx ₁ -Δx ₂ ) / f <−0.00005 (6) More preferably, the first lens component closest to the object side of the taking lens has a positive surface with the convex surface facing the object side. The first lens component has an aspheric surface in which the positive aspheric displacement increases as the image-side surface of the first lens component moves away from the optical axis.

More preferably, at least one stop is provided on the image side of the photographing lens, and the first lens component closest to the object side of the photographing lens comprises a positive meniscus lens having a convex surface facing the object side. When the distance from the image-side refracting surface of one lens component to the diaphragm closest to the image is X, and the focal length of the taking lens is f, the following conditional expression is satisfied.

0.07 <X / f <0.15 (7) Alternatively, a first lens component that satisfies the conditional expression (1), wherein the first lens component has a positive refractive power from the object side, A first aperture, a second lens component having a convex surface facing the image surface side, and a second aperture, wherein the aperture diameter of the second aperture is variable or close to the second aperture, and the aperture diameters are different. A third aperture is inserted to make the lens aperture diameter variable.

[0017] More desirably, a second lens component of the imaging lens, the distance of the second diaphragm and D _a, the focal length of the photographing lens is f, a configuration satisfying the following condition.

0 <D _a /f<0.07 (8) More preferably, in the fixed focus camera provided with the above-described photographing lens for a fixed focus camera and a flash, a switch of an artificial light emitter (also referred to as a flash) The F-number of the taking lens changes in conjunction with ON and OFF, and the F-number of the taking lens when the switch is ON is _Fo, and the F-number when the switch is OFF is _Foff . Then, a fixed-focus camera that satisfies the following conditional expression is obtained.

0.4 <F _o / F _off <0.7 (9) More preferably, in the above-mentioned fixed focus camera, the F-number of the taking lens is such that the spherical aberration of the F marginal ray is SA (F). When half of the length of the photographing screen in the long side direction is y _L , the configuration satisfies the following conditional expression.

−0.008F _off · y _L <SA (F _o ) <− 0.003F _off · y _L (10) and −0.072y _L <SA (F _o /0.7)<−0.024y _L (3) More preferably, in the above-mentioned fixed-focus camera or the photographic lens for a fixed-focus camera, all of the two lens components of the photographic lens have a refractive index at d-line of 1.6 or less. It consists of.

In the above configuration, each conditional expression will be described. First, when the value exceeds the upper limit of the conditional expression (1), sufficient exposure for a low-luminance subject cannot be obtained,
Alternatively, exposure of a subject at a long distance where the illuminance by the strobe light is reduced, such as a background when the strobe is used indoors, is insufficient, and a good quality photograph cannot be obtained. On the other hand, when the value goes below the lower limit of the conditional expression (1), the two lenses cannot sufficiently correct various aberrations including the spherical aberration, and the depth of focus becomes too shallow. The back focus error and the mounting error at the time of mounting the lens are too large, which often results in a photograph with poor focus.

When a photographic lens is formed by using three lenses, if the respective lenses are not provided with an anti-reflection coating, the transmitted light becomes about 79% of the light incident on the lens, and 2% on the refracting surface. The ratio of flare light that reaches the screen after being reflected more than once reaches 2.2% of the transmitted light, which is undesirable. To prevent this, it is necessary to coat at least one lens with an anti-reflection coating, and cost increases can be avoided. Absent. on the other hand,
In the case of two lenses, even without applying an anti-reflection coat,
The transmitted light is about 85%, and the flare light is
It is as small as 0.86%, which is sufficient. Therefore, the lens
Constructing with one piece is cost and lens performance comprehensive,
It is most suitable as a shooting lens for a low-cost camera.

Conditional expression (2) is a condition for obtaining a sufficient depth of field as a fixed focus camera with a taking lens having an open F-number of conditional expression (1). Conditional expression (2)
If the upper limit is exceeded, the depth of field becomes too shallow, whereas if it falls below the lower limit, the lens becomes too wide-angle, and the peripheral light quantity becomes insufficient due to the cosine fourth law, and the effect of the perspective becomes poor. It is not preferable because it tends to be too large and uncomfortable.

In the photographing lens for a fixed focus type camera according to the present invention, it is preferable that the spherical aberration is insufficiently corrected and the conditional expression (3) is satisfied. When the value exceeds the upper limit of conditional expression (3), spherical aberration is excessively corrected, the center focus position approaches the ideal image plane position, and the difference from the focus position of the off-axis light flux, that is, the influence of the field curvature increases, which is preferable. Absent. Below the lower limit of conditional expression (3), the spherical aberration is too large, which is not preferable.

Conditional expression (4) is a condition relating to the refractive power distribution of the two lenses according to the present invention. If the upper limit of conditional expression (4) is exceeded, manufacturing errors such as surface accuracy and eccentricity of the first lens component will occur. When the conditional expression (4) is less than the lower limit of the conditional expression (4), the total lens length is undesirably large. Further, when the first lens component is a meniscus lens having a convex surface facing the object side, it is easy to correct coma aberration, and if the radius of curvature of the first surface is determined so as to satisfy the conditional expression (5), the Petzval sum When the upper limit of conditional expression (5) is exceeded, the Petzval sum becomes too large, and when the F-number is relatively small, the imaging surface such as a film surface is curved. Even if it does, it is not preferable because all the areas in the screen do not enter the depth of focus, and conversely, if the lower limit of conditional expression (5) is exceeded, the first
The optical axis shift between the two refraction surfaces of the lens component undesirably increases the influence on one-sided blur.

When at least one surface of the first lens component is aspherical, various aberrations including spherical aberration can be sufficiently corrected.

Conditional expression (6) is a condition relating to the aspherical surface of the first lens component. If the upper limit of conditional expression (6) is exceeded, the amount of aspherical deformation is insufficient, and spherical aberration and the like cannot be sufficiently corrected. When the value is below the lower limit of the expression (6), unclearness or the like due to eccentricity of the lens easily occurs, which is not preferable. Further, if the image-side surface of the first lens component is an aspheric surface in which the positive aspherical deformation increases as the distance from the optical axis increases, various aberrations can be corrected and the influence of decentering can be reduced. .

Conditional expression (7) is a condition relating to coma aberration and curvature of field. When the first lens component is a positive meniscus lens having a convex surface facing the object side, when the open F-number becomes small, the angle of view becomes low. The difference in coma aberration due to the angle of view becomes remarkable, such as inward coma aberration at the angle of view and outward coma aberration at a high angle of view, and the position of the stop becomes important. Conditional expression (7)
Above the upper limit, the difference in coma is small, but the field curvature is undesirably large, and conversely, below the lower limit,
The difference in coma aberration becomes large, and the image quality is deteriorated particularly at a low angle of view, which is not preferable.

In a lens having a small f-number which satisfies the conditional expression (1), the entrance pupil is large and the marginal ray passes through a portion farther from the optical axis. Although it is strongly affected by scattered light due to an object, that is, an edge of a lens, the second lens having the first lens component having a positive refractive power, the first diaphragm, and the second lens having a convex surface directed toward the image surface side is provided from the object side. If a stop is arranged between the first and second lens components, such as a lens component, the scattered light can be effectively prevented.

The second lens component has a convex surface facing the image side, and a second diaphragm is disposed behind the second lens component. The diameter of the second diaphragm is variable, or the second diaphragm is close to the second diaphragm. By inserting a third stop having a different stop diameter so that the aperture diameter of the lens becomes variable, the first stop and the second lens component of the first lens component can be integrated into a camera, and Since the aperture variable mechanism is independent of the above, the structure and assembly are simple, a camera capable of varying the aperture according to the luminance of the subject can be obtained, and the open F number satisfies the conditional expression (1). When satisfied, it is possible to prevent overexposure of a high-brightness subject such as outdoors in fine weather, and a long-distance subject outdoors can sufficiently enter the depth of field to obtain a favorable result.

If the upper limit of conditional expression (8) is exceeded, the curvature of field will increase, and the outer diameter of the lens, particularly the outer diameter of the first lens component, will increase. Below the lower limit, the variable aperture mechanism is likely to interfere with the lens, which is not preferable.

When the variable aperture is operated in conjunction with a switch of an artificial light emitting mechanism provided in a fixed focus camera and the F-number of the lens is changed so as to satisfy the conditional expression (9), the brightness of the subject becomes large. Exposure will not be over-exposure even in sunny outdoors, and the F-number will be small indoors where the brightness of the subject is insufficient, and the artificial light will reach even if the guide number of the artificial light emission mechanism is relatively small. You can also get enough. If the upper limit of conditional expression (9) is exceeded, the difference between F _o and F _off is too small to obtain a sufficient effect. However, whichever one is selected, it is not preferable because it tends to be inappropriate.

When the photographing lens of the fixed-focus camera is satisfied by the conditional expression (3), various aberrations when the lens is opened can be corrected well as described above.

If conditional expression (10) is further satisfied, an appropriate depth of field can be obtained both when the artificial light emitting mechanism is used and when it is not used. When the upper limit of conditional expression (10) is exceeded, small amount of spherical aberration in the open F-number F _o, small displacement of the best focus position when focused on F _off, when the auxiliary light by the artificial light is so the depth of field to enter the well within reach when opened, It is not preferable because the resolution of the long-distance object when focused on F _off can not be sufficiently improved, the displacement is too large the best focus position when focused on F _off when falls below the lower limit of the inverse of conditional expression (10), F _off In this case, the resolution of the subject at a short distance when the aperture is stopped down is not sufficient.

The photographing lens of the fixed-focus camera has a refractive index at d-line of 1.6 for all two lens components.
If the following plastic lens is used, it can be manufactured by injection molding and can be manufactured at a very low cost. In this case, an acrylic plastic such as PMMA (polymethyl methacrylate) or PC ( Polycarbonate), PS (polystyrene) and the like are preferable because of low material cost.

It should be noted that the artificial light emitting mechanism mentioned here includes all mechanisms for emitting an artificial light source used at the time of photographing.
For example, it refers to instantaneous light emission of a strobe or the like, and is also simply called flash.

(Solution 2) A photographing lens for a fixed focus camera according to the present invention comprises a first lens component having a positive refractive power from the object side, a first stop, and a second lens having a convex surface facing the image plane side. And a second stop, wherein the stop diameter of the first stop is variable, or a third stop having a different stop diameter is inserted close to the first stop to change the aperture diameter of the lens. When the open F-number of the taking lens is F _o , the following conditional expression is satisfied.

5.6 <F _o <8 (11) More preferably, when the half angle of view of the photographic lens is ω and the focal length of the photographic lens is f, the following conditional expression is satisfied: I do.

5 <f / (F _o · tan ω) <7 (12) Alternatively, more preferably, the spherical aberration of the marginal ray of the imaging lens whose F number is F is SA (F),
Assuming that y _L is half of the length in the long side direction of the shooting screen, the following conditional expression is satisfied.

−0.072 y _L <SA (F _o /0.7)<−0.024 y _L (13) More preferably, when the focal length of the first lens component of the photographing lens is f ₁ , Are configured so as to satisfy the conditional expression.

0.4 <f / f ₁ <0.8 (14) Alternatively, more preferably, the first lens component of the taking lens is a positive meniscus lens having a convex surface facing the object side, and the first lens Assuming that the radius of curvature of the refracting surface on the object side of the component is r ₁ and the focal length of the taking lens is f, the following conditional expression is satisfied.

0.12 <r ₁ /f<0.23 (15) Or more preferably, the first lens component of the taking lens is a positive meniscus lens having a convex surface facing the object side, and the first lens is At least one of the two refracting surfaces of the component is an aspheric surface, and the aspherical displacement of the first surface and the second surface at a height at which the marginal ray of the open F number passes through each surface is Δx ₁ , When Δx ₂ is set and the focal length of the taking lens is set to f, the following conditional expression is satisfied.

However, each aspherical displacement is defined as a displacement facing the image plane being positive.

−0.0004 <(Δx ₁ −Δx ₂ ) / f <−0.00005 (16) More preferably, the first lens component of the photographic lens is a positive meniscus lens having a convex surface facing the object side. As the image-side surface of the first lens component moves away from the optical axis,
The aspherical surface is such that the positive aspherical displacement increases.

More preferably, the first lens component of the photographing lens is a positive meniscus lens having a convex surface facing the object side, and the second diaphragm closest to the image side of the image side refraction surface of the first lens component. When the distance to X is X and the focal length of the taking lens is f, the following conditional expression is satisfied.

[0046] 0.07 <X / f <0.15 ( 17) More preferably, the first aperture of the imaging lens, the distance of the second diaphragm and D _S, the focal length of the photographing lens is f At this time, it is configured so as to satisfy the following conditional expression.

[0047] 0.04 <D _S /f<0.1 (18) More preferably, in the fixed focus camera with the above-mentioned fixed focus camera taking lens and artificial light-emitting mechanism, the switch of the artificial light-emitting mechanism On and off, the F-number of the taking lens is changed in conjunction with the off-state, and the F-number of the taking lens when the switch is on is set to _Fo .
When the F-number when the switch is _off is represented as Foff, a fixed focus camera which satisfies the following conditional expression is used.

0.4 <F _o / F _off <0.7 (19) More preferably, in the above fixed focus camera, the spherical aberration of a marginal ray having an F number of F of the photographing lens is set to SA (F). The configuration is such that the following conditional expression is satisfied, where y _L is half of the length in the long side direction of the shooting screen.

−0.008 F _off · y _L <SA (F _o ) <− 0.003 F _off · y _L (20) and −0.072 y _L <SA (F _o /0.7)<−0.024 y _L (13) More preferably, in the above-mentioned fixed-focus camera or fixed-focus camera photographing lens, all of the two lens components of the photographing lens have a refractive index at d-line of 1.6 or less. It consists of.

In the above arrangement, if the aperture diameter of the lens is variable at or near the first stop, the curvature of field follows the change in spherical aberration, and the substantial change in curvature of field due to variable aperture is reduced. be able to.

A description will be given of an eighth embodiment which will be described later. As shown in FIG. 7, when the apertures AP11 and AP12 of the first aperture plate AP1 are switched, light rays passing through the photographing lens are used. The bundle changes,
At the time of opening (A) as shown in the meridional lateral aberration of FIG.
As can be seen from the meridional lateral aberration at the first stop position at the time of stop-down (B), by stopping down, a component of the light beam at the time of opening that has an under image plane does not pass, and the image at the time of stop-down As shown in the lens aberration diagram of FIG. 27, the surface curvature amount becomes smaller than when the lens is opened. On the other hand, the spherical aberration is reduced by narrowing down the aperture, and the best focus position at the center of the screen is farther from the taking lens than when the aperture is open.

Therefore, the substantial amount of curvature of field at the time of stopping down hardly changes from that at the time of opening, and good off-axis performance can be obtained both at the time of opening and at the time of stopping down.
When the film surface is a cylindrical surface having a radius of curvature of 110 mm in Example 8 described later, as shown in FIGS. 29 and 30, good performance can be obtained from the center to the periphery of the screen at each open MTF at each subject distance. . In addition, as shown in FIGS. 31 and 32, good performance can be obtained from the center of the screen to the periphery of the MTF at the time of narrowing down at each subject distance.

Next, each of the conditional expressions will be described. First, if the upper limit of the conditional expression (11) is exceeded, sufficient exposure for a low-luminance subject will not be obtained, and the illuminance due to the strobe light, such as the shade of trees, the background at sunset, or the background when using the strobe indoors, will be reduced. When the exposure of the subject is insufficient and a photograph of good image quality cannot be obtained, on the other hand, when the lower limit of conditional expression (11) is not reached, the two lenses have sufficient aberrations including spherical aberration. In addition, the depth of focus is too shallow, the influence of curvature of field, the error of back focus at the time of manufacturing, and the mounting error at the time of assembling the lens is too large, and it is not preferable that the photograph is often out of focus.

When a photographic lens is formed by using three lenses, unless each lens is provided with an anti-reflection coating, the transmitted light becomes about 79% of the light incident on the lens, and the transmitted light becomes 2% at the refracting surface. The ratio of flare light that reaches the screen after being reflected more than once reaches 2.2% of the transmitted light, which is undesirable. To prevent this, it is necessary to coat at least one lens with an anti-reflection coating, and cost increases can be avoided. Absent. On the other hand, in the case of two lenses, even without the anti-reflection coating, the transmitted light is about 85%, and the flare light is 0.8% of the transmitted light.
It is as small as about 6%, which is sufficient. Therefore, the configuration of two lenses is the most suitable as a photographing lens of a low-priced camera in terms of cost and lens performance.

Conditional expression (12) is a conditional expression (1) which is a condition for obtaining a sufficient depth of field as a fixed focus camera with a taking lens having an open F-number of conditional expression (11).
Above the upper limit of 2), the depth of field becomes too shallow, and below the lower limit, the lens becomes too wide and cosine 4
It is not preferable because the peripheral light quantity is insufficient due to the influence of the power law, and the effect of the perspective is too large, and the photograph tends to be uncomfortable.

In the photographing lens for a fixed focus type camera according to the present invention, it is preferable that the spherical aberration satisfies the conditional expression (13) due to insufficient correction. If the upper limit of conditional expression (13) is exceeded, spherical aberration is excessively corrected, the focus position at the center of the screen approaches the ideal image plane position, and the difference from the focus position of the off-axis light flux, that is, the influence of field curvature increases. Not preferred. On the other hand, when the value goes below the lower limit of conditional expression (13), the spherical aberration is too large, which is not preferable.

Conditional expression (14) is a condition relating to the refractive power distribution of the two lenses according to the present invention. If the upper limit of conditional expression (14) is exceeded, lens errors due to manufacturing errors such as surface accuracy and eccentricity of the first lens component will occur. The performance is remarkably reduced, and the Petzval sum is undesirably increased. Conversely, when the value goes below the lower limit of conditional expression (14), the overall length of the lens becomes undesirably large.

When the first lens component is a meniscus lens having a convex surface facing the object side, it is easy to correct coma aberration, and the radius of curvature of the first surface is determined so as to satisfy the conditional expression (15). , The Petzval sum and the sensitivity to the occurrence of one-sided blur due to eccentricity can be made appropriate. Conditional expression (15)
Exceeds the upper limit, Petzval sum becomes too large and F
When the number is relatively small, even if the photographing surface such as a film surface is curved, all the areas in the screen are not within the depth of focus, which is not preferable. Conversely, if the lower limit of conditional expression (15) is exceeded, the effect of the optical axis shift between the two refracting surfaces of the first lens component on the one-sided blur becomes undesirably large.

When at least one surface of the first lens component is aspherical, various aberrations including spherical aberration can be sufficiently corrected. Conditional expression (16) is a condition relating to the aspherical surface of the first lens component. If the upper limit of conditional expression (16) is exceeded, the amount of aspherical deformation is insufficient, and spherical aberration and the like cannot be sufficiently corrected. If the lower limit of conditional expression (16) is exceeded, undesired blurring or the like due to eccentricity of the lens is likely to occur, which is not preferable.

Further, when the image side surface of the first lens component is formed as an aspheric surface in which the amount of positive aspherical deformation increases as the distance from the optical axis increases, various aberrations are corrected and the influence of eccentricity is reduced. be able to.

The conditional expression (17) is a conditional expression relating to coma aberration and curvature of field. When the first lens component is a positive meniscus lens having a convex surface facing the object side, if the open F-number becomes small, the angle of view becomes low. The difference in the coma aberration due to the angle of incidence becomes remarkable, such as the inward coma aberration at, and the outward coma aberration at a high angle of view, and the position of the stop becomes important. If the upper limit of conditional expression (17) is exceeded, the difference in coma will be small, but the field curvature will be undesirably large. Conversely, when the value is below the lower limit, the difference in coma aberration becomes large, and the image quality is deteriorated particularly at a low angle of view, which is not preferable.

Further, F is such that the conditional expression (11) is satisfied.
In a lens with a small number, the entrance pupil is large and a marginal ray passes through a portion farther from the optical axis. Although strongly affected by scattered light due to structures outside the effective diameter of each lens, that is, the edges of the lenses, the photographing lens is moved from the object side to the first lens component having a positive refractive power, the first stop, and the image plane side. The scattered light can be effectively prevented by forming a second lens component having a convex surface, and arranging a diaphragm between the first and second lens components.

The second lens component has a convex surface facing the image side, and a second diaphragm is disposed behind the second lens component. The diaphragm diameter of the second diaphragm is variable, or the diaphragm is located close to the second diaphragm. If a third aperture having a different diameter is inserted to make the aperture diameter of the lens variable, the first aperture and the second lens component can be integrated into the camera, and the variable aperture mechanism can be combined with the first aperture. Since the camera is independent, the structure and assembly are simple, and a camera can be obtained in which the aperture can be varied according to the luminance of the subject.
Is satisfied, it is possible to prevent overexposure of a high-brightness subject such as a sunny day outdoors, and a long-distance subject outdoors can sufficiently enter the depth of field to obtain a preferable result. When the value goes below the lower limit of conditional expression (18), the change in curvature of field due to the stop-down is small, and the substantial curvature of field combined with spherical aberration is undesirably large. Conditional expression (18)
If the upper limit is exceeded, the peripheral light ratio tends to be insufficient at the time of narrowing down, or if the shutter placed behind the lens is a simple single-plate type, exposure unevenness in the screen due to the difference in opening and closing time will occur And is not preferred.

The variable aperture is linked with a switch of an artificial light emitting mechanism provided in a fixed focus camera, and a conditional expression (1) is established.
If the F-number of the lens is changed so as to satisfy 9), overexposure does not occur even in clear weather outdoors where the subject brightness is high, and the F-number decreases when indoors where the subject brightness is insufficient, and an artificial light emission mechanism (also called a flash) ) Even if the guide number is relatively small, the flash arrives,
Exposure of a subject at a longer distance than the background can be sufficiently obtained. The difference between F _o and F _off that exceeds the upper limit of conditional expression (19) is too small to obtain a sufficient effect. Conversely, if the value is below the lower limit, there is too much difference in the F-number, and it is not preferable that the exposure of a subject having an intermediate luminance is inappropriate regardless of which one is selected.

Further, when the photographing lens of the fixed focus camera satisfies the conditional expression (13), it is possible to satisfactorily correct various aberrations at the time of opening as described above.
If 0) is satisfied, an appropriate depth of field can be obtained both when the flash is used and when it is not used. Conditional expression (20)
Exceeds the upper limit, the amount of spherical aberration at the open F-number F _o is small, the change in the best focus position when the aperture is stopped down to F _off is small, and the depth of field is within a range where the auxiliary light by the flash reaches sufficiently when the aperture is opened. Is not preferable because the resolution of a long-distance subject is not sufficiently improved when the _aperture is stopped down to F _off . Conversely, when the value goes below the lower limit of conditional expression (20), F _off
When the focus is narrowed, the displacement of the best focus position is too large, F _off
In this case, the resolution of the subject at a short distance when the aperture is stopped down is not sufficient.

Further, in the photographing lens of the above fixed focus camera, all the two lens components have a refractive index at d-line of 1.6.
With the following plastic lens, it can be manufactured by injection molding and can be manufactured at a very low cost. As the lens material at this time, acrylic plastics such as PMMA (polymethyl methacrylate), PC (polycarbonate), PS (polystyrene), and the like are preferable because of low material cost.

Here, the artificial light emission mechanism includes all mechanisms for emitting an artificial light source used at the time of photographing.
For example, it refers to instantaneous light emission of a strobe or the like, and is also simply called flash.

[0068]

(Embodiment 1) Next, a fixed focus camera according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an oblique view of a fixed focus camera showing an example of an embodiment of the present invention, FIG. 2 is a cross-sectional view showing an internal structure of a main part of the fixed focus camera of FIG. 1, and FIG. FIG. 4 is another explanatory view of the arrangement of the apertures in the section of the optical axis of the lens.

FIG. 1 shows an example of a fixed focus camera.
FIG. 1 is a perspective view of the external appearance of a film unit with a lens. A shutter release button 12 is provided at the top of the camera, and a photographing lens 11A is provided substantially at the center of the front of the camera, and a finder 13 is provided thereon. Further, a light emitting window 14 is provided at the upper right of the camera, and a slide knob 15A for switching to artificial light emission photographing is provided below the light emitting window 14.

FIG. 2 shows a cross section of the internal structure of the main part. A photographing screen frame 24 is provided substantially at the center of the main body 10, and an unexposed film chamber 22 is disposed on one side of the photographing screen frame 24.
On the other hand, exposed film chambers 23 are arranged respectively. In addition, there is a photographing lens 11A almost at the center of the main body,
A shutter 19 is provided on the photographic screen frame 24 side of the lens. The second aperture plate AP2 is provided between the photographing lens 11A and the shutter 19. The second aperture plate AP2 has an aperture AP2.
1 and an opening AP22. Note that the first aperture plate AP1 is installed between the two lenses of the photographing lens. The charging switch 16 is a switch for charging the artificial light emitting mechanism, and the slide knob 15A is a charging switch 16
This is a knob that turns on and off. Reference numeral 25 denotes a film.

As the photographing lens 11A, a photographing lens A described in "Example" to be described later is used. The taking lens has a refractive index of 1.6 for all two lens components at d-line.
The following plastic lenses. Also, taking lens 1
The spherical aberration of a marginal ray having an F-number of 1A of F is represented by S
A (F), half of the length of the shooting screen in the long side direction is y _L
-0.008F _off · y _L <SA (F _o ) <
-0.003F _off · y _L and -0.072y _L <SA
(F _o /0.7)<−0.024 y _L is satisfied.

The F number of the photographing lens 11A is changed in conjunction with the switching on and off of the artificial light emitting mechanism, and the F number of the photographing lens 11A when the switch is turned on is changed to F
and _o (opening AP 21), when the switch F-number of the off set to F _off (opening AP 22), 0.4 <
F _o / F _off <0.7 is satisfied.

Here, a method of switching the aperture will be described. 3A shows a state when the aperture AP22 of the second aperture is set, and FIG. 3B shows a state when the aperture AP21 of the second aperture is set. As shown in the figure, two openings AP21 and AP22 are provided in the second diaphragm plate, and switching is performed by sliding. As another example, FIG. 4A shows a state diagram before insertion of the third aperture, and FIG. 4B shows a state after insertion of the third aperture. As shown, a third diaphragm plate AP3 is inserted near the second diaphragm plate AP2. 3 and 4
, AP1 indicates a first diaphragm plate.

Next, the operation at the time of photographing will be described. In the case of photographing with artificial light emission, the slide knob 15A is slid rightward in the figure from the state shown in FIG. Then
The charge switch 16 is turned on to start charging artificial light, for example, a strobe. At the same time, the diaphragm is
Switch to opening AP21. When shooting with natural light, the shooting is performed with the aperture AP22 in the state shown in FIG.

(Embodiment 2) Next, a fixed focus camera according to an embodiment of the present invention will be described with reference to the drawings. next,
The fixed focus camera will be described. FIG. 5 is a perspective view showing the appearance of the fixed focus camera according to an embodiment of the present invention. FIG. 6 is a cross-sectional view showing the internal structure of a main part of the fixed focus camera shown in FIG. FIG. 7 is an explanatory view of the arrangement of the stop in the section along the optical axis of the lens.

FIG. 5 shows an example of a fixed focus camera.
FIG. 2 is a perspective view showing the external appearance of a film unit with a lens. A shutter release button 12 is provided at the top of the camera, and a photographing lens 11B is provided substantially at the center of the front of the camera, and a finder 13 is provided thereon. Further, a light emitting window 14 is provided at the upper right of the camera, and a slide knob 15B for switching to artificial light emission photographing is provided below the light emitting window 14.

FIG. 6 shows a cross section of the internal structure of the main part. A photographing screen frame 24 is provided substantially at the center of the main body 10, and an unexposed film chamber 22 is disposed on one side of the photographing screen frame 24.
On the other hand, the exposed film chambers 23 are arranged. In addition, there is a photographing lens 11B almost in the center of the main body,
A shutter 19 is provided on the photographic screen frame 24 side of the lens. The second aperture plate AP2 is provided between the photographing lens 11B and the shutter 19. The first aperture plate AP1 has an aperture AP1.
1 and an opening AP12. The charge switch 16 is a switch for charging the artificial light emitting mechanism, and the slide knob 15B is a knob for turning the charge switch 16 on and off. Reference numeral 25 denotes a film.

As the photographing lens 11B, a photographing lens described in "Example" to be described later is used. The taking lens is a plastic in which all two lens components have a refractive index of 1.6 or less at d-line.

FIG. 7 shows a method of switching the aperture.
This will be described below. The state diagram when the opening AP11 of the first aperture plate AP1 is set and the state when the opening AP12 of the first aperture plate is set are shown. Two apertures AP1 in the first diaphragm plate
1 and AP12 are provided, and are switched by sliding. In the drawing, AP2 indicates a second aperture plate.

Next, the operation at the time of photographing will be described. When photographing with artificial light emission, the slide knob 15B is slid rightward in the figure from the state shown in FIG. Then
The charge switch 16 is turned on to start charging artificial light, for example, a strobe. At the same time, the diaphragm is
Switch to opening AP11. When shooting with natural light, shooting is performed with the aperture set to AP12 in the state shown in FIG.

[0081]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the taking lens for a fixed focus camera of the present invention will be described below. The symbols in each embodiment are as follows.

F _o : The open F number of the taking lens, and the F number when using the flash F _off : The F number when not using the flash f: The focal length of the taking lens ω: Half angle of view r: The curvature of the refracting surface Radius d: Refraction surface interval N _d : Refractive index at d-line ν _d : Abbe number f ₁ : Focal length of first lens component y _L : Half of length of photographing screen in long side direction Δx ₁ : Open F Aspherical displacement of the first surface at a height at which the marginal ray of the number passes through each surface Δx ₂ : Aspherical displacement of the second surface at a height at which the marginal ray of the open F-number passes through each surface X : Distance from the image-side refracting surface of the first lens component to the stop closest to the image D _a : Distance between the second lens component and the second stop U: Distance between object image and aspherical surface used in the present invention The shape of the coordinate takes the x axis in the optical axis direction and the height in the direction perpendicular to the optical axis. When h is given, it is represented by the equation (1).

[0083]

(Equation 1)

In equation (1), K represents the aspherical conical constant, and A _2i represents the aspherical coefficient (i = 2, 3, 4, 5, 6).

In the lens aberration diagrams, ΔS represents sagittal, and ΔM represents meridional.

(Embodiment 1) FIG. 8 is a sectional view of the optical axis of the lens of Embodiment 1 of the present invention, and FIG. 9 is a lens aberration diagram of Embodiment 1 of the present invention. Tables 1 and 2 show lens data.

[0087]

[Table 1]

[0088]

[Table 2]

FIGS. 10 and 11 show that F _off is 1 in the first embodiment.
3. The distance between the final surface of the photographing lens and the imaging screen is 25.8.
and mm, the imaging surface with a radius of curvature and cylindrical surface of 110 mm, shows the MTF diagram at each object distance for the long side direction of the screen when further squeeze was F _o. Also,
Similarly, FIGS. 12 and 13 show MTF diagrams at each subject distance in the long side direction of the screen when the aperture is reduced to F _off .

As shown in the MTF diagrams of FIGS. 7 to 10, when the object is opened, the focus is good for an object of 1 m to 4 m corresponding to the emission distance of the artificial light emission mechanism (flash), and the flash is not used. At this time, the aperture becomes F13, and the focus is good from 1 m to infinity. In addition, the MTF value itself is sufficient, and a photograph of good image quality can be obtained.

(Embodiment 2) FIG. 14 is a sectional view of a lens optical axis of Embodiment 2 of the present invention, and FIG. 15 is a lens aberration diagram of Embodiment 2 of the present invention. Tables 3 and 4 show lens data.

[0092]

[Table 3]

[0093]

[Table 4]

(Embodiment 3) FIG. 16 is a sectional view of a lens optical axis of Embodiment 3 of the present invention, and FIG. 17 is a lens aberration diagram of Embodiment 3 of the present invention. Tables 5 and 6 show lens data.

[0095]

[Table 5]

[0096]

[Table 6]

(Embodiment 4) FIG. 18 is a sectional view of a lens optical axis of Embodiment 4 of the present invention, and FIG. 19 is a lens aberration diagram of Embodiment 4 of the present invention. Tables 7 and 8 show lens data.

[0098]

[Table 7]

[0099]

[Table 8]

(Embodiment 5) FIG. 20 is a sectional view of a lens optical axis of Embodiment 5 of the present invention, and FIG. 21 is a lens aberration diagram of Embodiment 5 of the present invention. Tables 9 and 10 show lens data.

[0101]

[Table 9]

[0102]

[Table 10]

(Embodiment 6) FIG. 22 is a sectional view of a lens optical axis of Embodiment 6 of the present invention, and FIG. 23 is a lens aberration diagram of Embodiment 6 of the present invention. Table 11 and Table 12 show lens data.
Shown in

[0104]

[Table 11]

[0105]

[Table 12]

(Embodiment 7) FIG. 24 is a sectional view of a lens optical axis of Embodiment 7 of the present invention, and FIG. 25 is a lens aberration diagram of Embodiment 7 of the present invention. Table 13 and Table 14 show lens data.
Shown in

[0107]

[Table 13]

[0108]

[Table 14]

In the above embodiment, as the distance from the optical axis increases in the direction of the long side of the photographing screen or the film surface,
The lens is curved toward the photographing lens. In the case of bending cylindrically, the radius of curvature is 90-1.
Good results can be obtained when the distance is 30 mm.

Embodiment 8 FIG. 26 shows Embodiment 8 of the present invention.
3A is a cross-sectional view of the lens, and FIG. 3A is a state at the time of full aperture, and FIG. FIG. 27 is a lens aberration diagram of the eighth embodiment of the present invention, and FIG. 28 is a meridional lateral aberration diagram of the eighth embodiment. Table 1 shows the lens data.
5, shown in Table 16.

[0111]

[Table 15]

[0112]

[Table 16]

FIGS. 29 and 30 show the state of M in the release of the eighth embodiment.
In the TF diagram, when the film surface is a cylindrical surface having a radius of curvature of 110 mm, M
FIG. 31 and FIG. 32 are MTF diagrams of the narrowing down according to the eighth embodiment.
Is shown. In any case, good performance can be obtained from the center of the screen to the periphery.

(Embodiment 9) FIG. 33 shows Embodiment 9 of the present invention.
3A is a cross-sectional view of the lens, and FIG. 3A is a state at the time of full aperture, and FIG. FIG.
FIG. 10 is a lens aberration diagram according to a ninth embodiment of the present invention. Tables 17 and 18 show lens data.

[0115]

[Table 17]

[0116]

[Table 18]

(Embodiment 10) FIGS. 35A and 35B are cross-sectional views of the optical axis of a lens according to Embodiment 10 of the present invention. More specifically, FIG. 35A shows a state when the diaphragm is fully opened, and FIG. FIG.
6 is a lens aberration diagram of the tenth embodiment of the present invention. Tables 19 and 20 show lens data.

[0118]

[Table 19]

[0119]

[Table 20]

(Embodiment 11) FIG. 37 shows Embodiment 1 of the present invention.
FIG. 1A is a sectional view of the optical axis of the lens, and more specifically, FIG. FIG.
11 is a lens aberration diagram of Example 11 of the present invention. Also,
Tables 21 and 22 show the lens data.

[0121]

[Table 21]

[0122]

[Table 22]

(Embodiment 12) FIGS. 39A and 39B are cross-sectional views of a lens optical axis according to Embodiment 12 of the present invention. More specifically, FIG. 39A shows a state at the time of full aperture, and FIG. FIG.
0 is a lens aberration diagram of the twelfth embodiment of the present invention. Tables 23 and 24 show lens data.

[0124]

[Table 23]

[0125]

[Table 24]

(Embodiment 13) FIGS. 41A and 41B are sectional views of the optical axis of a lens according to Embodiment 13 of the present invention. More specifically, FIG. 41A shows a state at the time of full aperture, and FIG. FIG.
2 is a lens aberration diagram of Example 13 of the present invention. Tables 25 and 26 show lens data.

[0127]

[Table 25]

[0128]

[Table 26]

[0129]

According to the structure described above, the following effects can be obtained. According to the imaging lens for a fixed focus camera of the first to tenth and thirteenth aspects, it is optimal for a fixed focus camera having two open F-numbers and is sufficient for a subject having low luminance. Can give exposure,
Various aberrations including spherical aberration can be sufficiently corrected. Also, since the focal length and angle of view were appropriately selected,
Although it has a relatively small number, it has an appropriate depth of field to be used as a fixed focus camera, and has a configuration in which one-sided blurring and focusing errors due to manufacturing errors are unlikely to occur. As can be seen from the various aberration diagrams, each aberration is also improved.

According to the fixed focus camera of the present invention, the aperture diameter can be varied with a simple structure that is easy to assemble, and the aperture can be varied in conjunction with a flash switch. Can obtain a fixed focus camera that can obtain good exposure for various subjects.
Further, by switching the aperture, it is possible to obtain a fixed focus camera in which the range of the depth of field is optimized both when the flash is used and when it is not used.

According to the imaging lens for a fixed focus camera of the present invention, a sufficient exposure can be given even to a subject having low luminance, and various factors including spherical aberration can be obtained. The aberration can be sufficiently corrected.
Further, as shown in the various aberration diagrams, each aberration is well corrected.

According to the fixed focus camera described in claims 24, 25 and 27, the aperture diameter can be varied with a simple structure that is easy to assemble, and the aperture can be varied in conjunction with a switch during artificial light emission photography. Thus, it is possible to obtain a fixed focus camera capable of obtaining good exposure for various subjects.

[Brief description of the drawings]

FIG. 1 is a perspective view of a fixed focus camera showing an example of an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an internal configuration of a main part of the fixed focus camera of FIG. 2;

FIG. 3 is an explanatory diagram of a diaphragm arrangement in a cross section of a lens optical axis.

FIG. 4 is an explanatory view of another stop arrangement in a cross section of a lens optical axis.

FIG. 5 is an external perspective view of a fixed focus camera showing an example of an embodiment of the present invention.

6 is a cross-sectional view of an internal configuration of a main part of the fixed focus camera of FIG. 5;

FIG. 7 is an explanatory view of the arrangement of the diaphragm in the section along the optical axis of the lens.

FIG. 8 is a sectional view of a lens optical axis according to the first embodiment of the present invention.

FIG. 9 is a lens aberration diagram of the first embodiment of the present invention.

A MTF (1) Figure in the F _o of the present invention; FIG.

11 is a MTF (2) Figure in the F _o of the present invention.

FIG. 12 is an MTF (1) diagram of F _{off according to the} present invention.

FIG. 13 is an MTF (2) diagram at F _{off according to the} present invention.

FIG. 14 is a sectional view of a lens optical axis according to a second embodiment of the present invention.

FIG. 15 is a lens aberration diagram according to the second embodiment of the present invention.

FIG. 16 is a sectional view of a lens optical axis according to a third embodiment of the present invention.

FIG. 17 is a lens aberration diagram according to the third embodiment of the present invention.

FIG. 18 is a sectional view of a lens optical axis according to a fourth embodiment of the present invention.

FIG. 19 is a lens aberration diagram according to Example 4 of the present invention.

FIG. 20 is a sectional view of a lens optical axis according to a fifth embodiment of the present invention.

FIG. 21 is a lens aberration diagram of Example 5 of the present invention.

FIG. 22 is a sectional view of a lens optical axis according to a sixth embodiment of the present invention.

FIG. 23 is a lens aberration diagram of the sixth embodiment of the present invention.

FIG. 24 is a sectional view of a lens optical axis according to a seventh embodiment of the present invention.

FIG. 25 is a lens aberration diagram of the seventh embodiment of the present invention.

FIG. 26 is a sectional view of a lens optical axis according to Example 8 of the present invention.

FIG. 27 is a lens aberration diagram of Example 8 of the present invention.

FIG. 28 is a meridional lateral aberration diagram of Example 8 of the present invention.

FIG. 29 is an MTF (1) diagram at the time of opening according to the eighth embodiment of the present invention.

FIG. 30 is an MTF (2) diagram at the time of opening according to the eighth embodiment of the present invention.

FIG. 31 is an MTF when narrowing down according to the eighth embodiment of the present invention.
FIG.

FIG. 32 is an MTF when narrowing down according to the eighth embodiment of the present invention.
FIG.

FIG. 33 is a sectional view of a lens optical axis according to a ninth embodiment of the present invention.

FIG. 34 is a lens aberration diagram of the ninth embodiment of the present invention.

FIG. 35 is a sectional view of a lens optical axis according to a tenth embodiment of the present invention.

FIG. 36 is a lens aberration diagram of the tenth embodiment of the present invention.

FIG. 37 is a sectional view of a lens optical axis according to Example 11 of the present invention.

FIG. 38 is a lens aberration diagram for Example 11 of the present invention;

FIG. 39 is a sectional view of a lens optical axis according to a twelfth embodiment of the present invention.

FIG. 40 is a lens aberration diagram of the twelfth embodiment of the present invention.

FIG. 41 is an optical-axis sectional view of a thirteenth embodiment of the present invention;

FIG. 42 is a diagram depicting the lens aberration of the thirteenth embodiment of the present invention;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Main body 11A, 11B Photographing lens 12 Shutter release button 13 Viewfinder 14 Emission window 15A, 11B Slide knob 16 Charge switch 19 Shutter 22 Unexposed film room 23 Exposed film room 24 Photographing screen frame 25 Film AP1 First aperture plate AP2 Second Aperture plate AP3 Third aperture plate AP11, AP12 Aperture AP21, AP22 Aperture L1, L2 Lens

Claims (27)

[Claims] 1. A photographic lens used in a fixed focus camera, wherein the photographic lens comprises two lens components and an aperture, and the photographic lens has an open F number of F
_A photographing lens for a fixed focus camera, characterized by satisfying the following conditional expression when _o is satisfied. 5.6 <F _o <8 2. The fixed focus camera according to claim 1, wherein the following conditional expression is satisfied when a half angle of view of the photographing lens is ω and a focal length of the photographing lens is f. For shooting lens. 5 <f / (F _o · tanω) <7 3. The following conditional expression is satisfied when the spherical aberration of a marginal ray having an F number of F of the photographing lens is represented by SA (F) and half of the length of the photographing screen in the long side direction is represented by y _L. 2. The photographing lens for a fixed focus camera according to claim 1, wherein: −0.72y _L <SA (F _o /0.7)<−0.024y
_L 4. The fixed lens according to claim 1, wherein the following conditional expression is satisfied when a focal length of a first lens component closest to the object side of the photographing lens is f _1. Shooting lens for focus cameras. 0.4 <f / f ₁ <0.8 5. The first lens component closest to the object side of the taking lens is a positive meniscus lens having a convex surface facing the object side, and the radius of curvature of the object side refraction surface of the first lens component is r _1. Wherein the following conditional expression is satisfied when a focal length of the photographing lens is f.
Or the imaging lens for a fixed focus camera according to 2. 0.12 <r ₁ /f<0.23 6. The first lens component closest to the object side of the taking lens is a positive meniscus lens having a convex surface facing the object side, and at least one of the two refraction surfaces of the first lens component is formed. The aspherical displacement of the first surface and the second surface at the height at which the marginal ray of the open F number passes through each surface is defined as an aspheric surface, and the displacement toward the image plane is defined as positive, and Δ
_{3. The} photographing lens according to claim 1, wherein the following conditional expression is satisfied, where x _{1 is} Δx _2, and f is a focal length of the photographing lens. 4. −0.0004 <(Δx ₁ −Δx ₂ ) / f <−0.000
05 7. The first lens component closest to the object side of the photographing lens is a positive meniscus lens having a convex surface facing the object side. As the image-side surface of the first lens component moves away from the optical axis, the positive lens component becomes positive. The photographing lens for a fixed focus type camera according to claim 1, wherein the aspherical surface has an aspherical surface having an increased amount of displacement. 8. The image forming apparatus according to claim 1, wherein at least one stop is provided on the image side of the taking lens, and the first lens component closest to the object side of the taking lens is a positive meniscus lens having a convex surface facing the object side. 8. The following conditional expression is satisfied, where X is the distance from the image-side refracting surface of the component to the diaphragm closest to the image, and f is the focal length of the taking lens. 7. The photographing lens for a fixed focus camera according to any one of the above. 0.07 <X / f <0.15 9. The photographic lens comprises a first lens component having a positive refractive power from the object side, a first stop, a second lens component having a convex surface facing the image surface side, and a second stop. The diameter of the stop is variable or close to the second stop,
2. The photographing lens for a fixed focus camera according to claim 1, wherein a third aperture having a different aperture diameter is inserted to make a lens aperture diameter variable. 10. A second lens component of the taking lens,
10. The photographing lens according to claim 9, wherein the following conditional expression is satisfied when _a distance of the second stop is Da and _a focal length of the photographing lens is f. 0 <D _a /f<0.07 11. A fixed focus camera provided with an imaging lens for a fixed focus camera according to claim 1, 9 or 10, and an artificial light emitting mechanism, wherein the artificial light emitting mechanism is switched on.
The F-number of the taking lens is changed in conjunction with the turning off, and the F-number of the taking lens when the switch is turned on.
A fixed-focus camera which satisfies the following conditional expression when the number is F _o and the F number when the switch is off is F _off . 0.4 <F _o / F _off <0.7 12. When the spherical aberration of a marginal ray having an F-number of F of the photographic lens is F, and the half length of the photographic screen in the long side direction is y _L , the following conditional expression is satisfied. The fixed focus camera according to claim 11, wherein: −0.008F _off · y _L <SA (F _o ) <− 0.003
F _off · y _L and -0.072y _L <SA (F _o /0.7)<-0.024
y _L 13. The lens according to claim 1, wherein all of the two lens components of the photographing lens are plastic lenses having a refractive index at d-line of 1.6 or less. Shooting lens for fixed focus cameras. 14. The fixed focus camera according to claim 11, wherein all of the two lens components of the taking lens are plastic lenses having a refractive index at d-line of 1.6 or less. 15. A first lens component having a positive refracting power from the object side, a first stop, a second lens component having a convex surface facing the image plane side, and a second stop. A photographing lens which is variable or close to the first diaphragm, has a different diaphragm diameter inserted therein, and has a variable aperture diameter, and the open F number of the photographing lens is F
_A photographing lens for a fixed focus camera, characterized by satisfying the following conditional expression when _o is satisfied. 5.6 <F _o <8 16. The fixed focus camera according to claim 15, wherein the following conditional expression is satisfied when a half angle of view of the photographing lens is ω and a focal length of the photographing lens is f. For shooting lens. 5 <f / (F _o · tanω) <7 17. When the spherical aberration of a marginal ray having an F number of F of the photographing lens is F is SA (F) and half of the length of the photographing screen in the long side direction is y _L , the following conditional expression is satisfied. 16. The photographing lens for a fixed focus camera according to claim 15, wherein: −0.072 y _L <SA (F _o /0.7)<−0.024
y _L 18. The fixed focus camera according to claim 15, wherein the following conditional expression is satisfied when a focal length of a first lens component of the taking lens is f ₁ . Shooting lens. 0.4 <f / f ₁ <0.8 19. The photographic lens wherein a first lens component of the photographic lens is a positive meniscus lens having a convex surface facing the object side, a radius of curvature of a refraction surface of the first lens component on the object side is r ₁ , 18. The photographing lens for a fixed focus camera according to claim 15, wherein the following conditional expression is satisfied, where f is a focal length of f. 0.12 <r ₁ /f<0.23 20. The first lens component of the photographing lens comprises a positive meniscus lens having a convex surface facing the object side, and at least one of the two refraction surfaces of the first lens component.
Two surfaces are aspherical, the amounts of aspherical displacement of the first surface and the second surface at the height at which the marginal ray of the open F number passes through each surface are Δx ₁ and Δx _2, and the focal length of the photographing lens is f
18. The taking lens according to claim 15, wherein the following conditional expression is satisfied. However, as for each aspherical displacement amount, a displacement facing the image plane is defined as positive. −0.0004 <(Δx ₁ −Δx ₂ ) / f <−0.000
05 21. The first lens component of the photographing lens comprises a positive meniscus lens having a convex surface facing the object side, and as the image-side surface of the first lens component moves away from the optical axis,
20. The photographing lens for a fixed focus camera according to claim 15, wherein the positive aspherical surface has an aspherical surface with an increased amount of displacement. 22. The first lens component of the taking lens is a positive meniscus lens having a convex surface facing the object side, and the second lens component closest to the image side with respect to the image-side refraction surface of the first lens component.
21. The fixed focal length camera according to claim 15, wherein the following conditional expression is satisfied when a distance to an aperture is X and a focal length of the photographing lens is f. Shooting lens. 0.07 <X / f <0.15 23. When the distance between the first stop and the second stop of the taking lens is D _S and the focal length of the taking lens is f, the following conditional expression is satisfied. 22. The taking lens for a fixed focus camera according to any one of 15 to 21. 0.04 <D _S /f<0.1 24. A fixed focus camera provided with an imaging lens for a fixed focus camera according to any one of claims 15 to 23 and an artificial light emitting mechanism, wherein the switch of the artificial light emitting mechanism is turned on and off. When the F-number of the taking lens is changed, and the F-number of the taking lens when the switch is on is F _o, and the F-number when the switch is off is F _off , the following conditions are satisfied. A fixed focus camera which satisfies the formula. 0.4 <F _o / F _off <0.7 25. When the spherical aberration of a marginal ray having an F number of F of the photographing lens is F, and the half length of the photographing screen in the long side direction is y _L , the following conditional expression is satisfied. 25. The fixed focus camera according to claim 24, wherein: −0.008F _off · y _L <SA (F _o ) <− 0.003
F _off · y _L and -0.072y _L <SA (F _o /0.7)<-0.024
y _L 26. The method according to claim 15, wherein all of the two lens components of the taking lens are plastic lenses having a refractive index at d-line of 1.6 or less. Shooting lens for fixed focus cameras. 27. The fixed focus camera according to claim 24, wherein all of the two lens components of the taking lens are plastic lenses having a refractive index at d-line of 1.6 or less. .