CN100520477C - Pickup lens - Google Patents

Abstract

The invention relates to an image pickup lens, which comprises four lenses, and a first lens with positive refractive index, a second lens with negative refractive index, a third lens with positive area refractive index and a fourth lens with weak refractive index which are arranged in sequence from an object end to an imaging end. The first, third and fourth lenses have at least one lens surface being aspheric. The image pickup lens must satisfy the following conditions: 0.1 < | F/F4| < 1, where F is the focal length of the image pickup lens, and F4 is the focal length of the fourth lens.

Description

Pickup lens

technical field

The invention relates to an image pickup lens, in particular to an image pickup lens which is applied to an imaging device and has a light weight.

Background technique

In recent years, mobile phones, portable digital assistants (PDAs) and notebook computers are mostly equipped with camera lens modules. Most of these lens modules are required to be small in size and light in weight, and because the resolution of image sensing units such as CCD or CMOS is quite low in the past, most conventional lens modules only have one or two lenses.

Nowadays, with the advancement of semiconductor process technology, the image sensor units for mobile phones, portable digital assistants and notebook computers have gradually increased to megapixels; the number of lenses in the lens is too small, and it may not be able to provide better image quality. How to use the minimum number of lenses to provide high-resolution imaging becomes the difficulty of the present invention.

Contents of the invention

Therefore, the object of the present invention is to provide a lightweight pickup lens, which uses four lenses to reduce the weight and length of the pickup lens; meanwhile, various optical aberrations can be corrected to obtain an excellent image.

According to the above-mentioned purpose, the pickup lens of the present invention includes a first lens with a positive refractive power, a second lens with a negative refractive power, a third lens with a positive refractive power, and a weak refractive power lens from the object end to the imaging end. rate of the fourth lens.

As mentioned above, the first lens of the pickup lens of the present invention is a crescent-shaped positive lens, and its object end surface protrudes toward the object end; the third lens is also a crescent-shaped positive lens, and its imaging end surface faces The imaging end is convex; and the object end surface of the fourth lens is convex toward the imaging end.

As mentioned above, the pickup lens of the present invention must satisfy this condition:

$\mathrm{<span\; class="notranslate">\; 0.1</span>}<span\; class="notranslate">\; <</span><span\; class="notranslate">\; |</span>\frac{\mathrm{<span\; class="notranslate">\; f</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 1</span>}$

Wherein, F is the focal length value of the pickup lens, and f4 is the focal length value of the fourth lens.

As mentioned above, the first, third and fourth lenses of the pickup lens of the present invention all have at least one aspheric surface.

As mentioned above, the aperture stop of the pickup lens of the present invention is located between the first lens and the second lens.

As mentioned above, the object end surface and the imaging end surface of the fourth lens of the present invention further need to meet this condition:

$\mathrm{<span\; class="notranslate">\; 0.05</span>}<span\; class="notranslate">\; <</span><span\; class="notranslate">\; |</span>\frac{\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 7</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 7</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0.8</span>}$

Wherein, R7 is the radius of curvature of the object end surface of the fourth lens, and R8 is the radius of curvature of the imaging end surface of the fourth lens.

As described above, the object end surface of the second lens of the pickup lens of the present invention is convex toward the imaging end.

The advantage of the present invention is that four lenses are used, so that the pickup lens of the present invention has the advantages of short length and light weight. Preferably, the first positive lens, the second negative lens, the third positive lens and the fourth lens can all be made of plastic materials.

Another advantage of the present invention is that the aperture diaphragm is disposed between the first and second lenses, so that the pickup lens has a wide viewing angle.

Now in conjunction with the accompanying drawings of the description, the pickup lens of the present invention will be further described in detail.

Description of drawings

Fig. 1 schematically shows the position of the pickup lens of the embodiment of the present invention;

Fig. 2 shows the spherical aberration of the pickup lens of the embodiment of the present invention;

Fig. 3 shows the field curvature aberration of the pickup lens of the embodiment of the present invention;

Fig. 4 shows the distortion aberration of the pickup lens of the embodiment of the present invention;

FIG. 5 shows the ray aberration of the pickup lens of the embodiment of the present invention.

Detailed ways

The pickup lens of the present invention can be applied to an image capture device for imaging an object on an image sensing device, such as a Charge Coupled Device (CCD for short) or a Complementary Metal Oxide Semiconductor (CMOS). The pickup lens includes a first lens with a positive refractive power, a second lens with a negative refractive power, a third lens with a positive refractive power and a third lens with a weak refractive power from the object end to the imaging end. Four lenses. The aperture stop is disposed between the first lens and the second lens. The first, third and fourth lenses all have at least one aspherical surface.

In the pickup lens of the present invention, the first lens is a crescent-shaped positive lens, and its object end surface protrudes toward the object end. The second lens is a negative lens whose object end surface protrudes toward the imaging end. The third lens is a crescent-shaped positive lens, and its image end surface protrudes toward the imaging end. The object end surface of the fourth lens is concave toward the imaging end, and the imaging end surface thereof is convex toward the imaging end.

In the present invention, the pickup lens must meet the following conditions:

$\mathrm{<span\; class="notranslate">\; 0.1</span>}<span\; class="notranslate">\; <</span><span\; class="notranslate">\; |</span>\frac{\mathrm{<span\; class="notranslate">\; f</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Wherein, F is the focal length value of the pickup lens, and f4 is the focal length value of the fourth lens. When |F/f4| is greater than the upper limit of condition (1), the total length of the pickup lens will be too long. When |F/f4| is less than the lower limit of the condition (1), the distortion aberration of the pickup lens will worsen and the image quality will be reduced.

In addition, the object end surface and the imaging end surface of the fourth lens of the present invention further need to meet this condition:

$\mathrm{<span\; class="notranslate">\; 0.05</span>}<span\; class="notranslate">\; <</span><span\; class="notranslate">\; |</span>\frac{\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 7</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; R</span>}\mathrm{<span\; class="notranslate">\; 7</span>}}<span\; class="notranslate">\; |</span><span\; class="notranslate">\; <</span>\mathrm{<span\; class="notranslate">\; 0.8</span>}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

大于条件(2)的上限值时，将使得拾像镜头的系统像差愈趋恶化而降低成像品质。当

小于条件(2)的下限值时，将使得第四透镜无法修补拾像镜头的像差。Wherein, R7 is the radius of curvature of the object end surface of the fourth lens, and R8 is the radius of curvature of the imaging end surface of the fourth lens. when

When it is greater than the upper limit of condition (2), the system aberration of the pickup lens will worsen and the imaging quality will be reduced. when

When the value is less than the lower limit of condition (2), the fourth lens cannot repair the aberration of the pickup lens.

Referring to Fig. 1, the embodiment of the pickup lens of the present invention, this pickup lens comprises the first lens G1 of positive refractive power, the second lens G2 of negative refractive power, positive refractive power from object end OBJ to imaging end IMA in sequence. The third lens G3 with diopter power and the fourth lens G4 with weak diopter power; and, the system focal length of the pickup lens is F=5.30mm, and Fno.=2.86. In addition, the aperture stop STO is located between the first lens G1 and the second lens G2.

The first lens G1 is a crescent-shaped positive lens, and includes a first surface L1 and a second surface L2 respectively from the object end OBJ to the imaging end IMA, and the first surface L1 adjacent to the object end OBJ protrudes toward the object end OBJ. In addition, both the first surface L1 and the second surface L2 are aspherical.

The second lens G2 is a negative lens, and the third surface L3 adjacent to the object end OBJ must protrude toward the imaging end IMA. Referring to FIG. 1 , in this embodiment, the second lens G2 is a biconcave lens, and the fourth surface L4 adjacent to the imaging end IMA protrudes toward the object end OBJ. In addition, both the third surface L3 and the fourth surface L4 are aspherical.

The third lens G3 is a crescent-shaped positive lens, and includes a fifth surface L5 and a sixth surface L6 respectively from the object end OBJ to the imaging end IMA, and the sixth surface L6 adjacent to the imaging end IMA protrudes toward the imaging end IMA. In addition, both the fifth surface L5 and the sixth surface L6 are aspherical.

The fourth lens G4 is a crescent lens, and includes a seventh surface L7 and an eighth surface L8 respectively from the object end OBJ to the imaging end IMA, and the eighth surface L8 adjacent to the imaging end IMA protrudes toward the imaging end IMA. In addition, both the seventh surface L7 and the eighth surface L8 are aspherical.

In an embodiment of the present invention, the parameters of the first, second, third and fourth lenses of the pickup lens are listed in Table 1 in sequence:

In addition, in the embodiment of the present invention, the first surface L1 and the second surface L2 of the first lens G1, the third surface L3 and the fourth surface L4 of the second lens G2, the fifth surface L5 and the sixth surface of the third lens G3 The surface L6, and the seventh surface L7 and the eighth surface L8 of the fourth lens G4 are aspheric surfaces, and the relevant values of the aspheric surfaces are listed in Table 2 in sequence:

According to Table 1, it can be known that the focal length of the fourth lens G4 with weak refractive power is f4=-20.963, and |F/f4|=0.253, which indeed meets the condition (1).

可得 $\left|\frac{R8-R7}{R8+R7}\right|=0.216$ 且确实符合条件(2)。According to Table 1, it can be known that the radius of curvature R7 of the seventh surface L7 of the fourth lens G4=-0.87 mm, and the radius of curvature R8 of the eighth surface L8 of the fourth lens G4=-1.350 mm. Substitute R7 and R8 into

Available $\left|\frac{R8-R7}{R8+R7}\right|=0.216$ And it does meet condition (2).

FIG. 2 shows the spherical aberration (Spherical aberration) of the pickup lens of the embodiment of the present invention. Within the pupil radius of 0.9283mm, the spherical aberration is less than 0.07mm.

Fig. 3 shows the field curvature aberration (Field Curvature) of the pickup lens of the embodiment of the present invention. Within the range of the image field height of 2.9mm, the field curvature aberration of light rays on the meridian plane and sagittal plane is less than 0.08mm.

FIG. 4 shows the distortion aberration (distortion aberration) of the pickup lens of the embodiment of the present invention. Within the range of the image field height of 2.9mm, the distortion difference of each wavelength light is less than 0.15%.

FIG. 5 shows the ray aberration (also known as rayfans) of the pickup lens of the embodiment of the present invention. When the image heights are 0.0mm, 1.8mm, 2.3mm and 2.9mm respectively, the ray aberration of the pickup lens remains quite flat.

As can be seen from the above, the pickup lens of the embodiment of the present invention has excellent imaging quality; although the first lens, the second lens, the third lens and the fourth lens all use plastic injection molding lenses, they are not affected by temperature changes. degrade image quality.

Referring to FIG. 1 and Table 1, the aperture stop STO of the pickup lens of the present invention is located between the first lens G1 and the second lens G2.

The above is only a specific embodiment of the present invention, and should not limit the scope of the present invention with this, that is, all simple equivalent changes and modifications made according to the patent scope of the present invention and the content of the description of the invention are still within the scope of the present invention. Within the scope covered by the patent of the present invention.

Claims (9)

1. an imagery picking lens is characterized in that, comprises in regular turn on optical axis from thing end to imaging end:

First lens are positive refractive index;

Second lens are negative refractive index;

The 3rd lens are a meniscus positive lens, have a thing end surfaces and a picture end surfaces, and it protrude towards the imaging end as end surfaces; And

The 4th lens are weak refractive index, are meniscus lens, have a thing end surfaces and a picture end surfaces, and it protrude towards the imaging end as end surfaces;

Wherein, the aperture mirror diaphragm is arranged between first lens and second lens, and this imagery picking lens meets the following conditions:

$0.1<\left|\frac{F}{f4}\right|<1$

Wherein, F is the focal length value of this imagery picking lens, and f4 is the focal length value of the 4th lens.

2. imagery picking lens as claimed in claim 1 is characterized in that, first lens are a meniscus positive lens, have a thing end surfaces and a picture end surfaces, and its thing end surfaces protrudes towards the thing end.

3. imagery picking lens as claimed in claim 2 is characterized in that, second lens have a thing end surfaces and a picture end surfaces, and its thing end surfaces protrudes towards the imaging end.

4. imagery picking lens as claimed in claim 1 or 2 is characterized in that, this imagery picking lens further satisfies this condition:

$0.05<\left|\frac{R8-R7}{R8+R7}\right|<0.8$

Wherein, R7 is the radius-of-curvature of the thing end surfaces of the 4th lens, and R8 is the radius-of-curvature of the imaging end surfaces of the 4th lens.

5. imagery picking lens as claimed in claim 2 is characterized in that, it is aspheric surface that the first meniscus positive lens has at least one surface.

6. imagery picking lens as claimed in claim 2 is characterized in that, it is aspheric surface that the 3rd meniscus positive lens has at least one surface.

7. imagery picking lens as claimed in claim 2 is characterized in that, it is aspheric surface that the 4th lens have at least one surface.

8. imagery picking lens as claimed in claim 3 is characterized in that it is aspheric surface that second negative lens has at least one surface.

9. imagery picking lens as claimed in claim 6, wherein the first, the 3rd meniscus positive lens is made by plastic material.

Images