BACKGROUND OF THE INVENTION

Field of the Invention

The invention generally relates to an optical apparatus, and more particularly, to a lens module and an image apparatus.

Description of Related Art

Along with the increasing popularity of demand on the surveillance under night and low-light environments, video cameras with 24-hours surveillance function are widespread used. In general speaking, a conventional video camera uses a light-filter for switching the 24-hours surveillance modes. In more details, when an object to be shot is under an environment with adequate luminance, a light-filter would be put down to block infrared light from entering the photosensitive component. On the other hand, when an object to be shot is under an environment with insufficient luminance, an infrared light source of the video camera would be turned on to emit infrared light onto the object to be shot. At the time, the light-filter is disabled so that the infrared light reflected by the object to be shot can reach at the photosensitive component for imaging.

In the application practice however, the images captured during day normally are clear, while the images captured during night (in infrared mode) are fuzzy. The different results are caused by a too large difference between visible light and infrared light in wavelength. In more details, after the visible light and the infrared light pass through a lens module of the video camera, due to the two focal planes of the above-mentioned two lights are apart quite far from each other; in addition, due to the cost consideration, most of the commercial video cameras for surveillance are not equipped with auto-focusing function. Under such circumstances, how to design an appropriate lens module of video cameras able to capture images with good quality at day and night becomes one of important projects to solve the above-mentioned problem by the relevant developers.

U.S. Pat. No. 7,417,802 discloses a lens module including a first lens group, a second lens group, a third lens group, a fourth lens group and a fifth lens group, in which the first, the second, the third, the fourth and the fifth lens groups have positive refractive-power, negative refractive-power, positive refractive-power, positive refractive-power and positive refractive-power respectively. U.S. Pat. No. 7,369,313 discloses a zoom lens for a video camera. The zoom lens includes a first lens group with positive refractive-power, a second lens group with negative refractive-power, a third lens group with positive refractive-power, a fourth lens group with positive refractive-power and a fifth lens group with positive refractive-power. The fourth lens group and the fifth lens group herein respectively have an aspheric lens. In addition, U.S. Pat. Nos. 7,227,693, 6,738,196, 6,870,689 and 6,989,940 disclose several types of projection lenses. U.S. Pat. Nos. 5,299,064, 5,414,562, 5,548,445 and 5,659,426 also disclose a projection lenses including multiple lens groups.

SUMMARY OF THE INVENTION

Accordingly, the invention is directed to a lens module with high performance of imaging quality.

The invention is also directed to an image apparatus with good 24-hours confocal image-capturing quality.

Other objectives, features and advantages of the invention will be further understood from the further technological features disclosed by the embodiments of the invention.

To achieve one of, a part of or all of the above-mentioned objectives, or to achieve other objectives, an embodiment of the invention provides a lens module. The lens module is located between an object-side and an image-side for capturing an object light-beam from the object-side. The lens module is disposed on a transmission path of the object light-beam and includes five lens groups sequentially-arranged from the object-side to the image-side: a first lens group, a second lens group, a third lens group, a fourth lens group and a fifth lens group. The first lens group has positive refractive-power and includes a first lens with positive refractive-power and a second lens with negative refractive-power. The second lens group has negative refractive-power and includes a third lens with positive refractive-power and a fourth lens with negative refractive-power. The third lens group has positive refractive-power and includes a fifth lens with positive refractive-power and a sixth lens with negative refractive-power. The fourth lens group has positive refractive-power and includes a seventh lens with positive refractive-power and an eighth lens with negative refractive-power. The fifth lens group has positive refractive-power and includes a ninth lens with positive refractive-power and a tenth lens with negative refractive-power. The first lens group, the third lens group and the fifth lens group herein are fixed groups, the second lens group and the fourth lens group are removable groups and any lens in the third lens group is a spherical lens.

Another embodiment of the invention provides an image apparatus, which includes the above-mentioned lens module and a photosensitive component. The photosensitive component is disposed on a transmission path of an object light-beam and located at an image-side of the image apparatus. The lens module is located between the photosensitive component and an object-side.

The above-mentioned image apparatus further includes a light-emitting component for emitting an illumination light-beam towards the object-side. The illumination light-beam has a first wavelength range and the illumination light-beam after being reflected by an object at the object-side is converted into the object light-beam. When the luminance at the object-side is less than a predetermined value, the light-emitting component is turned on to emit the illumination light-beam with the first wavelength range towards the object-side, in which the first wavelength range of the illumination light-beam is the same as the wavelength range of the infrared light.

The above-mentioned image apparatus further includes a light-filtering component for blocking the illumination light beam with the first wavelength range, in which when the luminance at the object-side is greater than the predetermined value, the light-filtering component moves on the transmission path of the object light-beam, while when the luminance at the object-side is less than the predetermined value, the light-filtering component leaves from the transmission path of the object light-beam.

In an embodiment of the invention, focal length of the second lens group of the above-mentioned lens module is f2, focal length of the lens module at a wide-end is fW, focal length of the lens module at a tele-end is fT and the lens module satisfies a following condition expression:
0.4<|f2/√{square root over ((fW×fT))}|<0.6

In an embodiment of the invention, focal length of the fourth lens group of the above-mentioned lens module is f4, focal length of the fifth lens group is f5 and the lens module satisfies a following condition expression:

0.25<(f⁢⁢4f⁢⁢5)<0.65

In an embodiment of the invention, the first lens of the first lens group of the above-mentioned lens module is located between the second lens of the first lens group and the second lens group, and the first lens and the second lens are joined to each other to form a cemented lens.

In an embodiment of the invention, Abbe number of the first lens of the above-mentioned lens module is V1, and Abbe number of the second lens is V2, wherein V1 and V2 satisfy a following condition expression:
V1>70 andV2<35

In an embodiment of the invention, the third lens group of the above-mentioned lens module includes a cemented lens and the cemented lens includes the fifth lens, in which Abbe number of the fifth lens is V3, and V3 satisfies a following condition expression:
V3>70

In an embodiment of the invention, the above-mentioned fourth lens group and the fifth lens group respectively include at least one aspheric lens.

In an embodiment of the invention, the above-mentioned first lens group further includes an eleventh lens with positive refractive-power located between the first lens of the first lens group and the second lens group.

In an embodiment of the invention, the above-mentioned second lens group further includes a twelfth lens with negative refractive-power located between the fourth lens and the first lens group.

In an embodiment of the invention, the fifth lens of the above-mentioned third lens group is located between the sixth lens of the third lens group and the second lens group.

In an embodiment of the invention, the above-mentioned third lens group further includes a thirteenth lens with negative refractive-power located between the fifth lens and the second lens group and the cemented lens of the above-mentioned third lens group is formed by the fifth lens, the sixth lens and the thirteenth lens.

In an embodiment of the invention, the above-mentioned third lens group further includes a fourteenth lens with positive refractive-power located between the thirteenth lens and the second lens group.

In an embodiment of the invention, the cemented lens of the above-mentioned third lens group is formed by the fifth lens and the sixth lens.

In an embodiment of the invention, the seventh lens of the above-mentioned fourth lens group is located between the eighth lens of the fourth lens group and the third lens group, and the seventh lens is the aspheric lens of the above-mentioned fourth lens group.

In an embodiment of the invention, the above-mentioned fourth lens group further includes a fifteenth lens with positive refractive-power located between the eighth lens and the fifth lens group.

In an embodiment of the invention, the ninth lens of the above-mentioned fifth lens group is located between the tenth lens of the fifth lens group and the fourth lens group, the ninth lens is the aspheric lens of the above-mentioned fifth lens group and the ninth lens and the tenth lens form a cemented lens.

In an embodiment of the invention, the above-mentioned lens module further includes an aperture stop located between the second lens group and the third lens group.

Based on the description above, in the lens module and the image apparatus of the invention, the five lens groups all include at least one positive lens and at least one negative lens, the refractive-powers of the five lens groups are sequentially positive, negative, positive, positive and positive. Moreover, each lens of the third lens group is a spherical lens. In this way, in addition to having high zoom magnification and high revolution, the lens module and the image apparatus of the invention can obtain good image-capturing effect under the different wavelength ranges of the object light-beam.

In order to make the aforementioned and other features and advantages of the invention comprehensible, several exemplary embodiments accompanied with figures are described in detail below.

