Calibration method and apparatus for optical imaging lens system with double optical paths

This invention provides a calibration method and a corresponding apparatus for optical imaging lens system with double optical paths. The apparatus for optical imaging lens system with double optical paths comprises a first optical subsystem, a second optical subsystem and a calibration module. The calibration module receives a first image data from the first optical subsystem and a second image data from the second optical subsystem. The calibration module calibrates the first image data according to at least one selected optical parameter of the second optical subsystem, and calibrates the second image data according to at least one selected optical parameter of the first optical subsystem. The selected optical parameters of the first optical subsystem and the second optical subsystem are different.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 099142767 filed in Taiwan, R.O.C. on Dec. 8, 2010, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a calibration method and a corresponding apparatus for optical imaging lens system with double optical paths, and more particularly, to a calibration method for optical imaging lens system with double optical paths which is able to calibrate images coming from different optical systems.

2. Description of the Prior Art

Calibration of cameras, especially the calibration of distortion, has been considered as an important issue in aerial photographic measurement and machine vision system (MVS). The article entitled “Camera Calibration with Distortion Models and Accuracy Evaluation” (Juyan Weng, IEEE TRANSACTION ON PATTERN ANALYSIS AND MACHINE INTELLIGENCE VOL. 14 NO. 10 OCTOBER 1992) proposes a number of methods for calibrating distortions. However, as cameras are widely used, commercially and industrially, it will be insufficient to simply calibrate the distortions. Improving uniformity in images generated by different cameras is also required. Therefore, there is a demand for a method which is able to correct image non-uniformity caused by differences among various components produced in massive quantities.

As an optical system comprises a number of precise optical components, one optical system will be different from anther in optical parameters, such as lateral magnification, contrast, image surface illumination and distortion, due to the subtle differences in the size of the individual components thereof. The characteristics of different batches of sensors vary slightly as well. Non-uniform images displayed continuously at a high speed will cause much discomfort for the average viewers.

Therefore, a need exists in the art for a method which can effectively calibrate non-uniformity in images generated by different optical lenses.

SUMMARY OF THE INVENTION

An object of the present invention is to calibrate the differences between two optical systems caused during the manufacturing process so that the output images will not be affected by such differences. Consequently, uniformity in images can be improved.

To achieve the above object, the present invention provides a calibration apparatus for optical imaging lens system with double optical paths, comprising: a first optical subsystem; a second optical subsystem having a back focal length equal to that of the first optical subsystem; an optical path selector selectively having a light reflection state and a light passing state; a first reflector set disposed at an image side of the first optical subsystem for directing the light from the first optical subsystem to the optical path selector; a second reflector set disposed at an image side of the second optical subsystem for directing the light from the second optical subsystem to the optical path selector; a sensor for obtaining a first image data from an image coming from the first optical subsystem and a second image data from an image coming from the second optical subsystem; and a calibration module for receiving the first image data and the second image data from the sensor, the calibration module calibrating the first image data according to at least one selected optical parameter of the second optical subsystem and calibrating the second image data according to at least one selected optical parameter of the first optical subsystem, the selected optical parameters of the first optical subsystem and the second optical subsystem being different; wherein when the optical path selector is in the light reflection state, the light from the first optical subsystem forms an image on the sensor while the light from the second optical subsystem forms an image on another position rather than on the sensor; and wherein when the optical path selector is in the light passing state, the light from the second optical subsystem forms an image on the sensor while the light from the first optical subsystem forms an image on another position rather than on the sensor.

The present invention provides another calibration apparatus for optical imaging lens system with double optical paths, comprising: a first optical subsystem; a second optical subsystem having a back focal length equal to that of the first optical subsystem; a reflector set disposed at the image sides of the first optical subsystem and the second optical subsystem for directing the light from the first optical subsystem and the light from the second optical subsystem, so that an optical path of the first optical subsystem intersects with an optical path of the second optical subsystem; a movable optical path selector for reflecting either the light from the first optical subsystem or the light from the second optical subsystem; a sensor for obtaining a first image data from an image coming from the first optical subsystem and a second image data from an image coming from the second optical subsystem; and a calibration module for receiving the first image data and the second image data from the sensor, the calibration module calibrating the first image data according to at least one selected optical parameter of the second optical subsystem and calibrating the second image data according to at least one selected optical parameter of the first optical subsystem, the selected optical parameters of the first optical subsystem and the second optical subsystem being different; wherein when the movable optical path selector is disposed at a position where the optical path of the first optical subsystem and the optical path of the second optical subsystem intersect, the light from the first optical subsystem forms an image on the sensor while the light from the second optical subsystem forms an image on another position rather than on the sensor; and wherein when the movable optical path selector is disposed at the position other than the optical path of the first optical subsystem, the optical path of the second optical subsystem, or the intersection of the two optical paths, the light from the second optical subsystem forms an image on the sensor while the light from the first optical subsystem forms an image on another position rather than on the sensor.

The present invention provides another calibration apparatus for optical imaging lens system with double optical paths, comprising: a first optical system; a second optical system having a back focal length equal to that of the first optical system; a first sensor for obtaining a first image data from an image coming from the first optical system; a second sensor for obtaining a second image data from an image coming from the second optical system; and a calibration module for receiving the first image data and the second image data from the first sensor and the second sensor, the calibration module calibrating the first image data according to at least one selected optical parameter of the second optical system and calibrating the second image data according to at least one selected optical parameter of the first optical system, the selected optical parameters of the first optical system and the second optical system being different.

The present invention provides a calibration method for optical imaging lens system with double optical paths comprising the steps of: receiving a first image data from a first optical subsystem and a second image data from a second optical subsystem; calibrating the first image data according to at least one selected optical parameter of the second optical subsystem; and calibrating the second image data according to at least one selected optical parameter of the first optical subsystem.

With the aforementioned calibration method and apparatus for optical imaging lens system with double optical paths, uniformity in images generated by different optical systems or optical subsystems can be improved.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the present invention are shown.

FIG. 1Aillustrates a schematic view showing a calibration apparatus100for optical imaging lens system with double optical paths according to a first embodiment of the present invention, wherein an image coming from the first optical subsystem is recorded.FIG. 1Billustrates the calibration apparatus100according to the same embodiment of the present invention, wherein an image coming from the second optical subsystem is recorded. In this embodiment, the calibration apparatus100for optical imaging lens system with double optical paths comprises a first optical subsystem101, a second optical subsystem102, an optical path selector103, a first reflector set104, a second reflector set105comprising two reflectors105aand105b, a sensor106, and a calibration module108. By a proper configuration of the first reflector set104, the second reflector set105comprising two reflectors105aand105band the optical path selector103, the present invention enables a first image coming from the first optical subsystem101and a second image coming from the second optical subsystem102to be recorded on the sensor106in a sequential or alternating order. The sensor106outputs a first image data and a second image data according to the first image and the second image. The calibration module108receives the first image data and the second image data output by the sensor106and calibrates the first image data and the second image data to improve uniformity in images.

The first optical subsystem101and the second optical subsystem102may be optical systems with conventional imaging lenses; they are used for receiving the light coming from an object (not shown) to be imaged. The first reflector set104comprising one reflector is disposed at the image side of the first optical subsystem101for directing the light from the first optical subsystem101to the optical path selector103. The second reflector set105comprising two reflectors105aand105bis disposed at the image side of the second optical subsystem102for directing the light from the second optical subsystem102to the optical path selector103. The optical path selector103comprises a liquid crystal element having at least liquid crystal molecules and two electrode plates. By selecting the types of liquid crystal molecules and the voltage applied to them, the optical path selector103can be controlled to let light pass through or reflect. In the first embodiment of the present invention, when the optical path selector103is in the light reflection state, the light from the first optical subsystem101is reflected by the optical path selector103and forms an image on the sensor106; meanwhile, the light from the second optical subsystem102is reflected by the optical path selector103and forms an image on another position107rather than on the sensor106. When the optical path selector103is in the light passing state, the light from the second optical subsystem102passes through the optical path selector103and forms an image on the sensor106; meanwhile, the light from the first optical subsystem101passes through the optical path selector103and forms an image on another position107rather than on the sensor106.

FIG. 1Aillustrates a schematic view showing a calibration apparatus for optical imaging lens system with double optical paths according to the first embodiment of the present invention, wherein an image coming from the first optical subsystem101is recorded. InFIG. 1A, the optical path of the first optical subsystem101is shown in solid lines, while the optical path of the second optical subsystem102is shown in dashed lines; the optical path selector103is in the light reflection state. After the first optical subsystem101receives the light from an object (not shown) to be imaged, the light from the first optical subsystem101is reflected by the first reflector set104and directed to the optical path selector103; since the optical path selector103is in the light reflection state, the light from the first optical subsystem101is further reflected by the optical path selector103, directed to the sensor106and forms a first image thereon. The first image is recorded on the sensor106upon its formation.

On the other hand, after the second optical subsystem102receives the light from an object (not shown) to be imaged, the light from the second optical subsystem102is reflected by the second reflector set105comprising two reflectors105aand105band then directed to the optical path selector103; since the optical path selector103is in the light reflection state, the light from the second optical subsystem102is further reflected by the optical path selector103, directed to another position107and forms an image thereon rather than on the sensor106.

FIG. 1Billustrates a schematic view showing a calibration apparatus for optical imaging lens system with double optical paths according to the first embodiment of the present invention, wherein an image coming from the second optical subsystem102is recorded. InFIG. 1B, the optical path of the first optical subsystem101is shown in dashed lines, while the optical path of the second optical subsystem102is shown in solid lines; the optical path selector103is in the light passing state. After the second optical subsystem102receives the light from an object (not shown) to be imaged, the light from the second optical subsystem102is reflected by the second reflector set105(comprising two reflectors105aand105b) and directed to the optical path selector103; since the optical path selector103is in the light passing state, the light from the second optical subsystem102passes through it and forms a second image on the sensor106. The second image is recorded on the sensor106upon its formation.

On the other hand, after the first optical subsystem101receives the light from an object (not shown) to be imaged, the light from the first optical subsystem101is reflected by the first reflector set104and then directed to the optical path selector103; since the optical path selector103is in the light passing state, the light from the first optical subsystem101passes through it and forms an image on another position107rather than on the sensor106.

It can be seen from the above that, the first optical subsystem101and the second optical subsystem102of a calibration apparatus for optical imaging lens system with double optical paths according to the present invention have equal back focal lengths, so that the light from both the first optical subsystem101and the second optical subsystem102can form clear images on the sensor106.FIG. 2illustrates a timeline chart showing the state that each component of the calibration apparatus100for optical imaging lens system with double optical paths is according to the first embodiment of the present invention. As described above, by controlling the voltage applied to it, the optical path selector103can let light pass through or reflect light. In the first embodiment, the optical path selector103will be in the light passing state when a high voltage is applied thereto; the optical path selector103will be in the light reflection state when a low voltage is applied thereto. The calibration apparatus100for optical imaging lens system with double optical paths of the present invention further comprises a control unit (not shown), which controls whether a high or low voltage is applied to the optical path selector103. With reference toFIGS. 1A and 1B, in the first embodiment, when a low voltage is applied to the optical path selector103, the optical path selector103will be in the light reflection state; as a result, the sensor106receives a first image that comes from the first optical subsystem101. And when a high voltage is applied to the optical path selector103, the optical path selector103will be in the light passing state; as a result, the sensor106receives a second image that comes from the second optical subsystem102. By synchronizing the cycle that the optical path selector103changes its optical state and the cycle that the sensor106is exposed to light, a calibration apparatus for optical imaging lens system with double optical paths of the present invention enables an image coming from the first optical subsystem101and an image coming from the second optical subsystem102to be alternately recorded on the sensor106in a sequential order. It should be noted that alternatively, by using other types of liquid crystal molecules, a low voltage applied to the optical path selector103could cause light to pass through the optical path selector103, and a high voltage applied to the optical path selector103could cause light to be reflected by the optical path selector103.

From the above, it is known that the optical path selector103may be any device which has a light passing state and a light reflection state.FIG. 3illustrates an alternative example of the optical path selector103in the calibration apparatus for optical imaging lens system with double optical paths according to the first embodiment of the present invention. The optical path selector103comprises a disk303. The disk303has five light reflection areas3031and five light passing areas3032, each light reflection area3031and each light passing area3032being arranged alternately. By rotating the disk303, light can either pass through the disk303or be reflected by it. The light reflection areas3031may be mirrors or areas made of reflective materials, and the light passing areas3032may be hollowed out areas or made of materials that permit light to pass therethrough.

FIG. 4Aillustrates a schematic view showing a calibration apparatus100for optical imaging lens system with double optical paths according to an alternative example of the first embodiment of the present invention, wherein an image coming from the first optical subsystem101is recorded.FIG. 4Billustrates a schematic view showing a calibration apparatus100for optical imaging lens system with double optical paths according to an alternative example of the first embodiment of the present invention, wherein an image coming from the second optical subsystem102is recorded. InFIG. 4A, the optical path of the first optical subsystem101is shown in solid lines, while the optical path of the second optical subsystem102is shown in dashed lines. One of the light reflection areas3031of the disk303is rotated to be placed at the position where the optical path of the first optical subsystem101and the optical path of the second optical subsystem102intersect; that is, the disk303is in the light reflection state. After the first optical subsystem101receives the light from an object (not shown) to be imaged, the light from the first optical subsystem101is reflected by the first reflector set104and directed to the disk303; since the disk303is in the light reflection state, the light from the first optical subsystem101is further reflected by the disk303, directed to the sensor106and forms a first image thereon. The first image is recorded on the sensor106upon its formation.

On the other hand, after the second optical subsystem102receives the light from an object (not shown) to be imaged, the light from the second optical subsystem102is reflected by the second reflector set105(comprising two reflectors105aand105b) and directed to the disk303; since the disk303is in the light reflection state, the light from the second optical subsystem102is further reflected by the disk303, directed to another position107and forms an image thereon rather than on the sensor106.

FIG. 4Billustrates a schematic view showing a calibration apparatus100for optical imaging lens system with double optical paths according to an alternative example of the first embodiment of the present invention, wherein an image coming from the second optical subsystem102is recorded. InFIG. 4B, the optical path of the first optical subsystem101is shown in dashed lines, while the optical path of the second optical subsystem102is shown in solid lines. One of the light passing areas3032of the disk303is rotated to be placed at the position where the optical path of the first optical subsystem101and the optical path of the second optical subsystem102intersect; that is, the disk303is in the light passing state. After the second optical subsystem102receives the light from an object (not shown) to be imaged, the light from the second optical subsystem102is reflected by the second reflector set105(comprising two reflectors105aand105b) and directed to the disk303; since the disk303is in the light passing state, the light from second optical subsystem102passes through the disk303and forms a second image on the sensor106. The second image is recorded on the sensor106upon its formation.

On the other hand, after the first optical subsystem101receives the light from an object (not shown) to be imaged, the light from the first optical subsystem101is reflected by the first reflector set104and directed to the disk303; since the disk303is in the light passing state, the light from the first optical subsystem101passes through the disk303and forms an image on another position107rather than on the sensor106. The cycle that the disk303changes its state for light passing or blocking and the cycle that the sensor106is exposed to light can be synchronized by adjusting the angular velocity of the disk303. By synchronizing the cycles of the states, an image coming from the first optical subsystem101and an image coming from the second optical subsystem102can be alternately recorded on the sensor106in a sequential order.

FIG. 7is a flow chart showing the steps of a calibration method for optical imaging lens system with double optical paths. This calibration method is applicable to the calibration module108of the aforementioned embodiment. The calibration module108may be an image processing unit or a multi-functional unit.

In Step701, the calibration module108receives a first image data from the first optical subsystem101and a second image data from the second optical subsystem102. As described above, when the light from the first optical subsystem101is reflected by the optical path selector103and forms an image on the sensor106, the sensor106obtains a first image. When the light from the second optical subsystem102passes through the optical path selector103and forms an image on the sensor106, the sensor106obtains a second image. The sensor106outputs a first image data and a second image data according to the first image and the second image.

In Step702, the calibration module108calibrates the first image data according to at least one selected parameter of the second optical subsystem102. In Step703, the calibration module108calibrates the second image data according to at least one selected parameter of the first optical subsystem101. The calibration calculation of certain parameters of the first image data from the first optical subsystem101is made based on corresponding parameters of the second optical subsystem102while the calibration calculation of certain parameters of the second image data from the second optical subsystem102is made based on corresponding parameters of the first optical subsystem101. The calibration calculation will not be performed on the parameters of the first image data from the first optical subsystem101on which the calibration calculation of certain parameters of the second image data is based; the calibration calculation will not be performed on the parameters of the second image data from the second optical subsystem102on which the calibration calculation of certain parameters of the first image data is based. In the present invention, an image coming from the first optical subsystem101and an image coming from the second optical subsystem102can be alternately recorded on the sensor106in a sequential order. Therefore, the calibration module108will calibrate the first image data from the first optical subsystem101and the second image data from the second optical subsystem102upon receiving them.

In Step704, the calibration module108combines and stores the calibrated first and second image data. Generally, the modified first and second image data can be stored in an alternating order.

FIG. 5Aillustrates a schematic view showing a calibration apparatus500for optical imaging lens system with double optical paths according to a second embodiment of the present invention, wherein an image coming from the first optical subsystem501is recorded.FIG. 5Billustrates the calibration apparatus500according to the same embodiment of the present invention, wherein an image coming from the second optical subsystem502is recorded. In the second embodiment, a calibration apparatus500for optical imaging lens system with double optical paths comprises a first optical subsystem501, a second optical subsystem502, a movable optical path selector503, a first reflector set504, a second reflector set505(comprising two reflectors505aand505b), a sensor506, and a calibration module508. By a proper configuration of the first reflector set504, the second reflector set505(comprising two reflectors505aand505b) and the movable optical path selector503, the present invention enables a first image coming from the first optical subsystem501and a second image coming from the second optical subsystem502to be alternately recorded on the sensor506in a sequential order. The sensor506outputs a first image data and a second image data according to the first image and the second image. The calibration module508receives the first image data and the second image data from the sensor506and calibrates the first image data and the second image data to improve uniformity in images. The first optical subsystem501and the second optical subsystem502may be optical systems with conventional imaging lenses. The first reflector set504comprising one reflector is disposed at the image side of the first optical subsystem501for directing the light coming from the first optical subsystem501. The second reflector set505(comprising two reflectors505aand505b) is disposed at the image side of the second optical subsystem502for directing the light coming from the second optical subsystem502. Moreover, the configuration of the first reflector set504and the second reflector set505(comprising two reflectors505aand505b) allows the optical path of the first optical subsystem501and the optical path of the second optical subsystem502to intersect. The movable optical path selector503comprises a reflector for reflecting the light from the first optical subsystem501or the light from the second optical subsystem502. In this embodiment, when the movable optical path selector503is disposed at the position where the optical path of the first optical subsystem501and the optical path of the second optical subsystem502intersect, the light from the first optical subsystem501is reflected by the movable optical path selector503and further forms an image on the sensor506, while the light from the second optical subsystem502is reflected by the movable optical path selector503and further forms an image on another position507rather than on the sensor506. When the movable optical path selector503is disposed at the position other than the optical paths of the first optical subsystem501and the second optical subsystem, or the intersection of the two subsystems, the light from the second optical subsystem502forms an image on the sensor506while the light from the first optical subsystem501forms an image on another position507rather than on the sensor506.

FIG. 5Aillustrates a schematic view showing a calibration apparatus500for optical imaging lens system with double optical paths according to the second embodiment of the present invention, wherein an image coming from the first optical subsystem501is recorded. InFIG. 5A, the optical path of the first optical subsystem501is shown in solid lines, while the optical path of the second optical subsystem502is shown in dashed lines. The movable optical path selector503is disposed at the position where the optical path of the first optical subsystem501and the optical path of the second optical subsystem502intersect. After the first optical subsystem501receives the light from an object (not shown) to be imaged, the light from the first optical subsystem501is reflected by the first reflector set504and directed to the movable optical path selector503. As a result, the light from the first optical subsystem501is further reflected by the movable optical path selector503and forms a first image on the sensor506. The first image is recorded on the sensor506upon its formation.

On the other hand, after the second optical subsystem502receives the light from an object (not shown) to be imaged, the light from the second optical subsystem502is reflected by the second reflector set505comprising two reflectors505aand505band directed to the movable optical path selector503. As a result, the light from the second optical subsystem502is further reflected by the movable optical path selector503and forms an image on another position507rather than on the sensor506.

FIG. 5Billustrates a schematic view showing a calibration apparatus500for optical imaging lens system with double optical paths according to the second embodiment of the present invention, wherein an image coming from the second optical subsystem502is recorded. InFIG. 5B, the optical path of the first optical subsystem501is shown in dashed lines, while the optical path of the second optical subsystem502is shown in solid lines. The movable optical path selector503is disposed at the position other than the optical paths of the first optical subsystem501and the second optical subsystem502, or the intersection of the two subsystems. After the first optical subsystem501receives the light from an object (not shown) to be imaged, the light from the first optical subsystem501is reflected by the first reflector set504and directed to another position507rather than to the sensor506. On the other hand, after the second optical subsystem502receives the light from an object (not shown) to be imaged, the light from the second optical subsystem502is reflected by the second reflector set505comprising two reflectors505aand505b, directed to the sensor506and forms a second image thereon. The second image is recorded on the sensor506upon its formation.

It can be seen from the above that, the first optical subsystem501and the second optical subsystem502of a calibration apparatus for optical imaging lens system with double optical paths according to the present invention have equal back focal lengths, so that light from both the first optical subsystem501and the second optical subsystem502can form clear images on the sensor506. In a calibration apparatus for optical imaging lens system with double optical paths of the present invention, the cycle that the movable optical path selector503changes its position and the cycle that the sensor506is exposed to light can be synchronized by adjusting the moving speed of the movable optical path selector503. By synchronizing the two cycles, an image coming from the first optical subsystem501and an image coming from the second optical subsystem502can be alternately recorded on the sensor506in a sequential order.

FIG. 7shows the steps of a calibration method for optical imaging lens system with double optical paths of the present invention. This calibration method is applicable to the calibration module508of the aforementioned embodiment.

In Step701, the calibration module508receives a first image data from the first optical subsystem501and a second image data from the second optical subsystem502. As described above, when the light from the first optical subsystem501is reflected by the optical path selector503and forms an image on the sensor506, the sensor506obtains a first image. When the light from the second optical subsystem502passes through the optical path selector503and forms an image on the sensor506, the sensor506obtains a second image. The sensor506outputs a first image data and a second image data according to the first image and the second image.

In Step702, the calibration module508calibrates the first image data according to at least one selected parameter of the second optical subsystem502. In Step703, the calibration module508calibrates the second image data according to at least one selected parameter of the first optical subsystem501. The calibration calculation of certain parameters of the first image data from the first optical subsystem501is made based on corresponding parameters of the second optical subsystem502while the calibration calculation of certain parameters of the second image data from the second optical subsystem502is made based on corresponding parameters of the first optical subsystem501. The calibration calculation will not be performed on the parameters of the first image data from the first optical subsystem501on which the calibration calculation of certain parameters of the second image data is based; the calibration calculation will not be performed on the parameters of the second image data from the second optical subsystem502on which the calibration calculation of certain parameters of the first image data is based. In this embodiment, an image coming from the first optical subsystem501and an image coming from the second optical subsystem502can be alternately recorded on the sensor506in a sequential order. Therefore, the calibration module508will calibrate the first image data from the first optical subsystem501and the second image data from the second optical subsystem502upon receiving them.

In Step704, the calibration module508combines and stores the calibrated first and second image data. Generally, the calibrated first and second image data can be stored in an alternating order.

FIG. 6illustrates a schematic view showing a calibration apparatus600for optical imaging lens system with double optical paths according to a third embodiment of the present invention. In the third embodiment, the calibration apparatus600for optical imaging lens system with double optical paths comprises a first optical system601, a second optical system602, a first sensor603, a second sensor604, and a calibration module605. A first image coming from the first optical system601and a second image coming from the second optical system602can be recorded on the first sensor603and the second sensor604, respectively. The first sensor603outputs a first image data according to the first image, and the second sensor604outputs a second image data according to the second image. The calibration module605receives the first image data output by the first sensor603and the second image data output by the second sensor604and calibrates the first and the second image data to improve uniformity in images.

The first optical system601and the second optical system602may be optical systems with conventional imaging lenses; they are used for receiving the light coming from an object (not shown) to be imaged. After the first optical system601receives the light from an object to be imaged, the light from the first optical system601is projected to the first sensor603and forms a first image thereon. The first image is recorded on the first sensor603upon its formation. On the other hand, after the second optical system602receives the light from an object (not shown) to be imaged, the light from the second optical system602is projected to the second sensor604and forms a second image thereon. The second image is recorded on the second sensor604upon its formation.

FIG. 8is a flow chart showing the steps of a calibration method for optical imaging lens system with double optical paths according to another embodiment of the present invention. This calibration method is applicable to the calibration module605of the aforementioned embodiment.

In Step801, the calibration module605receives a first image data from the first optical system601and a second image data from the second optical system602. As described above, when the light from the first optical system601forms an image on the first sensor603, the first sensor603obtains a first image data. When the light from the second optical system602forms an image on the second sensor604, the second sensor604obtains a second image data.

In Step802, the calibration module605calibrates the first image data according to at least one selected parameter of the second optical system602. In Step803, the calibration module605calibrates the second image data according to at least one selected parameter of the first optical system601. The calibration calculation of certain parameters of the first image data from the first optical system601is made based on corresponding parameters of the second optical system602while the calibration calculation of certain parameters of the second image data from the second optical system602is made based on at least one parameter of the first optical system601. The calibration calculation will not be performed on the parameters of the first image data from the first optical system601on which the calibration calculation of certain parameters of the second image data is based; the calibration calculation will not be performed on the parameters of the second image data from the second optical system602on which the calibration calculation of certain parameters of the first image data is based. In this embodiment, an image coming from the first optical system601and an image coming from the second optical system602can be recorded on the first sensor603and the second sensor604, respectively. Therefore, the calibration module605can calibrate a first image data from the first optical system601and a second image data from the second optical system602simultaneously. Alternatively, the calibration module605calibrates the first image data from the first optical system601and the second image data from the second optical system602in an alternating order.

In Step804, the calibration module605combines and stores the calibrated first and second image data. Generally, the calibrated first and second image data are stored in an alternating order.

In the aforementioned embodiments of the present invention, the parameters of the optical subsystem or optical system may be the distortion parameter, the lateral magnification parameter, the contrast parameter, the image surface illumination parameter, etc. It should be noted that the parameters adopted in a calibration method for optical imaging lens system with double optical paths of the present invention are not limited to those listed above. The parameters of any optical image can be parameters of the optical subsystem and optical system of the present invention.

FIG. 9is a schematic view showing how a calibration method for optical imaging lens system with double optical paths of the present invention adopting the distortion parameter, the lateral magnification parameter, the contrast parameter and the image surface illumination parameter is performed. In this embodiment, the distortion parameter and the contrast parameter of the optical subsystem A serve as criteria while the lateral magnification parameter and the image surface illumination parameter of the optical subsystem B serve as criteria. Therefore, the calibration calculation of the lateral magnification parameter and the image surface illumination parameter of the first image data from the optical subsystem A is made based on the lateral magnification parameter and the image surface illumination parameter of the optical subsystem B, but the calibration calculation will not be performed on the distortion parameter and the contrast parameter of the first image data from the optical subsystem A. On the other hand, the calibration calculation of the distortion parameter and the contrast parameter of the second image data from the optical subsystem B is made based on the distortion parameter and the contrast parameter of the optical subsystem A, but the calibration calculation will not be performed on the lateral magnification parameter and the image surface illumination parameter of the second image data from the optical subsystem B. The calibrated first and second image data will then be further integrated or alternately stored to form a single image data.

The lateral magnification means the lateral magnifying power; the contrast magnification means the black and white contrast magnifying power; the image surface illumination means the ratio of brightness on the central part to that on the periphery of the image. Generally, the calibration calculation is performed on the parameters of both optical subsystems that may lead to inferior image quality, thereby the image quality can be maintained.

In the present invention, the selection of parameters from the two optical subsystems can be made by comparing the images of an object or a test board taken by the two optical subsystems under the same conditions. While this invention has been described by way of examples and in terms of preferred embodiments, it is to be understood that this invention is not limited hereto, and that various changes, substitutions, and alterations can be made herein without departing from the spirit and scope of this invention as defined by the appended claims.