WO2010143108A2

WO2010143108A2 - Optical scanner

Info

Publication number: WO2010143108A2
Application number: PCT/IB2010/052490
Authority: WO
Inventors: Rieko Verhagen; Bart Willem Jan Spikker
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2009-06-11
Filing date: 2010-06-04
Publication date: 2010-12-16
Also published as: WO2010143108A3

Abstract

The invention relates to an optical scanner and a method, adapted for imaging applications. The optical scanner (8) comprises a detector array (4) operatively connected to a lens array (1), wherein the lens array (1) comprises a plurality of lenses, being an odd number, and the plurality of lenses is arranged in a predetermined configuration, and the lens array (1) is adapted for allowing a movement relative to the detector array (4). In this way, a possibility is provided to reconstruct the light intensity of the detection signal and thus to assign the light intensity collected per lens.

Description

Optical scanner

FIELD OF THE INVENTION

The invention relates to the field of optical scanners, preferably adapted for imaging applications.

BACKGROUND OF THE INVENTION

Document US 7,388,658 B2 describes an apparatus and a method for detecting inclination by employing a point source of light that emits light through a lens towards a reflective surface of a liquid contained in a vessel. Light reflected from the surface passes through the lens to form a defocused image of the point source on a two-dimensional array of detector elements. Data acquired from the array represents intensity of the light incident on each of the detector elements. A center of gravity representing inclination of the vessel is determined from the data.

In some applications, such as in laser shaving, there is a need for a high-numerical-aperture objective scanner. Preferably, a single objective or a plurality of objectives are moved, which are adapted for scanning a surface. There are two possibilities adapted for detecting light: Firstly, a detector array is moved together with a lens array. Secondly, a lens array is moved in combination with a stationary detector array, i.e. a detector array which stays constant relative to a fixed ground or a fixed surface, respectively, is applied. The first possibility is expensive to implement due to the high speed at which the detection array is required to move.

According to the second possibility and due to the movement of the lenses comprised by the lens array, the signal travels over the detector array which comprises a plurality of detecting units, such as photodetectors or photodiodes, and at a certain moment in time it becomes possible for a detecting unit to receive detection light from two different lenses. Therefore, in imaging applications, it becomes hardly possible to determine the light intensity collected per lens. For such a determination to be made, only very complex and expensive setups are known in the prior art. SUMMARY OF THE INVENTION

It is an object of the invention to provide a possibility in the field of optical scanners comprising a lens array for reconstructing the light intensity of the detection signal and for determining the light intensity collected per lens, in particular in imaging applications.

This object is achieved by the subject matter of the independent claims. Preferred embodiments are defined in the sub claims.

According to a first aspect of the invention, this object is achieved by an optical scanner, adapted for imaging applications, with a detector array operatively connected to a lens array, wherein the lens array comprises a plurality of lenses, being an odd number, and the plurality of lenses is arranged in a predetermined configuration, and the lens array is adapted for allowing a movement relative to the detector array.

In this way, information regarding full intensity is obtained, preferably for the lens array, more preferably for each lens out of the plurality of lenses. Thus, it becomes possible to assign the light intensity collected per lens out of the plurality of lenses to the respective lens. The solution is very simple and can be realized at low cost.

According to a preferred embodiment of the invention, the movement of the lens array relative to the detector array is adapted for scanning a surface. Preferably, the movement of the lens array relative to the detector array comprises a step-wise and/or a continuous movement and/or a movement in a rotating fashion, such as rotating along a predetermined axis. Preferably, such a movement comprises a changing relative phase, more preferably a constantly changing relative phase. Preferably, the detector array is operatively connected to a fixed ground. However, depending on the desired application, it is also possible that the detector array is operatively connected to a lens array, but neither to a fixed ground nor to a fixed surface. The detector array preferably comprises a plurality of detecting or detection units, such as photodiodes or photodetectors.

According to another preferred embodiment of the invention, the predetermined configuration of the plurality of lenses comprises a closed configuration, such as lenses arranged in a ring-shaped array, more preferably a disc comprising the plurality of lenses equally spaced at its periphery, and/or a linear configuration, such as lenses arranged in a direction at least partly horizontal relative to the detector array. The closed configuration preferably comprises a ring configuration. Preferably, the lenses are arranged in a way such that they are each equidistantly spaced with respect to one another. Preferably, the linear configuration of the plurality of lenses comprises at least a further detection unit arranged on each side of the lens array.

According to yet another preferred embodiment of the invention, the detector array comprises a plurality of detection units, and the number of lenses out of the plurality of lenses equals the number of detection units. It becomes also possible that in a closed configuration the number of lenses is a factor < 2 smaller than the number of detection units of the detector array. Preferably, the distance between every two adjacent lenses of the plurality of lenses equals a pitch corresponding to the distance between every two adjacent detection units. It is noted that in case the number of detecting units is a factor > 2 larger than the number of lenses, a detecting unit will not be illuminated by two beams of different lenses at the same time. It goes without saying that a larger detecting unit preferably corresponds to a larger intensity falling on the detecting unit.

According to yet another preferred embodiment of the invention, the optical scanner further comprises an actuator that is operatively connected to the lens array and adapted for allowing a movement of the lens array relative to the detector array. In this way, the movement of the lens array relative to the detector array is controllable at any time. Preferably, the optical scanner further comprises an encoder adapted for determining the position of the lens array relative to the actuator. In this way, the position of the lens array is determined accurately and, therefore, the relative phase between the lens array and the detector array is calculated.

According to yet another preferred embodiment of the invention, the optical scanner further comprises a data processing unit adapted for processing information generated by light intensity directed to the detector array in such a way that light intensity coming from a lens of the plurality of lenses is assigned to the respective lens. Preferably, the optical scanner further comprises a display unit adapted for displaying the generated information for a user.

According to a second aspect of the invention, this object is achieved by a method of use for an optical scanner according to the first aspect of the invention, in at least one of the following applications: in a laser shaver, in a microscope, and in a detection system, more preferably a detection system adapted for detecting a birefringent object, such as a hair; most preferably the detection system is integrated in a laser shaver.

According to a third aspect of the invention, this object is achieved by a method, adapted for imaging applications, comprising the step of directing light through a lens array towards a detector array, the detector array and the lens array being comprised by an optical scanner according to the first aspect of the invention, and the step of moving the lens array relative to the detector array, thereby scanning a surface.

Preferably, the optical scanner is used in at least one of the following applications: in a laser shaver, in a microscope, and in a detection system that is preferably integrated in a laser shaver. The inventive idea can preferably be applied in the field of lens array scanning, more specifically relating to immersion objective scanning, such as for a microscope or for any other imaging device or imaging unit.

It is an important idea of the invention to deal with partial overlap between a lens and a detecting unit, in the following also referred to as relative phase or relative phase shift between lens and detecting unit. Moreover, due to the fact that there is typically some dead space between the lenses and also between the photodiodes, also referred to as pitch, the information obtained about the relative phase between the detecting unit and the lens array enables the intensity of the light emanating from each lens of the plurality of lenses to be recalculated. In particular, the invention serves for finding a possibility of detecting light intensity per lens in the case of a combination of a stationary detecting array and a moving lens array. In other words, the lens array is moved relative to a detector array.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

In the drawings:

Fig. 1 shows detection light falling on a detector array in a first scenario;

Fig. 2 shows detection light falling on a detector array in a second scenario;

Fig. 3 shows detection light falling on a detector array with a relative phase shift α according to a preferred embodiment of the invention;

Fig. 4 illustrates the determinant of a matrix A for an even number, indicated in Fig. 4a, and for an odd number, indicated in Fig. 4b, of lenses and/or detecting units according to a preferred embodiment of the invention; and

Fig. 5 schematically shows an implementation of an optical scanner according to a preferred embodiment of the invention. DETAILED DESCRIPTION OF EMBODIMENTS

It is one aspect of the invention to collect as much signal as possible by means of equally sized detecting units with respect to the detection beam, as schematically shown in Fig. 1. However, if two detection light beams fall onto the same detecting unit comprised by the detector array 4, it is no longer immediately possible to directly relate the sensor reading to the intensity per beam. Fig. 1 shows detection light, indicated in black, falling on the detector array 4, indicated in white. A single detector is illuminated by two beams of the detection light. Therefore, the invention serves to overcome the problem of distinguishing between the intensities of the beams by a direct measurement. It is an idea of the invention to use an odd number of lenses adapted for reconstructing the original light intensity per lens when a plurality of lenses in a lens array is used, preferably in a closed configuration such as a ring-shaped array corresponding to a disc with lenses arranged at its periphery according to a preferred embodiment of the invention. The inventors have found that for an odd number of lenses the mathematical reconstruction is robust. Applying an even number of lenses results in a very unstable and/or noise-sensitive reconstruction, in particular close to the situation in which the light emanating from two lenses is equally distributed over a single photodiode, i.e. when the relative phase between lens and detecting unit equals one half.

The position of the lens is reconstructed by means of the difference between the measurements of two detectors. Fig. 2 shows detection light falling on the detector array 4, wherein the detection light is indicated in black and the detector array 4 comprising a plurality of detecting units is indicated in white. In order to ensure that the detector array 4 is illuminated by a single lens, a detecting unit is not allowed to be bigger than the dead space or pitch between the lenses. This means that a detecting unit is illuminated by a beam of the detection light. However, by doubling the number of detecting units with respect to the number of lenses, it becomes possible to determine the position of each lens or the lens array comprising a plurality of lenses. Since a detecting unit comprises a small surface with respect to the illuminated surface comprised by the detection beam, a large amount of the signal does not fall on the detecting unit and thus a lot of signal intensity will be lost. According to the preferred embodiment of the invention, an odd number of moving lenses illuminating a stationary array of photodiodes is used. This allows reducing the number of detecting units required. In the following, it is assumed that the size of the detector pitch is equal to the size of the lens pitch. For simplicity reasons, there is no dead space between the lenses and the detecting units. Further, it is assumed that the number of detecting units is equal to the number of lenses. Moreover, the detection light per lens shows a uniform distribution and the predetermined configuration of the lens array is chosen from one of a linear and/or a ring configuration. In other words, the positions of the lenses with respect to each other are known and are fixed. Fig. 3 shows detection light, indicated in black, falling onto the detector array 4, indicated in white, according to a preferred embodiment of the invention. The detector array 4 and the lens array (not shown in Fig. 3) comprise a relative phase CC with respect to each other. A certain or fixed relative phase CC between the lens array and the detector array, can be given by the following equation:

PD = A HI,

where PD is the matrix comprising the measurement results of the different detecting units, A is the matrix comprising the relative phases, and HI is the matrix for the light intensity per lens. Assuming four lenses and four detecting units in a circular arrangement, such as a ring arrangement, the matrix A looks as follows:

α 1 - α 0 0

0 α 1 - α 0

A =

0 0 α 1 - α

1 - α 0 0 α

where cc is the relative phase between a detecting unit and a lens, as indicated in Fig. 3. A solution for the matrix HI with respect to the measured intensities PD and the relative phases CC, comprised by the matrix A, is given by:

HI = A^{"1 •} PD,

where A^"1 is the inverse matrix A. This implies that if the inverse matrix exists, i.e. det(A) ≠ 0, a solution to the above equation exists. Moreover, the determinant of the matrix A indicates the robustness of the solution. The solution is more robust as the values of the determinant are larger. Fig. 4 shows a plot of the determinant for an even- sized matrix A and for an odd- sized matrix A according to the preferred embodiment of the invention. Fig. 4a shows a plot of the determinant in the case of an even number of lenses or detecting units, where the determinant goes through zero, which indicates a non-existing solution for the inverse matrix. Fig. 4b shows a plot of the determinant of matrix A for an odd number of lenses or detecting units. The determinant does not come close to zero and thus the inverse matrix exists for all values. For values where det(A) = 0 it holds that no inverse matrix exists. For values close to zero, the solution is sensitive to, for instance, noise and thus is not robust. This is the case for an even-sized matrix, not however for odd-sized matrix A. It is worth noting that the comparison of the systematic error for an even and an odd numbered lens array shows that in the case of an even numbered lens array a substantial error occurs and that the systematic error for an odd-numbered lens array is at least two orders of magnitude smaller than for an even-numbered lens array. This statement preferably holds for a relative phase CC = 0.5. Fig. 5 shows an optical scanner 8 according to the preferred embodiment of the invention. A rotating lens array 1 comprising an odd number of lenses with image reconstruction is schematically illustrated in this Figure. In the upper part of Fig. 5, a round disc is depicted with a lens array 1 comprising a plurality of lenses arranged at the periphery of the disc, wherein the disc is rotated by means of a motor or an actuator 2. An angular detector or angular encoder 3 measures the position of the lenses with respect to the actuator 2, also referred to as fixed world, and, therefore, with respect to the stationary photodiodes comprised by the detector array 4. The detector array 4 is adapted for detecting the intensity of each light beam and sends data 5 to a data processing unit 6 adapted for processing the data 5, wherein the data 5 comprises information generated from the light intensity falling on the detector array 4. The data processing unit 6 is adapted for processing information about the position and other parameters of the detector array 4 and also about the relative phase CC in order to recalculate the intensity of the light emanating from each lens of the plurality of lenses comprised by the lens array 1. Furthermore, the intensity per lens is interpreted by means of, for instance, an image illustrated on a display unit 7 adapted for displaying the generated information for a user. The detector array 4 is thus operatively connected to the lens array 1 , wherein the lens array 1 is adapted for allowing a movement relative to the detector array 4 and also for scanning a surface.

It is an idea of the invention to scan a surface by means of a predetermined configuration of a lens array, such as a rotating array of lenses, for instance a rotating disc comprising a plurality of lenses arranged at its periphery. The idea is applicable in any device which requires a moving objective scanner, such as in a laser shaver or in a microscope.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. An optical scanner (8), adapted for imaging applications, with a detector array (4) operatively connected to a lens array (1), wherein the lens array (1) comprises a plurality of lenses, being an odd number, the plurality of lenses is arranged in a predetermined configuration, and the lens array (1) is adapted for allowing a movement relative to the detector array (4).

2. The optical scanner according to claim 1, wherein the movement of the lens array (1) relative to the detector array (4) is adapted for scanning a surface.

3. The optical scanner according to any one of the preceding claims, wherein the movement of the lens array (1) relative to the detector array (4) comprises a step-wise and/or a continuous movement and/or a movement in a rotating fashion.

4. The optical scanner according to any one of the preceding claims, wherein the predetermined configuration of the plurality of lenses comprises a closed configuration, such as lenses arranged in a ring-shaped array, preferably a disc comprising the plurality of lenses equally spaced at its periphery, and/or a linear configuration, such as lenses arranged in a direction at least partly horizontal relative to the detector array (4).

5. The optical scanner according to claim 4, wherein the closed configuration comprises a ring configuration.

6. The optical scanner according to any one of the preceding claims, wherein the lenses are arranged in a way such that they are each equidistantly spaced with respect to one another.

7. The optical scanner according to any one of claims 4 to 6, wherein the linear configuration of the plurality of lenses comprises at least a further detection unit arranged on each side of the lens array (1).

8. The optical scanner according to any one of the preceding claims, wherein the detector array (4) comprises a plurality of detection units, and the number of lenses out of the plurality of lenses equals the number of detection units.

9. The optical scanner according to claim 8, wherein the distance between every two adjacent lenses of the plurality of lenses comprises a pitch corresponding to the distance between every two adjacent detection units.

10. The optical scanner according to any one of the preceding claims, further comprising an actuator (2) that is operative Iy connected to the lens array (1) and is adapted for allowing a movement of the lens array (1) relative to the detector array (4).

11. The optical scanner according to claim 10, further comprising an encoder (3) adapted for determining the position of the lens array (1) relative to the actuator (2).

12. The optical scanner according to any one of the preceding claims, further comprising a data processing unit (6) adapted for processing information generated by light intensity directed to the detector array (4) in such a way that light intensity coming from a lens of the plurality of lenses is assigned to the respective lens.

13. The optical scanner according to claim 12, further comprising a display unit

(7) adapted for displaying the generated information for a user.

14. Method of use for an optical scanner according to any one of claims 1 to 13, in at least one of the following applications: in a laser shaver; in a microscope; and in a detection system, preferably a detection system adapted for detecting a birefringent object, such as a hair; more preferably the detection system is integrated in a laser shaver.

15. A method, adapted for imaging applications, comprising the step of directing light through a lens array (1) towards a detector array (4), the detector array (4) and the lens array (1) being comprised by an optical scanner according to any one of claims 1 to 13, and the step of moving the lens array (1) relative to the detector array (4), thereby scanning a surface.