APPARATUS FOR LIGHT INTENSITY ADJUSTMENT

Abstract

An automotive camera includes at least one lens unit, at least one image sensor having a plurality of light sensitive elements configured to collect incident light projected by the lens unit and transform it into an electrical signal, the image sensor being configured to read out the charge collected by the plurality of light sensitive elements with a predetermined frame rate, and at least one apparatus for light intensity adjustment which is mounted or mountable in front of the lens unit and includes a view control film (VCF).

Claims

1. An automotive camera, comprising: at least one lens unit; at least one image sensor comprising a plurality of light sensitive elements configured to collect incident light projected by the lens unit and transform it into an electrical signal, the image sensor being configured to read out the charge collected by the plurality of light sensitive elements with a predetermined frame rate; and at least one apparatus for light intensity adjustment which is mounted or mountable in front of the lens unit and comprises a view control film (VCF).

2. The automotive camera of claim 1, wherein an integration time of the image sensor for collecting the incident light is approximately constant.

3. The automotive camera of claim 2, wherein the integration time of the image sensor is close to a maximum defined by a time period between two consecutive frame read outs.

4. The automotive camera of claim 1, wherein the automotive camera further comprises a coverglass and the VCF is positioned on the coverglass.

5. The automotive camera of claim 4, wherein the coverglass is mounted on the automotive camera and can be detached from the automotive camera.

6. The automotive camera of claim 1, wherein the VCF is positioned on an outermost lens of the lens unit.

7. A vehicle, comprising at least one automotive camera according to claim 1.

8. The vehicle of claim 7, wherein an integration time of the image sensor for collecting the incident light is approximately constant.

9. The vehicle of claim 8, wherein the integration time of the image sensor is close to a maximum defined by a time period between two consecutive frame read outs.

10. The vehicle of claim 7, wherein the automotive camera further comprises a coverglass and the VCF is positioned on the coverglass.

11. The vehicle of claim 10, wherein the coverglass is mounted on the automotive camera and can be detached from the automotive camera.

12. The vehicle of claim 7, wherein the VCF is positioned on an outermost lens of the lens unit.

13. A method for adjusting light intensity by an apparatus for light intensity adjustment according to claim 1, comprising dimming the at least one apparatus for light intensity adjustment to at least a frame rate of an image sensor of the automotive camera so that the integration time of the sensor is maintained at a maximum.

14. The method of claim 13, further comprising providing a coverglass and positioning the VCF on the coverglass.

15. The method of claim 14, further comprising mounting the coverglass on the automotive camera so that the coverglass can detached from the automotive camera.

16. The method of claim 13, further comprising positioning the VCF on an outermost lens of the lens unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] FIGS. 1a, 1b, 1c illustrate a timing diagram, depicting phases of shutter (FIG. 1a), light source pulses (FIG. 1b) and result of the superposition of the former two (FIG. 1c), when the shutter is closed for 1 ms and open for 32 ms;

[0058] FIGS. 2a, 2b, 2c illustrate a timing diagram, depicting phases of shutter (FIG. 2a), light source pulses (FIG. 2b) and result of the superposition of the former two (FIG. 2c), when the shutter is closed for 11 ms and open for 22 ms;

[0059] FIGS. 3a, 3b, 3c illustrate a timing diagram, depicting phases of shutter (FIG. 3a), light source pulses (FIG. 3b) and result of the superposition of the former two (FIG. 3c), when the shutter is closed for 15 ms and open for 18 ms;

[0060] FIGS. 4a, 4b, 4c illustrate a timing diagram, depicting phases of shutter (FIG. 4a), light source pulses (FIG. 4b) and result of the superposition of the former two (FIG. 4c), when the shutter is closed for 25 ms and open for 8 ms;

[0061] FIG. 5 is a lateral view of a first embodiment of an apparatus for light intensity adjustment in a three-dimensional representation according to an implementation form;

[0062] FIG. 6 is an exploded view of the apparatus depicted in FIG. 5;

[0063] FIG. 7 is a lateral view of an apparatus for light intensity adjustment in a three-dimensional representation according to an implementation form;

[0064] FIG. 8 is an exploded view of a second embodiment of an apparatus;

[0065] FIGS. 9a and 9b a shematic diagram of image sensor integration time, light source pulses and frame rate;

[0066] FIG. 10 a schematic top view on an optical member of the second embodiment of the apparatus.

[0067] FIG. 11a illustrates an apparatus for light intensity adjustment with a view control film (VCF) on a coverglass that functions to remove stray light entering into the lens.

[0068] FIG. 11b illustrates an apparatus for light intensity adjustment with a view control film (VCF) on a first lens that functions to remove stray light entering into the lens.

DETAILED DESCRIPTION

[0069] In the following detailed description, reference is made to the accompanying drawings, which form a part thereof, and in which is shown by way of illustration specific aspects in which the disclosure may be practiced. It is understood that other aspects may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

[0070] In the following, an automotive camera with the fixed aperture and an apparatus for light intensity adjustment is described. The apparatus can be used for controlling amount of light that reaches an image sensor, also denoted as imager of the camera. The apparatus comprises two polarizer filters, one of which may move with respect to another in such a way, that the amount of transmitted light is gradually changed. This allows keeping image sensor integration time close to the frame period, thus eliminating stroboscopic effect, when dealing with light emission diode (LED) based daytime running lamps, installed on a vehicle or strobe lights of emergency lighting.

[0071] FIG. 5 is a lateral view of an apparatus for light intensity adjustment 500 in a three-dimensional representation according to an implementation form, and FIG. 6 illustrates an exploded view of the apparatus 500, depicted in FIG. 5. The apparatus 500 includes a first 501 and a second 503 linear polarizing filter and an actuator 511. The apparatus for light intensity adjustment 500 is mountable on an automotive camera 519. Such an automotive camera 519 may include a lens unit 509 and an image sensor (not depicted in FIG. 5), comprising a plurality of light sensitive elements, configured to collect incident light projected by the lens unit 509, and transform it into an electrical signal. The image sensor may read out the charge collected by the plurality of light sensitive elements with a predetermined frame rate. The first 501 and the second 503 linear polarizing filters are arrangeable in front of the lens unit 509, such that the incident light passes through both of them before entering the lens unit 509. The actuator 511 can move the first 501 and the second 503 linear polarizing filters with respect to each other. By that movement the actuator 511 adapts a light exposure of the image sensor to the frame rate of the image sensor and lighting conditions, when the apparatus 500 is mounted on the automotive camera 519 as depicted in FIG. 5. The apparatus 500 can be mounted on the camera 519 and can be released from the camera 519. While FIG. 5 depicts an automotive camera 519, the apparatus can also be mounted on other kinds of cameras or optical systems, for example iris, telescope, glasses etc. The size of the apparatus may be fitted to a size of the optical system, whereon the apparatus is mounted.

[0072] The actuator 511 can provide a first orientation 515a of the first 501 and the second 503 linear polarizing filters in case of low-light conditions. In that first orientation 515a both filters 501, 503 polarize the incident light in a same plane. The actuator 511 can provide a second orientation 515b of the first 501 and the second 503 linear polarizing filters in case of high-light conditions. In that second orientation 515b polarization planes of both filters 501, 503 are close to be perpendicular to each other. The actuator 511 can provide a third orientation 515c of the first 501 and the second 503 linear polarizing filters in case of intermediate-light conditions. That third orientation 515c lies in between the first orientation 515a and the second orientation 515b of the linear polarizing filters 501, 503. The first orientation 515a may be a first angle, the second orientation 515b may be a second angle, and the third orientation 515c may be a third angle in between the first angle and the second angle. The first linear polarizing filter 501 may be fixedly mountable in front of the lens unit 509, and the second linear polarizing filter 503 may be movable with respect to the first linear polarizing filter 501 or vice versa. The actuator 511 may rotate the second linear polarizing filter 503 about a rotation axis 516, in particular by at least 90 degrees. The rotation axis 516 may approximately coincide with an optical axis of the lens unit 509, when the apparatus is mounted on the camera 519 as shown in FIG. 5. The apparatus 500 may include an inner ring 507, carrying the second linear polarizing filter 503, and an outer ring 505, carrying the first linear polarizing filter 501. Both, the inner ring 507 and the outer ring 505 may be aligned with the optical axis of the lens unit 509, when the apparatus 500, 600 is mounted on the camera 519. The actuator 511 may include a worm wheel 513 for moving the inner ring 507.

[0073] The automotive camera 519 may include a lens unit 509 and an image sensor, comprising a plurality of light sensitive elements, which collect incident light, projected by the lens unit 509 and transform it into an electrical signal. The image sensor may read out the charge collected by the plurality of light sensitive elements with a predetermined frame rate. FIG. 5 shows the apparatus 500, mounted on the automotive camera 519. Integration time of the image sensor for collecting the incident light may be approximately constant. The integration time of the image sensor may be close to a maximum, defined by a time period between two consecutive frame read outs.

[0074] One or more of the automotive cameras 519 together with mounted apparatus 500, 600 may be mounted on a vehicle (not depicted in the figures).

[0075] The apparatus for light intensity adjustment 500, 600 may be mounted outside of the lens unit 509 that may have a fixed stop diameter, for example in front of the first lens element. The apparatus 500 may include a pair of linear polarizing filters 501, 503, one of which may be fixed in a housing, and another can be rotated by at least 90 degrees. The optical surfaces of the filters 501, 503 may be approximately parallel to each other. The filters 501, 503 may be situated in the housing in such a way that the incident light passes through both of them before it enters the front optical element of the lens unit 509. The moveable filter, in FIGS. 5 and 6 the second linear polarizing filter 503 may be rotated by the actuator 511. Whenever the orientation of the filters 501, 503 is such that they polarize the incident light in the same plane, a maximum of the incident light may reach the lens unit 509 and the sensor. This would be the case in the low-light conditions. Whenever polarizing planes of the filters 501, 503 are close to be perpendicular to each other, only a small portion of the incident light reaches the lens and the sensor. This would correspond to the high-light conditions. Orientations of the filter polarizing planes between the two extremes described above correspond to intermediate lighting conditions.

[0076] As shown in FIGS. 5 and 6, the axis of rotation 516 of the moveable filter 503 may coincide with the optical axis of the lens 509. This configuration enables minimizing the form factor of the device. The camera 519 with the lens 509, actuator 511 and the outer ring 505 of the bearing may be mounted in the device housing. The actuator shaft may feature a worm that may be in contact with the worm wheel 513, thus making up a worm gear arrangement. The worm wheel 513 may be firmly attached to the inner ring 507 of the bearing. The stationary polarizer 501 may be attached to the outer ring 505 of the bearing, and the moving polarizer, i.e. the second polarizing filter 503 to the worm wheel 513. A torque from the actuator's rotor may be transferred to the worm, which in turn, rotates the worm wheel 513 with the attached polarizer 503 and the inner ring 507 of the bearing.

[0077] An advantage of such an apparatus 500, 600 is that a position sensor, which is typically used to determine the position of moving parts of the mechanism, is not required. The position sensor can be replaced by an algorithm that calibrates the system at the start-up by finding the position where the light intensity is at a maximum (or minimum, respectively). Measurement of the amount of light may be performed by the imager. Once a peak position has been found, other required polarizer positions can be set by counting steps of the stepper motor of the actuator 511.

[0078] The stationary outer polarizer, i.e. the first polarizing filter 501 may be equipped with an electrical heater that may be activated manually or automatically, e.g. whenever frost, snow or moisture obscures the view for the camera. This allows eliminating an additional cover glass that is typically placed in front of the lens to protect it from dirt, moisture and frost.

[0079] The logic responsible for the pixel integration time adjustment may be eliminated from the imager or supporting integrated circuit, in order to simplify its layout, thus reducing silicon area required for logic implementation and eventually save costs. In this case, pixel integration time may be fixed at the level reasonably close to the frame period. Exposure adjustment may be achieved by changing the intensity of incident light with the use of the two polarizers 501, 503.

[0080] FIG. 7 is a lateral view of an apparatus for light intensity adjustment 700 in a three-dimensional representation according to an implementation form.

[0081] The apparatus 700 includes a first 701 and a second 703 linear polarizing filter and an actuator 711. The apparatus for light intensity adjustment 700 is mountable on an automotive camera 519 as described above with respect to FIGS. 5 and 6. The first 701 and the second 703 linear polarizing filters are arrangeable in front of the lens unit 509 such that the incident light passes through both of them 701, 703 before entering the lens unit 509. The actuator 711 can move the first 701 and the second 703 linear polarizing filters with respect to each other. By that movement the actuator 711 adapts a light exposure of the image sensor to the frame rate of the image sensor and lighting conditions, when the apparatus 700 is mounted on the automotive camera 719 as depicted in FIG. 7. The apparatus 700 can be mounted on the camera 519 and can be released from the camera 519. While FIG. 7 depicts an automotive camera 519, the apparatus can also be mounted on other kinds of cameras or optical systems, for example iris, telescope, glasses etc. A size of the apparatus may be fitted to a size of the optical system, whereon the apparatus is mounted.

[0082] The actuator 711 can provide a first orientation 715a of the first 701 and the second 703 linear polarizing filters in case of low-light conditions. In that first orientation 715a both filters 701, 703 polarize the incident light in a same plane. The actuator 711 can provide a second orientation 715b of the first 701 and the second 703 linear polarizing filters in case of high-light conditions. In that second orientation 715b polarization planes of both filters 701, 703 are close to be perpendicular to each other. The actuator 711 can provide a third orientation 715c of the first 701 and the second 703 linear polarizing filters in case of intermediate-light conditions. That third orientation 715c lies in between the first orientation 715a and the second orientation 715b of the linear polarizing filters 701, 703. The first orientation 715a may be a first angle, the second orientation 715b may be a second angle and the third orientation 715c may be a third angle in between the first angle and the second angle. The first linear polarizing filter 701 may be fixedly mountable in front of the lens unit 509, and the second linear polarizing filter 703 may be movable with respect to the first linear polarizing filter 701 or vice versa. The actuator 711 may rotate the second linear polarizing filter 703 by a rotation axis 716, in particular by at least 90 degrees.

[0083] The rotation axis 718 may be approximately parallel to an optical axis 716 of the lens unit 509, when the apparatus is mounted on the camera 519 as shown in FIG. 7. The first linear polarizing filter 701 may be approximately formed as a circle (or as a polygon having n edges), having a center coinciding with the optical axis 716 of the lens unit 509, when the apparatus is mounted on the camera. The second linear polarizing filter 703 may be approximately formed as a semi circle (or as a semi polygon having n/2 edges), having a center coinciding with the rotation axis 718 of the actuator 711. Other geometrical shapes of both filters 701, 703 may be applied as well.

The apparatus 700 may include an inner semi ring 707, carrying the second linear polarizing filter 703, and an outer ring 705, carrying the first linear polarizing filter 701. The inner semi ring 707 may be aligned with a rotation axis 718 of the actuator 711. The outer ring 705 may be aligned with the optical axis 716 of the lens unit 509, when the apparatus 700 is mounted on the camera 519 as depicted in FIG. 7. The rotation axis 718 of the actuator 711 may drive the inner semi ring 707. An area of the inner semi ring 707 may be larger than an area of the outer ring 705.

[0084] One or more of the automotive cameras 519 together with mounted apparatus 700 may be mounted on a vehicle (not depicted in the figures).

[0085] The apparatus for light intensity adjustment 700 may be mounted outside of the lens unit 509 that may have a fixed stop diameter, for example in front of the first lens element. The apparatus 700 may include a pair of linear polarizing filters 701, 703, one of which may be fixed in a housing, and another can be rotated by at least 90 degrees. The optical surfaces of the filters 701, 703 may be approximately parallel to each other. The filters 701, 703 may be situated in the housing in such a way that the incident light passes through both of them before it enters the front optical element of the lens unit 709. The moveable filter, in FIG. 7 the second linear polarizing filter 703 may be rotated by the actuator 711. Whenever the orientation of the filters 701, 703 is such that they polarize the incident light in the same plane, a maximum of the incident light may reach the lens unit 509 and the sensor. This would be the case in the low-light conditions. Whenever polarizing planes of the filters 701, 703 are close to be perpendicular to each other, only a small portion of the incident light reaches the lens and the sensor. This would correspond to the high-light conditions. Orientations of the filter polarizing planes between the two extremes described above correspond to intermediate lighting conditions.

[0086] The axis of rotation 718 of the moveable filter, i.e. the second polarizing filter 703 may not coincide with the optical axis 716 of the lens unit 709 as depicted in FIG. 7. By shifting the axis of rotation 718 to be outside of the outer diameter of the lens 709, the rotation mechanism can be simplified, thus simplifying the integration and reducing the costs of the device while increasing its robustness.

[0087] The stationary outer polarizer, i.e. the first polarizing filter 701 may be equipped with an electrical heater as described above with respect to FIG. 5.

[0088] The logic responsible for the pixel integration time adjustment may be eliminated from the imager or supporting integrated circuit as described above with respect to FIG. 5.

[0089] In addition, while a particular feature or aspect of the invention may have been disclosed with respect to only one of several implementations, such feature or aspect may be combined with one or more other features or aspects of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms include, have, with, or other variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term comprise. Also, the terms exemplary, for example and e.g. are merely meant as an example, rather than the best or optimal.

[0090] Although specific aspects have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific aspects shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific aspects discussed herein.

[0091] FIG. 8 illustrates an exploded view of the apparatus 500 comprising a grey filter 801. In the shown embodiment the grey filter 801 comprises a separate part and is mounted in front of the lens unit 509.

[0092] FIG. 9a shows the integration time of an image sensor 901 and an upcoming light source pulse 902 within a frame 903 of the state of the art. Because of the relatively short integration time of the image sensor 901 an upcoming light source pulse 902 like a flash or light of a led. In the first frame 903 the upcoming light source pulse 902 is not detected by the image sensor 901. In the following frame 903 the light source pulse 902 is only detected with reduced intensity. Only in the following frame the light source pulse 902 is fully detected by the image sensor 901.

[0093] FIG. 9b shows the integration time of an image sensor 901 and an upcoming light source pulse 902 within a frame 903 according to an embodiment. Because of the extended exposure time of the image sensor 901 the light source pulse 902 is totally detected by the image sensor 901 in the second and third frame 903. Even in the first frame 903 the light source pulse 902 is detected.

[0094] FIG. 10 shows an embodiment of an optical member 904 comprising a plurality of optical elements 905. The optical member 904 can be an image sensor and/or lens of the lens unit.

[0095] The optical elements 905 are arranged in a plurality of columns 906 and rows 907. In the embodiment shown in FIG. 10 the optical elements 905 of every second row 907 comprise a grey filter 801.

[0096] FIG. 11a illustrates an apparatus for light intensity adjustment 1110 with a view control film (VCF) on a coverglass 1120 that functions to remove stray light entering into the lens unit 509.

[0097] Referring to FIG. 11a, an apparatus for light intensity adjustment 1110 is illustrated which takes the form of a VCF 1110. The VCF 1110 is positioned on a coverglass 1120. An automotive camera 519 may include a lens unit 509 and an image sensor (not depicted in FIG. 11a), including a plurality of light sensitive elements, configured to collect incident light projected by the lens unit 509, and transform it into an electrical signal. The image sensor may read out the charge collected by the plurality of light sensitive elements with a predetermined frame rate. The apparatus 1110 including the coverglass 1120 can be mounted on the camera 519 and can be released from the camera 519. While FIG. 11a depicts an automotive camera 519, the apparatus can also be mounted on other kinds of cameras or optical systems, for example iris, telescope, glasses etc. The size of the apparatus 1110 may be fitted to a size of the optical system whereon the apparatus is mounted.

[0098] In an example, the VCF 1110 will have the function of removing the stray light entering into the lens unit 509. The VCF 1110 may have the same function as a stray light cone used in photographic set-up and other camera systems.

[0099] FIG. 11b illustrates an apparatus for light intensity adjustment 1110 with a view control film (VCF) on an outer lens 1130 that functions to remove stray light entering into the lens unit 509.

[0100] Referring to FIG. 11b, an apparatus for light intensity adjustment 1110 is illustrated which takes the form of a VCF 1110. The VCF 1110 is positioned on an outer lens 1130 of a lens unit 509. The automotive camera 519 may include the lens unit 509 and an image sensor (not depicted in FIG. 11b), including a plurality of light sensitive elements, configured to collect incident light projected by the lens unit 509, and transform it into an electrical signal. The image sensor may read out the charge collected by the plurality of light sensitive elements with a predetermined frame rate. While FIG. 11b depicts an automotive camera 519, the apparatus can also be mounted on other kinds of cameras or optical systems, for example iris, telescope, glasses etc. The size of the apparatus 1110 may be fitted to a size of the optical system whereon the apparatus is mounted.

[0101] Although the elements in the following claims are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence.