• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention relates to a process for stray light compensation of an IR camera. According to the process, it is included that: a) stray light images are measured in production for at least two different camera temperatures against flat radiators and stored (11), b) the stray light is measured directly in image during operation for a selection, such as one or more lines, a few points or the whole image (14) and the made selection is low-pass filtered (15), c) corresponding selections are made in the stray light images (21), d) the selection from the stray light is matched against corresponding selections in the stray light images by calculating the factor which makes the most points from the selections coincide (22), e) image during operation is compensated with calculated factor of matched stray light image (23-29).
    公开号:SE1130090A1
    申请号:SE1130090
    申请日:2011-09-22
    公开日:2012-10-09
    发明作者:Odd Larson；Emanuel Johansson
    申请人:Flir Systems Ab；
    IPC主号:
    专利说明:

    15 20 25 30 out differently than in the focused mode. This results in a new stray light originating from the defocused position being added to the stray light in focused position.
    Summary of the Invention An object of the invention is to provide a method which can compensate for low frequency noise in the form of stray light in the camera.
    The object of the invention is achieved by a method characterized in that: a) stray light images are measured in production for at least two different camera temperatures against flat radiators and stored, b) the stray light is measured directly in image during operation for a selection, such as one or fl your lines, a few points or the whole image and the selection made is low-pass filtered, c) the corresponding selection is made in the scattering light images, d) the selection from the scattering light is matched against the corresponding selection in the scattering light images by calculating the factor that makes most points from the selection match, e) image during operation is compensated calculated factor of matched stray light image.
    The method ensures that low-frequency scene content does not destroy the measurements and that very noise-free images can be generated.
    According to a further development of the method, it is proposed that points in the selection from the stray light which deviate from the stray light shape according to the selection in the stray light images are eliminated. Spot lights have a characteristic shape that allows deviating shapes to be identified and excluded.
    Examples of deviating shapes can be sharp notches, steep peaks and the like.
    By first removing parts that deviate from the stray light shapes, a subsequent matching is facilitated and a more effective stray light compensation is achieved.
    According to another further development of the method, it is proposed that the selection directly in the image consists of the two diagonal lines of the image. By making a diagonal selection, the image is covered from corner to corner and a very representative selection is obtained under normal conditions without having to handle excessive amounts of data, which facilitates compensation in almost real time. 10 15 20 25 30 According to an alternative to the method according to the previous paragraph, the selection directly in the image consists of at least one horizontal line and at least one vertical line in the image. This selection also advantageously covers the image without the need for excessive amounts of data.
    The calculation of the factor that causes the most points from the samples to match is performed with advantage using the least squares method. However, other calculation methods can also be applied.
    According to a further development of the method, where the offset folder is made during operation against a defocused scene or against a shovel, low-pass noise is eliminated by the offset folder being high-pass filtered and the offset folder being compensated with a calculated factor of matched stray light image. The high-pass filtering prevents new stray light coming from calibration towards defocused scene or towards shovel from being added.
    According to a further development of the method, the low-frequency noise is compensated to an even greater extent by generating offset folders in production for compensating for low-frequency noise in the detector.
    The scattering light compensation can be performed separately in operation or coordinated with other activities. A preferred further development of the method is to perform the stray light compensation in connection with offset calibration in operation.
    The diffuser compensation can be performed, for example, in combination with optics NUC or spade NUC.
    Spotlight images that are measured in production should be made for at least two camera temperatures.
    Separately, it is proposed that stray light images be measured in production for at least three camera temperatures, of which one camera temperature corresponds to room temperature and at least one camera temperature is lower and at least one camera temperature is higher than room temperature. BRIEF DESCRIPTION OF THE DRAWINGS The invention according to the stated methods will be further described below with reference to the accompanying drawings where: Lie schematically shows a detector matrix to be housed in an IR camera.
    Lie schematically shows a memory circuit.
    Figures 3a and 3b in a block diagram illustrate an example of a method according to the invention for compensating for stray light and thus also for handling other noise. The transition between Figure 3a and Figure 3b is shown in the drawings by means of a dotted line.
    Detailed embodiment description Detectors included in a detector matrix of an IR camera do not behave the same but show variations in gain and offset. To handle these variations, so-called gain and offset folders are preferably recorded and stored already in production. Using the gain folder is corrected during operation for gain variations of the individual detectors in a matrix. Correspondingly, the offset map is used to shift the detector signals of the input detectors in parallel during operation so that the gain curves of the detectors substantially coincide. To further illustrate the principles behind gain and offset mapping, reference is made to our published US patent application US 2011/0164139 A1.
    Figure 1 schematically illustrates a detector natris 1 housed in an IR camera which is only indicated in box form with dashed lines. The detector array 1 comprises rows and columns with detectors 2, whose gain and offset folders after they have been taken into production have been stored and are illustrated here in Figure 2 with a memory circuit 4 accommodating gain folder 5 and offset folder 6. In addition there is space for storing stray light images, which will be described in more detail in another context below. Although the memory circuit here is shown as a separate unit, folders and stray light images can be stored separately. As a memory circuit, each suitable type of memory can be included and, for example, memory types suitable for interaction with microcomputers. With reference to a schematic fate diagram shown in Figures 3a and 3b, the principles of stray light compensation and related mapping are now described. To more clearly mark the stray light compensating part, it has been circled by means of a dashed loop 31.
    In connection with the production of an IR camera 3, gain and offset maps 5, 6 are suitably accommodated. Block 7 in Figure 3 illustrates this mapping in production. Furthermore, offset mapping is performed during normal operation of the IR camera. This is illustrated by block 8.
    Offset mapping can be performed according to the principle of optical NUC, ie by defocusing the scene the IR camera is showing, for example by moving optical elements such as lenses, and performing the mapping towards the defocused scene which shows great smoothness. Another possible principle is spade-NUC when a spade-like object is inserted into the beam path when picking up the offset folder.
    In order to eliminate low-frequency contributions from the stage and from the optics in the defocused mode, a high-pass filtering is performed according to block 9. Thus, an offset folder is developed which, from a noise point of view, can handle the high-frequency noise in a favorable way.
    To handle scattering us, scattering light images are measured in production for different temperatures against flat radiators and stored in a memory, such as the memory 4 shown in figure 2 with a section 10 for scattering light images. The process of measuring stray light images is illustrated in Figure 3a with block 1 1. The stray light measurement in production requires measurement at at least two temperatures. It may be appropriate to cover a temperature range of perhaps 40 degrees, with measuring points of, for example, + 10 degrees and +35 degrees. To increase accuracy, measurements can be made at fl more than two measuring points, which in particular should provide more effective scattering light compensation at the edges of an image. In particular, it is proposed to place a measuring point at room temperature.
    A block12 illustrates an image available during operation in the IR camera 3. 10 15 20 25 30 To find out how high the level of the disturbance light is, a match is made of stored disturbance images, block II, with the current direct image, block 12, according to the principles described below.
    Based on the current live image, a selection is first made. The selection can be made so that one or fl your lines in the image, a few dots or the whole image are processed. By limiting the selection to a few lines or a few points, the calculation time can be kept down. In particular, it is suggested to select the two diagonals in the image. Other suitable choices may be some parallel lines and some horizontal lines.
    For the sake of clarity, a selection is described below which consists of a single horizontal line 13 shown in a block 14 to show the principle behind the stray light compensation. Such a horizontal line as well as other examples of selection also contain stage content that has nothing to do with the stray light. To separate the stray light information from the rest of the image, a low-pass filtering of the horizontal line is performed first, see block 15. It can then be checked whether the low-pass filtered line has a shape that matches the shape of the stray light. Points that deviate significantly, such as sharp notches or steep peaks, are eliminated. A block 16 indicates a comparison between the low-pass filtered horizontal line and characteristics of the scattering light shape obtained from block 17. After low-pass filtering and elimination of any points, a line 19 is obtained which may have a curve shape schematically shown in block 18.
    Previously, stray light images taken during the production phase are stored. The block 11 makes such images available and the corresponding line 21 in the spotlight images is produced and schematically exemplified in block 20.
    Now there is a line 19 representing part of the direct image of the IR camera and lines 21 representing known curves from stray light images. In a block 22, the curve shape of the line 19 is now matched against the 21 curve shapes of the line by calculating the factor X which causes the most pixels from the curves to match. The calculation can be performed using the least squares method. Block 22 illustrates the equation and delivers the calculated factor X. Block 22 may also include a reasonableness assessment of calculated factor X. The selected factor X is then multiplied by the stray light image that best corresponds to line 19, see block 23. A connection 24 shows in this case that the stray light image can be retrieved from the block 11 and a connection 25 points out the current stray light image. The multiplication results in a stray light folder marked by a block 26. This stray light folder is placed in a block 27 together with the offset folder generated in block 8 and high-pass filtered in block 9 to a folder 28 which is applied to the IR camera direct image represented by block 12 in a block 29 resulting in a finished image, block 30, compensated for stray light and other both low-frequency and high-frequency noise.
    The invention is not limited to the methods described above by way of example, but may be subject to modifications within the scope of the appended claims.
    权利要求:
    Claims (10)
    [1]
    Method for scattering light compensation of IR camera, characterized in that: a) scattering light images are measured in production for at least two different camera temperatures against flat radiators and stored, b) the scattering light is measured directly in image during operation for a selection, such as one or fl era lines, a few points or the whole image and the selection made is low-pass filtered, c) the corresponding selection is made in the stray light images, d) the selection from the stray light is matched against the corresponding selection in the stray light images by calculating the factor that makes fl est points from the selection match, e) image during operation is compensated with calculated factor of matched stray light image.
    [2]
    Method according to Claim 1, characterized in that points in the sample from the stray light which deviate from the shape of the stray lice according to the selection in the stray light images are eliminated.
    [3]
    Method according to one of the preceding claims, characterized in that the selection directly in the image consists of the two diagonal lines of the image.
    [4]
    Method according to one of the preceding claims 1-2, characterized in that the selection directly in the image consists of at least one horizontal line and at least one vertical line in the image.
    [5]
    Method according to one of the preceding claims, characterized in that the factor is calculated by means of the least squares method.
    [6]
    Method according to one of the preceding claims, wherein an offset folder is made during operation against a defocused scene or against a shovel, characterized in that the offset folder is high-pass filtered and that the offset folder is compensated by a calculated factor of matched stray light image.
    [7]
    Method according to one of the preceding claims, characterized in that offset folders are generated in production for compensating for low-frequency noise in the detector. 10
    [8]
    Method according to one of the preceding claims 6 or 7, characterized in that the stray light compensation is carried out in connection with offset calibration in operation.
    [9]
    Method according to one of the preceding claims 6 to 8, characterized in that the stray light compensation is carried out in combination with optic NUC.
    [10]
    Method according to one of the preceding claims 6 to 8, characterized in that the stray light compensation is carried out in combination with a spade NUC. Method according to one of the preceding claims, characterized in that stray light images are measured in production for at least three camera temperatures, of which one camera temperature corresponds to room temperature and at least one camera temperature is lower and at least one camera temperature is higher than room temperature.
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    法律状态:
    2021-10-12| NUG| Patent has lapsed|
    优先权:
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