EP1299760A1 - Autofocussing method for telescopes pertaining to surveying equipment - Google Patents
Autofocussing method for telescopes pertaining to surveying equipmentInfo
- Publication number
- EP1299760A1 EP1299760A1 EP01960486A EP01960486A EP1299760A1 EP 1299760 A1 EP1299760 A1 EP 1299760A1 EP 01960486 A EP01960486 A EP 01960486A EP 01960486 A EP01960486 A EP 01960486A EP 1299760 A1 EP1299760 A1 EP 1299760A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- maximum
- kkf
- signal
- signal amplitude
- local
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C15/00—Surveying instruments or accessories not provided for in groups G01C1/00 - G01C13/00
- G01C15/002—Active optical surveying means
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C1/00—Measuring angles
- G01C1/02—Theodolites
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
- G02B7/28—Systems for automatic generation of focusing signals
- G02B7/36—Systems for automatic generation of focusing signals using image sharpness techniques, e.g. image processing techniques for generating autofocus signals
Definitions
- the invention relates to a method for autofocusing, in particular for telescopes of surveying devices, and is suitable for image sensors that resolve the image signal into individual picture elements (pixels), such as CCD lines and matrices and CMOS image sensors.
- pixels such as CCD lines and matrices and CMOS image sensors.
- DE-OS 1 96 1 4 235 describes an auto focus for a level. Additional optics located behind the image plane serve to capture the focus by means of two imaging lenses that generate object images on two line sensors. Means for detecting the focusing lens position are also required.
- DE-OS 1 95 49 048 is to be seen, which uses a beam splitter to generate a plane for the focus detection system that is equivalent to the image plane.
- This solution has the disadvantage that it cannot be easily transferred to a digital level.
- JP-OS 4-93 71 1 contains an autofocus for a CCD camera connected to a tachymeter telescope via a beam splitter. A focusing lens is adjusted so that the image size of the imaged object is minimal. This solution also does not necessarily ensure optimal image sharpness, since the minimum can be relatively wide and is therefore difficult to grasp.
- US 54 81 329 describes an autofocus device with an additional image on the image plane on four sensors and correlation of the opposite, resulting images. The sum of the difference between neighboring pixels is taken as the contrast value. Depending on the success, further filters are available for other spatial frequencies. Depending on whether an object produces a high-contrast or low-contrast image, the proportion of constant light is removed completely or incompletely. The required additional optics are disadvantageous and complex in this device.
- the image contrast is at a maximum. From DE 1 95 00 81 7 it is also known to find edges as objects of greatest contrast in the image as a local maximum or minimum of the cross-correlation function (KKF) of a few pixels of the image content with an ideal edge.
- KF cross-correlation function
- the focusing path up to the next measurement is determined as a product of the ratio of the maximum signal to the local signal amplitude, the focus position in relation to the position when focusing on infinity and a constant.
- FIG. 2 shows the signal representation of a CCD line with defocused image
- FIG. 3 shows the signal representation of a CCD line with the image focused
- FIG. 4 shows a flowchart for the first part of the autofocus algorithm described in the example
- FIG. 5 shows a flowchart for the second part of the autofocus algorithm described in the example.
- FIG. 1 shows the measurement image of the CCD line of a digital level with complete defocusing.
- the x-axis 1 continuously shows the pixel number i from 0 to 1,799.
- the brightness of the respective pixel Yj is plotted in arbitrary units on the y-axis 2.
- the value 255 means no signal (black), the value 0 means maximum signal (white), which results in a negative representation.
- the measurement images according to FIGS. 1 to 3 were taken with a digital level in which, due to the design, only a little light can reach the beginning or the end of the CCD line. In principle, it is of course also possible to determine the dark signal from a separate measurement.
- the brightest point is at pixel 720.
- the signal Ymin is used in a known manner for exposure control.
- ß be kept within certain limits. For example, it must not become zero because the CCD line is then overexposed.
- the first value essential for focusing that is obtained from the measurement image is the maximum signal S]:
- FIG. 2 shows a signal representation of a CCD line with a defocused image. A certain picture content is already recognizable here.
- MPX center pixel
- the local signal amplitude S2 is calculated from the monotonically falling or rising signal up to the next local maximum Ylmax and minimum Y
- Imax the local maximum
- Imin the local minimum
- the first relationship (formula) to focus is as follows:
- Focusing path (Si / S2) »focus position • constant (7)
- S, / S2 is limited to a maximum value, e.g. 4 Fig. 4).
- rule (7) does not include the signal amplitude but the ratio 5, 7 52 has the advantage that rule (7) is independent of the amplitude. It can therefore be used before an optimal exposure control has been made. The calculations and changes in the focus position of the links for the autofocus can thus already take place during the exposure control.
- FIG. 3 shows the same object as in FIGS. 1 and 2, but in a focused state.
- the measurement curve 20 contains dark areas 21 and bright areas 22, which are separated by edges 23. The edges only extend over a few pixels of the image. The pixels 24, 25, 26 and 27 of the edge 23 are shown in FIG. 3.
- Pixels 24 to 27 have the signals in this order:
- the third function that is essential for the focusing process is the cross-correlation function (KKF), each consisting of four pixels and an ideal dark-light edge with the signals (+1; + l; -l; -l).
- KF cross-correlation function
- KKF (i) Yj + Yj + i - Yj + 2 - Yi + 3 (8)
- KKF (860) 1 09 results.
- the KKF is formed pixel by pixel.
- edges in the measurement image which lie in the region of the pixels Yj + i and Yj + 2, respectively.
- the exact position is then determined by interpolation. It is essential for the focusing process that the KKF is a measure of the image contrast.
- a reference function can be formed from the KKF maxima, which allows statements to be made about the state of focus. It is expedient and easiest to use the maximum value of the KKF in the entire image field as a reference function. With a little more effort, the mean value from the local maxima of the KKF could also be used as a reference function.
- the reference function thus formed is referred to below as KKF MAX.
- the further focusing process consists of maximizing the KKF MA ⁇ / S 2 function. Depending on the size of the KKF MA ⁇ / S 2 function, it is advisable to either set the focusing path to twice the depth of focus as long as KKF MA ⁇ / S 2 ⁇ 0.5 is. If the value 0.5 is exceeded, the focusing path is limited to the depth of field until the next measurement.
- the sequence of the focusing process is shown as a flow chart in FIG. 5.
- the focusing path can be measured or also by a suitable control of the focusing motor, e.g. a stepper motor can be set with sufficient accuracy without measurement.
- a suitable control of the focusing motor e.g. a stepper motor can be set with sufficient accuracy without measurement.
- FIGS. 4 and 5 The rules regarding focusing are summarized in FIGS. 4 and 5.
- Fig. 4 shows that rule (7) is applied until either the focus position is ⁇ 0.1 or Si / S2 falls below a value of 1.4.
- Fig. 5 shows that if one of the above conditions is met, KKF MA ⁇ / S2 is formed.
- the step size is limited to the depth of field as soon as KKF MA ⁇ / S2> 0.5. Subsequently - "t retraction up to the maximum KKF, M, AX / S2 * - '
- the invention is not limited to the example above.
- the for decision The selected constants can assume other values that are optimally adapted to the respective optical system.
- the step sizes indicated in FIG. 5 for the focusing can also assume other values, such as the whole and half the depth of focus.
- the KKF another strongly contrast-dependent function can be used. It is also possible instead of CCF MA ⁇ / S2 as decision J skriterium the function CCF. M, X A ⁇ V to use, 'only must then be eschreibt g 3 that the exposure does not change anymore during the focusing operation.
Landscapes
- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Computer Vision & Pattern Recognition (AREA)
- Optics & Photonics (AREA)
- Automatic Focus Adjustment (AREA)
- Focusing (AREA)
Abstract
Description
Claims
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE10033483A DE10033483C1 (en) | 2000-07-10 | 2000-07-10 | Auto-focusing method for telescopes of surveying equipment |
DE10033483 | 2000-07-10 | ||
PCT/EP2001/007931 WO2002005005A1 (en) | 2000-07-10 | 2001-07-10 | Autofocussing method for telescopes pertaining to surveying equipment |
Publications (1)
Publication Number | Publication Date |
---|---|
EP1299760A1 true EP1299760A1 (en) | 2003-04-09 |
Family
ID=7648419
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP01960486A Withdrawn EP1299760A1 (en) | 2000-07-10 | 2001-07-10 | Autofocussing method for telescopes pertaining to surveying equipment |
Country Status (4)
Country | Link |
---|---|
US (1) | US6927376B2 (en) |
EP (1) | EP1299760A1 (en) |
DE (1) | DE10033483C1 (en) |
WO (1) | WO2002005005A1 (en) |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP4201924B2 (en) * | 1999-06-28 | 2008-12-24 | 株式会社 ソキア・トプコン | Surveyor autofocus mechanism |
DE10033483C1 (en) | 2000-07-10 | 2002-01-03 | Zsp Geodaetische Sys Gmbh | Auto-focusing method for telescopes of surveying equipment |
DE10349030B4 (en) * | 2003-10-13 | 2005-10-20 | Gkn Driveline Int Gmbh | axial setting |
DE102005053555B3 (en) * | 2005-11-08 | 2007-08-02 | Gkn Driveline International Gmbh | Ball ramp arrangement with variable pitch of the ball grooves |
EP2047212B1 (en) * | 2006-08-01 | 2012-04-04 | Trimble Jena GmbH | Electronic leveling apparatus and method |
US7627429B2 (en) * | 2006-09-15 | 2009-12-01 | Schlumberger Technology Corporation | Method for producing underground deposits of hydrocarbon from an earth formation using fault interpretation including spline fault tracking |
EP3839424A1 (en) | 2019-12-19 | 2021-06-23 | Leica Geosystems AG | Geodetic surveying telescope with image sensor focus |
Family Cites Families (17)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5078321A (en) * | 1973-11-09 | 1975-06-26 | ||
GB2003692B (en) * | 1977-09-02 | 1982-08-11 | Olympus Optical Co | Method for detecting a focalisation or in-focussed-condition of an optical system |
JPS5616806A (en) * | 1979-07-20 | 1981-02-18 | Hitachi Ltd | Surface roughness measuring unit |
US4371866A (en) * | 1980-11-21 | 1983-02-01 | The United States Of America As Represented By The Secretary Of The Army | Real-time transformation of incoherent light images to edge-enhanced darkfield representation for cross-correlation applications |
DE3339970A1 (en) | 1983-11-04 | 1985-05-15 | Karl Süss KG, Präzisionsgeräte für Wissenschaft und Industrie GmbH & Co, 8046 Garching | DEVICE FOR AUTOMATIC FOCUSING OF OPTICAL DEVICES |
US4639587A (en) * | 1984-02-22 | 1987-01-27 | Kla Instruments Corporation | Automatic focusing system for a microscope |
US4677286A (en) * | 1985-02-14 | 1987-06-30 | Quantronix Corporation | Method and apparatus for autofocusing a microscope |
JPH0610694B2 (en) * | 1985-04-12 | 1994-02-09 | 株式会社日立製作所 | Automatic focusing method and device |
US4804831A (en) | 1985-10-30 | 1989-02-14 | Canon Kabushiki Kaisha | Focus detecting apparatus independent of object image contrast |
JPH0738046B2 (en) | 1987-03-30 | 1995-04-26 | 新王子製紙株式会社 | Surface inspection device for semi-transparent sheet-like samples with internal structure |
US4945220A (en) * | 1988-11-16 | 1990-07-31 | Prometrix Corporation | Autofocusing system for microscope having contrast detection means |
JP3444551B2 (en) * | 1994-05-11 | 2003-09-08 | オリンパス光学工業株式会社 | Camera focus detection device |
JP3708991B2 (en) * | 1994-12-28 | 2005-10-19 | ペンタックス株式会社 | Inner focus telescope |
DE19500817C1 (en) * | 1995-01-13 | 1996-02-22 | Zeiss Carl Jena Gmbh | Edge position measurement method for light-dark structure |
DE19614235C2 (en) * | 1995-04-10 | 2001-06-28 | Asahi Optical Co Ltd | Surveying instrument with auto focus system |
JP2000125177A (en) * | 1998-10-12 | 2000-04-28 | Ricoh Co Ltd | Automatic focusing unit |
DE10033483C1 (en) | 2000-07-10 | 2002-01-03 | Zsp Geodaetische Sys Gmbh | Auto-focusing method for telescopes of surveying equipment |
-
2000
- 2000-07-10 DE DE10033483A patent/DE10033483C1/en not_active Expired - Lifetime
-
2001
- 2001-07-10 US US10/070,580 patent/US6927376B2/en not_active Expired - Lifetime
- 2001-07-10 WO PCT/EP2001/007931 patent/WO2002005005A1/en active Application Filing
- 2001-07-10 EP EP01960486A patent/EP1299760A1/en not_active Withdrawn
Non-Patent Citations (1)
Title |
---|
See references of WO0205005A1 * |
Also Published As
Publication number | Publication date |
---|---|
US6927376B2 (en) | 2005-08-09 |
DE10033483C1 (en) | 2002-01-03 |
WO2002005005A1 (en) | 2002-01-17 |
US20030089837A1 (en) | 2003-05-15 |
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