JP2002064752A - Shutter calibration method - Google Patents

Abstract

(57) Abstract: Provided is a method of calibrating a shutter of a camera having a charge-coupled device. In a camera having a charge coupled device, (a) generating a first set of data from a test source using (a) electronic shuttering of the charge coupled device; Generating a second set of data from the test source 8 using both the mechanical shutter 12 of the camera 4 and the electronic shuttering of the charge coupled device 14; and (c) the first data set. And the second set of data, and (d) adjusting the exposure time of the mechanical shutter 12 in response to the comparison. To provide a calibration method for the exposure time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates generally to calibration techniques, and more particularly, to calibrating the exposure time of a mechanical shutter in a camera.

[0002]

2. Description of the Related Art Conventionally, in digital cameras, the exposure time is controlled using a mechanical shutter. The shutter receives an electric signal, and the shutter opens and closes according to the electric signal. Due to the electrical and mechanical time constants, there is a delay from this electrical signal until the shutter closes mechanically. This delay is shown in FIG. This delay time varies from shutter to shutter due to manufacturing variations, but typical delay times are in the range of 1-3 milliseconds. To control exposure precisely, manufacture precision parts with very narrow delays, or
Either measure or compensate for the shutter delay of each camera.

[0003]

One prior art technique for measuring shutter delay is to mount a camera shutter device, along with a light source, photodetectors, appropriate electronics, and an oscilloscope, in a fixture. It is to be mounted. The light passing through the shutter is measured by a photodetector, and an oscilloscope connected to the photodetector is used to measure the shutter delay. If the operator examines the oscilloscope, the delay of the shutter is known. This prior art technique of measuring shutter delay is labor intensive and does not account for all of the camera electronics.

[0004]

According to the principles of the present invention,
When the exposure time of a mechanical shutter is calibrated, the time delay of that mechanical shutter becomes apparent. Charge-coupled device (ch
The first set of data is generated from the test source using electronic shuttering of an arge coupled device (hereinafter referred to as “CCD”).
A second set of data is generated from the test source using the mechanical shutter of the camera and the electronic shuttering of the CCD. Next, the first set of data is compared with the second set of data. If necessary, adjust the exposure time of the mechanical shutter.

In accordance with a further principle of the present invention, a first set of data is generated by exposing a CCD to a test source and capturing an image of the test source with the CCD. Transfer the captured image from the CCD,
A first set of data is generated from the captured images. A second set of data is generated in the same manner as the first set, except that after the mechanical shutter exposure time, the mechanical shutter blocks the CCD from the test source.

[0006] As the description proceeds, other objects of the present invention,
Benefits and capabilities become more apparent.

[0007]

FIG. 2 shows an embodiment of the system 2 of the present invention. The system 2 includes a camera 4, a calibrator 6, and a test source 8. In the illustrated embodiment, the calibrator 6 is a separate device from the camera 4 and communicates with the camera 4. Instead, the calibrator 6 is embodied inside the camera 4 as one part of the camera 4.

[0008] The camera 4 can be any camera having a mechanical shutter. The camera 4 includes a lens unit 10 having a mechanical shutter 12, a CCD 14,
And a control device 16. Optional camera 4
Also includes a storage device 18 and an interface 20.

The lens unit 10 also includes a lens,
Includes the above openings and the structural supports needed to hold and adjust the lens and mechanical shutter 12. The mechanical shutter 12 can be any type of shutter that can be used in a camera that can selectively pass or block light from the test source to the CCD 14. C
The CD 14 may be any device that converts light into data. By the prior art, CC
D produces a voltage output whose amplitude is CCD
It depends on the amount of light that enters the surface. Then, this voltage output is converted into digital data.

The control device 16 may be any device that controls the operation of the camera 4. The storage device 18
Any device that stores data or executable code. The storage device 18 may be any type of storage device, for example, optical, magnetic, electrical, and the like. In an embodiment in which there is no data to be stored in the camera 4, the storage device 18 can be omitted.

The interface 20 may be any type of interface capable of exchanging information between the camera 4 and the calibrator 6. For example, interface 20 may be a standard serial port, a universal serial port, a parallel port, or an infrared port. When the calibrator 6 is a component of the camera 4, the interface 20 can be omitted.

The calibrator 6 can be any device that can be used to compare sets of data and issue commands to the camera 4. Calibrator 6
Includes a processor 22 and, optionally, an interface 24 and a storage device 26.

The processor 22 may be any type of processor that controls the calibrator 6 by comparing two sets of data to each other. For example, the processor 22 can be a computer processor or a circuit.

Interface 24 may be any type of interface that allows information to be exchanged between camera 4 and calibrator 6. For example, interface 24 may be a standard serial port,
It can be a universal serial port, a parallel port, or an infrared port. Calibrator 6 is camera 4
The interface 24 can be omitted in the case of the component.

The storage device 26 can be any device that stores data or executable code. The storage device 26 is, for example, optically, magnetically,
It may be any type of storage device, such as electrical. In an embodiment in which there is no data to be stored in the calibrator 6, the storage device 26 can be omitted.

Test source 8 may be any light test source suitable for use in calibrating mechanical shutter 12. For example, test source 8
Can be a uniform diffuse light source.

FIG. 3 is a flowchart showing each step of the present invention. Although the steps depicted in FIG. 3 are in a particular order, the invention encompasses permutations of the steps. Further, additional steps may be performed between the steps shown in FIG. 3 without departing from the scope of the present invention.

With the mechanical shutter 12 open,
A first set of data is generated by using only the electronic shuttering of the CCD 14 (28). Light from the test source 8 enters the CCD 14, which produces a voltage that is converted to digital data.
From this digital data, a first set of data is generated. The first set of data may be any type of set of data useful to indicate exposing CCD 14 to test source 8. For example, the first set of data may be a histogram of color values or an average of color values. In one embodiment, the first set of data is the average value of the histogram of only one color pixel of the CCD 14.

Prior to generating the first set of data (28), it may be desirable or necessary to adjust the camera exposure time to provide a properly exposed test source 8 to the CCD 14. Proper exposure refers to exposure in which the voltage from the CCD is between the maximum and minimum voltages. Voltages in the middle range between the maximum and minimum voltages are most desirable.

FIG. 4 illustrates the generation of the first set of data,
2 shows states of various control signals in the camera 4. The exposure time for the first set of data is the time from resetting the CCD 14 to transferring information from the photodiode of the CCD 14 to the register. This time is called the electronic shuttering exposure time.

The first set of data is stored (30) after generation (28) for later use. The first set of data is stored in the storage device 18 of the camera 4 or
Alternatively, they are communicated through the interfaces 20 and 24 and stored in the storage device 26 of the calibrator 6.

Using both the mechanical shuttering of the shutter 12 and the electronic shuttering of the CCD 14,
A second set of data is generated (32). The second data set is of the same type as the first data set. FIG. 5 shows the camera 4 during the generation of the second set of data.
1 shows the states of various control signals within the control signal.

A second set of data is generated (3
At 2), the exposure time of the electronic shuttering is either increased or remains the same as at 28 when the first set of data was generated. If the electronic shuttering exposure time has not increased, the mechanical shutter delay will cause the mechanical shutter to close after the electronic shuttering exposure time. Then,
The second set of data will not properly reflect the mechanical shutter delay.

The first data set and the second data set are compared (34). If the first data set and the second data set match within an allowable error (36), the adjustment of the exposure time of the mechanical shutter 12 is unnecessary. However, if the first data set and the second data set do not match within an allowable error (36), the exposure time of the mechanical shutter 12 is adjusted (38). The exposure time is adjusted manually or automatically by the calibrator 6 (38).

When the exposure of the test source 8 to the CCD 14 is smaller in the second data set than in the first data set, the exposure time of the mechanical shutter 12 is increased. Conversely, compared to the first set of data,
In the case where the exposure of the test source 8 to the CCD 14 is larger in the set of data, the exposure time of the mechanical shutter 12 is reduced.

After adjusting the exposure time, it is desirable to repeat the process to ensure that the exposure time has been properly calibrated to compensate for the mechanical shutter 12 time delay. Further, for a camera 4 having many openings, it is desirable to calibrate each opening. Furthermore, some cameras 4 use the interlaced CCD 12 to capture an image. For such a camera 4, the first set of data and the second set of data are:
It is desirable to generate from only the first transfer of the photodiode. Depending on the camera 4, the frame transfer CCD 1
Some use 2. For such a camera 4, it is desirable to generate the first set of data and the second set of data using only certain small areas of the CCD.

The foregoing description is merely illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the invention is intended to cover such alternatives, modifications, and variations that fall within the scope of the appended claims.
And variants.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a shutter delay for a mechanical shutter.

FIG. 2 is a block diagram illustrating one embodiment of a system of the present invention for calibrating a camera to accommodate mechanical shutter shutter delays.

FIG. 3 is a flowchart illustrating a method of the present invention for calibrating a camera to adapt to the shutter delay of a mechanical shutter.

FIG. 4 is a conceptual diagram showing various signals and times for capturing an image using only electronic shuttering of a charge coupled device (CCD) of a camera.

5 is a conceptual diagram showing the same signals as in FIG. 4 when capturing an image using both mechanical shuttering and electronic shuttering of a CCD.

[Explanation of symbols]

 2 System 4 Camera 8 Test source 12 Mechanical shutter 14 CCD

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/225 H04N 5/225 G // H04N 101: 00 101: 00 (72) Inventor David Kay Campbell Moffat Avenue, Lavland, 80538, Colorado, USA 3315 (72) Inventor Gregory Buoy Hofer Ridgecrest Drive, Roverland, Colorado, 80537, Colorado, USA 1864 (72) Inventor Shinichi Suzuki Maenocho, Itabashi-ku, Tokyo 2-36-9 Asahi Gaku Kogyo Co., Ltd. (72) Inventor Masahiro Ohno 2-36-9 Maeno-cho, Itabashi-ku, Tokyo F-term in Asahi Gaku Kogyo Co., Ltd. 2H054 AA01 2H081 CC53 CC58 EE04 EE06 2H082 BB02 BB23 BB76 BB78 5C022 AA13 AB17 AB31 AC32 AC42 AC52 5C024 BX01 CX56 CY44 DX04 HX15 HX29

Claims (10)

[Claims] 1. A camera having a charge-coupled device, comprising: (a) generating a first set of data from a test source using electronic shuttering of the charge-coupled device; Generating a second set of data from the test source using both a mechanical shutter and the electronic shuttering of the charge coupled device; and (c) generating the first set of data and the second set of data. And d. Adjusting the exposure time of the mechanical shutter in response to the comparison. 2. A method of calibrating the exposure time of a mechanical shutter, the method comprising: 2. The method of claim 1, further comprising: (a) exposing the charge-coupled device to the test source; and (b) using the charge-coupled device to image the test source. And (c) transferring the captured image from the charge coupled device; and (d) generating the first set of data from the captured image. The method of claim 1. 3. The step of generating the second set of data includes: (a) exposing the charge coupled device to the test source; and (b) capturing an image of the test source. c) closing the mechanical shutter; (d) transferring the captured image from the charge coupled device; and (e) generating the second set of data from the captured image. The method of claim 1 comprising: 4. The set of first and second data is:
The method of claim 1, wherein the average value is the color value of the test source. 5. The set of the first and second data,
The method of claim 1, wherein the test source is a histogram of color values. 6. A test source; (b) a charge-coupled device having electronic shuttering; (c) a mechanical shutter that shields the test source from the charge-coupled device; and (d) the charge-coupled device. Means for generating a first set of data from the test source using the electronic shuttering of the device; and (e) using both the mechanical shutter and the electronic shuttering of the charge coupled device. Means for generating a second set of data from the test source; (f) means for comparing the first set of data with the second set of data; and (g) responding to the comparison. Means for adjusting the exposure time of the mechanical shutter, wherein the exposure time of the mechanical shutter of the camera is calibrated. 7. The means for generating the first set of data comprises: (a) means for exposing the charge coupled device to the test source; and (b) capturing an image of the test source with the charge coupled device. 7. The means of claim 6, further comprising: (c) means for transferring the captured image from the charge coupled device; and (d) means for generating the first set of data from the captured image. The described system. 8. The means for generating the second set of data includes: (a) means for exposing the charge coupled device to the test source; and (b) means for capturing an image of the test source. c) means for closing the mechanical shutter; (d) means for transferring the captured image from the charge coupled device; and (e) means for generating the second set of data from the captured image. 7. The system of claim 6, comprising the system. 9. The set of first and second data is:
7. The system of claim 6, wherein the test source is an average of the color values. 10. The system of claim 6, wherein said first and second sets of data are histograms of color values of said test source.