CN1411285A - Calibration method of electric charge coupler response linearity - Google Patents

Abstract

This invention discloses a method for calibrating the response linearity of a charge coupled device which is to sample facula lattice of back focus plane of Fourier lens with charge coupled device by Fourier lens convergence using single colour plane illumination diffraction screen to get the output array value of the facula lattice and to analyse facula strength theory distribution value and output gray value sampled by charge coupled device computed from Fraumnhofer diffraction theory to realize the calibration for response linearity of the charge coupled device.

Description

A kind of scaling method of electric charge coupler response linearity

The present invention relates to a kind of scaling method of electric charge coupler response linearity, relate in particular to a kind of by measuring the method that charge coupled device input light intensity and output gray level value response curve carry out the electric charge coupler response linearity demarcation.

Charge coupled device is a kind of new electrooptical device, can utilize its this Characteristics Detection Be Controlled object usually according to its its input intensity variations of gray scale output change detection.But because charge coupler response non-linear, and the response difference between each picture dot of charge coupled device, need demarcate to electric charge coupler response linearity.The demarcation of electric charge coupler response linearity at present mainly contains damped method and divided beams method.

Damped method is to make light pass through one group of attenuator or different diaphragm of clear aperture that transmitance is different, realization is fixed than regulating to incident light, and make this group incident light enter charge coupled device, demarcate the response linearity of charge coupled device by the charge coupled device measured value that obtains therefrom.The defective of this method is and need repeatedly samples, so stated accuracy is subjected to intensity of light source fluctuating to influence bigger.

The divided beams method is to utilize the light-dividing principle of wedge, one side at wedge is plated the film that is all-trans, one side is plated spectro-film, a branch of directional light is after wedge repeatedly reflects, form the certain light beam of a series of beam intensity ratios, assemble through a fourier transform lens again, and make charge coupled device place fourier transform lens back focal plane place, once sampling can obtain the response of one group of light intensity, can demarcate the response linearity of charge coupled device thus.The defective of this method is that processing, the plated film to wedge have relatively high expectations, and light path is difficult for adjusting, and easily introducing bigger off-axis aberration influences optical quality on the focal plane, thereby influences stated accuracy.

The objective of the invention is to overcome the deficiency of existing method and a kind of method of demarcation electric charge coupler response linearity simple in structure is provided.

For finishing above-mentioned purpose, the inventive method comprises the following steps:

Making slit diffraction screen is selected the diffraction screen parameter, makes the target surface of the primary maximum width of diffraction and charge coupled device to be measured measure-alike;

After fourier transform lens placed diffraction screen, and charge coupled device to be measured is placed the back focal plane position of fourier transform lens;

Utilize a branch of monochromatic planar light irradiation diffraction screen, carry out the sampling of charge coupled device output gray level value to be measured, obtain diffraction pattern output gray level value;

Calculate spot intensity theoretical distribution value, and with the hot spot output gray level value of charge coupled device sampling to be measured relatively, realize demarcation to electric charge coupler response linearity to be measured.

Method of the present invention can also be finished through the following steps:

Described diffraction screen can be made as double slit (single seam, many seams, square hole or circular hole) diffraction screen;

The described sampling of carrying out charge coupled device output gray level value to be measured can obtain the hot spot output gray level value of (the stitching diffraction screen) of continuous (square hole, single seam, diffraction from circular aperture screen) or serial dot matrix more.

The present invention has following advantage with respect to existing method: utilize the light distribution of double slit (single seam, many seams, square hole or circular hole) diffraction accurately to provide with the Fraunhofer diffraction theory, obtain the theoretical value of its distribution.Conversion character according to Fraunhofer diffraction and fourier transform lens, utilize a branch of monochromatic planar light irradiation diffraction screen, measure its diffraction distribution value with tested charge coupled device,, obtain the non-linear deviation of tested charge coupled device by comparing and measuring the difference of value and theoretical value.Because it is simple in structure that this method adopts, so debugging is convenient to Project Realization easily.And, be beneficial to the uniformity of test charge coupled apparatus owing to utilize monochromatic planar light light source.In addition, owing to can obtain the certain sampled value of a series of light distribution relations, demarcate the influence that electric charge coupler response linearity has avoided light source to rise and fall thereby make by single exposure.Especially this method optics processing of not needing to have relatively high expectations is so cost is lower.

The present invention is further illustrated below in conjunction with drawings and Examples (selecting the two-slit diffraction screen).

Fig. 1 is the light channel structure figure that the method for the embodiment of the invention adopts.

Fig. 2 is the spot intensity theoretical distribution figure of the embodiment of the invention.

Fig. 3 is the hot spot dot chart of the embodiment of the invention.

The embodiment of the invention comprises the following steps: as shown in Figure 1, the embodiment of the invention is utilized a branch of monochromatic planar light irradiation two-slit diffraction screen 1, assemble to its back focal plane through fourier transform lens 2, charge coupled device to be determined 3 is placed the back focal plane position of fourier transform lens 2.Select following parameter: the focal distance f=1200mm of fourier transform lens 2, the target surface 3.2 * 2.4mm of charge coupled device 3 to be determined, the wavelength X of the monochromatic planar light of incident=1.064 μ m.

Half width according to the primary maximum of single slit diffraction is: $\mathrm{\Δx}=\frac{\mathrm{\λf}}{a}$

Select the diffraction screen parameter: slit stitches wide a=0.4mm, makes the primary maximum of single slit diffraction be full of the target surface of charge coupled device 3.

Spacing according to two-beam interference the two poles of the earth large spot is: $\mathrm{\Δx}=\frac{\mathrm{\λf}}{d}$

Select double slit apart from d=10mm, make d=ma (m=1,2,3 ... n), thereby on the target surface of the back focal plane of fourier transform lens 2 that is charge coupled device 3, obtain one group of (m) spacing by slit centre-to-centre spacing d determine, the certain hot spot dot matrix of strength relationship, as shown in Figure 3.

Carry out the sampling of charge coupled device 3 output gray level values, obtain the gray value of a series of hot spot dot matrix outputs.

According to the conversion character of double slit Fraunhofer diffraction and fourier transform lens, derive the light spot energy relation of charge coupled device 3 samplings:

Monochromatic plane wave vertical illumination diffraction screen, the COMPLEX AMPLITUDE of aperture plane is: $E\left(x_1\right)=\mathrm{rect}\left(\frac{x_1-d/2}{a}\right)+\mathrm{rect}\left(\frac{x_1+d/2}{a}\right)----\left(1\right)$

Behind lens, the COMPLEX AMPLITUDE of the Fraunhofer diffraction style that forms in the focal plane can be obtained by Fourier transform: $E\left(x\right)=F{\left(E\left(x_1\right)\right)}_{n=x/\mathrm{\λf}}=F\left(\mathrm{rect}\left(\frac{x_1-d/2}{a}\right)\right)+F\left(\mathrm{rect}\left(\frac{x_1+d/2}{a}\right)\right)----\left(2\right)$

By the phase shift theorem of the upright conversion of Fu Ye, 2. formula can be written as: $E\left(x\right)=\exp (-i2\mathrm{\πu}(d/2))F\left(\mathrm{rect}(x_1/a)\right)+\exp (-i2\mathrm{\πu}(-d/2))F\left(\mathrm{rect}(x_1/a)\right)$ $=(\exp (-\mathrm{i\πud})+\exp \left(\mathrm{i\πud}\right))a\sin c\left(\mathrm{au}\right)$ $=2a\sin c\left(\frac{\mathrm{ax}}{\mathrm{\λf}}\right)\cos {\left(\frac{\mathrm{\πxd}}{\mathrm{\λf}}\right)}_{n=x/\mathrm{\λf}}----\left(3\right)$ Intensity distributions is: $I\left(x\right)=|E\left(x\right){|}^2=I\left(0\right)\sin c^2\left(\frac{\mathrm{ax}}{\mathrm{\λf}}\right){\cos }^2\left(\frac{\mathrm{\πxd}}{\mathrm{\λf}}\right)----\left(4\right)$ I in the formula (O) is the intensity distributions at diffraction pattern center;

4. formula shows that the intensity distributions of two-slit diffraction is by the single slit diffraction factor and the coefficient result of the two-beam interference factor.Figure 2 shows that the intensity distributions of hot spot.

4. calculate the theoretical distribution value of hot spot dot matrix according to formula.

Analyze the theoretical distribution value of hot spot dot matrix and the hot spot dot matrix output gray level value of charge coupled device 3 samplings, realize demarcation charge coupled device 3 response linearities.

Claims (2)

1, a kind of scaling method of electric charge coupler response linearity is characterized in that comprising the following steps:

Make slit diffraction screen (1), select the diffraction screen parameter, make the target surface of the primary maximum width of diffraction and charge coupled device to be measured (3) measure-alike;

After fourier transform lens (2) placed diffraction screen, and charge coupled device to be measured (3) is placed the back focal plane position of fourier transform lens (2);

Utilize a branch of monochromatic planar light irradiation diffraction screen (1), carry out the sampling of charge coupled device to be measured (3) output gray level value, obtain diffraction pattern output gray level value;

Calculate spot intensity theoretical distribution value, and with the hot spot output gray level value of charge coupled device to be measured (3) sampling relatively, realize demarcation to charge coupled device to be measured (3) response linearity.

2, the scaling method of electric charge coupler response linearity according to claim 1 is characterized in that:

Described diffraction screen (1) can be made double slit (single seam, many seams, square hole or circular hole) diffraction screen;

The described sampling of carrying out charge coupled device to be measured (3) output gray level value, can obtain a series of dot matrix hot spot output gray level value.

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