JPS6143641B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a device that photoelectrically extracts specific component information from spatial frequency components of an optical image.
As a method for extracting a specific spatial frequency component, there is a method of mechanically vibrating a light-dark grating installed in front of a photoelectric element, or a method of propagating surface acoustic waves on a CdS light receiving surface, which changes the conductivity of CdS from place to place over time. A method is already known in which an alternating current signal is obtained in accordance with the magnitude of the spatial frequency component. However, the former method has the disadvantage that the device becomes large due to the presence of mechanically moving parts, and power consumption also increases.
Since the degree of change in conductivity of CdS is small, it has the disadvantage of a poor signal-to-noise ratio. Furthermore, determining a specific spatial frequency component in an optical image corresponds to determining a Fourier component, and this Fourier transform calculation procedure itself is well known. However, since the Fourier transform operation is a complex number operation, a computer or the like must be used, and even then, there is a problem in that the processing takes time. Therefore, an object of the present invention is to provide a device that extracts a specific frequency component from among the spatial frequency components of an optical image with high precision and in real time using a relatively simple configuration without using mechanically movable parts. . In order to achieve this object, the first invention of the present application is an apparatus for extracting specific frequency component information from the spatial frequency components of an optical image. The output of each element is made to depend on the intensity of light incident thereon at or near the focal point of the system, and the photoelectric elements are divided into a plurality of element groups each consisting of a plurality of elements. The spatial lengths are made equal to each other, and there is a phase difference of one period between the output of the photoelectric element of each element group and the output of the photoelectric element of the next group located at a position corresponding to the photoelectric element. The output of the photoelectric element of each element group is modulated into a sinusoidal AC signal having a phase difference depending on the position of the photoelectric element, an amplitude corresponding to the output of the photoelectric element, and an equal angular frequency so that The invention is characterized by providing a modulation means and an addition means for adding the alternating current signals, and the second invention is an apparatus for extracting specific frequency component information from spatial frequency components of an optical image, etc. A photoelectric element array consisting of a plurality of photoelectric elements arranged in a row at intervals is provided at or near the focal point of the optical system, the output of each element is made dependent on the intensity of light incident thereon, and the photoelectric elements are Divide into a plurality of element groups consisting of a plurality of elements, and make the spatial length of each element group equal to each other,
Then, the number N of photoelectric elements in each element group is made equal, the output of the photoelectric element located at the beginning of each group is added, the output of the photoelectric element located next is added, and so on. Add the output of the photoelectric element at the position,
Modulating means modulates these summed outputs into alternating current signals having equal angular frequencies, whose phases are sequentially shifted by 1/N period in the order in which the photoelectric elements are arranged, and whose amplitudes correspond to the magnitudes of the summed outputs. and adding means for adding the alternating current signals, and the third invention is an apparatus for extracting specific frequency component information from spatial frequency components of an optical image, A photoelectric element array consisting of a plurality of photoelectric elements is provided at or near the focal point of the optical system, and the output of each element is made dependent on the intensity of light incident thereon. The spatial length of each element group is made equal to each other, and the output of the photoelectric element in each element group and the photoelectric element in the next group located at a position corresponding to the photoelectric element in each element group are divided into The output of the photoelectric element of each element group is set at an angle that is equal to the phase difference depending on the position of the photoelectric element and the amplitude depending on the output of the photoelectric element so that a phase difference of one period is generated between the output of the photoelectric element and the output of the photoelectric element. The apparatus is characterized by comprising a modulating means for modulating an alternating current signal having a frequency, an adding means for adding the alternating current signal, and a phase comparing means for comparing the phase of the output of the adding means with comparative phase information. It is. The output of the adding means is an alternating current output at the angular frequency, the amplitude of which is related to the magnitude of the specific spatial frequency component, and the phase of which is related to the relative position of the specific spatial frequency component and the photoelectric element array. . In this way, both of the present invention extract specific spatial frequency components by modulating the output of the photoelectric element with a predetermined alternating current signal and adding these signals, so this extraction can be performed in real time, and the configurations are also comparable. It will be simple. In particular, regardless of whether the optical image is moving or stationary on the photoelectric element array, the relative positional relationship between the optical image and the photoelectric element array can be obtained from the phase information of the AC output, so it is very easy to handle. becomes. Next, the present invention will be explained in principle using FIG. Photoelectric elements 1a to 1 arranged in a row at equal intervals
The photoelectric element array 10 consisting of d, 2a to 2d, and 3a to 3d is arranged at or near the focal plane of an optical system (not shown). In addition, the element array is
It is divided into element groups consisting of equal numbers of elements 1a to 1d, 2d to 2d, and 3a to 3d. Element 1 arranged first in each element group
a, 2a, 3a, the next elements 1b, 2b,
3b, and the next elements 1c, 2c, 3c,
The last elements 1d, 2d, and 3d are connected to each other at connection points 11a, 11b, 11c, and 11d, respectively, and connected to the modulation means 12. On this element array 10, an optical image containing various spatial frequency components is formed by the optical system, and each photoelectric element generates an output having a DC component related to the intensity of the light incident thereon. The modulation means 12 converts the output signals of the elements at the connection points 11a, 11b, 11c, and 11d into alternating current signals having a phase advanced or delayed by 1/4 period, respectively, and an amplitude related to the magnitude of the output signal. modulates to. Therefore, the outputs of photoelectric elements such as 1a, 2a, and 3a, located at positions corresponding to the arrangement order of each element group, are modulated into alternating current signals having the same phase, and the modulated alternating current signals of the elements of each group are modulated by the elements. The phase will be shifted by 1/4 period in the order of arrangement. This 1/4 period phase shift is because each element group is composed of 4 elements, and generally when it is composed of N elements, the 1/4 period phase shift is due to the fact that each element group is composed of 4 elements. This will result in a misalignment. thus,
The alternating current output of the photoelectric element after modulation has an amplitude related to the light intensity and a specific phase difference as described above with respect to other elements. Adding means 1 adds the modulated output of each element.
4, when added, the output of this adding means is the reciprocal of the spatial length dmm of each element group, that is, 1/d pieces/mm.
This includes an extremely large amount of spatial frequency component information. Next, the principle of the present invention described above for extracting a specific spatial frequency component of 1/d lines/mm from an optical image consisting of a large number of spatial frequency components will be explained using a mathematical formula for the case of sinusoidal modulation. Explain in detail. In the above example, for simplicity, the number of groups is 3 and the number of elements in each group is 4, but in the following explanation, for generalization, the number of groups is M, and the number of elements in each group is Let be N.
When an optical image with a certain luminance distribution is projected onto these M×N elements, the output of each element proportional to the luminance is ^m _o (n=1, 2...N, m=1, 2 …
M). Note that this ^m _o is, for example, n=1, m=
This means that the output ¹ ₁ when n=2 and m=3 represents the output of the element 1a in FIG. 1, and the output ³ ₂ when n=2 and m=3 represents the output of the element 3b. The output ^m _o of the nth element of each group is modulated by the modulation means,

[Formula] When modulated with an AC signal, the The output after modulation is

[Formula] becomes. Here, i is an imaginary unit and w is an angular frequency. Therefore, the output I of the adding means is the sum of the outputs of all the elements after modulation.
teeth

[Formula] becomes. this

[Formula] is the spatial frequency component itself of 1/d lines/mm. Therefore, it can be seen that the amplitude of the AC output I of the adding means 14 is proportional to the magnitude of the spatial frequency component of 1/d lines/mm. As described above, according to the present invention, by determining the spatial length d of the element groups , , of the element array 10, a desired spatial frequency component in the optical image can be photoelectrically extracted. As is already known, for example, the focusing state of the imaging optical system can be detected using the information on the magnitude of the spatial frequency component extracted in this way. In other words, in a general optical system, the high-order spatial frequency components in the optical image are large when in focus, but as the optical system deviates from the focused state, the high-order components rapidly decrease. The in-focus state of the optical system can be detected by extracting the magnitude information of high-order spatial frequency components and detecting the maximum value. In the above description, it has been stated that the amplitude information of the AC component output from the adding means 14 is related to the magnitude of the desired spatial frequency component. By using this, it is possible to detect the displacement of the optical image, that is, the movement of the optical image. To explain this in detail, when the optical image on the array is displaced by one photoelectric element to the left in FIG. 1, the output I' of the adding means 14 is becomes. Here, the first term in { } is equal to the output I before the image displacement, and the second term represents the influence of the part of the image that entered the element array and the part that protruded from the element array due to the displacement of the image. There is. However, since this second term can be ignored compared to the first term in a general optical image, the difference between I and I' is due to the existence of e-2π/Ni. That is, this shows that when the image is laterally shifted by exactly the width of one element, the phase of the output of the adding means changes by 2π/N. Furthermore, the DC component of the output of the adding means represents the average brightness of the optical image. In FIG. 1, elements at corresponding positions in each element group, that is, elements 1a, 2a, 3a, 1b, 2b, 3b, whose outputs are modulated into alternating current signals having the same phase, are shown.
Since they are connected to each other and the connection point is connected to the modulation means 12, the lead wire from the element array is determined by the number of elements in the group, not by the number of element groups. Of course, the present invention is not limited to such a configuration, and each photoelectric element may be individually connected to the modulation means 12. Furthermore, in the above example, the number of elements constituting each element group, , is all equal, but this is not essential to the present invention, and the number of elements constituting the element group is set to N.
In this case, the number of constituent elements in each element group may be different as long as the condition that the element output is sequentially modulated into an alternating current signal having a phase difference of 1/N period is satisfied. Next, a first embodiment of the present invention will be explained with reference to FIG. In the first embodiment, a photoconductive element such as CdS that produces an output current proportional to the applied voltage and the light intensity is used as a photoelectric element, and by using an alternating current voltage as the applied voltage, the output of the photoelectric element is related to the light intensity. This is an example of modulating current. In FIG. 2, the sinusoidal AC voltage supply circuit 16 has four output terminals 16a, 16b, 16c, and 16d as shown in FIG.
Equal angular frequency W ₀ as shown in b, c, d, respectively
, but generates a sine wave voltage whose phase is sequentially delayed by 2π/4. The output terminal 16a is connected to one terminal of the first photoconductive element 1a, 2a, 3a of each group of the element array 10 arranged in the same manner as in FIG. 1, and the other output terminals 16b, 16c, 16d are also connected. Similarly, photoconductive elements 1 corresponding to each group in the order of arrangement
b, 2b, 3b, 1c, 2c, 3c, 1d, 2
d and 3d, respectively. As a result, the output current of each photoconductive element becomes proportional to the intensity of light incident thereon and the applied alternating current voltage. That is,
This means that the output current of each element, which is proportional to the light intensity, is modulated by the applied AC voltage. The output terminal 16a
The terminals of the photoconductive elements not connected to ~16d are all connected together by conductive wires 17, and the current-voltage conversion circuit 1 consisting of an operational amplifier
8 is connected. Therefore, the output currents of each photoconductive element are all added together and input to the conversion circuit 18. As shown in Fig. 4a, this added output current has an angular frequency of W ₀ and 1/d line/of the optical image.
Contains information on spatial frequency components of mm. This added output current is converted into a voltage by the conversion circuit 18, and the _fourth
Extract the AC component shown in Figure b. The amplitude of this alternating current is proportional to the magnitude of the desired spatial frequency component of 1/d line/mm. If the output of the filter 20 is rectified and amplified by the circuit 22, a DC output proportional to the magnitude of the desired spatial frequency component can be obtained. Further, the phase difference between the output of the bandpass filter 20 and the output from any one of the four output terminals (16d in FIG. 2) of the sine wave voltage supply circuit 16 is measured by the phase difference measurement circuit 24. When obtained, phase information about the desired spatial frequency component is obtained, and the displacement of the optical image can be detected from this.
Furthermore, the output of the conversion circuit 18 is passed through a low pass filter 2.
6, information regarding the average light amount of the light image shown in FIG. 4c can be obtained. Comparing the components of this first embodiment with those shown in FIG. 17 corresponds to the addition means 14. Next, a specific structural example of such a photoconductive element array is shown in FIG. In FIG. 5a, there is a transparent substrate 30 that serves as a light-receiving surface, and In ₂ O ₃ or SnO ₂ on it.
A transparent common electrode 32 such as, and a CdS 34 thereon,
An element array is constituted by a plurality of In electrode pieces 36 lined up thereon, and lead wires connected to the common electrode and each electrode piece, respectively. Furthermore, Figure 5b
is a plan view. This structure is preferable because the distance between the mutually insulated electrode pieces 36 can be made extremely narrow, and therefore the number of photoelectric elements constituting the element group can be increased. Next, a second embodiment of the present invention will be described with reference to FIG. The photoelectric elements of the element array used in this embodiment may be of any type as long as they convert light intensity into electrical signals approximately proportional to it. Therefore, a photoconductive element such as CdS, a photovoltaic element such as a silicon photovoltaic cell, a photodiode, etc. can be used. In FIG. 6, a constant voltage +V is applied to each photoelectric element of the element array 10, so that each photoelectric element outputs a direct current approximately proportional to only the light intensity. Corresponding elements 1a, 2 of each group
The output terminals of a and 3a are both connected to the output terminal 10a of the array 10, so the outputs of these three elements are summed. Similarly, corresponding element 1
b, 2b, 3b, 1c, 2c, 3c and 1d, 2
d and 3d are also output terminals 10b, 10c, and 10d, respectively.
and each output is summed there. In this way, the four summed output currents obtained by adding the three outputs, respectively, are generated by the current-voltage conversion circuits 40a, 40b, 40c,
It is converted into a DC voltage at 40d. This DC voltage is shown in FIGS. 7a, b, c, and d. That is, FIG. 7a,
DC voltages b, c, and d are applied to photoelectric elements 1a and 2, respectively.
It has a value proportional to the sum of the light intensities of a and 3a, the sum of the light intensities of 1b, 2b, and 3b, the sum of the light intensities of 1c, 2c, and 3c, and the sum of the light intensities of 1d, 2d, and 3d. The modulation circuit 42 is shown in FIG. 7 a, b, c, d.
The DC voltage is modulated into the AC voltages shown in FIGS. 8a, b, c, and d, respectively. These alternating current voltages both have the same angular frequency W ₀ , but their amplitudes are each proportional to the direct current voltage in Figure 7, and their phases are
It is delayed by 90 degrees. Addition circuit 44 is modulation circuit 4
Adding the four outputs of 2, the angular frequency shown in Figure 9 is obtained.
Generates an AC output of W ₀ . The amplitude of this AC output is proportional to the magnitude of the spatial frequency component of 1/d lines/mm, and corresponds to the output of the first embodiment shown in FIG. 4a. Thereafter, the output of this adder circuit 44 is passed through a band pass filter 20, a rectifier 22, a phase difference measuring device 24, and a low pass filter 26, as in the first embodiment, thereby obtaining desired information. FIG. 10 shows a specific example of the modulation circuit 42.
The sine wave voltage supply circuit 42S is the same as the voltage supply circuit 16 shown in FIG. 2, and its four output terminals each have an angle whose phase is delayed by 2π/4 as shown in FIG. 3 a, b, c, and d. Generates an alternating voltage with frequency W ₀ . Multipliers 42a, 42b, 42c, and 42d multiply the output voltages of current-voltage conversion circuits 40a, 40b, 40c, and 40d, respectively, by the sequentially delayed output voltages of 2π/4 from voltage source 42S. In the present invention, the element group is composed of a finite number of N elements, that is, the length d of the element group is quantized into N elements, so the spatial frequency component of the image is 1/d elements/mm. decreases in magnitude. The degree of this decrease is (sinπ/N)/π/N. In this example, N = 4 to avoid complicating the drawing, but if N = 8, then (sinπ/8)/π/8 = 0.974, which is 1, which is the value when N is infinite. So close that the above-mentioned reduction becomes almost negligible. In this way, by dividing the width d of the desired spatial period, that is, the width d of the element group, by a relatively small number, for example, eight photoelectric elements, the magnitude of the spatial frequency component of the image, that is, the amplitude information, is extracted with sufficient precision. can. Although amplitude information has been discussed above, phase information can also be extracted with sufficient accuracy, ie, with an accuracy several times 2π/N, simply by dividing d by a small number of N photoelectric elements. In addition, in the above explanation, a specific 1/d book/
In order to extract only the spatial frequency component of mm, the photoelectric element output was modulated with a sine wave signal. However, it is possible to modulate the output of the photoelectric element with a sine wave signal. Modulation may also be performed. In this case, a signal containing relatively many spatial frequency components of 1/d lines/mm can be extracted. Of course, if a bandpass filter that passes only the fundamental frequency component of the arbitrary periodic signal is connected to the output of the adding means 14, a signal containing an extremely large number of spatial frequency components of 1/d lines/mm can be extracted. However, when the modulation signal is a rectangular wave, the alternating current signal synthesized by the addition means has a stepwise shape, and in order to detect the phase with high precision, it is necessary to use an extremely narrow band bandpass filter. In general, narrowband bandpass filters have a problem in that the peak position tends to change depending on temperature, and this tends to cause a phase change between the input and output. On the other hand, when the modulation signal is sinusoidal, there is no particular need for a narrow band filter, and there is an advantage that a simple DC component removal filter or the like is sufficient. As is clear from the above, according to the present invention, by selecting the spatial length of the photoelectric element group, a specific component determined by the length is extracted from among the spatial frequency components of the optical image. Furthermore, since an electrical alternating current signal is used to modulate the element output, the signal-to-noise ratio can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the principle of the present invention, FIG. 2 is a block diagram showing a first embodiment of the invention, FIG. 3 is a graph showing each output voltage of a sinusoidal AC voltage supply circuit, and FIG. Figures a, b, and c are graphs representing a signal containing extracted spatial frequency components, an AC component separated from the signal, and a DC component of the signal, respectively;
5a and 5b are cross-sectional views and plan views showing specific structural examples of the element array used in this embodiment, FIG. 6 is a block diagram showing a second embodiment of the present invention, and FIG.
FIG. 8 is a graph showing the output of the photoelectric device of the example, FIG. 8 is a graph of the photoelectric device output after modulation, FIG. 9 is a diagram similar to FIG. 4a, and FIG. 10 is a graph of the modulation circuit of the second example. FIG. 2 is a block diagram showing a specific configuration example. In the figure, 1a to 1d, 2a to 2d, 3a to
3d; photoelectric element; ,; element group; 10; element array; 12; modulation means; 14; addition means.

Claims (1)

[Claims] 1. In an apparatus for extracting specific frequency component information from spatial frequency components of an optical image, a photoelectric element array consisting of a plurality of photoelectric elements arranged in a line is placed at or near the focal position of an optical system. In addition to making the output of each element dependent on the intensity of light incident thereon, the photoelectric elements are divided into multiple element groups each consisting of a plurality of elements, and the spatial length of each element group is made equal to each other. Each element group is arranged so that a phase difference of one period occurs between the output of the photoelectric element of each element group and the output of the photoelectric element of the next group located at a position corresponding to the photoelectric element. A modulation means is provided for modulating the output of the photoelectric element into a sinusoidal alternating current signal having a phase difference depending on the position of the photoelectric element, an amplitude corresponding to the output of the photoelectric element, and an angular frequency that is mutually equal. A spatial frequency component extraction device characterized by comprising an addition means for adding signals. 2. In a device for extracting specific frequency component information from the spatial frequency components of an optical image, a photoelectric element array consisting of a plurality of photoelectric elements arranged in a line at equal intervals is provided at or near the focal position of the optical system, and each Making the element output dependent on the intensity of light incident thereon, dividing the photoelectric elements into a plurality of element groups each consisting of a plurality of elements, and making the spatial lengths of each element group equal to each other, Then, the number N of photoelectric elements in each element group is made equal, the output of the photoelectric element located at the beginning of each group is added, the output of the photoelectric element located next is added, and so on. The outputs of the photoelectric elements at the positions are added, and these summed outputs have the same angular frequency, the phases are sequentially shifted by 1/N period in the order in which the photoelectric elements are arranged, and the amplitude is equal to the magnitude of the added output. 1. A spatial frequency component extracting device comprising: modulation means for modulating a corresponding alternating current signal; and addition means for adding the alternating current signals. 3. In a device that extracts specific frequency component information from the spatial frequency components of an optical image, a photoelectric element array consisting of a plurality of photoelectric elements arranged in a line is provided at or near the focal point of the optical system, and each element's output is directed there. At the same time, the photoelectric elements are divided into a plurality of element groups each consisting of a plurality of elements, and the spatial length of each element group is made equal to each other. The output of the photoelectric element of each element group is adjusted so that a phase difference of one period is generated between the output of the photoelectric element and the output of the photoelectric element of the next group located at a position corresponding to the photoelectric element. , providing modulation means for modulating into an alternating current signal having a phase difference corresponding to the position of the photoelectric element, an amplitude corresponding to the output of the photoelectric element, and an angular frequency that are mutually equal, and adding means for adding the alternating current signals, A spatial frequency component extracting device further comprising phase comparison means for comparing the phase of the output of the addition means with comparison phase information.