JPS604424B2 - Photoelectric conversion element with spatial filter function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photoelectric conversion element having a spatial filter function conventionally achieved using stationary, translational and rotating reticles.

The configuration of the spatial filter based on the conventionally known principle is
This will be explained with reference to the figures.

In FIG. 1a, a subject 31 is captured at an image plane 3 by an objective lens 32.
The image is focused on 3. A reticle plate 34 having a transparent part and an opaque part is disposed on the image plane 33. The light transmitted through the reticle plate is focused by a condenser lens 35 and collected on a photoelectric conversion element 36, and a current proportional to the light is obtained. As a reticle plate used for one-dimensional space filtering, there is a shelf-shaped reticle plate as shown in FIG. 1b.

The transmission ratio of the shelf-shaped reticle plate in the x direction is as shown in FIG. 1c. If such a tickle plate is fixed on the image plane, when the subject moves in the X direction at an angular velocity Qx as shown in Figure 1a, the light intensity distribution in the X direction of the subject will depend on its spatial frequency and angular velocity Qx. It is output from the photoelectric conversion element as a series of strength and weakness signals. This can be understood as a convolution integral of the illuminance distribution of the object on the image plane, which changes over time, and the transmittance distribution of the reticle plate. As is well known, the spatial filter using the shelf-shaped reticle plate of FIG. 1b, which is stationary, has a one-dimensional narrow band pass characteristic. Since a direct current component of a spatial frequency passes through a transmission type reticle plate as shown in FIG. 1c, it is desirable to use a polar reticle that can provide an output as shown in FIG. 1d.
Further, the translational reticle method in which the reticle plate is moved in the x direction as shown in FIG. 1b is known to be effective because it can provide spatial filtering even to a stationary subject. Therefore, it is desirable that the spatial distribution of the transmission ratio can change with time as a function of the reticle. In order to obtain polarity in the output with the conventional device shown in FIG. 1a, it is necessary to divide the optical path in some way. Furthermore, since the use of a moving reticle plate requires a mechanical feeding device or the like, there is a problem in that the device becomes complicated and large. The purpose of the present invention is to provide a photoelectric conversion element that can operate in the same manner as a conventional movable reticle without mechanically moving the reticle, and has a spatial filter function that can be operated in the same manner as a polarized reticle by following the reticle. It is about providing.

The photoelectric conversion element having a spatial filter function according to the present invention includes the reticle plate 4, the capacitor 35, and the capacitor 35 shown in FIG.
The photoelectric conversion element 36 can be configured as an integrated functional element, and is not limited to a one-dimensional spatial filter function, but can perform any pattern of spatial filter functions.

Changes in the arrayed reticle pattern can be electrically controlled. Furthermore, since it can be integrated into an integrated circuit, it is possible to make the entire device smaller. Applications of one-dimensional spatial filters include speedometers and optical focus alignment.

Spatial filtering is generally used for the purpose of improving the S/N of the output of the tracking system and depicting error signals, but its application is limited due to the complexity of the device. With elements such as those shown in the present invention, the spatial filter can be more broadly extended to the remote speedometer side,
It is thought that it will be possible to use it for movement detection and pattern recognition. This is because, for example, when used as a sensor for pattern recognition preprocessing, at all frequencies outside the spatial filter,
The spatial frequency of an object must be analyzed adaptively and using a large number of elements.The photoelectric element having a spatial filter function according to the present invention can be applied very effectively to such applications. First, the explanation will be given with reference to FIG.

In FIG. 2, the photoelectric cells (1-a, 1-b, 1-c, . . . ) are portions that accumulate charges proportional to the irradiated light, and are spatially arranged in a pattern that suits the purpose. In the figure, 1-a,
They are arranged in one dimension in the order of 1-b and turtle-c. Each photocell has two signal output switches 2 (2-a
, 21b, 21c...) and 3 (3-a, 31b731c...) are provided. This readout switch is controlled by a switch control clock 4, and is controlled so that either both of the readout switches 2 and 3 are OFF, or only one is ON.This control is performed for each photoelectric cell. The charge of the photocell read out from each readout switch, which is wired so as to be changed, is added to an adder 5 (5-a).
g Horse-P) is added. Everything read from the readout switch 2 is added by the adder 5-a, and everything read from the readout switch 3 is added by the adder 5-b.Adder 5-a, The outputs of 5-b are respectively input to the differential amplifier 6, and the difference between the two adders is output from the differential amplifier 6. First, it is assumed that all the output switches are turned off by the switch control clock W. Due to the object image irradiated onto the photoelectric cell at the time, a charge proportional to the light intensity is accumulated in each photoelectric cell.Next, the switch control clock 4 is activated to turn on one of the photoelectric cells. 'When rubbed, the charges of each photocell flow into the adder through the output switch of the OM side, where they are added together ~ Furthermore, the difference between the two adders is output from the differential amplifier.As shown in the figure. Street,
Since the adder 5-a is connected to the positive phase side of the duty amplifier 6 and the adder 51b is connected to the reverse side, the transmittance of the photocell with the readout switch 2 on is 11, and the readout switch 3 is on the transmittance of 11. O
A photoelectric cell of N is equivalent to placing a sacrificial reticle with a transmittance of -1. The reticle pattern can be freely controlled by a switch control clock. This method allows for a configuration in which the spatial filter element according to the present invention is configured in a 3D manner by charge coupling.The configuration of the spatial filter element according to the present invention will be explained in more detail with reference to FIG.

FIG. 3 is an explanatory diagram of an embodiment for realizing a one-dimensional spatial filter using the shelf-like translational reticle shown in FIG. Fig. 4 shows a pulse waveform for driving the element having the configuration shown in Fig. 3. Fig. 5 is a graph also showing the pattern of spatial filtering. Fig. 3a shows the configuration of the present invention. This is a cross-sectional view of a device that realizes the function of an optical turtle cell and a signal output switch using a charge coupling method.
A thin film insulating layer is provided on the semiconductor substrate 1, and a plurality of independent metal electrodes are provided on the insulating layer 2, so that charge is accumulated under one electrode and transferred under the adjacent electrode. So-called charge-coupled devices (Cha
Depending on the basic structure and principle of the r saddle coupled device, the storage metal electrode 13 and the transfer metal electrode 14,
is provided. Further, under the transfer electrode, a floating diffusion layer 6 and a layer 7 having a conductivity type different from that of the substrate are provided in a location that does not interfere with the adjacent storage metal electrode. In the figure, the broken line indicates the surface potential of the bath where a potential well was created under the storage metal electrode. Assuming that the semiconductor substrate 11 is a P-type semiconductor, the storage metal electrode is biased to a positive potential with respect to the substrate. When the transfer electrodes 14 and 15 are in a pinch-off state as shown by the broken line 18, a potential well is formed directly below the storage metal electrode 13, creating a photoelectric conversion photocell. When a deep positive potential bias is applied to either of the transfer electrodes 14, 15, the charges directly under the storage metal electrode flow into either of the floating diffusion layers 16, 17 which have been biased in advance. FIG. 3b shows a schematic diagram of the device.

The storage metal electrode 13 and the transfer metal electrodes 14 and 15 shown in FIG. 3a are arranged one-dimensionally as shown. The floating diffusion layers 16 and 17 are connected in common,
Charges read out from each cell are added together and read out using a reverse bias method. In other words, the floating diffusion layers 16 and 17 are also connected to each reset switch 19 and 20, and when each photocell is in an accumulation state, the reset switch is turned on and biased to a sufficiently high voltage VR. is turned off, the floating diffusion layer is kept in a bias state close to VR.In this state, the transfer electrodes 14 and 15
When either of them is turned on, the charges accumulated in the photocrab cell pass under the transfer electrode and flow into the floating diffusion layer, lowering its floating potential. The potential change of the floating diffusion layer is MOSF
It is read out by a source follower amplifier consisting of ETs 21, 22 and source resistors 23, 24. The outputs of the two amplifiers are led to a differential amplifier 25, where only the t difference signal is amplified. In order for the photocells arranged in one dimension B to operate as a shelf-like translational reticle, the transfer electrodes 4 and 16 are connected to six-phase drive as shown in the figure. Six-phase applied drive pulses &, -f6 are shown in FIG.

FIG. 4 also shows the reset pulse R for the reset switch. ◇s is a storage pulse applied to the storage electrode 13. In Fig. 3, waste wiring at s is omitted, but all storage electrodes are kept at the same potential. In Fig. 4, time t,
At , the storage electrode is on and all transfer electrodes are off. (2) After R is turned on and the floating diffusion layer is reset biased, it is in a floating expansion state again. At time t2, only 5 and 6 are turned on, resulting in 14-a9 85
1b, 151cwo Turtle 51G, Kan4-e, Turtle41t... are turned on, and Turtle 31a, 131e, 13-f...
The charges of the photocell are in the floating diffusion layer 16, 13-b, 13
-c, 13-d... photocell charges are floating diffusion layer 1
7. FIG. 5 shows the operating state in a vague diagram. In FIG. 5, the white part shows the state read out to the floating diffusion layer 16, and the shaded part shows the state read out to the floating diffusion layer 17. The operations at times t3, t4, and t5 in FIG. 4 are as shown in FIG. It is clear that the output of the differential amplifier 15 in FIG. 3 corresponds to the output of the sacrificial translation space filter in FIG. 5, where the white area is 11 and the shaded area is -1. In the photoelectric conversion element according to the present invention, a spatial filter can be constructed simply by forming an optical image on a semiconductor substrate, so it is obvious that the structure can be simplified and miniaturized.

Since there are no restrictions in principle on how to arrange the photoelectric cells or change the pattern of the time series, it is possible to perform spatial filtering using a moving reticle, which was completely impossible with conventional methods. Needless to say, circular arrays and two-dimensional grid arrays are possible. The present invention is applicable not only to charge coupling but also to charge transfer devices in general.
It can also be realized using the principle of It goes without saying that various device structures and signal readout methods of charge-coupled devices can be applied to the charge-coupled device structure shown in the embodiment.

[Brief explanation of the drawing]

Figure 1a is a schematic diagram for explaining a conventional -dimensional spatial filter. Figure 1b is an enlarged view of a shelf-shaped reticle, and Figure 1 shows the transmission ratio of a transmission type reticle plate. Graph 1d is a graph showing the transmission ratio of a shelf-like reticle. FIG. 2 is a principle diagram showing the configuration of a photoelectric conversion element having a spatial filter function according to the present invention. A sectional view, FIG. 3b is a schematic diagram showing the overall configuration, FIG. 4 is a time chart of driving pulses, and FIG. 5 is an explanatory diagram showing the operation pattern as a suitable reticle.
32...Objective lens, 33...Imaging plane "34
... Reticle plate, 35 ... Condenser lens, 36 ... Photoelectric conversion element, 1 (1-a, Kanichi b, Kiichi c ...) ... Photoelectric cell, 2 (21a,
21b, 2-c...")...The first readout switch of the photoelectric cell "3(31a, 31b, 3-c...)...
・...Second logic switch t of the light exposure cell 4...Switch control clock generation circuit, 5 (5-a, 5-b)・
...Adder, 6...Differential amplifier, 11...
...Semiconductor substrate, 12...Thin film insulating plate, 14,
15... Metal electrode for transfer, 16, 17...
...Floating diffusion layer, 18...Dotted line indicating semiconductor surface potential, 19, 20...Reset switch, 21, 22
...MOSFET, 23, 24... Source resistance, 1
5...Differential amplifier. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. A plurality of spatially arranged photoelectric conversion cells; every other cell region among a plurality of cell regions adjacent to each other and consisting of at least one cell along a predetermined direction; a control circuit that reads signals from the cell and changes the plurality of cell areas over time to move the readout cell area along the predetermined direction over time; an addition that adds the read signals; A photoelectric conversion element having a spatial filter function, characterized by comprising a circuit. 2. A photoelectric conversion element having a spatial filter function according to claim 1, wherein the photoelectric conversion cell is a charge coupled device.