JPS5919371A - Brightness detecting system by storage type photosensor - Google Patents

Abstract

PURPOSE:To readily detect the time mean brightness by reading out the output of a storage type photosensor applied to the structure of a static induction transistor in the storage of optical information by using the photosensor and calculating the time differentiation. CONSTITUTION:Storage type photosensors PT1-PT7 which can nondestructively read out and applies the structure of a static induction transistor formed sequentially with an N<-> type layer, a P type layer and an N<+> type layer are arranged linearly on an N<+> type silicon substrate. When a drive circuit DV is in low level state, optical information stored in the photosensors PT1-PT7 are cleared, and when a switch SW1 is closed, the storage is started. When sample pulses for differentiation is produced at times tA, tB, output signals are held through sample-holding circuits SA2, SB2, SA4, SB4, thereby obtaining information of mean brightness between the times tA and tB.

Description

[Detailed Description of the Invention] The present invention utilizes the structure of a SIT (static induction transistor) to output accumulated light input from a photosensor, etc., and output it in real time, non-destructively, as an integrated signal. In the storage-type 7-photo sensor, when the accumulation of optical information starts, the output of one or n photosensors is read out, and the time differential of the read l~ signal is calculated. This relates to a method that detects the brightness on a surface and also determines the storage time.

Conventionally, the method of detecting the brightness on the sensor surface and L7 are as follows.
Non-storage type photodiodes are used, but the output from these sensors changes from moment to moment, so
In order to detect time-averaged brightness, integration over a certain period of time is required, making the circuit complex.

The present invention provides a method for detecting brightness based on the output of an accumulation type photosensor, which does not require any complicated circuit configuration.

The present invention will be specifically explained below using the drawings.

FIG. 1(a) is a schematic diagram of the structure of the SIT photosensor, which consists of an n layer on a silicon substrate with an n soil layer.

A p layer and an n soil layer are formed as shown in the figure.

Light incident on the n-layer, which is the photosensitive surface, creates pairs of holes and electrons, and the holes are accumulated in the p-layer. The holes accumulated in the p-layer are proportional to the intensity of incident light and form the total potential of the base of the phototransistor. Based on this pace potential, a photoelectric conversion output signal is obtained via the load resistor RL.

DV is a drive circuit for the SIT photosensor, and when the output of DV is at a high level, optical information is stored and read out, and when the output of DV is at a low level, the holes that were generated in the p layer are is riff Vtsu7yu (cleared). That is, when the DV is at a high level, image information can be read out non-destructively even if the device is destroyed.

Figure 1(b) shows an equivalent circuit for driving the SIT photosensor in Figure 1 (hot), and the FT has a SIT structure.
It is an auto sensor.

Figure 2 shows storage type photosensors of the present invention capable of non-destructive readout arranged in a line, detecting the brightness of the sensor and determining the storage time based on the detected brightness. This is an example of an electric circuit. PTI-FT7 is S
The IT-structured photo sensor, AGI-AG7, is a switching gate for signal readout, and a decoder driver D.
Controlled by OD. ONT is a counter for DOD control, and OKT is a pulse control circuit. BO2, BO2 are gates for detecting the output of the photosensor, RL, R, L2
．． RL4 is the load resistance for signal readout, IN is the inverter %SA2°8A4. SB2 and 8B4 are sample and hold circuits, R80 to R88 are operational resistors, OPt to OP3 are operational amplifiers, MTI and MT2 are indicators for displaying information on detected brightness, and 0. . is an integrating capacitor for determining the accumulation time, and AG is 0. . OMP is a comparator, RF is a reference voltage, AN is an AND gate, POK is a signal processing circuit, SWI is a reset gate that resets the integrated charge of
teeth.

This is a switch that controls the start of the circuit. FIG. 3 is a timing chart of the main part of FIG. 2, and the operation of FIG. 2 will be explained in detail based on this. At time t1°, φl is at a low level and the 8IT drive circuit DV is also inverted to a low level, so unnecessary light (image) information stored in advance in the photosensors PTI to PT7 of the 8IT structure is cleared. At the same time, the counter CNT is also reset. Time tl
When the switch sw1 is turned on at l, φ1 is inverted to high level and DV is also inverted to high level, so the photo sensor FT
Accumulation of optical information is started at , but since the output of the comparator CPM is at a low level, the analog/game) AN cannot count the reference clock pulse φ2. In this state, all of the output terminals C6-C1 of the counter CNT are at a low level, and only the AO terminal of the decoder driver DCD is at a high level, so that the analog goots 01 to G7 are all turned off. On the other hand, since the output of inverter IN is at a high level,
Game) BO2, BO2 is turned on, and the photo sensor PT2. The output of PT4° is always connected to the load resistance RL2. R.L.
4. When a sample pulse for time differentiation of the signal is generated at times IA, , 4n., the sample and hold circuits SA2. SB2. SM4. The output signal at each time is held via SB4, and resistors R80 to
A differential amplifier circuit consisting of R87 operational amplifiers OPI and OF2 subtracts the signal held at time from the signal held at time tB, and the average brightness between time tA and tB is output from OPI and OF2. information is obtained and displayed on the displays MTI and MT2.

Next, time t is used to control the accumulation time of the 7th sensor.
When G4 is inverted in synchronization with the fall of the sample and hold pulse generated at B, and the reset gate AG is turned off, OPI
, OF2 starts second-time integration for determining the accumulation time. Time t8. When the output of OF2 exceeds the reference voltage RF, the output of the comparator CMP becomes high.) The reference clock pulse yi2 enters the counter CNT via AN, and the analog gates AG1 to AG7 are turned on in sequence by the decoder driver DCD, and the photo sensor PT
The outputs of I to PT7 are read out in time series via load RL and signal processed by PCK. If the output level of the DV is set to an appropriate constant voltage level based on the inversion of the comparator CMP for determining the accumulation time, it is also possible to stop further accumulation of optical information during the start-up of image information. Also O
Operational resistor 188, R8 that calculates the output of PI and OF2
By appropriately changing and setting the value of 9, the output of the photosensor for brightness detection can be weighted to determine the accumulation time. Figure 4 shows another embodiment of the present invention. In one of the methods, a method is proposed in which the photosensor for detecting p1 brightness can be arbitrarily set by setting the set lever BS of the photosensor selection means MST.

ORGATE ORO~OR2, Antogame) ANQ~^
N2 is a gate for selecting a photosensor for brightness detection set in the photosensor selection means MST, D1 to D7 are light emitting display elements for displaying the selected photosensor, and R1 to R7 are gates for selecting a photosensor for brightness detection set in the photosensor selection means MST. It is a current limiting resistor.

For example, set lever B of a photosensor for brightness detection.
When S is set to ■ as shown in the figure, the decoder driver DC
At the same time that the terminal of the DOM4 becomes high level and the light emitting element D4 emits light, the analog game AG4 is turned on and the output of the photosensor PT4 is constantly outputted.

The specific operation of this electric circuit is the same as that in FIG. 2, so it will be omitted.

In addition to the SIT used in the above embodiment, the SIT sensor is FIRSiaD1, which has various modifications.
Examples include, but are not limited to, those described in RD-22P185, 975, Technical Report 1iD590, R50, August 28, 1980, Technical Report of the Television Society of Japan.

As described above, by using the present invention, it is possible to read out the output of a storage type photosensor during optical information storage, which can be read out non-destructively.
By calculating the time derivative of the readout signal, we can see the remarkable feature that not only detects the brightness but also determines the accumulation time.

[Brief explanation of the drawing]

Fig. 1 (,) is a sectional view of the SIT sensor element applied to the present invention, Fig. 1 (bl is Fig. 1 (-1) is an equivalent circuit diagram of Takako, Fig. 2 is a detection circuit according to the present invention - example diagram) Figure 3 is the second
Operation waveform diagram of the illustrated circuit FIG. 4 is an electric circuit diagram of another modification of the second illustrated circuit PTI~
FT7; SIT sensor AGI to AG7; heave opening gate SA2. SA4. SB2. SB4; Sample and hold circuit OFI to OP3; Operational amplifier circuit Cl01 Integrating capacitor Patent applicant: Canon Co., Ltd. Procedural amendment (spontaneous) December 21, 1980" 1 ■ 1980 Patent Application No. 128549 2, Invention Brightness detection method 3 using a name storage type photosensor, relationship with the case of the person making the correction Patent applicant address 3-30-2 Shimomaruko, Ota-ku, Tokyo Name (+01
1) Canon Co., Ltd. Representative: Ryu Kaku, Department 4, Agent address: 3-30-25 Shimomaruko, Ota-ku, Tokyo 148, Figures 2 and 4 of the drawings to be amended, Figure 4, 6, Contents of the amendment, Figure 2 , Figure 4 is corrected as shown in the attached sheet.

Claims (1)

[Claims] (11) In an accumulation type photosensor in which the output from accumulated optical input is output in real time as a non-destructively integrated signal, only one fcI' is output during accumulation of optical information. i
A brightness detection method for an accumulation type photosensor, characterized in that the brightness on the surface of the photosensor is detected by reading out the outputs of the n photosensors and calculating the time differential of the readout signal. (2) A brightness detection method for an accumulation type photosensor according to claim (1), wherein the accumulation time is determined based on the brightness calculated by the time differentiation.