WO2002047377A1

WO2002047377A1 - Photosensor and photosensing method

Info

Publication number: WO2002047377A1
Application number: PCT/JP2001/010737
Authority: WO
Inventors: Seiichiro Mizuno
Original assignee: Hamamatsu Photonics K.K.
Priority date: 2000-12-07
Filing date: 2001-12-07
Publication date: 2002-06-13
Also published as: AU2002221085A1; JP2005101675A

Abstract

A photo sensor (1) comprises M units (1001 to 100M), an A/D conversion circuit (200), a timing detecting circuit (300), and a control circuit (400). Each unit (100m) has N photodiodes (PDm1 to PDmN), N switching elements (SWm1 to SWmN), charge voltage conversion circuit (110m), and a switching element (120m). If the charge produced in the photodiode (PDmn) and detected by the timing detecting circuit (300) is saturated, the control circuit (400) controls the switching of each switching element (SWmn) at the timing at which the charge accumulation in an integration capacitor of the charge voltage conversion circuit (110m) is stopped before the time when the saturated charge is accumulated in the integration capacitor. As a result, the influence of the blooming is suppressed and the intensity of the incident light can be accurately measured.

Description

Akitoda

Photodetector and photodetection method

Technical field

The present invention relates to an apparatus and a method for detecting the intensity of incident light. Background art

The light detection device includes one or more light detection elements, and a charge-voltage conversion circuit that outputs a voltage output according to the amount of charge output from the light detection elements. In this photodetector, the charge output from the photodetector in response to the incidence of light is accumulated in the charge-voltage conversion circuit, and a voltage output corresponding to the amount of the accumulated charge is output from the charge-voltage conversion circuit. Output, and an incident light intensity is obtained based on the output voltage output value. Such a photodetection device can be manufactured by the CMOS technology. For example, a P-type semiconductor region is formed on a P-type semiconductor substrate, and an N-type impurity region is formed in the P-type semiconductor region, thereby forming a photodiode (photodetector) having a PN junction. . Further, a first N-type impurity region (source region) and a second N-type impurity region (drain region) are formed in the P-type well region, and a gate electrode is formed therebetween. As a result, a switch element is formed. This switch element is provided between the output terminal of the photodiode and the input terminal of the charge-to-voltage conversion circuit, and opens and closes based on the voltage value applied to the gate electrode, and the charge voltage of the charge generated by the photodiode Controls the flow into the conversion circuit. Further, the N-type impurity region of the photodiode and the source region of the switch element may be common.

In a photodetector that captures a one-dimensional or two-dimensional optical image, a set of photodiodes and switch elements is arranged in M rows and N columns (M is an integer of 1 or more, N is an integer of 2 or more). N charge-voltage conversion circuits are provided, and N photodiodes in the m-th row have switch elements at the input terminals of the m-th charge-voltage conversion circuit (m is any integer from 1 to M). Connected through. In this photodetector, Each of the N switch elements is sequentially closed, and the charge generated by the photodiode corresponding to the closed switch element flows into the charge-voltage conversion circuit and is accumulated, and the amount of the accumulated charge is Is output from the charge-voltage conversion circuit. In this way, the intensity of light incident on each photodiode for each row is sequentially detected, and a one-dimensional or two-dimensional light image is captured.

Disclosure of the invention

As described above, in the photodetector configured by the CMOS technology, the charge generated by the photodiode in response to the incident light flows into the charge-to-voltage conversion circuit when the switch element closes, and the charge-to-voltage conversion occurs. The charge is stored by the circuit, and a voltage output corresponding to the amount of the stored charge is output from the charge-voltage conversion circuit.

On the other hand, as described above, even a switch element has a PN junction between a P-type well region and a drain region, so that charge is generated when light enters. Then, the charge generated by the switch element flows into the charge-voltage conversion circuit and is accumulated by the charge-voltage conversion circuit regardless of the open / closed state of the switch element. That is, not only the charge generated by the photodiode but also the charge generated by the switch element is accumulated by the charge-voltage conversion circuit.

Since the junction capacitance in the drain region of the switch element is smaller than the junction capacitance in the photodiode, the amount of charge generated in the switch element is smaller than the amount of charge generated in the photodiode, and the ratio between the two is smaller. It is constant. Therefore, in the normal case, the influence of the charge generated in the switch element is small.

However, in the case of a photodetector that captures a one-dimensional or two-dimensional light image, an increase in the number of arranged photodiodes (higher resolution) is required. As the photodetection area of each photodiode becomes smaller and the junction capacitance becomes smaller, the saturation charge becomes smaller. Also, with the increase in resolution, the number N of switch elements connected to the input terminal of each charge-voltage conversion circuit increases, and the total amount of charges generated in all N switch elements in each row increases. As a result, of the charges flowing into each charge-to-voltage conversion circuit, the total amount of charges generated in all of the N switch elements in each row is determined by the corresponding switch element among the N photodiodes in each row. Compared to the amount of electric charge generated by any one of the photodiodes that are closed, it becomes so large that it cannot be ignored. When the above phenomenon occurs, the value of the voltage output output from the charge-to-voltage conversion circuit is likely to be saturated, and the light image composed of pixels of M rows and N columns obtained by the photodetector is inaccurate. Becomes This phenomenon is called blooming phenomenon.

The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a light detection device and a light detection method capable of detecting an accurate incident light intensity while suppressing the influence of a blooming phenomenon. And

The photodetector according to the present invention comprises: (1) a photodetector that generates an amount of electric charge according to the intensity of incident light; and (2) a switch element that controls the output of the electric charge generated by the photodetector. (3) a charge-to-voltage conversion circuit that accumulates the electric charge generated by the photodetector and arrives via the switch element in the integration capacitance section, and outputs a voltage output corresponding to the amount of electric charge accumulated in the integration capacitance section; (4) control means for terminating the charge accumulation in the integration capacitance section before the time when the saturation charge is accumulated in the integration capacitance section of the charge-voltage conversion circuit when the charge generated in the photodetector is saturated. , Is provided.

According to this photodetector, the charge generated according to the intensity of the light incident on the photodetector reaches the charge-to-voltage conversion circuit via the switch element, and is accumulated in the integration capacitance section of the charge-to-voltage conversion circuit . A voltage output corresponding to the amount of charge stored in the integration capacitance section is output from the charge-voltage conversion circuit. The charge accumulation in the integration capacitance section is controlled by the control means, and if the charge generated in the photodetector is temporarily saturated, the charge before the time when the saturated charge is accumulated in the integration capacitance section of the charge-voltage conversion circuit is obtained. To end.

This time substantially corresponds to the time at which the amount of charge generated in the switch element starts to be accumulated in the integration capacitance unit. That is, from the time when the charge exceeding the saturation charge of the photodetector was accumulated in the integration capacitor, the charge was generated in each switch element. Although the charge starts to be accumulated in the integration capacitance section, which affects the output accuracy of the charge-voltage conversion circuit, according to the device of the present invention, the charge accumulation ends before this time. As described above, since the charge accumulation in the integration capacitance section is completed before the charge accumulation by the switch element is started, the influence of the blooming phenomenon is suppressed, and the accurate incident light intensity is detected.

The photodetector according to the present invention includes: (1) a saturated charge generating means for generating a saturated charge at a time when the switch element is closed; and (2) operating characteristics equivalent to those of the charge-voltage conversion circuit, A dummy charge-to-voltage converter that accumulates the generated charges and outputs a voltage output according to the amount of the accumulated charges; and (3) a voltage output value and a threshold value output from the dummy charge-to-voltage converter. And a comparison circuit that outputs a saturation signal indicating that the value of the voltage output reaches a threshold value when the voltage output value reaches a threshold value. The control means terminates the charge accumulation in the integration capacitance section of the charge-voltage conversion circuit based on the saturation signal output from the comparison circuit.

In this case, the saturated charge generated by the saturated charge generating means at the time when the switch element is closed is accumulated by the dummy charge-to-voltage conversion circuit, and a voltage output corresponding to the amount of the accumulated charge is output from the dummy charge-to-voltage conversion circuit. Is output. The value of the voltage output output from the dummy charge voltage conversion circuit and the threshold value are compared by the comparison circuit, and when the value of the voltage output reaches the threshold value, a saturation signal indicating that fact is output from the comparison circuit. Then, based on the saturation signal output from the comparison circuit, the control means terminates the charge accumulation in the integration capacitance section of the charge-voltage conversion circuit. Here, the dummy-to-charge-to-voltage conversion circuit has the same operating characteristics as the charge-to-voltage conversion circuit. Therefore, by terminating the charge accumulation in the integration capacitance section of the charge-voltage conversion circuit as described above, the effect of the blooming phenomenon is suppressed, and the accurate incident light intensity is detected. The photodetection method according to the present invention includes a photodetection element that generates and outputs an amount of charge corresponding to the intensity of incident light, and a scan that controls output of the charge generated by the photodetection element. A switch element, and a charge-to-voltage conversion circuit that accumulates the electric charge generated by the light detection element and arrives via the switch element in the integration capacitance section and outputs a voltage output according to the amount of electric charge accumulated in the integration capacitance section. A method for detecting the intensity of incident light using a photodetector provided with the photodetector.If the charge generated in the photodetector is temporarily saturated, the amount of the saturated charge is accumulated in the integration capacitance section of the charge-voltage conversion circuit. It is characterized in that the charge accumulation in the integration capacitance section is terminated before the time when the charge is made.

According to this photodetection method, in the photodetector, the charge generated according to the intensity of the light incident on the photodetector reaches the charge-voltage converter via the switch, and is integrated by the charge-voltage converter. It is stored in the capacity part. A voltage output corresponding to the amount of charge stored in the integration capacitance section is output from the charge-voltage conversion circuit. Then, the charge accumulation in the integration capacitance unit ends before the time when the saturation charge is accumulated in the integration capacitance unit of the charge-voltage conversion circuit when the charge generated in the photodetector is temporarily saturated. Therefore, similarly to the above, the charge accumulation is completed before the time corresponding to the charge from the switch element is accumulated in the integration capacitance portion, thereby suppressing the effect of the plumming phenomenon and reducing the accurate incident light intensity. Is detected.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a configuration diagram of a photodetector 1 according to the present embodiment.

2A and 2B are explanatory diagrams of the photodiode PD _mn and the switch element SW _mn of the photodetector 1 according to the present embodiment.

Figure 3 is a circuit diagram of a charge-voltage conversion circuit 1 1 O _m of the photodetector 1 according to the present embodiment.

FIG. 4 is a circuit diagram of the timing detection circuit 300 of the photodetector 1 according to the present embodiment.

FIGS. 5A, 5B, 5C, 5D, 5E, 5F, 5G, and 5H are timing charts for explaining the operation of the light detection device 1. FIG. 6 is a circuit diagram of another configuration example of the charge-voltage conversion circuit 1 1 o _m of the photodetector 1 according to the present embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description. FIG. 1 is a configuration diagram of a photodetector 1 according to the present embodiment. This photodetector 1 is composed of M (M is an integer of 1 or more) cuts 10 (^ to 丄 0 0 _M AZD conversion circuit 200, timing detection circuit 30) on one semiconductor substrate. 0 and a control circuit 400. Each input 100 _M (m is an integer of 1 or more and M or less) is N (N is an integer of 2 or more) photodiodes (photodetectors). and a PD _ML PD N number of switch elements SW ^ SW ^ charge-voltage conversion circuit 1 1 0 _M and Suitsuchi element 1 2 0 _M.

MX N photodiode PDUs PDMN are arrayed in M rows and N columns in the imaging area. The photodiode PD _mn is located at the m-th row and the n-th column, and generates an amount of electric charge according to the intensity of incident light. Switch element SW _MN is compatible with photodiode PD _MN, is provided between the input end of Fotodaiodo PD _MN and the charge-voltage conversion circuit 1 1 0 _m, generated in the photodiode PD _MN Controls the output of charges.

The input end of the charge-voltage conversion circuit 1 1 0 _M is connected to the N switch elements SW ^ SW ^ by A 1 line 1 9 0 _M. Charge-voltage converting circuit 1 1 0 _M is to accumulate the charges arriving via generated in the photo die Odo PD _MN Suitsuchi element SW _MN in the integral capacitance part, corresponding to the amount of charge accumulated in the integral capacitance part Outputs voltage output. Switch element 1 2 0 _M is provided between the input of the charge-voltage conversion circuit 1 1 0 _M output terminal and the A / D converter circuit 2 00. The switch elements 120 _M of each unit 100 _M are controlled by the control circuit 400 and closed sequentially, and the voltage output from the charge-voltage conversion circuit 110 _{m is} converted to the A / D conversion circuit 2. 0 Input to 0.

A / D conversion circuit 2 0 0, each Interview - Enter the Tsu preparative 1 0 0 _RA charge-voltage conversion circuit 1 1 0 _M voltage output sequentially arrive via the switch element 1 2 0 _RA from, the voltage output To A Performs ZD conversion and outputs digital output. The timing detection circuit 300 is a circuit for detecting the opening / closing timing of each switch element _SWmn . The control circuit 400 controls the opening and closing of the switch elements SW _mn based on the closing timing detected by the timing detection circuit 300, controls the charge storage operation in the charge-voltage converting circuit 11 O _m, each Suitsuchi element 12 and controlling the opening and closing of O _m, also, AZD conversion circuit 20

Controls the AZD conversion operation at 0.

2A and 2B are explanatory diagrams of the photodiode PD _ran and the switch element SW _mn of the photodetector 1 according to the present embodiment. FIG. 2A shows the photodiode PD _mn and the switch element SW _mn formed. FIG. 2B shows an equivalent circuit including a photodiode PD _mn and a switch element SW _mn , schematically showing a cross section of a P-type semiconductor substrate. As shown in FIG. 2 A, P-type Ueru region 90 l _mn on the surface of the P-type semiconductor substrate 900 is formed, the P-type Ueru region 90 :! On the other hand, an N + type impurity region 91 l _mn and an N + type impurity region 912 _mn are formed at a certain interval from each other, and _extend over a part of each of the N + type impurity region 91 l _ran and the N + type impurity region 912 _mn. Thus, a gate electrode 920 _mn is formed on the insulating film on the surface of the P-type semiconductor substrate 900. And PN junctions are formed between the P-type semi-conductor substrate 900 _mn of P-type Ueru region 90 l _mn and the N + -type impurity regions 91 l _mn, photodiode PD _mn is formed by the PN junction. The N + type impurity region (source region) 911 _ran , the N + type impurity region (drain region) 912 _mn and the gate electrode 920 _mn constitute a switch element SW _mn having an M〇S-FET structure. Further, 190 _m of A1 wiring (parasitic capacitance value Cv) is formed on the surface including a part of N + type impurity region _{912 mn} . The A1 wiring 190 _ra electrically connects the N + type impurity region 912 _{mn of} each of the N switch elements SW _{ml to} SW _mN in the m-th row and the input terminal of the charge-voltage conversion circuit 110 _m . In such a configuration, when light is incident on the N + -type impurity regions 91 l _ran surface, PN junction between the P-type Ueru region 901 _mn and the N + -type impurity regions 911 _mn of P-type semiconductor substrate 900 (in the photodiode PDJ Charge is generated and the charge _{Stored in} the PN junction capacitance Cd of the diode PD _mn . When a predetermined voltage is applied to the gate electrode 920 _mn , a conduction state is established between the N + -type impurity region (source region) 91 l _mn and the N + -type impurity region (drain region) _{921 mn} (ie, When the switch element SW _mn is closed), the charge stored in the PN junction capacitance Cd of the photodiode PD _mn is transferred from the N + type impurity region 91 _lmn to the N + type impurity region 912 _mn through the A1 wiring 190 It flows into _m, and reaches the input end of the charge-voltage conversion circuit 1 1 O _m. As can be seen from FIG. 2A, a PN junction is also formed between the P-type well region 901 _mn and the N + -type impurity region (drain region) 912 _mn of the P-type semiconductor substrate 900. A photodiode equivalent (hereinafter referred to as “photodiode PD _dmey ”) is configured. Accordingly, N + -type When light is incident on the impurity region 9 1 2 _mn, P-type PN junction between the P-type Uweru region 90 l _mn and the N + -type impurity region 9 12 _mn of the semiconductor substrate 900 (Fotodaiodo PD _dy ), A charge is generated. Then, all the charges generated by the photodiode PD _du in each of the N switch elements SW ^ SW ^ in the m-th row flow to the A1 wiring 19 O _m irrespective of the open / closed state of the switch element SW _mn. _Reaches the input terminal of the charge-voltage conversion circuit 11 Om.

FIG. 3 is a circuit diagram of the charge-voltage conversion circuit 11 _Ora of the photodetector 1 according to the present embodiment. Each charge-voltage converting circuit 1 1 o _m includes an amplifier 1 1 1, the capacitor (the integral capacitance part) 1 1 2 and switch element 1 1 3. The inverting input terminal of the amplifier 111 is connected to the N + -type impurity region (drain region) 91 2 _{mn of} each of the N switch elements SW ^ SW ^ in the m-th row via the A 1 line 19 O _m. It is connected. Further, a capacitive element 112 and a switch element 113 are provided in parallel between the inverting input terminal and the output terminal of the amplifier 111. The reference voltage Vref is supplied to the non-inverting input terminal of the amplifier 111. The charge-voltage conversion circuit 1 1 O _ra, when the switch element 1 1 3 closes, the capacitor element 1 12 is discharged, the voltage output is outputted from the output is initialized. Hand, the charge-voltage conversion circuit 1 1 O _m, when Suitsuchi element 1 13 is open, the input The charge that has flowed into the terminal is stored in the capacitor 112, and a voltage output corresponding to the amount of the stored charge is output from the output terminal.

At time t when the time t has elapsed from the time when the switch element 1 13 of the charge-voltage conversion circuit 1 1 O _m is opened, the N switch elements SW _{ml to} SW „ _i in the m-th row ₍ in the n-th column). When only certain switch element SW _mn is closed, the amount Q of electric charge accumulated in the capacitor element 1 1 2 of the load voltage conversion circuit 1 1 O _m conductive at time t is expressed by the following formula .

Q = Q _mn + I d- t ... h)

The value V of voltage output that is output from the output terminal of the charge-voltage conversion circuit 1 1 o _m at time t is expressed by the following equation.

V = Q / Cf

_{= (Q m + Id- t)} / C 112 - (2)

Here, Q _mn indicates the amount of charge flowing from the photodiode PD „corresponding to the closed switch element SW _mn among the N photodiodes PD _{ml to} PD _rt in the m-th row. shows the total amount of the first 111 rows of] ^ number of switch element 3 _"1-3 respectively generated per unit time in Oke Ru photodiode PD _DUMY charge (or current). Further, C ₁₁₂ is the capacitance element This is the capacitance value of 1 1 2.

FIG. 4 is a circuit diagram of the timing detection circuit 300 of the photodetector 1 according to the present embodiment. The timing detection circuit 300 includes a charge-voltage conversion circuit 310, a capacitance element 320, a comparison circuit 330, and a D latch circuit 340.

Charge-voltage converting circuit 310 of the timing detection circuit 300 has been made in view of the charge-voltage conversion circuit 1 1 O _ra equivalent operating characteristics of each Yunitto 10 O _m, amplifier 1 1 1 and the amplifier 31 1 of the same, etc., the capacity It has a capacitive element 312 equivalent to the element 112 and a switch element 313 equivalent to the switch element 113. The inverting input terminal of the amplifier 311 is connected to the capacitive element 320 via the A1 wiring 390. A capacitor 312 and a switch element are connected between the inverting input terminal and the output terminal of the amplifier 311. 3 1 3 are provided in parallel. The reference voltage Vref is supplied to the non-inverting input terminal of the amplifier 311. In the charge-voltage conversion circuit 310, when the switch element 313 is closed, the capacitance element 312 is discharged, and the voltage output output from the output terminal is initialized. On the other hand, when the switch element 313 is open, the charge-to-voltage conversion circuit 310 accumulates the electric charge flowing into the input terminal into the capacitive element 312, and generates a voltage corresponding to the amount of the accumulated electric charge. Output from the output terminal.

One terminal of the capacitive element 320 is connected to the input terminal of the charge-voltage conversion circuit 31 via the A1 wiring 390, and the other terminal is connected to the control circuit 400. . When the value of the voltage applied to the capacitive element 320 from the control circuit 400 decreases by ΔV, AV′C ₃₂ is input to the input terminal of the charge-voltage conversion circuit ₃₁₀ . Only charge flows in. Where C ₃₂ . Is the capacitance value of the capacitor 320. The charge amount AV′C ₃₂₀ is made equal to the saturation charge amount in each photodiode PD _mn . Further, the parasitic capacitance of the A 1 line 3 9 0 timing detection circuit 3 0 0 is equal to the parasitic capacitance value Cv of the A 1 line 1 9 O _m of each Yunitto 1 0 O _ra. The amount of charge accumulated in the capacitance element 312 of the charge-voltage conversion circuit 310 is represented by the parasitic capacitance value Cv of the A1 wiring 390 and the capacitance value C32 of the capacitance element ₃₂₀ . , And increases according to the time constant determined by the band of the amplifier ₃₂₀ , and eventually reaches the saturated charge amount AV- _{C32 ()} . That is, the capacitive element 320 acts as a saturated charge generating means for generating a saturated charge when the voltage value applied from the control circuit 400 decreases by Δν.

The comparison circuit 330 inputs the voltage output output from the charge-voltage conversion circuit 310 to the inverting input terminal, and inputs the threshold voltage Vth to the non-inverting input terminal. Then, the comparison circuit 330 outputs a logical output of a logical value H when the voltage output value is smaller than the threshold voltage Vth, and outputs a logical output of a logical value L when the voltage output value is larger than the threshold voltage Vth. The threshold voltage Vth is the saturation charge AV.C _{32 in} the capacitor 312. Is set to a value that is somewhat smaller than the value of the voltage output output from the output terminal of the charge-voltage conversion circuit 310 when the charge of the charge is accumulated. Therefore, the capacitance element of the charge-voltage conversion circuit 310 The logic output (saturation signal) output from the output terminal of the comparison circuit 330 changes from the logical value H to the logical value L at a time slightly earlier than the time at which the charge accumulation in 312 is saturated.

The D latch circuit 340 inputs the logical output (saturation signal) output from the comparison circuit 330 to the C1r terminal, and determines the voltage value applied to the capacitive element 320 from the control circuit 400. C 1 Input to the k terminal and supply voltage Vdd to the D terminal. If the logical value input to the C Ir terminal is L, the D latch circuit 340 outputs a logical value L from the Q terminal. On the other hand, if the logical value input to the CI r terminal is H, the D latch circuit 340 latches the logical value input to the D terminal at the timing when the voltage value input to the C 1 k terminal falls. Output from Q terminal.

Therefore, the voltage value applied to the capacitive element 320 from the control circuit 400 becomes Δ

Before the time when the voltage drops by V, the logical value L is output from the Q terminal of the D latch circuit 340, and the voltage applied to the capacitive element 320 from the control circuit 400 is ΔV only. At the time of the drop, the logical output input to the C 1 r terminal from the comparison circuit 330 is the logical value H, and after this time, the logical value H is output from the Q terminal of the D latch circuit 340. You. Thereafter, when the logic output input to the C1r terminal from the comparison circuit 330 changes to a logic value L, the logic value L is output from the Q terminal of the D latch circuit 340 after this time.

The logical output output from the Q terminal of the D latch circuit 340 of the timing detection circuit 300 configured as described above indicates the opening / closing timing of each switch element SW _mn . The control circuit 400 changes the voltage value applied to the capacitive element 320 of the timing detection circuit 300 at a predetermined timing, and outputs the voltage from the Q terminal of the D latch circuit 340 of the timing detection circuit 300. Input logical output. Then, the control circuitry 4 0 0 controls the opening and closing of the switch elements SW _mn based on a logical output which is output from the timing detection circuit 3 0 0, the charge storage operation in the charge-voltage conversion circuit 1 1 0 _m To control the opening and closing of each switch element 120 _m , and the AZD conversion operation in the AZD conversion circuit 200. Next, the operation of the light detection device 1 according to the present embodiment will be described, and the light detection method according to the present embodiment will be described. The following operation is performed based on the control by the control circuit 400. M units 10 (^ to 丄 00 _M operate in parallel at the same timing. In each unit 100 _ra , N switch elements SW _{ml to} SW _mN are closed in order, and N units In each of the photodiodes PD ^ PD ^, the charges generated due to the incidence of light are sequentially input to the charge-voltage conversion circuit 11 1 o _m via the A 1 wiring 190 _ra .

5A, 5B, 5C, 5D, 5E, 5F, 5G, and 5H are timing charts for explaining the operation of the photodetector 1 according to the present embodiment. is there. In this figure, a case will be described in which a charge generated by light incidence in the photodiode PD _mn located in the m-th row and the eleventh column is input to the charge-voltage conversion circuit _11ora .

At time tO, closes switch element 1 1 3 of the charge-voltage conversion circuit 1 10 "(FIG. 5A), the capacitive element 1 1 2 is discharged, the value of the voltage output that is output from the charge-voltage conversion circuit 1 10 _m The reset level is reached (Fig. 5H) .The switch element 313 of the charge-voltage conversion circuit 310 is closed (Fig. 5B), and the capacitance element 312 is discharged.

The voltage output value output from 0 becomes the reset level (Fig. 5D). At this time, the N switch elements SW ^ SW ^ are open (Fig. 5G). Further, a predetermined voltage value is supplied from the control circuit 400 to the capacitive element 320 of the timing detection circuit 300 (FIG. 5C). Then, the logical output output from the comparison circuit 330 becomes a logical value H (FIG. 5E), and the logical output output from the Q terminal of the D latch circuit 340 is a logical value L) (FIG. 5F).

At time tl, the switch element 113 of the charge-voltage conversion circuit 110 is opened (FIG. 5A), and the charge can be accumulated in the capacitance element 112 of the charge-voltage conversion circuit 110 _m .

In addition, the switch element 313 of the charge-voltage conversion circuit 310 is opened (FIG. 5B), and the charge is stored in the capacitance element 312 of the charge-voltage conversion circuit 310. At time t2, only one Suitsuchi elements SW _ran of the N Suitsuchi element SW _ml to SW _mN is closed (FIG. 5G). Further, the voltage value supplied from the control circuit 400 to the capacitive element 320 of the timing detection circuit 300 decreases by AV (FIG. 5C). As a result, the logical output output from the Q terminal of the D latch circuit 340 changes to the logical value H (FIG. 5F). Also, the saturation charge ΔV · _C32 . Flows into the input terminal of the charge-voltage conversion circuit 310 and is accumulated in the capacitive element 312. The amount of charge accumulated in the capacitor 312 increases according to the time constant, and eventually reaches the saturated charge amount ΔV * C ₃₂ . And Therefore, the voltage output output from the output terminal of the charge-voltage conversion circuit 310 also gradually increases, and eventually reaches a saturation value (FIG. 5D).

At time t3, when the value of the voltage output output from the output terminal of the charge-voltage conversion circuit 310 reaches the threshold voltage Vth (FIG. 5D), the logic output output from the comparison circuit 330 changes to a logic value L (FIG. 5). E), the logical output output from the Q terminal of the D latch circuit 340 also changes to the logical value L (FIG. 5F). Then, sure that you this logical output is turned to a logical value L, is controlled by the identification and control circuit 400 opens switch element SW _ran (5 G), the capacitive element 1 12 of the charge-voltage conversion circuit 1 1 O _m The accumulation of the charge ends.

In the present embodiment, each of the charge-voltage conversion circuit 110 _m and the charge-voltage conversion circuit 310 have the same operating characteristics as each other, and the parasitic capacitance value of each of the A1 wiring 190 _m and the A1 wiring 390 Are the same as each other. Therefore, charges generated in the photodiode PD _mn is be saturated charge amount, the charge storage prior to time accumulated saturation charge in the capacitor 1 1 2 of the charge-voltage conversion circuit 1 1 O _m is completed . At this time, the charge accumulation in the capacitive element 112 of the integration capacitance section is controlled by the control means, and if the charge generated in the photodiode PD _mn is temporarily saturated, the saturated charge is integrated by the charge-voltage conversion circuit. It roughly corresponds to the time stored in the capacity unit. That is, this time substantially corresponds to the time when the amount of charge generated in the switch element _SWmn starts to be accumulated in the capacitance element 112 of the integration capacitance section. In other words, around the time when the charge exceeding the saturation charge of the photodiode PD is accumulated in the capacitor 1 1 2 Good to, charges generated in each switch element SW _mn begins to be accumulated in the capacitor 1 1 2, is given effect in the output accuracy of the charge-voltage conversion circuit 1 1 O _m, according to the present device, this time The charge accumulation ends before. As described above, since the charge accumulation in the capacitive elements 112 ends before the charge accumulation by the switch element _SWmn starts, the influence of the blooming phenomenon is suppressed, and the accurate incident light intensity is detected. Is done.

As a result, the influence of the plumming phenomenon is suppressed, and an accurate incident light intensity is detected. Note that the charge-voltage conversion circuit 1 1 O period the switch element 1 1 3 open the _m (Tokii U tl later), N number of switch elements of the m rows SW ^ SW ^ photodiode PD that put each All of the charges generated by _{du y} (the second term on the right side of the above equation (1)) also take into account the force S accumulated in the capacitor 1 1 2 of the charge-voltage conversion circuit 1 1 O _{m and} the total amount of this charge. The threshold voltage Vth is set appropriately.

Further, in this embodiment, since the M units 10 (^ to 丄 00 _M and the timing detection circuit 300 are provided on one semiconductor substrate, each charge-voltage conversion circuit 11 O _m and if the charge-voltage converting circuit 3 1 0 each design and the same thing, manufacturing process is stabilized even if no, the charge-voltage conversion circuit 1 1 o _m and charge voltage conversion circuitry 3 1 0, respectively The operating characteristics are also the same.

The present invention is not limited to the above embodiment, and various modifications are possible. For example, without providing the timing detection circuit ₃₀₀ , a control signal for controlling the opening / closing timing of the switch element _SWmn may be externally provided to the photodetector 1. In this case, the switch element sw _mn is closed only during the period in which the effect of the blooming phenomenon is suppressed when the light with high intensity is incident on the photodetector 1.

The charge-voltage conversion circuit 1 1 O _m may be configured as shown in FIG. The charge voltage shown in FIG conversion circuit 1 1 0 _ra comprises an amplifier 1 1 1, capacitor element 1 1 2 il 1 2 ₄ and switch element 1 1 3 1 1 3 _4. Amplifier 1 1 between the first inverting input terminal and the output terminal, the capacitive element 1 1 2 serially connected capacitance element 1 1 2 ₂ mutually And switch element 1 1 3 _2, capacitor element 1 1 2 ₃ and sweep rate Tutsi element 1 1 3 ₃ connected in series with each other, the capacitive element 1 1 2 ₄ and switch element 1 1 3 ₄ connected in series with each other, as well as switch Elements 113 i are provided in parallel. The capacitance value of the integral capacitance part of the charge-voltage conversion circuit 1 1 0 _m is determined according to the switch device 1 1 3 _2-1 1 3 ₄ closed state of their respective. By doing so, the capacitance value of the integration capacitance section can be appropriately set according to the incident light intensity.

Industrial applicability

INDUSTRIAL APPLICABILITY The present invention can be used for an apparatus and a method for detecting the intensity of incident light.

Claims

Claim aspects

1. A photodetector that generates an amount of electric charge according to the intensity of incident light, and a switch element that controls the output of the electric charge generated by the photodetector,

A charge-to-voltage conversion circuit that accumulates charge generated by the light detection element and arrives via the switch element in the integration capacitance unit, and outputs a voltage output according to the amount of charge accumulated in the integration capacitance unit;

A control for ending the charge accumulation in the integration capacitance section before the time when the charge generated in the photodetector is temporarily saturated and before the saturation charge is accumulated in the integration capacitance section of the charge-voltage conversion circuit. Means,

A light detection device comprising:

2. Saturated charge generation means for generating the saturated charge at a time when the switch element closes;

A dummy circuit that has an operating characteristic equivalent to that of the charge-to-voltage conversion circuit, stores the charge generated by the saturation charge storage unit, and outputs a voltage output corresponding to the amount of the stored charge. A charge-voltage conversion circuit,

A comparison circuit that compares a value of a voltage output output from the dummy charge-voltage converter with a threshold value, and outputs a saturation signal indicating that when the value of the voltage output reaches the threshold value;

Further comprising

The light detection device according to claim 1, wherein the control unit terminates charge accumulation in the integration capacitance unit of the charge-voltage conversion circuit based on a saturation signal output from the comparison circuit. apparatus.

3. A photodetector that generates and outputs an amount of electric charge according to the intensity of the incident light, a switch element that controls the output of the electric charge generated by the photodetector, and the switch that is generated by the photodetector. The charge arriving through the element is stored in the integrating capacitance A charge-to-voltage conversion circuit that outputs a voltage output according to the amount of charge accumulated in the integration capacitance unit.A method for detecting the intensity of incident light, comprising: In the case where the charge generated in step (a) is temporarily saturated, the charge accumulation in the integration capacitance unit is terminated before the time when the saturation charge amount is accumulated in the integration capacitance unit of the charge-voltage conversion circuit. Light detection method.