Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
1999-11-18
2002-01-01
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C327S514000
Reexamination Certificate
active
06335523
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor dark image position sensitive device, more particularly to a semiconductor dark image position sensitive device for sensing an image position of dark point image such as dark target point (dark image position) existing in a bright background, and especially to a semiconductor dark image position sensitive device which is applied to a non-contact optical positioning sensor in a variety of automated systems or a variety of optical measuring devices, so that it is suitable for realizing a sensing system or a measuring system which can sense easily a dark image position in a bright background at high-speed.
2. Description of the Related Art
Heretofore, a semiconductor image position sensitive device has been known as a sensor for sensing easily at high speed an image position of spot (bright point) such as bright target point existing in a dark background.
In general, a semiconductor image position sensitive device is composed of a photoelectric layer, a dividing resistive element layer laminated on the photoelectric layer, and signal current output terminals connected to the dividing resistive element layer. Such semiconductor image position sensitive device is constituted on the basis of such a basic principle that when light irradiated from a spot is input to the photoelectric layer, a photoelectric current is generated in the photoelectric layer, the photoelectric current thus generated in the photoelectric layer is allowed to flow into the dividing resistive element layer, whereby the photoelectric current distributed in response to a resistance value between an inflow portion of the photoelectric current in the dividing resistive element layer and the signal current output terminals is settled, and a center-of-gravitational position of incident light into the photoelectric layer is calculated based on a value of photoelectric current.
A conventional semiconductor image position sensitive device constituted on the basis of the above described basic principle will be explained in detail herein by referring to the accompanying drawings.
Namely,
FIG. 1
is a conceptual view showing the structure of a conventional semiconductor image position sensitive device, and
FIG. 2
is a conceptual diagram of an equivalent circuit exhibiting a principle of the calculation for sensing an image position in the semiconductor image position sensitive device of
FIG. 1
wherein the semiconductor image position sensitive device comprises a P-type semiconductor layer P, an insulator layer I laminated on the bottom side of the P-type semiconductor layer P, an N-type semiconductor layer N laminated on the bottom side of the insulator layer P, a resistive element layer R
P
for calculating an image position and which is laminated on the surface side of the P-type semiconductor layer P, a signal current output terminal A as well as a signal current output terminal B formed on the opposite ends of the resistive element layer R
P
on the surface side thereof, and a bias terminal C formed on the bottom side of the N-type semiconductor layer N at the central portion thereof.
In the above described semiconductor position sensitive device S, a photoelectric layer S is formed from the P-type semiconductor layer P, the insulator layer I, and the N-type semiconductor layer N, while the dividing resistive element layer is formed from the resistive element layer R
P
.
In such semiconductor image position sensitive device as described above, when light L is irradiated from the surface side of the resistive element layer R
P
, photoelectric current generated in the photoelectric current layer S at an incident position of the light L flows into the resistive element layer R
P
, the photoelectric current thus flowed into the resistive element layer R
P
is distributed in response to a resistance value defined between a position at which the photoelectric current flowed into the resistive element layer R
P
and the signal current output terminals A and B, whereby output signal currents I
A
and I
B
are output from the signal current output terminals A and B, respectively (see FIG.
2
). It is to be noted that reference character I
C
designates a bias current output to the bias terminal C.
In this case, when it is supposed that resistivity of the resistive element layer R
P
is constant, the resistance value is proportional to a distance defined between the position at which photoelectric current is flowed into the resistive element layer R
P
and the signal current output terminals A and B, so that information X at an incident position of the light L (being equivalent to a ratio of dislocation from the central position of the resistive element layer R
P
) is determined by an equation (1):
x
=(
I
A
−I
B
)/(
I
A
+I
B
) (1)
In the meantime, it is constituted in such that the photoelectric current layer S is continuous, and the resistive element layer R
P
being a dividing resistance for calculating an image position is formed as a thin film superposed on the photoelectric layer S in the semiconductor image position sensitive device shown in
FIGS. 1 and 2
.
However, it is not so easy that the resistive element layer R
P
being a dividing resistance for calculating an image position is formed stably as a uniform thin film having a predetermined resistivity, and as a result, such resistivity cannot be made constant, whereby a distribution of the resistivity becomes scattered, so that there is a problem that the scattering becomes a factor of an error in sensing for image position.
In order to solve such problem as described above, devised is a semiconductor image position sensitive device of separate photoelectric device type wherein a photoelectric layer is fabricated as a separate photoelectric layer of a dividing structure separated into plural sections being independent of a dividing resistive element layer, while the dividing resistive element layer is fabricated stably as a constriction resistance at a position away from the separate photoelectric layer, and photoelectric currents generated in the separate photoelectric layer having a structure which has been separated and divided individually into sections are allowed to flow condensedly into positions corresponding to the dividing resistive element layers.
FIG. 3
is a conceptual diagram of an equivalent circuit exhibiting a principle of such semiconductor image position sensitive device of a separate photoelectric device type as described above.
In
FIG. 3
, reference character Sg designates a separate photoelectric layer in the semiconductor image position sensitive device of separate photoelectric device type. According to the semiconductor image position sensitive device of separate photoelectric device type as described above, a resistive element layer R
P
can be stably fabricated as a dividing resistance for calculating an image position, whereby errors in sensing an image position is allowed to decrease, so that it is possible to improve stability in sensing an image position.
Furthermore, a photoelectric current generated by irradiating the light L in any structure in any semiconductor image position sensitive device as described above shown in
FIGS. 1 through 3
is output from the signal current output terminal A as an output signal electric current I
A
, while it is output from the signal current output terminal B as an output signal current I
B
(see FIGS.
2
and
3
). Accordingly, when a calculation is made on the basis of the equation (1) by applying the output signal currents I
A
and I
B
, it becomes possible to calculate a position of spot image by means of an analog arithmetic circuit at extremely high-speed.
Meanwhile, any of the above described semiconductor image position sensitive device is the one for sensing an image position of a spot (bright point) existing in a dark background, and it could not sense a position of dark point image existing in a bright background.
In other words, a gravitational positi
Fujita Toyomi
Idesawa Masanori
Yano Yasushige
Allen Stephone B.
Riken
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