JPH0566129A - Distance measuring semiconductor integrated circuit - Google Patents

Abstract

PURPOSE:To provide an IC for measuring distance enabling cost reduction and high performance of a distance measuring device. CONSTITUTION:A distance measuring semiconductor integrated circuit 40 for auto-focusing device having a light receiving element 30 which receives the light from a target 20 subjected to distance measurement and outputs a signal according to the distance to the target has following elements formed in one chip: a distance measuring arithmetic part 41 for forming a digital distance measurement data inversely proportional to the distance to the target 20 from the signal of the light receiving element 30, a memory part 42 for writing two distance measurement data outputted from the distance measuring arithmetic part 41 for two known distances at the time of calibration mode, and a data arithmetic part 43 for operating an auto-focusing device control signal from the two measured distance data stored in the memory part 42 and the distance measurement data outputted from the distance measuring arithmetic part 41 at the time of distance measuring mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring semiconductor integrated circuit which is a main component of a distance measuring device mounted on an active type or passive type autofocus device.

[0002]

2. Description of the Related Art A distance measuring device mounted on an autofocus device, when the distance measuring device is an active type, has an infrared light emitting diode 110 for irradiating a subject whose distance is to be measured with light, as shown in FIG. , Subject 120
The PSD (position sensitive detector) element 130 that receives the light reflected by the light and outputs a current according to the incident angle of the light, and the distance to the subject after A / D conversion of the current applied from the PSD element 130 A distance measurement integrated circuit (distance measurement IC) 140 that calculates data (distance measurement data) corresponding to the above, and a CPU (central processing unit) 150 that controls the distance measurement IC 140 are normally included.

In such a distance measuring device, the optical system is physically fine-tuned in order to compensate for the measurement error due to the manufacturing variation of the distance measuring IC and the deviation of the optical system (light receiving element, light emitting element, etc.). Is done.

However, it is very difficult to completely compensate for such a measurement error by adjusting the optical system, so that the error is electrically eliminated. That is, the distance measuring IC is provided with a few terminals for externally connecting the adjustment variable resistors R1 and R2, and by adjusting the resistance values of the plurality of adjustment resistors R1 and R2 at the initial stage, A Correct the current at the / D converter,
The error in the distance measurement data is deleted.

This compensating method using the adjusting resistor is described as follows.
The current is shifted in parallel by changing the resistance value of 1, and the slope of the current is changed by changing the resistance value of the resistor R2. That is, as shown in FIG. 6, first, distance measurement is performed at the first distance, which is the rotation center of the data,
The resistance value of the resistor R1 is changed so that the output data has a desired value. Next, distance measurement is performed at a second distance different from the first distance, and the resistance R2 is set so that the output data has a desired value.
Change the resistance value of. However, this method requires a great deal of effort because it is necessary to repeat the distance measurement many times and adjust the resistance value until the output data becomes the desired data.

As a method of erasing the error of the distance measurement data without using the adjusting resistor, as shown in FIG. 7, an independent memory 260 is externally attached to the normal distance measuring IC 240 and the distance measuring IC 240 is used. The applicant knows a compensation method in which a linear function obtained by measuring a known distance is stored in this memory 260.

[0007]

However, according to this method, an external memory itself and a circuit for generating each timing at the time of adjustment are required, and wiring between each element is newly required, and moreover, a CPU is required. The burden on the software will increase significantly.

Therefore, an object of the present invention is to provide a distance measuring IC which can reduce the cost and improve the performance of the distance measuring device.

[0009]

According to the present invention, the above-mentioned object is an autofocus device having a light receiving element for receiving light from an object to be measured and outputting a signal according to the distance to the object. It is achieved by a semiconductor integrated circuit for distance measurement having the following configuration.

In this distance measuring semiconductor integrated circuit, the following elements are formed in one chip. That is, a distance measurement calculation unit that forms digital distance measurement data that is inversely proportional to the distance from the signal from the light receiving element to the object, and two distance measurement calculation units that output two known distances in the calibration mode. The storage unit to which the distance data is written, and the storage unit 2 stored in the storage unit in the distance measurement mode
The data calculation unit calculates an autofocus device control signal from one distance measurement data and the distance measurement data output from the distance measurement calculation unit.

Preferably, control logic means capable of selectively switching between the calibration mode and the distance measuring mode according to a control input from the outside is further formed in one chip.

The storage unit is preferably an EEPROM. It is also preferable that the EEPROM is CMOS and the semiconductor integrated circuit is formed by a Bi-CMOS process.

The semiconductor integrated circuit may be for an active type autofocus device.

[0014]

Function: Calibration of a distance measuring device in which a known true distance is actually measured by a distance measuring device to obtain distance measuring data, and the relationship between the distance measuring data and the true distance is stored in a storage unit. Is performed only by issuing a calibration command from the CPU. Therefore, the load on the software of the CPU of the distance measuring device can be greatly reduced, the configuration can be made extremely simple, and the cost and performance of the distance measuring device can be reduced.

[0015]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 schematically shows the configuration of an active type distance measuring device mounted on a compact camera or the like as an embodiment of the present invention.

In the figure, 10 is an infrared light emitting diode for irradiating the object 20 whose distance is to be measured with light, and 30 is a PSD for receiving the light reflected by the object 20 and outputting a current according to the incident angle of the light. A (position-sensitive detector) element, 40 is an integrated circuit for distance measurement (distance measurement IC) for A / D converting the current output from the PSD element 30 and calculating data (distance measurement data) corresponding to the distance to the subject. ) And 50 each represent a CPU (central processing unit) for controlling the entire distance measuring device.

FIG. 1 schematically shows the internal structure of the distance measuring IC 40.

The distance measuring IC 40 has an A / D
A distance measurement calculation unit 41 including a converter, an EEPROM (electrically erasable programmable ROM) 42 whose input is connected to the output of the distance measurement calculation unit 41, an output of the distance measurement calculation unit 41, and an output of the EEPROM 42. Connected data calculation unit 43, distance measurement calculation unit 41, EEP
It is provided with a ROM 42 and a control logic 44 which is connected to the data operation section 43 and controls these operations. The input of the distance measurement calculation unit 41 is connected to the output of the PSD element 30, the control logic 44 is connected to the CPU 50 and the light emitting diode 10, and the output of the data calculation unit 43 is connected to the CPU 50. Distance measuring IC 40 and CP
The signal line connecting the U50 is two control lines from the CPU 50 to the distance measuring IC 40 and the distance measuring IC 40.
These are three lines of data lines for sending the data obtained in step 1 to the CPU 50.

The EEPROM 42 is formed of CMOS, and the other components are formed of bipolar. That is, the distance measuring IC 40 is a one-chip IC formed by the Bi-CMOS process.

Next, the operation of this distance measuring device will be described with reference to the flow chart of the control program of the CPU 50 shown in FIG.

There are two modes of operation of the distance measuring device. One is a calibration mode and the other is a distance measurement mode.

The calibration mode is an initial setting mode which is carried out before the distance measuring device is shipped from the factory and when the adjustment becomes necessary thereafter. Step S in FIG.
When it is determined that the calibration mode is set in step 1, the operations of steps S2 to S7 are executed. First, the CPU 50 controls the control logic 4 of the distance measuring IC 40.
Then, a control signal is sent to the EEPROM 4, and the EEPROM 42 is set to the write mode (step S2). Then, another control signal is sent to the control logic 44 to start the distance measuring operation for initialization (step S
3). As a result, the light emitting diode 10 is driven, and the light reflected from the subject (distance-measuring object) 20 installed at a predetermined and known first distance is applied to the PSD element 30. .. The PSD element 30 outputs a signal current of two channels according to the first distance, and the signal current is input to the distance measurement calculation unit 41. The distance measurement calculation unit 41 amplifies each of these currents and inputs a logarithmically compressed voltage using a diode to each input terminal pair of the differential circuit to obtain an output current proportional to the reciprocal of the distance to the subject. Then, the output current is A / D converted to generate digital distance measurement data a. Next, the distance measurement data a is changed to E by the control of the control logic 44.
It is written to a predetermined address of the EPROM 42 (step S4).

The same operations as in steps S3 and S4 are performed on the subject 20 placed at a position that is separated by a predetermined known second distance (step S5).
The distance measurement data b is written in a predetermined address of the EEPROM 42 (step S6). As described above, the CPU 50 is notified that the calibration operation is completed (step S7).

The distance measurement mode is a mode in which the original distance measurement for autofocus is performed. If it is determined in step S1 that this distance measuring mode is set, step S
The operations of 8 to S11 are executed. First, the CPU 50 sends a control signal to the control logic 44,
The distance measuring operation is started (step S8). This allows
The light emitting diode 10 is driven, and the light reflected from the subject 20 at the position to be measured is applied to the PSD element 30. The PSD element 30 outputs a signal current of two channels according to the distance, which is input to the distance measurement calculation unit 41. The distance measurement calculation unit 41 amplifies each of these currents and inputs a logarithmically compressed voltage using a diode to each input terminal pair of the differential circuit to obtain an output current proportional to the reciprocal of the distance to the subject. Then, the output current is A / D converted to generate digital distance measurement data x (step S9).

In the next step S10, the EEPROM 4
The autofocus device control signal K is calculated in the data calculation unit 43 from the distance measurement data a and b stored in 2 and the distance measurement data x. The control signal for the autofocus device is a signal indicating at which position the lens should be stopped, and is a division zone formed by dividing the distance from zero to infinity by a predetermined number (11 in the example described later). expressed.

The first distance in the calibration mode is the boundary point between the nth zone and the (n + 1) th zone, the distance measurement data at this time is stored in the EEPROM 42 as a, and the second distance is the mth distance. Zone and No. (m +
1) It is a boundary point with the zone and the distance measurement data at this time is b
Is stored in the EEPROM 42 and the actual distance measurement data in the distance measurement mode is x, the control signal K for the autofocus device in the data calculation unit 43.
Is calculated based on the following linear function.

K = INT [n + (x−a) / {(b−a) / (m−n)}] The circuit configuration of the data calculation unit 43 that performs such a calculation is known.

The autofocus device control signal K calculated by the data calculation unit 43 is output in the next step S11.
Is transferred to the CPU 50 at.

FIG. 4 is a graph showing the relationship between the distance to the subject and the distance measurement data and the divided zones, and shows two examples in which the distance from zero to infinity is 11 divided zones.

As one example (line A), the first distance in the calibration mode is the boundary point between the first zone and the second zone, and the distance measurement data at this time is a = 18.
No. 4 is stored in the EEPROM 42, the second distance is the boundary point between the 10th zone and the 11th zone, and the distance measurement data at this time is b = 1012, and the EEPROM 4
2 and the actual distance measurement data in the distance measurement mode is x, the calculation of the autofocus device control signal K in the data calculation unit 43 is performed based on the following linear function.

K = INT [1+ (x-184) / {(1
012-184) / (10-1)}] = INT {1 + 9 (x-184) / 828} As a result, as shown in FIG. 4, K becomes the sixth zone.

The case where the distance measuring device is mounted on another autofocus device is the other example (line B). The first distance in the calibration mode is the boundary point between the first zone and the second zone, and the distance measurement data at this time is stored in the EEPROM 42 as a = 180, and the second distance is the tenth zone and the second zone. It is a boundary point with the 11th zone, and the distance measurement data at this time is EE with b = 530
If the actual distance measurement data stored in the PROM 42 in the distance measurement mode is x, the data calculation unit 43
The calculation of the control signal K for the autofocus device in
It is performed based on the following linear function.

K = INT [1+ (x-180) / {(5
30-180) / (10-1)}] = INT {1 + 9 (x-180) / 390} As a result, as shown in FIG. 4, K becomes the sixth zone as in the previous case. That is, the autofocus device control signal K generated by this distance measuring device has the same correct value regardless of which autofocus device is equipped.

In this way, the known true distance (in the above example, the boundary between the zones) is actually measured by the distance measuring device to obtain the distance measurement data, and the distance measurement data and the true distance are obtained. The distance measuring device is calibrated such that the relationship of (4) is stored in the EEPROM 42 only by issuing a calibration command from the CPU 50 side. Therefore, the load on the software of the CPU of the distance measuring device can be greatly reduced, the configuration can be made extremely simple, and the cost and performance of the distance measuring device can be reduced.

Although the above-mentioned embodiments describe the active type distance measuring device, the present invention may be, for example, a passive type distance measuring device utilizing a spatial phase difference. Further, although the one-chip IC formed by the Bi-CMOS process is used as the distance measuring IC, the distance measuring IC of the present invention may be a one-chip IC formed by another process. Furthermore, EEPR
Instead of the OM, another EPROM (erasable programmable ROM) such as a fuse type may be used.

[0037]

As described in detail above, according to the present invention, a distance measuring semiconductor integrated circuit has the following elements formed in one chip. That is, a distance measurement calculation unit that forms digital distance measurement data that is inversely proportional to the distance from the signal from the light receiving element to the object, and two distance measurement calculation units that output two known distances in the calibration mode. A storage unit into which the distance data is written, and a data calculation unit that calculates an autofocus device control signal from the two distance measurement data stored in the storage unit in the distance measurement mode and the distance measurement data output from the distance measurement calculation unit. Is. Therefore, the cost and performance of the distance measuring device can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic electrical configuration of a distance measuring IC according to an embodiment of the present invention.

FIG. 2 is a diagram schematically showing an overall configuration of a distance measuring device in the embodiment of FIG.

FIG. 3 is a flow chart of a control program of a CPU in the embodiment of FIG.

4 is a graph showing a relationship between a distance to a subject, distance measurement data, and divided zones in order to explain an operation principle of the distance measuring IC of FIG.

FIG. 5 is a diagram schematically showing a configuration of a conventional distance measuring device.

FIG. 6 is a graph showing a relationship between a distance to a subject and distance measurement data for explaining the conventional apparatus of FIG.

FIG. 7 is a diagram schematically showing a configuration of a conventional distance measuring device.

[Explanation of symbols]

 10 infrared light emitting diode 20 subject 30 PSD element 40 integrated circuit for distance measurement 41 distance measurement calculation unit 42 EEPROM 43 data calculation unit 44 control logic 50 CPU

Claims (5)

[Claims] 1. A distance measuring semiconductor integrated circuit for an autofocus device, comprising a light receiving element for receiving light from an object to be measured and outputting a signal according to a distance to the object. Distance measurement calculation means for forming digital distance measurement data inversely proportional to the distance from the signal from the object to the object, and two distance measurement calculation means output for the two known distances in the calibration mode. A control signal for the autofocus device is generated from the storage means in which the distance data is written, the two distance measurement data stored in the storage means in the distance measurement mode, and the distance measurement data output from the distance measurement calculation means. A semiconductor integrated circuit for distance measurement, characterized in that data calculating means for calculating is formed in one chip. 2. A control logic means capable of selectively switching between the calibration mode and the distance measurement mode according to a control input from the outside is further formed in one chip. Item 1. A semiconductor integrated circuit for distance measurement according to item 1. 3. The semiconductor integrated circuit for distance measurement according to claim 1, wherein the storage means is an EEPROM. 4. The semiconductor integrated circuit for distance measurement according to claim 1, wherein the EEPROM is a CMOS, and the semiconductor integrated circuit is formed by a Bi-CMOS process. 5. One of the known distances in the calibration mode is a boundary point between the nth zone and the (n + 1) th zone of the autofocus device control signal, and a is stored in the storage means. Distance measurement data of m, the other distance known in the calibration mode is the m-th zone and the (m +) th zone of the autofocus device control signal.
1) If it is a boundary point with the zone, b is the distance measurement data at this time stored in the storage means, and x is the actual distance measurement data in the distance measurement mode, then the data calculation means uses K = The semiconductor integrated device for distance measurement according to claim 1, wherein INT [n + (x−a) / {(b−a) / (m−n)}] is calculated. circuit.