Skip to main content

Camera Intrinsic Parameters

This document provides comprehensive information about camera intrinsic parameters, including how to obtain them, their formats, and applications.

Q1: Availability and Identification​

Intrinsic Parameter Availability​

Starting from 2023, all SENSING cameras come with pre-calibrated intrinsic parameters stored in the camera. For cameras produced before 2023, intrinsic parameters were only calibrated upon specific customer request.

Identifying Camera Manufacturing Year​

You can identify the manufacturing year of the camera through the SN code:

The image below shows a camera with:

  • SN Code: H190S-E01220525
  • Product Model: SG3-ISX031C-GMSL2-H190S
SN Code Example
PrefixManufacturing YearIntrinsic Parameters Status
Dxxxxxx2021Not calibrated by default
Exxxxxx2022Not calibrated by default
Fxxxxxx2023Calibrated by default
Gxxxxxx2024Calibrated by default
Hxxxxxx2025Calibrated by default

Q2: Accessing Camera Intrinsic Parameters​

Method 1: Following Model-Specific Instructions​

Below are examples of models and their corresponding instruction documents for obtaining intrinsic parameters:

#Model ExamplesInstruction DocumentNotes
1SG2-AR0233C-5200-G2A-Hxxx
SG2-IMX390C-5200-GMSL2-Hxxx
SG5-IMX490C-5300-GMSL2-Hxxx
SG8-AR0820C-5300-GMSL2-Hxxx
SG8-OX08BC-5300-GMSL2-Hxxx		Intrinsic Parameter Reading Instructions for GW5200 & GW5300 ISP ModelsModels with 5200 or 5300 in the model name
2SG2-AR0231C-0202-GMSL-HxxxIntrinsic Parameter Reading Instructions for AP0101 & AP0202 ISP ModelsModels with 0101 or 0202 in the model name
3SG3S-ISX031-GMSL2F-HxxxISX031(IMX623) GMSL2 Module Intrinsic Parameter Reading InstructionsModels with ISX031 or IMX623 in the model name
4SG2-AR0233C-GMSL2 (raw camera)
SG8-IMX728C-G2G-Hxxx (raw)
SG3S-OX03JC-G2F-Hxxx
S56 binocular		Intrinsic Parameter Reading Instructions for GMSL2 and FPDLINK III Series Modules without ISPModels with GMSL2 or FPDLINK in the name but without an ISP model number
5SG1-OX01FC-GMSL-HxxxIntrinsic Parameter Reading Instructions for OX01F10 SENSOR ModelsModels with OX01FC in the model name

Data Format References

Method 2: Using SensingTech Online Service Platform​

You can download intrinsic parameters individually through the SensingTech Customer Self-service Information Query Platform. Note that the SN code of the camera is required.

Q3: Camera Model Types​

Two types of camera models are used for intrinsic parameters:

  1. Pinhole Model: Used for lenses with fields of view up to 120 degrees (including H120)
  2. Fisheye Model: Used for lenses with fields of view up to 190 degrees

Pinhole Camera Model​

The pinhole camera model with distortion correction can be represented by:

[x']   [x(1 + k₁r² + k₂r⁴ + k₃r⁶)/(1 + k₄r² + k₅r⁴ + k₆r⁶) + 2p₁xy + p₂(r² + 2x²)]
[y'] = [y(1 + k₁r² + k₂r⁴ + k₃r⁶)/(1 + k₄r² + k₅r⁴ + k₆r⁶) + p₁(r² + 2y²) + 2p₂xy]

Where:

  • (x, y) are the normalized image coordinates
  • (x', y') are the distorted image coordinates
  • r² = x² + y² is the squared radius
  • k₁, k₂, k₃, k₄, k₅, k₆ are the radial distortion coefficients
  • p₁, p₂ are the tangential distortion coefficients

By default, parameters K1-K6 are used for distortion correction.

Fisheye Camera Model​

The fisheye camera model can be represented by:

r(θ) = k₁θ + k₂θ³ + k₃θ⁵ + k₄θ⁷

Where:

  • θ is the angle between the incoming light ray and the optical axis
  • r is the distance from the optical center on the image plane
  • k₁, k₂, k₃, k₄ are the fisheye distortion coefficients

This model is specifically designed for wide-angle lenses with fields of view exceeding 120 degrees.

Q4: Reading Intrinsic Parameters on Third-Party Platforms​

If your camera has calibrated intrinsic parameters, you can access them through the following methods:

Using I2C Tools​

You can use the platform's I2C tools to read intrinsic parameters according to the provided instructions.

I2C Reading Process:

  1. Identify the correct I2C bus and device address for your camera (typically 0x51 for EEPROM)
  2. Use I2C commands to read specific register addresses containing intrinsic parameters
  3. For Linux systems:
    • Use i2cdetect -r -y <bus_number> to scan for available devices
    • Use i2ctransfer -y -f <bus_number> w2@<device_address> <reg_high> <reg_low> r<count> to read data

Important Note: When multiple modules are connected to a domain controller simultaneously, the default I2C addresses must be remapped to unique addresses to ensure reading from the correct module.

Using Platform-Provided Interfaces​

Some platforms may have already implemented interfaces based on our documentation. Please consult with your platform provider for specific usage methods.

Q5: Parameter Conversion and Usage​

Converting Intrinsic Parameters​

Example of Intrinsic Parameter Storage:

The following table shows an example of how the focal length parameter (fx) is stored in registers:

RegisterValueDescriptionType and UnitFlag
0x00650x59
0x00660xAD
0x00670xFE
0x00680xD61426.1570701402value：fx
type: double
unit: pixels		YES_CRC32_4
0x00690xA0
0x006A0x48
0x006B0x96
0x006C0x40

These register values can be converted to the actual focal length parameter (fx = 1426.1570701402 pixels) using the string conversion formula described below.

String Conversion Formula:

#include "stdio.h"

int main(void)
{
    unsigned char pMem[] = {0x59, 0xad, 0xfe, 0xd6, 0xa0, 0x48, 0x96, 0x40};
    double *p = (double*)pMem;
    printf("%.10f\r\n", *p);

    return 0;
}

Converting Floating Point Values​

For focal length conversion:

AddressParameterHex ValueDecoded Value / DescriptionStatus
0x00210xECYES_CRC32_4
0x0022Focal Length0x514.26 Focal LengthYES_CRC32_4
0x00230x88YES_CRC32_4
0x00240x40YES_CRC32_4

Use the following code for conversion:

unsigned char ppm[] = { 0xEC, 0x51, 0x88, 0x40 };
float* m = (float*)ppm;
printf("%f\r\n", *m);

Reading and Converting SN Codes​

The SN code is stored as part of the OTP data in the module, following the same format as intrinsic parameters.

SN Code Conversion Process:

  1. Read the hexadecimal values from the SN code registers (addresses 0x0120-0x0133)
  2. Convert each hexadecimal value to its ASCII character representation
  3. Combine the characters to form the complete SN code
  4. Stop at the first 0xFF value, which indicates the end of the SN string

SN Code Conversion Example:

RegisterAddressValueRef No.Notes
SN0x01200x48H60S-D11200036Model code contains 32 bytes; unused positions are filled with 0xFF
0x01210x36
0x01220x30
0x01230x53
0x01240x2D
0x01250x44
0x01260x31
0x01270x31
0x01280x32
0x01290x30
0x012A0x30
0x012B0x30
0x012C0x33
0x012D0x36
0x012E0xFF
0x012F0xFF
0x01300xFF
0x01310xFF
0x01320xFF
0x01330xFF
0x01340xFF
0x01350xFF
0x01360xFF
0x01370xFF
0x01380xFF
0x01390xFF
0x013A0xFF
0x013B0xFF
0x013C0xFF
0x013D0xFF
0x013E0xFF
0x013F0xFF
0x01400xFF

SN String Conversion Code:

#include <stdio.h>

int main() {
    unsigned char pMem[] = {0x48, 0x36, 0x30, 0x53, 0x2d, 0x44, 0x31, 0x31, 0x32, 0x30, 0x30, 0x33, 0x36};

    int arrayLength = sizeof(pMem) / sizeof(pMem[0]);

    char result[arrayLength + 1];

    for (int i = 0; i < arrayLength; i++) {
        result[i] = pMem[i];
    }
    result[arrayLength] = '\0';

    printf("SN: %s\n", result);

    return 0;
}

Using Intrinsic Parameters​

Intrinsic parameters can be used with OpenCV. Implementation code must be developed by the customer.

Reference article: OpenCV Camera Intrinsic Calibration and Usage"

Q6: Working with Multiple Cameras​

Reading Parameters from Multiple Cameras​

For Camera with GW5200/GW5300 ISP

  1. For a single camera connection:

    • In a Linux environment, scan the EEPROM I2C address (0x51) using i2cdetect -r -y
    • Read the register values using: sudo i2ctransfer -y -f 1 w2@0x51 0x00 0x01 r1

  2. For multiple cameras of the same model:

    • Remap the EEPROM address 0x51 (0xA2) to different addresses by modifying registers 0x42 and 0x43 of 9295/96717F
    • Write the original address 0x51 (0xA2) to register 0x43
    • Write the destination addresses (e.g., 0x54/0xA8, 0x55/0xAA) to register 0x42 as defined in the device tree file

Address Remapping Process:

  1. Original Setup: All cameras initially have the same I2C address (0x51)
  2. Configuration: Write to registers 0x42 and 0x43 of MAX9295/MAX96717F
  3. Result: Each camera now has a unique address (e.g., 0x54, 0x55, etc.)
  4. Reading: Use the new unique addresses to read data from each camera individually

For Camera with ISX031 sensor

Follow the same method as above:

  • Write the original address 0x34 (0x1A) to register 0x43
  • Write destination addresses (e.g., 0x54/0xA8, 0x55/0xAA) to register 0x42 as defined in the device tree file

Q7: Technical Specifications​

Parameter Storage Addresses​

Pinhole and fisheye model parameters are stored at different addresses:

  • Pinhole mode: Addresses 0x85-0xC4 store K1, K2, P1, P2, K3, K4, K5, K6 parameters (FOV < 120°)
  • Fisheye mode: Addresses 0xC5-0xE4 store K1, K2, K3, K4 parameters (FOV > 120°)

Storage Addresses Table:

Parameter TypeModel TypeAddress RangeParameters
Intrinsic MatrixBoth0x45-0x54Fx, Fy, Cx, Cy
DistortionPinhole0x85-0xC4K1, K2, P1, P2, K3, K4, K5, K6
DistortionFisheye0xC5-0xE4K1, K2, K3, K4
SN CodeBoth0x0120-0x0133ASCII characters

Calibration Precision​

  • RMS Differences: RMS calculation formulas may vary between different batches of cameras
  • Calibration Error Range:
    • COD precision error: AA lenses have standards, threaded lenses do not
    • Equivalent focal length error: Controlled according to lens design tolerance
    • Reprojection error (RMS): Average reprojection error is 0.25

Calibration Standards and Accuracy Assessment​

The evaluation standards include:

  • Reprojection error
  • Stability of intrinsic parameters and distortion parameters
  • Calibration accuracy at different viewing angles
  • Distortion correction effects
  • Testing in actual applications